Low Profile and Drag Pop Top Wedge Foamy+PMF on a 5x10

[KCStudly]

I think you will have problems with the water-based glue and glass, especially when you scale up. I wouldn't expect that it can properly saturate before starting to skin over, especially in less than ideal temperature and humidity levels. If the glue skins over the foam is not absorbent like wood and won't give the moisture under the skinned over part anyway of drying out. I had a similar failure using PL300 attempting to laminate foam, it just never cured. So wasting a $30 piece of glass to save $30 on epoxy is a false economy, in my opinion.

I had several very experienced builders suggest that I just go straight to epoxy on my build and I dinked around using glue at first. When I eventually "saw the light" and switched to epoxy, I ran into some issues with compatibility making me sort of wish I had listened to the advice sooner. Just saying, if you're going to use glass, use epoxy. If you want to use glue, maybe better to stick with canvas.

 

[kipa]

But I digress. I think you have your mind made up.

Tony

If only . . LOL.

I am of two minds: Build it fast and cheap to prototype the design and figure what works and doesn't, or do it all right the first time which is an obvious fools errand.

 

[kipa]

I think you will have problems with the water-based glue and glass, especially when you scale up. I wouldn't expect that it can properly saturate before starting to skin over, especially in less than ideal temperature and humidity levels. If the glue skins over the foam is not absorbent like wood and won't give the moisture under the skinned over part anyway of drying out. I had a similar failure using PL300 attempting to laminate foam, it just never cured. So wasting a $30 piece of glass to save $30 on epoxy is a false economy. in my opinion.

I had several very experienced builders suggest that I just go straight to epoxy on my build and I dinked around using glue at first. When I eventually "saw the light" and switched to epoxy, I ran into some issues with compatibility making me sort of wish I had listened to the advice sooner. Just saying, if you're going to use glass, use epoxy. If you want to use glue, maybe better to stick with canvas.

That's a solid point. Dry times for the first mat layer are very long, but it saturated completely through far easier than I expected. It soaked it up like water to a sponge and flooded the facing of the foam. So what was left to squeegee off the top was all excess.

I'm not convinced it is fully dried even now after two full days, but that is also why I cross cut through it. I couldn't detect any wet glue at the cut, or on the cutoff piece when I separated the mat from the foam - which pealed up foam when I did. If I were to take it full scale, I'd give the first layer 2 days of drying time at a minimum.

 

[Pmullen503]

I've covered a lot foam with fiberglass cloth and water based polyurethane (Minwax) for RC airplanes. A couple things. First, it really doesn't soak into foam (that's why I use it) and second, it takes days to fully cure. I weigh the parts and can see the part getting lighter for a few days.

The point is, for a thick lay up using water based adhesives, maybe wait a few days between layers/coats.

 

[kipa]

I think the way I am going to start this build is to keep the experimenting small with the tongue box. I'm going to try forming prefab FRP panels and Sika post hole pour foam to make simple curves very fast and easy with proper forms. That should create a solid very strong structure rapidly and could be fully built to be used in just a few hours.

The same technique could possibly work efficiently for the lower supporting wall strength as well and would allow me to avoid having to worry about adhesives curing completely.

I'll save the ACM panels for lighter duty areas that are unlikely to get much contact abuse, if I use them at all.

 

[Tony Latham]

and Sika post hole pour foam to make simple curves very fast and easy with proper forms.

Make sure to share your progress with some photos. That's got my curiosity.

Tony

 

[kipa]

Comparing cost differences and required structure strength, I have decided to fiberglass everything I can. I only want to do the sealing once, and removing PMF/resealing with epoxy after the fact seems like even more work than just starting over. Appreciate all of the comments so far!