Wishbone booms

[Garry]

I have been thinking about using wishbone booms for my Princess 28 for several reasons. I have no experience with them and little knowledge but they would seem to make sense in some ways. They would be a challenge to build and would add a little complication to raising the masts, but they could be worth it.

The main reason is to be able to rig a "basket" to catch the sail as it is dropped or reefed. The sails will be large enough to present a challenge when reefing or when the entire sail is dropped. Unruly sails can be a danger in a seaway and block forward vision when entering port.

I have an idea that could make reefing easier. I envision the outhaul running through a block at the aft end of the boom, then along the boom, turning down at a block at the forward end, and cleating off on the mast. Reefing outhauls would follow the same path through parallel blocks. Possibly, the lines could be lead through the hollow shafts of the wishbones.

Reefing would be:

1. ease the halyard and the clew line letting the sail gather in the "basket",

2. tighten the reefing downhaul,

3. tighten the reefing outhaul,

4. gather the sail in the reef points.

The forward attachment of the wishbone could be adjustable for flexibility or, possibly, the forward end of each shaft could be attached to pivots fixed to each side of the mast.

I have found little information about wishbones available. I'm sure that Graham will have a good solution, but I wanted to play with some ideas before we get to that part of it. Any thoughts?

[Norman Colter]

Garry, I have some thoughts to share, but want to make sure you mean boom. My Princess sailplan calls for sprits. And I have heard of wishbone sprits. But maybe you're talking about something else.

Have you actually sailed a cat ketch rigged boat? You may just need a good sail and all your questions will be answered.

Norm

[Peter HK]

Hello Garry

In the early 90's I had a 10 meter trimaran with a wishbone boom- I've dug out an old photo

As you suspect the lazy jacks suspended under the boom were brilliant at controlling the sail when dropping/reefing. We never botthered to tie in the reefs as the sail was so secure in the lazy jacks- see

There were a few difficulties with reefing- running lines along the curved boom to winches- but not anything major. We did bend the wishbone in a savage jibe once (at 1 am off Fraser island in the 93 Brisbane to Gladstone when it was blowing a steady 45 knots). You do need to build them quite strong.

Peter HK

[Peter HK]

Norm

I'm a little confused about your post.

Just to clarify the nomenclature- I understand the term sprit without any addition to mean a sprit from mast to the top corner (peak) of a quadrilateral sail.. a spritsail. I've not seen a wishbone sprit.

A sprit boom goes from mid mast to clew and is not uncommonly a wishbone sprit boom.

I take it you are using sprit in the sense of a sprit boom, and presumably then boom in the sense of a standard boom along the foot of the sail. Is that right?

Peter HK

[Garry]

Sorry about the confusion - I mean a wishbone (sprit) boom as in Peter HK's photos.

Peter, I have a few questions if you wouldn't mind. Did your mast rotate? I can make out stays on your rig. Was it hitting a stay with the boom that damaged your wishbone? Were your reefing outhauls lead through fixed blocks at the end of the wishbone, then forward to the mast? How was your boom attached to the mast?

Thanks, Garry

[Norman Colter]

Yes Peter,

That is what I meant, My bad.

Norm

[Tom Lathrop]

Sorry about the confusion - I mean a wishbone (sprit) boom as in Peter HK's photos.

Peter, I have a few questions if you wouldn't mind. Did your mast rotate? I can make out stays on your rig. Was it hitting a stay with the boom that damaged your wishbone? Were your reefing outhauls lead through fixed blocks at the end of the wishbone, then forward to the mast? How was your boom attached to the mast?

Thanks, Garry

Doesn't look like a rotating mast to me.

There appear to be running backstays for flying the spinnaker.

It's a trimaran so the base of the stays is very wide.  It looks as if the wishbone can rotate under and inside the stays when let out.  There is a limit but maybe the main sheet is not long enough to give trouble with hitting the stays.

[Peter HK]

Garry

In answer to your questions, firstly the mast was originally rotating as the designer intended but when I bought the boat the rotation had been abandoned. Interestingly all of the sisterships also had eliminated rotation by then. I was told that rig tension was an issue and forestay sag from the slacker rig required for rotation was greater, harming windward performance.

The wishbone couldn't hit a stay as a traveller line prevented it going too far so it didn't bend by hitting anything. I think it was the twisting forces (the wishbone never sat horizontal in any breeze) against the mast that did it. Conditions were quite strong and usually in a gybe the wishbone would twist from one angle to the other quite quickly. The wishbone was shackled to a stainless bale on the mast to allow it to slide side to side to some extent. There was no adjustment at the mast.

Reefing lines were led from turning blocks at the aft end to winches on the boom itself- a bit awkward to use as the wishbone was usually canted. As this was a fully battened roachy mainsail the reefs were still near the end of the boom- with a more triangular sail there might be some problems with the position of the boom when the clew is a long way from it...you might need a strong topping lift.

Peter HK

[Peter HK]

Norm said

Yes Peter,

That is what I meant, My bad.

Norm

Norm

I've just read my post regarding terminology again and it sounded a little rude- I didn't mean any criticism or to be didactic, just trying to clarify the situation. I find that everywhere the use of terms is a little different.

Hope there was no offence.

Peter HK

[Garry]

Same here Norm. After sailing over 20 years, I still have trouble with sailing terms. Most of the time, I was either solo or the most experienced person on board so my training has been primarily from books. And if I don'y use, I lose it. To write the first post in this topic, I had to look up some terms to get a clew!  ;D

[Norman Colter]

No worries, if I had checked my Chapman I would have discovered that boom can properly refer to any spar used to extend the foot of a sail. My bad. These threads are really useful to our forum. No harm done.

Norm

[Garry]

Here is a sketch of some concepts for a wishbone boom that rotates with the mast. This is a modified image to add vertical adjustment. What do you think?

[Ken_Potts]

  You might want to make allowance for moving the boom up and down on the mast.  changing the angle of the boom varies the downward pressure on the clew (like a vang).

[Garry]

Good idea Ken. I have replaced the sketch above with one that includes tracks for adjusting the pivot point of the boom vertically. This will add a little potential movement particularly when pulling down on the outhaul line - the boom will tend to pivot down on that side. Previously, the pivot pins were fixed on the mast which prevent the boom pivoting laterally. I could probably add a bridle to the line that raises the forward end of the boom which would limit this lateral rotation.

The vertical movement could be accommodated with one track on the forward side of the mast. This would allow the boom to rotate separately from the mast which might be good in some cases but could be damaging if it went too far. I tend to like the more direct connection of two tracks which means the mast must rotate with the boom. This should work fine unless the mast binds and can't rotate, then something has to give!

This seems to be getting complicated with all the outhauls, uphauls, and downhauls!

[Peter HK]

Garry said

This seems to be getting complicated with all the outhauls, uphauls, and downhauls!

I'd agree with that. Is the Princess 28 intended to be trailerable? If so then keeping everything very simple is the way I would go.

If you are going to moor the boat then the added benefits of all the extra lines etc might be worth it.

Peter HK

[Garry]

Trailerable but capable of cruising for at least a few weeks. So she needs to be able to set up easily but be capable of all needed setup.

Maybe the vertical adjustment for the forward part of the boom is not needed. If necessary, the sail could be repositioned up or down to change the angle of the boom.

[Designer]

I have enjoyed watching this discussion evolve. With so many fertile minds we are all going to learn something. 

I have been playing with the rig on P22 #1 for the new owner and I have had this discussion on my mind.

I have used wing masts on multihulls and can see some advantages but I see many pitfalls. For my money simple non rotating round masts are hard to beat for reliability and I see the extra weight cancelling out any perceived performance gain on rotating round masts. I want the rig so that if something fails I can make a lash-up using stuff on board like duct tape, line, blocks, shackles and sail battens. 

I like wishbones and would be sorely tempted to use them on a P28. I prefer the snotter to adjust the sail draft from the mast end and by carefully positioning the hardware, the tightening of the snotter when easing the sail out is minimal. 

As for sail handling we are talking about pocket handkerchief size sails here even for the P28. To furl a sail on the P22 I attach the topping lift to the aft end of the sprit and drop the sail. The snotter is tightened and the bottom few feet of the sail acts like a shelf for the rest of the sail. As the luff is contained by the slides on the track all you have to do is roll the upper two thirds of the sail into the shelf and throw a few sail ties around the roll.

[Peter HK]

Graham said

To furl a sail on the P22 I attach the topping lift to the aft end of the sprit and drop the sail. The snotter is tightened and the bottom few feet of the sail acts like a shelf for the rest of the sail. As the luff is contained by the slides on the track all you have to do is roll the upper two thirds of the sail into the shelf and throw a few sail ties around the roll.

Thanks for the description and photos- this is how I had planned to set up my CS17 and it's good to know that it works. One question- I had planned on a masthead topping lift, with adjustment along the boom, but I see in the photos that the topping lift appears to be from the mizzen mast and thus temporary(must be removed for sailing). Does this have an advantage? What about the mizzen?

Peter HK

[Garry]

Graham,

Thanks for your viewpoint. One of the biggest reasons that I chose to work with you to develop this design is that I appreciate the practicality of your straightforward designs. I can get caught up in trying to solve every potential dificulty and incorporate every possible device.

I appreciate the neat flaking job shown in your pictures. I am still a little concerned about dropping or reefing sails in storm conditions. Most of my seagoing experience is on a 28' sloop and there were times that those sails were all that I cared to tackle. I realize that fully battened sails on tracks will be much easier to handle which is exactly what I want.

If wishbone booms are used with snotters for adjusting sail draft, would there also be outhauls (normal and reefing) and how would they be rigged?

[Charlie Jones]

That's pretty much what Travis does on Pilgrim, except he has topping lifts run from each mast head