Flotation Foam

[2Dive4fun]

OK,

Quick question.....

I just purchased another boat. Yes, the wife knows about it.

The boat is a 1982, 21 foot Glasply. I have a real liking to these boats. This is my third one. On the 19 foot boats there is flotation foam filling the space between the stringers and floor boards. On my last renovation project the foam was wet and traped water that got into the cavity. I removed all the old foam when I rebuilt some rotten stringers and replaced it with new foam.

The 21 foot boat had a soft spot in the floor so I cut it out and found no foam in the cavity. I'm trying to determin if I should add foam or keep it as origionally designed. Glasply is a very strong boat and has a great reputation. The company is no longer in business, so I can't go to them for questions.

My thoughts...

The size and weight of the boat exceeds the flotation value provided by the foam and the boat will sink in the event of a hull rupture anyway.

The foam can trap moisture and impeed air drying the cavity.

Glasply had a reason for not foaming the boat; What would you do?

 

[Hank49]

The size and weight of the boat exceeds the flotation value provided by the foam and the boat will sink in the event of a hull rupture anyway.

The foam can trap moisture and impeed air drying the cavity.

Glasply had a reason for not foaming the boat; What would you do?

I thought the only reason for foam was to float the boat if it flooded. I was considering foaming mine (we have the capability here where I work) but came up with the same conclusion as you. I would have to route a 4 inch PVC pipe or something, to feed throttle/shifter, electrical, steering cables through, but that shouldn't be a big deal. I just have a high flow bilge pump and make sure its working.

 

[captain]

my error. see below

 

[captain]

The Coast Guard only requires manufacturer to put positve foam flotation in boats 20 feet and under. As you correctly assumed you may not be able to get enough foam in it to provide positive flotation. Also it is virtually impossible to keep foam dry. When it becomes wet and it will, it can add several hundred pounds to the weight of the boat, not good. Also it promotes rot in decks and stringers. If I were you I would not put any in.

 

[Tom Winters]

Glasplys were good boats but used styrene resins throughout. You could foam the voids if you totally sealed all the joints on the hull and barrier coated the hull with either epoxy or maybe a vinylester resin. This way, no osmotic water or water leaking through a bulkhead or seam. Done correctly, the foam would help with the integrity of the hull in pounding seas - you'd get a nice solid feeling pounder through larger offshore seas.
There are at least 4 different densities of foam readily available ranging from 8 pounds/cubic foot (super dense) to 2 pounds/cubic foot (light airy stuff). The dense stuff is great for embedding gas tanks - preferably cross-linked poly and NOT aluminum).
Some guys have cast foam blocks, sealed them impermiably with resin, and glued them up in voids for extra flotation. This way, the foam is never getting wet unless you get partitioned by an oil tanker.
Filling or not filling your boat can't really be decided in a forum - you need a good boat guy to take a look at your Glasply.