R22 Discussion Group

I love butyl tape and use it everywhere that does not require adhesive

Reuben: 

No, the deck is not solid fiberglass. In most cases it is comprised of a sandwich construction with plywood between a heavier fiberglass deck and thin inside liner. I understand that later models of the boat utilized a foam core which would not have the problem of core rot but I don't know when that change occurred. What year is your boat?

In my case the plywood separated from the deck skin resulting in a soft deck that would flex when you walked on it. I thought that the soft deck was due to rot in the core so I cut the duck in half immediately in front of the cabin, removed the bow section of the deck entirely, separated the liner, removed the core and replaced it with marine plywood encased in epoxy and then reinstalled the unit. This gave me the chance to examine the core construction in detail. What I had is not necessarily what you would have. My boat is a 1976 and clearly boats of that vintage were not built to the standards of  later boats. Apparently these early boats were built by contractors who I can attest cut many corners.

In my case the core was the cheapest plywood (i.e., not even exterior) with large voids. The layers of the plywood had separated and the plywood itself was attached to the deck skin with occasional strips of some sort of sealant which had long past let go. I could remove the core with my hands. 

Except for one area of about 1' square where the head air vent came through the deck there was no rot so the extreme measures I took turned out to be unnecessary. Carefully injecting epoxy into the core might have been sufficient. The problem was that until you look inside the deck, you it is difficult to know what is wrong or how well the injection process is working. 

Knowing what I learned from the deck reconstruction I was able to use the injection method quite successfully on the side deck - so far as I can tell. By looking at the core from where the deck was removed I could tell that delimitation had occurred there as well but without any sign of rot. Knowing what the problem was I was able to inject thickened epoxy into the core without going through the core - in which case the injected epoxy would have simply pooled in the space between the core and the liner. The liner is solidly attached to the core on the cabin top but not the side decks. By avoiding this problem I could inject the epoxy into one hole until it came up through the next hole giving me a pretty good indication that most of the voids in the plywood and the space between the core and the deck skin were filled. 

By removing the solar vent in the cabin top I was able to see that the core, at least in that area, appeared to be solid. Certainly there was not flex in the deck there so I concluded that I could leave the cabin top as is.

I am not telling you this because I think that this is something you should do - quite the contrary - it is simply to describe what the core was like for my vintage of boat. I have posted pictures of the process and the state of the core in previous times but if you or anyone would like to see them and can't find those pictures in the archive I would be happy to post them again.

Whenever a bolt is removed from a deck it is a very good idea to determine whether water has made its way into the core and to also ensure that the hole is property sealed with epoxy before the bolt is replaced. If water is coming into the boat there is an excellent chance that it was also making its way into the core unless the hole was previously prepared properly. 

The best way to prepare the hole that I have seen is to enlarge the hole going through the core without enlarging the hole in the fiberglass deck and liner skins. I did this using a dremmel bit that looks like this: https://www.leevalley.com/en-ca/shop/tools/power-tool-accessories/burrs/31016-hss-carvers-burrs . It has a shank that is about 1/8" and a cutter cylinder that is about 1/4". The bit will fit through the deck hole and then by moving it around you remove wood creating a hole below thr surface that is about 5/8". Check the wood dust that is removed to see if it is wet or appears rotted. If there are signs of rot/water, try remove more of the core to get back to good wood. If you still have signs of rot you might need to consider a more extensive fix.

Put tape over the hole on the inside liner and then coat the hole with un-thickened epoxy and then pack it with thickened epoxy. Once the epoxy is set re-drill the hole for the bolt. In my experience it is MUCH easier to drill the hole when the epoxy is set - solid but not sticky - but before it cures completely. In this semi-cured state drilling straight through is much easier. Once cured, the epoxy is much harder than the surrounding material and the drill bit will want to wander. Using a brad point bit also helps. This gives a solid and waterproof plug between the deck and inner skins. 

All this is a bit fussy but not difficult to do and gives you reasonable assurance that the deck core is protected. You really really want to avoid having to replace sections of the core.

Graham Stewart
Agile, Rodes 22, 1976
Kingston Ontario

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Graham Stewart

Leak at the bow....where to look first