Re: [bolger] Re: Birdsmouth masts & spars
> No, but it's almost impossible to predict the direction of the stress, soI was trying to speculate about the asymetry for Centenial II,
> circular is a good guess (and strong).
>
> Roger
and the best I can guess is that Bolger wanted flex
in the fore and aft direction, but not athwartships,
probably for the set of the sprit sails? [So that you can
flatten/depower the sail by cinching up on the snotters?]
No, but it's almost impossible to predict the direction of the stress, so
circular is a good guess (and strong).
Roger
derbyrm@...
http://derbyrm.mystarband.net/default.htm
circular is a good guess (and strong).
Roger
derbyrm@...
http://derbyrm.mystarband.net/default.htm
----- Original Message -----
From: "Bruce Hallman" <bruce@...>
> Why are masts traditionally a circle?
> I don't think masts are circular because
> the stresses are equal in 360 degrees.
> PCB because it is "not simple." LFH because there weren'tYou are probably right. Bolger and Buehler are just a likely
> good epoxy glues then. ????
> Roger
to use a 'grown stick'.
LFH, and Bolger [with Centenial II (and others?)] sometimes
used asymetrical shapes. Why are masts traditionally
a circle. First, because trees are circular? Second, so gaff
jaws can rotate easier? I don't think masts are circular because
the stress are equal in 360 degrees.
PCB because it is "not simple." LFH because there weren't good epoxy glues
then. ????
The system is described in Hassler & McLeod's "Junk Rig" (sic) under the
title of the Noble System. Apparently it was common in the non-nautical
world for making columns for anti-bellum mansions et. al.
Roger
derbyrm@...
http://derbyrm.mystarband.net/default.htm
then. ????
The system is described in Hassler & McLeod's "Junk Rig" (sic) under the
title of the Noble System. Apparently it was common in the non-nautical
world for making columns for anti-bellum mansions et. al.
Roger
derbyrm@...
http://derbyrm.mystarband.net/default.htm
----- Original Message -----
From: "Bruce Hallman" <bruce@...>
I am curious why, neither Bolger or L.F. Herreshoff,
advocate the use of birdsmouth masts?
[At least that I recall.]
> birdsmouth mastsI am curious why, neither Bolger or L.F. Herreshoff,
advocate the use of birdsmouth masts?
[At least that I recall.]
--- Inbolger@yahoogroups.com, "Thierry" <southcoveemail@y...> wrote:
boat,
Cheers,
John Mann
> Thanks to all for the advice on scarphing. I would like to build atabernacle. Does anyone have some pics or designs for micro or other
boat,
Cheers,
John Mann
> I have built a 40' hollow box mast 5"x7" with scarphes to make the 4
> staves (is that the right word?) for a marconi cutter. Everything was
> glued with epoxy. It takes time to make the scarphes right and to
> prepare everything especially for the first time. I had 80 home made
> mast clamps and a 40' long wall with a great number of wedges. For a
> mast I would always use 1:12 scarphes even with epoxy.
> I built this to replace a mast that had been built out of staggered
> and butted 2"x4"s on a 6"x6" section and then covered with glass and
> epoxy. Everything was falling apart after a few years of weather
> exposure.
> Don't use anything thicker than 11/2" at the most. Don't try to
> encapsulate, it will fail in the real world.
>
> I built my next mast (8 years later for a different boat) from a
> 36'long glulam beam 7"x7" in cross section. It was cheap et very
> quick. I tapered and shaped the square beam into a round section
> (gaff rig) in a few days. The glulam comes with finger-jointed
> laminated staves and I think it is stronger than a solid mast. The
> idea of using a glulam came from one of the designer of Prada who
> happened to race in the same club (from high tech to low tech). The
> advantage of the glulam beam is that you can order just the length
> and section you need. The beams are made for the building industry in
> factories under controlled conditions with a tight control of quality.
> The mast is now 4 years old, was only coated with oil and is in very
> good condition.
>
> Thierry
I have built a 40' hollow box mast 5"x7" with scarphes to make the 4
staves (is that the right word?) for a marconi cutter. Everything was
glued with epoxy. It takes time to make the scarphes right and to
prepare everything especially for the first time. I had 80 home made
mast clamps and a 40' long wall with a great number of wedges. For a
mast I would always use 1:12 scarphes even with epoxy.
I built this to replace a mast that had been built out of staggered
and butted 2"x4"s on a 6"x6" section and then covered with glass and
epoxy. Everything was falling apart after a few years of weather
exposure.
Don't use anything thicker than 11/2" at the most. Don't try to
encapsulate, it will fail in the real world.
I built my next mast (8 years later for a different boat) from a
36'long glulam beam 7"x7" in cross section. It was cheap et very
quick. I tapered and shaped the square beam into a round section
(gaff rig) in a few days. The glulam comes with finger-jointed
laminated staves and I think it is stronger than a solid mast. The
idea of using a glulam came from one of the designer of Prada who
happened to race in the same club (from high tech to low tech). The
advantage of the glulam beam is that you can order just the length
and section you need. The beams are made for the building industry in
factories under controlled conditions with a tight control of quality.
The mast is now 4 years old, was only coated with oil and is in very
good condition.
Thierry
staves (is that the right word?) for a marconi cutter. Everything was
glued with epoxy. It takes time to make the scarphes right and to
prepare everything especially for the first time. I had 80 home made
mast clamps and a 40' long wall with a great number of wedges. For a
mast I would always use 1:12 scarphes even with epoxy.
I built this to replace a mast that had been built out of staggered
and butted 2"x4"s on a 6"x6" section and then covered with glass and
epoxy. Everything was falling apart after a few years of weather
exposure.
Don't use anything thicker than 11/2" at the most. Don't try to
encapsulate, it will fail in the real world.
I built my next mast (8 years later for a different boat) from a
36'long glulam beam 7"x7" in cross section. It was cheap et very
quick. I tapered and shaped the square beam into a round section
(gaff rig) in a few days. The glulam comes with finger-jointed
laminated staves and I think it is stronger than a solid mast. The
idea of using a glulam came from one of the designer of Prada who
happened to race in the same club (from high tech to low tech). The
advantage of the glulam beam is that you can order just the length
and section you need. The beams are made for the building industry in
factories under controlled conditions with a tight control of quality.
The mast is now 4 years old, was only coated with oil and is in very
good condition.
Thierry
"...You still have to scarf the sticks..."
Everybody does. I've done so myself on every birdsmouth spar I've built.
Each time, I think to myself that the scarfs are probably unnecessary. The
sticks are self aligning and the points where the 'sticks' meet are
supported in position by the construction method. If the points at which the
sticks met were scattered more or less evenly along the length of the spar I
suspect that the whole thing could serve very satisfactorily with the ends
merely butted, and the goop in the butt joints serving as caulk rather than
adhesive. Inelegant perhaps, but a marked saving in handwork. The 7/8ths
strength could be factored out by a infitesimally small increase in OD. One
of these days I'll try it and see. Done that way a spar becomes a trivial
construction; the scarfing [while not hard to cut and jig] is still the most
complex part of a Birds Mouth build.
cheers
Derek
Everybody does. I've done so myself on every birdsmouth spar I've built.
Each time, I think to myself that the scarfs are probably unnecessary. The
sticks are self aligning and the points where the 'sticks' meet are
supported in position by the construction method. If the points at which the
sticks met were scattered more or less evenly along the length of the spar I
suspect that the whole thing could serve very satisfactorily with the ends
merely butted, and the goop in the butt joints serving as caulk rather than
adhesive. Inelegant perhaps, but a marked saving in handwork. The 7/8ths
strength could be factored out by a infitesimally small increase in OD. One
of these days I'll try it and see. Done that way a spar becomes a trivial
construction; the scarfing [while not hard to cut and jig] is still the most
complex part of a Birds Mouth build.
cheers
Derek
Two great birdsmouth calculators that you can download and run on your
computer:
http://www.carlsondesign.com/
(Scroll down about 7/8s of the page to "Shareware for Boat Design"
section.) Loads of fun!
All best,
Garth
P.S. I just glued up the staves for my 16' mizzenmast (3" diameter)
and 19' mainmast (5" diameter). Used 150 lb.-test nylon twine to pull
tight and wrap around the assembled staves. Worked great, like 200
hose clamps. Much planing and shaping to do now.
computer:
http://www.carlsondesign.com/
(Scroll down about 7/8s of the page to "Shareware for Boat Design"
section.) Loads of fun!
All best,
Garth
P.S. I just glued up the staves for my 16' mizzenmast (3" diameter)
and 19' mainmast (5" diameter). Used 150 lb.-test nylon twine to pull
tight and wrap around the assembled staves. Worked great, like 200
hose clamps. Much planing and shaping to do now.
--- Inbolger@yahoogroups.com, "Gabriel K. McAtee" <gmcatee@s...> wrote:
> I can forward information on this to the group if people are
interested. I
> had a wonderful email conversation going on with Gaétan Jetté (the
guy who
> wrote the DuckWorks article) and he sent me a Excel spreadsheet based
> calculator which calculates the cut angles, diameters, etc...
>
> --Gabe
>
I can forward information on this to the group if people are interested. I
had a wonderful email conversation going on with Gaétan Jetté (the guy who
wrote the DuckWorks article) and he sent me a Excel spreadsheet based
calculator which calculates the cut angles, diameters, etc...
--Gabe
-----Original Message-----
From: Derek Waters [mailto:dgw@...]
Sent: Tuesday, February 08, 2005 11:49 AM
To:bolger@yahoogroups.com
Subject: Re: [bolger] Tips on Scarphing
If the quality of the available lumber is not on your side, you could always
consider a 'Bird's Mouth' spar. Easily built from sticks, they have much to
recommend them. Chuck at DuckWorks has run several informative articles on
the subject, and there are other sources on the web if you 'google' for
them.
cheers
Derek
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had a wonderful email conversation going on with Gaétan Jetté (the guy who
wrote the DuckWorks article) and he sent me a Excel spreadsheet based
calculator which calculates the cut angles, diameters, etc...
--Gabe
-----Original Message-----
From: Derek Waters [mailto:dgw@...]
Sent: Tuesday, February 08, 2005 11:49 AM
To:bolger@yahoogroups.com
Subject: Re: [bolger] Tips on Scarphing
If the quality of the available lumber is not on your side, you could always
consider a 'Bird's Mouth' spar. Easily built from sticks, they have much to
recommend them. Chuck at DuckWorks has run several informative articles on
the subject, and there are other sources on the web if you 'google' for
them.
cheers
Derek
------------------------ Yahoo! Groups Sponsor --------------------~--> Meet
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bid on the Lincoln Fry prop charity auction.
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--------------------------------------------------------------------~->
Bolger rules!!!
- no cursing, flaming, trolling, spamming, or flogging dead horses
- stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
- Pls add your comments at the TOP, SIGN your posts, and snip away
- Plans: Mr. Philip C. Bolger, P.O. Box 1209, Gloucester, MA, 01930, Fax:
(978) 282-1349
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Yahoo! Groups Links
Back in the bad old days when glues were weak and demanded perfect fits and
heavy pressure, making a scarf called for real craftsmanship. Now, with
thickened epoxy which does not want a tight fit and needs only enough
clamping to hold it in position, they're easy. By scarfing and graving one
can take a collection of big box lumber and make it whole.
Skin the area with fiberglass reinforced epoxy and it's better than whole.
Roger
derbyrm@...
http://derbyrm.mystarband.net/default.htm
heavy pressure, making a scarf called for real craftsmanship. Now, with
thickened epoxy which does not want a tight fit and needs only enough
clamping to hold it in position, they're easy. By scarfing and graving one
can take a collection of big box lumber and make it whole.
Skin the area with fiberglass reinforced epoxy and it's better than whole.
Roger
derbyrm@...
http://derbyrm.mystarband.net/default.htm
----- Original Message -----
From: "Bruce Hallman" <bruce@...>
> consider a 'Bird's Mouth' spar. Easily built from sticks
> Derek
You still have to scarf the sticks, correct?
> consider a 'Bird's Mouth' spar. Easily built from sticksYou still have to scarf the sticks, correct?
> Derek
If the quality of the available lumber is not on your side, you could always
consider a 'Bird's Mouth' spar. Easily built from sticks, they have much to
recommend them. Chuck at DuckWorks has run several informative articles on
the subject, and there are other sources on the web if you 'google' for
them.
cheers
Derek
consider a 'Bird's Mouth' spar. Easily built from sticks, they have much to
recommend them. Chuck at DuckWorks has run several informative articles on
the subject, and there are other sources on the web if you 'google' for
them.
cheers
Derek
I once built a mast from smaller pieces, 3/4" thick by 3" or 4" wide
and about six feet long, making sure the individual scarfs were
staggered. The scarfing was easier on these smaller boards, and
epoxying and clamping them together yielded a mast of excellent strength.
TomP
and about six feet long, making sure the individual scarfs were
staggered. The scarfing was easier on these smaller boards, and
epoxying and clamping them together yielded a mast of excellent strength.
TomP
--- Inbolger@yahoogroups.com, "mannthree" <johnmann@i...> wrote:
>
> If I have to build a new mast, then the maximum length timber I can
> get is 6 metres (about 19.5') and 90mm x 90mm (3.5" square). I will
> have to scarph the difference. I've heard that at least a 12:1 scarph
> is required. Given that the thickness is 3.5", does that mean the
> length of the scarph should be about 42"? Also what way should the
> "edge" of the scarph face, port/starboard or stem/stern? By the
> "edge" of the scarph I mean that by looking at the joined timber
> pieces, the edge-join looks like a ramp,
>
> Regards,
>
> John Mann
> I've heard that at least a 12:1 scarph is required.I was just re-reading the plans for Micro and in it
Phil Bolger states that the mast scarf(s) should
be a minimum of 7:1.
Assuming the scarf is nicely done, it shouldn't matter which way it faces.
For underwater scarfs the received wisdom is that the external feather edge faces aft, so it's less likely to start 'peeling' back as the water rushes by. With modern epoxy glues, though, that's not really a problem.
I've never used more than an 8:1 scarf, and it's never failed on me yet.
Still, for a mast I'd be inclined to make it from two 2x4s glued together, rather than a single piece. They can be scarfed at separate places so the scarf in one part is backed up by an unscarfed bit in the other part. By aligning the grain properly, warping should be pretty much eliminated. Dynamite Payson describes mast making in New Instant Boats.
Bill
For underwater scarfs the received wisdom is that the external feather edge faces aft, so it's less likely to start 'peeling' back as the water rushes by. With modern epoxy glues, though, that's not really a problem.
I've never used more than an 8:1 scarf, and it's never failed on me yet.
Still, for a mast I'd be inclined to make it from two 2x4s glued together, rather than a single piece. They can be scarfed at separate places so the scarf in one part is backed up by an unscarfed bit in the other part. By aligning the grain properly, warping should be pretty much eliminated. Dynamite Payson describes mast making in New Instant Boats.
Bill
----- Original Message -----
From: mannthree
To:bolger@yahoogroups.com
Sent: Tuesday, February 08, 2005 8:48 AM
Subject: [bolger] Tips on Scarphing
If I have to build a new mast, then the maximum length timber I can
get is 6 metres (about 19.5') and 90mm x 90mm (3.5" square). I will
have to scarph the difference. I've heard that at least a 12:1 scarph
is required. Given that the thickness is 3.5", does that mean the
length of the scarph should be about 42"? Also what way should the
"edge" of the scarph face, port/starboard or stem/stern? By the
"edge" of the scarph I mean that by looking at the joined timber
pieces, the edge-join looks like a ramp,
Regards,
John Mann
Bolger rules!!!
- no cursing, flaming, trolling, spamming, or flogging dead horses
- stay on topic, stay on thread, punctuate, no 'Ed, thanks, Fred' posts
- Pls add your comments at the TOP, SIGN your posts, and snip away
- 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
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[Non-text portions of this message have been removed]
If I have to build a new mast, then the maximum length timber I can
get is 6 metres (about 19.5') and 90mm x 90mm (3.5" square). I will
have to scarph the difference. I've heard that at least a 12:1 scarph
is required. Given that the thickness is 3.5", does that mean the
length of the scarph should be about 42"? Also what way should the
"edge" of the scarph face, port/starboard or stem/stern? By the
"edge" of the scarph I mean that by looking at the joined timber
pieces, the edge-join looks like a ramp,
Regards,
John Mann
get is 6 metres (about 19.5') and 90mm x 90mm (3.5" square). I will
have to scarph the difference. I've heard that at least a 12:1 scarph
is required. Given that the thickness is 3.5", does that mean the
length of the scarph should be about 42"? Also what way should the
"edge" of the scarph face, port/starboard or stem/stern? By the
"edge" of the scarph I mean that by looking at the joined timber
pieces, the edge-join looks like a ramp,
Regards,
John Mann