Richard Brooksby wrote:

Michael Moore wrote:

https://corribee.files.wordpress.com/2009/06/mk2plan.jpg

This shows the Corribee and Coromandel lines. I think it demonstrates why heeling should be minimised.

Can you explain what you see that makes you say that?

I raised the mast on the new step this morning. Here it is with maximum rake. https://www.flickr.com/photos/rptb1/shares/AU38Xj. Sporty! I should be able to do a few tests in Portsmouth Harbour tomorrow. I'm off to the boat show this afternoon, and a Jester Challenge dinner this evening.

Full blog post with construction will follow, probably next week.

Try this: https://www.dixdesign.com/lofting1.htm If you put in a heeled waterline the shape of hull immersed changes. This will add to the tendancy to turn to windward. (if running the sail will act as a couple and do the same!) Most dinghy sailors agree that the rudder will act a a brake so sail as upright as possible. I think our boats are better if we do the same. Look foeward to hearing how your mast rake helps.

https://corribee.files.wordpress.com/2009/06/mk2plan.jpg

This shows the Corribee and Coromandel lines. I think it demonstrates why heeling should be minimised.

ueli lüthi wrote:

Michael Moore wrote:

…All monohulls do this. When a boat heels the underwater shape changes and the result is they turn to weather…

there's no need for a change of the underwater shape to make a heeling yacht turn to weather – a simple cyllinder or double cone would do the same, as the CE of the sail moves leeward.

Perhaps the CE or centre of sail lift is moving. Perhaps the CLR is moving or the keels are developing lift (as they are designed to do). It's hard to tell. What I do know is that the static analysis suggested by PJR does not give a good result for the Coromandel. Dynamic analysis is needed.

i often sail my (still bermudan rigged) boat sitting the 'wrong' side in light winds to balance out some lee helm – and i try to keep some light wind lee helm when converting to junk, as the weather helm in strong winds might increase with the junk rig.

I agree, and that is indeed what PJR recommends.

Richard Brooksby wrote:

Given ask the very dynamic CLR of my hull I  think the best idea (and my plan anyway) is to have a lot of possible adjustment to the rig.

possibilities for general adjustments are good, but i don't like too many lines to handle when i change the direction. my intention is to have an adjustment which gives a good overall compromise.

Agreed. That is my eventual goal too, but I don't have faith in finding a solution without experimentation, so I'll start out with plenty of freedom and narrow it down. In the end perhaps I'll have just one adjustment line!

Annie Hill wrote:

Richard Brooksby wrote:

Yes indeed. I'm a bit startled by how much though. It probably makes both the “push the boat” and “balance a silhouette” methods a bit useless. I'll have to keep experimenting and using empirical methods. Darn :)

I'm not sure about that, Richard.  After all, one assumes that Blondie used the 'balance a silhouette' for his little boats.  If nothing else, it gives you somewhere to start from.

I'm almost certain the Corimandel was designed straight out of PJR. The sail for example is absolutely identical to the recommended H-M plan and rigging. When I have a moment I'll run the silhouette method myself and see what I get. It would not surprise me at all if I get what I already have.

Given ask the very dynamic CLR of my hull I  think the best idea (and my plan anyway) is to have a lot of possible adjustment to the rig. I don't think a static analysis will give me a “correct” sail position, only (as you say) a starting point. Except even there, I'm starting with whatever Newbridge did, which appears to be a bit wrong.

As Slieve said, I must keep good logs!

Edit: don't you just love autocorrect

Arne Kverneland wrote:

Michael Moore wrote:

Richard Brooksby wrote:

Perhaps the CLR is shifting a long way forward on heeling. Maybe because the keels are assymetrical foils that “fly” upwind, and the windward keel lifts when heeling. I can imagine that would move the CLR a great deal if the keel foils are effective. But this is speculation and I have no proof.

All monohulls do this. When a boat heels the underwater shape changes and the result is they turn to weather. You can test it, as I have done, as follows.

On a F2 or F3 day set up to go to windward, then let go the tiller. My Coromandel will carry on without luffing up. Slowly move over to the lea side and the boat will luff up a little. Move to weather and she will bare away! All well set up boats will do this tegardless of their rig!

Er...
.. that depends on the hull shape. However, during the last forty years, most boats have been made with broader and broader sterns, known as unbalanced hulls, and these certainly will develop weather helm when heeled.