Bi-Plane rig on a 20m cat

Not so fast

Bear flag

Be careful in assuming that the apparent will always be in front of the beam. Cruising cats are cruised at speeds less than a mono races and spend an awful amount of time with the apparent aft of the beam.

As for lifting the CG instead of rotating - there is no change at all. In a cat you always lift and rotate the CG over the leeward hull - it doesn't matter what rig you use and doesn't matter if the rig is to windward or leeward - the boat still needs torque.

I have my own doubts on twin rigs - unlike some (Rob and I disagree here) I like stays and being able to easily add sail (kites and reachers) and trim the boat for up and downwind sailing. Also I like being to windward of the rig in nasty stuff whereas a twin rig always has a rig to windward of you.

Best advice - go for a sail - a long one and see for yourself

cheers

Phil Thompson

 

If the wind is aft of the boat and you are running or on a broad reach, you could run with both sails wide to either hull. There may be a small angle where blanketing is "bad", or that your windward sail is acting more like a drag-sail than in lift, true enough, but its not much of a sacrifice. Better to change heading a bit and gain VMG.

I agree, about stayed vs. unstayed, the advantages of a jib are too compelling, but there is no reason one can't have a stayed bi-plane with rotating masts and have your cake (or jib) and eat it too?

As far as rotating...

What I was saying is that the point of leverage would be different. In effect you would have 2 shorter levers instead of one tall one, one orthogonal to the leeward hull, and one orthogonal to the windward hull. Sail area for sail area, this should be less than the one big lever in the middle of the two. (more likely you will just have more sail, assuming you have stays for jibs)

I like your advice, boatless for now though, so have to rely on my friend's charity and schedule.

 

Yes, Gary its certainly an interesting boat. was it built to compete against the orma 60's, if so how did it go?

As we are talking cruising boats here, deep T foils and aft C of E is going to be a right pain in the proverbial for the average cruiser. . Headsails on a roller furler are probably the most useful sails on a cruiser and mainsails are the most work (hoisting and reefing). Wanting two of the beasts seems a little naive.

Regards.

 

Well Bruce, this forum began with questions of pitching (and other questions) of bi-plane rigged catamarans - with no emphasis whatsoever placed on cruising.
Parlier's cat was built to fit into ORMA class but the trimarans outperformed it, especially in lighter conditions. However the stepped, seaplane type hulled cat set, and held for a short time, a 24 hour run record. It was designed for speed in stronger winds when it broke free like a powerboat hydroplane - but was sticky in the light. The stepped hull point was not part of the original question here, just that the most highly developed bi=plane catamaran had them - and a more conventionally shaped hull catamaran would be a better all rounder, not as fast top speed but better averages IMO. The inverted T rudders make perfect sense if you're worried about pitching and reducing nose diving downwind. And I disagree with two mains being difficult to handle; they are far more efficient than headsails and everything can be controlled from, or close to the cockpit. Have you ever sailed on a bi-plane rigged multihull?

 

That does seem to be my biggest problem. I have talked to a lot of people with single stick experience, but very few have ever sailed a bi-plane rig on anything the size of which I'm considering (about 20 m (60') length, cruiser).

The advice to go sail one, is good advice. I plan to charter Coolchange and try their biplane rig, and then immediately charter a single mast cat of about the same size for comparison. Unfortunately, my early sailing experience is on a two mast mono. Any suggestions on a good catamaran brand to charter to get the best example of a good long range cruiser (not something good for just the Caribbean waters, for example). Something in the 55' to 60' range.

Whatever I decide to buy/build, it's going around the world a few times, though not necessarily a circumnavigation, just a lot of miles crossing the Atlantic and Pacific several times. I don't plan on taking it too far north or south. I've sailed the North Sea of Germany in bad conditions and don't really want to experience that again, but I need a boat that could handle it should I get caught with my shorts down, so to speak

 

Thanks for the reply. So Parliers cat was designed for a specific but very narrow range of conditions so the Bi rig was probably a good choice in this particular case.

Post #3 states "

I looked, it seemed to have no relevance to my questions about a bi-plane rig for a catamaran cruiser."

Hence the emphasis place on cruising.

I find it interesting that you consider inverted T foils ( weed catchers par excellence) would be a valid solution to the pitching problem for you average real world sailor.

Regards the two mains, nothing is easier on a cruising boat than furling and unfurling a headsail. A main requires a lot more effort. We seem to find that were always trying to slow the boat down when cruising so chasing the last 1% in efficiency gains is a total WAFTAM.

Regards

 

You could look at Brian Elliand's cool aft-mast or mainsail-less thread. There are some wicked cool boats in there. In particular there is this CAT somewhere in that mess of threads that has really slim and trim hulls, very useable bridge deck, and 3 roller furled sails on the bow, all of them self-tacking and non interfering, 2 jibs and one gennaker or something? Regardless its pretty cool, its fast, stable, sleek, and effortless to sail.

 

Crew available here!

 

It depends on what you mean by mainsails are the most work. It is much less work to tack a boat with a mainsail only rig than a boat with an overlapping jib . In fact its no work at all. Not only is it less work to trim a mainsail than an overlapping jib ,sails of 450 sq. ft. can be trimmed by a women without the benefit of a winch. Add to that the ability to tack through a crowded harbour single handed , and I think that despite the fact that it might be appropriate to use the windlass or have a dedicated electric winch to raise the sail, single or double mainsail rigs are great for cruising. As for not having a stay to hoist extra sail it is no problem to set flying sails off the wind.

 

Yes timothy, tacking a mainsail only rig is certainly very easy.I've built and sailed a lovely cape cod cat boat, but thats another story. Aren't we talking cruising?. If the course requires tacking then leave the pick in the water and wait until tomorrow.Cruising is about setting the sails and switching on the auto pilot. I'm not saying mainsails are bad, I have a perfectly good one I'm very attached too. All I'm saying is one mainsail is quite enough. Once the course is down wind, its time for the kite or if there's a lot of wind then just unroll the heady which keeps the C of E where it belongs. Geees if I wanted to root around with a mainsail hanging out to leeward over the ogin I'd buy a mono and not ruin a perfectly safe catamaran by mounting Bi rigs.

 

Well, for running down wind I'd have to disagree here. This is one of the areas where a biplane rig is the safest and best rig around. You goose wing and rotate the (unstayed) masts forward of center line when running down wind.

This is an unbelievably stable configuration. It is basically self centering and doesn't run the risk of a jib if the boat twists a little going over swells. As the boat twists it brings one of the two main sails more directly into the force of the wind, which cause that sail to push more than the other, re-centering the boat down wind. If you want more speed, hoist a square spinnaker attached to both masts, right down the middle, that's a lot of square footage of cloth.

If anything, down wind is the single best way to a sail an unstayed, bi-plane rig. (I got this info from some people who have sailed one).

 

Thats funny!

Junk rig owners talk in the same glowing terms about their rig choice.

 

Bruce, you seem to have an antipathy towards fast sailers. Your comments about mainsail control "not being bad" implies that some other rig is superior. What other rig - a headsail only set up? That is load of complete and utter toss. Strange that the most efficient sailing yachts have not embraced this lazy, poor windward performing set up. One wonders why. Also Parlier's cat, although beaten by the ORMA tris in light conditions (and for someone who is deeply cruising oriented, this should not be important ... but you make a point about it) - that so-called narrow range of conditions for Parlier's design lined up with the world's most strung out, high performing, and long developed tris, would still whip most other turd boxes around, especially a headsail only rigged one. But performance is of no interest to you; you'd rather stay at anchor than having to beat somewhere.
Yes, inverted T foils will pick up weed - but so do all raked forward or vertical foils and rudders - and even bulb keel monohulls .... there's a few of them around too.
You still haven't answered if you've sailed on a bi-plane boat ... but you don't need to - it's obvious that you're just blowing smoke.

 

Well, I talked about running down wind being good... but I'm not all rosy about bi-plane rigs... they don't perform as well on a reach and there is some question about how far they can point into the wind. So, no, I'm not all a glow about the performance of bi-planes, but when the owners of a bi-plane rig tell me how well it runs down wind, I have to accept their opinion over those that haven't sailed much, if at all, on a large bi-plane rigged yacht.

 

Becaris, on a reach a bi-plane rig is at its best; large sail area set lower equals speed without much heeling moment - that is, a reach with the apparent just forward, or aft of abeam and with the leeward sail not blanketed. And if the latter does occur, you head up or down a fraction to rectify the situation, no big deal. The weakest point is beating BUT with decent underwater appendages and rotating masts or a very clean and uncluttered double rig, these boats can sail to windward just fine. Also they pitch less because of the lower CoG. All boats are compromises - you just pick the version that you like the most.