Thread: Floatation Foam

G'day Darren

Epoxy doesn't seem to react with the foams I've seen it applied over.
Unlike polyester resins.... !!!

Do the class rules specify any particular grade of foam?
If not, polystyrene works fine but needs to be able to dry out between wettings. ie- either perfectly sealed or well ventillated.

Pour-in foam should be avoided as it absorbs water & doesn't release it readily. Also it is too heavy for its volume.

Best of the bunch perhaps, in the last Australian Amatuer Boat Builder magazine, Terry Buddell wrote about a new foam which meets Qld DoT standards for a sea-going flotation foam. Similar to closed-cell pool noodle material (which would also work well but costs an arm, a leg & half your first-born at Clark Rubber.)

HTH
AJ

You want to use a closed cell polyurethane foam, which is typically a two part mixture (yep, pour in). It comes in a number of densities, which commonly are 2, 4 and 8 pounds per two gallon batch (there are other densities). The lower density stuff is the most buoyant of course. A two gallon mix will yield about 8 cubic feet of foam, which produces about 480 pounds of buoyancy. 8 pound foam is for structural applications, maybe a core. A 2 gallon mix will get you about 2 cubic feet of foam and provide about 110 pounds of floatation.

Just pour the two parts together and mix. Mix quickly, because it starts to react pretty much right away and expand. Pour the goo into the cavity with an eye toward the amount of expected expansion you'll get from this particular density. When cured it's easily cut with a hot knife or hand saw.

I don't like pour-in foam for flotation, it can trap water and it adds weight unnecessarily. Just pump all of the cavities full of old 2 litre plastic milk bottles with their lids on. Cheap, light and nasty! You can squeeze them into amazingly small areas too, let them expand, and put the lids on afterwards.

Mind you, I like flotation compartments that serve one purpose too!

Cheers,
P

FGI sell a polyethalene foam cant remeber the name of it comes in various
thickness up to about 100mm in a 2400 x 1200 sheet. Same stuff as used in modern day life jackets. Meets all sorts of standards.
I paid around $100 for a 50mm thick sheet

Hi,

Thanks for the replies.

I'm not keen on expanding/pour-in foam for the reasons stated - I've heard negative things about it from others too.

I'll check out standard plyeurathene, and thanks Lewy for the suggestion of FGI - that's where I get my fiberglass, so I'll ask about it.

Regards,
Darren

Howdy - Pour in Foam is the instrument of the devil.

Generally If foam is really required I try to glue it in virtually as part of the structure and keep it clear of the floor area - glued up under the deck or high up on a bulkhead is a good idea. To minimise performance effects keep it as close to the cockpit as you can under the rules.

With more friable (easy to break foams) you can always put a couple of coats of pox on them to stiffen up the surface. Works wonders with el cheapo eskys too!!!!

MIK

I completely understand your distain for pour in foams, Michael, but I've had to yank out enough water and oil saturated polystyrene over the years that I don't mind. I wouldn't want to be the person that has to do repairs under the poured in foam, but happily will fill around ice boxes, fish wells, etc as well as form fitted under side deck floatation.

I have used a few interesting techniques to insure easy removal, most all involving a release agent (automotive paste wax usually), so it can pop out of it's void, reasonably intact, repairs preformed and re-inserted.

I did watch a grown man cry (very loudly too) when he poured a 2 pound foam into the fore peak area of a small canoe yawl. His bellowing began when the whole of the fore deck, first buckled then cracked and finial ripped loose from the beams and clamps. Though there was an access hole, the foam over flowed it, eventually sealing it against the hull sides, continuing to expand inside the chain locker area, which really made a mess of his dainty little yawl.

The foam most commonly used for whitewater kayaks is minicell, I don't know a supplier but if you ask on a paddling forum you may get an answer. Try here http://www.adventurepro.com.au/forum...?board=paddlea

The foam I used is Microlen found this about it.
http://www.sealifedesigns.com/seasho...en%20Flyer.pdf

Plastics boats are shipped with a foam block under the deck to avoid sagging in transit. I have used this (closed cell) foam in the past with good success. I was able to get some for free from a large kayak shop. It may be worth ringing a few stores if you are looking for a cheap option. I used contact cement to secure the foam.

I would avoid poured in foams for all of the reasons outlined above. If they still turn out to be your best option, perhaps you could foam fill some containers or bags and then place them the boat.

I am not familiar with the rules for racing, being more interested in seakayaking, but could you get away with float bags or dry bags? Chris Cunningham from seakayaker magazine did an article on making your own custom bags. As you are installing hatches I assume you would like to be able to remove the flotation foam and put gear in the boat.

On a bit of a tangent, I had another quick look at your building post, I would be interested in knowing what style of hatches you are going to use. I used the old style CLC hatches and they leak quite a bit (CLC Chesapeake 16 built from the new kayak book).

regards,

James

Originally Posted by PAR

I completely understand your distain for pour in foams,

G'day PAR
Possibly what is readily available in the US of A (eg. closed cell polyurethane in a bottle) is not available here in Oz. Except possibly in 44gal drums or 1000Litre pallet tanks.... not exactly 1-off canoe quantities...

The only readily available small-quantity 2 part pour-in stuff I've seen here is the one that produces very small bubbles & is almost grainy in texture. Most commonly used for packaging heavy or brittle items such as tiles or jet turbine components into cardboard boxes. Heavy & expensive for its volume compared with polystyrene blocks or bean-bag beads. It absorbs water & etc relatively quickly & is the devil's own job to dry out when it does.

cheers
AJ

Originally Posted by yjnb

On a bit of a tangent, I had another quick look at your building post, I would be interested in knowing what style of hatches you are going to use. I used the old style CLC hatches and they leak quite a bit (CLC Chesapeake 16 built from the new kayak book).

regards,

James

Hi,

Thanks for the additonal links, I'll ask around and see what i can get, and where. Will let people know the outcome.

James, I'm not sure on hatch design yet. I'd like them to sit flush with the deck, so will go with curring them from the deck panel and epoxying in supports underneath. I was going to use rubber strips to seal, but aren't sure on how to best lock them down yet to prevent leaking.

I have to update my build post so will put more pics on this week - should have the deck on this weekend so I need to decide on hatches soon!

Regards,
Darren

One Ocean http://www.oneoceankayaks.com/ has some ideas on hatch design that look promising.

cheers
AJ

I was watching a friend yesterday laying up some surfboards at his factory. He has switched to using polystyrene foam. It is much lighter than conventional foam but requires a different resin coating. The resin used in board manufacturing will "melt" polystyrene. I think that the compatible resin is something like a West Sytem 2 part mix. If you are interested I can find out what resin should be used.

prozac