Dale Williams wrote:

I'm doing a 13b for my 40 year old tailwind, But my question is related to
cooling a Franklin in a 47 bellanca. I have 3.8 # wp in my upper cowl and
3.2 in my lower cowl . I can't close my cowl flap because of air pressure in
the cowl - I think! If anyone can guide me to a book or give me direction I
would be eternally grateful.

In other words you want to close the cowl flap completely.

Lets see 3.2 inches of water is .037 psi. If your cowl flaps
are 12" by 12" and there are two the load on the flaps
is 34 pounds total. probably half of that is taken by
the hinges so you need to lift 17 pounds. If the linkage
to the flaps is less than one to one ...say the flap handle
moves half as far as the flap you could be back up to 34 pounds.
 
Since it is a certified engine and airplane there is little you can
do other than lift weights to build up your mussels :)

Paul Lamar
 
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