Will saran wrap hold back 2 part polyurethane foam expansion in a tube with many1.5 inch drill holes

Hello, i have an 8 inch pipe x 7 foot with many 1.5 inch drill holes and i want to pour 2 part polyurethane foam into the pipe and to keep the foam almost contained, am thinking of wrapping the pipe with saran wrap, but at the same time hoping the foam expands just enough to expand flush and actually a bit more with the surface of the pipe so i can then sand the foam flush with the pipe. Will then apply some fiberglass cloth over the pipe. So in essence, i'm hoping the saran wrap will expand just enough to allow some foam to expand past the surface of each drill hole. I experimented with some of that Great Stuff foam in a can and it pretty much just expanded up the tube and didn't push laterally through the drill holes as much as i hoped it would. Bottom line is i'm trying to create some pontoons for a canoe and had to drill the holes because the weight of the 8 inch gray schedule 40 pvc tubes is too heavy.

 

If you’re looking for light weight, eliminate either the foam or the tubing.
That looks like pipe, methinks you want a thin wall tubing instead.
Why does the foam need to be exposed outside of the walls?

 

good point because the main reason i'm adding the foam is to make for a smooth curved surface by filling in the drill holes and then apply the fiberglass cloth to the pipe, but now that you mention it, maybe the fiberglass with smooth itself out over the drill holes, but if not, the fiberglass will look uneven spanning the drill holes. Hmmmm so maybe there's another way i can create a smooth curved surface over those drill holes, good point

 

What I’m trying to say is that the empty sealed pipe alone will float better than a foam filled pipe.
If you want a cylindrical foam hull wrapped in fiberglass, use the pipe as a mold for the foam, then discard the pipe, shape the ends, and fiberglass the whole thing.
No, Saran Wrap won’t hold back expanding foam.

 

ok yes i agree with the foam only approach and i have a backup plan to glue, cut and shape some of that foam board with a vertical plywood center beam like someone posted an example on a previous post, but before that i'm going to try and make these pipes work if possible and so now i'm going to try and find a way to fill those drill holes with some lightweight material to make a temporary flush rounded or curved surface so the fiberglass cloth will look smooth. For example, maybe i could inflate some kind of inner tube of some kind that would press up against the drill holes and then shoot some great stuff foam over that, sand it down and that might be just enough to allow the fiberglass to laydown smooth. Here's what i'm going to start on this winter for sure, but for now going to try and make these tubes work somehow: Foam and Fiberglass Ama Construction https://amaconstruction.blogspot.com/2021/02/foamand-fiberglass-ama-construction.html

 

Gary Dierking, in his book, "Building Outrigger Sailing Canoes", has a section on foam and fibreglass amas starting page 103. Archive has a copy available for "loan", but the book is a wealth of information and well worth having.

 

yes exactly, i'm going to use Gary's plan for building those pontoons and have already started clearing space to start on that project as it makes total sense, so its good to have a long term better plan, thanks for the reference!

 

ok i was able to bow and shove some aluminum flashing into the tube and it gives enough of a backing to shoot some great stuff into the drill hole, so will spray that flashing with some kind of non stick spray and actually having a bit of a gap in between the flashing and drill hole gives it a bit more of a plug, so this may work, thanks kapnD

 

Holy canoly man, how complicated and expensive can you get? Pick one material, not three or four to cobble together.
Product Listing PVC-PIPE-Class100 at FlexPVC.com https://flexpvc.com/cart/agora.cgi?p=PVC-PIPE-Class100&xm=on

 

yeah i know and basically i'm trying to make lemonade now that i realize i've got a lemon, so its either try to make this work or take it to the dump hahaha

 

Maybe you should go back to basics. What makes you thing a canoe needs pontoons? I have been canoeing for about 56 years without pontoons and haven't had a problem. This includes ocean canoeing.

 

very good point, i'm starting to question that myself as its keeping me from getting out on the water, but i've got that Expandacraft sailing canoe stuck in my mind with a deck area on the sides, but that's a very good point, but this winter i'm still going to build that foam fiberglass pontoon, but well i guess an employee at the marina said he wouldn't go out on the James with anything less than a 19 footer because of the wind and waves at times and i guess i'm sort of thinking worst case, but yeah this particular project will probably end up like a lot of other boat flop stories i've heard about hahaha

 

Capsize the canoe and practice recovering. It is not difficult. We had a gang of about 5 canoes and 8 dinghies when I was a kid. We spent days capsizing each other.

 

You are now pointing out to me how the project should be done, but you’re still hell bent on doing it wrong?

 

yes i know and going to remove as much material as i can and give it one last shot before eventually probably taking it to the dump and the insult to injury is that i will probably have to pay to dump it, but here's what i'm trying to build, similar to this expandacraft rig