I have a 78 Hunter 27 with a slight depression around the mast step. It is time to replace the balsa core. I intend to peel off the deck, scrape out the balsa and replace it with something that is not subject to rot. My greatest concren is when the deck piece that is cut out goes back down, I want to get a all the air gaps out and make sure the bond with the replaced core and at the cut seam is at least as strong as it was prior to the deck removal. Any advice would be greatly appreciated. Steve Horswill
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Recoring
I am currently recoring my entire deck on my 1986 Pearson P36-2. I am using Nidacor, which is a plastic honey comb material used on high end boats. Also, under my stantions, I have solid core to absorb the load and stress. My fiberglass guy is using a polyester instead of epoxy for the bonding. You can see pictures of my job under the Pearson forum Greg P36-2
I am currently recoring my entire deck on my 1986 Pearson P36-2. I am using Nidacor, which is a plastic honey comb material used on high end boats. Also, under my stantions, I have solid core to absorb the load and stress. My fiberglass guy is using a polyester instead of epoxy for the bonding. You can see pictures of my job under the Pearson forum Greg P36-2
Under the mast I wouldn't put any Core
I would build it up solid in Glass and resin. For the rest of the core that needs to be replaced I would use CoreCell A500. This is a PVC foam that is very tough, damage resistant and completely rot proof. AS for getting a solid bond mix a batch of short chopped strand with resin trowel it on thick on the new fill and on the cutout piece lay the cutout piece in place and press it down after you have it in place lift it up briefly and see if you have full contact if yes press it back in. If not then butter the thin spots and put it back.
I would build it up solid in Glass and resin. For the rest of the core that needs to be replaced I would use CoreCell A500. This is a PVC foam that is very tough, damage resistant and completely rot proof. AS for getting a solid bond mix a batch of short chopped strand with resin trowel it on thick on the new fill and on the cutout piece lay the cutout piece in place and press it down after you have it in place lift it up briefly and see if you have full contact if yes press it back in. If not then butter the thin spots and put it back.
Phenolic - Airex - End-cut-Balsa
Steve, The balsa you are replacing works well if you keep out ALL leaks. Having said that, Airex and the man-made non-rotting materials are better now. Under your mast, assuming it is deck-stepped with a compression post, use Phenolic a great material for load bearing structures, and commonly in use for this purpose now, I used Teak for my mast; phenolic is better. A big job, but is done all the time by yards when rot is found in a cored deck. NY Nidacor is another one like Airex, Polyester is fine, that is what your yacht is made from amyway, too expensive to build boats from epoxy, other 'issues' too...;-)
Steve, The balsa you are replacing works well if you keep out ALL leaks. Having said that, Airex and the man-made non-rotting materials are better now. Under your mast, assuming it is deck-stepped with a compression post, use Phenolic a great material for load bearing structures, and commonly in use for this purpose now, I used Teak for my mast; phenolic is better. A big job, but is done all the time by yards when rot is found in a cored deck. NY Nidacor is another one like Airex, Polyester is fine, that is what your yacht is made from amyway, too expensive to build boats from epoxy, other 'issues' too...;-)
Aluminum
We put an aluminum plate in our step to replace the balsa. In addition to being 100% rot-proof, it distributes the load over a broader area. Check the archives - there are lots of really good threads on this topic. David Lady Lillie
We put an aluminum plate in our step to replace the balsa. In addition to being 100% rot-proof, it distributes the load over a broader area. Check the archives - there are lots of really good threads on this topic. David Lady Lillie
Check the floor timbers
Steve, I had the same problem on my 81 Hunter 27. However, upon further inspection, the problem was not the deck core but the fiberglass floor timbers that the compression post sat on. The floor timbers were wood that were glassed over. The wood rotted and the glass shell could not support the compression loads. I fixed the problem by drilling holes in the floor timbers with a large hole saw. I then removed the wood through the holes. After all the reminants of the wood were removed, I filled the hollow glass timbers with steel rods. Next, I filled the hollows with a mixture of mortar and sand agragate. To finish the job, I cut an inch or two off the compression post and fitted the end with a robust threaded rod and two nuts, making the post expandable. Using two wrenches, it was possible to expand or contrack the compression post while under sail, giving another degree of freedom in tuning the standing rig. In theory, at least. A nasty divorce resulted in the boat being sold before I could get it out of dry dock. Ralph
Steve, I had the same problem on my 81 Hunter 27. However, upon further inspection, the problem was not the deck core but the fiberglass floor timbers that the compression post sat on. The floor timbers were wood that were glassed over. The wood rotted and the glass shell could not support the compression loads. I fixed the problem by drilling holes in the floor timbers with a large hole saw. I then removed the wood through the holes. After all the reminants of the wood were removed, I filled the hollow glass timbers with steel rods. Next, I filled the hollows with a mixture of mortar and sand agragate. To finish the job, I cut an inch or two off the compression post and fitted the end with a robust threaded rod and two nuts, making the post expandable. Using two wrenches, it was possible to expand or contrack the compression post while under sail, giving another degree of freedom in tuning the standing rig. In theory, at least. A nasty divorce resulted in the boat being sold before I could get it out of dry dock. Ralph
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