Chainplate reinforcement



Here's the way I did it, and ways that might be better.
The selection of the hardware will affect the dimension of the turnbuckle, etc. So, I sketched the rough shape of the tab and various distances so at the store I could layout some different designs based on the pieces they had available. The chainplates were Schaffer and had bends designed into them which had to be straightened by pressing them straight in a bench vise. If someone has the time, it would be preferred to have a shop manufacture the chainplates as flat pieces.
The first task on the boat is to cut the hole in the bench that allows for the lower chainplate to be mounted flush against small notch in the bench structure seen in the picture. This was accomplished with a 5/8 in. wood boring bit, and a Dremel tool with a cutting bit. A jigsaw could also be used by drilling out the corners of a thin rectangle shape and using the jigsaw to connect the holes to complete the cut out. Watch out for screws used to attached the wood at the edge of the bench structure.
Lay the lower chainplate against the notch in the bench where it will be mounted and mark the holes in the bench. I traced the entire hole so it was easier to be sure I could center the bit on the mark. The holes and bolts were 1/2 in. so I recommend drilling 5/8 in. holes in the bench to allow a little slop in lining things up. I drilled 1/2 in. holes (rookie mistake) and had to go back and bore them out to get things aligned.
A 3/4 in. teak backing board was cut from some scrap I kept for years just for a job like this. Likewise, mark the board either with the chainplate or by using the holes cut in the bench. Again, cut 5/8 in. holes to provide a little slop to line things up.
You should now be able to bolt the lower chainplate together. I did not use any adhesive between chainplate and the bench or backing board and the bench, but this would not be a bad idea. I figured 5 x 1/2 in. bolts should be enough. I used galvanized bolts, washers, and nuts with nylon locking inserts on the nuts. Stainless would be fine too. Either way, with 1/2 in. bolts you will pull you bench out of the boat before even one of the 5 bolts fail.
To make sure the location of the upper chainplate bolted into the tab was compatible with the reach of the turnbuckle, I connected the whole assembly together. This allowed me to map out different upper plate orientations' and consider pros and cons. The direct orientation picture may be changed once I see the overall affect on the hull when the mast is up. There is still a considerable vector pulling inward on the tab. I may buy (or have made) a longer thicker upper plate and bolt it more horizontally such that the two plates are connected with a more vertical turnbuckle orientation. This would eliminate the inward force in the current design. At any rate, I drilled the holes for the upper plate directly through the smaller chainplate holes. With just two holes there aren't as many alignment problems as with the lower plate, and used 3/8 in. stainless bolts, washers and self-locking nuts.
With just hand tightening the turnbuckle I could see the affect on the hull and gaps at the top of the small bulkhead. It does not take much to get things back on track. I'll report what I find when the mast is stepped.
Other reinforcement I may pursue.
Add fiberglass tabs or fillets to the back (bow side) of the wooden bulkhead. This area is accessed by pulling the drawer assembly out, which is only held in by 6 screws. A drywall screw works great for pulling out teak plugs. Minwax Red Oak Stain 215 matches my 22 year old teak perfectly when applied to new teak plugs.
Add fiberglass tabs or fillets to the hull and bench structure where the lower chainplate is mounted. There is a lightweight tab there already but could be reinforced pretty easily.
Questions are welcome.

Tad Ilg
s/v No Se'
1981 Newport 28
Belmont Harbor - Chicago
TILGWOOD@aol.com