Re: Centerboard pivot

FWIW, I'm machined a nice bushing to go in the centerboard out of
UHMW. Hole size was .760, 10 thou bigger than the .75" 303 stainless
rod donated to the cause. OD of the bushing matched the hole size cut
by one of the hole cutters that go on the hand drill. About 1.5"

Cut notches in the outside of of the bushing, on both sides, to keep
it from any possible turning. Mallet fit in the centerboard, epoxy
putty in the notches, and two layers of 4oz clother over it.

Pivot bearing plates are 3.5" square, 1/8" thick square plates, with
a 3/8" long piece of 1.25" round stock welded on, then a .755 hole
bored in both. Mounted with generous use of epoxy putty, and 8 screws
each.

Pivot pin is the .75 303 SS round, drilled and taped on the lathe to
accept 1/4-16 SS bolts and fender washers to keep the pin in place.

Fit of the board is loose enough so all the sailing forces will be
transfered to the case.

Incidentaly, the CB case for the CLC doesn't have the top cross beam,
so all the forces will need to be carried by the 2x bracing around
the keel and under the floorboards. Case is glassed inside and out,
with that in mind.

Rudder post will be 1-1/2" SCH 10 304-304L PIPE
Outer Diameter = 1.9000"
Inner Diameter = 1.6820"
Wall Thickness = 0.1090"

I can get a four foot section for about $37 from online metals.

--- In bolger@y..., "Chuck Leinweber" <chuck@d...> wrote:
> Richard:
>
> I like the UHMW idea. You may remember that I used it for parrels
on my
> Caprice. Also for hatch glides. You can get extruded bushing
stock from
> McMaster-carr with 1-1/4" ID and various OD's.
>
> Chuck
>
> >
> >
> > Ah, that would make sense.
> >
> > Googling shows quite a few references to "uhmw bushings aluminum
> > shaft"... Even a couple of marine ones.
> >
> > For the low load, slow speed application of rudder, centerboard,
and
> > tabernacle pivot, think I could get away with 1 1/8" aluminum
> > shafting and uhmw poly bushings?
> >
> > I suspect the bushings and shafts would last quite a few years of
> > normal trailer sailing use. I'd be sure to design the setup so
it's
> > easy to dissassemble for inspections and/or replacements.
> >
> >
> > --- In bolger@y..., kwilson800@a... wrote:
> > > Why doesn't aluminum make a good bearing? The reason bare
aluminum
> > > doesn't "rust" in normal use is that it forms a very thin
coating
> > of
> > > aluminum oxide on the surface which inhibits further
corrosion. In
> > a
> > > bearing application, this coating is continuously worn off and
> > > renewed. Well, guess what, the aluminuum oxide left inside the
> > > beaing is quite an effective abrasive. You could probably
hardcoat
> > > anodize it, or "hardlube", which is hardcoat anodizing
impregnated
> > > with teflon. There are also several proprietary processes to
make
> > > aluminum into a decent bearing surface, "Nituff" is one of the
> > better-
> > > known ones, but by the time you've gone through all that
trouble,
> > why
> > > not just use bronze or stainless steel in the first place?
> > >
> > > Keith Wilson
> > >
> > > --- In bolger@y..., richard@s... wrote:
> > > > UHMW poly has a pretty low melting point. Wonder if I could
cast
> > > > parts out of it?
> > > >
> > > > Also, why doesn't it work well with aluminum?
> >
> >
> > Bolger rules!!!
> > - no cursing, flaming, trolling, spamming, or flogging dead horses
> > - pls take "personals" off-list, stay on topic, and punctuate
> > - add your comments at the TOP and SIGN your posts, snip all you
like
> > - To order plans: Mr. Philip C. Bolger, P.O. Box 1209,
> > Gloucester, MA, 01930, Fax: (978) 282-1349
> > - Unsubscribe: bolger-unsubscribe@y...
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
> >

Writing the previous message inspired me to finish updating Paul Zander's
article on the design and construction of centerboards and rudders. The
corrected and expanded article can be found here:

http://www.boat-links.com/foils.html

On Wed, 22 Aug 2001 21:37:05 -0700, I wrote:
> Pat-
>
> I don't have any plots of foils, but I've got a couple of articles about
> how to plot your own:
> ...

--
John <jkohnen@...>
http://www.boat-links.com/
The problem with people who have no vices is that generally you can be
pretty sure they're going to have some pretty annoying virtues.
<Elizabeth Taylor>

Pat-

I don't have any plots of foils, but I've got a couple of articles about
how to plot your own:

http:///www.boat-links.com/foils.txt

http:///www.boat-links.com/foilfaq.html

I'm in the process of editing and reformating the article by Paul Zander,
there's an error in one of the formulae now. Apparently the right stuff is
in this under construction version:

http://www.boat-links.com/foils-1.html

I think you could get a pretty good shape by shaping the leading edge out
of a sizable chunk of solid wood, and the trailing edge likewise, then
using thin ply over the center spar for the main part of the shape. The
leading edge could be close enough to half-round that you could machine it
to shape, and the trailing edge could have straight sections so you could
make it on a table saw. Rabbets could be worked into the edges for the
plywood. You've come up with an interesting idea.

On Tue, 21 Aug 2001 19:11:29 -0000, Pat wrote:
> ...
> I would love to see a couple of plots of of
> the airfoils. You can send them to pateson@...
> ...

--
John <jkohnen@...>
http://www.boat-links.com/
Why should we take advice on sex from the Pope?
If he knows anything about it, he shouldn't. <G. B. Shaw>

I don't think there is a sharp distiction between a simple wing and
and sophisticated end plate. "Wing" suggests a high aspect ratio and
an foil section. "End plate" suggests a low aspect ratio and a flat
plate. Wings also merge into "bulbs" if they are, well, bulbous.

PHV

--- In bolger@y..., "Clyde S. Wisner" <clydewis@c...> wrote:
> I wanted to ask the difference between "wing keel" and end plates
on the cb/keel and rudder. Clyde
>
> pvanderw@o... wrote:
>
> > I am the owner and sailor of a wing keel sloop. I have a slightly
> > different perspective. I see very few wing keels on all-out racing
> > boats. They have a lot of bulbs, but few wings.
> >
> > The place where the wing keels have a big market is in cruiser-
> > racers, specifically the shoal draft versions of boats available
with
> > deep (6 ft +) keels. The wing keel versions will have ALMOST the
same
> > performance. PHRF ratings usually give the wing keel a 3 sec/mi
> > difference in handicap. Certainly the difference is insignificant
in
> > any non-racing context. For most people, saving a foot or so in
draft
> > is much more important. Of course, they are risking getting a
lobster
> > pot warp or anchor rode really, really, really tangled around the
> > keel.
> >
> > The wing works as an end plate, preventing flow from the high
> > pressure side to the low pressure side. This is done by the lee
side
> > wing. The weather side wing does not provide a hydrodynamic
benefit.
> > So dragging the extra wing around causes the slight performance
> > penalty.
> >
> > As for the bad effects of racing rules, here is my opinion. By in
> > large, racing sailors create and administrate the rules, and they
get
> > what they (the majority) want. The boats are too expensive, too
> > complicated, need too much crew, etc. in my opinion and in the
> > opinion of many others. But, the really bad thing is that non-
racers
> > use the racing boats as a model, rather than going out on their
own.
> > If the racers don't want unstayed, rotating wing masts, so be it.
But
> > cruisers should have the gumption to get them if they want them.
But
> > they don't.
> >
> > Peter
> >
> > Bolger rules!!!
> > - no cursing, flaming, trolling, spamming, or flogging dead horses
> > - pls take "personals" off-list, stay on topic, and punctuate
> > - add your comments at the TOP and SIGN your posts, snip all you
like
> > - To order plans: Mr. Philip C. Bolger, P.O. Box 1209,
Gloucester, MA, 01930, Fax: (978) 282-1349
> > - Unsubscribe: bolger-unsubscribe@y...
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/

I wanted to ask the difference between "wing keel" and end plates on the cb/keel and rudder. Clyde

pvanderw@...wrote:

> I am the owner and sailor of a wing keel sloop. I have a slightly
> different perspective. I see very few wing keels on all-out racing
> boats. They have a lot of bulbs, but few wings.
>
> The place where the wing keels have a big market is in cruiser-
> racers, specifically the shoal draft versions of boats available with
> deep (6 ft +) keels. The wing keel versions will have ALMOST the same
> performance. PHRF ratings usually give the wing keel a 3 sec/mi
> difference in handicap. Certainly the difference is insignificant in
> any non-racing context. For most people, saving a foot or so in draft
> is much more important. Of course, they are risking getting a lobster
> pot warp or anchor rode really, really, really tangled around the
> keel.
>
> The wing works as an end plate, preventing flow from the high
> pressure side to the low pressure side. This is done by the lee side
> wing. The weather side wing does not provide a hydrodynamic benefit.
> So dragging the extra wing around causes the slight performance
> penalty.
>
> As for the bad effects of racing rules, here is my opinion. By in
> large, racing sailors create and administrate the rules, and they get
> what they (the majority) want. The boats are too expensive, too
> complicated, need too much crew, etc. in my opinion and in the
> opinion of many others. But, the really bad thing is that non-racers
> use the racing boats as a model, rather than going out on their own.
> If the racers don't want unstayed, rotating wing masts, so be it. But
> cruisers should have the gumption to get them if they want them. But
> they don't.
>
> Peter
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - pls take "personals" off-list, stay on topic, and punctuate
> - add your comments at the TOP and SIGN your posts, snip all you like
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/

Just like to liven up the conversation with ideas.
"Hollow foil winged keel" for an Elegant Punt?
Did it 19 years ago. (Not with wing on bottom) ;-)
That's one hanging on the side of my Elegant Punt "Toad"
My Son didn't know he was sailing such a "Controversial Design".
Made a good "Streamlined shape, if not perfect NACA Airfoil.
Easy enough to do, and it is very strong.
Just thought someone might like to try the idea.

Pat Patteson
Molalla, Oregon

--- In bolger@y..., wmrpage@a... wrote:
> In a message dated 8/21/01 11:18:37 AM Central Daylight Time,
> pateson@c... writes:
>
>
> > Any criticism? It sounds good to me.
> >
> >
>
> Hi, Pat:
>
> You've really brought the fluid-flow people out of the
woodworks,
> haven't you?! I think you should just go ahead and do it,
photograph the
> process and post photos & commentary on the Bolger2 site. You would
be a
> public benefactor. I'm inclined to think that shaping a solid board
would be
> easier, but perhaps your scheme would be more warp & swelling
resistant and
> worth the extra bother, if any. Go for it! Win, lose or draw, it'll
be an
> education for you certainly, and for the rest of us if you will
share.
>
> Bill in MN
>
>
> [Non-text portions of this message have been removed]

In a message dated 8/21/01 11:18:37 AM Central Daylight Time,
pateson@...writes:

> Any criticism? It sounds good to me.
>
>

Hi, Pat:

You've really brought the fluid-flow people out of the woodworks,
haven't you?! I think you should just go ahead and do it, photograph the
process and post photos & commentary on the Bolger2 site. You would be a
public benefactor. I'm inclined to think that shaping a solid board would be
easier, but perhaps your scheme would be more warp & swelling resistant and
worth the extra bother, if any. Go for it! Win, lose or draw, it'll be an
education for you certainly, and for the rest of us if you will share.

Bill in MN


[Non-text portions of this message have been removed]

> Don't manufacturers tend to push homogeneity? Tooling and

engineering costs and all that.

The tendency of cruisers to copy racers goes way back before
manufactured boats, as mentioned by Bolger in more than one place.
Anyway, if this was a factor, it would work in the other direction
because 90% of sailboats are never raced.

In fairness, there are cruising boats out there with little racing
influence: Freedom, Island Packet, all the boats built especially for
Caribbean charter, etc.

Peter

<snip>

> the really bad thing is that non-racers
> use the racing boats as a model, rather than going out on their own.
> If the racers don't want unstayed, rotating wing masts, so be it. But
> cruisers should have the gumption to get them if they want them. But
> they don't.
>
> Peter
>

Don't manufacturers tend to push homogeneity? Tooling and engineering costs
and all that.

Chuck

-This is the way to go. What you are talking about is essentially a
large control-line model airplane wing. Why not build it that way. You
will probably want a little more material on the trailing edge anyway
and the leading edge would be very simple as a solid member
Bob Chamberland



I could make a set of real ribs in half an hour. Glue the paper to
the

> plywood, cut a little outside the line and then use a disc sander or
> something that works perpendicularly to sand down to the line. You
> could probably make ribs out of regular wood if you wanted to. They
> don't have to be built up out of little pieces as weight isn't
> critical here. I don't know how close close enough is. No one

studies

> this, but wind tunnel models are often off by 1/64" and work fine.

You

> don't want local waviness, but a little roughness will only hurt a
> little.
>
> If you just want to know what the foil looks like:
> Nice picture of NACA 009:
>http://amber.aae.uiuc.edu/~m-selig/ads/afplots/n0009sm.gif
>
> The NACA 009 is probably appropriate, tho possibly you could find

one

> slightly better. You could easily get one thicker, if you wanted.

NACA

> 012 would work. Not sure whether NACA 015 starts to get too thick.
>
> If you want me to plot it, you need to tell me the skin thickness

and

> the chord length (i.e. width of board), plus your snail mail. I'm

not

> sure you could get plywood more than 1/8" thick to take the bend but
> you could use 2 layers. the leading edge will have to be shaped out

of

> a chunk of wood.
>
> program to plot (my unzip software couldn't deal with it, but it
> worked on my old computer). I don't think it does skin thickness:
>http://rampages.onramp.net/%7emicheleb/hanger.html
>
> > with plywood and glass, so it would be "Simple" to build.
> > I know it can be done by using foam or real ribs, but
> > I think "Pretty Close" if probably good enough here.
> >
> > > >

I am the owner and sailor of a wing keel sloop. I have a slightly
different perspective. I see very few wing keels on all-out racing
boats. They have a lot of bulbs, but few wings.

The place where the wing keels have a big market is in cruiser-
racers, specifically the shoal draft versions of boats available with
deep (6 ft +) keels. The wing keel versions will have ALMOST the same
performance. PHRF ratings usually give the wing keel a 3 sec/mi
difference in handicap. Certainly the difference is insignificant in
any non-racing context. For most people, saving a foot or so in draft
is much more important. Of course, they are risking getting a lobster
pot warp or anchor rode really, really, really tangled around the
keel.

The wing works as an end plate, preventing flow from the high
pressure side to the low pressure side. This is done by the lee side
wing. The weather side wing does not provide a hydrodynamic benefit.
So dragging the extra wing around causes the slight performance
penalty.

As for the bad effects of racing rules, here is my opinion. By in
large, racing sailors create and administrate the rules, and they get
what they (the majority) want. The boats are too expensive, too
complicated, need too much crew, etc. in my opinion and in the
opinion of many others. But, the really bad thing is that non-racers
use the racing boats as a model, rather than going out on their own.
If the racers don't want unstayed, rotating wing masts, so be it. But
cruisers should have the gumption to get them if they want them. But
they don't.

Peter

Warning: rant follows, but real info follows rant.

Wing keels are popular because hydrodynamically they act like they are
longer than they really are (and interact with the racing rules well),
plus it's a place to stash the lead that's nice and low. Don't take
anything that's done on a racing boat seriously until you know how
much of it is to increase performance and how much is to beat the
rules. THere are a lot of rules. If there are no rules everyone would
probably race wing masted multihulls. Remember that America's cup race
with no rules where one boat was enormous and the other one was a
multihull? I had a professor in college (Jerry Milgram) who came up
with a way to "beat" the rules with a different rig. Even though it
was not particularly extremem or unmanageable, they changed the rules
so it wasn't worth his while. I kind of doubt that he still races, but
that way all the other people who beat the rules in the conventional
way didn't have to change their boats, though Jerry had played
honestly and was now SOL. Look up "Cascade" if you're curious. THe
reason almost all bicycles are uprights and devote 80% of the rider's
effort to beating air drag is the racing rules: recumbents were
banned. THis kind of thing goes on and on. All those people think they
are driving SUV's because they are cool, but it's really because SUV's
don't raise the car companies CAFE (fleet mileage for cars but not
"light trucks"). Read Bolger on rules, it's sad and funny.

I'm not as extreme as he is, but I recognize the distortion.

I could make a set of real ribs in half an hour. Glue the paper to the
plywood, cut a little outside the line and then use a disc sander or
something that works perpendicularly to sand down to the line. You
could probably make ribs out of regular wood if you wanted to. They
don't have to be built up out of little pieces as weight isn't
critical here. I don't know how close close enough is. No one studies
this, but wind tunnel models are often off by 1/64" and work fine. You
don't want local waviness, but a little roughness will only hurt a
little.

If you just want to know what the foil looks like:
Nice picture of NACA 009:
http://amber.aae.uiuc.edu/~m-selig/ads/afplots/n0009sm.gif

The NACA 009 is probably appropriate, tho possibly you could find one
slightly better. You could easily get one thicker, if you wanted. NACA
012 would work. Not sure whether NACA 015 starts to get too thick.

If you want me to plot it, you need to tell me the skin thickness and
the chord length (i.e. width of board), plus your snail mail. I'm not
sure you could get plywood more than 1/8" thick to take the bend but
you could use 2 layers. the leading edge will have to be shaped out of
a chunk of wood.

program to plot (my unzip software couldn't deal with it, but it
worked on my old computer). I don't think it does skin thickness:
http://rampages.onramp.net/%7emicheleb/hanger.html

I wonder if anyone has done work on flow fences on outboard rudders
and leeboards to keep them from ventilating?

--- In bolger@y..., pateson@c... wrote:
> Why then, are Wing Keels so popular?
> As I said, "Just a thought"
> OK, forget the "Wing Keel" for my "Toad" Darn
>
> I still think the "Foil" shape with a single spar
> would work OK. Might not be a perfect NACA Airfoil,
> I would think you could get fairly close. Ribs might
> be good, or just appropriatly sized spacers.
> How "Close" does it need to be?
> I would love to see a couple of plots of of
> the airfoils. You can send them to pateson@c...
> I'm also looking for "Simple" here. We're already working
> with plywood and glass, so it would be "Simple" to build.
> I know it can be done by using foam or real ribs, but
> I think "Pretty Close" if probably good enough here.
>
> "THis is only going to improve the performance of your
> boat a little bit, mind you."
>
> Thanks for the input.
> I've come up with a lot of really "Bad Ideas",
> but this one doesn't seem that "Bad".
>
> Pat Patteson
> Molalla, Oregon
>
>
> --- In bolger@y..., "Lincoln Ross" <lincolnr@m...> wrote:
> > I'm afraid the ballast idea doesn't work:
> > 1. You won't get much righting moment. As the boat tilts, the
force
> > will tilt with it. Will not act "down" but down and to windward,
> thru
> > center of boat. In a real keel, the weight acts vertically, thru a
> > line to windward of the center of the boat. I forget the
> terminology,
> > tho I knew it well at one point. The America's cup boat that had a
> > wing keel also had plenty of lead.
> >
> > 2. If you did come up with a hydrodynamic ballast substitute (say
> an
> > offset hydrofoil or by adding a control to tilt the "wing"), what
> > happens when the sail fills while the boat isn't moving? It's ok
to
> > have a little leeway in that situation, but it's not ok to flip.
> >
> > IF you designed it just right, the "wing" could reduce drag some,
> and
> > maybe make the board act as if it was longer. But it's a lot
easier
> to
> > add a few inches to the board if you can afford the draft.
> > --- In bolger@y..., pateson@c... wrote:
> > snip
> > >
> > > Just a thought. If it were used as a daggerboard, it
> > > could have a "Wing" on the bottom of it.
> > > Would not be removable, but pretty cool underwater dynamics.
> > > Enough of the proper foil shape down there, and you wouldn't
> > > need balast. It would just suck the boat down.
> > >
> > > Pat Patteson
> > > Molalla, Oregon
> > >
> > >

Why then, are Wing Keels so popular?
As I said, "Just a thought"
OK, forget the "Wing Keel" for my "Toad" Darn

I still think the "Foil" shape with a single spar
would work OK. Might not be a perfect NACA Airfoil,
I would think you could get fairly close. Ribs might
be good, or just appropriatly sized spacers.
How "Close" does it need to be?
I would love to see a couple of plots of of
the airfoils. You can send them topateson@...
I'm also looking for "Simple" here. We're already working
with plywood and glass, so it would be "Simple" to build.
I know it can be done by using foam or real ribs, but
I think "Pretty Close" if probably good enough here.

"THis is only going to improve the performance of your
boat a little bit, mind you."

Thanks for the input.
I've come up with a lot of really "Bad Ideas",
but this one doesn't seem that "Bad".

Pat Patteson
Molalla, Oregon

--- In bolger@y..., "Lincoln Ross" <lincolnr@m...> wrote:
> I'm afraid the ballast idea doesn't work:
> 1. You won't get much righting moment. As the boat tilts, the force
> will tilt with it. Will not act "down" but down and to windward,
thru
> center of boat. In a real keel, the weight acts vertically, thru a
> line to windward of the center of the boat. I forget the
terminology,
> tho I knew it well at one point. The America's cup boat that had a
> wing keel also had plenty of lead.
>
> 2. If you did come up with a hydrodynamic ballast substitute (say
an
> offset hydrofoil or by adding a control to tilt the "wing"), what
> happens when the sail fills while the boat isn't moving? It's ok to
> have a little leeway in that situation, but it's not ok to flip.
>
> IF you designed it just right, the "wing" could reduce drag some,
and
> maybe make the board act as if it was longer. But it's a lot easier
to
> add a few inches to the board if you can afford the draft.
> --- In bolger@y..., pateson@c... wrote:
> snip
> >
> > Just a thought. If it were used as a daggerboard, it
> > could have a "Wing" on the bottom of it.
> > Would not be removable, but pretty cool underwater dynamics.
> > Enough of the proper foil shape down there, and you wouldn't
> > need balast. It would just suck the boat down.
> >
> > Pat Patteson
> > Molalla, Oregon
> >
> >

I'm afraid the ballast idea doesn't work:
1. You won't get much righting moment. As the boat tilts, the force
will tilt with it. Will not act "down" but down and to windward, thru
center of boat. In a real keel, the weight acts vertically, thru a
line to windward of the center of the boat. I forget the terminology,
tho I knew it well at one point. The America's cup boat that had a
wing keel also had plenty of lead.

2. If you did come up with a hydrodynamic ballast substitute (say an
offset hydrofoil or by adding a control to tilt the "wing"), what
happens when the sail fills while the boat isn't moving? It's ok to
have a little leeway in that situation, but it's not ok to flip.

IF you designed it just right, the "wing" could reduce drag some, and
maybe make the board act as if it was longer. But it's a lot easier to
add a few inches to the board if you can afford the draft.

--- In bolger@y..., pateson@c... wrote:
snip
>
> Just a thought. If it were used as a daggerboard, it
> could have a "Wing" on the bottom of it.
> Would not be removable, but pretty cool underwater dynamics.
> Enough of the proper foil shape down there, and you wouldn't
> need balast. It would just suck the boat down.
>
> Pat Patteson
> Molalla, Oregon
>
>

I disagree that you could get almost any shape. The sharpest curvature
is going to be right where the spar is, and it may depend to some
extent on the plywood you are using. A real airfoil isn't going to
look like that. How about using thinner plywood and some ribs to
control the shape, just like an airplane wing? Shouldn't be that much
harder to build, and if you're careful you can get a very good shape.
If you go this way, can't figure out how to get a good plot, and don't
have too huge of a board, I could send you a couple of plots of one of
the airfoils I have in my computer with the thickness of the plywood
subtracted. I wouldn't worry much about the strength as long as
there's a little extra beef right where the board exits the bottom of
the boat. The increased thickness of the foil will make it strong
enough.

If I were doing it, I'd use a hot wire to cut out an appropriately
shaped piece of extruded styrene foam and add a bunch of layers of
glass, but then I'm already used to that process and have the tools
on hand. (they're cheap, but it's probably cheaper to do one board by
building it up from wood pieces).

Alternatively, I might carve from foam or thick balsa, per
instructions for sanding tail on Apogee and Allegro-Lite
model airplanes on www.charlesriverrc.org. I think if you had a power
plane this might be a viable way to make a good foil quickly from
solid wood. But it takes a bit of head scratching to make sure you're
doing it right.

THis is only going to improve the performance of your boat a little
bit, mind you.

--- In bolger@y..., pateson@c... wrote:
> Hollow "Wing" Centerboard:
> It seems to be the consensus that a foil shaped board would be
better.
>
> Does anyone find a "Fatal Flaw" in my "Hollow Board" idea?
>
> A board built much like an airplane wing, with a vertical
> "Spar" with "Skins" of plywood. All sheathed in glass.
> Almost any shape could be obtained with proper selection
> and placing of the spar, and it would seem to be about
> as much work as trying to plane, saw or rout a solid piece to shape.
> Any "Harpoints" such as Bearing hole could be made with a solid
> piece inside.
> It should be as strong, or stronger that a "Solid" or "Solid
> Plywood" board as it would have intact plywood on the outside
> plus the glass sheathing.
> Being hollow, it would have the added benifit of being able
> to place lead down low without having to drill or cut a
> hole in the board for lead.
>
> Any criticism? It sounds good to me.
>
> Pat Patteson
> Molalla, Oregon
>
>
> --- In bolger@y..., cha62759@t... wrote:
> > --- In bolger@y..., richard@s... wrote:
> > > Naw, I'll shape the board to a foil section I think. 'Cuz I want
> to!
> >
> > Hi Richard,
> > Some years ago I built a center hull for the Dick Newick Trimaran
> > "Tremolino".
> >
> > T has a daggerboard about16"x5'. Plans call for a symetrical
> airfoil
> > about the shape I was familiar with with control-line model
> airplanes.
> > To
> > construct it I drew the airfoil full size, measured the offsets
> every
> > inch or so and then set the table saw to cut almost the
> > distance of the offsets on my blank. This didn't take much
material
> > off but it did make a good guide for rapid removal of the material
> > with an power plane. I used some odd bits of western redcedar I
had
> > laying around since it was an experiment. It worked out so well
> that I
> > went whole hog, finished it bright and it was great. Of course
> with a
> > daggarboard I could rip to the end, with a centerboard it would be
> > necessary to lift the board at the appropriate location. It did
> > simplify making the airfoil.
> >
> > Bob Chamberland

Nope
All sealed up nice and tight.
Bottom can be same shape as rest of board, with foil
shaped plug in the end,(Piper Cherokee) or tapered and rounded,
with a little "Torturing" of plywood skin.(Piper Warrior)
Or entire board can be shaped with just some movement
of the spar. Spar can also be tapered top to bottom
to suit.

Just a thought. If it were used as a daggerboard, it
could have a "Wing" on the bottom of it.
Would not be removable, but pretty cool underwater dynamics.
Enough of the proper foil shape down there, and you wouldn't
need balast. It would just suck the boat down.

Pat Patteson
Molalla, Oregon

--- In bolger@y..., willsamson@y... wrote:
> Pat - Would you make it free-flooding? The weight of water might
> help a little. Some of Phil's designs have free-flooding hollow
> keels for exactly this reason. OTOH the presence of holes might
> disturb the hydrodynamics.
>
> Thoughts?
>
> Bill
>
> --- In bolger@y..., pateson@c... wrote:
> > Hollow "Wing" Centerboard:
> > It seems to be the consensus that a foil shaped board would be
> better.
> >
> > Does anyone find a "Fatal Flaw" in my "Hollow Board" idea?
> >
> > A board built much like an airplane wing, with a vertical
> > "Spar" with "Skins" of plywood. All sheathed in glass.
> > Almost any shape could be obtained with proper selection
> > and placing of the spar, and it would seem to be about
> > as much work as trying to plane, saw or rout a solid piece to
shape.
> > Any "Harpoints" such as Bearing hole could be made with a solid
> > piece inside.
> > It should be as strong, or stronger that a "Solid" or "Solid
> > Plywood" board as it would have intact plywood on the outside
> > plus the glass sheathing.
> > Being hollow, it would have the added benifit of being able
> > to place lead down low without having to drill or cut a
> > hole in the board for lead.
> >
> > Any criticism? It sounds good to me.
> >
> > Pat Patteson
> > Molalla, Oregon
> >
> >

Pat - Would you make it free-flooding? The weight of water might
help a little. Some of Phil's designs have free-flooding hollow
keels for exactly this reason. OTOH the presence of holes might
disturb the hydrodynamics.

Thoughts?

Bill

--- In bolger@y..., pateson@c... wrote:
> Hollow "Wing" Centerboard:
> It seems to be the consensus that a foil shaped board would be
better.
>
> Does anyone find a "Fatal Flaw" in my "Hollow Board" idea?
>
> A board built much like an airplane wing, with a vertical
> "Spar" with "Skins" of plywood. All sheathed in glass.
> Almost any shape could be obtained with proper selection
> and placing of the spar, and it would seem to be about
> as much work as trying to plane, saw or rout a solid piece to shape.
> Any "Harpoints" such as Bearing hole could be made with a solid
> piece inside.
> It should be as strong, or stronger that a "Solid" or "Solid
> Plywood" board as it would have intact plywood on the outside
> plus the glass sheathing.
> Being hollow, it would have the added benifit of being able
> to place lead down low without having to drill or cut a
> hole in the board for lead.
>
> Any criticism? It sounds good to me.
>
> Pat Patteson
> Molalla, Oregon
>
>

Hollow "Wing" Centerboard:
It seems to be the consensus that a foil shaped board would be better.

Does anyone find a "Fatal Flaw" in my "Hollow Board" idea?

A board built much like an airplane wing, with a vertical
"Spar" with "Skins" of plywood. All sheathed in glass.
Almost any shape could be obtained with proper selection
and placing of the spar, and it would seem to be about
as much work as trying to plane, saw or rout a solid piece to shape.
Any "Harpoints" such as Bearing hole could be made with a solid
piece inside.
It should be as strong, or stronger that a "Solid" or "Solid
Plywood" board as it would have intact plywood on the outside
plus the glass sheathing.
Being hollow, it would have the added benifit of being able
to place lead down low without having to drill or cut a
hole in the board for lead.

Any criticism? It sounds good to me.

Pat Patteson
Molalla, Oregon

--- In bolger@y..., cha62759@t... wrote:
> --- In bolger@y..., richard@s... wrote:
> > Naw, I'll shape the board to a foil section I think. 'Cuz I want
to!
>
> Hi Richard,
> Some years ago I built a center hull for the Dick Newick Trimaran
> "Tremolino".
>
> T has a daggerboard about16"x5'. Plans call for a symetrical
airfoil
> about the shape I was familiar with with control-line model
airplanes.
> To
> construct it I drew the airfoil full size, measured the offsets
every
> inch or so and then set the table saw to cut almost the
> distance of the offsets on my blank. This didn't take much material
> off but it did make a good guide for rapid removal of the material
> with an power plane. I used some odd bits of western redcedar I had
> laying around since it was an experiment. It worked out so well
that I
> went whole hog, finished it bright and it was great. Of course
with a
> daggarboard I could rip to the end, with a centerboard it would be
> necessary to lift the board at the appropriate location. It did
> simplify making the airfoil.
>
> Bob Chamberland

Richard:

I like the UHMW idea. You may remember that I used it for parrels on my
Caprice. Also for hatch glides. You can get extruded bushing stock from
McMaster-carr with 1-1/4" ID and various OD's.

Chuck

>
>
> Ah, that would make sense.
>
> Googling shows quite a few references to "uhmw bushings aluminum
> shaft"... Even a couple of marine ones.
>
> For the low load, slow speed application of rudder, centerboard, and
> tabernacle pivot, think I could get away with 1 1/8" aluminum
> shafting and uhmw poly bushings?
>
> I suspect the bushings and shafts would last quite a few years of
> normal trailer sailing use. I'd be sure to design the setup so it's
> easy to dissassemble for inspections and/or replacements.
>
>
> --- In bolger@y..., kwilson800@a... wrote:
> > Why doesn't aluminum make a good bearing? The reason bare aluminum
> > doesn't "rust" in normal use is that it forms a very thin coating
> of
> > aluminum oxide on the surface which inhibits further corrosion. In
> a
> > bearing application, this coating is continuously worn off and
> > renewed. Well, guess what, the aluminuum oxide left inside the
> > beaing is quite an effective abrasive. You could probably hardcoat
> > anodize it, or "hardlube", which is hardcoat anodizing impregnated
> > with teflon. There are also several proprietary processes to make
> > aluminum into a decent bearing surface, "Nituff" is one of the
> better-
> > known ones, but by the time you've gone through all that trouble,
> why
> > not just use bronze or stainless steel in the first place?
> >
> > Keith Wilson
> >
> > --- In bolger@y..., richard@s... wrote:
> > > UHMW poly has a pretty low melting point. Wonder if I could cast
> > > parts out of it?
> > >
> > > Also, why doesn't it work well with aluminum?
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - pls take "personals" off-list, stay on topic, and punctuate
> - add your comments at the TOP and SIGN your posts, snip all you like
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209,
> Gloucester, MA, 01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/
>
>
>

Even at an angle of attack of 0, a proper foil has much less drag than
a flat plate. But you probably need to do a good job shaping it.

--- In bolger@y..., wmrpage@a... wrote:
> In a message dated 8/20/01 12:23:30 PM Central Daylight Time,
> cha62759@t... writes:
>
>
> > I drew the airfoil full size, measured the offsets every
> > inch or so and then set the table saw to cut almost the
> > distance of the offsets on my blank. This didn't take much
material
> > off but it did make a good guide for rapid removal of the material
> >
>
> Obviously, the same technique could be used with a dado blade and a
little
> low cunning to remove more material - probably not worth the bother
on a thin
> DB or CB, but maybe worth it on a fat rudder.
>
> Somewhere on the web, Craig O'Donnell has an somewhat interesting
posting on
> foils. (Its not on his site, but I think you can get from one to the
other).
> He includes a link to a shareware program called "NACAGEN" which
presumably
> will generate offsets for NACA foils of various properties. (I
haven't tried
> it - using shareware is as yet beyond my capability - I'm still
struggling to
> get "HULLS" operational) This might be useful for someone trying to
optimize
> performance. O'Donnell says that CB/DB's ordinarily operate at such
a small
> angle of attack that the advantge of a foil over a flat plate is not
great. I
> wouldn't know. My personal, unreliable, subjective experience is
that small
> amount of effort involved in tapering the square trailing edges on a
board
> and ruddder to a point is well worth the bother.
>
> Bill in MN
>
>
> [Non-text portions of this message have been removed]

In a message dated 8/20/01 12:23:30 PM Central Daylight Time,
cha62759@...writes:

> I drew the airfoil full size, measured the offsets every
> inch or so and then set the table saw to cut almost the
> distance of the offsets on my blank. This didn't take much material
> off but it did make a good guide for rapid removal of the material
>

Obviously, the same technique could be used with a dado blade and a little
low cunning to remove more material - probably not worth the bother on a thin
DB or CB, but maybe worth it on a fat rudder.

Somewhere on the web, Craig O'Donnell has an somewhat interesting posting on
foils. (Its not on his site, but I think you can get from one to the other).
He includes a link to a shareware program called "NACAGEN" which presumably
will generate offsets for NACA foils of various properties. (I haven't tried
it - using shareware is as yet beyond my capability - I'm still struggling to
get "HULLS" operational) This might be useful for someone trying to optimize
performance. O'Donnell says that CB/DB's ordinarily operate at such a small
angle of attack that the advantge of a foil over a flat plate is not great. I
wouldn't know. My personal, unreliable, subjective experience is that small
amount of effort involved in tapering the square trailing edges on a board
and ruddder to a point is well worth the bother.

Bill in MN


[Non-text portions of this message have been removed]

My only concern with UHMW poly is that it is very soft and may get
chewed up by sand and grit that may find their way into the bearing.
Delrin is much tougher. HOwever, I have no experience with either in
this specific application. I have employed teflon cut into disks as a
bearing surface against stainless in my modified Swifty's inboard
rudder and that's real smooth.

Whatever materials you use, design the wear parts so that
replacements are real easy to make and install.

Steve

If you're intent on using the aluminum shaft and UHMW, why not use a
press fit bushing on the aluminum? This way it won't dig up the
aluminum oxide and machine away the shaft. Anyone who's been on an
alloy wheel bike in the rain much probably knows what I'm talking
about. Anyone who's done the same with steel probably isn't with us
anymore or is at least missing a few teeth due to lack of friction.

I'd be tempted to get some of that heavy wall fiberglass tubing for
both pivot (with appropriate UHMW bushings) and rudder stock. Small
Parts (www.smallparts.com, I think) and probably other places have
it, not sure if they have right size. You'll pay a premium at Small
Parts, probably.

--- In bolger@y..., richard@s... wrote:
> Ah, that would make sense.
>
> Googling shows quite a few references to "uhmw bushings aluminum
> shaft"... Even a couple of marine ones.
>
> For the low load, slow speed application of rudder, centerboard, and
> tabernacle pivot, think I could get away with 1 1/8" aluminum
> shafting and uhmw poly bushings?
>
> I suspect the bushings and shafts would last quite a few years of
> normal trailer sailing use. I'd be sure to design the setup so it's
> easy to dissassemble for inspections and/or replacements.
>
>
> --- In bolger@y..., kwilson800@a... wrote:
> > Why doesn't aluminum make a good bearing? The reason bare
aluminum
> > doesn't "rust" in normal use is that it forms a very thin coating
> of
> > aluminum oxide on the surface which inhibits further corrosion.
In
> a
> > bearing application, this coating is continuously worn off and
> > renewed. Well, guess what, the aluminuum oxide left inside the
> > beaing is quite an effective abrasive. You could probably
hardcoat
> > anodize it, or "hardlube", which is hardcoat anodizing impregnated
> > with teflon. There are also several proprietary processes to make
> > aluminum into a decent bearing surface, "Nituff" is one of the
> better-
> > known ones, but by the time you've gone through all that trouble,
> why
> > not just use bronze or stainless steel in the first place?
> >
> > Keith Wilson
> >
> > --- In bolger@y..., richard@s... wrote:
> > > UHMW poly has a pretty low melting point. Wonder if I could cast
> > > parts out of it?
> > >
> > > Also, why doesn't it work well with aluminum?

Oh, now I understand. There's a goodly chunk of 1-1/8" diameter
aluminum sitting in the corner of your shop. Sure, why not. It'll
last a long time, at least in fresh water. I've made an awful lot of
materials choices the same way myself. I might use a, say, 1/2"
stainless rod (or bolt with the threads cut off) for the CB pivot,
since it's harder to get to than the others, and then you'd be able
to forget about it for a very long time.

One final point about aluminum in salt water (and I'm FAR from an
expert about this): the "normal" extruded Al shapes, including
rounds, are either 2000 or 6000 series; 6061-T6 is very common.
Marine alloys, (which they make very nice boats out of, BTW) are
usually 5000 series, which don't contain any copper. Most other Al
alloys do, and copper and aluminum together make a good battery when
immersed in salt water, rather to the detriment of the aluminum.
Anyway, keep a good eye on the rudder stock if you ever have her in
salt water for any length of time, and fer gosh sakes don't sail off
to Bora Bora in her.

--- In bolger@y..., richard@s... wrote:
> For the low load, slow speed application of rudder, centerboard,
and
> tabernacle pivot, think I could get away with 1 1/8" aluminum
> shafting and uhmw poly bushings?
>
> I suspect the bushings and shafts would last quite a few years of
> normal trailer sailing use. I'd be sure to design the setup so it's
> easy to dissassemble for inspections and/or replacements.

--- In bolger@y..., ghartc@p... wrote:

> Check Cadillac Plastic's, or similar, drop-offs bucket for Delrin,
> Teflon, HD Poly (UHMW), or Nylon. No waiting. Machines easily -

if

> you must use al., at least keep it separated by a bearing.
>

Isn't really a "must", but a "I already have this sitting there
gathering dust. Can I use it?"

> Trailing edges should be flat - up to about 1/4" wide with sharp
> edges. Sheds the vortices rather than developing turbulent flow on
> the board. Beveling the flat to about 30 degrees is said to cause
> the port/starb vertices to miss each other rather than banging head-
> on.
>

Haven't heard that explanation, but it makes more sense than mine.

> For the same reason, sharpen the transom's trailing edge.
>

? Should the transom be in the water?

> Your 2" tube, assuming a .1" wall, is twice as strong geometrically
> as your 1.125" solid bar, and probably 2-3 times stronger again due
> to material choice.
>

Ah. That was what I was looking for. So, my proposed rudder shaft is
on the light side. Would a 1.75" OD Al pipe, .25" walls be in the
same ballpark as the 2" OD .1" wall SS?

> GHC
>
> --- In bolger@y..., richard@s... wrote:
> > McMaster (good site, I spend lots of $$ there...) has UHMW poly,

3"

> > round stock, for $11.98 a foot. Sounds like the perfect thing to
> > machine some bushings out of!
> >
> > --- In bolger@y..., kwilson800@a... wrote:
> > > Y'know, the more I think of it, the more UHMW (ultra-high
> molecular
> > > weight) polyethylene looks like it would make a really good
> bearing
> > > material. It works with almost any smooth hard metal (not very
> > well
> > > with aluminum), is almost completely impervious to salt or

fresh

> > > water, and lasts just about forever. For low-speed, low-load
> > > bearings, (which describes the rudder and CB pivot exactly) it
> > should
> > > work very well. It's relatively easy to machine, comes in a

lot

> of
> > > different shapes, and is not too expensive. The detriments are
> > that
> > > you can't glue it with anything that I know of, and it's not

very

> > > strong or stiff compared to metal. Great for bushings in

holes,

> or
> > > wear plates. I made some rudder gudgeons out of it 12 years

ago,

> > and
> > > they show no discernible wear. Look up McMaster-Carr's website
> > > (which is an experience in itself):http://www.mcmaster.com/

and

> > > search on UHMW.
> > >
> > > Keith Wilson

Ah, that would make sense.

Googling shows quite a few references to "uhmw bushings aluminum
shaft"... Even a couple of marine ones.

For the low load, slow speed application of rudder, centerboard, and
tabernacle pivot, think I could get away with 1 1/8" aluminum
shafting and uhmw poly bushings?

I suspect the bushings and shafts would last quite a few years of
normal trailer sailing use. I'd be sure to design the setup so it's
easy to dissassemble for inspections and/or replacements.

--- In bolger@y..., kwilson800@a... wrote:
> Why doesn't aluminum make a good bearing? The reason bare aluminum
> doesn't "rust" in normal use is that it forms a very thin coating
of
> aluminum oxide on the surface which inhibits further corrosion. In
a
> bearing application, this coating is continuously worn off and
> renewed. Well, guess what, the aluminuum oxide left inside the
> beaing is quite an effective abrasive. You could probably hardcoat
> anodize it, or "hardlube", which is hardcoat anodizing impregnated
> with teflon. There are also several proprietary processes to make
> aluminum into a decent bearing surface, "Nituff" is one of the
better-
> known ones, but by the time you've gone through all that trouble,
why
> not just use bronze or stainless steel in the first place?
>
> Keith Wilson
>
> --- In bolger@y..., richard@s... wrote:
> > UHMW poly has a pretty low melting point. Wonder if I could cast
> > parts out of it?
> >
> > Also, why doesn't it work well with aluminum?

Check Cadillac Plastic's, or similar, drop-offs bucket for Delrin,
Teflon, HD Poly (UHMW), or Nylon. No waiting. Machines easily - if
you must use al., at least keep it separated by a bearing.

Trailing edges should be flat - up to about 1/4" wide with sharp
edges. Sheds the vortices rather than developing turbulent flow on
the board. Beveling the flat to about 30 degrees is said to cause
the port/starb vertices to miss each other rather than banging head-
on.

For the same reason, sharpen the transom's trailing edge.

Your 2" tube, assuming a .1" wall, is twice as strong geometrically
as your 1.125" solid bar, and probably 2-3 times stronger again due
to material choice.

GHC

--- In bolger@y..., richard@s... wrote:
> McMaster (good site, I spend lots of $$ there...) has UHMW poly, 3"
> round stock, for $11.98 a foot. Sounds like the perfect thing to
> machine some bushings out of!
>
> --- In bolger@y..., kwilson800@a... wrote:
> > Y'know, the more I think of it, the more UHMW (ultra-high
molecular
> > weight) polyethylene looks like it would make a really good
bearing
> > material. It works with almost any smooth hard metal (not very
> well
> > with aluminum), is almost completely impervious to salt or fresh
> > water, and lasts just about forever. For low-speed, low-load
> > bearings, (which describes the rudder and CB pivot exactly) it
> should
> > work very well. It's relatively easy to machine, comes in a lot
of
> > different shapes, and is not too expensive. The detriments are
> that
> > you can't glue it with anything that I know of, and it's not very
> > strong or stiff compared to metal. Great for bushings in holes,
or
> > wear plates. I made some rudder gudgeons out of it 12 years ago,
> and
> > they show no discernible wear. Look up McMaster-Carr's website
> > (which is an experience in itself):http://www.mcmaster.com/and
> > search on UHMW.
> >
> > Keith Wilson

Never heard of remelting and casting UHMW, although that certainly
doesn't mean it won't work. Plastics are generally very viscous when
melted and need a lot of pressure to force them into the mold. You
might also check if it starts to decompose at near its melting
temperature. My guess is that it'll be more trouble than it's worth,
since it's easy to machine.

Why doesn't aluminum make a good bearing? The reason bare aluminum
doesn't "rust" in normal use is that it forms a very thin coating of
aluminum oxide on the surface which inhibits further corrosion. In a
bearing application, this coating is continuously worn off and
renewed. Well, guess what, the aluminuum oxide left inside the
beaing is quite an effective abrasive. You could probably hardcoat
anodize it, or "hardlube", which is hardcoat anodizing impregnated
with teflon. There are also several proprietary processes to make
aluminum into a decent bearing surface, "Nituff" is one of the better-
known ones, but by the time you've gone through all that trouble, why
not just use bronze or stainless steel in the first place?

Keith Wilson

--- In bolger@y..., richard@s... wrote:
> UHMW poly has a pretty low melting point. Wonder if I could cast
> parts out of it?
>
> Also, why doesn't it work well with aluminum?

Getting in on the end of this, I would agree that you should consider
machining HD Poly (UHMW), Delrin, Teflon, or even nylon. Cadillac
Plastics used to have a drop-offs bucket, as I would expect most
plastics houses do. Easy to machine.

GHC

--- In bolger@y..., richard@s... wrote:
> McMaster (good site, I spend lots of $$ there...) has UHMW poly, 3"
> round stock, for $11.98 a foot. Sounds like the perfect thing to
> machine some bushings out of!
>
> --- In bolger@y..., kwilson800@a... wrote:
> > Y'know, the more I think of it, the more UHMW (ultra-high
molecular
> > weight) polyethylene looks like it would make a really good
bearing
> > material. It works with almost any smooth hard metal (not very
> well
> > with aluminum), is almost completely impervious to salt or fresh
> > water, and lasts just about forever. For low-speed, low-load
> > bearings, (which describes the rudder and CB pivot exactly) it
> should
> > work very well. It's relatively easy to machine, comes in a lot
of
> > different shapes, and is not too expensive. The detriments are
> that
> > you can't glue it with anything that I know of, and it's not very
> > strong or stiff compared to metal. Great for bushings in holes,
or
> > wear plates. I made some rudder gudgeons out of it 12 years ago,
> and
> > they show no discernible wear. Look up McMaster-Carr's website
> > (which is an experience in itself):http://www.mcmaster.com/and
> > search on UHMW.
> >
> > Keith Wilson

McMaster (good site, I spend lots of $$ there...) has UHMW poly, 3"
round stock, for $11.98 a foot. Sounds like the perfect thing to
machine some bushings out of!

--- In bolger@y..., kwilson800@a... wrote:
> Y'know, the more I think of it, the more UHMW (ultra-high molecular
> weight) polyethylene looks like it would make a really good bearing
> material. It works with almost any smooth hard metal (not very
well
> with aluminum), is almost completely impervious to salt or fresh
> water, and lasts just about forever. For low-speed, low-load
> bearings, (which describes the rudder and CB pivot exactly) it
should
> work very well. It's relatively easy to machine, comes in a lot of
> different shapes, and is not too expensive. The detriments are
that
> you can't glue it with anything that I know of, and it's not very
> strong or stiff compared to metal. Great for bushings in holes, or
> wear plates. I made some rudder gudgeons out of it 12 years ago,
and
> they show no discernible wear. Look up McMaster-Carr's website
> (which is an experience in itself):http://www.mcmaster.com/and
> search on UHMW.
>
> Keith Wilson

Hello again,

I can't comment much on what has gone before on this thread however
this morning I went for a sail and when I picked up my mooring with my
telescoping aluminum boathook it was jammed with sand. The point is
that sand is hell on aluminum and you might want to consider that
since you may be beaching your boat.

Bob Chamberland

--- In bolger@y..., richard@s... wrote:

> Naw, I'll shape the board to a foil section I think. 'Cuz I want to!

Hi Richard,
Some years ago I built a center hull for the Dick Newick Trimaran
"Tremolino".

T has a daggerboard about16"x5'. Plans call for a symetrical airfoil
about the shape I was familiar with with control-line model airplanes.
To
construct it I drew the airfoil full size, measured the offsets every
inch or so and then set the table saw to cut almost the
distance of the offsets on my blank. This didn't take much material
off but it did make a good guide for rapid removal of the material
with an power plane. I used some odd bits of western redcedar I had
laying around since it was an experiment. It worked out so well that I
went whole hog, finished it bright and it was great. Of course with a
daggarboard I could rip to the end, with a centerboard it would be
necessary to lift the board at the appropriate location. It did
simplify making the airfoil.

Bob Chamberland

UHMW poly has a pretty low melting point. Wonder if I could cast
parts out of it?

Also, why doesn't it work well with aluminum?

--- In bolger@y..., kwilson800@a... wrote:
> Y'know, the more I think of it, the more UHMW (ultra-high molecular
> weight) polyethylene looks like it would make a really good bearing
> material. It works with almost any smooth hard metal (not very
well
> with aluminum), is almost completely impervious to salt or fresh
> water, and lasts just about forever. For low-speed, low-load
> bearings, (which describes the rudder and CB pivot exactly) it
should
> work very well. It's relatively easy to machine, comes in a lot of
> different shapes, and is not too expensive. The detriments are
that
> you can't glue it with anything that I know of, and it's not very
> strong or stiff compared to metal. Great for bushings in holes, or
> wear plates. I made some rudder gudgeons out of it 12 years ago,
and
> they show no discernible wear. Look up McMaster-Carr's website
> (which is an experience in itself):http://www.mcmaster.com/and
> search on UHMW.
>
> Keith Wilson

Good luck with your boat. They appear very nice.
Almost decided to build one a while ago, but I've had
my "Sailing days", and with a Hobie I can "Sail" if I want
to.
My next boat is going to be a GP-16/18. I want to cruise
in comfort, and be able to stand up. (I'm gettin too old
for "Sitting height" and my head already has too many knots
on it.)
Probably not goiing to put the 50 HP recomended, but 15 HP
or so, and cruise at "Sailing speed" but in a straight line.
I'm in no hurry to "Get" anywhere. Ramp will be great for
getting my wife and my broken old bodies on an off.

Take my ideas for what you paid for them.

Have Fun.

Pat Patteson
Molalla, Oregon

If you need more strength, I recall that Delrin is an acceptable
bearing material. But do your homework now, as it will be easier than
removing things later. I've used UHMW a bit, and it's almost as
slippery as teflon! If you look around, you may be able to get some of
these materials made up into bearings already. You might try looking
at sources for the food industry, as some of these things have to deal
with very corrosive environments (say, cooking in hot, maybe even
salty water). It's been too long and I don't remember the companies
anymore from the time I helped design a 50 foot long bagel cooker.

--- In bolger@y..., kwilson800@a... wrote:
> Y'know, the more I think of it, the more UHMW (ultra-high molecular
> weight) polyethylene looks like it would make a really good bearing
> material. It works with almost any smooth hard metal (not very well
> with aluminum), is almost completely impervious to salt or fresh
> water, and lasts just about forever. For low-speed, low-load
> bearings, (which describes the rudder and CB pivot exactly) it
should
> work very well. It's relatively easy to machine, comes in a lot of
> different shapes, and is not too expensive. The detriments are that
> you can't glue it with anything that I know of, and it's not very
> strong or stiff compared to metal. Great for bushings in holes, or
> wear plates. I made some rudder gudgeons out of it 12 years ago,
and
> they show no discernible wear. Look up McMaster-Carr's website
> (which is an experience in itself):http://www.mcmaster.com/and
> search on UHMW.
>
> Keith Wilson

Y'know, the more I think of it, the more UHMW (ultra-high molecular
weight) polyethylene looks like it would make a really good bearing
material. It works with almost any smooth hard metal (not very well
with aluminum), is almost completely impervious to salt or fresh
water, and lasts just about forever. For low-speed, low-load
bearings, (which describes the rudder and CB pivot exactly) it should
work very well. It's relatively easy to machine, comes in a lot of
different shapes, and is not too expensive. The detriments are that
you can't glue it with anything that I know of, and it's not very
strong or stiff compared to metal. Great for bushings in holes, or
wear plates. I made some rudder gudgeons out of it 12 years ago, and
they show no discernible wear. Look up McMaster-Carr's website
(which is an experience in itself):http://www.mcmaster.com/and
search on UHMW.

Keith Wilson

--- In bolger@y..., richard@s... wrote:

> Naw, I'll shape the board to a foil section I think. 'Cuz I want to!

Foil Shapped Hollow Board.

I designed a "Foil" shaped leeboard for my "Elegant Punt".
(the ultimate in low speed and high drag)
It was an experiment in light weight, and high strenght.

I modified it to be built of two outside layers of 1/4"
ply, and a vertical spar inside. All covered with glass.
(Took as long to build as the boat.)
Kind of cool idea.
Kind of like an airplane wing. Spar about 2/5 of the way
from the leading edge, so gives a NACA Airfoil (of some number)
shape to the board. Very important on an "Elegant Punt".
Idea would be great for dagger or center boards.
Very stong, and light weight, and hollow, so balast could
be poured in to put it down low where it should be.
1/2-" leading and trailing edges. Leading rounded, trailing
tapered.

--- In bolger@y..., pateson@c... wrote:

> Is the rudder supported by pintals above and below?

Yes.

> If so, I would think 1 1/8" solid would be plenty strong.

Good. Think I'll buy some uhmw polyethelely bushing stock. Can get a
5 foot length for a reasonable price from McMaster.

> How much does the post extend between the top of the
> rudder and the tiller? That would seem to be the only

Rudder is under the boat. Goes from pintle on the bottom to the,
bearing on hull, (16" or so), to bearing under tiller (20" or so)
(not sure exact numbers there)

> Do you have the board built? If not, check my note on
> Symplified Foils. Very strong with room for lead in
> bottom, and "Cool" shape.
> >

Naw, I'll shape the board to a foil section I think. 'Cuz I want to!

--- In bolger@y..., richard@s... wrote:

> --- In bolger@y..., pateson@c... wrote:
> > I'm not an engineer, but I play one on TV.
> :-)
> > Sounds plenty strong.
> That's what I was thinking, but wanted a second opinion. I have

about

> 5ft of the bar setting on the bench.
>
> Another question, the plans call for a 2" diamater SS tube for the
> rudder post. I'm assuming it's a tube and not solid. Would a 1 1/8"
> solid aluminum bar be a suitlble substitue for the 2" SS tube?

Is the rudder supported by pintals above and below?
If so, I would think 1 1/8" solid would be plenty strong.
My Hobie 16 has only about 1/2 pins supporting rudders, and they
take a Lot of force.
How much does the post extend between the top of the
rudder and the tiller? That would seem to be the only
"Week" point. For bending forces on the post, but again,
bending 1 1/8" solid aluminum over so short a distance
would be tough.
Again, smooth bearing surfaces would be good. Rudder will move
a gazillion times.
I was thinking of some sort of High density plastic/teflon
type material, both for the board, and the rudder, and the inside
of the board case.

>
> > I am ignoarant on Chebacco Boards. Wood or Metal?
> Wood, with lead in the bottom to sink it.

Do you have the board built? If not, check my note on
Symplified Foils. Very strong with room for lead in
bottom, and "Cool" shape.

>
> > A bushing of some sort in the board to bear on the
> > rod would probably be good.
> I was thinking of an aluminum bearing surface. Wouldn't want to mix
> the difffert metals in the marine environment...

Again, "Plastic"? Now worry. Very slick, quiet,no electrolisis, and
replacable if necessary.

>
> > And , as you say, the side forces would be taken by the
> > case, some sort of low friction bearing surface on the inside
> > of the case would make raising or lowering under load easier.
> Not sure you often would need to raise it under load. Since the
> weight is what lowers it, not sure you COULD lower it under load.
> Still, a nice coating of graphite/epoxy on the inside of the case
> wouldn't hurt.
>
> Also, I thought about having bearing surfaces at the pivot point,

and

> the opening, but I'm back and forth about it. Might be simpler and
> just as effective to make the entire inside smooth and slick.
>
> Can't make it to tight. Even with epoxy and glass, I bet the board
> will absorb water and swell some. Anybody have any idea how much
> clearance I need to leave on the board sides? I was thinking about
> 1/8" clearance on both sides of the board. Thoughts anyone?

"Plastics" ( I sound like the guy in "The Graduate")
1/8" sounds good. Don't want it to jam, and don't want it to
bang. I would err a little on the sloppy side, as wood and
glass against a plastic surface would be quieter than steel
against glass.

>
> > I have a 17' Sloop with a flat plate steel board, and use
> > the board to trim the boat, raising or lowering slightly
> > too improve helm. I guess that can be done with the mizzen
> > but smooth would be nice. Might also be able to make board
> > fit a little more snugly in case. Mine is quite loose,
> > and bangs against the sides when not under load.
> > What is the "Uphaul" mechanism?
>
> Very complicated one called "rope an hole". Weight in board causes
> close to neutral boyancy, doen't take much force to lift the board.

Perfect

>
> >
> > Pat Patteson
> > Molalla, Oregon
> >
> >
> > --- In bolger@y..., richard@s... wrote:
> > > I'm getting ready to cut and build the centerboard and case for
> the
> > > Chebacco Cruiser.
> > >
> > > The plans leave a lot to the imagination. Anybody have any
> pictures
> > > or drawings of the pivot mechanism on their centerboard boat?
> > >
> > > Also, I'm toying with making the pivot out of 1 1/8" solid
> aluminum
> > > rod, with aluminum bearing surfaces. Any of you engineer types
> want
> > > to comment? Not strong enough? To soft? I figure, most of the
> side
> > > forces will be taken by case, and it will probably only pivot a
> > > couple of thousand times in the lifetime of the boat, so wear

is

> > not
> > > really a problem....
> > >
> > > Anyone? Gregg?

--- In bolger@y..., kwilson800@a... wrote:

> Well, some thoughts on the subject from an engineer, although
> certainly no expert in marine bearings: I wouldn't do it.

Aluminum

> on aluminum, even for fresh water, makes a really lousy bearing
> surface - It corrodes and galls badly.

OK.

> For salt water, you need to be a lot more careful - DON'T mix

metals,
I want the ability to take it in salt water. No oilite bushings..

> particularly when they're in contact with each other, and certainly
> don't use aluminum. You don't want your centerboard to fall out at
> the wrong moment. Bronze on bronze is probably the best bet if the

Guess I need to get some bronze and start playing with it...

> best of the alternatives mentioned. I think that 1-1/8" dia would

be

> a wreched excess of strength for steel or bronze, (how long is the
> pivot pin between supports?) but that's fine, there's nothing wrong
> with making it too strong. Hope this helps.
>

Supports are right next to the board, probably only 2" max.

> Keith Wilson
>
> --- In bolger@y..., richard@s... wrote:
> > Also, I'm toying with making the centerboard pivot out of 1 1/8"
> > solid aluminum rod, with aluminum bearing surfaces. Any of you
> > engineer types want to comment?

--- In bolger@y..., pateson@c... wrote:

> I'm not an engineer, but I play one on TV.

:-)

> Sounds plenty strong.

That's what I was thinking, but wanted a second opinion. I have about
5ft of the bar setting on the bench.

Another question, the plans call for a 2" diamater SS tube for the
rudder post. I'm assuming it's a tube and not solid. Would a 1 1/8"
solid aluminum bar be a suitlble substitue for the 2" SS tube?

> I am ignoarant on Chebacco Boards. Wood or Metal?

Wood, with lead in the bottom to sink it.

> A bushing of some sort in the board to bear on the
> rod would probably be good.

I was thinking of an aluminum bearing surface. Wouldn't want to mix
the difffert metals in the marine environment...

> And , as you say, the side forces would be taken by the
> case, some sort of low friction bearing surface on the inside
> of the case would make raising or lowering under load easier.

Not sure you often would need to raise it under load. Since the
weight is what lowers it, not sure you COULD lower it under load.
Still, a nice coating of graphite/epoxy on the inside of the case
wouldn't hurt.

Also, I thought about having bearing surfaces at the pivot point, and
the opening, but I'm back and forth about it. Might be simpler and
just as effective to make the entire inside smooth and slick.

Can't make it to tight. Even with epoxy and glass, I bet the board
will absorb water and swell some. Anybody have any idea how much
clearance I need to leave on the board sides? I was thinking about
1/8" clearance on both sides of the board. Thoughts anyone?

> I have a 17' Sloop with a flat plate steel board, and use
> the board to trim the boat, raising or lowering slightly
> too improve helm. I guess that can be done with the mizzen
> but smooth would be nice. Might also be able to make board
> fit a little more snugly in case. Mine is quite loose,
> and bangs against the sides when not under load.
> What is the "Uphaul" mechanism?

Very complicated one called "rope an hole". Weight in board causes
close to neutral boyancy, doen't take much force to lift the board.

>
> Pat Patteson
> Molalla, Oregon
>
>
> --- In bolger@y..., richard@s... wrote:
> > I'm getting ready to cut and build the centerboard and case for

the

> > Chebacco Cruiser.
> >
> > The plans leave a lot to the imagination. Anybody have any

pictures

> > or drawings of the pivot mechanism on their centerboard boat?
> >
> > Also, I'm toying with making the pivot out of 1 1/8" solid

aluminum

> > rod, with aluminum bearing surfaces. Any of you engineer types

want

> > to comment? Not strong enough? To soft? I figure, most of the

side

> > forces will be taken by case, and it will probably only pivot a
> > couple of thousand times in the lifetime of the boat, so wear is
> not
> > really a problem....
> >
> > Anyone? Gregg?

Well, some thoughts on the subject from an engineer, although
certainly no expert in marine bearings: I wouldn't do it. Aluminum
on aluminum, even for fresh water, makes a really lousy bearing
surface - It corrodes and galls badly. If you're sailing in fresh
water only, then stainless steel on brass or bronze would be good.
If you can't find an easy source of stainless rod, you can buy a long
stainless bolt and cut off the threaded part for the pin. For
bearings, either genuine oilite (oil-impregnated sintered bronze)
bearings, or brass (pipe or hose nipple) works nicely.

For salt water, you need to be a lot more careful - DON'T mix metals,
particularly when they're in contact with each other, and certainly
don't use aluminum. You don't want your centerboard to fall out at
the wrong moment. Bronze on bronze is probably the best bet if the
rest of the underwater metal is nonferrous. Stainless on stainless
would probably work, although it's not a good bearing. Bronze on
wood is fine, too, although by rights the pin should be larger than
it would be for a metal-on-metal bearing to get more surface area.
Steel or bronze on UHMW polyethylene is excellent, and may be the
best of the alternatives mentioned. I think that 1-1/8" dia would be
a wreched excess of strength for steel or bronze, (how long is the
pivot pin between supports?) but that's fine, there's nothing wrong
with making it too strong. Hope this helps.

Keith Wilson

--- In bolger@y..., richard@s... wrote:
> Also, I'm toying with making the centerboard pivot out of 1 1/8"
> solid aluminum rod, with aluminum bearing surfaces. Any of you
> engineer types want to comment?

I'm not an engineer, but I play one on TV.
Sounds plenty strong.
I am ignoarant on Chebacco Boards. Wood or Metal?
A bushing of some sort in the board to bear on the
rod would probably be good.
And , as you say, the side forces would be taken by the
case, some sort of low friction bearing surface on the inside
of the case would make raising or lowering under load easier.
I have a 17' Sloop with a flat plate steel board, and use
the board to trim the boat, raising or lowering slightly
too improve helm. I guess that can be done with the mizzen
but smooth would be nice. Might also be able to make board
fit a little more snugly in case. Mine is quite loose,
and bangs against the sides when not under load.
What is the "Uphaul" mechanism?

Pat Patteson
Molalla, Oregon

--- In bolger@y..., richard@s... wrote:
> I'm getting ready to cut and build the centerboard and case for the
> Chebacco Cruiser.
>
> The plans leave a lot to the imagination. Anybody have any pictures
> or drawings of the pivot mechanism on their centerboard boat?
>
> Also, I'm toying with making the pivot out of 1 1/8" solid aluminum
> rod, with aluminum bearing surfaces. Any of you engineer types want
> to comment? Not strong enough? To soft? I figure, most of the side
> forces will be taken by case, and it will probably only pivot a
> couple of thousand times in the lifetime of the boat, so wear is
not
> really a problem....
>
> Anyone? Gregg?

I'm getting ready to cut and build the centerboard and case for the
Chebacco Cruiser.

The plans leave a lot to the imagination. Anybody have any pictures
or drawings of the pivot mechanism on their centerboard boat?

Also, I'm toying with making the pivot out of 1 1/8" solid aluminum
rod, with aluminum bearing surfaces. Any of you engineer types want
to comment? Not strong enough? To soft? I figure, most of the side
forces will be taken by case, and it will probably only pivot a
couple of thousand times in the lifetime of the boat, so wear is not
really a problem....

Anyone? Gregg?