Teardrops n Tiny Travel Trailers

Hi all,

I've been dithering trying to decide on a skin for my little bicycle trailer foamie and came across this video https://www.youtube.com/watch?v=CKb6uEv0rDk for boat building.

I believe he's a commercial builder, and for these builds is using fibreglass cloth with tb3 over the hull of the boat for protection. He does comment that it's not structural, but there's "it's not really structural", and there's "I was going to use canvas otherwise, so...".

Locally for me, it seems like the majority of the cost of fibreglassing is in the epoxy, and less so in the cloth, especially if you compare a lightweight fibreglass to a heavy duck canvas. So this seems compelling to me, for both keeping down weight, not being too crazy on price, and also avoiding the smell and cleanup complexity of the epoxy.

But I guess I need to do some tensile and weight tests to know for sure. (Currently testing tb2 + kraft paper (!) as an "even-poorer" PMF as recently discovered on the foamies facebook group. At least one person seems to have had really great and lightweight results, though he did do 3 layers on the exterior and commented that it was quite labour intensive.)

That seems crazy to use wood glue with glass.

If you want to minimize the weight, use a lighter cloth. Muslin is cheap and lighter than canvas; i did the inside of my foamy with that.

Btw, I've been using kraft paper and water based poly to cover my RC airplane wings for a decade or more. The tensile strength to weight ratio is better than epoxy/glass. But I don't think it's as water proof even after painting.

Pmullen503 wrote:Btw, I've been using kraft paper and water based poly to cover my RC airplane wings for a decade or more. The tensile strength to weight ratio is better than epoxy/glass. But I don't think it's as water proof even after painting.

I'm still waiting on multiple-layer versions drying to run some tests, but it does seem to have added a lot of stiffness already with one layer. It's interesting that it's less waterproof though... I thought the paint was doing all of the work of waterproofing, but I guess it likely doesn't get absorbed as well as into fabrics?

One positive I notice about the kraft already is that on the flat surfaces it looks like if it were painted it would already be a nice finish (i.e. very minimal sanding required).

The key thing would be to avoid water sitting anywhere for any length of time. I wouldn't have a concern about the sides but the top if it pools or areas around the frame and doors could be problematic. I just rebuilt the bottom of my inset side door after 7 years. Enough moisture collected there to start to rot the wood frame.

I'd use oil rather than latex paint too in addition to being careful to make sure everything drains.

Pmullen503 wrote:The key thing would be to avoid water sitting anywhere for any length of time. I wouldn't have a concern about the sides but the top if it pools or areas around the frame and doors could be problematic. I just rebuilt the bottom of my inset side door after 7 years. Enough moisture collected there to start to rot the wood frame.

I'd use oil rather than latex paint too in addition to being careful to make sure everything drains.

Thanks for that suggestion, I was thinking at first a Marine Spar Varnish (though the "good" ones seem to want about 5-8 coats, bleh). Possibly something like https://flexseal.ca/products/flex-seal-liquid which I assume would be completely waterproof, though likely very heavy too. So maybe just an exterior oil paint is the way to go.

Pmullen503 wrote:Btw, I've been using kraft paper and water based poly to cover my RC airplane wings for a decade or more. The tensile strength to weight ratio is better than epoxy/glass.

I figured I should finish off an attempt at testing tensile strength testing after you mentioned this, and long-windedly wrote it up here just now: https://scot.tg/2022/09/26/foam-sandwich/ (The short version is that yes, paper seems to be very stiff, which is pretty neat to me!)

DO. NOT. USE. FLEXSEAL. In some of the groups I belong to, people have reported problems with it, saying its sealing properties don't last.

I've read about and seen videos of boats covered in fiberglass and Tightbond. They've been happy with it. How it lasts in the long run, though, is anybody's guess. My guess is that it'll do just fine.

I'm still wondering, why not use the real deal: epoxy?

There's no question what the results are. We put a great deal of labor into these projects and quite a bit of money...



Easy-peasy.

Tony

S. Heisley wrote:DO. NOT. USE. FLEXSEAL. In some of the groups I belong to, people have reported problems with it, saying its sealing properties don't last.

Thanks for the warning, will avoid!

tony.latham wrote:I'm still wondering, why not use the real deal: epoxy?

Thanks Tony, I'm sure you're right that epoxy would make for the best final product. Mostly I just thought it was interesting to look into simpler materials, especially if I'd feel OK about my young kids "helping" with their application.

especially if I'd feel OK about my young kids "helping" with their application.

Young kids and fiberglass/epoxy... what could go wrong?

Tony

Look at this YouTube https://youtu.be/1rERbgbv1Tk
Then go to part 7 and 8. He glues paper on the Styrofoam, then goes iver that with fiberglass and resin. Unless you understand Portuguese you will have to guess what he is saying.

He's using expanded foam which leave a rough surface after sanding so the paper makes it smoother base for the epoxy.