Don't make this mistake

[rodsmith]

Aileron.JPG Sprayed the top coat on my ailerons yesterday and discovered a problem that goes back to the initial covering technique I used. I used a single piece of fabric wrapped around the flaps and ailerons with a 2" glued overlap and 3" tape on the upper leading edge. So far so good. What I didn't do was glue the fabric to the rest of the aluminum leading edge top or bottom. Didn't think that would present a problem as the fabric would shrink tight against the aluminum. The first coat in the stewarts system is diluted glue brushed through the fabric and I thought this would further help adhere the fabric to the aluminum. This seems to have worked fine and is no issue except the aluminum on the bottom of the aileron leading edge. Turns out this area between the leading edge and the aileron spar is concave, about 1/8". I didn't realize that and may not have realized the implications if I had. I noticed when brushing the diluted glue coat on that the fabric wasn't totally adhering to the aluminum but didn't understand the implications. Sprayed and sanded the 3 UV coats and everything looked fine. Sprayed the silver metallic top coat and due to the reflectivity you can see where the fabric is and isn't adhered to the aluminum, aesthetically it looks awful. I don't see this as a safety issue, long term if it vibrates enough in that area it might cause deterioration. Fortunately it isn't in the prop wash. It seems to be about 1/32" proud of the aluminum. If anyone thinks this could be a safety issue please let me know. I've gone through a range of emotions over this. This morning I was determined to cut it all off and start over again. Then I reminded myself this isn't and wasn't supposed to be a show plane and it isn't like there isn't going to be any other cosmetic blemishes. My point in writing this up, is be sure you glue the fabric to the aluminum in this area. If doing it over I would put a coat of glue on the aluminum and let it dry before installing fabric, then iron the fabric into the glue. Use the necessary technique for the system you are using.

[marcusofcotton]

Thanks for the heads up.

[Nev]

Appreciate the heads up too.

[AZBearhawk272]

Rod
Been there, did this.
Arthroscopic gluing.
Poke a 1/4 hole in the center of the area through the fabric only.
Dilute a glue solution and put it into a reasonably large syringe.
Inject the solution into the cavity and rub to displace all over the area. Just push and smoosh.
Then work as much of the excess back out the hole as possible.
After 15 min or so stick the shop vac over the center hole and suck for a bit. Then iron down from outer edges working toward the center.
Apply Quarter sized patch over hole.

just make a training sample out of a piece of AL with fabric folded over the edges.

Kevin D

[rodsmith]

I had thought of that, then dismissed the idea, concerned about getting the glue evenly spread. Will take another look, will require more than one hole as the unattached areas aren't continuous.

[jaredyates]

It has been a while, but as I recall, the polyfiber method would call for sticking a stitching needle in, working parallel to the fabric, and scrape the fabric loose where it is being held down against the aluminum at any point lower than the outermost plane. This would typically be done pretty early in the process, before taping, so that the holes would be covered by tapes. But if you did it now, you could add a patch. There is a demonstration on the polyfiber video, which I can try and find if this doesn't make sense.

[svyolo]

I would try injecting glue first. If it doesn't work to your satisfaction then recover. I would bet it works just fine. I have never done this on an airplane, but was going to suggest it. I have done it on a variety of oddly different things, including a horribly done "back butter" tile job. I spent two days injecting mortar into voids. But it worked.

You might even try some large diameter medical needles so you can "aim" the glue in the direction you want. Sort of like horizontal drill for oil.

[interstate al]

I didn't glue my LSA ailerons on all of the aluminum either. They have two cross cotes, one brushed and one sprayed and don't look anything like yours? However I can see a few spots that are loose but nothing that I will worry about at this stage of the game. I did re-watch the Stewarts video where Dan is covering the Citabria aileron. No where does he mention gluing all of the aluminum, only the 2" overlap and the 3" tape, which is what I did too. Also he doesn't mention diluted glue in this video? Am I missing something new with the diluted glue? Or is this just another covering option?
Thanks for the heads up Rod!

[rodsmith]

Al, sometime ago Stewarts changed their procedure for the first coat of fabric filler. They used to recommend brushing the first coat of ekofill into the fabric using a foam brush, followed by sprayed coats. Now they recommend diluting ekobond, adding one part water to 3 parts glue and brushing that through the fabric with a foam brush as the first coat, followed by sprayed coats of ekofill. Apparently that works better to encapsulate the fabric. Not sure what you mean by yours doesn't look like mine. The aileron has the silver metallic top coat on it and picture was taken late on an overcast day.

[interstate al]

Rod, I was referring to your visible air pockets. What I ended up with are not as severe as what I'm seeing in your picture. I covered my control surfaces two years ago but still have the fuse to do so really glad for the information. My Stewart videos are 4 or 5 years old so will get on the Stewart website and check out the new process in detail. Hope to be covering the fuse in a few weeks? Thanks again for the info!

[rodsmith]

Understand now. I watched the Stewarts fuselage video and got some good pointers before doing mine. Overall I was very happy with the way my fabric work came out.

[Battson]

IMHO, this won't be a problem long term. No need to try and fix it.

1. Once you have colour on, you won't see it as much - silver would make a supermodel look ugly if you sprayed her down. It shows all flaws.
2. That fabric is under tension, the drumming of flight and time will probably allow it to release and sit more naturally.

Go forward and build, never-mind all the issues which silver shows up. They disappear again. I wasted days of sanding and respraying...