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Old Oct 24, 2011, 08:47 AM
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tacx's Avatar
United States, MI, Macomb
Joined Apr 2009
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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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Old Oct 24, 2011, 09:13 AM
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Crossville, TN
Joined Dec 2004
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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.
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Old Oct 25, 2011, 10:16 PM
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Canada, ON, Windsor
Joined Apr 2008
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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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