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Old Oct 24, 2011, 08:47 AM
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tacx's Avatar
United States, MI, Romeo
Joined Apr 2009
2,900 Posts
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
2,907 Posts
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
1,177 Posts
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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