Model IV wing tank repair DIY.

[4Hummer]

Wings have been taken home and prepped for surgery.

Cut lines, Hoping to avoid cutting threw one of the reinforcement ribs.

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Prepped and ready for surgery..
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This is what happens when you have diet high in ethanol

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It's a serious case of Ethanol-19

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Even the finger stainers were plugged.. How this was getting fuel I don't know, But so glad I decided to cut them open
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[4Hummer]

Dremel Multi Tool with the Diamond grit sanding pad for the win. This tool made short(ish) work of things. and doesn't clog up like sand paper

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Both tanks ready for some fibreglass repair

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[4Hummer]

Little trip to Aircraft Spruce.

EZ-Poxy I have to say is the nicest low odour. easy to use, easy to clean up resin I have ever used. Fuel and Ethanol safe.

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Fibreglassing a new lip to seal the top
Started by cutting 2" strips up some super thin plexi sheets I had. (Note the Fiberglass tape is 1" wide)
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Two layers of 1" tape on the Plexiglas
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EZ-POZY. did I mention how nice this stuff is?
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Lay Up.
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Needed more clothes pegs
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[4Hummer]

Had to let that set up overnight, I had the Heat in the garage on high (25c/77f)
Next we need to add a lip to the stiffener ribs you'lI have to cut threw

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Done:

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[4Hummer]

Here is the Tank sealer. (sitting on the cut out of one of the tanks.. )


Aircraft Spruce Part Number: 09-03477
https://www.aircraftspruce.ca/.../gastanksealer.php...
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Close up of the Ribs, I ended up leaving a fair amount of the old epoxy that was glued to the baffles, as it helps line everything up. (Removed all loose crap first)

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First Coat Lids
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Tank Bare.
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Tank 1st coat:
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2nd Coat; FYI it takes 2 Quarts to seal both tanks.
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[4Hummer]

Sanded off 1/2" of the Gel Coat all the way around the top of the tank, and the lid, This is to prep for sealing the lid back to the tank. A 1" Fibreglass tape will be glued to the top once the lid is glued down internally

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The Lid
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I mixed the epoxy with Micro Ballon's into a couple different consistency. 1st Coat Very thin to brush along the edges, 2nd a bit thicker to fill some of the voids. and 3rd extremely thick to re-glue the baffles to the lid.

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One Lid Glued down. Will need to wait a couple days before doing the other as I have run out of things to place on top to get that perfect seal.

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I'm pretty impressed with myself. One lid back on. (Weights removed)
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seams came out real nice too. This is after a bit of sanding
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Added a 1" top layer of tape over the seam. (might be overkill.... but...)
Tomorrow I hope to glue the lid on the other wing. Just need a hand moving it off the rotisserie, and putting this wing into it.

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[bbs428]

Very interesting thread. That is some serious work. Unbelievable the chunks that were in the tanks. Sure is looking good now!

All the best getting it all done.

[jrevens]

Re: gluing fabric to surface of the tanks... I'll throw this out - If your tanks have a perfectly smooth surface and are made & mounted such that the surface height matches that of the wing ribs, then gluing the fabric to it should be fine (probably done as Jerrytex described). If not smooth, and especially if the surfaces don't match the upper & lower elevations of the ribs, adding false ribs to the tank surfaces would seem to be the way to go, gluing the fabric to the false ribs & shrinking it the same as you do between ordinary ribs. That's what I had to do on my 7SS. Many of us mount the false ribs on small standoffs, matching the contour of the ribs & allowing the fabric to be laced to them with the proper technique, although I don't think that's absolutely necessary. I know of Mod. IV builders who laid down a layer of felt-like material over the tanks to insure that the fabric didn't stick to it or rub on it, and to insure a smooth surface. I also know that some (most?) do not even attempt to lace the fabric to those false ribs, and some even glue on "fake lacing" to maintain a uniform look.

[4Hummer]

In regards to spraying the Poly-Fibre system, Seems everyone says "It's the easiest paint system to spray" followed by "you need a $1500 + professional spray system setup to get a good paint job"

I have a small air compressor, which I don't think would cut it, add to that I'd need larger hoses, a water separator, filters, regulator and a HVLP paint gun, this all adds up. another option was the Turbine HVLP system buts that over 2grand Canadian. Seems like a lot of money to spend for a small fabric patch.

I took a chance and went a totally different route. (Warning this may offend the Nay Sayers)

AMAZON Neu Master HVLP paint sprayer. $108 Canadian.

https://www.amazon.ca/NEU-MASTER-N31...xpY2s9dHJ1ZQ==


This is a 600 WATT electric paint sprayer, super easy to clean, comes with 3 different nozzle sizes, has 3 spray patterns, and adjustable flow control

I built myself a test frame and covered it in fabric, After testing the different nozzles I determined the smallest nozzle (RED) sprayed best, and was actually very impressed with the results once dialled in

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I didn't take many pictures of the process, but I can ensure you this sprayer laid down the Poly-Brush, the Poly-Spray, and Poly-Tone extremely well.
plus its super easy to Clean,

Heres a picture just after applying the first coat of Poly-Tone
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Only thing I would do different, is recover the entire section of the wing, instead of just putting in a "patch", I have a few winkles under the tapes where to two fabrics where glued together, Overall however I'm extremely happy with the results,