Biplane rig behaviors

[dustman]

Curious if anyone with experience on a biplane rigged catamaran could tell me what happens if you reef or take down only one sail. Since the thrust would be off the centerline of the boat it seems that this may affect helm balance?


I am very interested in using the biplane rig on my small catamaran build, just want to be sure I'm aware of all the factors. If you have anything else to add about how they behave in various conditions and circumstances, please share.

[ggray]

Can't speak from experience, but it probably wouldn't be a hugh deal.

Probably best to try to keep them close to the same size, but on many points of sail one sail will interefere with the other giving different drive forces even if they are identical sailplans.

Outriggers and atlantic proas don't seem to have a problem

[Tupaia]

Google "Cool Change" a Derek Kelsall bi-rig


https://boatingnz.co.nz/ready-for-a-change/ gives some incite.

[NevilleCat]

You could see if you get a response from Jeff Schionning or one of his team, there's a few of his Radical Bay designs around I believe...
https://schionningdesign.com/radical-bay-800/

and one of his Wilderness designs adapted is for sale in West Australia at the moment...
https://yachthub.com/list/yachts-for...ss-1230/280238

the late Pete Hill's old cat is for sale in NZ....been all over the world
https://www.trademe.co.nz/a/motors/b...9?bof=mN7j1jeN

[Chotu]

I did a lot of research on these. I don’t know what the criteria is for you selecting a biplane rig, but the problem with all bi planes and why you do not see by planes in the sky anymore is that they are a low aspect ratio. So they are less efficient. For less weight, a high aspect ratio foil gets you more thrust. It also reaches higher/faster winds aloft.

Sorry I don’t have the answer to our original question, but I figured I would put in some of what I learned here.

[AKA-None]

Originally Posted by Chotu

I did a lot of research on these. I don’t know what the criteria is for you selecting a biplane rig, but the problem with all bi planes and why you do not see by planes in the sky anymore is that they are a low aspect ratio. So they are less efficient. For less weight, a high aspect ratio foil gets you more thrust. It also reaches higher/faster winds aloft.

Sorry I don’t have the answer to our original question, but I figured I would put in some of what I learned here.

Yet research into electric planes are showing at least one design that is a biplane where the wings have sufficient spacing to minimize interference

[Dragon701]

I have experience with the rig. We are an older cruising couple and, in many conditions, we find that using just one sail works great. Of course, it affects the balance somewhat, but not in any ways that I consider negative. Our sails are large -- they are the only two sails on the boat and have the same total sail area as a cat (with our righting moment) would have if its full main and largest spinnaker were set.

A picture of our boat is attached. Please PM me if you would like more information.

[GRIT]

Originally Posted by Dragon701

I have experience with the rig. We are an older cruising couple and, in many conditions, we find that using just one sail works great. Of course, it affects the balance somewhat, but not in any ways that I consider negative. Our sails are large -- they are the only two sails on the boat and have the same total sail area as a cat (with our righting moment) would have if its full main and largest spinnaker were set.

A picture of our boat is attached. Please PM me if you would like more information.

Lovely looking boat. I considered a biplane rig when we were building, but it was a little too "non standard" for my wife's taste.

I'd love to read more about your boat and it's sailing qualities. Is there somewhere I can find more information about your boat?

Cheers.
Paul.

[Training Wheels]

Originally Posted by Dragon701

I have experience with the rig. We are an older cruising couple and, in many conditions, we find that using just one sail works great. Of course, it affects the balance somewhat, but not in any ways that I consider negative. Our sails are large -- they are the only two sails on the boat and have the same total sail area as a cat (with our righting moment) would have if its full main and largest spinnaker were set.



A picture of our boat is attached. Please PM me if you would like more information.

Beautiful boat! We just missed you at Barra. We have a CW tri. Was walking over to see you and you were gone!

Chotu, looks pretty high aspect ratio to me!