RE: [bolger] Making a hollow mast ?
I think its at www.CarlsonDesign.com
Bill
-----Original Message-----
From: James Fuller [mailto:james@...]
Sent: Thursday, December 27, 2001 6:48 PM
To: bolger@yahoogroups.com
Subject: Re: [bolger] Making a hollow mast ?
Look at this site. Good article on making a hollow mast.
There is a free program out there for calculating wood
sizes also. I can't remember where I found it. I'll look
tonight and post the address.
http://users2.ev1.net/~fshagan/bm.htm
James Fuller
Bill
-----Original Message-----
From: James Fuller [mailto:james@...]
Sent: Thursday, December 27, 2001 6:48 PM
To: bolger@yahoogroups.com
Subject: Re: [bolger] Making a hollow mast ?
Look at this site. Good article on making a hollow mast.
There is a free program out there for calculating wood
sizes also. I can't remember where I found it. I'll look
tonight and post the address.
http://users2.ev1.net/~fshagan/bm.htm
James Fuller
----- Original Message -----
From: "Harry W. James" <welshman@...>
To: <bolger@yahoogroups.com>
Sent: Thursday, December 27, 2001 2:37 PM
Subject: Re: [bolger] Making a hollow mast ?
> Here is a copy of what John (last name escapes me, I always think of
him
> as John Boatguy) wrote me. John wrote an extensive article for
> Boatbuilder Magazine on birdsmouth masts.
>
> HJ
>
> The numbers for birdsmouth are posted on the Bolger message board in
the
> Files under 'How To tips'.
>
> You can go for a 20% of mast diameter thickness, as I did, and get a
> mast
> slightly lighter, but possibly not quite as strong as, a solid stick,
> depending on stock. (Bolger calls for a 2" stick if it is to be made
> round).
> I haven't had any trouble with mine, but I would still recommend that
> you
> consider going for a 15% of diameter wall thickness, and then up the
> overall
> diameter by 10%, to 2.2". That works out to .88" width (7/8"), by
.33"
> (11/32) thickness for each stave, for an eight stave birdsmouth mast.
> You'll
> get a thinner wall for a lighter mast, with just as much strength as a
> solid
> 3" stick. And I do think the lighter mast makes a difference in
> Cartopper
> with its relatively narrow bottom.
>
> If you do opt for a 15% wall, by all means build a plug to extend up
> past any
> mast base fittings, cleats and whatnot, you may want to screw on. The
> weight
> is minimal, and low, and won't make the a difference. Make the plug
> birdsmouth style, from staves longer than you need the plug to be.
Then
> taper the extra length of the staves--but from the birdsmouth
> face!--right
> down to a point. Don't taper the plug itself as you put it together.
> The
> tapered staves will stand straight up like little pointy fingers,
> dissipating
> the mast's cross sectional area slowly.
>
> To be honest, in such a small mast you may not need to worry about
> stress
> concentration, but why take a chance? If it's an eight stave mast,
the
> inside comes out octagonal, and an eight stave plug, properly sized,
> will fit
> in like a glove after a few swipes with a plane. Measure across the
> inside
> of your test fit mast, and divide by 2.4 to find the stave width for
> your
> eight stave plug. Build the plug before gluing up the mast, then glue
> up the
> plug, fit it into your test fit mast, mark everything so it goes
> together the
> same way, then glue up the mast, with the plug inside, in one step.
> With
> glue slathered all over the outside of the plug, and using the plug as
a
> 'rolling pin' to roll up your staves around, mast glue up is an easy,
> one man
> operation. If you're using epoxy (by all means use epoxy, the slow
set
> up,
> and the fact that it's slippery when wet, will make glue up and
> straightening
> much easier) then all you need to do is spiral up a wrap of hand
tight,
> waxed
> twine around the mast as a clamp. The whole thing will take ten
> minutes.
> Make sure the mast is straight!
>
> Good luck!
>
> John
>
> bitme1234 wrote:
> >
> > How much larger should it be than a solid mast in diameter?
> > Say for a 16 foot mast.
> >
> > Todd
> >
>
>
> 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 to
http://docs.yahoo.com/info/terms/
>
>
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Bolger rules!!!
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- 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 to the Yahoo! Terms of Service
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[Non-text portions of this message have been removed]
Look at this site. Good article on making a hollow mast.
There is a free program out there for calculating wood
sizes also. I can't remember where I found it. I'll look
tonight and post the address.
http://users2.ev1.net/~fshagan/bm.htm
James Fuller
There is a free program out there for calculating wood
sizes also. I can't remember where I found it. I'll look
tonight and post the address.
http://users2.ev1.net/~fshagan/bm.htm
James Fuller
----- Original Message -----
From: "Harry W. James" <welshman@...>
To: <bolger@yahoogroups.com>
Sent: Thursday, December 27, 2001 2:37 PM
Subject: Re: [bolger] Making a hollow mast ?
> Here is a copy of what John (last name escapes me, I always think of him
> as John Boatguy) wrote me. John wrote an extensive article for
> Boatbuilder Magazine on birdsmouth masts.
>
> HJ
>
> The numbers for birdsmouth are posted on the Bolger message board in the
> Files under 'How To tips'.
>
> You can go for a 20% of mast diameter thickness, as I did, and get a
> mast
> slightly lighter, but possibly not quite as strong as, a solid stick,
> depending on stock. (Bolger calls for a 2" stick if it is to be made
> round).
> I haven't had any trouble with mine, but I would still recommend that
> you
> consider going for a 15% of diameter wall thickness, and then up the
> overall
> diameter by 10%, to 2.2". That works out to .88" width (7/8"), by .33"
> (11/32) thickness for each stave, for an eight stave birdsmouth mast.
> You'll
> get a thinner wall for a lighter mast, with just as much strength as a
> solid
> 3" stick. And I do think the lighter mast makes a difference in
> Cartopper
> with its relatively narrow bottom.
>
> If you do opt for a 15% wall, by all means build a plug to extend up
> past any
> mast base fittings, cleats and whatnot, you may want to screw on. The
> weight
> is minimal, and low, and won't make the a difference. Make the plug
> birdsmouth style, from staves longer than you need the plug to be. Then
> taper the extra length of the staves--but from the birdsmouth
> face!--right
> down to a point. Don't taper the plug itself as you put it together.
> The
> tapered staves will stand straight up like little pointy fingers,
> dissipating
> the mast's cross sectional area slowly.
>
> To be honest, in such a small mast you may not need to worry about
> stress
> concentration, but why take a chance? If it's an eight stave mast, the
> inside comes out octagonal, and an eight stave plug, properly sized,
> will fit
> in like a glove after a few swipes with a plane. Measure across the
> inside
> of your test fit mast, and divide by 2.4 to find the stave width for
> your
> eight stave plug. Build the plug before gluing up the mast, then glue
> up the
> plug, fit it into your test fit mast, mark everything so it goes
> together the
> same way, then glue up the mast, with the plug inside, in one step.
> With
> glue slathered all over the outside of the plug, and using the plug as a
> 'rolling pin' to roll up your staves around, mast glue up is an easy,
> one man
> operation. If you're using epoxy (by all means use epoxy, the slow set
> up,
> and the fact that it's slippery when wet, will make glue up and
> straightening
> much easier) then all you need to do is spiral up a wrap of hand tight,
> waxed
> twine around the mast as a clamp. The whole thing will take ten
> minutes.
> Make sure the mast is straight!
>
> Good luck!
>
> John
>
> bitme1234 wrote:
> >
> > How much larger should it be than a solid mast in diameter?
> > Say for a 16 foot mast.
> >
> > Todd
> >
>
>
> 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/
>
>
Hi Todd, your question is a little like asking how far is up!
I've been looking through some of my boat design books and an answer
occurs in Skene's Elements of Yacht Design as revised by Francis
Kinney.
Mr Kinney states that "A hollow spar is roughly half the weight of a
solid one and, if given about a 10% increase in diameter or sectional
dimensions, is just as strong.". He continues with a description of an
example worked out by Mr Skene in which two short spars were worked
out for the same strength, 8500 pounds. The hollow mast had a 4"
outside diameter and 3" inside diameter. The solid spar was 3/8"
smaller in diameter. The hollow weighed 11 1/2#, the solid 21 1/2#
both had a design strength of 8500#. If you are really wanting to get
into this the book again is "Skene's Elements of Yacht Design" revised
and updated by Francis Kinney and published by Dodd, Mead. My edition
is 1962 but I know that the Yacht Design Institute used this
reference, but a newer edition, in their course 10 years or so ago.
Anything else you would like me to dig out of this jewel?
Bob Chamberland
I've been looking through some of my boat design books and an answer
occurs in Skene's Elements of Yacht Design as revised by Francis
Kinney.
Mr Kinney states that "A hollow spar is roughly half the weight of a
solid one and, if given about a 10% increase in diameter or sectional
dimensions, is just as strong.". He continues with a description of an
example worked out by Mr Skene in which two short spars were worked
out for the same strength, 8500 pounds. The hollow mast had a 4"
outside diameter and 3" inside diameter. The solid spar was 3/8"
smaller in diameter. The hollow weighed 11 1/2#, the solid 21 1/2#
both had a design strength of 8500#. If you are really wanting to get
into this the book again is "Skene's Elements of Yacht Design" revised
and updated by Francis Kinney and published by Dodd, Mead. My edition
is 1962 but I know that the Yacht Design Institute used this
reference, but a newer edition, in their course 10 years or so ago.
Anything else you would like me to dig out of this jewel?
Bob Chamberland
--- In bolger@y..., "bitme1234" <ktsrfer@m...> wrote:
> How much larger should it be than a solid mast in diameter?
> Say for a 16 foot mast.
>
> Todd
Here is a copy of what John (last name escapes me, I always think of him
as John Boatguy) wrote me. John wrote an extensive article for
Boatbuilder Magazine on birdsmouth masts.
HJ
The numbers for birdsmouth are posted on the Bolger message board in the
Files under 'How To tips'.
You can go for a 20% of mast diameter thickness, as I did, and get a
mast
slightly lighter, but possibly not quite as strong as, a solid stick,
depending on stock. (Bolger calls for a 2" stick if it is to be made
round).
I haven't had any trouble with mine, but I would still recommend that
you
consider going for a 15% of diameter wall thickness, and then up the
overall
diameter by 10%, to 2.2". That works out to .88" width (7/8"), by .33"
(11/32) thickness for each stave, for an eight stave birdsmouth mast.
You'll
get a thinner wall for a lighter mast, with just as much strength as a
solid
3" stick. And I do think the lighter mast makes a difference in
Cartopper
with its relatively narrow bottom.
If you do opt for a 15% wall, by all means build a plug to extend up
past any
mast base fittings, cleats and whatnot, you may want to screw on. The
weight
is minimal, and low, and won't make the a difference. Make the plug
birdsmouth style, from staves longer than you need the plug to be. Then
taper the extra length of the staves--but from the birdsmouth
face!--right
down to a point. Don't taper the plug itself as you put it together.
The
tapered staves will stand straight up like little pointy fingers,
dissipating
the mast's cross sectional area slowly.
To be honest, in such a small mast you may not need to worry about
stress
concentration, but why take a chance? If it's an eight stave mast, the
inside comes out octagonal, and an eight stave plug, properly sized,
will fit
in like a glove after a few swipes with a plane. Measure across the
inside
of your test fit mast, and divide by 2.4 to find the stave width for
your
eight stave plug. Build the plug before gluing up the mast, then glue
up the
plug, fit it into your test fit mast, mark everything so it goes
together the
same way, then glue up the mast, with the plug inside, in one step.
With
glue slathered all over the outside of the plug, and using the plug as a
'rolling pin' to roll up your staves around, mast glue up is an easy,
one man
operation. If you're using epoxy (by all means use epoxy, the slow set
up,
and the fact that it's slippery when wet, will make glue up and
straightening
much easier) then all you need to do is spiral up a wrap of hand tight,
waxed
twine around the mast as a clamp. The whole thing will take ten
minutes.
Make sure the mast is straight!
Good luck!
John
bitme1234 wrote:
as John Boatguy) wrote me. John wrote an extensive article for
Boatbuilder Magazine on birdsmouth masts.
HJ
The numbers for birdsmouth are posted on the Bolger message board in the
Files under 'How To tips'.
You can go for a 20% of mast diameter thickness, as I did, and get a
mast
slightly lighter, but possibly not quite as strong as, a solid stick,
depending on stock. (Bolger calls for a 2" stick if it is to be made
round).
I haven't had any trouble with mine, but I would still recommend that
you
consider going for a 15% of diameter wall thickness, and then up the
overall
diameter by 10%, to 2.2". That works out to .88" width (7/8"), by .33"
(11/32) thickness for each stave, for an eight stave birdsmouth mast.
You'll
get a thinner wall for a lighter mast, with just as much strength as a
solid
3" stick. And I do think the lighter mast makes a difference in
Cartopper
with its relatively narrow bottom.
If you do opt for a 15% wall, by all means build a plug to extend up
past any
mast base fittings, cleats and whatnot, you may want to screw on. The
weight
is minimal, and low, and won't make the a difference. Make the plug
birdsmouth style, from staves longer than you need the plug to be. Then
taper the extra length of the staves--but from the birdsmouth
face!--right
down to a point. Don't taper the plug itself as you put it together.
The
tapered staves will stand straight up like little pointy fingers,
dissipating
the mast's cross sectional area slowly.
To be honest, in such a small mast you may not need to worry about
stress
concentration, but why take a chance? If it's an eight stave mast, the
inside comes out octagonal, and an eight stave plug, properly sized,
will fit
in like a glove after a few swipes with a plane. Measure across the
inside
of your test fit mast, and divide by 2.4 to find the stave width for
your
eight stave plug. Build the plug before gluing up the mast, then glue
up the
plug, fit it into your test fit mast, mark everything so it goes
together the
same way, then glue up the mast, with the plug inside, in one step.
With
glue slathered all over the outside of the plug, and using the plug as a
'rolling pin' to roll up your staves around, mast glue up is an easy,
one man
operation. If you're using epoxy (by all means use epoxy, the slow set
up,
and the fact that it's slippery when wet, will make glue up and
straightening
much easier) then all you need to do is spiral up a wrap of hand tight,
waxed
twine around the mast as a clamp. The whole thing will take ten
minutes.
Make sure the mast is straight!
Good luck!
John
bitme1234 wrote:
>
> How much larger should it be than a solid mast in diameter?
> Say for a 16 foot mast.
>
> Todd
>
Hi Todd
I made two hollow square section mast for my schooner out of clear
douglas fir. I made them 3 inch per side and started a taper to 2
inch square at he tops. I made a 16 ft mast as the main mast and a
15 ft mast as the foremast. I used them unstayed and they were very
rugged. I hope this helps!
Steve Bosquette
I made two hollow square section mast for my schooner out of clear
douglas fir. I made them 3 inch per side and started a taper to 2
inch square at he tops. I made a 16 ft mast as the main mast and a
15 ft mast as the foremast. I used them unstayed and they were very
rugged. I hope this helps!
Steve Bosquette
--- In bolger@y..., "bitme1234" <ktsrfer@m...> wrote:
> How much larger should it be than a solid mast in diameter?
> Say for a 16 foot mast.
>
> Todd
How much larger should it be than a solid mast in diameter?
Say for a 16 foot mast.
Todd
Say for a 16 foot mast.
Todd