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Originally Posted by BigCat
When I read the first post about the Radical Bay's steering problems, I sent an e-mail to his company, suggesting that they read it and respond to this forum. They didn't respond. The usual responses to steering problems like this are bigger rudders and moving the rig aft, or raking the masts aft. Moving the daggerboard forward would be another solution. I don't think the biplane rig is responsible here, as this problem hasn't been reported with other biplane rigged boats, but it has been encountered with boats having rigs on the centerline. The issue is almost certainly either one of too much lead-the CE being too far forward of the CLR, or the rudders just aren't big enough. I have links to other sites about biplane boats at the bottom of my web page, under a heading that gathers them together as a category. |
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Originally Posted by multihullsailor6
1) The wisdom says "release the windward sheet and sail head to wind on the lee sail, then dumping that and sail off with the leeward sail? Could also try doing the same with the centerboards. Lift the leeward one pre tack, sail away with the ww one up, lw one down".
Here is a comment from the owner/skipper of this cat: "We have tried the sail configuration as explained above, but had still best results sailing up to the point rudder not to tight, releasing lee sail to reduce drag of lee-hull until new lee sail tacks and hauling close new windward sail." |
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Originally Posted by multihullsailor6
What I can now tell you about tacking this boat is
1) In wind under 20kts-ish just before commencing the tack release the windward sheet totally and tack on the leeward sail. Wait for the (new) windward sail to fill and push the bows around, then slowly sheet in the leeward sail and off you go. Only in really flat conditions would we play around with the daggerboards to assist the tacking effort.
Results 10/10
2) In wind in the 20-25-ish kts we have a problem! Depending on wave action we cannot tack and have to gybe.
Results 4/10
3) In winds of approx. 30kts and more we cannot tack nor gybe!!
When tacking the boat would stall 10 degrees from the turn, even sailing backwards did not work to push the bows through the wind.
Attempting a gybe, the pressure on the rudders was incredible, could run down-wind but not turn further to the leeward side. Ended up anchoring in 40kts of wind on a lee shore! (Can really recommend the Fortress anchor  !). And managed to break the mast / gooseneck boom connection due to a gybe which went wrong.
This weekend's experience has put a big damper on my otherwise positive aspects of this rig design! |
There appears to be some real problems with tacking this bi-rig. I might suggest it is a factor of having two distinct turning forces on either side of the vessel as a result of the bi-rig, AND two distinct turning pivot points via the two boards, keels, whatever on either side as well. I've not had time to fully analyze the force diagrams, but I believe it could have a lot to do with the problem. It's not as though you can resolve the two forces on either side into one central force on centerline as is often mistakenly done on multihulls
So what I might suggest is at least eliminating the two 'pivot points' and centralizing them into a central mounted CB affair similar to that I suggest here:
Asymmetrical CB's, nacelle mounted
http://www.cruisersforum.com/forums/...5&postcount=12
You've done a lot of nice
work on your design Alan, and this might be a solution to the easing the tacking problem...pivot around one central point.