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Author Topic:   Drying Wet Foam with a Shop Vacuum
n1ywb posted 06-17-2015 03:15 PM ET (US)   Profile for n1ywb   Send Email to n1ywb  
Howdy, folks. I recently acquired a 1975 Montauk 17. The drain tubes were badly corroded. Today I pulled them out and the foam inside is soaked.

I took my shop vac tool adapter and stuck it in the bare drain hole. I took the shop vac and put it on the deck near the stern bilge opening and threw a bunch of blankets over it. This created a tent encapsulating the vacuum and the opening.

My thinking is that the hot exhaust air from the shop vac motor will circulate through the drain hole passage and accelerate drying of the foam. The blankets being blankets will breath out the moisture and hopefully not seal so tightly as to set the thing on fire. Also the vacuum ought to get any liquid water that accumulates down there during the process.

Has anybody tried something like this? Am I nuts? I'm going to let it run overnight and see where things are in the morning.

contender posted 06-17-2015 03:54 PM ET (US)     Profile for contender  Send Email to contender     
You have no idea just how much water is in the foam unless you weight the bare hull, or open the fiberglass to remove the wet foam. One thing about a Boston Whaler boat: if your boat has soaked up water you will not get it all out. Good luck
n1ywb posted 06-17-2015 04:19 PM ET (US)     Profile for n1ywb  Send Email to n1ywb     
I'm planning to survey it with a moisture meter and also weigh it. If the contamination is small I'll ignore it. If it's a bit bigger I might try to extract the wet foam and blow in some new foam, so long as it's not large enough to create a structural problem, since the new foam won't be as strong as the original.

If it's fully waterlogged I guess I can say fudge, run it the way it is, or scrap it. I'm probably not going to open it up and completely rebuild it. I'll sell this hull to somebody who doesn't care and save my pennies for a better one.

I'm an engineer so I like coming up with creative solutions to intractable problems. If I find a large contaminated area I'm thinking of trying to drill a grid of holes and build a manifold to pull warmed air through them, kind of like what I've got going now but with more exposed foam surface area. What have I got to lose except a waterlogged hull and the water in it?

I was reading about some of the vacuum attempts folks have done, usually without much success. I was thinking about trying freeze drying using as similar grid of holes, a vacuum pump, and the naturally cold winter weather we get here.

We only get a few months of boating weather around here anyway so if it has to sit hooked up to some contraption for the fall, winter, and spring, fine by me.

Seems to me like one of the main reasons why most drying efforts fail is the low surface area of exposed foam. How do you expose more foam surface area without compromising the integrity of the hull? Punch a bunch of small holes in it. Or maybe even dry it from the inside out by creating internal air channels in the foam from a smaller number of holes in the skin.

contender posted 06-17-2015 05:09 PM ET (US)     Profile for contender  Send Email to contender     
This is not the 1st time this subject has come up "Water in the Foam" or "Water in the Whaler" different guys on this site have tried different things, standing the whaler on end, drilling numberous holes, vacuums, and heat. I do not think any of them acheive what they were looking for. You would think the water would just drain out but it does not. I hate to say it, but the best and correct way would be to open the fiberglass and dig out the bad foam. But to give you an Idea of how much foam is bad (water in the foam) in the hull the bare hull should be weight.
n1ywb posted 06-17-2015 07:46 PM ET (US)     Profile for n1ywb  Send Email to n1ywb     
Yeah I've read all the main wet foam threads including CSW on here and every other site and their sad conclusions. I think it made me paranoid.

The shop vac seems to have dried out the drain hole pretty well, and after probing a few places with my moisture meter, I'm hopeful I won't have to try any of my crazy ideas. She seems pretty dry. I weighed it using the armstrong scale and it didn't seem unusually heavy or anything. I'll still get it weighed eventually but now that my panic has worn off I'm not going to rush it. Plenty of other things to fix on this boat.

dg22 posted 06-17-2015 09:47 PM ET (US)     Profile for dg22  Send Email to dg22     
I would not worry about a little water in the hull. Do your best to dry it out but don't worry about it. Your 1975 Whaler weighs significantly less than a new Whaler of the same size. I think the dry weight of your boat is 900 lbs and a 2015 is 1400 lbs. So even if you have 200 pounds of water in the hull which I doubt, it will still be a lot lighter than a new hull built today.
contender posted 06-17-2015 10:59 PM ET (US)     Profile for contender  Send Email to contender     
n1ywb I kinda read over your post to quick. I have the same boat and have own it since 1975. I have always had it on a trailer and just redid it two years ago. I custom my boat to my liking and wants. The boat is clean and plenty of room. Take care and good luck with the foam.
george nagy posted 06-18-2015 02:11 AM ET (US)     Profile for george nagy  Send Email to george nagy     
Here is a thought, what if you put absorbent pads in each end of the hole? Jack up the tongue as far as possible to let gravity assist moving any water in that direction.
jimh posted 06-18-2015 08:58 AM ET (US)     Profile for jimh  Send Email to jimh     
Many years ago Tom Clark had a 13-footer he dubbed Chain Saw Whaler because it was completely saturated with water in the foam and he cut it up with a chain saw. He shipped a large chunk of that boat hull to me a long time ago. Recently, while doing some clean up of the back room, I came across that section of the hull from Chain Saw Whaler. The foam was completely dry and showed no sign of retained water. Of course, it was cut up into a cube about one-foot square, and had been drying for a decade.

Read about jimp's Boston Whaler SQUALL. It has been drying in his furnace room in Alaska for about a decade, and slowly losing weight as the water evaporates from the hull.

crabby posted 06-19-2015 07:44 AM ET (US)     Profile for crabby  Send Email to crabby     
The motor in a shop vac is cooled by the air moving through the unit. If you use it as a vacuum pump you will not be moving very much air and risk cooking the motor.
n1ywb posted 06-19-2015 10:40 AM ET (US)     Profile for n1ywb  Send Email to n1ywb     
Thanks Jimh, I read your CSW threads, sad story. Thankfully after further investigation I believe my hull to be dry and seaworthy.

My idea behind the shop vac wasn't to use it as a vacuum pump per se, but rather to circulate a large volume of warm air over a large surface area of foam. Additionally the venturi effect in the passages would probably create some low level vacuum. Thankfully it doesn't look like I'll have to try this.

Thanks for your input, everybody. Since I believe my hull to be dry I am declaring this thread closed.

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