epoxy failure

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builderwannabe
Posts: 9
Joined: Mon May 13, 2019 8:05 pm

epoxy failure

Post by builderwannabe » Mon Oct 28, 2019 6:07 pm

Has anyone ever had T88 epoxy fail? I ask because yesterday when i stepped into my pietenpol for the first time to sit down i heard a pop and crackle. Upon closer inspection after getting out it appears that a section of about 3 inches of the floor came unglued from the cross strut that is holding up the front of the rear seat. It is possible that i put my heel(which holds up 200 lbs) too close to the cross strut when getting in. In addition when I glued this cross strut in I could not determine which orientation to put it based on the plans so turned it so that the shorter edge was being glued to the plywood(cross strut is 1/2’ x 1’). This means that a much smaller surface area of glued wood is holding me up. That explanation plus a possibility that I may not have put enough epoxy on there in the first place is what i have come up with. The rest of the glue on that piece did not fail though so that is why i have gone with my explanation. Does anyone have any other insights or similar experience?

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taildrags
Posts: 283
Joined: Tue Mar 07, 2017 10:39 pm

Re: epoxy failure

Post by taildrags » Mon Oct 28, 2019 10:08 pm

Let me try to understand which member you're referring to. The crossmember that secures the bottom edge of the pilot's seat is also the aft pivot mounting point for the aileron bellcrank beam that links the two control sticks. Where it mounts to that crossmember, the pivot bearing has two bolts going through the steel strap, the crossmember, and the floor. Were those fittings not in place at the time? Because if they were, then you have not bolted everything through the floor. See picture, which is Chris Tracy's Air Camper and it appears that he has laid that crossmember with the 1" dimension down flat.
05260001.jpg
Sorry if I've gotten this wrong, but I'm trying to picture where you stepped and what it was that let go.

Oscar Zuniga
Medford, OR
Air Camper NX41CC, A75 power

builderwannabe
Posts: 9
Joined: Mon May 13, 2019 8:05 pm

Re: epoxy failure

Post by builderwannabe » Mon Oct 28, 2019 10:12 pm

correct crossmember but i have not done anything with the controls yet so there are no bolts through the floor.

Stroid
Posts: 7
Joined: Sun Sep 15, 2019 3:51 pm

Re: epoxy failure

Post by Stroid » Wed Oct 30, 2019 10:32 am

Yes I have had epoxy fail on my wood minimax. Hard landings, stepping on the wrong spot like you did etc. Im not a big fan of the wood/epoxy. I like metal fasteners myself. But then Im pretty rough with my planes doing stol flying. I really wish I had the steel frame instead. Oh well.

Tools
Posts: 18
Joined: Wed Feb 22, 2017 9:22 pm

Re: epoxy failure

Post by Tools » Wed Oct 30, 2019 5:24 pm

Another consideration is too much clamping pressure, which can displace too much epoxy, the more common way of not having enough.

Tools

builderwannabe
Posts: 9
Joined: Mon May 13, 2019 8:05 pm

Re: epoxy failure

Post by builderwannabe » Tue Nov 12, 2019 6:06 am

Thanks for all the input, I don’t feel as bad as I did but only somewhat. It’s a good lesson for the rest of the build.

Sean

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