I didn't think about rotating it. This should be 1:1 if printed on 8.5" X 11" paper (what size do you guys use down there?).

Matt,

When do you expect to have the go ahead to race the Hobie 20 with the EPO2's?

Ian

Matt Miller doesn't have anything to do with whether the EPO2s are class legal on the H-20.

Depends on the HCA Rules Committee:
Jeff Alter (chair - Hobie Family Rep)
Doug Skidmore (Hobie Cat US rep)
John Dinsdale (Hobie Cat Europe rep)
Mal Gray (AUS)
Erik Olsen (DEN)

But Matt could give us an update since he shares office space with Skidmore . . . .

A4 is standard paper size here, 210 x 297mm.

A3 is exactly double the size, 297 x 420mm.

Concave sections were mentioned (in relation to the NACA 63 and 64-series).
I have heard someone say that Marstöm's Tornado rudders have concave surfaces in front of the trailing edge.

So I would like to know:
Are concave surfaces on symmetric foils of any advantage for high-perfomance 16-20-foot cat?
Which symmetric NACA-profiles have concave sections?
Or are concave sections/surfaces only useful in asymmetric profiles?

Stein

The IHCA rules committee contacted me about this a few weeks ago. I have never sailed a Hobie 20 so I've asked our Vice Chair Phil Collins to help out. He had some questions so he's going to test the EPO2 Hobie 16 blades on the 20 and let us know what he thinks.
Bob

The only concave sections that I've actually seen are on some of the newer F18 rudders where the foil section is stretched out on the trailing edge leaving a concavity near the back. I have no idea as to what the performance advantage is supposed to be and I can't imagine why you would want a concavity on the leading edge.

Tip loss?

Or one hell of a weed catcher?

the hollows are in the foil profile. for instance, with the rudder down in the sailing position, if you hold a straight edge horizontally on the trailing edge of the rudder to the high point of the camber, you will have space under the middle of the straight edge - this is the hollow.