Wishbone booms

[Designer]

Garry, do a search for Nonsuch and Wylie 39. They are cat rigged boats with huge wishbones and there have been enough built to have the rig well sorted out. 

 

The reason that I like to outhaul the wishbone from the mast is that there is no twisting and wracking of small critical parts and while the loads can be high the line and blocks can align to the load. If the worst happened you should be able to create a lash-up to get you home. 

 

There is no reason why you can't run your reefing up the wishbones and back to the cockpit. If you look closely at the above photo you will see the aft reefing line running around the sprit 

 

Peter, on bigger boats I usually run the topping lift from the mast head, but on dinghies to save clutter I drop the sail first allowing the aft end of the sprit to land on the deck and then I run the halyard back to use as a topping lift. On the Princess 22 the mizzen sprit drops onto the boom gallows. On the main I have a short line running to the snotter eye on the mizzen mast as you observed for the main topping lift. On needs to be careful on an open boat locking the main this way because if the main fills it could capsize the boat. 

 

There used to be a question on the Coast Guard licence test, "in which order do you hoist the sails on a schooner". The answer is, hoist from aft to forward and lower from forward to aft. I always do it this way and make sure that the main sheet is not fouled.

[Garry]

Garry, do a search for Nonsuch and Wylie 39. They are cat rigged boats with huge wishbones and there have been enough built to have the rig well sorted out. 

I had previously searched for "wishbone sprit, boom, rig" etc and found little detail, but I just searched for "Nonsuch wishbone" and found a nice description at:

http://www.harrisellis.com/Nonsuch/howandwhy.htm

And a picture of the Nonsuch rig at: http://www.yachtminder.com/Listings/Active/sail/36Nonsuch/Specifications.htm

And this gallery with lots of photos:http://www.pbase.com/nonsuch/root including this gallery which includes Graham's Lapwing as a "relative" of the Nonsuch design (with credit to Graham):http://www.pbase.com/nonsuch/ancestors_cousins_old_new

This site on the Wylie Cat website even has a picture showing the reefing lines coming out of the booms where they are led internally.

http://www.wyliecat.com/info/wishbone_rig.html#

Both the Nonsuch and the Wylie Cat have single sail rigs. For some reason it seems to me that the more balanced ketch rig would be easier to handle than those large sails, especially when caught running and not realizing how strong the wind has become.

[Designer]

That is a good photo. It shows how the wishbone tackle can align itself throughout the entire range of movement. The only thing that I question is the two single part lines for the outhaul/snotter, it would seem a natural to me to put in a multi part tackle for ease of handling.

I also question putting all of your eggs in one basket with that huge main. There is no way to balance the boat, imagine running down wind with a wishbone nearly as long as the boat eased all of the way out. It is one thing to go out in relatively protected waters in a Spindrift for a few hours but how do you heave-to?

[Tom Lathrop]

Graham,

On Tuesday I ran the annual New Year's Day race in the Neuse off Oriental.  There were 45 boats from a small cat boat to 40 something yachts.  One was Joe Valinoti's  Nonsuch 30.  Winds were 12 to 15 for the start and increased a bit toward Adams Creek entrance mark.  On the run to Garbacon Shoal, the wind increased and many were lulled to the wind strength as usual.  Rounding Garbacon some found themselves overpowered and had to fight to get sails trimmed, often by inexperienced crews that come out for this fun race.  The Nonsuch is apparently ballasted well enough and has enough form stability that it was able to carry on in wind over 25 knots to the finish while the smaller catboat retired after the first leg.  Your question was how could the crew of a catboat have made any change while running down wind?  I guess they could not, while the crew of a sloop could choose to change to a small jib or none at all. 

I completely agree with you view of single large sails.  I have recently sailed a gaff rigged catboat and did not at all like having to work in the bow to make sail reduction on a boat without any sail balance.  A cat ketch like the Core Sound would be much easier to make sail changes on though.

[Peter HK]

Garry

In the link  you provided http://www.yachtminder.com/Listings/Active/sail/36Nonsuch/Specifications.htm the wishbone appears to have been bent/twisted a little. That is how mine looked (a bit worse) when I bent it. The twisting forces can be significant. Easy to build a strong enough wishbone in the size range you need though.

Peter HK

[Garry]

That is a good photo. It shows how the wishbone tackle can align itself throughout the entire range of movement. The only thing that I question is the two single part lines for the outhaul/snotter, it would seem a natural to me to put in a multi part tackle for ease of handling.

I also question putting all of your eggs in one basket with that huge main. There is no way to balance the boat, imagine running down wind with a wishbone nearly as long as the boat eased all of the way out. It is one thing to go out in relatively protected waters in a Spindrift for a few hours but how do you heave-to?

Perhaps the idea is when the boom is to starboard the port line takes the load and vice versa for some reason. Although, I do recall seeing multi-part tackles here. The picture below shows a two-part tackle on a Nonsuch 30.

Another point against the large single mast: I once met a couple who were pinned in a marina for several days for fear they could not control their boat because of the strong crosswind in the narrow exit channel.

[Howard]

Garry:

With this last picture, you have swerved back to what I thought it would look like the first time I heard of wishbone rigs. Both sides of the 'bone coming together at a short crossblock for a strong point of attachment for snotter tackle. And relatively narrow 'bone. Just barely enough clearance for the sail to take a nice shape without touching.

I see some problems with the setup shown. The single line for the snotter, anchored to the side of the mast in particular. Imagine wrapping a sail around the mast when let out forward and I see a spot where the sail is going to chafe through. I'd be tempted to put a deadeye on the forward part of the mast for a multi-part tackle for the snotter, and run that to the base of the mast and aft. Imagine the 'bone in a full range of motion....180 degrees. If it's fixed, the snotter is going to have to rotate around the mast 180 degrees....a spiral wrap? But through all the turns, etc, probably enough slack and backlash to avoid tensioning problems. It may tension up, but not enough to matter.

Same for the reefing lines. I can see one coming forward on each side of the 'bone, down to a turning block and back to the cockpit. Not sure how you would secure the reefed tack point from the cockpit unless you do a crossover, but that could be worked out. And it may not be worth it. You may just want to end everything at the base of the mast, knowing you have to go forward to raise, lower and reef the main. The mizzen is already in the cockpit and not a problem.

Next comes the choice of sail track or laced on sails. With fixed attachment points on the mast, lacing lines are out. Sail track looks to be the option and that means the sail is going to wrap around the mast when on a beam reach or forward. Not going to be easy to raise and lower with the sails forward. Dang those compromises.

Next question is what to build it out of? All aluminum? Hey, if they already exist........it's the easy way.

Lastly, Graham's comments about the size of these sails hit home. A year or so ago he sent me a few plan sheets for the Princess 26, one of which shows the sail plan. The mizzen on the 26 is only 86 SF. Mast is around 19'. I think the sail area on my Spindrift 10 is 75 SF and the mast is nearly 18' long. It's a one piece birdsmouth that I can lift with one hand. On a 28 footer, everything gets proportionally bigger, but this isn't the Dreadnaught. It's doable.

[ecgossett]

For some reason the search window on this is not linked or appearing anywhere on my connection, but I'm going via satellite and it's slow.

I liked using PVC in drawing and wrapping glass tape or something around it.. Has anyone actually accomplished this?

I'm thinking it's going to be more straightforward to do a curved version of my current boom rather then attempting a wishbone.

[DaveOnCudjoe]

Edward,

I am planning to convert my Sea Pearl to a Sprit Boom rig. The booms will be curved(half a wishbone)with the reefing outhauls internal and led to the mast end of the sprit. The booms will be laminated wood epoxy. Dave

[ilnadi]

The search window seems to be just off the screen on the top right.

Anyway, this thread has all the great wishbone picture you ever want;

http://messing-about.com/forums/topic/7700-bb-mess-about-2011/page__p__66178__hl__wishbone__fromsearch__1#entry66178

[ecgossett]

I went through that, the stainless looks easy to get a piece and bend then drill some holes..

Not sure how the other bolt was held in. Finding the right ss S hook seems to be a pain, might have to order from B&B.

Now I just have to figure out the right curve.

Here are a few more detail images of Tom Lathrop's beautifully built wishbone sprit-booms.

Tom noted that he finds it important to be able to separate the forward joint. The forward end of the boom has two bolts: only the bolt with the wing-nut presses the two sides together, the other bolt helps maintain alignment. Right Tom?

I think these would ride well at anchor if kept up and level with topping lifts.

--Paul

[Tom Lathrop]

I went through that, the stainless looks easy to get a piece and bend then drill some holes..

Not sure how the other bolt was held in. Finding the right ss S hook seems to be a pain, might have to order from B&B.

Now I just have to figure out the right curve.

The forward end of the boom has two bolts: only the bolt with the wing-nut presses the two sides together, the other bolt helps maintain alignment. Right Tom?

--Paul

The stainless was cut from scrap with a bandsaw and finished with a grinder and polish wheel.. Very easy to cut stainless with an old fine tooth blade. Just make sure you clean out dust from the bandsaw first and check for smoldering afterward. The cutting is not actually sawing but burning and is easier than cutting regular steel. The hooks were made from a stainless rod. The small forward bolt is fixed with a nut/tang/nut assembly on the inside of the booms. Its main purpose is to hold the snotter tang and block.

Good luck with the half wishboom. The single boom looks easier but, in practice, seems to create more problems than it solves.

[tom151]

Good luck with the half wishboom. The single boom looks easier but, in practice, seems to create more problems than it solves.

Tom,

Beautiful work and straight forward design on those wishbone booms - thanks for sharing all the details, have been looking for this kind of help for a while - probably will be trying this approach with rotating wingmasts on a CS20+

Would you be so kind as to share whatever experience you have with the "in practice ... create more problems" of the single wishbone (in boats of this size range)?

Do the masts of the wishbone boomed Marissa rotate at all?

Thanks,

[Hirilonde]

I don't think Marissa has a mast at all

http://www.bandbyach...s.com/ec018.htm

[ChrisObee]

Perhaps they meant Mandy/Amanda

[Tom Lathrop]

Good luck with the half wishboom. The single boom looks easier but, in practice, seems to create more problems than it solves.

Tom,

Beautiful work and straight forward design on those wishbone booms - thanks for sharing all the details, have been looking for this kind of help for a while - probably will be trying this approach with rotating wingmasts on a CS20+

Would you be so kind as to share whatever experience you have with the "in practice ... create more problems" of the single wishbone (in boats of this size range)?

Do the masts of the wishbone boomed Marissa rotate at all?

Thanks,

If you are asking about the masts in Lapwing, they do rotate. Non rotating masts with a snotter do cause a problem because of the changing snotter tension as the sail is let out or in. On the Southern Skimmer mainmast, which could not rotate in the tabernacle, we reduced this tendency by attaching the snotter to eye straps on both sides of the mast which allowed the sprit to swing more without changing tension very much.

Problems with the half wishboom are that it must be built as strong as the double wishboom to take the required compression so no weight is saved. The single likes to droop and must be restrained in some fashion or it ruins the sail shape much like the straight sprit.. The solutions to this problem is what I don't like about them. There are some inventive soultions but you wind up with compromises in performance or complexity or both and I think the full wishboom makes more sense. Also, the reefing cradle will not work on a half wishboom. Storage during transport is the only negative I see to the full wishboom. Your experience may vary.

[rattus]

Edward,

I am planning to convert my Sea Pearl to a Sprit Boom rig. The booms will be curved(half a wishbone)with the reefing outhauls internal and led to the mast end of the sprit. The booms will be laminated wood epoxy. Dave

How do you plan on routing the outhauls through a curved wishbone? It would be great if you had a solution; but every time I think about it I feel friction. Maybe guide wheels?

Inquiring minds want to know ;-)

One thought I had was to route the outhaul alongside the bottom edge of the sail w/ a pulley on mast.

Mike

[PAR]

On a free standing Bermudian with a curved sprit boom, it just makes sense to make it a rotating stick. This is fairly easy. The next logical step is to fix the boom to the mast, eliminating the snotter and use a conventional outhaul at the end of the boom, which can also snake down the boom to the mast for cockpit adjusted tension. A drawing on the previous page shows how a full wishbone boom would work, though with small craft I prefer a half a wishbone arrangement, which is lighter and less windage. Personally (again on small craft) I don't see the need for cockpit outhaul adjustment capability. You just head up, luff a wee bit, grab the boom end, adjust the tension, then fall off on your way. No muss, fuss or extra tackle or weight, extra lines, etc.

If the pivot point on the mast is made with some forethought, you'll incorporate a stop, for the boom to rest on, so it acts like a topping lift, preventing the boom from dropping into the cockpit. Lastly, when shaping the boom, it doesn't have to be a foil section. The forward third of the boom shouldn't touch the luff or sail, but the after portions of the sail may, without noticeable difference in sailing ability (it could be "L" shaped). Chafe is an issue as with all sprit booms, but some well placed tape over the marks left, when you first use your sails will solve this. If you try to make the boom "full" enough of a foil shape, to keep it from touching the sail, you'll have to carry a wheelbarrow shaped boom, which is silly. I've used curved half wishbones for some time and just keeping the leading edge (luff) unmolested, particularly in very light winds can be a huge advantage. The first boat I made this change to, had a straight sprit boom and in very light air, the "unfavored" side wouldn't point very well at all and tacking was difficult. With the curved boom, in the same wind strength, I didn't notice any differences between port or starboard.

[tom151]

Good luck with the half wishboom. The single boom looks easier but, in practice, seems to create more problems than it solves.

[snip] Would you be so kind as to share whatever experience you have with the "in practice ... create more problems" of the single wishbone (in boats of this size range)? Do the masts of the wishbone boomed Marissa rotate at all?

Thanks,

If you are asking about the masts in Lapwing, they do rotate. [snip]

Problems with the half wishboom are that it must be built as strong as the double wishboom to take the required compression so no weight is saved. The single likes to droop and must be restrained in some fashion or it ruins the sail shape much like the straight sprit.. The solutions to this problem is what I don't like about them. There are some inventive soultions but you wind up with compromises in performance or complexity or both and I think the full wishboom makes more sense. Also, the reefing cradle will not work on a half wishboom. Storage during transport is the only negative I see to the full wishboom. Your experience may vary.

Tom - yes, thanks, i was referring to Lapwing (not Marissa) and the photos at http://messing-about...h__1#entry66178

Appreciate the added comment about the single vs double on the weight issue - hadn't thought through that the compression loads really govern weight. (PAR in post #38 above suggests weight savings with a single, will see what he has to say on that)

I am expecting to need addittional clearance inside the double wishbone in way of the mast to allow for over-rotation of the planned wingmast(s) -- and was thinking of making the fwd ends of the booms more separated and fixed with the aft end being able to be opened up for rigging. Seeing your simple approach at the front of your wishbones has provided the direction to use at the aft end. Your very straight forward hardware for the clew-end will be pirated in it's entirety (so thanks for posting the clear pictures) BTW, looks like the aft end arrangement might allow for some spreading of the two sides of the wishbone under maximum outhaul tension... did you observe anything like that (or is it just way overbuilt) ?

New question: about reefing, I see there are reefs in your Lapwing sails, if you've worked it out, would you describe how you rig for reefing please (I'm reluctant to run reefing lines back to the mast (compression loads) and prefer to not relax the snotter the amount necessary to allow for afixing the reef-clew directly to the boom end).

Sincere thanks for helping this noobie.

[Tom Lathrop]

Appreciate the added comment about the single vs double on the weight issue - hadn't thought through that the compression loads really govern weight. (PAR in post #38 above suggests weight savings with a single, will see what he has to say on that)

BTW, looks like the aft end arrangement might allow for some spreading of the two sides of the wishbone under maximum outhaul tension... did you observe anything like that (or is it just way overbuilt) ?

New question: about reefing, I see there are reefs in your Lapwing sails, if you've worked it out, would you describe how you rig for reefing please (I'm reluctant to run reefing lines back to the mast (compression loads) and prefer to not relax the snotter the amount necessary to allow for afixing the reef-clew directly to the boom end).

Sincere thanks for helping this noobie.

First, the weight of a single beam will likely be less than a double one of the same total cross section. That is because the stiffness of a beam is proportional to the cross section dimensons and that will be greater in a single. Of course the stuff that keeps it from sagging will add some weight but a single will likely be marginally lighter weight.

I have not seen any spreading of the clew fitting. That will be a function of the stiffeness of the stainless fitting though and I don't expect any spreading.

I have only reefed once at the Small Reach Regatta in Maine and did not really need to then. The Lapwing is not really highly canvased and is pretty easy to handle so reefing is not often needed. I just lower the sail and tie in the reef points in a roll along the foot and insert the sprit in the reefing cringle. With the double wishboom, reefing is probably easier since the reefed foot can drop into the basket lines from the booms if they are fitted. I wanted reef points because I am well past getting senior discounts and may need them.

I think some inventive thinking will be needed for a wishboom on a roatating wing mast. The over rotation will need a very wide space between the booms near the mast. Tension between the snotter and clew will tend to limit mast rotation. I cannot immediately see any way to mount a wishboom directly to a rotating wing mast since the over rotation needed for best performance would then not be possible on the wingmast..