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Epoxy Chock Build |
I have put together this page showing how I built the experimental epoxy chocks. They may not be any better than steel or aluminum but it was something I had to get out of my system and one more part of my boat that I can say was home made. So far I have used them once and they seem to be working fine. I will update this page with my findings as I use them good, bad or otherwise. They cost less than 100 dollars to build using 2.5 qts of West System and some cloth that I bummed from Mike. Even if you have to buy the cloth they still should cost less than 100 bucks to build. The first layup that I tried resulted in a lot of flex so I put the chocks back in the mold and added more layers of cloth. I left out the photos where I did a second layup in an effort to make the process easier to understand. The next time I make a set of these I am going to try a lighter layup but add a gusset to the inside edge to compensate for the light layup. I started with a mold made from 3/4 plywood with pieces of 2x4 screwed to the sides. The mold is 20" long giving me plenty of stock for two chocks.The filler piece that goes in the middle is 1 1/4 thick. The filler piece makes the slot for the runner to fit in. I made it 1 1/4 thick so that I could add a 1/8" steel shim to each side of the runner slot thinking this would keep the runner from chafing the epoxy. Because we were all out of waxed paper I found something that works much better by accident. Meat wrapping paper is the best release product that I have ever used. It released from the cured West System with out even tearing. I stapled the wrapping paper to the mold surfaces and cut the 10" wide cloth in twenty inch long pieces. I am not sure of the wieght of the cloth. I call it fab mat but it is actually a diagonal weave with a mat backer. It is quite heavy cloth. 20 pieces of cloth were used total. Sorry I didn't take many pictures during layup for obvious reasons. In this photo ten layers have been wet out and layed in the mold. The filler piece is then added to the mold. I then took the ten layer flap and wrapped it up around the filler piece making a sandwich out of the filler piece. This gives a total of 10 layers on each side of the filler piece. This part was a little messy but Mike happened to come strolling into the shop during this process so four messy hands are better than two. At this point I wet out 10 more layers of cloth and layed them in the mold against the filler piece. This gives a total of 20 layers on what will be the inside piece of the chock if it were bolted on a rear beam and 10 layers on the outer edge. I was not fancy with the wet out process and didn't worry about rolling out air etc. Once the mold is clamped up things will work out. Probably the West system pros out there will cringe at my methods but I use what I got. Once all of the wet out cloth was in the mold I put on the last peice of the mold and clamped the daylights out of it making sure to clamp the filler piece down first while leaving the other clamps just snug but loose enough to allow the cloth to pull around the filler piece as I clamped it. After clamping I tilted the mold on the table so all the excess would run in the same direction. There was a lot of excess resin running out onto the table but I would rather have to much than to little Fresh out of the mold I'll probably never go to boatbuilding heaven using a table saw to cut through 20 layers of cured west system but it was an old blade anyhow. I forgot to photo a few steps but basically, I cut steel shims to go in the runner slot. I found one 1/8" shim and one 1/16" shim to be a good fit for the runner. I roughed up the shims with a grinder and glued them to the chocks using West System and clamping them with the runner in place as a filler. I also drilled and tapped the top of the chocks to accept the 5/16 bolts that hold them on. In this photo the chocks are being lined up on the rear beam. After the chocks were lined up and bolted I faired the edges of the chocks to the rear beam. Love that grinding and sanding!!! In this photo you can see the steel shims in place. I also used a spruce shim between the chocks and rear beam. The large nut shown is an eyebolt for staywire connection. The runner bolt is in place with the nut and washer glued on. This shim is not slotted for a reason. It was the only thing I could find at the hardware store that was 1/16 thick. I did make top plates for the chocks out of a West System layup but not fully understanding thier purpose elected not to use them. As an update to this page I have used these chocks 30 sailing days so far with no problems. |