Here is a sketch of the cowl flaps I intend to use on the Kis Cruiser.
I have a turbo engine so I expect about the same amount of HP as
my C182. I therefore sized the cowl flaps the same. You might think
they are too big but I don't :-)

The air cooled  VW engine thermostat shown is a powerful little mother.
It can hold at least 25 pounds when closed so the cowl flaps
will be spring loaded to open. It also moves about 1.25 inches from
closed to open.

Paul Lamar

 Paul,

You probably don't need the spring to open.  If the
bellows fails (leaks) it opens HARD.   A spring AT
the cowl flap would protect against a linkage disconnect.
These are really nice units and pretty reliable.  Only seen
one or two failures in hundreds, and they were holes
punched in by rocks or something.

Bill

Probably don't need it but what the hey. Belt and suspenders.
I did not get around to making a rig to test the opening force.
I figure it will take a hot plate, a pan of boiling water sitting on a 
bath room scale inside some sort of frame work to test the opening
force. Unless you got a better idea.

Paul Lamar
 
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