Plywood Pontoons

[sosky]

I bought a book with instructions on building a small wooden pontoon boat. Styrofoam is used inside the plywood pontoons. The book shows 4'x8' sheets of 2 inch Styrofoam house insulation cut to fit in layers inside the pontoons. Could shredded packaging foam be used?

 

[64osby]

I would think that the sheet foam would provide some structure to the toons, where shredded foam would not. Also is the packaging foam closed cell like the foam that the big box stores sell. Closed cell will not absorb water.

Welcome to iboats.

 

[sosky]

It's like the Styrofoam used for those white coolers

 

[HotTommy]

Sosky,
Think of it this way. If the wooden pontoons were both structurally strong enough and water tight, you wouldn't need to put anything inside them. The fact that the plans call for the styrofoam sheets indicates they may be needed to keep the sides of the pontoons from collapsing inward, and they may be needed to keep the boat afloat when water gets inside. That means closed cell foam is the way to go.

 

[GA_Boater]

It's like the Styrofoam used for those white coolers

Junk, sosky. Many boat mfgrs. in the 1960' s used styro for floatation and all of us who have rebuilt a boat from that era it find it's water logged and falling apart. Spend a few extra bucks and buy the pink or blue closed cell insulation board from HD or Lowes.

Welcome aboard.

 

[Stumpalump]

A lot of packing peanuts are biodegradable and melt in water. I think you can even eat some of them.

 

[sosky]

Thanks for keeping me from making a big mistake.

 

[jbcurt00]

Dont ask me about packing peanuts, ugh uke:

Added bonus: removing spray on bedliner

Good luck w the `toon project sosky

 

[Rickochet]

I built a plywood pontoon boat back in the 70's using Glen L Marine plans. I found a plant about 100 miles away that made foam sheets and blocks. I bought of trailer load of their "cut offs" for very little and fit it inside the toons. What about filling the pontoons with empty milk jugs? You could probably buy new jugs pretty cheap.

 

[GA_Boater]

When a few closed cells in foam rupture, it's not that big a deal. When a milk jug or one big cell ruptures, it could be a big deal.

 

[Grandad]

I wouldn't recommend using anything less than the closed cell foam (pink or blue stuff) and definitely not in peanuts form. As long as the foam sheets are carefully cut to fully fill the voids inside the pontoons, you'll get the maximum flotation. Without actually knowing, I'd estimate that the space between the peanuts might be 40% of the volume inside the pontoon that could potentially fill with water. Same for noodles and plastic bottles. I expect that the pontoons are sized just adequately to do the job if no water enters them. And before someone suggests that the seal on the outside of the pontoons is sufficient, then why would there be a need for flotation material at all, except perhaps as HotTommy said for structural integrity. - Grandad

 

[64osby]

To fill the toons with foam and ensure structure, then pour in foam would be an optimum solution. Yes, it would be expensive.

 

[jbcurt00]

What is the plan for sealing the plywood used for the pontoons?

Epoxy w cloth, epoxy, WOGs old timer 'recipe', spar?

 

[sosky]

Epoxy with cloth

 

[garveyvenanzoni]

nice

 

[jbcurt00]

If you plan to use epoxy and cloth, I have an alternative method to fabricate your pontoons.

Just use the rigid foam instead of plywood, fill the inside w rigid foam too.

Covered w epoxy and cloth, they'll be strong and rigid plus no wood that will rot if theres a nick or scratch thru the glass layer.

 

[GA_Boater]

tpenfield built a 8 ft. or so dinghy out of glass over cut and formed foam sheets. He did really nice work and turned out a good looker.

As JB said - An alternative to using plywood for the logs.

 

[garveyvenanzoni]

I thinks that you should follow what the book says. Styrofoam is intact, unlike the shredded packaging foam. If it says that there should be something between the pontoon and the plywood, then most likely, something shredded and ripped to pieces isn’t a really good idea.