Full foam between deck and hull ?

One of my customer let us fill foam full between deck and hull, just like Boston Whaler. Is that good ?
------Some expert told me too much foam is not good, because even the foam are closed cells, they also will absorb water, after years the boat will become heavy and very hard to let the water out.

 

not good not good !!!

Not good not good at all !
The floatation in the bottom od completely the wrong place to have it .
i saw a small boston whaler fill with water in the pouring rain at Papaeete and all of a sudden it flipped completely up side down , lucky it was moored and no one close by . have to be very careful how much floatation you have in a boat and where its placed . Seach the uscg site and find there recomendations . I been down this road some time ago making automatic inflating floatation for aluminium boats . the placement is critiacal !!.

 

With the possible exception of 2C foam in sealed plastic bags (sausages) the general concensus is not to use foam in marine applications because the thin membranes deteriorate and allow water to seep in and stay there.

 

Its a terrible way to build a boat . The older Boston whaler were not good boats and the glass work on the ones i seen was really thin and its the foam held them together sort of !!,Yuk !!

 

Dont do it !!!

 

and if the hull is made of epoxy?

 

Whats that got to do with it ??

 

The idea of building in floatation is appealing on the surface, but all you have to do is look at a few old Boston Whalers to see where it can end up. A water saturated hull is one of the hardest repair jobs there is. If it were me I'd want him to sign a waiver relieving me of any responsability...now and in the future.

MM

 

Water has to first get through the laminate, deck or hull, to get to the foam?

We all know polyester is water-resistant not water-proof, that's what the gel-coat tries to remedy.

So if it is a sealed space, ie. epoxy laminate, that it will stay dry in the first place, then fill with foam!

My opinion only, not my facts!

 

From past exsperiances its also a way to have thinner laminates and almost no stringersa or stiffeners inside as well so the foam takes it all .
It wont matter what resin you use the water still get in !! theres bolt holes theres a join all way round theres drains in the motor well !!!count them all up !you will need to take your shoes off because you wont have enough fingers !! and what gets in cant never get out ! sorry not for me not never !,chop up and stand on as many bits of boat as you like time will always find a way !!

 

When I was building the mini-keels for my boat, everyone of note recommended - - "NO foam fill" ! ! ! and I now wholeheartedly concur, adding that when you sell your boat it will be extra nice to know that if inspected or, there is a need to open to effect a repair visual evidence of a dry compartment will be very reassuring. - - Build it right in the first place and do not stuff with rubbish that may deteriorate and hold water in the mix of rotting innards... A slosh sound is a warning,.. No sound with water held in suspension is a grave mistake...

 

how much foam is needed ?
Now when making boats we must use foam to get enough buoyancy.
We usually do this way : Buoyancy (foam volume) = total boat weight (boat+engine+baggage+passengers) Is that right ????

 

how much foam needed?

We usually do this way : Buoyancy (foam volume) = total boat weight (boat+engine+baggage+passengers) Is that right ????

 

That will only give you a boat that floats just on the surface. Most boats with serious safety concerns ensure flotation that provides a bit of of freeboard .

As Tunnels commented, the positioning of the flotation is very important

 

Actually to answer your question we need more info. What type of boat, I/B, O/B, I/O? How long? Monohull? A pic would be good.

Another question? What kind of foam? Polyurethane closed cell? Polyethylene? What?

Also a lot of opinions given but nothing based on ABYC or USCG requirements. Using Boston Whaler as a model is misleading because the foam in a BW is not just there to provide the flotation. It is structural foam and is part of the structure of the boat. Yes, in the mid 90's the USCG tested a BW for flotation and it failed. Not because it didn't have enough foam. It had plenty, but it was distributed wrong and the boat heeled to far over.

Flotation in boats is placed to support three things, the boat, the people and the engine. If the boat is an outboard the foam to support the engine has to be placed at the two rear quarters, and high enough to support the engine without the weight of the engine turning the boat over. The flotation to support the boat is distributed about the boat. The flotation to support the people is distributed evenly around the area where the people will be.

Placing all the flotation in the bottom of the boat will most assuredly make the boat roll over and float upside down..

Outboards are required to have level flotation, that is they float relatively upright when swamped. In this case distribution of the flotation is vital.

Inboards are required to have basic flotation. That is they float when swamped, in any attitude, as long as some part of the boat is out of the water. Usually the part out of the water is the bow. In this case where the foam is is not important unless you are trying to achieve something better than basic flotation.

Yes there are legions of stories about foam absorbing water. Closed cell foam is NOT supposed to absorb water. But in years of testing boats for flotation I have seen many that do. It's all in how the foam is installed and what kind is used. I have also participated in research to find out why some foam absorbs water. Not much was found that was conclusive.

Anyway don't do it until you know the answers to the above questions and look at the USCG and ABYC requirements. Oh and by, the way, if this boat is over 20 feet it isn't required to have foam, so you can do it any way you want.

See http://newboatbuilders.com/pages/flot.html
USCG Boatbuilders Handbook http://www.uscgboating.org/regulations/boatbuilder_s_handbook/flotation_landing.aspx
ABYC http://wwwabycinc.org