UK-Cherub Forum

Cherub Chat => Tech Chat => Topic started by: Will_Lee on March 09, 2008, 07:08:52 PM

Title: Whales and their tubercles.
Post by: Will_Lee on March 09, 2008, 07:08:52 PM
http://www.technologyreview.com/Energy/20379/page1/

This idea runs and runs!

W
Title: Re: Whales and their tubercles.
Post by: ross_burkin on March 09, 2008, 08:06:22 PM
Very interesting. Do T-foils suffer from stalling? I can't imagine that they do as the range of the angel of attack is pretty narrow. I guess the main interest is the "capture more energy" bit and the drag reducing effect at the higher angles of attack. Would this help people with draggy foils? Paul was saying how effective his foil is upwind but down wind it is very draggy, could this reduce the downhill draggyness? Could it be used on the vertical part of a t-foil rudder? Just a few things that first jumped to mind. Some food for thought.

Are you thinking of building a prototype Will? The new boat will look seriously pimp with spiky T-foil.  ;D
Title: Re: Whales and their tubercles.
Post by: Will_Lee on April 02, 2008, 05:56:05 PM
Don't know!

In Hyeres I remember feeling like I had stalled otu the T foil, but thinking about it now I don't think that's right - I think I was just increasing the angle of attack by loading it more.

These tubercles are quite stylish, and I think the message is that they may increase stall angles: So I think the vertical part of the rudder may be the best thing. The only reaosn rudders are the sixe they are is to get you moving at the start and after a tack. If they were smaller they'd be less draggy at speed, but would stall out on tacks etc. Tubercles may open the door to smaller rudders, but not this year!
Title: Re: Whales and their tubercles.
Post by: mathew_harris on April 03, 2008, 09:11:53 AM
would this work the same with daggerboards? 
Title: Re: Whales and their tubercles.
Post by: Will_Lee on April 03, 2008, 10:15:03 AM
Possibly, but I don't see the requirement for very high angles of attack as being the same for a rudder. I may be wrong though...

Also, try getting it up through the case.....
Title: Re: Whales and their tubercles.
Post by: mathew_harris on April 07, 2008, 09:12:31 AM
was thinking about either a smaller daggerboard or possibly trying to remove the build up speed before pointing part as with a bit of luck the blade shouldn't stall as easy?

i appreciate that you would end up with time sawing through the daggerboard case, are there any class rules banning fixed daggerboards?
Title: Re: Whales and their tubercles.
Post by: Phil Alderson on April 07, 2008, 12:40:32 PM
Quote from: Matt Harris on April 07, 2008, 09:12:31 AM
was thinking about either a smaller daggerboard or possibly trying to remove the build up speed before pointing part as with a bit of luck the blade shouldn't stall as easy?

i appreciate that you would end up with time sawing through the daggerboard case, are there any class rules banning fixed daggerboards?
No rule against having a fixed centerboard, however you might have some problems with the chine rule and you would have to cut the top of your mast off as the lowest part of your hull would now be even lower.

It might be eisier to set it up so it comes in and out the bottom as the moths do.

The trouble with most of these things is they work well in a restricted speed and angle of attack range but outside that are very draggy. How do you design it for what you want, you know what works for the whale but it has a different speed range to a Cherub
Title: Re: Whales and their tubercles.
Post by: phil_kirk on April 07, 2008, 12:49:41 PM
We spend our time trying to get nice smooth fair foils and now bumpy ones are shown to be better.  DOH! :-\

The irony of it.