Is hull flotation foam worth the trouble?

Evening,
I have noticed that a lot of post's involving hull flotation foam are usally about the foam either being water logged or generally just turning into a big sponge and going rotten. This has got me to thinking is it really worth the trouble in the long run, or would you be better off just creating a series of airtight and water tight compartments in the hull and having a watertight inspection ports in the deck so that you can check each compartment periodicaly.
Thank's Gary

 

For very small boats it may be easier to use foam, but then it should be removable for cleaning, drying and control.
Otherwise I think water tight compartments with inspection hatches is a better solution. You can use them for storage also.

 

And about foam in airtight and water tight compartment ?

 

I don't know.
You may want it for extra safety maybe, in case of a collision.
Foam can also be useful as insulation in cold (or very hot) climates.
Maybe it's easier to keep it dry if you build with epoxy than it's with polyester? There are many old polyester boats with polyurethane foam in the bottom that are very heavy..

 

It depends. If the boat is under 20 feet and you use air chambers, and it is rated for more than 2 hp (for outboards) then It has to be able to pass the level flotation standard with the two largest air chambers punctured. This is why most manufacturers use foam. It's easy to install and doesn't have any penalty. As long as yoy have enough and the boat can meet the level flotation standard. Yes foam on SOME boats gets waterlogged. Not on all. I have seen boat 20 years old with perfectly adequate flotation foam. However I have also seen boats six months old with problems. Most of the problems are because it simply because it was not installed in accordance with the foam manufacturers specs. As you said though, sealing the chamber where the foam is would make a big difference.

Little boats, those that are manually propelled or rated for 2 hp or less have no penalty on air chambers, and often that is the method of choice for small dinghys and row boats.

Inboard boats less than 20 feet have to meet basic flotation which simply means they have to float with some part of the boat out of the water. They usually use foam in the bow or under the floor because floating all that engine weight is difficult.

All that said, the Coast Guard tested an Aluminum Chambered Boat (that's a copyrighted name by the way) that had so many chambers, that although we punctured 4 of them (just for demo purposes) it still floated level. We actually had to push it under water to fill the chambers. So air chambers have their place.

 

Thank's Peter, Raggi,
Peter I'm not quite sure how the regulations stand in regards to level flotation here in Australia at the moment, so I will have to look into them. I was looking into the idea of possibily lining the compartment's that were going to be foam filled with plastic sheeting. Then pouring in the foam allowing it to expaned and set, then sanding it where it needed it so that the deck is going to sit level on the cleats and then hopefully just being able to lift out the plastic sheeting and the foam out in one piece. Peel the plastic of the foam which should have conformed to the shape of the chamber that it was poured into, then give the foam a couple of coats of epoxy to seal it and just drop the foam back into the chamber it came out of minus the plastic sheeting. Put the deck on seal up the edges properly and hopefully never have to worry about it possibly becoming water logged if I have sealed everything up properly.
With A bit of luck I should be able to find a type of plastic sheeting that the Foam wont stick to . Thank's again for the input on my query I appreciate your'e time.
Gary

 

Forgive me. I have this bad habiit of forgetting to look at profiles to find out where people are from. I looked up the standards for recreationla boats in Australia (isn't the internet wonderful!) and they are based on the ABYC standards for level, basic and modified level flotation . Here's the link to the Australian National Marine Safety Committee http://www.nmsc.gov.au/# Click on standards then on Recreational boats. THe file is a PDF and can be downloaded.

What you are proposing sounds reasonable. Frankly I'd just leave it in the plastic sheeting. Seal it so it is a bag and leave it in there. let me know how it goes. If it works I may bring it up at the next ABYC meeting.

 

CE regulations require foam or airtight compartments for boats under 6m (20 feet). Airtights compartmenst shall be tested with a small pressure for some minutes, don't remember the exact procedure.

I think it's a good idea to use plastic when you pour the foam and then seal it with epoxy. It shouldn't be neccesary if the inside of the compartment is epoxy sheated, though.

 

Stuff a big plastic bag in the space, fill it with foam and close the bag. Conversly stuff a bag full of chunks of foam sheeting (both of these methods keep atmospheric moisture from condensing in the foam). You can also fill a sealed space with plastic pop bottles ( chill them in the freezer then cap them for maximum air density) then should the chamber get holed, you have individual air cells to provide the bouyancy and you are recycling too.

 

Sound Barrier

I thought the foam also served as a sound barrier between the water and your loud footsteps..say for a fishing vessel...isn't this true?

 

Floam

I am repairing a boat currently, and will be getting to the foam soon. I also considered the idea of plastic under the foam, but came to the conclusion that if I did this, then the foam would lose some structural properties by not being bonded to the hull, stringers, underside of deck. I guess it depends on what type of hull you are dealing with, and what was there beforehand.

Im dealing with a Ranger Bassboat that used plywood stringers that were heavily glassed in, with a very dense foam between all but the center section of the boat, the bilge. (Im not well versed in marine lingo yet)
Anyway, there were multiple places that water was allowed to enter below the "sole"? and no provisions for drainage back to the bilge. (Limber holes?). The foam I ripped out would be dry at the top and wet at the bottom, but it seems that the wet areas had "morphed" into something almost like peanut-brittle, and the water seemed to be trapped within the cells of this foam. It was very strange is why I mention it.

My plan is to improve drainage using limber holes, and have purchased 4lb pourable foam to replace the foam that I removed, so as not to alter the original design, as I believe that the foam does provide a good bit of structural reinforcement. In this boat.