Rise Of The Ok etc

Good point about the hat, Dan, mine does too! And of course it's in windy weather that L/D becomes most important, when you want max. thrust/heeling moment.

Blue One, I share your scepticism about manufacturers bike tests. Results depend on how they weight yaw, the wheels they fit and whether the dummy's legs are pedalling. Nonetheless, measurable improvements have been made, meaning you cover a set distance faster and/or use less energy, so an aero frame is handy if you have a flat stage.

Likewise I'm sceptical about claims made for small-area, high aspect boards in, say, the 505 class. There are so many other, major contributors to drag upwind - hull hydrodynamic and aero - and high-aspect foils stall more easily. Nonetheless, I'd be loath to risk turning up at a 5-oh worlds with a large area, low aspect board.

That 10% gain was experimentally measured, not merely theoretical, and the difference between Aero and OK is greater than that. We've had testimony from two people that the OK has plenty of room under the boom, too, so I find it hard to see any advance in the Aero rig over that of the OK, quite the contrary in fact.

I think the end plate effect between the boom and deck is limited. It may look worth while in a wind tunnel, but in the real world, its acknowledged that there's not a great deal of wind between the water level and 1 metre above it. So unless you've got a metre of freeboard its probably better to give yourself a bit more room beneath the boom for ease of handling. 

Originally posted by JimC Originally posted by Medway Maniac And do you really think raising the boom to make the boat accessible to old men and novices while sacrificing efficiency to induced drag is progress? What makes you think that having an 18inch gap under the boom is significantly better than having a 30 inch one?

The OK is an awesome boat, and one that teaches you so much about how rigs work. BTW, there's more space boom-to-floor in an OK than a Laser.
I love mine and can't wait to get started on refurbing my REALLY old one - it's going to be a rocket when done!

On the other hand though, Dan, that area is in the worst of the turbulence and nonsense coming off the hull, is deep in the surface wind sheer in very light airs, and generally, per square foot the least effective on the boat... |so it comes down to balancing factors, as ever, and what's best in an open water boat sailed in turbulent sea breezes might not be so good on a lake.

But we agree that induced drag isn't much to do with it unless you can actually close the gap, as we do with jibs. Mind you, having made a case of sorts that higher booms might not necessarily be very wrong, lets look at my boat...