So what's with mast rake?

It is complicated and surely more so when the rake is achieved with either a stiff rig (a la Merlin photo) where the mast is raked but upright or a floppy rig. In the latter case more rake also means more fall-off laterally which I would have thought aids gust response.
Doesn't the modern Phantom have a floppy rake system and can offset the fall-off by tightening the lowers?

Originally posted by Fearfull Originally posted by ellistine That's the other odd thing. I would have thought a more raked mast would create more weather helm what with the CofE moving back and everything but the tiller was still really neutral. I've been quite conscious of weather helm after Paul Brotherton said the 4K rudder is too big and can really kill the speed if not balanced. I am still pretty convinced that when the main is fully depowered the CofE is further forward. Certainly on a high aspect ratio rig the sail above a line from the end of the boom to the top of the mast isn't doing a lot.

Edited by ellistine - 26 Oct 10 at 5:15pm

Originally posted by ellistine That's the other odd thing. I would have thought a more raked mast would create more weather helm what with the CofE moving back and everything but the tiller was still really neutral. I've been quite conscious of weather helm after Paul Brotherton said the 4K rudder is too big and can really kill the speed if not balanced. Perhaps lots of mast rake in lighter conditions would create weather helm? It's all very odd. I can see this turning into another one of those 'You Said' snippits in the Y&Y magazine.

in that case, lets all hope we get a pro on here to give us their 'read' on it!

I think the reason that rake depowers is that it moves the CofE down as well as changing the profile of the <wing(s)> sails which means;

less righting moment required = less turbulence around the foils

and

more speed generated by the power from the rig as power is more efficently transfered into motion = greater VMG

Once, many years ago, we tried this on sailing school wayfarers, normally with their sloppy rigs and basic foils, large amounts of weather helm were present in any sort of blow, we raked the mast back and wound on the kicker and jury-rigged cunningham, result = neutral helm.  the contrast was huge. 

Only thing I can compare it to is trying to bear away with the sails pinned in and boat heeled to leward versus bearing away with sails eased and the boat heeled to windward.  To my <simple> mind the forces in play are similar, rig vs foils = turbulence & loss of speed, rig & foils working together = smoother tranference of power and greater speed


hhhhhhhmmmm, sailmakers or similar pro's please feel free to tell me I'm wrong!!


Edited by getafix - 26 Oct 10 at 4:35pm

Originally posted by blueboy If I have a main that is not backwinding, then I ease it in a puff so the luff starts to backwind, the CoE moves aft. If I have (or expect) persistent backwinding, then I want to depower the rig and one of the things I'll do is rake. Now where we came in was the argument that a reason to rake was the assertion (which I reject) that's it is because CoE moves forward as breeze increases.

Just one of the reasons though.