Compression Block Replacement

Jan 9, 2025
56
Catalina 30' SR John Wayne Marina, Sequim, WA
After a review of the several compression block replacements available on the forums, I decided to go ahead and replace mine before it became a serious problem. Yes, mine was starting to give way, (losing adjustment travel on my standing rigging) but after I had it all out and had a chance to examine it, I found that it was wet through and through, but not rotten. I found that the perfect tool for the job was a die grinder with a 6" extension using a router bit. Also, this job can be done pier side rather than on the hard and actually I think the hull shape in the water, rather than on the hard, helps in relieving cabin top pressure off the compression post (as the keel weight draws the freeboard inward). Additionally, I loosened the standing rigging and removed the boom and sails. I added two 2x4s to support the mast weight. I was surprised to find that my compression block was not an oak block but rather laminated plywood! It did not come out easily with a chisel resulting in the purchase of a die grinder.
Progress is slow as I like to allow 24 hours of curing between laminations under a heat lamp. So far, I've laid up 8 layers of G10 (1/4" and 10mm thick) alternating with fiberglass matt, using west system epoxy mixed with high density filler. Also, I'm using Gflex epoxy to fill voids as I go. I decided to go with fine thread 3/4" SS bolts (2) which are welded to 3" diameter support bases. The support bases will be embedded in epoxy.e09d990d-acf9-4bf4-9123-c198a5c53020.jpg7c40df86-81e0-4ac4-b490-a90b772cedea.jpgIMG_4138.jpgIMG_4139.jpgIMG_4153.jpgIMG_4164.jpgIMG_4165.jpgIMG_4161.jpg
 
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Jan 9, 2025
56
Catalina 30' SR John Wayne Marina, Sequim, WA
A spade bit is also handy. Also, I decided to seal off the shower drain as I have no shower in the head.
before anyone asks, yes, I checked the cabin top under the mast this summer on the hard when I replaced the standing rigging, added a new mast base and upgraded chainplates. There was a noticeable air gap between this compression block and the underside of the cabin sole.

One other detail; I affixed a 10mm thick plate of G10 with 10 layers of matt to the underside of the sole for the screw jacks to push up against. Not pictured yet.

I've seen a few questions about how to cut G10. I'm using a wet tile saw and doing my cutting in the cockpit of the boat. I'm contouring each piece by hand with no risk of loosing a finger to the saw blade.
 
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Jan 9, 2025
56
Catalina 30' SR John Wayne Marina, Sequim, WA
Last layer of G10 laid up yesterday. Going to let it cure over the weekend under a heat lamp. My finished gap for the screw jack is 3.625", just enough for a 1" spacer on top of a 1" support nut w/lock nut. Which will give me up to 1" of base/epoxy support to cover the screw jack base.92320A387_7a4c23c7-20e5-4d8c-8268-4bc7c20e6b57@4x_638059353921802393.jpg92320A387_18-8 Stainless Steel Unthreaded SpacerX.gif
 
Jan 9, 2025
56
Catalina 30' SR John Wayne Marina, Sequim, WA
Very nice work! I've had good results cutting G10 with jig saws and oscillating tools. Blades dull but no faster than tough steel.
Thanks! I've cut G10 with a table saw before. What I didn't want to deal with this time wearing a respirator/dust mask and dealing with the dust, which is very bad for you if inhaled. I had a lot of cutting to do and the wet tile saw didn't get dull.