WishBone Sailing Rig

[brian eiland]

Those appear to be squaring shrouds, similar in function to upper and lower shrouds on a conventional rig.

The same problems exist for both it and the ''A'' frame rig. The mast must be held rigidly upright for the two stay sails to work properly.

I don't think the SMG cat had staysails,...only a roller furling/reefing genoa and main?

 

[Spiv]

They give the rig rigidity, balancing side loads and flexing, similarly as diamonds in single masts.

 

[sharpii2]

I don't think the SMG cat had staysails,...only a roller furling/reefing genoa and main?

Actually, for most practical purposes, the 'main'' is a Stay Sail. It sets on a Jack Line just aft the mast, for its entire luff length. For this reason, it has all the liabilities of a Stay Sail, such as losing its shape, should the Jack Line sag too much. Granted, with the Jack Line being nearly parallel to the mast, this is far less likely to happen than if it were angled away from the mast, but it's a real concern, none the less.

 

[brian eiland]

Spiv, you might find this interesting. A few days ago I discovered there was an old friend of mine in town with his current catamaran Ppalu (the original Peter Spronk built one).

Had dinner with him the other night. Randy West has had LOTS of experiences with all types of vessels over the years. He was also the skipper of Procyon for several years when she was first built. We talked a little about her A-frame, wishbone mast rig.

 

[Spiv]

........Randy West has had LOTS of experiences with all types of vessels over the years. He was also the skipper of Procyon for several years when she was first built. We talked a little about her A-frame, wishbone mast rig.

That is the first cat-ketch I see!!
I wonder why they are not popular with cruisers, but then we have the heard mentality to deal with.


Please tell us what Randy said about Procyon's rig, I remember reading they had problem with the masthead junction of the two masts.
Once again, torsion loads at work... did they solve the problem?

 

[brian eiland]

If you can find photos of the early Peter Spronk catamarans you will find that he was a big fan of lower aspect sail plans that involved two mast. Most were schooners, some were ketches.
Spronk catamaran images

We talked a little bit about that 'connection problem', and perhaps we will again this morning when we meet up again. Interesting solution involving titanium.
But I have even bigger fish to fry....

 

[brian eiland]

De-ketchification of America

That is the first cat-ketch I see!!
I wonder why they are not popular with cruisers, but then we have the heard mentality to deal with.

Perhaps have a look at this article from Eric Sponberg
De-ketchification of America

 

[Spiv]

Perhaps have a look at this article from Eric Sponberg
De-ketchification of America

Brian,
this is perhaps not the best thread for these pic, but forgive me.
You can add it to your collection.
One of the best cruising rig I have seen cruising the last 5years when I was in Fiji:

 

[brian eiland]

Please tell us what Randy said about Procyon's rig, I remember reading they had problem with the masthead junction of the two masts.
Once again, torsion loads at work... did they solve the problem?

So far I know of several features to avoid:
1) Do NOT mount the bases of the mast legs at the gunnels of the vessel, particularly with a mono-hull. There are too many situations where the lower legs of the rig will interfere with high dock surfaces, and/or with tall pier pilings. Procyon experienced damage on several occasions.

2) Do not utilize carbon fiber/nomex-core construction. It's thought that this combination is too brittle for these bendy mast tubes, with some resultant skin-core delaminations having occurred.

3) They resorted to some sort of a fixture at the upper join made of titanium. There are two considerations here;
a) there is a lot more potential difficulties at the upper masthead if the two bottom bases are also limited in their degree of movement.
b) Procyon's tubes were built of straight sections, then torture bent into their arch shapes.

 

[brian eiland]

Here is a posting that needs repeating.

Hello Brian,

Quite a while back already, on this very thread, you mentioned Procyon's masthead problem, and I addressed the issue then...uh, well, I thought I had...but maybe I wasn't intelligible then...or, maybe your memory is even more like Swiss cheese than mine...but wait, here's the link:

http://www.boatdesign.net/forums/boat-design/wishbone-sailing-rig-1999-16.html#post499688

Anyhow, some details and photos are there at that link, and my comments then seem as intelligible as my usual gibberish and there's little hope for improvement, but I will add that by the time I threw the bright idea, of putting an A-frame on my cat, to Malcolm Tennant, he had long since thought of such an animal, knew all about Procyon's problems, and had also been dealing for years with issues of flexibility on catamarans, and he dealt quite handily with this one.

In short, the A-frame structure must not be rigid; there must be allowance for some movement, not just at the masthead but at all junctions and especially at all three corners of the big triangle formed by the mast legs and the boat.

On Catbird Suite, each of the two mastheads has a plate, (a silhouette of a bird) of about 400mm by 1500mm, welded to the masthead, so that the bolts holding the two mastheads together are spread over a large area, and there is considerable play in the bolt holes drilled through those plates (which play I'm sure would be appreciated by any red-blooded bolt). Also, a thick rubber gasket is sandwiched between the plates (and the holes in that gasket are EXACTLY the diameter of the bolts, so that no bolt, or dolt, could complain about looseness of fit). See photo at the link given above.

The bases of the two mast sections are cut in a slight curve so that they have rocker, i.e., Catbird Suite's masts can ROCK. (Can yours?) Each mast base is stepped within and loosely pinned through a stainless collar which is welded onto a stainless plate beneath which there is a thick rubber gasket.

 

[brian eiland]

Double A-frame Rig

Recently a gentleman, David Slater, viewed a posting I had made on the unusual rig onboard "Diomedea Exulans". He wrote to tell me of a rig his father, Alan Slater, had designed and built back in the early 1970's,.... (for those that don't recall, Alan Slater was the gentleman who brought us the PDQ line of catamarans).

What first caught David's attention was the manner in which the two mast on Diomedea Exulans meet at a single point at deck level approx in the middle the boat, then projected upwards, one forward and one rearward from that central point. David wrote to tell me of his father's experiment with a similar concept, but involving A-frame masts rather than single mast tubes.

So here is the document (a copy of a Multihull article) that David just sent to me (attached PDF), and a couple of photos.

 

[brian eiland]

BTW, here is the letter David sent along with that material

Brian ,

Here are the things I have at home to scan . The first is an article that was published in Multihulls magazine . The second was for Publication in the Amateur Yacht Research Society . The 2 photos were taken in the spring of 79 of Annapolis on my way home from the Bahamas as you can see the rig was quite light if unusual in appearance . It was absolutely the easiest boat I have ever single handed . 0 to full sail in 30 seconds (I timed it once ) and there was only one halyard for the storm jib ,the rest of the sails where bolted up and tensioned with a turnbuckle at the bottom . With such small tubes my 19 year old self could go hand over hand up the mast with a bosuns chair around my waist and throw a loop over the top to work on the rig.

My Dad is an engineer who was never afraid of taking his own path and never blew his own horn ,you can see this by his speed claims of 6 to 7 knots . Remember this was in the era of the Alberg ,Grampians so was quite fast at the time .I did see 16 knots once on a broad reach. This boat has the same basic shapes and characteristics as the PDQ36 which he also designed .

Please share this as you like, and if you want you can some of it on that thread .I think people might like to see the rig in action and I always thought it looked elegant under full sail .

It was sold in the late 80,s and went to Flint Michigan ,since then we have not seen it . It would be neat to find it .

THE address and phone # are decades out of date

 

[Kojii]

Some thoughts...

So far I know of several features to avoid:
1) Do NOT mount the bases of the mast legs at the gunnels of the vessel, particularly with a mono-hull. There are too many situations where the lower legs of the rig will interfere with high dock surfaces, and/or with tall pier pilings. Procyon experienced damage on several occasions.
So don't design a sailboat to sail? Design it to sit at the dock? The gunnel/hull section can be the strongest on the boat. You might add don't make a mast over 15 feet cause there's low bridges in some ports.

2) Do not utilize carbon fiber/nomex-core construction. It's thought that this combination is too brittle for these bendy mast tubes, with some resultant skin-core delaminations having occurred.
Cofabrication requires complimentary modulus but fiber orientation and other qualities are important in insuring laminate integrity.

3) They resorted to some sort of a fixture at the upper join made of titanium. There are two considerations here;
a) there is a lot more potential difficulties at the upper masthead if the two bottom bases are also limited in their degree of movement.
b) Procyon's tubes were built of straight sections, then torture bent into their arch shapes.

Bring legs together at hips, not at head. Form arc at layup, organically. Arcs are inherently stronger (done right) than straight lines. Birds have no straight bones.
Tootles

 

[Kamelisko]

Hi. There is a this boat with this kind of rig for sale in Finland.

Don't know anything about it, just happened to notice...

In english:
Iveco Aifo 8061 - 145 hp, special rig, single handlable, electrich winches, generator 6,5 kW, hydraulic stem- and aft props, anchorswinches in stem and aft, accessories for charter usage.

http://www.nettivene.com/purjevene/alumiinivene/636870

 

[brian eiland]

Hi. There is a this boat with this kind of rig for sale in Finland.

Don't know anything about it, just happened to notice...

In english:
Iveco Aifo 8061 - 145 hp, special rig, single handlable, electrich winches, generator 6,5 kW, hydraulic stem- and aft props, anchorswinches in stem and aft, accessories for charter usage.

http://www.nettivene.com/purjevene/alumiinivene/636870

Interesting. I tried a save a copy of the photos of this rig, so I might post them on this subject thread and another subject thread dealing with aftmast rigs.

I was unable to save a copy of the photos. My concern is that these 'for sale listings' disappear fairly soon, and then we have no record of the vessel's existence.

I would also be very interested in asking the owner about his satisfaction/dis-satisfaction with the rig.