by GreenLake » Tue Sep 04, 2018 2:51 am
Welcome to the forum.
I think the cracks, if they go through, are indeed a possible source of the water. If you want to be scientific about it, you could fill the boat with water when on the trailer and add food coloring. . . but you write "water was dripping from it" - if that was more water than just the few drops that would have fit the crack, I think you have your answer.
The fact that the cracks were "patched" also speaks to them having been a source of leaks. Just smeaing some goop over a thin crack like this will do nothing to fix it (as you are witnessing). However, a lasting repair is doable and not all that complex. (It helps if you can put your boat on its side with the help of 2-3 people - see copious discussions about turning over these boats, or just do it . . )
For DSII centerboard removal, see older posts in the "DSII only" section of the forum. Much repair stuff is general, but the DSII has some specific stuff about its CB, and that info we try to keep in that section. (You should be able to tell whether you need the board removed for access - not something we can diagnose for you from some photos).
Crack repair starts with grinding open the crack. Ideally with a 1:12 bevel (i.e. 6" wide for a crack that's 1/2" deep). Then you get fiberglass cloth and layer it with laminating epoxy. Pretty good instructions can be found on the West System or System Three websites. That type of repair is not only watertight, but restores any strength lost because of the crack.
Where the crack goes up into the CB well, you may run into some limitations as far as placing laminate. In those areas I would use 3M High Strength Marine Filler. It's a polyester-based paste that's thickened with glass fibers. It will fill gaps to 1/4" depth/width and is super strong. Normally we prefer epoxy because it bonds more strongly, but I've made good experiences with this stuff and would recommend it for hard to reach areas. (You still need to grind/scrape open any existing cracks).
On the flat parts of the hull, I would be very generous in the amount of laminate ground away, because the existence of the crack indicates that there's some damage to the laminate and that may well extend. Best to get anything that might be weakened out and replace with new layup.
The instructions will tell you this, but for epoxy, the key to success is careful and precise measurement and thorough mixing. (If you've never done any work with epoxy/fiberglass, or it's been a while, start with a flat piece that you lay up on a sheet of wax paper on your work bench. That sample, if it turns out well, can later be used as backing plate if you ever have a repair where there's an open hole, because laminate needs a surface to be applied to).
Note that you need to paint any epoxy for UV protection. If you drysail your boat, many paints will survive brief immersion, otherwise you'll need to get some stuff rated for below the water line.
~ green ~ lake ~ ~