Compression Block Replacement

[Night Watch]

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.

 

[Night Watch]

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.

 

[Night Watch]

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.

 

[Project_Mayhem]

Very nice work! I've had good results cutting G10 with jig saws and oscillating tools. Blades dull but no faster than tough steel.

 

[Night Watch]

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.

 

[Project_Mayhem]

Were you able to smell the fiberglass when using the wet saw?

 

[Night Watch]

Were you able to smell the fiberglass when using the wet saw?

Can't say that I did.

 

[Night Watch]

Test fit the screw jacks, a little bilge painting and a couple pictures of the project.

 

[Project_Mayhem]

How long did it take to grind out the block? What did you do to support the mast with the 2x4's?

 

[dlochner]

I've cut G10 with a cheap DIY wet saw with a diamond blade. Cuts like butter with no dust and cuts straight. Drill holes with a glass cutting bit in a drill press with a shop vac to suck up the dust.

 

[Night Watch]

How long did it take to grind out the block? What did you do to support the mast with the 2x4's?

Grinding out the block took about 10 days. I only worked an hour/day on it. Working on your head is not very comfortable. The closer I got to the hull the slower I worked due to how aggressive the die grinder was. As far as the mast support goes I got lucky with the support in the bilge holding up the cabin floor. It is a solid sheet of epoxy all around under the cabin floor, so I just jam'd two 2x4's up at an angle to take the load off the post, that's all I did, as you can see. However, I did loosen my standing rigging, took the boom and sails off as well.

 

[Project_Mayhem]

That's an incredibly simple method to support the mast. I will definitely keep this technique in mind when it comes time to redo my mast step

 

[Night Watch]

That's an incredibly simple method to support the mast. I will definitely keep this technique in mind when it comes time to redo my mast step

I had the mast off for upgrades this last summer and I found that I could lift each end of the mast by myself, so I figure the mast only weighs around 200lbs, so there's not much dead weight to support when doing this job especially since a lot of the load is uplifted from water pressure on the freeboard which is squeezed inward thus lifting the cabin top slightly. Added benefit of doing this pier side.

 

[Night Watch]

That's an incredibly simple method to support the mast. I will definitely keep this technique in mind when it comes time to redo my mast step

https://groups.io/g/Catalina30/topic/74731981

the above link is probably the best version of a compression post replacement that I've found.

 

[Project_Mayhem]

I had the mast off for upgrades this last summer and I found that I could lift each end of the mast by myself, so I figure the mast only weighs around 200lbs, so there's not much dead weight to support when doing this job especially since a lot of the load is uplifted from water pressure on the freeboard which is squeezed inward thus lifting the cabin top slightly. Added benefit of doing this pier side.

Mine was down for this exact reason. I initially found the mast step had sunken in. I cut into it and found that the wood was solid so I assumed that the block was the issue. Before diving in I had a very knowledgeable friend take a look at it. While the compression post was pushing into the ceiling, there was no evidence that the block had failed. The floor was perfectly level. He concluded that there was a void in the ceiling where there should have been filler. I made up the height difference when I put the mast step back together.

I have a 94 SR wing keel. I could barely lift one end. I'm estimating my mast to be 300-400lbs. I can normally lift 200-250lbs.

https://groups.io/g/Catalina30/topic/74731981

the above link is probably the best version of a compression post replacement that I've found.

I agree. George is also pretty responsive to questions.

 

[shemandr]

Night watch, would you post a pic close up of the die grinder bit that you used and maybe the spade bit. I’m having a hard time imagining removing all that wood with what looks like a small bit.

 

[Night Watch]

Night watch, would you post a pic close up of the die grinder bit that you used and maybe the spade bit. I’m having a hard time imagining removing all that wood with what looks like a small bit.

I tried several different router bits but these worked the best. The spade bit was useful at first by plunging into the block, chewing up a lot of material as it went in, but getting it all out especially along both sides the die grinder worked best. I even chew'd up a lot of epoxy as well.