A leaking hull-deck joint is not uncommon to Cape Dories or any other boat that is built in a similar manner and sailed in rough condition. Most hull-deck joints are built in the same fashion as the Cape Dory. When the boat is being built the deck, made in a separate mold, is lowered down onto an adhesive that is applied to the hull's inward turning flange. Then, the deck is drilled many times to accommodate machine bolts. Next, more caulking is applied to the top of the joint and the wood toe-rail is laid down to cover the joint and screws are used fasten the toerail through the hull-deck joint. Finally, the genoa track is attached to the toe-rail and is bolted through the toe-rail and the deck. I counted nearly 115 holes per side (not including chain-plates, stanchions, or turning blocks) as reflected in the picture to the left. Eventually, water makes its way under the toe rail and it leaks into the boat.
I previously removed the toe-rail. The next order of business was to clean out all the old caulk which I did with a lot of acetone, scotch-brite pads, and a chisel. Next the entire deck and topside (this was just one step in what eventually would required complete sanding of the deck and topside) was wiped down with Interlux 202 dewaxer to remove any trace of mold release wax or silicone.
The sharp right angle of the hull deck joint would need to be grinded down to a more rounded edge to allow for the glass tape to bend around the corner. I started this process using a ½” round-over bit in my router. Where the angle was greater than 90 degrees (amidship) the router could not get deep enough into the joint to round it over. This area, about 10 feet long, will require a bigger round-over bit or some careful sanding. The photos below show the before and after and a fence I added to the router to control the depth of the cut in the bow area where the joint edge is significantly less than 90 degrees.
The plan for lamination is 4” wide tape, then 6” wide, and finally 8” wide 10oz finishing cloth. I did not remove the bolts securing the hull deck flange. They are counter sunk and the heads will be covered with epoxy then the glass tape. So, they should not be able to leak water into the hull. I figure they will add something to the strength of the joint.
For the actual sanding I used the 5" Porter Cable Right Angle DA RO sander with 40 grit paper PSA disks. However, today I paid with double digit compound interest for the relatively easy job sanding the topside yesterday. The gelcoat was hard and thick. I estimate up to 3/32-1/8” in some places. It was tough going. It took about 5 hours of sanding and 21 disks to get 30 feet of the horizontal deck edge sanded. I think the vertical face of the hull will be much more difficult. Nonetheless it has to get done. I am sanding carefully so I create as smooth a bevel as possible to reduce the amount of fairing that will be required.
The scaffolding has worked out great. What a pleasure to be able to walk all the way around the boat without having to move ladders and planks. The sun was out. The temperatures came up to about 60 degrees. I opened the doors of the boat shed and all in all enjoyed the day sanding away . . . .
Tomorrow I will begin sanding the cabin sides and the cockpit which I have not started on due to the work on the deck and the hull-deck joint. This is about the time a 36' boat feels like it's a 100 feet long.
As mentioned the conditions in the shed are terrible. But, there is no sense doing a complete shed clean up till the cabin sides and cockpit are sanded. Then, perhaps, I'll perform a good cleaning. No sense in going hog wild though sense there will be much more sanding before the deck is completed.
I mixed up some unthickened epoxy and wet out all the holes and the edge of the deck where it was uneven or jagged. I let it kick for about an hour. Then I mixed up 407 thickened epoxy. I added little 406 to make it thicker and less likely to sag. I spread it out on a 12"X12" piece of 1/4" scrap plywood to slow the exothermic reaction. Then I applied the epoxy with a 4" drywall knife. It took a couple of hours to go all the way around the boat. Working off the scaffolding made it much easier than working off ladders. After I applied the fairing compound all the way around one time, I mixed up some more epoxy and went back and hit any low spots where the fairing compound had retreated down in the holes. Tomorrow I'll wash the hull-deck joint down with water and a scrub pad and dry with paper towel to remove any amine blush then sand it smooth. I'll apply more compound to any area that needs it and then early in the week I'll begin applying the three layers of biaxial tape.
Yesterday afternoon I laid out and cut all the biaxial tape to the proper length. I was able to get good quality 4" and 6" wide tape but the 8" wide I had to cut from a bolt of 17oz biaxial. It was not hard to do. I made a 1/4" plywood template to make sure all the pieces would be the same length and squared on the ends. I used the template and a marker pen to trace the shape then cut it out with my neighbor's massive heavy duty scissors.
I will use 105 Resin and 206 slow hardener. I plan to start on the bow and establish a staggered joint. The first 4" wide piece will be 5' long, then the 4" piece will be 3 1/2' long, and the 8" piece with be 2' long. After that, all the pieces will be 4' long. I will butt joint the pieces of the same width and cover that butt joint with the wider tape above working my way around the boat. I'll cover the whole thing with release fabric in an attempt to make the work cure as smooth as possible. It may be more trouble than it's worth. With luck, I might finish in one day as I would like to get a complete "chemical bond" between all the layers.
This morning we taped up some painter's plastic to keep any epoxy sags from running down the hull. Then we basically ran an assembly line. My wife mixed the West 105 epoxy resin with the 206 slow hardener. Bruce wetted out the biaxial tape, rolled it up like a sausage and handed it up to me on the scaffolding. I laid the tape on the joint, "squeegeed" out excess resin and applied the release fabric. I kept the area to be glass-taped wetted out with epoxy slightly thickened with 406. The weather was a perfect sunny 70 degree day. We opened up the shed and has a nice breeze as we worked. The epoxy never got away from us kicking before we were ready.
It took 80' each of 4", 6", and 8" wide tape for a total of 240 linear feet. We used about 2 1/2 gallons of epoxy. I thought it would take much more epoxy.
The speed of the job was made possible by having three people working together, pre-cutting the tape and release fabric yesterday, and preparing the work areas last night.
I am very happy to have this behind me. In a day or so I'll begin the long process of fairing in the hull-deck joint.
After pulling the release fabric I suited up with a tyvek suit and full respirator and sanded the new lamination with the right angle DA RO sander loaded with 80 grit paper. I went though about 20 disks. I concentrated knocking down the edges and giving the whole thing a light once over sanding. The temperature is dropping tonight to the high 30s. That meant no fairing today. I spent an hour or so cleaning up the shed. Below are some pictures of the new hull-deck joint after the sanding.
Later in the day I marked up the template for the biaxial patch for the holes where the engine control box and the wind instruments were located. If all goes well, I will apply those patches tomorrow along with sanding and applying the fourth coat of fairing compound. The 410 microlight sanded much easier. I went back to the long board and also used the 5" vertical axis RO sander with 80 grit. I am still working on my sanding technique and trying to find the right balance between the different sanding tools. After vacuuming the hull deck joint and surrounding area I did a good wipe down with acetone. Then I began applying the third coat of fairing. I used mostly 410 Microlight today with just a little 407 and a touch of cabo-sil (406). I used a stiffer 5" knife today. It worked well. I focused on filling in the bevels between the gelcoat and the widest layer of tap--both above and below the hull deck joint. There is still a little washboard but it is definitely coming along. I used a total of about 15oz of unthickend epoxy today or about 30oz of fairing compound.
Later in the day I marked up the template for the biaxial patch for the holes where the engine control box and the wind instruments were located. If all goes well, I will apply those patches tomorrow along with sanding and applying the fourth coat of fairing compound.
After three days of fairing and sanding I thought it was time to tackle the outside edge of the deck--the roundover, if you will. I wasn't sure how I was going to get smooth even coverage over the edge. There was no good way to do it with a dry wall knife or a squeegee that I could see. I kept thinking about it while I was working the flat part of the tape the last couple of days. It finally occurred to me that I needed something flexible that would bend around the curve. I cut up an plastic container that formerly held deli-meat. I cut the curved corner part with scissors and trimmed up the edge. Then, I mixed up more epoxy and added the usual ingredients--407, 410, and 406. I used a dry wall knife to spread some of the compound along the edge. I dragged the flexible plastic along the edge applying even pressure which smoothed the epoxy out along the edge. It gave pretty good coverage. I used a total of about 8oz of unthickend epoxy or about a pint of thickened epoxy.
I took the small amount that was left over and started filling in the holes in the cabin top that were from the "eye-brow" trim. I am not putting it back on . There are 28 holes on each side of the cabin top. They leaked quite a bit.
In preparation for priming the the boat with Awlquick--a two part medium build epoxy primer, I vacuumed the deck and then wiped it down with acetone. I thin applied two coatings of unthickend epoxy to any fairing that had 410 microlight in it. Apparently, the same thing that makes it easy to sand makes it vulnerable to some solvents. I sent the MSDS sheets of the thinners and paints I'll be using to prime and paint the deck and topsides off to West Systems for their chemist to look at. In the meantime they thought it would be safer to lay a coat of epoxy over the micolight. The picture to the right shows the shiny epoxy curing on the hull-deck fairing. Tomorrow I'll wash the deck, wipe with Interlux 202 dewaxer-degreaser one more time, then sand with 120-150. In few days I'll prime.
Yesterday I finished filling all the holes for the portlights. I wasn't going to do this, but the more I thought about it the more it seemed like the best thing to do. I initially thought if I left them unfilled I could use them as a guide when put up the new plywood on the inside. But it occurred to me that I would never get the holes to line up exactly with the portholes. So, by filling them I start new. A safer bet I think.
Last night I spent some time using my laser level to level the boat and strike a line to mark the waterline. It was an exasperating event. I had read Tim Lackey's description of how he does it and it seemed like a lot of work. How much easier it would be with my laser level. Wrong! All I did was chase the beam around. The problem is in the SRF I can't strike the whole hull at one time Just one side and I have to move the laser twice to do it. Tim's method essentially builds the surface of the water around the boat with stings and then you level the boat to a planar surface and mark the waterline. So, I'll do use that technique on Sunday and be ready for priming on Monday.