Fiberglass Emp Tips

I know this has been asked lots of times, but I can't quite find this answer. I've decided to tackle the emp tips while waiting on the weather to warm up for the canopy.

I used insulation foam board to block in the tips and covered and shaped with West Systems 410 micro and resin. I'm quite happy with the shape and gaps of the elevators and HS.

My question is do I need to put a layer of glass over the micro or will a glaze or resin suffice? I plan to wrap someday if that makes any difference. Pics below, thanks for any advice.

If it were my project , I would put at least two layers of 6 oz cloth in the mix.

Endlessly debated.

Did you rivet the tips into place with wet epoxy in the aluminum-to-glass overlap? If yes, you are (IMHO) good to go as is.

If not, well, a ply of exterior glass cloth can't hurt....if you keep it light.

Keeping it light is the key issue here. You'll fully balance the elevators (separately) after paint, so you'll have an opportunity to compensate for filler/glass weight behind the hinge line. Still, weight is weight.

The rudder is a different story. Your -7 wedge rudder already has a more rearward CG (i.e. is more under-balanced) than the folded trailing edge rudders used on earlier models. There have been some inflight losses of RV-7 vertical tails. There is no clear explanation, although overspeed is known or suspect in all cases, with flutter highly likely in one case and suspect in others. The accident report for the known overspeed/probable flutter case (from Canada) points to excessive application of filler as a possible contributing factor. Nuff said.

I did not have epoxy in the overlap, but I did proseal an aluminum rivet strip inside the tip to give the rivets something to bite.

If I put on glass cloth, it will change the gap spacing. If that is the cost, what is the benefit of putting on the glass? Does the micro have a tendency to flake off or something without a glass overlay?

Thanks, all.

BLittleton said:

I did not have epoxy in the overlap, but I did proseal an aluminum rivet strip inside the tip to give the rivets something to bite.

If I put on glass cloth, it will change the gap spacing. If that is the cost, what is the benefit of putting on the glass? Does the micro have a tendency to flake off or something without a glass overlay?

Thanks, all.

Click to expand...

Often, the micro will crack unless the tips are glued and riveted or there is a layer of glass over the joint.