drying wet foam in keel

grafozz

grafozz

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Trying to do a small keel repair, the crack has been ground out to a hole and the boat has been standing , dripping water from the foam within the keel , but after more than a month it is still dripping ?
I have tried towels , a vacumn cleaner and a small heater , but it still persists .
How can I dry this out so the reapairs can be started ?
the keel is completly filled with foam and needs to be dry , any ideas please ?
 
Depends on how much foam and water is inside. You may well find it better to remove all the foam, do the repair and refoam with closed cell foam.
 
Only way to dry it out is to hack it out one way or another. Personally i wouldnt bother refoaming it. Regardless of if its closed cell or not any of the single or mixable two pack foams will absord water sooner or later whether you like it or not.
 
Polystyrene foam dissolves in petrol. Pour some in and make a hole right at the bottom of the keel to let it out. Sonds dangerous? No different from a large petrol tank.
Check first that it does dissolve it.
Normal precautions regarding interior ventilation (lots), sparks etc.

As earlier, what is the foam doing? Do you need to replace it?
 
Keith 66 said:
Only way to dry it out is to hack it out one way or another. Personally i wouldnt bother refoaming it. Regardless of if its closed cell or not any of the single or mixable two pack foams will absord water sooner or later whether you like it or not.
Click to expand...

Closed cell won't.
 
I assume polyurethane foam, mixed and poured? Closed cell content is only about 70% with this method, which means that the remaining 30% absorbs water over a long period. It will almost never dry if left to its own devices. The only way is to dig it out.

I speak as someone who made lots of canoes in the past, buoyancy provided by mix and pour PU foam ex Glasplies or Strand Glass. After a year of capsizes I had to dig all of it out again.
 
The Vacuum Cleaner will do very little as pressure it can achive is not low enough to evaporate water, however If you can beg/ borrow / steal a vacuum pump, you could connect the inlet to the foam filled void. Assuming you can get the entire area leaktight, the pump will reduce the pressure to below the point where water will start to boil at normal outside temperature ( about 15 mbar) However at 15 mbar the atmospheric load on the exterior of the keel will be 1 Ton per square foot so keel could collapse. Other slight problem is the water could freeze if there is no thermal mass to keep it liquid. So not really practical however it leads onto another possibilty and that is to get set up some form of air heater such as a length of copper pipe formed into a coil such so that it can be heated to about 100 C by whatever means and air blown through it at relatively slow velocity into the void. Will take days and days rather than hours but may help. You need, heat, air flow and even distribution.
 
Besides the interminable wait for the foam to dry you might be able to increase the flow by drilling a hole at a higher location than that from which the water is dripping so that air can come into the enclosed space and replace the water. This will only work if the foam-filled space is not already exposed to the air at some point within the boat. With wet rudders this second hole helps.
However, as has already been said, the only real solution is to remove the foam.
 
chrishelen said:
Closed cell won't.
Click to expand...

Maybe the cells themselves won't but the space between them will.
Think of a jar filled with marbles. If water is added to the jar none of it will be absorbed by the marbles but there is still a good percentage of space between them where water can fit.
 
Thanks , all , really interesting , the conclusion I have arrived at is to remove the foam entirely , BUT
I have a slot/ gap of about 90mm x 60mm x 300mm , this will make it very difficult to actually claw it all out , in addition , there are 3 x chambers with vertical stringers which means the foam could only be extracted from 1 x chamber .
The rear chamber is possibly still watertight , cannot be certain though .
the existing foam is suspended at about 70mm from the inner floor , not sure why or even how that was achieved at build ?
Today , there was no water under the gap so this may mean it is coming near to drying ? I pushed a towel into the gap and it came out after 2 hours ,perhaps 30 % wet , so this could show that it may be drying .
In Greece so lucky with hot sun directly on the errant keel post 1200 , and the pm breeze is blowing straight at the gap !
The removal of all foam is therefore too difficult so unlikely although it is plainly the best thing to do .
What will foam do anyway if it absorbs water , quelle pont ?
Now I need to know which is the best foam to refill with ?
Soudal foam/ adhesive is in the local hardware shop so may go with that the expansion rate ( unrestricted) is 40 litres per litre would this be dense enough ?
I doubt it would take a 1 litre can but will use tubes to reach the extremities .
I plan to use Epoxy resin for at least the first few layers of CSM and mat to give better key to the grp .
. Sorry Boatmike , yes a catamaran . Solaris Sunstar
 
Keith 66 said:
Having split more rudders & chopped more foam out of the bilges of fibreglass boats than i care to count i have yet to find a foam that has not soaked up water. The two pack polyurethanes are little better than the builders foam in cans.
Click to expand...

I remember lots of boat builders in the 70s used open cell expanding foam which was fine as long as the integrity of the decks and hull was maintained, but as soon as a hole was drilled and not sealed properly water got in, which over time saturated the foam, closed cell foam although more expensive cured that. It took many years, perhaps the lifetime of the boat to rot this stuff. I have just filled a hull with the stuff, messy job.
 
PuffTheMagicDragon said:
Maybe the cells themselves won't but the space between them will.
Think of a jar filled with marbles. If water is added to the jar none of it will be absorbed by the marbles but there is still a good percentage of space between them where water can fit.
Click to expand...

No it doesn't. A fully formed closed cell will be impermeable to water. The broken cells on the skin layer, of which, there is generally in the region of 3% to 5%, will of course take on water but the rest will remain perfectly dry, assuming the foam has been used according to the instructions.
 
shan said:
No it doesn't. A fully formed closed cell will be impermeable to water. The broken cells on the skin layer, of which, there is generally in the region of 3% to 5%, will of course take on water but the rest will remain perfectly dry, assuming the foam has been used according to the instructions.
Click to expand...

If that's what you believe you're welcome to use it as much as you want on your boat.
Personally I wouldn't have it on any of mine. ;)
 
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