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Covering butt rib

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Posted

My Mk IV kit came with a wing tank "upgrade" set. The wing root end of the tanks has a flange about 1" deep (on the top only). I extended the bottom of the first rib with a 1/8" plywood strip with gussets glued to the tank. Now considering gluing in some vertical braces up to the top flange so I can stretch the fabric over the butt end of the wing. The fabric will not be glued to the tank except for the plywood rib strips. ( I glued in carbon fiber strips under the plywood for strength).  Has anybody installed this type of tank? How did you do the fabric on the butt end? 

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Posted

Just glue it to the top and bottom of the rib. No flight loads involved, no stress, just mainly cosmetic.

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Posted

Never seen an Avid done like that before.  Will you have enough room between the wing and butt rib when the wing is in place for flight?  Usually the fuel tank forms the end of the wing.  JImChuk

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Posted

Never seen an Avid done like that before.  Will you have enough room between the wing and butt rib when the wing is in place for flight?  Usually the fuel tank forms the end of the wing.  JImChuk

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Yes I assembled the tanks with the wings on the plane. The rear part of the wing ribs are original.

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Posted

My Mk IV kit came with a wing tank "upgrade" set. The wing root end of the tanks has a flange about 1" deep (on the top only). I extended the bottom of the first rib with a 1/8" plywood strip with gussets glued to the tank. Now considering gluing in some vertical braces up to the top flange so I can stretch the fabric over the butt end of the wing. The fabric will not be glued to the tank except for the plywood rib strips. ( I glued in carbon fiber strips under the plywood for strength).  Has anybody installed this type of tank? How did you do the fabric on the butt end? 

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I did mine that way too. One thing to remember when brushing the poly brush through is it will bleed through and try to glue its self to the tank so be careful. You don't want it to stick to the tanks in some spots and not the other. I guess one more thing you will have to put thicker seals under the gas caps otherwise the metal part of the caps will hit the fabric and the aluminum plates you need to glue the fabric to around the filler neck. One thing leads to another believe me.

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Posted

TJay got any pics?

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Posted

Are you sure your flaperons will fit on the rib tails?  The tank was the right width for the flaperon spacing if the rear ribs did not overhang the fuel tank.  TJay's kitfox used a narrower fuel tank then the Avid.  That's why the kitfox has a complete rib on either side of the fuel tank.  Kitfox tanks hold 13 gallons, Avids 14 gallons.  JImChuk

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Posted

I didn't change the rear parts of the original ribs, except one I replaced. I have clamped the flaperons to the ribtails. Looked fine. Book says don't drill and attach til after covering.

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Posted

As long as the flaperons fit you're good.  Double check that as you install the trailing edge aluminum.  That will lock the ribtails in place side to side.  JImChuk

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Posted (edited)

When you paint leave a 2-inch diameter unpainted area over the tank. This will allow light into the tank to make it easier to see fuel level as you look at the root end of the tank.  I actually cut a hole in the fabric at the root end of the tank just above the fuel viewing window.

I also made two fuel level marks. Five and ten gallon level marks with tail up and separate marks for tail down. 

I have the under chambered wings.

John M

Edited by skypics

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