Filling a rubber dinghy with foam?

[gag]

I think everyone should chip in a quid as suggested. After all , how often do you get to see an expanding inflatable burst its foamy guts out on vid eo for £1.
Or post him all your old builders foam.
Hmmm ....the more £s the more foam....and does the reactive part make it happen faster if overdosed ??

 

[William_H]

Yeah the whole idea seems like it will be good for a laugh. You may recoup the costs in prizes from "Funniest Home Videos" TV show. I presume you have that show or equivalent in UK.
The foam will not spread itself out evenly but will bulge and burst.

Another thought is if you can get plastic storm water pipes and fittings that could be inserted into the rubber tubes to provide permanent air tanks. But don't let me spoil; the fun.....
Go for an old F/G dinghy and put a cover over it to avert filling with rain water. good luck..... olewilll

 

[cliffordpope]

You could use the dinghy as a temporary mould. Cover with a few coats of resin and matting, then cut out all the rubber. Then fibre-glass in thwarts, strenghthening ribs, boyancy tanks, etc.
But it all sounds a lot of trouble and expense compared with just patching up an old GRP dinghy in the first place.

 

[apollo]

A mate of mine tried just that, Polyurethane Foam in an old infalatable.

It sank like a stone!!

 

[polwart]

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don't do it - it will be a disaster. as already stated expanding foam is not closed cell -so any water that gets in will stay in and eventually it will sink.

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Was that an order!

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<span style="color:red"> No - if he wants to waste his money and still have no useable dinghy then that is his perogative. The fact that I stated it with some degree of assertiveness is because it may it first appear to have worked but will gradually soak up water - and could potentially become quite dangerous (i.e. sink, or become unstable, or just be too heavy to push with a wee outboard) </span>

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I doubt epoxy will stick particularly well to hypalon/pvc - never minding the issues of flexibility.

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Ever heard of finding out? It doesn't actually need to adhere, in the same way the gel coat does not adhere to the mold, do you see?

[/ QUOTE ] <span style="color:red"> This was based on educated, reasoned judgement, even hypalon glue doesn't stick particularly well to hypalon without a lot of intensive prep and care. Gelcoat doesn't stick to the mould but the mould is not part of the boat? I assume that we are talking about applying a relatively thin layer of epoxy over a boat (as you might do as an exterior coating to reduce osmosis, or as a "tough" paint on wood etc. Epoxy is not that strong (probably the wrong engineering term) unless reinforced with e.g. fibreglass. I am absolutlely certain that an epoxy painted hypalon dinghy will not in the long term (days rather than weeks) be any more water or air tight than before it was painted. </span>

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expanding foam is expensive (as is epoxy) - for the cost you could easily buy a cheap fibreglass or moulded plastic boat. There are some rotomoulded plastic dingies with hull shapes similar to an inflatable that will have all the stability etc. you want.

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Have you never tried something just to see, I bet you had daddy buy you a go cart rather than scouring the local tip with your mates for pram wheels for your own design MkIII as the last two snapped. It's how you learn to do stuff.

[/ QUOTE ] <span style="color:red"> don't be such an onoxious twat. "daddy" would have told me to give up if the wheels fell off the second time and there was no way he would have spend money for me to see if I could trash a commercial design. I am just as open to experimental development as anyone. I thought the questioner had come here to ask advice. I gave him my advice. If he follows that advice he will save money. If he doesn't then thats his choice. </span>

 

[snowleopard]

There are two types of 'foam in place' foams generally available.

1. Two-part REP (Rigid Expanded Polyurethane) that you buy as two liquids which expand once mixed. The resulting foam is not closed cell but more importantly it is very low strength, to the extent that it can be crushed by as little a 2ft of water pressure, let alone you standing on it in your size 9s.

2. Builder's 'expanding foam' from e.g. Polycell. This comes as one can and sets with exposure to air. It continues to expand for some time after spraying and generates large pressures. If you get it wrong it will split the dinghy. As to whether it absorbs moisture, that is a moot point. It is used to form a moisture barrier in building though the manufacturers say it will absorb a percentage of its weight in water over time. At present I have a sample immersed in water as a test and it has not absorbed a significant amount after a month or so. I'll report on that after a while longer. It has some flexibility when set so won't crush like REP.

All the stories you hear of people having to hack out tons of waterlogged foam from 'sealed' compartments on old boats are REP.

 

[Gunfleet]

I don't believe any of you are thinking laterally enough here. You need a pram dinghy AND an inflatable tube lashed around it. End of prob!

 

[26ft_bathtub]

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I don't believe any of you are thinking laterally enough here. You need a pram dinghy AND an inflatable tube lashed around it. End of prob!

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Don't Walker Bay make one of those?

 

[David_Jersey]

Christ!............I was aiming to make a cheap dinghy that also suited my needs, not starts WWIII /forums/images/graemlins/frown.gif

FWIW:-

The heavy cautions about over expanding foam are noted, but I am truly not bothered if I get this part of the experiment wrong - and I will set up an exclusion zone /forums/images/graemlins/smirk.gif

However what is giving me pause for thought is that my idea about just coating the Dinghy in Epoxy does not seem to be the way forward due to "Non stickiness" to Hypalon and a lack of strength without laminate. These concepts I can understand.

In the (apparently!) unlikely event that I did get a dinghy shaped dinghy after the foam part of the operation, I wouldn't want the dinghy to then slowly get waterlogged. To be honest I really do not want to go down the route of laminating her in GRP all over (note it's now a "her", I am getting attached!)........mainly from complete laziness, but also the cost - as pointed out be cheaper to buy a plastic dinghy (and learn how to swim properly!).

Still, I haven't completely given up on the idea.........will put my thinking hat back on. But in the meantime will have a trawl through the old PBO's for the article on refurbishing a rubber Dinghy.

 

[rich]

what about this then.

 

[David_Jersey]

If I had the skills to manage anything remotely similar.......... I would have built my own yacht /forums/images/graemlins/laugh.gif

I am currently thinking of filling it with helium /forums/images/graemlins/grin.gif


(Actually, I guess I should make clear that this last comment is a joke, wouldn't want the "thread" to get overexcited again /forums/images/graemlins/confused.gif)

PS the Seat deflated in 5 minutes, the rear tubes are slowly following........and of course the bow tubes do not exactly hold any pressure /forums/images/graemlins/laugh.gif

 

[BrendanS]

You're better off with hydrogen. It has more lifting capacity than helium, and is cheaper.

It does have a bit of a reputation for being a little inflammable however.

 

[bendyone]

Ha
the danger of using Helium is that .......................

 

[velo]

get cheap bean bag then pour beads into valve opening cover with rubber paint exarmy vcheap on ebay

 

[hlb]

I'm a big believer in builders foam and think every boat should carry a tin. ( remind me) /forums/images/graemlins/laugh.gif

I can see the problem of it not filling every where. But then, if you just make a hole where its not filled and start again?? Most of the spare foam should just come back out of the hole.

Dont go along with this closed cell arguement, though on second thoughts, my cushions are wet through!! /forums/images/graemlins/crazy.gif

Anyway, a can of foam is only a few quid and well worth seeing the results.

 

[RutlandMike]

Cracking idea. Having used gallons of the expanding builders foam, I can confirm that it really is closed cell and will not absorb water - but how about this:
Builders foam expands a lot and exerts a lot of pressure while doing so - I've blown apart a couple of old hollow doors I was filling with foam to increase their sound reduction qualities! Got it right third time, worked a treat. What I did was spray a fine mist of water into holes I had drilled (this foam needs H20 to cure) and then put in the foam a bit at a time, leaving it to expand between doses. The same could be done with the dingy. Maky a series of holes, squirt in a bit of water, swill about, squirt in foam, massage into corners. The holes could be about 3 inches in diameter allowing any overexpansion to escape without splitting any seams. Once cured - leave for several days, it cures from the outside in- just carve off the overspill and patch filling/expansion holes with rubber (bike repair kit or similar). Job done! I'm pretty sure this is the same kind of foam they use in Bic plastic dinghies. Now I want to find an old inflatable to give it a go! /forums/images/graemlins/laugh.gif

 

[David_Jersey]

Cheers for the tips!

Week 3:

David is still looking out of the window at semi inflatable in his front garden. /forums/images/graemlins/grin.gif

(note to myself, must look at one of the 1 million threads on how to post pictures on YBW!)