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Oct 24, 2011, 09:47 AM
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tacx's Avatar

rear fin

Hi All,
Building a GP Electricub on floats. I have read, and have seen pics of a fin added to the bottom rear of the fuselage. What is this needed for? Here is a pic of one.
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Oct 24, 2011, 10:13 AM
Registered User
The sub fin stabilizes the wetted side area of the floats behind the CG ( like the feathers on a dart ).
Some long tail moment designs don't need them, but all mine had them.
I make this area 1/3 of the vertical area just from personal preference.
Some, like most DH-2 Beavers, have them mounted on the h. stab.
Oct 25, 2011, 11:16 PM
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Cougar429's Avatar
Art Schmitz is correct. Floats normally have more surface area ahead of the CofG and without that added fin can destabilize the yaw axis, especially in a turn. What you would notice is the nose of the plane trying to yaw away from the direction of the turn.

It is usually an easy addition and makes a world of difference on planes such as the Cub.

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