Alternative to foam

[Stoutcat]

Just a thought...

Suppose in certain rebuilds, we don't use foam for buoyancy or rigidity. Maybe we use air chambers and ribs instead. (I searched this forum, and I believe Opps talked about this. I also checked the CG regs and they talk about air chambers.) The air chambers would be readily accessible via deck plates or inspection plates and still be water proof. Check out the masterpiece below...

If you picture the deck made of see-thru Plexiglas, it almost makes sense...

Yeah the deck plates would cost extra, and yes, it would be a hassle. But I'm 50 years old and facing a rebuild with my brother now. The last thing I want to do is face rotting stringers and saturated foam when my brother and I are in our 70s and we just want to cruise off into the sunset.

Anyway... I've put waterproof deck plates in the wife's kayak and we love them. After every trip out, we unscrew the plates, make sure all is dry, and let the air circulate.

Air chambers/ribs provide plenty of redundant flotation, structural support, eliminate the chance of rot, offer "slim" storage, etc.

What am I missing?

Alan

 

[tashasdaddy]

Re: Alternative to foam

some people use 2 liter soda bottles under the deck. the problem is keeping a sealed space sealed.

pontoon boats work on the same principle. they are sealed tubes. but as they get older, a lot of the will get small leaks. you have to have a way to pressure test these. i have a 21 year old toon, i take on about 1 gallon of water in 8 hours on one tube, and about 7 gallons in the other tube. all of this is a drop in the bucket, considering the tubes are over 500 gallons, in volume. but i keep track of it, so i know if it gets worse.

 

[salty87]

Re: Alternative to foam

i think your time would be better spent designing a way to let any water out that gets in...drainage. foam is great stuff when it isn't left in water for years. let the water get out and the foam will stay dry. this implies that you don't just pour the foam into the hull sealing everything off. i lined my hull with plastic when i poured foam. after the foam sets, pull the plastic up and a foam block will pull up. peel the plastic off and drop the foam back into its' compartment. water will bead up and run off into your drainage system that leads to the bilge pump. limber holes thru stringers (sealed very well) let water into the bilge to get pumped overboard.

 

[Stoutcat]

Re: Alternative to foam

Hi Salty 87,

I like the idea of drainage, but I worry about the structural element of your plan... If the foam isn't allowed to adhere to the stringers and the hull, won't that weaken the boat?

Alan

 

[tashasdaddy]

Re: Alternative to foam

in most cases foam is not structural.

 

[Stoutcat]

Re: Alternative to foam

Hi TD,

You nailed it. How do you keep a sealed space sealed? The simple fact is that you can't. I don't care what all the poly and epoxy companies say... Sooner or later, water is going to find a way into a sealed space; when all is said and done, water is more slippery than buttered mucous.

But at least with air compartments with waterproof hatches, you can inspect, dry, and ventilate.

I know that this approach wouldn't be cheap, but I've reached the point where I'm willing to save a year for a solution I won't have to worry about down the road.

As for the pontoons... I'd empty the toons as best I could, then coat with a soapy water and put the rig back in the water and pressure test and look for bubbles.

I'd then use something like the following to address leaks...

• Alumaloy
• DuraFix
• HTS - 2000
• JB - Weld

Alan

 

[oops!]

Re: Alternative to foam

stoutcat.....one way of doing it is just a wee bit different than the pop bottle idea......there are sever types of plastic containers that can be incerted into the air chambers you are building.....any thing from a commercial milk bag...to an innertube....these could bi inflated and de flated for removal and inspection purposes......just make sure that your hull is thick enough that it doesnot recuire the foam for rigidity.....(as td pointed out...this is only nessary on a few boat designs)

there is also another idea that was presented on the forum......foam the underside of the cap !......add a 6 inch layer to the entire cap.

it would allways stay dry.....its not trapping water and holding moisture to the strings.....and if the boat get swamped it will not flip so the survivors actually can sit in the boat and wait for rescue

 

[Stoutcat]

Re: Alternative to foam

Bingo!

Oops, I think you called it! I've always worried about flotation low in the boat in that as the boat sinks the below-the-deck flotation will have a tendency to make the boat want to turn turtle.

It would be easy to put in the minimal internal ribs (sans foam) to give the craft the needed rigidity (per TD), give the boat the drainage Salty was talking about, and put the flotation under the cap, I think we have a winner!

Gotta love this forum...

Now if I can just get my brother off the sofa...

Alan