Herreshoff's catamaran reasoning

Cool! Hey! Is that the same group that had a rigid-wing trimaran for a while? And are you part of that group? It looks like they've got some kite technology going there. And they also have an asymmetric geometry, but no need to have the main floatation leeward since the kite sail doesn't heel the boat over.

You know, that's a good question. If all you want to do is set speed records, you're going to stay on a broad reach, right? So why would the rigid wing be so superior to a sail, when the sail saves on weight, especially a nice simple sprit-boom cat rig, and doesn't have to be as flat as a sail designed for sailing close-hauled? Another "whacko" idea that does over 30 knots!

 

Thanks for those links Brian, they're interesting. McIntyre dealt with the torsional stresses even further. He could push the leeward hull forward and the windward hull aft, so the whole boat was shaped like a parallelegram.
That also brought the leeward sail ahead of the shadow of the windward sail. Thanks again.

 

Tipping rigs.

It seems to me that the ORMA 60s are tipping their rigs to windward. I think this can be for several reasons.
First the basic angle of heel for those boats is pretty extreme, so they may be just getting the rig back to vertical.
Second, the rig weighs something, so moving its mass to windward adds stability to the boat.
Third, it reduces the projected area, just as heeling to leeward reduces the projected area, but it is probably a better choice because it increases stability instead of reduces it and some portion of the side force will in fact help reduce the displacement of the boat.
It isn't a magic feather, but there are some pretty good reasons to consider it along with other ideas to increase the speed and efficiency of sailing craft.

 

The ORMA 60s used to have 2.5m hydraulic rams, canting the rig by (IIRC, vague memory) 6 degrees, on a boat healing considerably more. The effect on weather helm was considerable, Frank Cammas said. It was noticeable that the boat was an absolute ***** when (prior to a tack) the windward ram was let go and the rig canted to lee.

I think Frank and Nigel Irens and others said that they don't use the rams on short courses.

Skippy; the apparent wind is well forward at a speed of 30 knots. You're actually far from broad reaching, but closer to sailing to windward.

 

I thought point of sail was defined relative to the true wind not apparent wind.
But I see your point, so at those speeds you'll be sheeted in much more and the sail's/wing's angle of attack will still be low.

 

If you read Herreshoff a bit more, he said why the design failed. The race commities banned the boat because it beat everything afloat. Herreshoff made a living from designing and building boats. Since there was no market for a banned from racing boat, he dropped it .

 

That's right. McIntyre also had trouble popularizing his design in the 1930s for maybe the same reason but also the depression.
I read that Herreshoff's cat won the one race it was in even though at one point the boat pitchpoled and sat there for several minutes while other boats passed it, then it eventually passed them after recovering.

 

excerpts from Herrshoff Chronicle

from Nov 1877, Bristol, RI (courtesy of the Herresoff Marine Museum)

It is true that the enormous disparity of speed between the catamaran and an ordinarily built boat is most noticeable when sailing with the wind a little abaft of beam. Sailing to windward is a paradox at best, and a small amount thus gained is a greater triumph than much greater distances gained in the headlong, freewind sailing. Windward sailing is not a weak point of the catamaran. I can, with a good whole sail breeze, beat to windward faster, by a mile an hour at least, than any sailing vessel afloat, or I can beat the WM. R. BROWN, the WM. T. LEE, the SUSIES, DARE DEVIL, or any other boat of that class that can be named, one-quarter, or five miles to their four, under the conditions before mentioned. I’m not making an idle, empty boast. I know well of what I am writing. I have sailed every class of vessel, from the small cat-boat up to the first-class yacht, and their performances are individually familiar to me. And further, if the owners of the boats whose names I have mentioned, want to be practically, convinced of this, that is, of the speed of the windward sailing of the catamaran, the best way for them is to try it on. I shall be only too happy to do so anywhere and at any time.


If, in a catamaran, you are sorely pressed by wind or wave, turn her bow to leeward. There you will find comfort and consolation, so light she is, and presents so little resistance, that the wind blows her along like a bubble floating in the air, We laid to off Point Judith, at seven. for breakfast, after which reinforcement we continued with the wind gradually dying. When off the Connecticut River we decided to steer for the Long Island shore. We had not gone far on that course when the wind hauled back to east and commenced blowing. Now, with the wind cast in Long Island Sound, and blowing a single-reef breeze, it does not take long to kick up a sea, especially with an ebb tide. At least it did not that day, and soon the TARANTELLA commenced to race, lifted, and borne on the crest of a wave, she should shoot forward with incredible speed. We settled away on the peak halyards and made, in effect, a leg-of-mutton sail from the mainsail. This made a very easy rig, and one particularly adapted for off-wind sailing.

And now, whilst we are flying along, with the waves lifting and breaking high under the after tie-beam, let us overhaul another of the alleged failings of the catamaran, to wit: their tendency to turn over endwise or pitchpole. Now, the center of effort of the sails of the TARANTELLA is 14 ‘6” above the waterline. With the wind abaft of beam, the tendency to bury the bows of the hull is quite obvious. This desire to bury forward is corrected, in a measure, first by having more than an ordinarily large jib, which, on account of its inclined position, lifts strongly that part of the boat. Then the midship link, at which point is imparted most of the press of the sails upon the leeward boat, is so placed in relation to the displacement of the hulls that the downward push (to which
the force of the wind on the sails is resolved) presses more toward the stern, so the leeward boat always keeps in good fore-and-aft trim. The trouble then lies only in the lifting of the stern of the windward hull. Of course if you lift the stern of the boat, and thus make the bow bury itself, the effect is just the same, and just as unpleasant as when the bow sinks for want of buoyancy with the trim of the stern where it should be.

Building the catamaran high in the bows cannot remedy this fault in the least degree; the only thing to be done is to take care of the stem, and the bow will take care of itself. Having stationary ballast will keep the stern down, but this is against my principles. I want to have everything about the boat as light as can possibly be; so when the stern of the TARANTELLA looks light, my companion sits on it, and says it is one of the best seats on the whole boat. It is almost always dry, and one gets three a real sense of the speed with which she tears along.

 

excerpt from NewYork Herald 1877

(courtesty of Multihulls Magazine)

Have a look at Amarylis

 

Thanks for that reference CT, I can see why you recommended it. Definately a Racer's Bible.
I've never seen so much space devoted to wind patterns. I probably won't get into it deeply right away,
but I could see it being almost as useful for a cruiser who wants to squeeze another knot or so out of his old tub.
It's also good to see a second opinion on Smith's work, I'll be studying that closely. I like Bethwaite's HSP too.
Again, thanks for the ref.

 

Lifting Force by the Sails

I saw where this subject thread was rather old, but there is some old Nat wisdom in it that desires renew light. I referenced this sdubject thread in a posting on my aftmast subject HERE
http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623-22.html#post411428
...so I thought it would be appropriate to ressurect this subject thread for discussion as well.

 

UPWARD Lifting Force by Headsails

This subject of upward lifting forces via headsails has come up again,
http://www.boatdesign.net/forums/sailboats/sail-loading-rig-rig-loading-vessel-2293-7.html#post769905

...and looking back thru some of my old postings I arrived at this one again, ...figured it deserves some new sunlight,....particularly this observation by Herresoff.....

 

Herreshoff on catamarans and sail lift

Thanks very much, Bryan-I hadn't read that before that I remember!

 

Doug it seems I've forgotten a lot of the postings I've made even myself
I find some of them when I'm trying to dig up some info from the past to answer some naysayers

 

Why we have outriggers; if you don't mind a bit of humor?

Brian E, very interesting topic. Mr. Speer, interesting insights.

Much appreciated by this dodger, as always.