Is foam insulation below deck of aluminum boat necessary?

[jimpittman]

The previous owner installed 4 layers of 1" foam sheeting below the aluminum deck of my 16 foot aluminum flat boat. It is between the ribs. I want to lift the deck and clean the inside bottom of the boat. Should I re install the foam sheeting. Someone told me this is a hazzard as the boat could flip if it is filled with water while fishing and I should remove it.
What is the best thing for me to do?
jimpittman

 

[oldjeep]

Re: Is foam insulation below deck of aluminum boat necessary?

Foam in small boats is usually there to keep the boat from sinking to the bottom if it fills with water.

 

[JB]

Re: Is foam insulation below deck of aluminum boat necessary?

Yup. When he put it there it ceased being insulation and became flotation.

If the boat is swamped the foam will keep it afloat, but it would theoretically be easier to capsize.

Which would you prefer, capsize or sink?

 

[jigngrub]

Re: Is foam insulation below deck of aluminum boat necessary?

Which would you prefer, capsize or sink?

That's not a very hard question for me, I'll take an upsidedown boat over a boat sunk to the bottom any day. An upsidedown boat could save your life, the only good a sunken boat would be is new fish structure.

 

[jimpittman]

Re: Is foam insulation below deck of aluminum boat necessary?

OK it stays in. Never thought of it that way.
thanks
jimpittman

 

[fleachili]

Re: Is foam insulation below deck of aluminum boat necessary?

...... it would theoretically be easier to capsize.

Pardon my ignorance, could you explain please?:redface:

Thanks

 

[EddiePetty]

Re: Is foam insulation below deck of aluminum boat necessary?

"........of my 16 foot aluminum flat boat...."

Most 16 foot aluminum flat boats that I am familiar with (especially with bench seat) already have foam insulation under the seats in a sufficient volume to keep the boat upright should it be swamped. If this is the case with your hull, I see no reason to retain the additional foam other than sound dampening.

 

[JB]

Re: Is foam insulation below deck of aluminum boat necessary?

Pardon my ignorance, could you explain please?:redface:

Thanks

With the floatation below the water there would be a tendency for the foam to want to be on top. The only way it could do that would be to invert the boat.

Eddie makes a good point. If there is foam in the seats, too, I think the boat would float upright.

 

[fishrdan]

Re: Is foam insulation below deck of aluminum boat necessary?

The previous owner installed 4 layers of 1" foam sheeting below the aluminum deck....

It could have been the manufacturer, Starcraft used sheet foam for flotation and I'm sure others mfg's have.

 

[sschefer]

Re: Is foam insulation below deck of aluminum boat necessary?

It is a requirement that all boats under 20' be capable of achieving level float. Level float means not capsizing and the manufacturers have to prove that it will not do that. If your foam has been replaced there is little guarantee that is still capable of achieving level float. In fact, it's unlikely that it's been re-tested so there's no guarantee that it will float at all in a fully flooded state.

Here's the irony. Owner builders are not required to meet the level float requirement so the day the original foam was removed by the owner it was no longer required. You can leave it out if you want or you can put it back in and have some sense of hope that your boat will float long enough for someone to effect a rescue.

 

[oops!]

Re: Is foam insulation below deck of aluminum boat necessary?

another sure fire way to keep the boat upright in case of swamp is to foam under the rub rail cap.....in most alum boats this space is just an inch or so, if any

but if its there.....the boat will stay upright. (this is assuming that sufficient flotation foam is in the boat to keep it afloat.)

your boat has allready been restored and more than likely a new deck has been installed. (the sheet foam is not factory,,,,but a home builders remedy).
i am wondering why you want to get in there and clean ?...a simple thru hull hatch....or (more than likely the deck was just screwed to the stringers) just pull up a section and hit it with a pressure washer.

the proper foam for any boat is a two part pour in foam......this foam serves three purposes...

1. flotation.....it is uscg rules that any production boat has flotation foam in case of swamp.
2. anti crush of the hull due to the strength of the pour in foam. the pour in foam will actually make your hull stiffer and stronger...making it less likely to dent.
3.sound deadining.... this stuff works miracles when it comes time to quiet your loud motor in an alum boat (not as much in your case with an ob setup)

the problem lies in the fact that the foam over time will hold water if enough water is left in the boat and allowed to sit for long periods of time.
this is compounded by the fact that when water gets into the boat by a leaky hull or hole......the factory foam traps the water....and does not allow the water to gush in. (kinda like putting duct tape over a hole. it stops the leak right there and then.
but the water will eventually weep into the foam...waterlogging the boat.

more than likely...the po found his boat getting heavy.....and tore the deck up and found wet foam.....took it all out and went to the sheet kind of house insulation because it would not allow the water in it.....

the water intrusion is actually your main concern......i am POSITIVE that you have more than one leaky rivet....thus allowing the water in the boat in the first place.
if you do pull the deck.....float the empty hull and look for any leaks.......when you find some......try and hammer the rivet back to shape and add a coat of gluvit.

this product will seal the boat from leaks.

then....you can foam the boat any way you like with out worry.

i wrote all this to help you make the best choice for YOU. each person is different, and some people do not want any foam in the boat at all.

hope that helps

cheers
oops

 

[Texasmark]

Re: Is foam insulation below deck of aluminum boat necessary?

I had both. A small John with nothing to call a "deck" but the bottom and some ribs. It had foam in the seats that were attached to the sides.

On a larger boat that had a floor and all that stuff, foam was below the deck. Hard to say if foam there would cause the boat to invert.....regardless, I'd take an inverted life jacket to a non inverted anchor any day.

Pointless question.

Mark