I have plenty of opinion on mast bend but have you guys seen this new technique used in the DN iceboats?

What do you think of it? And which one of you is going to be the first to mount some super-duper shroud adjusters with a bare mast (no diamond wires) and give it a try?


Here is a picture, followed by an explanation.

picture
[img]http://tinyurl.com/3xg7e[/img]
explanation

GARY

That's pretty neat! Ice boats are discussed a lot in Frank Bethwaite's "High Performance Sailing" book...he reckons them to be the highest performance sailing craft. At thier typical speeds (3-5 times true wind velocity are possible), apparent wind is basically always from directly ahead. This has significant impact on rig design for these things relative to "soft-water" sailing. Perhaps the lee-bend mast only has benefits at these higher velocities and would prove detrimental at slower speeds and higher angles to the apparent winds in which we cat sailors spend our time.

I think the biggest problem on a cat might be the pumping that the mast would encounter from the lumps on the soft water. The threat of a broken rig is one thing, but the loss of attached airflow would be a big drag.

Still, someone's going to prove, on a cat, that it either works or doesn't; empirically prove it I mean.

GARY

Gary,

Do you and Buzz still have the Nacra? You can try building a new mast like this for it and experiment!

Sheldon

For all we know this excessive bend causes an extra downforce on the scates that allow the rig to be more powerful without the craft slipping away sideways. Something that can not be translated to catamarans.

Wouter

It starts to look like a kite.
Those kite guys can out point a wave board these days.

Man, I would not want to try that on a Catamaran! But anyway, regarding the explanation article:
Where he says that performance is improved because the CE of the sail moves down and to leeward, I think he's only half right. Moving the CE down improves performance, but moving it to leeward does not increase the righting moment of the boat. It would be the same as saying your righting moment improves if you move the crew weight up or down, it dosen't, only laterally from the fulcrum, which in our case is the leeward hull.
Also, I would expect that a large reason for the improved performance is the gain in traction. Keeping the runners from slipping has got to be a big factor. Just from looking at the picture of the bent rig, it looks like the bottom 1/3 of the sail is just driving that leeward runner down into the ice which would keep it from skidding out. Probably great for ice boats, but would be a killer on a cat.