Re: Tabernacle mast - Wood/carbon
I think the idea is that if you ground the mast it will be at the
voltage level of the water but considerably closer to the hypothetical
cloud. If you don't ground the mast it will float at some intermediate
voltage and not draw a strike as much. If the mast is at the voltage
of the water, it is in the middle of some air which is at a
considerably different voltage, so the electric field will be stronger
and therefore more charge will accumulate in that area. I'm not sure
that this makes a big difference, but I'd think that a stronger field
would. However, I'm no expert. Only 1 semester of E&M, or was it two?
And that was a while back. I also have no idea of the statistics
involved, or whether 100:1 is realistic. I used to live next to a
smokestack that was maybe 150 or 200 feet tall. It didn't get hit all
that often. I only remember noticing it get hit once, and that one
time was extremely noticable. I now live next to a 75 foot tree that
hangs over the house. Someday....
voltage level of the water but considerably closer to the hypothetical
cloud. If you don't ground the mast it will float at some intermediate
voltage and not draw a strike as much. If the mast is at the voltage
of the water, it is in the middle of some air which is at a
considerably different voltage, so the electric field will be stronger
and therefore more charge will accumulate in that area. I'm not sure
that this makes a big difference, but I'd think that a stronger field
would. However, I'm no expert. Only 1 semester of E&M, or was it two?
And that was a while back. I also have no idea of the statistics
involved, or whether 100:1 is realistic. I used to live next to a
smokestack that was maybe 150 or 200 feet tall. It didn't get hit all
that often. I only remember noticing it get hit once, and that one
time was extremely noticable. I now live next to a 75 foot tree that
hangs over the house. Someday....
--- In bolger@y..., wmrpage@a... wrote:
> In a message dated 6/14/02 8:13:52 AM Central Daylight Time,
> pvanderw@o... writes:
>
> Why would grounding the mast cause it to build up a larger
charge than
> otherwise?
>
> It seems to me that if the masthead is electrically connected
to the
> water that any charge at the masthead would necessarily be in
equilibrium
> with the charge of the water.
In a message dated 6/14/02 8:13:52 AM Central Daylight Time,
pvanderw@...writes:
otherwise?
It seems to me that if the masthead is electrically connected to the
water that any charge at the masthead would necessarily be in equilibrium
with the charge of the water. Of course the masthead would still be a higher
than the surface of the water and present a marginally shorter path for a
bolt, which I imagine would increase the likelihood of a strike, but by a
factor of 100? (and, what on earth can "25X safer mean on any objective
basis?)
I admit to complete ignorance on the subject and I'm sure that
everything I have read on the subject was written by advocates of grounding.
I'd appreciate a referral to any serious literature on the subject.
Ciao for Niao,
Bill in MN
[Non-text portions of this message have been removed]
pvanderw@...writes:
> Third, the downside of a good gounding system is that it makes yourWhy would grounding the mast cause it to build up a larger charge than
> boat much more likely to be struck, even as it lowers the danger per
> strike. This is because makes it easier for a large charge to develop
> at the masthead. A gounding system could make you 25 times safer per
> strike, but 100 times more likely to be struck
otherwise?
It seems to me that if the masthead is electrically connected to the
water that any charge at the masthead would necessarily be in equilibrium
with the charge of the water. Of course the masthead would still be a higher
than the surface of the water and present a marginally shorter path for a
bolt, which I imagine would increase the likelihood of a strike, but by a
factor of 100? (and, what on earth can "25X safer mean on any objective
basis?)
I admit to complete ignorance on the subject and I'm sure that
everything I have read on the subject was written by advocates of grounding.
I'd appreciate a referral to any serious literature on the subject.
Ciao for Niao,
Bill in MN
[Non-text portions of this message have been removed]
My theory on lightning protection is that if bolt of lightning can
travel across a couple of miles of thin air, then it's unlikely that
any device is going to stop it it from jumping across your protection
and frying whatever is on the other side.
travel across a couple of miles of thin air, then it's unlikely that
any device is going to stop it it from jumping across your protection
and frying whatever is on the other side.
--- In bolger@y..., "pvanderwaart" <pvanderw@o...> wrote:
> > COuldn't you put a small gap in the system some place to isolate
> the
> > mast?
>
>
> Interesting thought. I, for one, know that I don't know.
>
> It does remind me of a point in a talk on the subject by a
> sailor/meteorologist/lightning survivor when was talking about how
> the electronic equipment on the boat could get fried. He held up a
> tiny electrical part about 1cm on a side, and suggested it could
> protect a radio or depth sounder. I suppose it was a diode or fuse.
> To me, it didn't seem likely to help much considering that induced
> currents could do a lot of damage.
>
> Peter (not an electricial or engineer)
> COuldn't you put a small gap in the system some place to isolatethe
> mast?Interesting thought. I, for one, know that I don't know.
It does remind me of a point in a talk on the subject by a
sailor/meteorologist/lightning survivor when was talking about how
the electronic equipment on the boat could get fried. He held up a
tiny electrical part about 1cm on a side, and suggested it could
protect a radio or depth sounder. I suppose it was a diode or fuse.
To me, it didn't seem likely to help much considering that induced
currents could do a lot of damage.
Peter (not an electricial or engineer)
> Wasn't the original Loose Moose 2 (AS 39) sunk by lightning?Destroyed by lightning, yes, but I think it was fire rather than a
simple hole in the bottom. The story is in back archives of this list
somewhere. (Probably back too far to find easily).
COuldn't you put a small gap in the system some place to isolate the
mast? When the voltage got high enough to make a spark thousands of
feet long, it wouldn't make much difference, but wouldn't it keep the
charge from building up?
mast? When the voltage got high enough to make a spark thousands of
feet long, it wouldn't make much difference, but wouldn't it keep the
charge from building up?
--- In bolger@y..., "pvanderwaart" <pvanderw@o...> wrote:
snip
> Third, the downside of a good gounding system is that it makes your
> boat much more likely to be struck, even as it lowers the danger per
> strike. This is because makes it easier for a large charge to
develop
> at the masthead. A gounding system could make you 25 times safer per
> strike, but 100 times more likely to be struck - a bad bargain.
> Experts that I have read and talked to are equivical on the best
> course of action. Of course, if you live in Florida or the like, you
> need a good protection system to keep your boat from being destroyed
> at the dock.
>
> The best lightning protection for the coastal sailor is a good
> weather forecast and caution. And moor next to a taller boat.
>
> Peter
Wasn't the original Loose Moose 2 (AS 39) sunk by lightning?
HJ
pvanderwaart wrote:
HJ
pvanderwaart wrote:
>
> > I once spent a memorable lifetime on Lake Superior - well, perhaps
> > 45 minutes
> > to an hour - on a chartered bareboat with a deck-stepped aluminum
> > mast and no visible grounding system.
> I once spent a memorable lifetime on Lake Superior - well, perhapsHaving been out in thunderstorms in my own boats with deck-stepped
> 45 minutes
> to an hour - on a chartered bareboat with a deck-stepped aluminum
> mast and no visible grounding system.
aluminum masts and no grounding systems, I concur that it's scary and
dangerous. But you are not quite as vulnerable as you feel.
You are probably aware of the "cone of protection" arguement that if
you are within the 45 degree cone around the mast, the mast will be
struck and not you. Look at the converse: if the strike was going
to "naturally" hit outside the cone, then it won't hit your boat. And
if you are within wire rigging, you probably won't be hit directly,
even if the boat is hit.
Second, the experts say that an effective ground requires several
square feet of surface area, much more than you might have from
trailing wires. I used to carry some lengths of chain myself with
idea that if there was chain gounding each stay, the strike might go
down the stay and from there to the water. The danger, of course, is
that the strike might come down the mast to the deck and have nowhere
to go. At that point it will flash unpredictably, and likely blow a
hole in the boat, as in your example.
Third, the downside of a good gounding system is that it makes your
boat much more likely to be struck, even as it lowers the danger per
strike. This is because makes it easier for a large charge to develop
at the masthead. A gounding system could make you 25 times safer per
strike, but 100 times more likely to be struck - a bad bargain.
Experts that I have read and talked to are equivical on the best
course of action. Of course, if you live in Florida or the like, you
need a good protection system to keep your boat from being destroyed
at the dock.
The best lightning protection for the coastal sailor is a good
weather forecast and caution. And moor next to a taller boat.
Peter
In a message dated 6/13/02 10:47:02 AM Central Daylight Time,
lincolnr@...writes:
would also more or less explode, too! (Patrick O'Brian is my authority on
this. :-) On boats with wire stays, lengths of wire can be trailed in the
water from stays as a temporary expedient to provide grounding path. This is
not an option for the unstayed wood masts that Bolger is fond of.
I once spent a memorable lifetime on Lake Superior - well, perhaps 45 minutes
to an hour - on a chartered bareboat with a deck-stepped aluminum mast and no
visible grounding system. There weren't any loose wires lying conveniently at
hand, either. I found myself caught in a raging thunderstorm. I was feeling
pretty vulnerable and scared, tearing along under double reefed main and no
jib, with my mast being the tallest point for miles and lightning coming down
all around. I had my crew huddle in the companion way and tried to make
myself as low and inconspicuous and equidistant from the shrouds and back
stay as possible. Not an experience I'd care to repeat. We subsequently
learned that a boat some miles to the west of us was struck by lightning
during the same storm. No one was injured, but it blew a hole in the bottom
of the boat big enough that the crew had trouble keeping it afloat, and
indeed it sank as soon as they tied up and stopped bailing.
Ciao for Niao,
Bill in MN
[Non-text portions of this message have been removed]
lincolnr@...writes:
> BTW, It would be interesting to watch a lightning strike on a carbonI expect a lightning strike on a wooden mast, if not similarly protected,
> spar. Since carbon is sort of conductive but has a lot of resistance,
> I expect it would more or less explode
would also more or less explode, too! (Patrick O'Brian is my authority on
this. :-) On boats with wire stays, lengths of wire can be trailed in the
water from stays as a temporary expedient to provide grounding path. This is
not an option for the unstayed wood masts that Bolger is fond of.
I once spent a memorable lifetime on Lake Superior - well, perhaps 45 minutes
to an hour - on a chartered bareboat with a deck-stepped aluminum mast and no
visible grounding system. There weren't any loose wires lying conveniently at
hand, either. I found myself caught in a raging thunderstorm. I was feeling
pretty vulnerable and scared, tearing along under double reefed main and no
jib, with my mast being the tallest point for miles and lightning coming down
all around. I had my crew huddle in the companion way and tried to make
myself as low and inconspicuous and equidistant from the shrouds and back
stay as possible. Not an experience I'd care to repeat. We subsequently
learned that a boat some miles to the west of us was struck by lightning
during the same storm. No one was injured, but it blew a hole in the bottom
of the boat big enough that the crew had trouble keeping it afloat, and
indeed it sank as soon as they tied up and stopped bailing.
Ciao for Niao,
Bill in MN
[Non-text portions of this message have been removed]
> If you are going to make both the wood and carbon take the stress,you
> are REALLY going to have to do your homework or they will still becarbon
> mismatched and only one will have significant stress. Not all
> has the same stiffness and the same strain at failure! I have itfrom
> a very experienced aero prof and airplane builder that some formsof
> carbon fail at the same strain as the wood. If this is the kind youpreventing
> were using, the carbon on the inside would be loafing (at least a
> little) until the wood on the outside failed. The wood has the nice
> feature of protecting the carbon from mechanical damage and
> buckling. The wood would need to be quite thin or the carbonwouldn't
> be doing any appreciable work. I think this technique may haveGood points. On the material side, just buy the stuff WEST sells, or
> potential as carbon is so strong that using a little extra in a
> non-optimal way still leaves you with a light spar.
>
at least that has the same values. They seem to me to be the main
folks who have been proponents of this technology, and had a sideline
for a long time selling engineered wing spar plans. If you can track
down their DN 40 plans, they had full spar details in there for a DN
sized deal. One thing to keep in mind with their stuff is that it is
all stayed wing spars/aero spars. So they used carbon mostly to
spread out loads from the wires, but you can discern the principle.
I have been keeping my eyes open for about 15 years, and have
acquired little details that cumulatively are pretty informative, but
I have yet to try my first spar.
Both Nigel Irens and Dick Newick have wood carbon free standing lug
rigs. You never know what the offer of waiving a few bucks under
their noses might get you. Actualy, the techs at WEST might give you
some good heads up for free. They have so much info. I remember one
of them telling me the obscene amounts of carbon they had to throw at
Ollies' simple 90 deg ama/beam connectors. So even the engineers can
get surprised at times. There was a recent article in the WEST
Epoxyworks about making a new wing mast for Meade's tri. Another
place to get some snippets.
re: carbon on the inside
If you are going to make both the wood and carbon take the stress, you
are REALLY going to have to do your homework or they will still be
mismatched and only one will have significant stress. Not all carbon
has the same stiffness and the same strain at failure! I have it from
a very experienced aero prof and airplane builder that some forms of
carbon fail at the same strain as the wood. If this is the kind you
were using, the carbon on the inside would be loafing (at least a
little) until the wood on the outside failed. The wood has the nice
feature of protecting the carbon from mechanical damage and preventing
buckling. The wood would need to be quite thin or the carbon wouldn't
be doing any appreciable work. I think this technique may have
potential as carbon is so strong that using a little extra in a
non-optimal way still leaves you with a light spar.
re: carbon on the outside
Agreed about the undersized spar, if you don't use enough carbon.
Also, you need to protect the carbon from any local sideways loads and
mechanical damage (bolts, fittings, partners, etc.) or the mast will
go the way a friend of mine's went after the carbon was chewed on for
a while. Maybe a kevlar or glass wrap would prevent this. On the other
hand, if you use enough carbon the calculations are relatively simple
and the carbon itself is as effective as possible. The wood will help
prevent a thin carbon layer from buckling, so it's still doing
something for you. If you look at layups on carbon tubes, a
significant part of the layup is circumferential to prevent buckling,
and you can probably leave this part off.
BTW, It would be interesting to watch a lightning strike on a carbon
spar. Since carbon is sort of conductive but has a lot of resistance,
I expect it would more or less explode unless a wire was built in. I
understand that some airplanes have a metal mesh molded in to deal
with this problem. Not long ago a full sized composite glider was
destroyed in the air this way, tho I don't know if it was carbon.
If you are going to make both the wood and carbon take the stress, you
are REALLY going to have to do your homework or they will still be
mismatched and only one will have significant stress. Not all carbon
has the same stiffness and the same strain at failure! I have it from
a very experienced aero prof and airplane builder that some forms of
carbon fail at the same strain as the wood. If this is the kind you
were using, the carbon on the inside would be loafing (at least a
little) until the wood on the outside failed. The wood has the nice
feature of protecting the carbon from mechanical damage and preventing
buckling. The wood would need to be quite thin or the carbon wouldn't
be doing any appreciable work. I think this technique may have
potential as carbon is so strong that using a little extra in a
non-optimal way still leaves you with a light spar.
re: carbon on the outside
Agreed about the undersized spar, if you don't use enough carbon.
Also, you need to protect the carbon from any local sideways loads and
mechanical damage (bolts, fittings, partners, etc.) or the mast will
go the way a friend of mine's went after the carbon was chewed on for
a while. Maybe a kevlar or glass wrap would prevent this. On the other
hand, if you use enough carbon the calculations are relatively simple
and the carbon itself is as effective as possible. The wood will help
prevent a thin carbon layer from buckling, so it's still doing
something for you. If you look at layups on carbon tubes, a
significant part of the layup is circumferential to prevent buckling,
and you can probably leave this part off.
BTW, It would be interesting to watch a lightning strike on a carbon
spar. Since carbon is sort of conductive but has a lot of resistance,
I expect it would more or less explode unless a wire was built in. I
understand that some airplanes have a metal mesh molded in to deal
with this problem. Not long ago a full sized composite glider was
destroyed in the air this way, tho I don't know if it was carbon.
--- In bolger@y..., "proaconstrictor" <proaconstrictor@y...> wrote:
snip
> So you have three choices. Make the mast out of all carbon, more or
> less: Make the mast out of carbon on the outside sufficient for all
> your loads using just enough wood on the inside as a plug, this
means
> all the wood weight is redundant, and you have to use a lot of
> carbon, which raises both cost and weight:
Finally you can make a
> light wood tube, and line it with enough carbon to take the loads
> that make it past the wood. This is the most bang for the buck. It
> would be backasswards if wood was a crummy spar material in terms of
> stiffness and cycles to failure, but it excells at both.
>
> What is a bad idea is to take a spar that is a little undersized and
> put a little carbon on the outside to help out. You will end up
with
> two undersized spars working in series, and first one breaks and
then
> the other.
I moved the bolts closer together. This was a zero cost solution, and if it
didn't work, I would put angle iron on it.
I'm happy to say, moving the bolts 1.5 inches closer together has all but
eliminate the flex. In fact, the wood under the retaining plate compresses
with no visible movement of the plate now.
I about halved the lever arm from the edge of the mast to the bolt holes.
didn't work, I would put angle iron on it.
I'm happy to say, moving the bolts 1.5 inches closer together has all but
eliminate the flex. In fact, the wood under the retaining plate compresses
with no visible movement of the plate now.
I about halved the lever arm from the edge of the mast to the bolt holes.
----- Original Message -----
From: "Chuck Leinweber" <chuck_dm@...>
To: <bolger@yahoogroups.com>
Sent: Wednesday, June 12, 2002 12:15 AM
Subject: Re: [bolger] Tabernacle mast holding plate sizing
> What's the problem with a little flexing, Richard? If the mast stays up,
that should be enough.
>
> Chuck
> there is
> significant flex in the 2" steel plate. Maybe 3/16" or even almost 1/4"
flex
> out in the center. (course, the mast was bending quite a bit more than
> that...)
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - add your comments at the TOP and SIGN your posts and <snip> away
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/
>
>
>
> Or is the wieght need in the mast? For some unknown to me, boatRoumaniere reported in his Fasnet disaster book that the yachts
> design reason? If the weight is not needed I could have a total rig
> weight of less than 20lbs for my micro main sail.
>
dismasted, rolled over. The spar weight/inertia was important to
stability. But what can you do? Go back to even heavier telephone
pole sized spars?
Carbon seems to be gaining in popularity. Look at this nice Nigel
Irens lugger at:
http://www.byd.btinternet.co.uk/ROM-3.jpg
Lots of sail, no standing rigging, or winches are required. Carbon
spars by:
http://www.carbospars.com/freestanding.html
> > If you intend to add carbon to a wood spar for reinforcement,it
> > consider adding it inside the tube rather than outside. Outside
> > will take all the load onto itself, and as a result the woodinside
> > will be just a heavy plug.sounds
>
> I'm no engineer, and have no experience with carbon fiber, but this
> "Bass-Akwards" to me! What is the point of adding expensive andtensily
> strong carbon fiber to a spar if not to take a load?It will take a load, the point is so will the wood. If you put it on
the outside, it is so relatively stiff, it will take up all the load
and only pass it on once it is broken.
So you have three choices. Make the mast out of all carbon, more or
less: Make the mast out of carbon on the outside sufficient for all
your loads using just enough wood on the inside as a plug, this means
all the wood weight is redundant, and you have to use a lot of
carbon, which raises both cost and weight: Finally you can make a
light wood tube, and line it with enough carbon to take the loads
that make it past the wood. This is the most bang for the buck. It
would be backasswards if wood was a crummy spar material in terms of
stiffness and cycles to failure, but it excells at both.
What is a bad idea is to take a spar that is a little undersized and
put a little carbon on the outside to help out. You will end up with
two undersized spars working in series, and first one breaks and then
the other.
I mention this carbon problem for three reasons:
Been there done that, Oops!
It isn't obvious
Glass works nicely on the outside, so it comes naturaly to put carbon
there also.
Plenty of old windsurfing mast! A few that are 18 to 20 feet 80% to
100 % carbon fiber 5lbs light. Seems it could work on a Gaff rig less
mast height than a leg O mutton. I was thinking I could make a longer
mastbase extension out of aluminuim to fit on my micro leg O mutton
main sail.
Or is the wieght need in the mast? For some unknown to me, boat
design reason? If the weight is not needed I could have a total rig
weight of less than 20lbs for my micro main sail.
Or why not a light aluminium flag pole . They can't be all that much
$$$$$.
Todd
100 % carbon fiber 5lbs light. Seems it could work on a Gaff rig less
mast height than a leg O mutton. I was thinking I could make a longer
mastbase extension out of aluminuim to fit on my micro leg O mutton
main sail.
Or is the wieght need in the mast? For some unknown to me, boat
design reason? If the weight is not needed I could have a total rig
weight of less than 20lbs for my micro main sail.
Or why not a light aluminium flag pole . They can't be all that much
$$$$$.
Todd
--- In bolger@y..., "Richard Spelling" <richard@c...> wrote:
> You have plent of carbon fiber?
> You should send me some!
> ----- Original Message -----
> From: "ntsrfer" <ktsrfer@m...>
> To: <bolger@y...>
> Sent: Wednesday, June 12, 2002 10:49 AM
> Subject: [bolger] Re: Tabernacle mast holding plate sizing
>
>
> > Okay so for the same gaff rig and forces put on the tabernacle,
would
> > it ease the stress on the tabenacle if you could lighten the
spars by
> > half the weight or even more? Would it ease the forces created in
a
> > sloppy sea? Or is the weight needed in all the spars?
> >
> > Even for the micro mast and its sprit I was thinging carbon fiber
> > which I have plenty of. To reduce stress on the mast partner and
base
> > from sloppy seas!?
> >
> > Todd
> >
> >
> >
> > --- In bolger@y..., "pvanderwaart" <pvanderw@o...> wrote:
> > >
> > > > How much of the force on a mast,
> > > > even when close hauled, is pulling directly back on the mast?
> > >
> > > The idea of the sail plan is to produce force going forward, not
> > > backward.
> > >
> > > Seriously, when close-hauled most of the force is to the side,
and
> > > some should be forward. The top of the mast is pulled back by
the
> > > force through the peak halyard to the gaff, down the leech and
> > > through the sheets. The magnitude of this force can be judged
from
> > > the fact that you can trim the sheet in more or less easily
without
> > > the full weight/strength of a teenager.
> > >
> > > In general, it's easy to overestimate the forces and weights
> > involved
> > > with small boats. They should all be in scale with the weight of
> > the
> > > boat - half a ton.
> > >
> > > Peter
> >
> >
> >
> > Bolger rules!!!
> > - no cursing, flaming, trolling, spamming, or flogging dead horses
> > - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred'
posts
> > - add your comments at the TOP and SIGN your posts and
<snip> away
> > - To order plans: Mr. Philip C. Bolger, P.O. Box 1209,
Gloucester, MA,
> 01930, Fax: (978) 282-1349
> > - Unsubscribe: bolger-unsubscribe@y...
> > - Open discussion: bolger_coffee_lounge-subscribe@y...
> >
> > Your use of Yahoo! Groups is subject to
http://docs.yahoo.com/info/terms/
> >
> >
> >
In a message dated 6/12/02 12:17:02 PM Central Daylight Time,
proaconstrictor@...writes:
"Bass-Akwards" to me! What is the point of adding expensive and tensily
strong carbon fiber to a spar if not to take a load?
If a mast can be considered as a cantilevered beam (I believe it can properly
considered such), tension and compression loads are greatest at the outside
surfaces, while at some path down the middle (a.k.a the "neutral axis")
little force is experienced. This is the theory, at least, behind "I-beams"
which place most of the material in the flanges, separated by a "sheer web",
as well as hollow sailboat masts of all description. As I understand it, the
stuff in the middle mainly serves to keep the higher-loaded exterior faces
distanced from one another.
I have no idea how this all works out in practice, but the notion of placing
expensive, high-tensile strength carbon fiber nearer rather than farther from
the "neutral axis" strikes me as more likely to be a waste of expensive
material than anything else.
Whether epoxying carbon fiber to the exterior of a mast increases strength or
stiffness in any proportion to its cost is probably a fraught question,
depending upon a host of design details and material properties. Still, at
least one face could, if properly engineered, take advantage of the
material's tensile strength. I think the opposite face, which would be loaded
in compression, would not derive much benefit from the presence of carbon
fiber.
With this opinion and $2.50 you could buy yourself a (small) fashionable cup
of coffee.
Ciao for Niao,
Bill in MN
[Non-text portions of this message have been removed]
proaconstrictor@...writes:
> If you intend to add carbon to a wood spar for reinforcement,I'm no engineer, and have no experience with carbon fiber, but this sounds
> consider adding it inside the tube rather than outside. Outside it
> will take all the load onto itself, and as a result the wood inside
> will be just a heavy plug.
"Bass-Akwards" to me! What is the point of adding expensive and tensily
strong carbon fiber to a spar if not to take a load?
If a mast can be considered as a cantilevered beam (I believe it can properly
considered such), tension and compression loads are greatest at the outside
surfaces, while at some path down the middle (a.k.a the "neutral axis")
little force is experienced. This is the theory, at least, behind "I-beams"
which place most of the material in the flanges, separated by a "sheer web",
as well as hollow sailboat masts of all description. As I understand it, the
stuff in the middle mainly serves to keep the higher-loaded exterior faces
distanced from one another.
I have no idea how this all works out in practice, but the notion of placing
expensive, high-tensile strength carbon fiber nearer rather than farther from
the "neutral axis" strikes me as more likely to be a waste of expensive
material than anything else.
Whether epoxying carbon fiber to the exterior of a mast increases strength or
stiffness in any proportion to its cost is probably a fraught question,
depending upon a host of design details and material properties. Still, at
least one face could, if properly engineered, take advantage of the
material's tensile strength. I think the opposite face, which would be loaded
in compression, would not derive much benefit from the presence of carbon
fiber.
With this opinion and $2.50 you could buy yourself a (small) fashionable cup
of coffee.
Ciao for Niao,
Bill in MN
[Non-text portions of this message have been removed]
One of my holes is slotted, so, as you say, you can pivot it out of the way.
----- Original Message -----
From: "recree8" <arvent@...>
To: <bolger@yahoogroups.com>
Sent: Wednesday, June 12, 2002 11:41 AM
Subject: [bolger] Re: Tabernacle mast holding plate sizing
> At one time I used to install wind monitoring equipment on 10 meter
> masts that pivoted on tabernacles. We used channel iron for the cross
> pieces at the base of the mast. We only had one bolt on each end and
> one end had the bolt hole slotted, so that bolt only had to be
> loosened and the cross-piece could be swung up out of the way. On a
> small boat I would guess that aluminum channel would work. Most of
> the forces while sailing are on the mast pivot bolt are they not?
>
> Nels
>
> --- In bolger@y..., "Richard Spelling" <richard@c...> wrote:
> > Put the plate on the tabernacle to hold the mast up on the CLC
> today. The
> > plans mention in passing "turnbuckle holddown" setup.
> >
> mast was bending quite a bit more than, have a
>
>
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - add your comments at the TOP and SIGN your posts and <snip> away
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/
>
>
>
You have plent of carbon fiber?
You should send me some!
You should send me some!
----- Original Message -----
From: "ntsrfer" <ktsrfer@...>
To: <bolger@yahoogroups.com>
Sent: Wednesday, June 12, 2002 10:49 AM
Subject: [bolger] Re: Tabernacle mast holding plate sizing
> Okay so for the same gaff rig and forces put on the tabernacle, would
> it ease the stress on the tabenacle if you could lighten the spars by
> half the weight or even more? Would it ease the forces created in a
> sloppy sea? Or is the weight needed in all the spars?
>
> Even for the micro mast and its sprit I was thinging carbon fiber
> which I have plenty of. To reduce stress on the mast partner and base
> from sloppy seas!?
>
> Todd
>
>
>
> --- In bolger@y..., "pvanderwaart" <pvanderw@o...> wrote:
> >
> > > How much of the force on a mast,
> > > even when close hauled, is pulling directly back on the mast?
> >
> > The idea of the sail plan is to produce force going forward, not
> > backward.
> >
> > Seriously, when close-hauled most of the force is to the side, and
> > some should be forward. The top of the mast is pulled back by the
> > force through the peak halyard to the gaff, down the leech and
> > through the sheets. The magnitude of this force can be judged from
> > the fact that you can trim the sheet in more or less easily without
> > the full weight/strength of a teenager.
> >
> > In general, it's easy to overestimate the forces and weights
> involved
> > with small boats. They should all be in scale with the weight of
> the
> > boat - half a ton.
> >
> > Peter
>
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - add your comments at the TOP and SIGN your posts and <snip> away
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/
>
>
>
> Even for the micro mast and its sprit I was thinging carbon fiberbase
> which I have plenty of. To reduce stress on the mast partner and
> from sloppy seas!?I was thinking of carbon in spars for a variety of reasons also. If
I went that route, I would eliminate the tabernacle altogether. I
know of a number of designs that use carbon spars in the small boat
range, and the resulting spars are reasonably easily hoisted by
hand. This would be superior to my way of thinking, unless you
expect to have to dip frequently to bridges or something.
If you intend to add carbon to a wood spar for reinforcement,
consider adding it inside the tube rather than outside. Outside it
will take all the load onto itself, and as a result the wood inside
will be just a heavy plug. Worse, if you are counting on that wood
for strength, you may end up with a catastrophic failure.
At one time I used to install wind monitoring equipment on 10 meter
masts that pivoted on tabernacles. We used channel iron for the cross
pieces at the base of the mast. We only had one bolt on each end and
one end had the bolt hole slotted, so that bolt only had to be
loosened and the cross-piece could be swung up out of the way. On a
small boat I would guess that aluminum channel would work. Most of
the forces while sailing are on the mast pivot bolt are they not?
Nels
masts that pivoted on tabernacles. We used channel iron for the cross
pieces at the base of the mast. We only had one bolt on each end and
one end had the bolt hole slotted, so that bolt only had to be
loosened and the cross-piece could be swung up out of the way. On a
small boat I would guess that aluminum channel would work. Most of
the forces while sailing are on the mast pivot bolt are they not?
Nels
--- In bolger@y..., "Richard Spelling" <richard@c...> wrote:
> Put the plate on the tabernacle to hold the mast up on the CLC
today. The
> plans mention in passing "turnbuckle holddown" setup.
>
mast was bending quite a bit more than, have a
Okay so for the same gaff rig and forces put on the tabernacle, would
it ease the stress on the tabenacle if you could lighten the spars by
half the weight or even more? Would it ease the forces created in a
sloppy sea? Or is the weight needed in all the spars?
Even for the micro mast and its sprit I was thinging carbon fiber
which I have plenty of. To reduce stress on the mast partner and base
from sloppy seas!?
Todd
it ease the stress on the tabenacle if you could lighten the spars by
half the weight or even more? Would it ease the forces created in a
sloppy sea? Or is the weight needed in all the spars?
Even for the micro mast and its sprit I was thinging carbon fiber
which I have plenty of. To reduce stress on the mast partner and base
from sloppy seas!?
Todd
--- In bolger@y..., "pvanderwaart" <pvanderw@o...> wrote:
>
> > How much of the force on a mast,
> > even when close hauled, is pulling directly back on the mast?
>
> The idea of the sail plan is to produce force going forward, not
> backward.
>
> Seriously, when close-hauled most of the force is to the side, and
> some should be forward. The top of the mast is pulled back by the
> force through the peak halyard to the gaff, down the leech and
> through the sheets. The magnitude of this force can be judged from
> the fact that you can trim the sheet in more or less easily without
> the full weight/strength of a teenager.
>
> In general, it's easy to overestimate the forces and weights
involved
> with small boats. They should all be in scale with the weight of
the
> boat - half a ton.
>
> Peter
Richard,
If I understand your test, it sounds like you are putting a bending
moment on the plate and that causes it to flex. How about instead of
getting thicker steel, using a piece of SS channel (u-shaped)or an
angle (L-shaped). These would be many times more rigid in bending
for the same thickness of material.
Alisa (AS-29) has a big SS channel for her gooseneck. That is a
different piece than what you are talking about, but it adds a lot of
strength and rigidity to the tabernacle assembly.
I also agree that there isn't normally significant backward force on
the mast, but you might have some significant dynamic backward loads
when that big pole and sail thrashes around in heavy chop.
Frank
Wilmington, DE
If I understand your test, it sounds like you are putting a bending
moment on the plate and that causes it to flex. How about instead of
getting thicker steel, using a piece of SS channel (u-shaped)or an
angle (L-shaped). These would be many times more rigid in bending
for the same thickness of material.
Alisa (AS-29) has a big SS channel for her gooseneck. That is a
different piece than what you are talking about, but it adds a lot of
strength and rigidity to the tabernacle assembly.
I also agree that there isn't normally significant backward force on
the mast, but you might have some significant dynamic backward loads
when that big pole and sail thrashes around in heavy chop.
Frank
Wilmington, DE
--- In bolger@y..., "Richard Spelling" <richard@c...> wrote:
> Put the plate on the tabernacle to hold the mast up on the CLC
today. The
> plans mention in passing "turnbuckle holddown" setup.
>
> Ran two pieces of 3/8" all thread through the tabernacle, 1 inch in
from the
> outside edges, at the height of the bottom of the mast. On the back
I have
> 1-1/2" fender washers to spread the load to the wood. On the front,
have a
> 1/4" thick, 2" wide piece of stainless steel spanning the full
width of the
> tabernacle. Distance between bolts is about 8 inches.
>
> Seems pretty solid. However, tying a long rope to the top of the
mast and
> having a 150lb teenager pull backwards on it as hard as he could
there is
> significant flex in the 2" steel plate. Maybe 3/16" or even almost
1/4" flex
> out in the center. (course, the mast was bending quite a bit more
than
> that...)
>
> This is bugging me. I'm toying with either using a thicker piece of
steel,
> or moving the bolts closer together, or something.
>
> Not sure that this is a valid test, though. How much of the force
on a mast,
> even when close hauled, is pulling directly back on the mast?
>
> Any feedback, engineering suggestions, comments, flames, rants, etc
are
> welcome!
>
> Should I run a forstay as insurance? Move the bolts closer
together? Use a
> thicker (or wider) piece of steel? Not worry about it and move on?
>
> Help!
>
> - Chebacco Richard
Hi Richard
It seems to me that the only 2 forces which would tend to pull your mast aft would be: 1. Steady, the
weight of the rig - the sail, boom and its rigging, and, 2. Transients having to do the weight of
everything resisting as the hull pitches forward over the top of a wave. A backstay, as opposed to a
headstay, might be the more important item.
The sail itself does its work by generating a force at right angles to the wind blowing by the boat.
That translates in part to a force forward which makes the boat go and in part to the side which
makes the boat want to slide off to leeward. On a beam reach, of course, both those forces are in the
forward direction, which is why, generally, that is the fastest point of sail.
So if the tabernacle rig is strong enough to keep the mast from falling forward under the press of
sail and upright under the momentum of the whole thing in a sloppy sea that's all it needs.
Jim
Richard Spelling wrote:
It seems to me that the only 2 forces which would tend to pull your mast aft would be: 1. Steady, the
weight of the rig - the sail, boom and its rigging, and, 2. Transients having to do the weight of
everything resisting as the hull pitches forward over the top of a wave. A backstay, as opposed to a
headstay, might be the more important item.
The sail itself does its work by generating a force at right angles to the wind blowing by the boat.
That translates in part to a force forward which makes the boat go and in part to the side which
makes the boat want to slide off to leeward. On a beam reach, of course, both those forces are in the
forward direction, which is why, generally, that is the fastest point of sail.
So if the tabernacle rig is strong enough to keep the mast from falling forward under the press of
sail and upright under the momentum of the whole thing in a sloppy sea that's all it needs.
Jim
Richard Spelling wrote:
> Put the plate on the tabernacle to hold the mast up on the CLC today. The
> plans mention in passing "turnbuckle holddown" setup.
>
> Ran two pieces of 3/8" all thread through the tabernacle, 1 inch in from the
> outside edges, at the height of the bottom of the mast. On the back I have
> 1-1/2" fender washers to spread the load to the wood. On the front, have a
> 1/4" thick, 2" wide piece of stainless steel spanning the full width of the
> tabernacle. Distance between bolts is about 8 inches.
>
> Seems pretty solid. However, tying a long rope to the top of the mast and
> having a 150lb teenager pull backwards on it as hard as he could there is
> significant flex in the 2" steel plate. Maybe 3/16" or even almost 1/4" flex
> out in the center. (course, the mast was bending quite a bit more than
> that...)
>
> This is bugging me. I'm toying with either using a thicker piece of steel,
> or moving the bolts closer together, or something.
>
> Not sure that this is a valid test, though. How much of the force on a mast,
> even when close hauled, is pulling directly back on the mast?
>
> Any feedback, engineering suggestions, comments, flames, rants, etc are
> welcome!
>
> Should I run a forstay as insurance? Move the bolts closer together? Use a
> thicker (or wider) piece of steel? Not worry about it and move on?
>
> Help!
>
> - Chebacco Richard
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - add your comments at the TOP and SIGN your posts and <snip> away
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/
Don't know, it just bugs me. Seems it should be firmer. Then again, I'm
bugged by the trailer flexing when the boat it on it!
There might be some wear on the 3/8" all threads do the the movement
eventualy....
You are probably right, I'm just not used to seeing a big chunk of steel
bend like that.
bugged by the trailer flexing when the boat it on it!
There might be some wear on the 3/8" all threads do the the movement
eventualy....
You are probably right, I'm just not used to seeing a big chunk of steel
bend like that.
----- Original Message -----
From: "Chuck Leinweber" <chuck_dm@...>
To: <bolger@yahoogroups.com>
Sent: Wednesday, June 12, 2002 12:15 AM
Subject: Re: [bolger] Tabernacle mast holding plate sizing
> What's the problem with a little flexing, Richard? If the mast stays up,
that should be enough.
>
> Chuck
> there is
> significant flex in the 2" steel plate. Maybe 3/16" or even almost 1/4"
flex
> out in the center. (course, the mast was bending quite a bit more than
> that...)
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
>
> Bolger rules!!!
> - no cursing, flaming, trolling, spamming, or flogging dead horses
> - stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
> - add your comments at the TOP and SIGN your posts and <snip> away
> - To order plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA,
01930, Fax: (978) 282-1349
> - Unsubscribe:bolger-unsubscribe@yahoogroups.com
> - Open discussion:bolger_coffee_lounge-subscribe@yahoogroups.com
>
> Your use of Yahoo! Groups is subject tohttp://docs.yahoo.com/info/terms/
>
>
>
> How much of the force on a mast,The idea of the sail plan is to produce force going forward, not
> even when close hauled, is pulling directly back on the mast?
backward.
Seriously, when close-hauled most of the force is to the side, and
some should be forward. The top of the mast is pulled back by the
force through the peak halyard to the gaff, down the leech and
through the sheets. The magnitude of this force can be judged from
the fact that you can trim the sheet in more or less easily without
the full weight/strength of a teenager.
In general, it's easy to overestimate the forces and weights involved
with small boats. They should all be in scale with the weight of the
boat - half a ton.
Peter
What's the problem with a little flexing, Richard? If the mast stays up, that should be enough.
Chuck
there is
significant flex in the 2" steel plate. Maybe 3/16" or even almost 1/4" flex
out in the center. (course, the mast was bending quite a bit more than
that...)
[Non-text portions of this message have been removed]
Chuck
there is
significant flex in the 2" steel plate. Maybe 3/16" or even almost 1/4" flex
out in the center. (course, the mast was bending quite a bit more than
that...)
[Non-text portions of this message have been removed]
Put the plate on the tabernacle to hold the mast up on the CLC today. The
plans mention in passing "turnbuckle holddown" setup.
Ran two pieces of 3/8" all thread through the tabernacle, 1 inch in from the
outside edges, at the height of the bottom of the mast. On the back I have
1-1/2" fender washers to spread the load to the wood. On the front, have a
1/4" thick, 2" wide piece of stainless steel spanning the full width of the
tabernacle. Distance between bolts is about 8 inches.
Seems pretty solid. However, tying a long rope to the top of the mast and
having a 150lb teenager pull backwards on it as hard as he could there is
significant flex in the 2" steel plate. Maybe 3/16" or even almost 1/4" flex
out in the center. (course, the mast was bending quite a bit more than
that...)
This is bugging me. I'm toying with either using a thicker piece of steel,
or moving the bolts closer together, or something.
Not sure that this is a valid test, though. How much of the force on a mast,
even when close hauled, is pulling directly back on the mast?
Any feedback, engineering suggestions, comments, flames, rants, etc are
welcome!
Should I run a forstay as insurance? Move the bolts closer together? Use a
thicker (or wider) piece of steel? Not worry about it and move on?
Help!
- Chebacco Richard
plans mention in passing "turnbuckle holddown" setup.
Ran two pieces of 3/8" all thread through the tabernacle, 1 inch in from the
outside edges, at the height of the bottom of the mast. On the back I have
1-1/2" fender washers to spread the load to the wood. On the front, have a
1/4" thick, 2" wide piece of stainless steel spanning the full width of the
tabernacle. Distance between bolts is about 8 inches.
Seems pretty solid. However, tying a long rope to the top of the mast and
having a 150lb teenager pull backwards on it as hard as he could there is
significant flex in the 2" steel plate. Maybe 3/16" or even almost 1/4" flex
out in the center. (course, the mast was bending quite a bit more than
that...)
This is bugging me. I'm toying with either using a thicker piece of steel,
or moving the bolts closer together, or something.
Not sure that this is a valid test, though. How much of the force on a mast,
even when close hauled, is pulling directly back on the mast?
Any feedback, engineering suggestions, comments, flames, rants, etc are
welcome!
Should I run a forstay as insurance? Move the bolts closer together? Use a
thicker (or wider) piece of steel? Not worry about it and move on?
Help!
- Chebacco Richard