Re: [bolger] Re: Masts for the 59 sq ft spritsail
Birdsmouth and something over 30 lb.
On Fri, 19 Aug 2011 11:10:53 -0700, Nels wrote:
> For a view of Mark's JB Jr under full-throttle check the Michalak home
> page.
>
>http://groups.yahoo.com/group/Michalak/
>
> That is a birdsmouth mast of just over 20 lb I believe.
--
John (jkohnen@...)
I shall allow no man to belittle my soul by making me hate him.
(Booker T. Washington)
Definitely most interesting to see all the thoughts/comments.
Re snotter purchase:
On Oldshoe I use a 2 part purchase on the snotter, leading the snotter line from the mast, through the slit in the sprit boom, back to the single block and down. This gets the sail much tighter than I can with a straight pull.
Re sail shape:
I thought I'd go all the way and find out how the "official Bolger LOM" was shaped so ordered one from HH Payson & Co. (Now managed by Dennis Hansen).
The dacron sail arrived today and, despite being winter and months before I shall get sailing, I took it out of the sailbag and had a good look at the geometry.
I was surprised to find it was a crosscut sail cut with slight rounding in the foot.
However there is also:
- evident rounding up the luff
- very slight hollow in the leach
- definite shaping in the front third of the sail (belly), achieved I believe, by panel cutting (today's equivalent of broadseaming - the sail is cut on a plotter)
I will have to wait a few months to try it out, but was impressed to see the amount of belly in the sail - what we achieve in polytarp using darts prescribed by Michalak / Polysail.
Looking forward to see more thoughts on this subject.
David
Santiago, Chile
Re snotter purchase:
On Oldshoe I use a 2 part purchase on the snotter, leading the snotter line from the mast, through the slit in the sprit boom, back to the single block and down. This gets the sail much tighter than I can with a straight pull.
Re sail shape:
I thought I'd go all the way and find out how the "official Bolger LOM" was shaped so ordered one from HH Payson & Co. (Now managed by Dennis Hansen).
The dacron sail arrived today and, despite being winter and months before I shall get sailing, I took it out of the sailbag and had a good look at the geometry.
I was surprised to find it was a crosscut sail cut with slight rounding in the foot.
However there is also:
- evident rounding up the luff
- very slight hollow in the leach
- definite shaping in the front third of the sail (belly), achieved I believe, by panel cutting (today's equivalent of broadseaming - the sail is cut on a plotter)
I will have to wait a few months to try it out, but was impressed to see the amount of belly in the sail - what we achieve in polytarp using darts prescribed by Michalak / Polysail.
Looking forward to see more thoughts on this subject.
David
Santiago, Chile
Forgot I had Trilars plans!
http://www.duckworksbbs.com/plans/jim/trilars/index.htm
Same 59 sq ft LOM as Bolger drew but has 13/4' rounding on the foot,
31/4" rounding at the luff and 2" of hollow on the leech. The snotter
attached so the sprit boom is just a bit lower at the clew that at the
mast.
Also has a row of reef points at the level of the snotter.
Interesting, as it is newer design than Pencilbox.
Nels
http://www.duckworksbbs.com/plans/jim/trilars/index.htm
Same 59 sq ft LOM as Bolger drew but has 13/4' rounding on the foot,
31/4" rounding at the luff and 2" of hollow on the leech. The snotter
attached so the sprit boom is just a bit lower at the clew that at the
mast.
Also has a row of reef points at the level of the snotter.
Interesting, as it is newer design than Pencilbox.
Nels
--- Inbolger@yahoogroups.com, Mark Albanese <marka97203@...> wrote:
>
> Nels,
>
> He's done them both ways regarding the foot, but always with a
> curving luff to allow for mast bend. Pencilbox, an early work, looks
> like it uses the straight cut foot that comes from Bolger. Later
> boats with the LOM, I've got plans for Trilars and JB Jr., have the
> rounded foot.
>
>
>
>
>
> On Aug 22, 2011, at 9:55 AM, prairiedog2332 wrote:
>
> > After further study, it occurs to me that Michalak's sail shaping
> > instructions apply mostly to the Balance Lug, or sometimes gaff or
> > lateen, all having the foot attached to a boom. He liked these
> > sails as
> > the mast would be shorter than with a LOM with sprit boom. His
> > favorite
> > sail was the Bolger balance lug as supplied with Windsprint as most
of
> > his designs were about that size. He even changed his Birdwatcher
over
> > to a balance lug.
> >
> > But I have no plans that come with the LOM so not sure how he
> > instructed
> > that to be made.
> >
> > So he had some rounding at foot and head and some hollow in the
leech
> > and the luff dead straight.
> >
> > Nels
> >
> > --- Inbolger@yahoogroups.com, "David" dir_cobb@ wrote:
> > >
> > > Myles/Nels
> > >
> > > You have got me thinking on this one.
> > >
> > > I think the reason many people are relocating the snotter further
up
> > the mast may actually be because the sail they are using is not cut
as
> > Bolger prescribes for a leg o mutton but more like a loose footed
> > sail,
> > therefore requiring the clew to be bisected by the sprit.
> > >
> > > I have for some time had my doubts about the use in edge shaping
in
> > the foot of the leg o mutton sail as a means of adding belly as:
> > >
> > > (a) the edge is not held against a spar [or stretched tight by the
> > edge reinforcement (rope or tape)]
> > > (b) it contradicts Bolgers instructions on many of the plans
> > (e.g.Gypsy) "Foot of sail cut straight to take tension".
> > >
> > > It seems to me that the edge curve in the foot does not generate
> > shape
> > because the tarp (specially in low wind conditions) tends to take
the
> > tension rather than the edge rope. This may be because I use pretty
> > heavy polytarp.
> > >
> > > On the other hand, I have found that the edge shaping up the mast
of
> > my leg o muttons works perfectly because the excess fabric forms the
> > bulge required since the edge of the bulge is held all the way
> > along its
> > edge by the lacing.
> > >
> > > Regarding high wind conditions, my feeling is that a flexible mast
> > plays a very important role in the capacity to depower the sail by
> > tensioning the snotter.
> > >
> > > Look forward to other peoples thoughts.
> > >
> > > David
> > > Santiago, Chile
> > >
> > >
> > >
> > > --- Inbolger@yahoogroups.com, "Myles Swift" mswift@ wrote:
> > > >
> > > > David,
> > > >
> > > >
> > > >
> > > > Thanks for that. The automatic preventer aspect of the sprit
boom
> > sail is
> > > > certainly a winner. Just looking at sail shape I've been
> > tempted to
> > make
> > > > another, higher, snotter position for high wind. I got the sail
> > directly
> > > > from Dynamite so I'm sure it is cut as well is it can be.
> > > >
> > > >
> > > >
> > > > MylesJ
> > > >
> > >
> >
> >
>
Nels,
He's done them both ways regarding the foot, but always with a curving luff to allow for mast bend.Pencilbox, an early work, looks like it uses the straight cut foot that comes from Bolger. Later boats with the LOM, I've got plans for Trilars and JB Jr., have the rounded foot.
On Aug 22, 2011, at 9:55 AM, prairiedog2332 wrote:
After further study, it occurs to me that Michalak's sail shaping
instructions apply mostly to the Balance Lug, or sometimes gaff or
lateen, all having the foot attached to a boom. He liked these sails as
the mast would be shorter than with a LOM with sprit boom. His favorite
sail was the Bolger balance lug as supplied with Windsprint as most of
his designs were about that size. He even changed his Birdwatcher over
to a balance lug.
But I have no plans that come with the LOM so not sure how he instructed
that to be made.
So he had some rounding at foot and head and some hollow in the leech
and the luff dead straight.
Nels
--- Inbolger@yahoogroups.com, "David" <dir_cobb@...> wrote:
>
> Myles/Nels
>
> You have got me thinking on this one.
>
> I think the reason many people are relocating the snotter further up
the mast may actually be because the sail they are using is not cut as
Bolger prescribes for a leg o mutton but more like a loose footed sail,
therefore requiring the clew to be bisected by the sprit.
>
> I have for some time had my doubts about the use in edge shaping in
the foot of the leg o mutton sail as a means of adding belly as:
>
> (a) the edge is not held against a spar [or stretched tight by the
edge reinforcement (rope or tape)]
> (b) it contradicts Bolgers instructions on many of the plans
(e.g.Gypsy) "Foot of sail cut straight to take tension".
>
> It seems to me that the edge curve in the foot does not generate shape
because the tarp (specially in low wind conditions) tends to take the
tension rather than the edge rope. This may be because I use pretty
heavy polytarp.
>
> On the other hand, I have found that the edge shaping up the mast of
my leg o muttons works perfectly because the excess fabric forms the
bulge required since the edge of the bulge is held all the way along its
edge by the lacing.
>
> Regarding high wind conditions, my feeling is that a flexible mast
plays a very important role in the capacity to depower the sail by
tensioning the snotter.
>
> Look forward to other peoples thoughts.
>
> David
> Santiago, Chile
>
>
>
> --- Inbolger@yahoogroups.com, "Myles Swift" mswift@ wrote:
> >
> > David,
> >
> >
> >
> > Thanks for that. The automatic preventer aspect of the sprit boom
sail is
> > certainly a winner. Just looking at sail shape I've been tempted to
make
> > another, higher, snotter position for high wind. I got the sail
directly
> > from Dynamite so I'm sure it is cut as well is it can be.
> >
> >
> >
> > MylesJ
> >
>
After further study, it occurs to me that Michalak's sail shaping
instructions apply mostly to the Balance Lug, or sometimes gaff or
lateen, all having the foot attached to a boom. He liked these sails as
the mast would be shorter than with a LOM with sprit boom. His favorite
sail was the Bolger balance lug as supplied with Windsprint as most of
his designs were about that size. He even changed his Birdwatcher over
to a balance lug.
But I have no plans that come with the LOM so not sure how he instructed
that to be made.
So he had some rounding at foot and head and some hollow in the leech
and the luff dead straight.
Nels
instructions apply mostly to the Balance Lug, or sometimes gaff or
lateen, all having the foot attached to a boom. He liked these sails as
the mast would be shorter than with a LOM with sprit boom. His favorite
sail was the Bolger balance lug as supplied with Windsprint as most of
his designs were about that size. He even changed his Birdwatcher over
to a balance lug.
But I have no plans that come with the LOM so not sure how he instructed
that to be made.
So he had some rounding at foot and head and some hollow in the leech
and the luff dead straight.
Nels
--- Inbolger@yahoogroups.com, "David" <dir_cobb@...> wrote:
>
> Myles/Nels
>
> You have got me thinking on this one.
>
> I think the reason many people are relocating the snotter further up
the mast may actually be because the sail they are using is not cut as
Bolger prescribes for a leg o mutton but more like a loose footed sail,
therefore requiring the clew to be bisected by the sprit.
>
> I have for some time had my doubts about the use in edge shaping in
the foot of the leg o mutton sail as a means of adding belly as:
>
> (a) the edge is not held against a spar [or stretched tight by the
edge reinforcement (rope or tape)]
> (b) it contradicts Bolgers instructions on many of the plans
(e.g.Gypsy) "Foot of sail cut straight to take tension".
>
> It seems to me that the edge curve in the foot does not generate shape
because the tarp (specially in low wind conditions) tends to take the
tension rather than the edge rope. This may be because I use pretty
heavy polytarp.
>
> On the other hand, I have found that the edge shaping up the mast of
my leg o muttons works perfectly because the excess fabric forms the
bulge required since the edge of the bulge is held all the way along its
edge by the lacing.
>
> Regarding high wind conditions, my feeling is that a flexible mast
plays a very important role in the capacity to depower the sail by
tensioning the snotter.
>
> Look forward to other peoples thoughts.
>
> David
> Santiago, Chile
>
>
>
> --- Inbolger@yahoogroups.com, "Myles Swift" mswift@ wrote:
> >
> > David,
> >
> >
> >
> > Thanks for that. The automatic preventer aspect of the sprit boom
sail is
> > certainly a winner. Just looking at sail shape I've been tempted to
make
> > another, higher, snotter position for high wind. I got the sail
directly
> > from Dynamite so I'm sure it is cut as well is it can be.
> >
> >
> >
> > MylesJ
> >
>
That last pic (http://www.flickr.com/photos/oneillparker/3106029284/in/set-72157609176660131)is a good illustration of the advantage of the two part snotter system. Note the background boat, heeling to port, boom to starboard, clew lifted, leech opened. That boat is probably getting ready to roll back to starboard, then back to port, with the clew lifting, and dropping, back and forth,with the helmsman working the rudder to keep on course and avoid an unintentional jibe, a classic downwind roll situation which can get downright dangerous. I don't think he has a boom vang. Instead the lead of the sheet is supposed to act to keep the boom from lifting. That system doesn't work too well.
My boat (not to brag) is stable, level, on course and at speed, even if sailing by the lee. Note the leech is closed. The snotter uphaul has positioned the sprit boom relatively high on the mast, the snotter dowhaul has been hauled in tight putting high tension on the foot of the sail. No death roll happening here!
John O'Neill
My boat (not to brag) is stable, level, on course and at speed, even if sailing by the lee. Note the leech is closed. The snotter uphaul has positioned the sprit boom relatively high on the mast, the snotter dowhaul has been hauled in tight putting high tension on the foot of the sail. No death roll happening here!
John O'Neill
--- Inbolger@yahoogroups.com, "c.ruzer" <c.ruzer@...> wrote:
>
>
>
>
> Load distributions from clew (and tack). (It's been observed more than once that many sailmakers -- routine producers of conventional bermudan triangular foot-boomed-vanged mainsails, jib and other foresails, etc -- often don't understand the sharpie l-o-m sprit-boomed sail. They don't get the triangulated balance of forces (resultant sail force tension at the clew, sprit compression, sheet tension) that fixes the distal end of the sprit in three dimensional space from which the clew is anchored). An issue often associated with sprit issues located low in the sail is that they cut the sail too full, and too jib-like. They could read some of Bolger's observations on this, for a better perspective. I'm sure a qualified sailmaker would quickly understand and discern the different qualities needed to their usual three-cornered sails - they are already well versed in load pathways, stresses, etc.
>
>http://groups.yahoo.com/group/Michalak/note marked horizontal creasing between lower luff/tack and clew. The creasing indicates the load pathways(s), here the load is mostly concentrated and distributed horizontally through the lower part of the sail fabric rather than by the foot reinforcement (rope, tape, whatever).
>
>
>
>http://www.flickr.com/photos/oneillparker/3034245064/in/set-72157609176660131note fanning out of creasing angles at clew; not any marked horizontal creasing clew to tack/lower luff
>
>
>http://www.flickr.com/photos/oneillparker/3102304446/in/set-72157609176660131/note telltale streaming, note fanning out of creasing angles at tack.
>
>
>http://www.flickr.com/photos/oneillparker/3102304312/in/set-72157609176660131/lightly reaching, no obvious ceasing at tack at all.
>
>
>http://www.flickr.com/photos/oneillparker/3106029284/in/set-72157609176660131running, note lower telltale, note fanning out of creasing angles at clew
>
>
Load distributions from clew (and tack). (It's been observed more than once that many sailmakers -- routine producers of conventional bermudan triangular foot-boomed-vanged mainsails, jib and other foresails, etc -- often don't understand the sharpie l-o-m sprit-boomed sail. They don't get the triangulated balance of forces (resultant sail force tension at the clew, sprit compression, sheet tension) that fixes the distal end of the sprit in three dimensional space from which the clew is anchored). An issue often associated with sprit issues located low in the sail is that they cut the sail too full, and too jib-like. They could read some of Bolger's observations on this, for a better perspective. I'm sure a qualified sailmaker would quickly understand and discern the different qualities needed to their usual three-cornered sails - they are already well versed in load pathways, stresses, etc.
http://groups.yahoo.com/group/Michalak/note marked horizontal creasing between lower luff/tack and clew. The creasing indicates the load pathways(s), here the load is mostly concentrated and distributed horizontally through the lower part of the sail fabric rather than by the foot reinforcement (rope, tape, whatever).
http://www.flickr.com/photos/oneillparker/3034245064/in/set-72157609176660131note fanning out of creasing angles at clew; not any marked horizontal creasing clew to tack/lower luff
http://www.flickr.com/photos/oneillparker/3102304446/in/set-72157609176660131/note telltale streaming, note fanning out of creasing angles at tack.
http://www.flickr.com/photos/oneillparker/3102304312/in/set-72157609176660131/lightly reaching, no obvious ceasing at tack at all.
http://www.flickr.com/photos/oneillparker/3106029284/in/set-72157609176660131running, note lower telltale, note fanning out of creasing angles at clew
http://groups.yahoo.com/group/Michalak/note marked horizontal creasing between lower luff/tack and clew. The creasing indicates the load pathways(s), here the load is mostly concentrated and distributed horizontally through the lower part of the sail fabric rather than by the foot reinforcement (rope, tape, whatever).
http://www.flickr.com/photos/oneillparker/3034245064/in/set-72157609176660131note fanning out of creasing angles at clew; not any marked horizontal creasing clew to tack/lower luff
http://www.flickr.com/photos/oneillparker/3102304446/in/set-72157609176660131/note telltale streaming, note fanning out of creasing angles at tack.
http://www.flickr.com/photos/oneillparker/3102304312/in/set-72157609176660131/lightly reaching, no obvious ceasing at tack at all.
http://www.flickr.com/photos/oneillparker/3106029284/in/set-72157609176660131running, note lower telltale, note fanning out of creasing angles at clew
--- Inbolger@yahoogroups.com, Mark Albanese <marka97203@...> wrote:
>
> Guys,
>
> Jim Michalak finds:
> > My feeling is that the tension in the foot of these sails is so
> > high that the foot is going to straighten out due to the load no
> > matter how you shape it, so it ends up as if you had laced it to
>> a straight boom.
> >
> Still playing it safe, I've only been in winds mostly 5 - 10 mph, but
> it's hard to imagine getting enough tension on the foot to
> straighten it out completely. My snotter tackle is always right up
> against the mast already. The angle in the photo of John booming
> along seems to show it running straighter, but it looks to me like
> the bisecting approach can only give more tension above the sprit
> the below.
>
> As far as the straight foot having a vang effect to keep the boom
> down, again in mild winds, with a rounded one I haven't had that
> problem.
> Mark
>
> On Aug 19, 2011, at 10:10 AM, Myles Swift wrote:
> >
> > Mark,
> >
> > So I guess the question is loose/rounded foot with bisecting sprit
> > versus taut foot with level sprit? I know I can ghost better than
> > most other small boats, sitting on the lee side to keep the sail
> > out. I don't think that would work as well with the bi-secting
> > approach given that the snotter is slacked in that condition.
> > With the Coots rafted up I have sailed around the group in light
> > air within an arm's length of their boats.
> > For a view of Mark's JB Jr under full-throttle check the Michalak
> > home page.
> >
> >http://groups.yahoo.com/group/Michalak/
> >
> > That is a birdsmouth mast of just over 20 lb I believe.
--- Inbolger@yahoogroups.com, Mark Albanese <marka97203@...> wrote:
> The sail can be drawing well everywhere else but a
> little bit along the foot is still a bit floppy, even with the
> snotter fully snugged.
> Mark
>
> On Aug 18, 2011, at 8:25 PM, David wrote:
> >
> > It seems to me that the edge curve in the foot does not generate
> > shape because the tarp (specially in low wind conditions) tends to
> > take the tension rather than the edge rope. This may be because I
> > use pretty heavy polytarp.
Guys,
My feeling is that the tension in the foot of these sails is so high that the foot is going to straighten out due to the load no matter how you shape it, so it ends up as if you had laced it to a straight boom.
Still playing it safe, I've only been in winds mostly 5 - 10 mph, but it's hard to imagine getting enough tension on the foot to straighten it out completely. My snotter tackle is always right up against the mast already. The angle in the photo of John booming along seems to show it running straighter, but it looks to me like the bisecting approach can only give more tension above the sprit the below.As far as the straight foot having a vang effect to keep the boom down, again in mild winds, with a rounded one I haven't had that problem.MarkOn Aug 19, 2011, at 10:10 AM, Myles Swift wrote:Mark,
So I guess the question is loose/rounded foot with bisecting sprit versus taut foot with level sprit? I know I can ghost better than most other small boats, sitting on the lee side to keep the sail out. I don’t think that would work as well with the bi-secting approach given that the snotter is slacked in that condition. With the Coots rafted up I have sailed around the group in light air within an arm’s length of their boats.
For a view of Mark's JB Jr under full-throttle check the Michalak home
page.
http://groups.yahoo.com/group/Michalak/
That is a birdsmouth mast of just over 20 lb I believe.
Nels
For a view of Mark's JB Jr under full-throttle check the Michalak home
page.
http://groups.yahoo.com/group/Michalak/
That is a birdsmouth mast of just over 20 lb I believe.
Nels
page.
http://groups.yahoo.com/group/Michalak/
That is a birdsmouth mast of just over 20 lb I believe.
Nels
--- Inbolger@yahoogroups.com, Mark Albanese <marka97203@...> wrote:
>
> My Jewelbox Jr. came with a well made dacron triangular sprit boomed
> sail, bisectected and with a rounded foot. I'm just getting the hang
> of it this season ( and may get a call from the previous owner ) but
> can see tthis too. The sail can be drawing well everywhere else but a
> little bit along the foot is still a bit floppy, even with the
> snotter fully snugged.
> Mark
>
> On Aug 18, 2011, at 8:25 PM, David wrote:
> >
> > It seems to me that the edge curve in the foot does not generate
> > shape because the tarp (specially in low wind conditions) tends to
> > take the tension rather than the edge rope. This may be because I
> > use pretty heavy polytarp.
>
Mark,
So I guess the question is loose/rounded foot with bisecting sprit versus taut foot with level sprit? I know I can ghost better than most other small boats, sitting on the lee side to keep the sail out. I don’t think that would work as well with the bi-secting approach given that the snotter is slacked in that condition. With the Coots rafted up I have sailed around the group in light air within an arm’s length of their boats.
MylesJ
My Jewelbox Jr. came with a well made dacron triangular sprit boomed sail, bisectected and with a rounded foot. I'm just getting the hang of it this season ( and may get a call from the previous owner ) but can see tthis too. The sail can be drawing well everywhere else but a little bit along the foot is still a bit floppy, even with the snotter fully snugged.
Mark
On Aug 18, 2011, at 8:25 PM, David wrote:
It seems to me that the edge curve in the foot does not generate shape because the tarp (specially in low wind conditions) tends to take the tension rather than the edge rope. This may be because I use pretty heavy polytarp.
Myles/Nels
You have got me thinking on this one.
I think the reason many people are relocating the snotter further up the mast may actually be because the sail they are using is not cut as Bolger prescribes for a leg o mutton but more like a loose footed sail, therefore requiring the clew to be bisected by the sprit.
I have for some time had my doubts about the use in edge shaping in the foot of the leg o mutton sail as a means of adding belly as:
(a) the edge is not held against a spar [or stretched tight by the edge reinforcement (rope or tape)]
(b) it contradicts Bolgers instructions on many of the plans (e.g.Gypsy) "Foot of sail cut straight to take tension".
It seems to me that the edge curve in the foot does not generate shape because the tarp (specially in low wind conditions) tends to take the tension rather than the edge rope. This may be because I use pretty heavy polytarp.
On the other hand, I have found that the edge shaping up the mast of my leg o muttons works perfectly because the excess fabric forms the bulge required since the edge of the bulge is held all the way along its edge by the lacing.
Regarding high wind conditions, my feeling is that a flexible mast plays a very important role in the capacity to depower the sail by tensioning the snotter.
Look forward to other peoples thoughts.
David
Santiago, Chile
You have got me thinking on this one.
I think the reason many people are relocating the snotter further up the mast may actually be because the sail they are using is not cut as Bolger prescribes for a leg o mutton but more like a loose footed sail, therefore requiring the clew to be bisected by the sprit.
I have for some time had my doubts about the use in edge shaping in the foot of the leg o mutton sail as a means of adding belly as:
(a) the edge is not held against a spar [or stretched tight by the edge reinforcement (rope or tape)]
(b) it contradicts Bolgers instructions on many of the plans (e.g.Gypsy) "Foot of sail cut straight to take tension".
It seems to me that the edge curve in the foot does not generate shape because the tarp (specially in low wind conditions) tends to take the tension rather than the edge rope. This may be because I use pretty heavy polytarp.
On the other hand, I have found that the edge shaping up the mast of my leg o muttons works perfectly because the excess fabric forms the bulge required since the edge of the bulge is held all the way along its edge by the lacing.
Regarding high wind conditions, my feeling is that a flexible mast plays a very important role in the capacity to depower the sail by tensioning the snotter.
Look forward to other peoples thoughts.
David
Santiago, Chile
--- Inbolger@yahoogroups.com, "Myles Swift" <mswift@...> wrote:
>
> David,
>
>
>
> Thanks for that. The automatic preventer aspect of the sprit boom sail is
> certainly a winner. Just looking at sail shape I've been tempted to make
> another, higher, snotter position for high wind. I got the sail directly
> from Dynamite so I'm sure it is cut as well is it can be.
>
>
>
> MylesJ
>
David,
Thanks for that. The automatic preventer aspect of the sprit boom sail is certainly a winner. Just looking at sail shape I’ve been tempted to make another, higher, snotter position for high wind. I got the sail directly from Dynamite so I’m sure it is cut as well is it can be.
MylesJ
A lot of people make this sail themselves for their puddle ducks which
is a Brick derivation and some tend to have the snotter located higher
than shown on the Bolger drawings. They tend also to have some rounding
at the foot and some hollow in the leech to prevent flutter.
Not sure if this is a good idea or not. The sprit boom of course is
quite light and the snotter easily reached even if higher up the mast.
And the PD Racer is very stable.
Nels
is a Brick derivation and some tend to have the snotter located higher
than shown on the Bolger drawings. They tend also to have some rounding
at the foot and some hollow in the leech to prevent flutter.
Not sure if this is a good idea or not. The sprit boom of course is
quite light and the snotter easily reached even if higher up the mast.
And the PD Racer is very stable.
Nels
--- Inbolger@yahoogroups.com, "David" <dir_cobb@...> wrote:
>
> Myles
>
> I've read a lot about the sprit bisecting the clew and I thought I'd
refer this one back to Bolger.
>
> The Leg o mutton with sprit boom is Rig 4 in 103 Sailing Rigs. Here
Bolger says (extract):
>
> "...With this arrangement, when the pull on the clew lifts the end of
the boom, the foot of the sail comes taut and stops the lift. ... The
point to which the sheet leads is not very important either, though it's
best if the sheet leads well aft and no more downwards than necessary.
>
> ...The sail has to be cut to have the three dimensional shape of a
sail set with the foot on a boom, not the shape of a boomless sail as
snap judgement might suggest. The latter would work well only if the
boom bisected the clew angle, which is rarely possible. The higher a
sprit boom crosses the luff of a sail, up to the point of bisecting the
clew angle, the better it will control the sail, but the more it will
interfere with its drive. The weight of a boom carried high up the luff
is greater and it is centered higher - a bad combination for the
stability of the boat. The height shown is a good compromise [closer to
1/3 of clew angle - just past horizontal in the drawing], but
considerably lower is workable."
>
> My conclusion is that Bolger was not convinced that bisecting the clew
either necessary or desirable. He does however state that the sail must
be shaped unless the sprit boom bisects the clew.
>
> David
>
>
> --- Inbolger@yahoogroups.com, "Myles Swift" mswift@ wrote:
> >
> > I wondered about that question of bisecting the clew vs any negative
affect
> > of the higher snotter mounting point in June Bug a few weeks ago
watching
> > the leech flap in a good wind. What about sail shape in ghosting
conditions?
> > The level sprit might be better. I figured I don't know enough to
change the
> > position so I leave it as designed.
> >
>
Myles
I've read a lot about the sprit bisecting the clew and I thought I'd refer this one back to Bolger.
The Leg o mutton with sprit boom is Rig 4 in 103 Sailing Rigs. Here Bolger says (extract):
"...With this arrangement, when the pull on the clew lifts the end of the boom, the foot of the sail comes taut and stops the lift. ... The point to which the sheet leads is not very important either, though it's best if the sheet leads well aft and no more downwards than necessary.
...The sail has to be cut to have the three dimensional shape of a sail set with the foot on a boom, not the shape of a boomless sail as snap judgement might suggest. The latter would work well only if the boom bisected the clew angle, which is rarely possible. The higher a sprit boom crosses the luff of a sail, up to the point of bisecting the clew angle, the better it will control the sail, but the more it will interfere with its drive. The weight of a boom carried high up the luff is greater and it is centered higher - a bad combination for the stability of the boat. The height shown is a good compromise [closer to 1/3 of clew angle - just past horizontal in the drawing], but considerably lower is workable."
My conclusion is that Bolger was not convinced that bisecting the clew either necessary or desirable. He does however state that the sail must be shaped unless the sprit boom bisects the clew.
David
I've read a lot about the sprit bisecting the clew and I thought I'd refer this one back to Bolger.
The Leg o mutton with sprit boom is Rig 4 in 103 Sailing Rigs. Here Bolger says (extract):
"...With this arrangement, when the pull on the clew lifts the end of the boom, the foot of the sail comes taut and stops the lift. ... The point to which the sheet leads is not very important either, though it's best if the sheet leads well aft and no more downwards than necessary.
...The sail has to be cut to have the three dimensional shape of a sail set with the foot on a boom, not the shape of a boomless sail as snap judgement might suggest. The latter would work well only if the boom bisected the clew angle, which is rarely possible. The higher a sprit boom crosses the luff of a sail, up to the point of bisecting the clew angle, the better it will control the sail, but the more it will interfere with its drive. The weight of a boom carried high up the luff is greater and it is centered higher - a bad combination for the stability of the boat. The height shown is a good compromise [closer to 1/3 of clew angle - just past horizontal in the drawing], but considerably lower is workable."
My conclusion is that Bolger was not convinced that bisecting the clew either necessary or desirable. He does however state that the sail must be shaped unless the sprit boom bisects the clew.
David
--- Inbolger@yahoogroups.com, "Myles Swift" <mswift@...> wrote:
>
> I wondered about that question of bisecting the clew vs any negative affect
> of the higher snotter mounting point in June Bug a few weeks ago watching
> the leech flap in a good wind. What about sail shape in ghosting conditions?
> The level sprit might be better. I figured I don't know enough to change the
> position so I leave it as designed.
>
I wondered about that question of bisecting the clew vs any negative affect of the higher snotter mounting point in June Bug a few weeks ago watching the leech flap in a good wind. What about sail shape in ghosting conditions? The level sprit might be better. I figured I don’t know enough to change the position so I leave it as designed.
The shorthand answer, is to spill wind in a gust. A narrower, whippier mast will do that.
Specifically why these designs need that more than some others, is a case-by-case discussion. And it may be that earlier designs with the heftier mast could have used the lighter ones just fine, who knows? Maybe he was being cautious about narrow masts by amateur builders, as there is some risk in building a narrow mast and making it too fragile (a bit too narrow perhaps, or perhaps a poorly placed knot, mistakes a pro would avoid almost as second nature) - and maybe he became more confident of us woodbutchers or maybe he decided, well they'll learn the hard way if necessary. Maybe a lot of things.
I think it's an iffy proposition to look for "one reason" in any of this. Each design decision is part of the overall design. The choice of mast diameter may not have been the only possible solution to whatever the challenge was, it's just the solution that he happened to choose. On another day, he might have solved the same issue some other way. That's not a criticism, it's just a recognition that these things are not easily isolated from the larger whole - likely it's among the best choices of solution, but maybe on another day, he'd've chosen another of the best choices instead. As was noted on another thread, here was a designer open to entertaining alternatives. That means, in essentially so many words, that he considerd that sound alternatives may well have existed.
Brick, as an example, was designed with a very simple goal: what's the simplest, largest displacement, little tiny boat possible. The precise diameter of the mast you stick in the plywood bracket in the front corner is perhaps a nuance in what has to be the least nuanced design (by intention) he ever put out there.
Asking ourselveswhy the end of the mast is an inch narrower on Brick than it might have been, when the sail is apt to be tarp with duct tape and the rig is way over on one side and leeboard is apt to be 18" deeper on one tack than the other, is perhaps a nuance?
From:David <dir_cobb@...>
To:bolger@yahoogroups.com
Sent:Monday, August 15, 2011 12:02 AM
Subject:[bolger] Masts for the 59 sq ft spritsail
I have read and re-read all my Bolger (and Payson) books many times, enjoying learning from the different logic in the different plans and never ceasing to be astounded by the enormous amount of analysis behind each of Bolgers designs, both simple and complex and the subtle design issues that appear in different boats.
One of the things that has perplexed me for some time, and I am yet unable to answer, is the change in the design of the masts for the "standard Payson sail as used for Teal, Surf, Elegant Punt,..."
All the original Instant Boats have 15'6" square section masts starting 1 3/4" and tapering to 3/4" at the head. This mast is also used in June Bug, Sweet Pea and Cartopper.
However, for Gypsy, Reubens Nymph and Brick, he specifies a similar mast (for the same sail) but tapering from 2 1/2" down to 3/4" at the head.
Has anyone got an idea why he changed the mast specs for these specific boats? I have looked at initial stability, length, date of design, type of build and have got nowhere.
Appreciate any thoughts.
David
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To:bolger@yahoogroups.com
Sent:Monday, August 15, 2011 12:02 AM
Subject:[bolger] Masts for the 59 sq ft spritsail
I have read and re-read all my Bolger (and Payson) books many times, enjoying learning from the different logic in the different plans and never ceasing to be astounded by the enormous amount of analysis behind each of Bolgers designs, both simple and complex and the subtle design issues that appear in different boats.
One of the things that has perplexed me for some time, and I am yet unable to answer, is the change in the design of the masts for the "standard Payson sail as used for Teal, Surf, Elegant Punt,..."
All the original Instant Boats have 15'6" square section masts starting 1 3/4" and tapering to 3/4" at the head. This mast is also used in June Bug, Sweet Pea and Cartopper.
However, for Gypsy, Reubens Nymph and Brick, he specifies a similar mast (for the same sail) but tapering from 2 1/2" down to 3/4" at the head.
Has anyone got an idea why he changed the mast specs for these specific boats? I have looked at initial stability, length, date of design, type of build and have got nowhere.
Appreciate any thoughts.
David
------------------------------------
Bolger rules!!!
- NO "GO AWAY SPAMMER!" posts!!! Please!
- no cursing, flaming, trolling, spamming, respamming, 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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You were looking in all the right places I think :-)
Stability. Masts must be designed to withstand the righting moment of the boat and not the size of the sail or wind strength directly. Sail force rises with wind strength, and sail size, but that's not a problem if the hull heels over reducing the effective amount of sail presented to the wind, and the force on the mast is thereby always limited to a maximum that it can take. Gypsy and Reuben's Nymph have double-chined "semi-dory-like" cross-sections that grant increasing secondary stability on largish heeling angles as contrasted to the sharply diminishing stability once beyond smallish angles for the sharpie and scow shapes. They also will most likely at times have crew hiked out, again increasing righting moment. Brick has the widest waterline beam, and is capable of carrying quite large loads, which together produce large righting moments, ie initial stability here (PCB mentioned how a fellow "totalled" one Brick hull built to spec scantlings by hiking out in a vain attempt to drive her hard - just as he'd done once himself to a Tortoise :-). June Bug, Sweet Pea, and Cartopper have less righting moment than those mentioned already as they are either narrower on the waterline, or best sailed with crew weight low in the boat so that not much is to be gained by hiking out because of hull shape (JB - sharpie heeling statics), or discomfort (Cartopper), or they are downwind sailers (Sweet Pea - least force when off the wind). The first three boats require a stronger mast, thicker where it counts, than the last three.
Length. As I recall, there is some difference in the specified length of mast amongst these boats too - due most likey to different "bury" of the mast between partner and step, and also clearance beneath the sail foot... If that's so... maximum mast stress at the partner, so thickness to withstand such stress, will increase inversely to the "bury" height...
Date. Was it for the Gypsy, and on, that Dynamite got PCB to make to sprit boom bisect the clew angle rather than just be horizontal, or some such? This increased the height of the snotter attachment point on the mast, increasing the resultant force it could exert. Like moving an arrow to the proper position on a (symetrical) bow rather than toward one end this allowed the snotter to more easily bow the mast. That's how the snotter is used to flatten the sail for stronger winds, reducing sail force akin to a conventional first reef. Dynamite liked the look, and the efficiency, if I recall right. However, could it be that on some hulls the higher positioning of the snotter may bend the mast too easily, too early for a particular wind strength, so PCB made the mast thicker?
Type of build. Depending how you mean it, this might go right back to hull cross sectional shapes, and waterline beams, ie, stability.
Dave, I'm not sure I've covered all there is to this question. If I've got the marine engineering right, I'd be pleased to know, but even more so if I've got anything wrong... I'm sure others here could express it more understandably anyway.
Stability. Masts must be designed to withstand the righting moment of the boat and not the size of the sail or wind strength directly. Sail force rises with wind strength, and sail size, but that's not a problem if the hull heels over reducing the effective amount of sail presented to the wind, and the force on the mast is thereby always limited to a maximum that it can take. Gypsy and Reuben's Nymph have double-chined "semi-dory-like" cross-sections that grant increasing secondary stability on largish heeling angles as contrasted to the sharply diminishing stability once beyond smallish angles for the sharpie and scow shapes. They also will most likely at times have crew hiked out, again increasing righting moment. Brick has the widest waterline beam, and is capable of carrying quite large loads, which together produce large righting moments, ie initial stability here (PCB mentioned how a fellow "totalled" one Brick hull built to spec scantlings by hiking out in a vain attempt to drive her hard - just as he'd done once himself to a Tortoise :-). June Bug, Sweet Pea, and Cartopper have less righting moment than those mentioned already as they are either narrower on the waterline, or best sailed with crew weight low in the boat so that not much is to be gained by hiking out because of hull shape (JB - sharpie heeling statics), or discomfort (Cartopper), or they are downwind sailers (Sweet Pea - least force when off the wind). The first three boats require a stronger mast, thicker where it counts, than the last three.
Length. As I recall, there is some difference in the specified length of mast amongst these boats too - due most likey to different "bury" of the mast between partner and step, and also clearance beneath the sail foot... If that's so... maximum mast stress at the partner, so thickness to withstand such stress, will increase inversely to the "bury" height...
Date. Was it for the Gypsy, and on, that Dynamite got PCB to make to sprit boom bisect the clew angle rather than just be horizontal, or some such? This increased the height of the snotter attachment point on the mast, increasing the resultant force it could exert. Like moving an arrow to the proper position on a (symetrical) bow rather than toward one end this allowed the snotter to more easily bow the mast. That's how the snotter is used to flatten the sail for stronger winds, reducing sail force akin to a conventional first reef. Dynamite liked the look, and the efficiency, if I recall right. However, could it be that on some hulls the higher positioning of the snotter may bend the mast too easily, too early for a particular wind strength, so PCB made the mast thicker?
Type of build. Depending how you mean it, this might go right back to hull cross sectional shapes, and waterline beams, ie, stability.
Dave, I'm not sure I've covered all there is to this question. If I've got the marine engineering right, I'd be pleased to know, but even more so if I've got anything wrong... I'm sure others here could express it more understandably anyway.
> Has anyone got an idea why he changed the mast specs for these
> specific boats? I have looked at initial stability, length, date of
> design, type of build and have got nowhere.
Gypsybecause of the potential to sail very hard;RNandBrickbecause they have the most capacity except forSweet Peaand are the least tender of the bunch?
On Aug 14, 2011, at 9:02 PM, David wrote:
I have read and re-read all my Bolger (and Payson) books many times, enjoying learning from the different logic in the different plans and never ceasing to be astounded by the enormous amount of analysis behind each of Bolgers designs, both simple and complex and the subtle design issues that appear in different boats.
One of the things that has perplexed me for some time, and I am yet unable to answer, is the change in the design of the masts for the "standard Payson sail as used for Teal, Surf, Elegant Punt,..."
All the original Instant Boats have 15'6" square section masts starting 1 3/4" and tapering to 3/4" at the head. This mast is also used in June Bug, Sweet Pea and Cartopper.
However, for Gypsy, Reubens Nymph and Brick, he specifies a similar mast (for the same sail) but tapering from 2 1/2" down to 3/4" at the head.
Has anyone got an idea why he changed the mast specs for these specific boats? I have looked at initial stability, length, date of design, type of build and have got nowhere.
Appreciate any thoughts.
David
I have read and re-read all my Bolger (and Payson) books many times, enjoying learning from the different logic in the different plans and never ceasing to be astounded by the enormous amount of analysis behind each of Bolgers designs, both simple and complex and the subtle design issues that appear in different boats.
One of the things that has perplexed me for some time, and I am yet unable to answer, is the change in the design of the masts for the "standard Payson sail as used for Teal, Surf, Elegant Punt,..."
All the original Instant Boats have 15'6" square section masts starting 1 3/4" and tapering to 3/4" at the head. This mast is also used in June Bug, Sweet Pea and Cartopper.
However, for Gypsy, Reubens Nymph and Brick, he specifies a similar mast (for the same sail) but tapering from 2 1/2" down to 3/4" at the head.
Has anyone got an idea why he changed the mast specs for these specific boats? I have looked at initial stability, length, date of design, type of build and have got nowhere.
Appreciate any thoughts.
David
One of the things that has perplexed me for some time, and I am yet unable to answer, is the change in the design of the masts for the "standard Payson sail as used for Teal, Surf, Elegant Punt,..."
All the original Instant Boats have 15'6" square section masts starting 1 3/4" and tapering to 3/4" at the head. This mast is also used in June Bug, Sweet Pea and Cartopper.
However, for Gypsy, Reubens Nymph and Brick, he specifies a similar mast (for the same sail) but tapering from 2 1/2" down to 3/4" at the head.
Has anyone got an idea why he changed the mast specs for these specific boats? I have looked at initial stability, length, date of design, type of build and have got nowhere.
Appreciate any thoughts.
David