Buoyancy Foam?

[rbcoomer]

As those of you who have seen my Arrowbolt thread will know, I'm currently removing the floor (compost), stringers, waterlogged foam etc.

When I refit with new in the coming weeks, I want to replace the buoyancy foam that is in pockets in the bow, under the floor and in stern side pockets etc. However, I'd like to think these foam materials have progressed a bit since the boat was built (70's/80's). Are there any water resistant equivalents that don't act like a giant sponge? Perhaps I could fill with ping-pong balls or similar - or would they rot?

Is there any reason I shouldn't use the aerosol expanding foam as found in builders merchants? Is there anything else anyone can recommend?

I know I could leave the voids empty, but kinda like the idea that where there's foam or something else, the water wouldn't be able to swamp quite so quickly in the event of a hull breach etc. (Ok, ok, so I'm paranoid... )

Thanks as always.

 

[gordmac]

This may be of interest:
http://www.worldseafishing.com/forums/showthread.php?t=171738&highlight=playpit+balls
Worth searching through the forum.
This was recommended there, I don't know about it though:
http://www.cfsnet.co.uk/acatalog/CFS_Catalogue__2_Part_Polyurethane_Foam_Liquid_415.html
If you do use balls or bottles put them in bags of some sort, it doesn't take that big a hole for them to escape.

 

[Tranona]

If it is in apermanent sealed compartment then use closed cll foam. You can buy it in two part form from GRP and epoxy suppliers. I have just used some from Blue Gee in Poole. Do not use builders foam as this is not closed cell.

 

[rbcoomer]

Thanks guys - I'm working tonight but will look those up tomorrow.

The sections will be closed off by the floor, but rather than leave holes to pour in and risk expansion damage (and entry point for water), I was going to build up the foam before fitting the floor. Unlike the original, I'll also glass the underside of floor and edges before fitting!

 

[AndieMac]

Have a read of this, particuarly page 3 of the pdf file at the bottom of the page.

http://www.mast.tas.gov.au/domino\m...ide+to+Buoyancy+in+Trailer+Boats?OpenDocument

 

[Assassin]

There are many new types of foams but you need a "closed cell" type as this does not absorb water, never use the open cell types as they do act like a sponge.

These come in two main types, spray on types which can be sprayed with the right spraying equipment, or in spray cans; and the two part mixes. Spray on types are fine for open areas as they expand once sprayed on, and they do require a lot of trimming if they are heavily applied which can be a waste.

Two part types are literally two parts which are liquids and they are mixed together and poured through any void, they expand at anything from 7-20 times their original volume when liquid. These are best used when the floor/fittings are in place as they simply run in as a liquid and expand, and as long as you know their expansion rate you can calculate how much to put in. If you put too little in you simply add a little more until a void is filled. Their downside is as they expand the pressure can force thin panels out to a bulge if they do not have a vent, or too much is put in.

 

[Assassin]

I would not advocate using playpit balls or similar as they have small holes in them to let air out as they are crushed, holes to let water out also let water in.

Plastic bottles are nearly all bio-degradeable plastic so they will degrade over time so you will be left with a mass of decomposing plastic with no floatation value after a period of time.

Both these systems will rattle around under the floor and can create other problems.

 

[rbcoomer]

Thanks once again - great feedback as always!

Assassin - yes agree on the foam. If it's waterproof - and it seems technology has indeed progressed on this front from the info above - then that has to bean better option than the balls/bottles IMHO. My concern about ping pong balls or even the bigger plastic 'ball pool' variants, was that like your comments on the bottles, they'd probably decompose and once boxed in, you'd never know!

Andiemac - I've seen a few threads on rebuilds where they have deliberately left out the foam as 'unnecessary' and a long-term liability. These were mostly in the US, and presumably lake boats, but I can't help but disagree on this and side with the MAST standpoint in the doc you kindly linked to. I would certainly not feel happy with no buoyancy at all, it was just a case of what's the best choice? I did wonder that if I could tab in the floor from within the voids, I'd be more happy that they were airtight, but as that's not possible I fear water would find a way in and there it would stay.

I'm leaning more towards the pre-formed foam blocks cut to fit - more work, but the link earlier that show's the water resistance advantage was astonishing! I can also integrate them into other voids above the waterline.

Fletcher's have always had the buoyancy foam and I've seem a couple swamped in the last two years around local waters - neither sank. In the event that the worst did happen then I'd rather stay with a swamped boat - it makes a much bigger target for a helicopter/RNLI etc to spot than a number of lifejacket tops bobbing about. Even on a good day!

 

[Assassin]

I would tend to stay away from the insulation blocks as many are not the closed cell type, and those that are are normally only closed cell if they are used whole, if they are cut to fit they become absorbant. Many i know have fallen foul of this, they are designed to keep a boat afloat for a pre-determ ined time ranging from 10 minutes upwards. Their ethos is simply to keep a boat afloat long enough to get back to shore and it assumes the hull is punctured and the engine/s are working, and its predominantly for use on boats for lakes and rivers.

 

[rbcoomer]

I would tend to stay away from the insulation blocks as many are not the closed cell type, and those that are are normally only closed cell if they are used whole, if they are cut to fit they become absorbant. Many i know have fallen foul of this, they are designed to keep a boat afloat for a pre-determ ined time ranging from 10 minutes upwards. Their ethos is simply to keep a boat afloat long enough to get back to shore and it assumes the hull is punctured and the engine/s are working, and its predominantly for use on boats for lakes and rivers.

Thanks again - that's really useful info and goes to illustrate again the wealth of knowledge on these forums!

I'm thinking that using the mixed solutions in the floor voids and rear quarters plus the preformed sheets to line the insides of the gunwale-to-floor section of the hull is perhaps the best compromise. I was planning on building in storage lockers here and just leaving a channel each side for cables etc and a recessed ledge for small stuff. Storage is always an issue in the 14' and everything tends to get thrown into these open 'pockets'. A more structured approach with accessible sections for things like lifeline, flares, extinguishers, first aid, mooring ropes etc would save space and make checking easy. If compartments were encased in buoyancy this high, a capsize would also be much less likely. (You see AndieMac - I did read the doc - and very informative it was too. )

 

[AndieMac]

Keeping the boat afloat as long as possible after sinking is a big priority in our remote waters RBC, we haven't got the support of the quick response RNLI units as you have in the UK, unfortunately.

Good luck with your project mate