[bolger] Re: Wishbone Boom For Micro?

>Thanks for the explanation. I think the Nonsuch style wishbone also
>has the snotter at the clew, in which case it would be an outhaul.
>
>Peter

No, because the sail is cut in such a way that the clew line is providing
sprit tension. This is the job of the snotter.
--
Craig O'Donnell
Sinepuxent Ancestors & Boats
<http://freepages.genealogy.rootsweb.com/~fassitt/>
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-- Professor of Boatology -- Junkomologist
-- Macintosh kinda guy
Friend of Wanda the Wonder Cat, 1991-1997.
_________________________________

> Munroe and Herreshoff liked sprit booms with jaw against the mast

with the

> "snotter" at the clew end of the sail. I think in this case Bolger

added

> the offset jaw.

Thanks for the explanation. I think the Nonsuch style wishbone also
has the snotter at the clew, in which case it would be an outhaul.

Peter

>Then, there is the scissor-action sprit. I wonder if anyone ever
>built one. See Shearwater (Different Boats) and Lion's Paw (30-Odd
>Boats). The Lion's Paw write-up refers to the "Munroe-type sprit boom
>with an offset jaw on the mast." Whether that refered to the half-
>wishbone, I have never been sure.

Munroe and Herreshoff liked sprit booms with jaw against the mast with the
"snotter" at the clew end of the sail. I think in this case Bolger added
the offset jaw.
--
Craig O'Donnell
Sinepuxent Ancestors & Boats
<http://freepages.genealogy.rootsweb.com/~fassitt/>
The Proa FAQ <http://boat-links.com/proafaq.html>
The Cheap Pages <http://www.friend.ly.net/~dadadata/>
Sailing Canoes, Polytarp Sails, Bamboo, Chinese Junks,
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Plywood Boats, Bamboo Rafts, &c.
_________________________________

-- Professor of Boatology -- Junkomologist
-- Macintosh kinda guy
Friend of Wanda the Wonder Cat, 1991-1997.
_________________________________

>The Lion's Paw write-up refers to the "Munroe-type sprit boom
>with an offset jaw on the mast." Whether that refered to the half-
>wishbone, I have never been sure.

No, it don't.
--
Craig O'Donnell
Sinepuxent Ancestors & Boats
<http://freepages.genealogy.rootsweb.com/~fassitt/>
The Proa FAQ <http://boat-links.com/proafaq.html>
The Cheap Pages <http://www.friend.ly.net/~dadadata/>
Sailing Canoes, Polytarp Sails, Bamboo, Chinese Junks,
American Proas, the Bolger Boat Honor Roll,
Plywood Boats, Bamboo Rafts, &c.
_________________________________

-- Professor of Boatology -- Junkomologist
-- Macintosh kinda guy
Friend of Wanda the Wonder Cat, 1991-1997.
_________________________________

> > I find it annoying when sailing
> > to see the sprit boom bisect the sail causing
> > it not to set properly.

See full quoted text below, but Bolger writes
that the sprit boom touching the sail 'reduces
the power only slightly'.

--- "pvanderwaart" wrote:

> Bolger ...opined (I forget where)

Was it in his book _103 Boat Rigs_
with Rig #4? [which has a wishbone
sprit boom]

http://hallman.org/bolger/rig004.gif

=========Quoted below=========================

RIG 4 Leg-o'-mutton with sprit boom

To correct the bad manners of a boomed sail, the heel of the boom
against the mast can be shifted higher, well above the tack of the
sail. It's then called a sprit boom and ought not to be called a
sprit for a reason I'll explain farther on. 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. A sail rigged this way is docile
on all points of sailing. It's also light to sheet because no effort
is devoted to holding the boom down. With a long sprit boom, sails up
to 150 square feet can be sheeted without any mechanical advantage.
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 downward
than necessary.

A great many methods of holding the forward ends of sprit booms
have been used. The cartoon here shows one form of wishbone boom.
The clew of the sail is fast at the outboard end. Tension on the sail
is adjusted with a snotter, a line led from the heel of the boom in
to the mast, then down to the deck.

The simplest form of sprit boom looks the same in profile: a straight
spar passing against the mast with the standing end of the snotter on
its heel. The drawback of such a boom is that it cuts into the sail
on one tack, possibly chafing the sail and reducing its power
slightly. The advantage of the straight sprit boom, besides its
simplicity, is that if there are shrouds, it can be squared out much
farther. Wishbone booms and standing rigging don't marry happily; for
instance, there was a case of a sizable yacht that was dismasted with
a spectacular crash when the mainsheet broke and the wishbone boom
crashed around against the shrouds.

It's possible to use only half of a wishbone boom. The result looks
like an arm bent at the elbow with the snotter held in the fist. Such
a boom has to be supported by a lift at the elbow to some point
higher on the mast. I've usually had a wire bridle on the end of the
lift to support the boom at both wrist and elbow. With such an
arrangement, the draft of the sail can be adjusted delicately for
different wind strengths, but in a heavy sea the snotter has to be
kept tight or the boom will swing on the lift and slam against the
mast. With that problem and the chafe problem, sprit booms aren't
usually a good choice for a long-distance cruiser in spite of the
apparent advantage in downwind manners. They're at their best in
small and casual daysailers.

The boat in the cartoon has a very small sail lashed permanently to
the mast. This avoids the problem of lowering the sail past the
snotter block. I'll show some other arrangements farther on.

A crosscut sail is shown. With the leech practically straight, as
here, the sail can be cut to hold its shape without battens. The sail
is broad enough to have a workable head angle with the straight
leech. A sailmaker unfamiliar with sails of this kind may need
reminding that the foot of the sail is in tension and must be shaped
and built to stand it. 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 a snap judgment 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 here is a good compromise, but considerably
lower is workable.

In very small boats stable enough to stand up in safely, the snotter
can simply be lashed to the mast at a convenient height while you
stand with the boom on your shoulder.

> I find it
> annoying when sailing to see the sprit boom bisect the sail causing
> it not to set properly.

Think about what you don't see as well as what you do see. The
wishbone lies near the surface of the sail disrupting the wind flow,
while the sprit buries itself in the sail leaving an unobstructed
surface. (Don't buy it? Oh, well, I tried.)

Bolger has designed an offset sprit that he calls a "half-wishbone"
and opined (I forget where) that he thinks it's just as good as the
full wishbone. Two examples are in his book Different Boats: Sweet
Chariot and Wolftrap.

Then, there is the scissor-action sprit. I wonder if anyone ever
built one. See Shearwater (Different Boats) and Lion's Paw (30-Odd
Boats). The Lion's Paw write-up refers to the "Munroe-type sprit boom
with an offset jaw on the mast." Whether that refered to the half-
wishbone, I have never been sure.

Peter

Jason,
I wonder if a windsurfer wishbone would work on the mizzen? I have 3 or 4
booms amongst the used windsurf rigs I've scrounged for my iceboats; they're
lying in the same vicinity as my two micro booms in a corner of the
basement. I'll try to remember tonight to lay the mizzen boom alongside them
to compare but I'm betting they're at least as long, and I know at least one
of them has a length adjustment built-in for the many different-sized
windsurf sails a good sailor needs in his 'quiver'. May need to cut one
down, but that shouldn't be a huge task - the ends are typically molded
plastic with aluminum tubes slipped into sleeves and pop-riveted. If you can
scrounge up one of these, it might save you having to build a curved,
laminated spar. The oldest rig I have has laminated teak booms - and weighs
a ton! I'd hate to get whacked in the head by that if I were a windsurfer
bobbing in the water trying to get back on my board... I'm sure the lighter,
foam-covered aluminum booms are much nicer for that. But it could be made to
look real pretty on the back of my micro, if cleaned up...
My first boat was built entirely of salvaged wood, and I've since had a
tradition that some part of all of my boats must be of recycled or 'found'
material. I've already milled part of an old mahogany table for my
companionway sliders, but this idea has some appeal as well.

Maybe you'll end up with a fully-battened, partially transparent, colorful
mizzen on your micro!! A windsurf-style sail might even match the Navigator
chinese-gaff sail better than the little triangle on the plans.

Paul Lefebvre

-----Original Message-----
From: Jason Stancil [mailto:jasonstancil@...]
Sent: Wednesday, April 14, 2004 12:30 AM
To:bolger@yahoogroups.com
Subject: [bolger] Re: Wishbone Boom For Micro?
I just sat down and sketched out how to put a wishbone on the
mizzen for the micro navigator i'm building.

>I'm trying to figure out how much curve to put on the wishbones,
>what wood to use and whether its better to laminate etc etc,

Laminate, and use carbon fiber between the layers. There isn't much stress
on a straight sprit (wood likes compression). There's a LOT of tension on a
curved sprit and it can snap like a toothpick.
--
Craig O'Donnell
Sinepuxent Ancestors & Boats
<http://freepages.genealogy.rootsweb.com/~fassitt/>
The Proa FAQ <http://boat-links.com/proafaq.html>
The Cheap Pages <http://www.friend.ly.net/~dadadata/>
Sailing Canoes, Polytarp Sails, Bamboo, Chinese Junks,
American Proas, the Bolger Boat Honor Roll,
Plywood Boats, Bamboo Rafts, &c.
_________________________________

-- Professor of Boatology -- Junkomologist
-- Macintosh kinda guy
Friend of Wanda the Wonder Cat, 1991-1997.
_________________________________

>Has anyone built a wishbone boom for the Micro or any other boat? I
>know it is said that the straight sprit boom does not appreciably
>affect the performance of the mainsail on the micro, but I find it
>anoying when sailing to see the sprit boom bisect the sail causing
>it not to set properly.
>I would think that if I used a wishbone boom I might be able to
>alleviate this problem.
>
>Does anyone have any information on building a wishbone boom?
>
>Regards,
>
>John

A triangular boom is shown in some Bolger drawings. So is a half-triangle.
Herreshoff used a triangle on some small boats with the two "front corners"
held up by lines.
--
Craig O'Donnell
Sinepuxent Ancestors & Boats
<http://freepages.genealogy.rootsweb.com/~fassitt/>
The Proa FAQ <http://boat-links.com/proafaq.html>
The Cheap Pages <http://www.friend.ly.net/~dadadata/>
Sailing Canoes, Polytarp Sails, Bamboo, Chinese Junks,
American Proas, the Bolger Boat Honor Roll,
Plywood Boats, Bamboo Rafts, &c.
_________________________________

-- Professor of Boatology -- Junkomologist
-- Macintosh kinda guy
Friend of Wanda the Wonder Cat, 1991-1997.
_________________________________

--- Inbolger@yahoogroups.com, "Jason Stancil" <jasonstancil@h...>
wrote:

> Jason,

I reckon its worth a try. I saw an article on the Nonsuce whilst
surfing the net looking for info on wishbones and it looks an
awesome boat. They also said that one could reef the sail
into "lazyjacks held in between the wishbones which would be another
advantage. Reefing would be easier on the Micro because of the
ability to heave to using the mizzen.
I'm trying to figure out how much curve to put on the wishbones,
what wood to use and whether its better to laminate etc etc,

Regards,

John

> > Has anyone built a wishbone boom for the Micro or any other

boat?

> I
> > know it is said that the straight sprit boom does not

appreciably

> > affect the performance of the mainsail on the micro, but I find

it

> > anoying when sailing to see the sprit boom bisect the sail

causing

> > it not to set properly.
> > I would think that if I used a wishbone boom I might be able to
> > alleviate this problem.
> >
> > Does anyone have any information on building a wishbone boom?
> >
>
> John-
> I know this is not what you wanted to hear, but i think it's a

great

> idea. I just sat down and sketched out how to put a wishbone on

the

> mizzen for the micro navigator i'm building. Thanks for the
> idea....for the mizzen i'm sure it's worthless since the sail is

cut

> flat....but i always liked the wishbone boom. I went out on a
> nonsuch 30 a few years back and to this day that is one of my
> favorite factory boats out there that i will never be able to
> afford. One person no sweat in a thirty footer. I was just along

for

> the ride and some brews, the skipper took care of it all.....the

one

> big main on the monster unstayed rig was a sight to behold perfect
> shape, no "bad" tacks. Sounds like a great idea. I'll try it on my
> mizzen...but it'll be a few months :)
> Jason

> Has anyone built a wishbone boom for the Micro or any other boat?

I

> know it is said that the straight sprit boom does not appreciably
> affect the performance of the mainsail on the micro, but I find it
> anoying when sailing to see the sprit boom bisect the sail causing
> it not to set properly.
> I would think that if I used a wishbone boom I might be able to
> alleviate this problem.
>
> Does anyone have any information on building a wishbone boom?
>

John-
I know this is not what you wanted to hear, but i think it's a great
idea. I just sat down and sketched out how to put a wishbone on the
mizzen for the micro navigator i'm building. Thanks for the
idea....for the mizzen i'm sure it's worthless since the sail is cut
flat....but i always liked the wishbone boom. I went out on a
nonsuch 30 a few years back and to this day that is one of my
favorite factory boats out there that i will never be able to
afford. One person no sweat in a thirty footer. I was just along for
the ride and some brews, the skipper took care of it all.....the one
big main on the monster unstayed rig was a sight to behold perfect
shape, no "bad" tacks. Sounds like a great idea. I'll try it on my
mizzen...but it'll be a few months :)
Jason

Has anyone built a wishbone boom for the Micro or any other boat? I
know it is said that the straight sprit boom does not appreciably
affect the performance of the mainsail on the micro, but I find it
anoying when sailing to see the sprit boom bisect the sail causing
it not to set properly.
I would think that if I used a wishbone boom I might be able to
alleviate this problem.

Does anyone have any information on building a wishbone boom?

Regards,

John