Bill is correct that generally speaking the vertical part of the end grain of balsa is a closed cell wood and water does not migrate normally. It appeared in my 22 that this area was sealed with foam or some other similar material. Some areas of the TC 255 cabin top to vertical pilot house walls are sealed with foam, others are open--the area I am sepecifically concerned about is on the back, but extends around the sides, there is a lip of the cabin top above. In a several foot area one can get a finger between the cabin top and the end of the laminate. The total area which needs sealing (in my opinion) is about 20 linleal feet. I just measured the gap under the lip aft. The height (top to bottom is just over half an inch (index finger easy is inserted and end grain felt)--The depth which I can put a tape measure into this gap is about 3/4" (the tip of the blade on the end of the tape measure is 3/8" thick, so it is not just a very narrow area which is void). The interior is sealed with tape and resin, so that no water would get inside of the boat. I don't know exactly what the thickness of the Balsa in this area is, but I would guess by feel that it is 1/2" at least--maybe 5/8".
As Bill says, the front has loads of sealant--and is more likely to take water up under this area. I do disagree with Bill slightly--and this is based on my "Autopsy" of twenty hurricane wrecked boats (maybe not a good comparison with the well built C Dory)--which I did this last January as part of our non destructive testing project. Exposed balsa (the end grain goes to the laminate, and the cell length [walls of the cells] are between the laminate at right angles to the laminate, so that the actual end grain is not exposed). We chopped up 20 cored boats --some foam some plywood and some balsa. We macrophotographed after smooth finishing the laminates and core. We then used these as controls in the lab using our ultra sonic methods (both direct, echo, sender/reciever on back surface and pitch & catch--separate sender and reciever with variable distance and angles foth those who might be technically minded). We found that there is some minor intrusion of fungi into balsa laminates, but for the most part they survived the 15 months since the storm amazingingly well.
However we have put some samples which are the vertical grain, as in the C Dory and mold will grow if water stays there on a flat surface without drying. The difference between the PNW and Florida, is that the weather is hot most of the year, humidity is quite high, and spray can get into a creavice and then be hydroscopic, and allow detiorration to occur. Has this happened in a C Dory? Not to my knowlege. I have said, that I am very perticular and want to avoid problems with cored hulls and other structures. When I am talking about cored hulls, I use C Dory as an very good example of an excellent core--where the laminate is thick enough--and totally sealed--so that problems do not occur. But I think that under the environmental conditions we have here, there is a potential for problems, so I am sealing this up.
The process of repair is a quite a bit more than a few minutes. First any debris (and there is quite a bit) has to be removed, then the area lightly sanded, and cleaned with acetone, the gelcoat masked below the caulk line, a device has to be fabricated to allow the compound to reach around a 90 degree bend and fill the void areas. Finally the gloved finger or a plastic spatchula has to smooth and fair off any excess butyl caulk and the tape removed.
I agree with Bill, that this problem is not a reason to reject C Dory as a boat--and I really feel badly that Seeker feels that this is, because it is something which can be resloved. If you really want to know about core problems read:
http://www.yachtsurvey.com/cored_hull_bottoms.htm
http://www.yachtsurvey.com/structuralissues.htm
http://www.yachtsurvey.com/Fiberglass_Boats.htm
http://www.yachtsurvey.com/core_materials.htm in which David Pascoe says:
"By sandwiching end grain cut balsa between two layers of fiberglass, this creates the effects of a truss and significantly stiffens up large flat panels. It was a perfect solution for floppy decks but for one thing: balsa is wood, and it will absorb a lot of water. As long as you design the structure right, with no fasteners going through the core, water won't get into it and it won't be a problem.
That notion is well and good but for one thing: Boat builders understood this, but no one else did. So people went merrily on their way drilling their decks and house tops full of holes to mount things. Water then got into the core and 10, 15 or 20 years later we're back to floppy decks again because the core eventually rotted. Next, they started using balsa to stiffen up hull sides because builders realized that they could cut some material out, ostensibly save a little money on thinner laminates. A few builders decided to go whole hog and use balsa for the entire hull, with disastrous results. One cannot use balsa underwater and not expect it fill up with water, which is what they all did. Ergo, the rule in boat building became: core only to the waterline.
This worked out pretty well because people generally don't go drilling the hull sides full of holes like they do the decks and house tops. Of course there were always a few, but by and large, balsa coring in hulls sides worked out just fine. Made the boat much quieter inside, too."
and:
http://www.yachtsurvey.com/more_on_cores.htm
You may say this is too much of David Pascoe--but although he may take things to the extreme to make a point--virtually all of what he says is valid. My recommendation to all boat buyers is to read David Pascoe's complete set of articles--and if you are really inquesitive buy his books.
So--knowing all of this, I still purchased a C dory and feel it is a good hull--and as I emphasized that these are quality control issues. The C Dory has been traditionally a West Coast boat--mostly PNW and inland, with few on the East coast or South--that is rapidly changing, and I would not want reputation to be damaged by core problems. Thus I am going to be filling all of these voids.
