Chainplate Knees

[Brian Duff]

Hi Yawl,

Whats the best fix?

THis boat was built with inboard chainplates mounted to fiberglass knees attached to the hull. The knees are of 2" wood center and 3/8"+ fiberglass mat/roving and very well attached to the hull. 5 of the knees have had water into them and the wooden center is gone GONE gone.

Whats the best fix.

My logic follows this path : the fiberglass is the structure,and it is well attached to the hull. The wood inside was never attached to the hull by anthing more than bondo. The wood inside is softer than the fiberglass, so provides no real sheer resistance for the bolts. The wood inside was not being used to creat a stiff, cored panel. The wood inside was essentially a form to build the knee over. The only other purpose I can see for the wood inside is compression resistance for the chainplate bolts to be tightened against. Sound?

So the fix i propose is to install compression tubes at each of the 10 bolts for each chainplate, and a drain hole at the bottom of the knee to help any water still in there to dry out. Rebed the chainplates with solid glass bosses around them in the deck to prevent any further leaks. Sound.

The two fiberglass guys I have had come in to look at doing this work have both suggested either to put tape over all the bolt holes and pour resin in till full (what BS is that?) OR to cut a side off of a knee, replace what wood can be replaced, and glass over the hole.

Problem I have is that right now there is a solid fiberglass structure in place and they want to cut it completely down one side, the make another secondry panel to replace what they can of the original strength. Doesn't seem like the right solution to me. I talked with a fellow rigger at a nearby shop, and he is in the same boat as me - compression tubes. Why don't the glass guys get it?


or maybe, What don't I get?

[Jack]

This is probably was off base Brian, but I was searching around to look for ways to beef up my cabin sides to accept a synthetic chain plate I have an idea for. Considering the same "knees" you are describing, minus the wood and priblems I hope.
I came across this PDF. I will throw it out as you description of the fiberglass with the wood core sounded like this race boats structures. I am serious about going to soft deck fittings. Just matter of time.

http://www.equiplite.com/2009/Frames...plates_WEB.pdf

[Ian McColgin]

Since the water to cause the rot had to come down through the chainplates, I'd double check the deck before deciding much else. Even if the deck is not wood cored, water can travel along and between the layers of glass causing interesting problems.

Were this my boat, I'd replace the glassed in debacle with good wooden knees blind-bolted and epoxied to the hull. How exactly you shape this depends on whether the chainplates are oriented fore and aft or athwartships.

If you really want to avoid woodword and a proper job, make quite a few small drill holes pointed slightly down, aim a heat lamp at the thing for a few days, and then inject lots of CPES. Frankly this is more expensive and almost as much work as just making a proper knee, but it will turn the wood mush into a cellulos/epoxy matrix of considerable strength and durability and will feel more comfortable to anti-woodies.

G'luck

Ian

[Brian Duff]

we have cut the deck out and installed fiberglass 'deck bosses' above each chainplate, that fit tight to each chainplate, to ensure no leaks develop in the future.