Wet balsa core in CD25 cockpit

debutler · Posted: Mon May 21, 2007 2:54 pm Post subject: Wet balsa core in CD25 cockpit

My CD25 is 4 years old. Last season my wife noticed a soft spot in the cockpit deck just forward of the port-side hatch. On removing that hatch, I found that it had not been installed properly, i.e. the hole for the hatch and screw holes not sealed properly. Consequently the balsa core was not just wet, but soaked, particularly forward of the hatch. I have read in this forum of some similar problems on other C-Dorys. I am advised that the best repair is to remove enough of the top skin to get all of the wet balsa out, replace the balsa, replace the top skin, and paint the whole cockpit to hide the patch. Does this sound like a reasonable approach?

David Butler

thataway · Posted: Mon May 21, 2007 7:58 pm Post subject:

Read very carefully my thread on the replacement of the cockpit floor of a C Dory 25 2003 vintage. If you have one soft spot which is noticable, there will most likely be much more than you think.

http://www.c-brats.com/viewtopic.php?t=5823 There are also photos of what we did in the "Thataway Album".

Yes, remove all of the bad balsa. Remove the thin top layer (one layer of mat in my boat), put in a core--either balsa (or we used Nida-core, which will not rot or transmit water, still use epoxy to fill the edges of all openings. Put on a layer of matt then the core, then biaxial cloth and another layer or two of matt--this will give a floor which will not rot and will last.

416rigby · Posted: Mon May 21, 2007 11:37 pm Post subject:

The boat should have a 5 year warranty on the hull...I'd get the factory involved.

Rick

thataway · Posted: Mon May 21, 2007 11:47 pm Post subject:

I certainly agree that you need to notify the factory. Also a proper repair will not be to just replace the outer surface. In our 2003 boat this layer is only a layer of 1 1/2 oz mat--way too thin. We replaced it with two layers of 1 1/2 oz mat and and at least one layer of 12 oz bi-axial cloth. This is about 10 x as strong as the origional deck. All areas where there is balsa or core has to be sealed with epoxy--not Bostik or polyester. You want significant thickness of epoxy to seal the edges. This is extremely important. When you pre bed the plastic ports, probably the best compound is Life Seal by Boat Life. It is a combination silicone and polyurethane sealant, which adheres well and does not attack plastic.
Each screw hole needs to be sealed. If you put screws into balsa, consider, drilling the core out, and putting in epoxy which you put the screw into. Probably easier and better to use a core which is waterproof.

Dora~Jean · Posted: Tue May 22, 2007 12:43 am Post subject:

Bob, what s/n hull is your '03 CD-25? Mine seems quite strong, does not give whatsoever at any spot I put all my weight on. But then again, I sealed my hatches within weeks of bringing her home from the dealer after noticing they were not sealed.

Appreciate the detailed write-ups on the repair of the core and laminates, will come in handy someday I'm sure. Thanks.

thataway · Posted: Tue May 22, 2007 9:46 am Post subject:

Steve, The hull number is 30. It was built in January 2003. I suspect that none of the factory built boats were adequately sealed at that time. If there was no water standing in the cockpit--there may be no problem. If the cockpit was kept covered, again I would not expect a problem. This boat may have had problems accentuated by cycles for freezing thawing with water having gotten into the core. Nothing wrong with a cored hull or deck, IF they are properly built and sealed.

Dora~Jean · Posted: Tue May 22, 2007 10:33 am Post subject:

Mine came out of the mold in July'02. I have a few minor hairline cracks at each end of the transom, I doubt they're big enough to even get water in them. I plan to seal them with some type of flexible compound, maybe polyurethane.

thataway · Posted: Tue May 22, 2007 1:41 pm Post subject:

Origionally I would have agreed with the cracks were due to too resin rich gel coat--but after looking at the way the boat is constructed, it is do to the way that the loads are distributed, and using resin, instead of glass and spreading the load out. I would expect that boats which are run hard and bang into seas, will have more cracks. Also that boats will larger motors will tend to have larger cracks in the corner of the transom where it meets the splash well.