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Filling stall Warning Holes

lr172

Well Known Member
How did you guys fill the holes in the leading edge for the stall warning device?

I don't have access to the backside of the skin. When filling a hole like this, I like to get a bit of build up to hold the filler in place. If I press it in from the front, there is little likelihood of it hitting the backside of the skin. That leaves me with only .032" of adhesion.

I don't want to pull the fuel tank to get access. These are QB wings.

Larry
 
Mine were just left open Larry. I also have an AOA that has a hole in the top of the wing. No big deal, but if you really didn't want the holes now is the time to fill them.

-Marc
 
Pull the tank

I pulled the tanks to leak test them off the wing anyway. Actually, I pulled the tank twice because the first time I forgot to fill the leading edge holes!

It’s really not that big of a deal.
 
I didn't want to pull the tanks either, but decided that it was what needed to be done. Once I started, pulling the tanks wasn't that hard. It took perhaps 30 - 40 minutes per tank to remove and replace them. Then just inserted the rivets to fill the holes per the plans.

Better to remove the tanks now, before they are closed up and installed, then try to fill the holes with some type of mastic and find you need to pull the tanks to do it right 6 months after first flight.

Cheers,
 
My QB wings had an inspection plate on the bottom for access to the back side of the holes for stall warning install. If you end up taking off your wings to gain backside access, this is what I did on mine - rough up the skin a little on the inside with some 80 grit, lay a layer of wetted out fiberglass cloth over that area, and then on the outside squeegee on some epoxy/flox over the hole and into the wet cloth. Let it cure, sand to flush, and smooth with epoxy micro paste or metal glaze. sand to 600 grit wet and you'll never see it when painted.
 
Is it possible to 3d print a plug that could pop in? You my have to force it a bit.

Since the only knowledge I have of 3d printing is reading Steve's thread, this idea may be nuts. I doubt all the holes are exactly the same size so probably couldnt mass produce them unless they were made a bit bigger and people modified the hole to fit the plug. Just an idea.
 
If you REALLY don't want to pull the tanks you could use a pulled rivet. Personally, I think it'd be a bigger hassle to get the rivets from ACS and you'll feel kind of silly once you pull the tanks anyway for some other reason. Plus, even when filled, it won't look as nice as solid rivets.
 
Thanks for the input. I think that I will try some liquid JB weld. If I push it up in there while in the wing cradle, gravity should coat the backside and make it strong enough. I was thinking filler and not something more liquid.

Larry
 
Yeah...

The issue with filling the hole with rivets is that it is a curved surface. The rivets will give you a flat spot in the curve. Ask me how I know...
 
Couldn't you use a bent piece of wire or small Allen wrench to spread the JB Weld around the inside? If it were me, I'd do that then cover the hole with tape (Peel-Ply would be great!) to keep the JB Weld from draining out. I'd also mask off the area around the hole to keep the JB Weld from sticking to the leading edge when the tape spreads it out. (I'm assuming the leading edge is facing down.)
 
Tape a slightly larger area around the holes and slot with packing tape and then a strip of electric tape. This allows some build up tha can be sanded down. Press in the JB weld as mentioned. Make sure you don’t sand the JB weld off back to the aluminum. Just float it where you see a smooth transition, leaving a little material covering the holes and slot. Don’t forget each wing has the slots.
 
Filling stall warning holes in QB wing

I don't have an answer for doing it with the tank attached.

I pulled the tanks to test them and while off I filled the right wing rivet holes with a soft rivets. I had them for fiberglass tip work. Easy. It will require a little bit of filler when painted.

I also installed the stall warning kit on the left wing: Belt and suspenders.

Happy Building,
 
NAS1097 AD3 is a good solution

Use the very small oops rivets to do it instead that will avoid the flat spot. After a little sanding and scotchbrite on mine you can barely tell they are there: NAS1097 AD3
 
Couldn't you use a bent piece of wire or small Allen wrench to spread the JB Weld around the inside? If it were me, I'd do that then cover the hole with tape (Peel-Ply would be great!) to keep the JB Weld from draining out. I'd also mask off the area around the hole to keep the JB Weld from sticking to the leading edge when the tape spreads it out. (I'm assuming the leading edge is facing down.)

I tried this today. It is only a #40 hole and it didn't seem like the dental pick was getting much in there to work with and the squeegee'ing didn't seem to do it either. In the end I filled it as best I could then left a large blob over the hole. I then put on masking tape and pulled tight. I am hoping that forced a bit more in there and gravity spread it around internally. We'll see tomorrow after it sets up. If it's loose, I'll pull the tanks.

Larry
 
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