Epoxy Wipe

[macleodm3]

As I understand it, we add peel-ply to a wet layup, then rip it off (the peel ply hopefully) when its all cured. This gives us a surface that we can easily bond to with additional layup or whatever it is that the plans call for.

 

I have seen another, easier method that I'd like to use if its widely accepted in our building community. This method is to add peel ply with a "swipe of epoxy", after the initial layup has cured. This could be done months after initial cure, for instance during fuselage assembly with fresh peel-ply on the bulkhead edges or fuselage side joint areas. My only concern is that we're adding epoxy to an unsanded and cured layup.

 

I think this method could be a big help for me, and also help prevent sanding into glass. Any opinions? Has this been discussed lately?

[Phil Kriley]

I've never heard of anyone doing that, and I don't understand why you would want to. Epoxy is heavy and expensive. I peel-ply everything so that my sanding is minimal.

[TMann]

Uhhhh .......... your're on your own on that one Andy.

The idea is to increase the bond between thwo layups. I can't help but think that you have increased the bond between the swipe and the following layup but not between the swipe and the original layup.

 

If you miss the peel ply then sand (or sand blast.) I usually peel ply AND sand when I can.

[Jon Matcho]

This method is to add peel ply with a "swipe of epoxy", after the initial layup has cured. This could be done months after initial cure...

I am assuming "swipe of epoxy" means "paint thin layer of epoxy on surface" and then you add the peel ply. The issue is that you need a rough surface for the new epoxy to bond to (thus why we need to sand or use peel ply in the first place).

 

I actually have done (I think) what you're describing (to clean-up something mainly), but only after sanding.

 

...for instance during fuselage assembly with fresh peel-ply on the bulkhead edges or fuselage side joint areas.

I assume you mean "on the face of the bulkhead, near the edges" (and not the edges themselves). Sorry, for reasons above, you need to sand or use peel ply in the first place. I peel plied most of my bulkheads completely (once I realized it would be good to do so). I don't peel ply everything though.

[macleodm3]

I'll have to agree with you guys that the epoxy swipe and peel method, as I've described it, isn't a good idea for a strong bond. I've seen it on builder website(s) and was trying to figure out how it could possibly work for fuselage assembly.

 

For me, I don't use peel ply for the weight savings, but for the sanding issues involved with sanding bare layups.

 

I'll pm the person soon who's website mentions this and see what the idea behind this is.

[argoldman]

epoxy does not bond to cured epoxy. As a matter of fact, cured unsanded, unpeel-plyed epoxy is a reasonably good separating medium. If you peel ply directly after the origina uncured layup, you will save time, weight and the heartbreak of paint job psoriasis ()that may result if you use the post cure epoxy/peel ply technique.

 

Rich

[macleodm3]

I talked to the originator of this idea, and its quite different than the explantion I gave.

 

The idea is simple. If you're going to make a micro fillet and let it cure before you apply your glass layup, you might as well peel ply it to reduce sanding the micro (and possibly foam too). For areas that a builder wants a cured micro fillet, this seems like a good idea to help avoid accidently sanding into the bare foam while sanding (in preparation for layup) the cured fillet.