PART 2, Repairing Wet Core in Cockpit Floor of Tanzer 22. Rebuilding.
The worst part of any job is cleaning up and preparing the surface to be repaired (or painted). That phase of the Tanzer 22 floor repair is thankfully mostly done.
The old wood is mostly stripped off. There is still plywood under the overhang and stuck to the fiberglass sheet on the floor.
Now the challenge is to put the floor of my little Tanzer back together again so that it is solid and looks reasonable.
The Tools are ready for surgery.
Removing the last of the wood
Ready to remove most of the wood stuck in the overhang. What's left is not that rotten and once dry will be covered in resin and imbedded in the floor. I don't dare be too aggressive for fear of damaging the delicate layer of fiberglass on the sides. The slivers I'm removing now are not particularly rotten anyway. The bottom sheet of fiberglass layer is solid but the sides are quite thin and seem to be lacking resin. The port side is the worst and has several holes. The mirror has proved to be of great use in inspecting the underside of the floor and makes it easier to work under there.
Drying out any wood left
We are having daily rainfall so nothing dries very fast. The wood fragments are fairly dry and pieces left are small. The floor looks like wood but it is a thin sheet of fiberglass with a damaged attachment area and assorted holes around the perimeter.
Repairing the big hole in the tanzer 22 floor where the attachment plate was located.
My hair dryer discovers a new career.
Working from the underside was easier than I had expected.
I had prepared a piece of plywood and taped an old towel over it. I had then put it in a plastic bag and taped that in place so that the top face of the towelled board was smooth. I put my patch on the plywood board, covered it with resin then pressed the board against the bottom of the floor where my hole was located. I pressed it and wiggled it back and forth to help it stick to the bottom. I had cleaned up the area and painted epoxy resin on the underside using my mirror. I used pieces of foam to solidly wedge the board up against the floor. This pressed the resin soaked patch against the floor.
I put weights on the top to squeeze the patch solidly in place from the top.
Once again my tool collection comes in handy. The tool box and cleaner provide some weight on top of the patch. They don't cover the whole area of the patch but that did not seem to matter. The foam helped distribute the weight.
The patch is just about invisible under the floor. It is almost transparent to light so not really visible in the photo. It went on very well and other that a couple of small bubbles is pretty much perfect. It is smooth and solid and the edges are very well attached to the bottom of the floor. The holey area now feels secure and more rigid than the rest of the floor.
Look no more holes. Strip of 6 ounces fiberglass repairs the holes on the port side of the floor.
Covering damage and holes.
I went around with resin and wet the perimeter of the floor. The underhang had wood fragments that needed to be well wet out and I wanted to make sure that the underside of the overhang was also saturated. It was never well wet out by the looks of things. I was quite generous with the resin and I expect that I will have some drips through the holes.
I then went around and put a strip of fiberglass in the overhang where the surface was damaged or there were holes. The starboard side was more robust and did not need repairing. The repairs help strengthen the future bond to the plywood.
Carbon Fiber layer.
I had measured and cut the carbon fibre before wetting the perimeter and it was easy to wet out the floor and unroll the cloth to the floor. It takes some brushing to get it wetted but luckily the kevlar goes translucent when wet and is a good gauge. The cloth is quite stiff and the floor not perfectly smooth but mostly it went on quite well. The floor had wood embedded that were tricky to remove without damaging the thin floor layer. So I had scraped as best I could and accepted that the floor would not be perfect. (compromise is the story of my life!!) The cloth extended under the overhang.
I worked with 3 speeds of hardener. I used a medium speed for the perimeter and a slow for the carbon fibre. This turned out well. The perimeter was just starting to thicken as I finished going around, about 45 minutes. It took about 1 hour to do the carbon fibre so the slow resin gave me enough time to work.
I used carbon fibre because I had it. It provides great stiffness but since I am adding plywood it is overkill. Carbon, kevlar and glass are quite similar in strength. Where they differ is in stiffness.
The weather has been really nasty this spring. Nasty if you are trying to fiberglass. Today, unlike last week, there was no snow, only torrential rain. it's quite cosy in the boat under my tarp. I used a white tarp so the light is fabulous. This means I have to think what speed I estimate the epoxy will set. Mostly I err for too much time. Also, if I'm working with a larger quantity it tends to set off faster. I like to use MAS resins because they don't blush.
Cleaning up the old floor
layer of my Tanzer.
Back to sanding fiberglass. Since I planned to reuse the original top layer of fiberglass/gelcoat that I had cut out it needed to be cleaned up. There was lots wood still sticking on to the underside and resin ridges where the gaps of the plywood boards had been filled with resin.
I used a nice old wide chisel and then used 60 grit in the random orbital sander. It was much quicker to do than I expected. I brought it home and could work on a workbench. Much more comfortable than kneeling in a boat. The glass sheet is certainly not the same thickness throughout. It varies at least a sixteenth of an inch or more in a couple of places. I guess when they made the top cover there was no real need to be perfectly even. I'm thinking this will mean I will have to have enough epoxy thickened goo to allow for the different thicknesses.
I've used the table saw to cut the long sides but I have to use my least favourite tool in the world. My poor Makita rotary saw doesn't deserve this bad rap because it has always behaved perfectly well, has never kicked back, and works very well. It did its job perfectly well once again.
I have since then bought another saw. It has 2 blades that rotate in opposite directions and don't kick back.
This is where the floorplate attaches so I've drilled oversize holes and painted epoxy on the edges, I've filled the holes with thickened epoxy. Later I will drill through the epoxy for the bolts to attach the floorplate back on. The paint cans are there to put pressure so the stuff doesn't ooze out of the back. I had some extra resin and used it on the edges of the plywood. I'll be coating it again when I lay it down.
I bought a half sheet of Meranti from Noah's. It is really nice to work with. Quite light and strong. 9 plys on a half inch section. The top veneer is also thick enough to sand and not the paper thin stuff you often see. it's not very pretty but very strong.
I had a AH HA! moment. I remembered that the floor is actually laid on a bulkhead roughly in its middle. So the pressure on the sides is not as big as I was afraid. I guess it's just a senior's moment. I had figured this out but had myself a good panic when I realized the poor condition of the bottom fiberglass layer.
Checking for sagging
Calm weather after the gale. (did you see my photos, pretty amazing weather.) I spent most of the day cleaning up debris of all kinds. When I went to work on the floor I checked the floor for sag to see how much I would have to adjust it. I was expecting to see some sagging so when I placed a straight board across the boat I was very surprised to see it was pretty level. Part of the reason is that when I patched the bottom from the underside I had pushed it up some and tried to level as much as possible. Still success always surprises me. Reflections and crooked carbon fiber threads make the floor look a wonky BUT it's NOT.
Plywood needed grinding to compensate for a couple of blips I had when I cut the top layer off. I'm amazed, the floor is level.
Checking the plywood for size and for thickness
I tried the plywood in place to see if it would fit. It was slightly too large in a couple of places. I guess I had a hiccups or two when I cut the floor out. It was a simple thing to use the belt sander to remove the extra plywood from the sides. Once done I checked the thickness and found to my great surprise that the thickness was dead on. Again the goddess is smiling on me.
I had ground a couple of bumps out of the carbon fibre. There was a glob of tangled threads and also piece of sawdust that had made a bump.
Finally I tried the top layer of fiberglass and it aligned well and the thickness was good. The holes lined up well with the plugged oversize holes. The position of the plugs is about an eight of an inch off and the oversize plugs will compensate. I'm ready now to resin all this together.
Filling the overhang
I used a thickened mixture of epoxy, silica and wood flour after coating everything with resin. Strength is not an issue because I already have a layer of carbon fiber-kevlar cloth plus another of just plain glass, plus the reinforcement under the deck. The first filler sagged when I put it in because it was actually quite warm and as the resin warmed up it got runnier after being placed. I adjusted the thickness and the fill stayed in place. I had prepared some small long sticks which I painted in resin and imbedded in the filled epoxy.
Put a coat of resin on the plywood. Just in case you're wondering the bright light is actually SUNSHINE! The first sunny day in weeks. I let everything set. The thickened resin in the overhang is medium speed so it gave me about 45 minutes of working time. I went to have some lunch and when I came back the epoxy had set but was not hard.
Putting it all together
I made up a large batch of resin thickened with silica. It was quite runny. I did not add any microfibres or wood flour because they don't make a very flowing mixture and I wanted the slurry to flow and fill hollows. I used slow set epoxy to give enough working time to get everything placed and adjusted. I wet the floor with epoxy then added the slightly thickened resin on both the board and the floor. I had a thickness of resin of at least 2 mm.
At this point I was a completely stressed out. I lowered the plywood and tapped it in position. I stood on it and realized that the board had cupped slightly in the sun. Luckily it was very slight and weight straightened it.
I prepared another contained of epoxy to glue in the glass sheet. After mixing it I kicked and spilled my epoxy on the plywood.
I scrambled madly to scoop it up. I also spread some on the plywood that luckily needed coating. Some resin seeped in between the plywood and the floor and helped fill any gap.
After a quick tidy and change of gloves, I thickened the rescued resin and smeared up the plywood and bottom of the glass sheet. The floor went down without any further problem.
I used straight sticks spanning from edge to edge to check that the floor had gone down evenly. I placed various weights where the floor needed to go down but mostly the thickness was good. The slow set resin worked in my favour here and hopefully will flow and even out the adhesive inside the floor sandwich. At this point I think I have a floor.
Left the floor set for a day. It's been cold and epoxy just is not setting up fast. Gave it a quick sand but not much to remove. I had a drip in the drainage gully from kicking over my mixed resin but other than that nothing much to sand.
I tried to drip resin in the gap between floor and plywood to see if any would flow in but very little was needed. I mixed up a batch of microsphere thickened epoxy and applied it generously to my edge. It is a garish red and easier to sand. I used quick set epoxy but after 3 hours it was still not set. Cold and rainy again. I went home by way of the paint store. I got primer, paint and a matting agent. I would like the paint to be closer to satin than to really shiny.
Cold weather this spring makes this job seem endless. I have to wait for epoxy to set at every step.
A final coat of glass cloth. The easy sanding filler is not that easy to sand!!
After sanding the filler flush with the floor I measured out my cloth. I'm using 6 oz. I cut the cloth the full width of the floor and cut out the drainage holes. The cloth is not a perfect rectangle. Because the floor dips down to the drains the area of cloth is actually wider in that spot and narrows towards the front and back. I rolled up the cloth, carefully cleaned the floor and vacuumed. I started at the cabin entrance and gradually wetted down the cloth. I used medium speed hardener. I added a second layer of cloth to the area leading to the cabin because I cannot access it from under to reinforce it as other areas.
Weather was cool so it took a while to kick off. Now after hardening I have a floor!! It is the magic point where if I did nothing else but attach the floor plate I could safely use the boat.
Came back the next day and was able to put down 2 more coats of resin. I could feel the cloth in many places. This is a total of 3 coats of resin and the floor is surprisingly smooth and shiny. The last coat was applied on a warm floor and it flowed well before kicking off in less than 10 minutes. The trees have been shedding little flowers so the floor is covered with them in the photo but they will sweep up. I had to remove my tarp cover since we are launching tomorrow. I still need to clean the inside of the boat but the floor is rock solid. The next steps are really a finishing/refinishing project. I will sand the cockpit, put a primer and paint.
Completed repair awaits paint.
As I read this page I seem to be pouring gallons of resin in the floor. In fact I used less than a third of an American gallon container. I did not have large gaps except around the overhang and this was only about a quarter inch. I tend to mix sparingly and often prepare measured but unmixed resin and hardener if I need to add some in a hurry. If I don't use it it can be returned to the containers or covered and used later.
Return to PART 1 of the Tanzer 22 Floor Repair
This web site reflects my personal ideas and doesn't represent anyone else's point of view. My methods are my own and I am not proposing them as the only or best way of doing things. Use your brains!