HT08 section shaped keel is KEY in National's win

Hello, I am an amateur sailor derived into modelboat sailing, designing and building. I sail RG65 Class which is very popular in Argentina.

Last November I was lucky to win the National Championship with an old boat ... with new modiffications.

It had a terrible keel, unknown section, approx 9% t/c, max thickness at 45% from le. Did not go well to windward nor downwind. I had the feeling that it was the keel...

I found on these forums a post by Mark Drela suggesting the use of one of his designs also offering so generously a method of shaping the foils by sanding.

So I bought 3mm unidirectional carbon fiber and started sanding... during 4 days!!!!

Now the keel is anyone's envy: 4.5% t/c. Flexes the same amount as professionally built keels of 6% t/c, has a SHARP trailing edge and the boat was born again. Highest pointing boat of the whole fleet at same speed and fastest at similar angles, either wit calm winds as with strong weather. Also downwind the boat was benefited.

I am grateful at Dr. Drela for sharing his knowledge.

I also want to leave a question open: would a section shape of parallel sides with fairings of the leading edge and trailing edge, thinner to about 3.5% t/c perform similarly ? I mean similar Cd for downwind and similar Cl/Cd for upwind?

This would be a huge advance in simplifying the building process.

Thanks, Luis Bordino

 

Luis, that 4.5% t/c is remarkable-congratulations..... Would you post a link to Mark Drela's suggestions?

 

Doug, sure I can, there are more than one reference but this one is clear, I just don't know how to quote posts from other threads... the thread is called "Foil section at low Reynolds numbers" and there are others, please search HT08 on these forums:

 

Thanks!!