Drying Experts Answer This

[Goldenboy]

On the older Ski Nautiques/Correct Crafts which are competition ski boats. On the bottom of the boats under the floor they have wooden beams called stringers. The wood has foam packed around the wood. The foam is for floatation and noise reduction. Once the foam gets wet it NEVER dries out even if stored inside. Wet foam then rots out the wood. When this foam gets wet I have read cases that it adds over 300 pounds of weight putting pressure on the hull then they start to crack. I know you can not stop the rotting wood. But do you think you could put a dehu inside a boat on top of the floor with plastic over the boat making a tent and pull that moisture out of the foam?

Golden Boy

 

[dgardner]

I'm not a WDR guy, but I am a boat guy. Here's my 2 pennies worth. The foam doesn't soak up water per se, flotation foam is always closed-cell, to trap air. That's what gives it buoyancy. The problem is the space between the hull, floor, and adjacent stringers (filled with foam) is fairly well sealed from the atmosphere. There's obviously enough of an opening for water to seep in, but nothing for air circulation. The water is trapped between the foam and adjacent surfaces, including stringers. Capillary action causes the water to wick into all the areas around the foam.

Since there is no opening between the wet area and above deck, dehus would draw out very little moisture, I think. Now if you knew where the stringers were, you could drill a small hole into each pocket (in an unobtrusive location, obviously), and use an something like an octi-dry to force air into the spaces between pairs of stringers, driving the moisture into the bilge area, where it could evaporate.

Some higher-end boats have a double layer hull, with blocks of balsa wood glassed-in between to create a very strong ply sandwich. Once water gets to these through tiny stress cracks in the glass, it's near impossible to dry them out. Hull strength is compromised, and the boat can gain weight this way as well.

Maybe a real expert will happen by and set us both straight...

 

[Bob Foster]

Rotten stringers. Plain and simple. It is common on boats like that.

Here's the cure, no two ways about it.

First go down below and drill out a stringer with a 1/2 drill bit you will come up with what looks like soggy cornflakes , that is, what used to be a ply stringer. I am certain you will find rotten stringers. Drill near the bottom of the stringer near the hull particularly where when the boat water levels might be when it was stored on its trailer.

The cure:
A sazall, grinder with 25 grit sanding disks lots of fiberglass, resin, roving etc because you are about to canoe the inside of that puppy by ripping out the floor and tearing everyone of those rotten stingers out and replacing them. Also you might end up replacing the blocks the motor mounts are on too.

There are holes in between the stringers to allow the water to drain between each stringer section. These holes are called limber holes and often when they are put in they are not properly sealed and resined up and that is where the rot started. That and the boat accumulated standing water or rain water in its bilge.

Anything else is cosmetic. If you do dry out the exterior of the stringers you still will have wet cornflakes (that used to be ply stringers) in cased in innocent supposedly solid looking stringers. The drill will tell all.

I've done this job before and it ain't pretty. Don't use pressure treated wood as it doesn't work well with resin.

Here is an example I found of a larger boat
http://images.google.ca/imgres?imgurl=h ... N%26um%3D1

 

[Goldenboy]

Dan in these particular boats when they pull the foam out it is wet. In some cases they have pulled 400 to 800 pounds of wet foam out.

Golden Boy

 

[Bob Foster]

 

[Bob Foster]

These boats are chop gun single hull and its the flotation material under the floor that has picked up the water. The compartments might be even glassed to the stringers. If this boat is over 10 years old look real close.

 

[Goldenboy]

Bob I know there are 100,000 cases of bad stringers. So there are 100,000 owners out there with wet foam. Can the foam be dried out? That is all I am trying to get answered. No the problem wont be fixed but if a guy could dry these boats out it would help them out getting rid of all the extra weight.


Golden Boy

 

[dgardner]

Dan in these particular boats when they pull the foam out it is wet. In some cases they have pulled 400 to 800 pounds of wet foam out.

Golden Boy

Interesting. I have pulled twenty year-old foam out of boats that was still, well, 'floaty'. Is fuel or something else breaking down the foam so it will absorb water or something? Your standard 2-part urea foam is pretty much impervious to water.

I have done a couple of floor/stringer replacements and I concur, it is not fun. I would still be interested to see if a dry-guy thinks my octi-dry idea would work.

I learn something new every day.

 

[Guest]

As for drying the foam I don't know, but I can add this:

In 1984 MasterCraft went to an all glass construction. The first couple years aren't considered great boats as they had a learning curve in the new construction methods. After that the boats are rock solid.

Even the hull will gain weight in water. With a dry bilge, the exterior of a glass boat stored in the water will absorb water. That is the main reason of many why we keep our racing sailboats on the hard. To dry them out we take them to a hot place and let the water bake out. I'd think you could remove the foam and put the boat in a hot and dry environment and the water would come out, but it takes a LONG time (months) and Iowa really isn't dry when hot.

 

[Al]

Yes the foam can get wet! I did one a few years ago and the foam was waterlogged, the stringers rotted and so on.
I tried drying it at first untill I discovered how wet it really was but if someone had taken the time to dry it out before the major damage set in like (preventitive drying) maybe it can be avoided.

I think thats what Waldo is getting at and it may be a good idea.

 

[Ed]

Waldo,
We just had a Rinker in our shop this summer that was pulled from the bottom of the lake here. Ins. co. asked us to dry it. We tried everything possible from tenting the entire boat with 6 mil poly, ducting in heat, had an evolution siting on deck, airmovement, everything we had on hand. While it did dry some, after all that time, some of the foam was still wet. We tried to tell the ins. co. to cash this guy out from the begining, but they insisted we try to dry it out. Worst thing was the fuel smell that had permiated all the foam. You can't get that out.

 

[Desk Jockey]

No expert, especially about boats but if you can't get air to pass over it, it will not dry.

It would be interesting to play with using desiccants and the TES, if you can't get air to the moisture I think you'd have limited success.

 

[LeeCory]

You know what the saying is about boats don't you?

"Bust out another thousand"

 

[Guest]

My question is; How in the world do you guys have that much spare time to play with boats when you have a business to worry about???

 

[The Great Oz]

I'd guess a good guy to ask about a drying in place plan would be Ernie Storrer of Injectidry. Without being able to compress foam we've never been successful drying it completely, and even then you could debate whether the time and cost was less than replacement.

I don't know if the foam breaks down in time or with exposure, but it starts out as closed cell, just like the styrene foam that will hold up a dock for fifty years. I've seen household spray-in insulation degrade to a stringy mess, so maybe some types of foam used in boats doesn't last either. Wet foam problems occur even in the supposedly unsinkable Boston Whaler, so if you search boat forums you'll probably find a ton of information.

 

[Ron K]

My question is; How in the world do you guys have that much spare time to play with boats when you have a business to worry about???

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