Using insulating foam to "sink proof" a boat

[axel_ess]

In my model of the Moyie, I am considering filling the voids in the hull up to the level of the deck with insulating foam to keep the thing from sinking outright should it swamp. I was planning to do this after giving the inside of the hull a couple of coats of epoxy to waterproof the wood. I am speaking of the foam that comes in a spray can and is used to fill voids around doors and windows. Has anyone any thoughts on this?

[Khephre]

It's fantastic stuff but go easy with the amount you use. The can has two active ingredients which mix together on leaving the nozzle and expand by absorption from the air.

I built a dumb barge recently for tug towing competitions - squirted the aerosol foam you refer to into the voids at bow and stern...

... and watched as the decks bulged upwards and one side of the barge split off along the hard chines at deck and bottom. Live and learn!!!

That foam expands by 30 - 40 times - it needs to have plenty of headspace and somewhere for the excess foam to expand to - a decent sized overflow hole that can be filled over later. I'd only allowed a small hole to squirt the stuff in through and that clogged solid pretty fast.

Don't forget to have some acetone on hand to clean up before it goes completely off (and plenty of ventilation for using acetone too).

Good luck
Tony

[towboatjoe]

You have to have experience in using the spray foam or you'll blow your model apart. I have used it for years and wouldn't reccomend it for someone who hasn't used it before. The only time I use it is before I put a deck on so the foam can expand upwards. I then trim off the eccess with a large razor blade used in carpet work.

Your best bet is to use the sheet styrofoam used as basement insulation and sheeting. You can cut it to fit, it comes anywhere from 1/4" thick to 6" thick, and you can usually pick up cut off sheets at a construction site for free. It saves them the trouble of cleaning up and putting it in the dumpster.

If you do use the spray, don't put no more than 1/4 volumn in a void cause it will expand that much. Better make a couble small boxes and expriment. Better to destroy a box that to watch a hull explode.

[axel_ess]

Good point. I was going to experiment first as a friend of mine used it to insulate around a window and it expanded to the point where the window frame warped. I was thinking of putting it on before attaching the deck and cutting down the excess.

[Eddy Matthews]

Another point to note if your filling a large space is that the foam will set on the outside and remain liquid in the middle - Put your newly finished boat out in the sun or in the back of a hot car and watch it blow itself apart even 6 months after you've added the foam!  I've seen it happen - The best solution is to add very small amounts of foam, wait until it sets fully, then add more until the space is filled...

[steamboatmodel]

I have used the spray foam and the two part mix on a number of occasions and never again  : , one boat split one year after the foam was put in. The deck had been put on after the foam was installed and left to cure in the back of a HOT boiler room for one week. What happens is the foam skins over and prevents the centre from curing, then later small cracks develop in the foam and the inside then expands and cures. GO WITH THE SOLID INSOLATION :!:
Regards,
Gerald

[axel_ess]

You've talked me into it. Solid foam. Thanks for all the advice.

[scotfriend]

Hello axel_ess,

I understand why you will fill your model with foam, it is hard to lost a boat I know this very well, once I'have lost one without foam.

I never had the experience of the other paddleducks, but one point I don't like to fill a model with foam is, what happened when water came into the model. Sooner or later it is between the hull and the foam, then it start's to rot. What do you think how does your model smell after a few week's. Your have covered the hull inside with epoxy but water start's to rot without contact to the wood only in the foam.

[axel_ess]

Thanks for your thoughts.

This is why I was thinking of using expanding foam injected into the voids, it wouldn't leave room for the water, but it appears the risks to hull as a whole are just too great so  I have decided to use loose foam in the form of styrofoam packing peanuts with an access hatch to allow me to remove them and dry the hull interior in the event of a mishap.

No system is perfect where water leakage is concerned as I recently found out whne a torrential rain flooded my basement.