Workong on the deck reinforcement, any suggestions are welcome!

[Udockjulio]

The underside of my deck is supported with what appears to be 1/4" ply epoxied in. I am nearing the end of the arduous removal of the rotted material and old resin to expose a clean working surface but I am unsure of how I should go about supporting the new ply for curing. Two Possibilities I have been considering are

A: drilling small holes and using Battens fastened from the top to conform and clamp.

B: Coat boards with epoxy and support it from bellow with stand clamps (or 2x4"s with hydraulic jacks.)

I'm open to anything but am working with a tight budget. Also what tools would be good for removing the remaining material and getting straight cuts overhead? I have been using a hammer and chisel to my own dismay.

What it looks like now:



The epoxy and ply I am trying to remove without damaging the deck.





New chain plates I fabricated and the start of this project of removing rotten materials

[Udockjulio]

Quick correction, 1/2" ply is what was originally used under the deck.

[JonathanSail]

That's tough work you're doing there. I hope you are somewhere that isn't too hot!

I'm probably not qualified to weigh in on this, but there are a lot of folks that are on this forum so hopefully they'll chime in. More information from your end may be useful and there are a lot of details with this project that come to my mind after looking at the photos from the best way to join the new core/reinforcing to the old, to preventing the rot from reoccurring, etc.

From what I can see, using a rotary cutter of some sort to define the edges of what you are removing and then using a chisel/prybar and similar to remove the biggest chunks would be where I would start with the removal and it looks like what you've been doing. From there I would get after it with a grinder with 5 inch coarse sanding discs, like 40 grit or so. That should make a great mess and suck a lot but should get you down through the old epoxy to the original deck for the most part. Smaller tools can help you get to GRP or ply in the tight spots and a shop vac and/or grinder with dust collection can be very good for this type of work along with great dust shielding and ventilation in the boat.

From there I'd consider how you will join the new layer with the old, ie should you just butt the two together or feather the joint in some way to avoid creating a flex point at the seam between the panels. Beyond tapering the wood edges for mating you may also have luck with glassing the seam to spread the loading, etc.. The overall structural situation of this part of the boat has to be considered in the repair but you may already have a good plan for all of that.

How to hold the new layer into place will in part depend on how firm the deck is above the repair, if it will be refinished etc. I bet there will be more good ideas but Drilling and screwing into the new panel from above may be a good option or it may not work if the skin is too flexible or if the deck isn't to be refinished. Using props from below can work really well if they are able to apply pressure uniformly over the panel so that it doesn't distort or pull away in low-pressure spots. 1/2 ply is pretty stiff though for the type of props that I have in mind so your 2x4's and jacks will probably be easier. You will want to spread the load of these supports though so that you get full and even contact between the deck and the new reinforcing layer. Also, if there is a lot of curvature and the deck is flexible you have to watch for the new panel pulling the deck down flatter than it was before and a solution if that is likely may be to ad multiple thin layers of reinforcing which can be laminated in place so that they take the shape of the deck and reinforce the deck shape vs. fight against it over time.

Good luck figuring it all out and I hope you get to move on to easier projects soon.

Jonathan

[micah719]

Rather than use slabs of ply, would it be possible to use thin strips of timber in layers....cold molded. You can lay up as many layers as you like, you know what you're getting as far as timber quality, there are no seams, and the individual pieces are light and handy to get in. Not sure what the situation is wit any nearby structural things like bulkheads, hatch coamings, or a compression post, but if you're doing your deck you could tie those other things in as well. You can steam timber that is so thin to form it to shape with a kettle and a piece of pvc pipe. Sourcing timber will be relatively easy, as you only need thin strips. Supporting the ply, whether little strips or big sheets, do what plasterers do and knock up some props that you can wedge in between deck and deckhead...it works for flimsy stuff like plasterboard, you'd just need more of them, wedge them evenly and securely and leave them in longer. Just don't inadvertently glue them to the boat, or you may have just built the frame for two dozen compartments a foot square. Unless you can use two dozen one foot square cabins.......

[DeepFrz]

I would suggest you use high density foam or balsa core. Cut strips that you can handle and apply according to directions. Its going to suck but will be better than trying to form 1/2 inch plywood to the deck camber. You can use small pieces of wood and screw through them and into the deck to hold the core that you choose in place.

[Udockjulio]

All of these ideas are great! Though some are out of my budget. After a whole lot of overhead sanding and grunt work I have the area mostly prepped.



Much larger area than I first though necessary but it pays to do it thorough I suppose. And I have decided to lam two layers of 1/4" in opposite directions to strengthen the deck. I tested some out the 1x2"s cut to the proper length seem to work perfectly well for support from bellow and the 1/4" ply conforms extremely well!

[roverhi]

This is plywood bonded to the underside of the deck, right?? Our old boat had a similar set up, not for reinforcing the deck, but stiffener for the hull and support to fasten a handhold that ran along the edge of the cabin. Used #10 pan head screws just long enough go through the bottom glass on the deck sandwich screwed in from underneath. Used polyester resin with filler to glue the plywood to the underside of the deck. Would probably use epoxy resin with a filler if I was to do it today. The polyester resin has held up for more than 30,000 miles and three cruises to SoPac, though. Screwing in from the top would probably be best but will mean more work filling all the pukas.

[nickn]

If it was just a matter of supporting the deck's own weight and preventing it from bowing downwards, I would try laying a frame 2x1 pine across the deck and hot melt glue it to the deck. I have done this successfully with a couple of sailing dinghies that I had to take apart to repair about 50 holes that some idiot had hammered into them. I just had a whole heap of pine that I hotmelted to the deck and to each other with the occasional nail from the nail gun. Sailing dinghies are really thin and flexible when they are separated into a hull and deck/tanks so I had to keep it all within a couple of mm

The hot melt is not very strong, but then it might be strong enough (don't walk on the deck) if you spread it out and if it is just strong enough then you can peel it away later.

[nickn]

You are lucky with the polyester, it should come with warnings, but then you can buy it in the hardware store. I've been involved with the repair of a few old polyester boats and the hull is great but wherever they couldn't lay it up wet and had to scratch, sand, etch or whatever so they could add engine bearers etc they always came up with really poor joints. Some of these boats were from reputable builders, but they were quite old.

[Udockjulio]

First layer in



Took a a second to get the mixture right but the slow hardener epoxy was quite nice to work with. Putting in the second layer today withe the bulkhead and new chain plates!

[micah719]

Looks good! Probably feels good too, to be making progress. A bit like your boat being in hospital....

[Udockjulio]

Yes! Especially nice as a live on it. Which makes my quite glad to be done grinding fiberglass for the time being :]

[zeehag]

looks kind of similar to the way we did my deck backing plate for the forward section of my forepeak---i used 3/4 ply and epoxied it and then epoxied it to the overhead using supports in similar fashion toyour pix...worked great.

[micah719]

Yes! Especially nice as a live on it. Which makes my quite glad to be done grinding fiberglass for the time being :]