Bi-Plane rig on a 20m cat

hiya. this thread caught my attention because I'd like to see bi rigs take off for cats, they just make more sense to me; but i think a bi rig in a 20m cat would be tough to do, beyond designing some seriously awesome masts, i'd be curious how you'd tack-- i suppose you could depower one of the mains to assist with some sort of pivot.

here's a slick schionning radical bay 8000 bi rig with two jibs; looks like he rolls one jib up (towards the end) to help with a tack/not obstruct airflow.
http://www.youtube.com/watch?v=ciP_xuZHih0

 

Thanks for the pictures. I am also interested in how this goes. Please keep us updated

 

I was down at the yard the other day to have a chat to the owner about building space for my next project. Mike has his boat closer to finished but is still waiting on his rigs to arrive.

 

So, could you ask your friend the planned height of his masts off the water? I'm curious as to how much shorter he is going than a single stick. Also, what kind of boom setup is he planning? And... what is the name of the boat? Thanks!

 

I'll ask next time I see him.

 

Name is Bi-Polar
Mast height is about 17.2 mtrs above W/L. About the same height as the conventional rig
Boom is 4.5 Mtr???, don't have the drawing in front of me, rigid vang
Originally it was shorter but a longer boom, pushed the height up a bit to compensate for the shortened boom
Flexibility is to be 8% at a wind strength to lift the hull with 1 sail up, but i can't remember that either sorry advanced alzheimers i think
Aiming for about 50 Mtrs of rag including the mast area each stick. Big flat top main
The wing is 720mm at the base and 390mm at the top

Mike

 

Did you ever get that charter of Coolchange in??...seems if you were really interested in that rig you should do that.

Meanwhile there are some interesting discussions of Derek Kelsall's rig going on over in the forum at 'multihulls@steamradio.com'
http://www.steamradio.com/mailman/listinfo/multihulls

http://www.kelsall.com/TechnicalArticles/TheCatRig.pdf
(a stayed bi-plane rig)

 

How are jibs attached to unstayed mast?

 

I stumbled upon this biplane cat:



I think it's Radical Bay with a little bit custom modified (and painted) hulls. It sure looks great.

 

Is that another one in the background? Is that another biplane rig I see?

 

Sure looks like it... We're taking over the world!

 

I didn't even notice it before.

How does light wind performance of biplane cat compare to light wind performance of ordinary sloop cat?

 

I can only speak for my boat, but generally speaking, the biplane rig uses significantly shorter masts for a much lower COE.
My cat is a bit lacking in light air, but I am hoping to resolve this by adding a furling drifter/genoa.
You can attach a foresail to a freestanding mast just like a rigged mast.
It might be a bit harder to get the luff super tight, but I've found (at least with my small free-flying jib) it to not be overly important.
I am just a cruiser and rookie racer, so take anything I say with a grain of salt.

 

I just found out where that cat in the upper picture is located: it's a charter cat in Thailand.

SY Crazy Horse



(and it is a Radical Bay 8000)

 

Thought I'd post up some pictures of Mike's Schionning Wilderness build. He has finally received his freestanding carbon masts and is test fitting them prior to painting.

you can read about the build of the boat on diy-yachts forum

http://diy-yachts.com/distribution/index.php?f=23&t=407&rb_v=viewtopic