how much water in foam core is too much?

[john8lyons]

Hi All,

We've had a very wet July in Alaska and some of the deck penetrations for the bow rail hardware of the new-to-us 2008 TomCat started dripping inside. A few of these had some rust staining on the inside, which I now know is a bit of a red flag, but were not mentioned during the pre-purchase survey. I started to pull hardware to over-drill and fill with epoxy, and found 1) that the core seems to be foam, and 2) that in some of the holes the foam was variably wet. Not so wet that they were dripping inside but enough so that they would wet the end of a Q-tip pressed into the foam. I don't have a moisture meter (yet) and don't know a better way to assess how far the moisture has spread.

Instead, I taped the inside of the holes and then held the shop-vac over the outside of the holes to see whether water would be pulled out. In the wettest holes, after a minute or so, there was some water inside the plastic shroud of the vacuum hose tip. It wasn't a lot, but enough to see some drops and wet up and inch or two into the vacuum hose. I went hole to hole putting vacuum to the holes and after a few rounds no more water was being pulled out. I left the cabin fan on exhaust overnight, which was pulling ambient air in through the deck holes and hopefully provided some additional drying.

I know that the best thing to do would be to cut away the fiberglass inside and expose the core to assess, likely remove and replace some core, and then reseal the inside structure. However, weekends are short and summer is shorter in Alaska so what I'd really like to do is fill all the 'dry' holes with epoxy, butyl tape the bolts, and get back on the water. So, how much water in foam core is too much? What's the risk to sealing some wet / damp foam in with epoxy (freeze-thaw a definite issue)? Any issue with sealing it up now and adding it to the list of things to take care of in the future?

John

 

[stevedudek]

Hi John

I just went through this with my 22. My balsa core was wet after years of not being covered during the rainy season. my area was the stern area at the fuel tank cleats the factory just used wood screws into the deck with a bit of sealer it didn't work very well. I did open the deck area and removed all the rotten material and replaced with end grain redwood blocks. it's a bit of work but i think worth it at least i now have a better idea of how this boat was built 1.5 thick floor is all it is.

Anyway i have more info how i installed a threaded insert into the decking to resecure the cleats. Let me know if you want to see some of the pictures hope yours is not as wet as mine good luck

Steve D

 

[thataway]

The balsa will speed moisture more slowly than the foam will, because of the cell structure and the way the end grain pieces are put together.

I would certainly try and get as much moisture out as possible. How much more work is it to overdrive, use a Dremel tool with bit to chop out 3/16 to 1/4 inch of foam around each hole, than just do an epoxy swab?

I would not even consider cutting away any of the fiberglass inner part. I would try and do as above for those wet holes, and put a heat lamp, plus good ventilation pulling as much air thru these holes as possible.

I suspect that the moisture has not gone far--but no easy way of telling, without being more destructive (drilling holes).

Is the boat going to be stored inside with some effort to prevent freezing? I would strongly consider it with the cost of the C Dory Tom Cat 255. (Replacement new would be in the $200,000 region now.)

You might buy one of the Ryobi or "General' moisture meters at the local lumber co--and use that to get some idea of the ring of moisture--it is comparative which is important.