Chain Plate Knees and Chainplate Angles.

[Windcall]

Atom, Thank you for all your help,

I just installed new v berth shelves and am cutting plywood for knees for chainplates, The ones I took out, looked like one 3/4" ply plus one 1/2" ply and fiberglassed in... so the whole wood knee was 1 1/4. It had about 1/4 of fiberglass wrapped around it.

I have made (2) 3/4 ply's to laminate together. Is this thick enough for knees, or should I up it to 2". I have lowered the shelve from the 6 1/2 tall to 10 1/2" tall. Also I am putting on the chain plate side a 1/4" laminate same size as the knee over the ply so that would make a total of 1 3/4" chain plate knee. Also the top of the Chainplate knees I increased in size a bit from 6 1/2 from hull to 9 1/2.

The second problem I have is the old chainplate knees were thrown away by a family member and I now have no idea what angle the chain plates need to be coming out of the deck. I can sort of guess on a couple by the direction of the hole through the deck but that will go away as soon as i start repairing the core around the exit hole. Is there a way to estimate or get a degree approx that the chainplates are from vertical on your boat.. should be about the same no? or is a good guess enough lol. I put a long strip of 1 1/2 x 1/4 thru the chain plate hole to get a angle that it probably was, if I mirror this on both sides is that a good guess or what do I do..

Any advice or direction you can give me would be appreciated.

[atomvoyager]

Your combined knee thickness of 1.75" plus fiberglass is more than enough. I always glass the knee on all sides - to deck, hull and shelf. The angle of the lower shroud from vertical is about 12 degrees. You can calculate it yourself by drawing a scaled down triangle of dimensions of spreader height (about 18') and distance from mast to chain plate (about 4') and reading the result off a protractor. However I don't try to get that much angle on the chain plate but just angle it a couple degrees until the bottom hits the hull with the point where it penetrates the deck the same as original. The oversize chain plate is way too strong to bend in that case. That simplifies the installation and maintains the more important angle of keeping the turnbuckle attachment point as far outboard as possible. I do try to get the chain plate in line with the angle to the mast by using a string from the mast base to slot in deck as a guide. It doesn't matter if the knee is not exactly to that angle, I just dry-fit the chain plate to it by wrapping in thin plastic sheet and laying it against thickened epoxy. I do make sure there is at least 1/8" gap all round the deck hole so I can get butyl down there as I found that the lifecaulk (polysulfide) I used to use sometimes leaks after only a couple years but the butyl never does. I use a schaefer cover plate to press it down and maintain the seal.

[svMira]

Make the hole bigger so it seals better. Counter intuitive, but makes sense. I redid mine with Lifecaulk summer before last, but can well imagine that your idea works much better. Mine previously had sealants just added and all squished out. I dug out quite a few different instances of sealant, including one where they just slathered sealant on the outside the cover plate in an effort to seal it up. Even with my cleanup, I was rather dubious about how little sealant there was left under that plate to effectively create a proper seal.
Butyl it is next round!