Airfoil for 17 footer needed

[elvar]

Hi all wind gurus.

I used to have blades made of pine for my 17 footer. I am planing to make new blade set and would like to improve prior set. Part of the failure of the old blades is that the tip was to thin (8mm) so it bends back and forth in very common wind. It bends back and to normal position because of different windspeed when blade is in top position versus lowest position. This makes annoying noise. I have seen blades made with chain saw on youtube. I would like to do same or similar because of access to requiered tools.

Can you point out good blades for my 17 footer, dimensions is very much priciated. I am still aiming for Tip speed ratio 6.

Thanks and best regards,

Elvar

[wdyasq]

It is my opinion airfoils for turbines should be low speed ones. The USA35 used on the Piper cub was one of Bob Noggle's and Wayne Abraham's favorites (RIP to both of those) for turbines.

There are many good low speed airfoils. If you have good carving skills, one of the 'fancy new ones' with a non-flat bottom and possibly re-curve in the upper surface may make sense. The HPV, "Human Powered Vehicles", used in aviation attempts may be very useful.

Remember - at 15MPH wind and a 6:1 speed/tip ratio the tips are only traveling 90MPH. Many small aircraft have cruising speeds well above this number.

Ron

[fabricator]

Google Dan Lenox, then read the page on his website on blades, this is the same profile the Dans use.

[elvar]

Thanks. I found this page/site, it is very informative, not only on the blades. As I do not have special carving skills I am wondering if I can user the chain saw method on this type as it would speed up things form me.

Elvar

[fabricator]

Yep, I used the chainsaw method, then I used a DA sander and a 17" inline air body file from harbor freight to finish them off.

[taylorp035]

What shape are your old ones?  Are they flat and did you carve them?  I make my blades with a twisted flat face and a simple air foil on top.  This requires only a small amount of skill and simple tools ( I have used saw-sals, chisels, and spoke shaves to create different blades ).  Basically, the better the tools, the less time it will take.  I would choose something other than pine, like maple, but it requires very straight wood with no knots and very sharp tools.  I guess it depends on what you have available.