Pi Hi by John Pizzey
Hi Rudolph, the Farrier tri used to be an exception in multihulls. I am not up to date any more on recent design trends, but in his Trailertri design and against convention at the time Ian opted for a broad stern semi-planing hull in a light boat. I have some knowledge of them as I sailed in the first prototype and prepared and prosecuted Ian’s patents which served him well. I doubt that you could create this arrangement in a proa, but my life has been spent getting patents for people who have made advancements so I never say it can’t be done and hopefully someone will come up with the answer, if they have not already done so.
I am no expert on hydrodynamics so I can’t fully answer your questions. Non-symmetrical boats have much more buoyancy aft than forward, yet they still manage to sail bow up. Whereas, if most of the buoyancy is centred as in a proa hull with a lot of rocker, any force applied by the rig high up will tend to rock the boat forward about this central buoyancy and perhaps this can or can’t be countered by selective shaping of the bottom of the hull.
When you introduce speed and dynamic effects into the equation, who knows, but I do know that there are less variables for a proa than a cat or tri. As I said earlier relying on amateur advice is risky business but discussions are interesting and help us see other points of view. I particularly noted in his article referred to, John Shuttleworth said “Other types. Proas (Atlantic, ama to leeward, and Pacific, ama to windward) and trimaran foilers. In general these are development types almost exclusively for racing, as far as modern multihulls are concerned, and they have special problems that require particular knowledge, experience and seamanship for safety at sea. Due to lack of space these types will not be dealt with in any detail in this article”
Perhaps he should be asked to contribute to the discussion.
The simple, but not the only amswer is to keep the hulls long and the rig low, minimum rocker may also help and can be used in proas but less so in any other sailing craft as tacking would be a problem. If you want a tall rig for speed, the mast back with a reacher or spinnaker set as I have proposed may give the lift we are seeking. Being an amateur I can’t predict that so I will have to build it and report the outcome, if only I could wave a magic wand.
Cheers
John Pizzey
Hello John,
I never knew that you were a patent attorney, or that you were Ian Farrier’s patent attorney.
I have to say that I strongly agree with your last paragraph where you talk about keeping the hulls long and the rig low. If the rig is clean and efficient, it can be fast as well. Look at the G- 32 catamaran, fast with a tiny rig and with little righting moment.
My proa has a rig the same length as the boat, and I don’t think that I have ever been passed by anything of a similar length.
I quite like the jib only rig (that you have been playing with) as it’s the simplest and by far the cheapest of the proa rigs.
I think that if the lateral resistance could be moved forward enough and the jib tack was placed far enough aft, it would work.
There was a 70’ proa from San Diego that had this rig and sailed across to Hawaii (or French Polynesia) in the 70"s. I don’t know more about it, but it obviously worked.
All the best,
Russell
Hi Russell, thanks for your thoughts. Perhaps I stumbled across the answer when I chose a straight keel, that plus a bit of nose down attitude….. I think Rudolf made a comment along these lines. Also centre of lateral resistance does not have to be so far forward for a “laid-off” rig as significant rounding up force is produced by the sail hanging way out there, and yes I am a practicing patent attorney working by myself after building up a significant practice earlier in my working years. I regard Ian’s tri high on the list of “my” successful inventions, you can see that in “Success Stories” on my website - scientasip.com - Ian was happy to approve its inclusion.
I wish I could boast of never being passed but Pi was a very comfortable cruising boat with a diesel but I did have some wonderful results in her, especially in strong winds. I also had some very fast sails in Flight, but never in company in favourable conditions other than in very light conditions which I have mentioned. Like the G32 you mentioned Flight had water ballast but because of the need to sail both ways I couldn’t easily incorporate the elegant auto fill and empty that they have. Perhaps a proa should be a one way boat, hull upwind on one tack and downwind on the other with the auto water ballast, but that’s basically a G32.
Best regards
John Pizzey