Projects Below the Waterline: - Through-Hulls - Rudder Port - Hole in the Keel - Applying Barrier Coat
My boat had ten through-hulls . . . or more correctly, nine plus a transducer. All the though-hulls needed to be removed. In a perfect world I would not have any through hulls. But sometimes they can't be avoided. However, the goal is to have as few as possible--less to go wrong, less to maintain. I need to have one for the sink discharge. I need to have one for salt water intake. I had originally planned to cut out the cockpit and reverse the slope from front to back draining the cockpit above the waterline so that I could eliminate the two through-hulls dedicated to the cockpit scuppers. And though it may sound odd, given the extensive nature of this refit and modification, I have, for the time being, decided against chopping up the cockpit. Thus, those two through-hulls will remain. That equals four . . . for now.
Removing the through-hulls and sea-cocks was not that difficult . . . once I had the right tool. After I unbolted the sea-cock and spun it off I tried hammering them out but they would not budge. The through-hull flange (the part on the outside of the hull) has little tabs sticking out into the hole part. So I went to Lowes and bought some steel bar of the correct width. for the two different size through-hull. I hacksaw them to the length I wanted and gentle hammered them up into the through-hull. Then I used used a pipe wrench to twist them off. Despite the 5200 they came right out. No sweat.
Update: on 10 November 09 I saw that Jamestown Distributors sells a through hull removal tool called a "Step Up" tool used to remove through hulls. It looks like one tool will fit many different size through-hulls. But it cost $40.00.
12 Apr 10
I spent the majority of the day patching the old through-hull holes. I was able to get all eight patched. I basically followed the West Systems guidance located in a PDF file on their web site called "How to Fill Machined Holes in Fiberglass Boats." I used "example 8." Though I have already ground down a similar bevel on the inside of the boat I have not applied the inside patches yet. I need to stay focused on the external parts of the boat so I can finish the primer, barrier coat, and bottom paint while the weather is cool.
Below is a series of photos that depict the sequence I used to patch the through-hull holes. Very simple and straight forward. A couple of things to note. Though it is counter-intuitive, the widest patch goes against the hull first. This provides the best bond according to West Systems. I also use release fabric when I can. It prevents amine blush from forming, it allows me to squeegee out the excess resin which makes a stronger patch that conforms better to the surface it is bonded to, and it protects the patch from shredding due to pressure applied from the squeegee.
The diameter of the ground out area is driven by the thickness of the hull. West Systems recommends a 12:1 bevel. So, a hull that's 3/4" thick where the hole is would have a 9" radius bevel from the outside edge of the hole to be filled which would be a patch nearly 20" diameter!!
You can make it smaller doing two things. First, I ground bevels on both sides of the hull--inside the boat and on the outside--which meant I only needed to bevel to half the thickness of the hull. That cut the radius of the patch in half to 4.5". Still too big. Second, I glassed in a 1/4 inch thick epoxy puck I made by pouring epoxy in a small plastic mixing cup, then popped it out of the cup after it cured. I ground it to size to fit the hole and glassed it into the hole with thickened epoxy. I completed that before Christmas and the arrival of cold winter weather. That reduced the thickness of the hole to be filled to about 1/4" thick on each side of the puck. This means the radius of the bevel only needed to be three inches from the outside edge of the hole or about 6" diameter. Much better. The number of layers of biaxial is determined by how thick an area you are filling and how heavy a material the biaxial is. I am using 17.7oz biaxial which is about 1/16" thick when wetted out.
After I ground the bevels, I traced the outside bevel and the through-hull hole on the same sheet of plastic with a sharpie pen. Then I cut the tracing out. I knew how thick the hole was thus I knew how many layers of biaxial I needed. Then I made a corresponding number of concentric circles between the larger tracing of the bevel and the smaller hole in the center of the tracing. Then I started with the largest tracing, laid it over the biaxial, traced the size/shape on the cloth, and cut it out. Then I cut out the next size tracing from the plastic, laid it over the biaxial, and cut it out and so on and so forth till I had a stack of biaxial circles that matched the tracings. In reality, I placed the outside of the puck about 5/16" from what would become the faired surface so that equal five layers of biaxial. The inside patch will only require about three layers of biaxial.
I stacked all the wetted out layers together and apply the entire patch at one time. I smoothed it out against the hull with my gloves--I always were latex gloves whenever I handle epoxy or solvents--then I covered it with the pre-cut release fabric. I squeegee it firmly working from the center of the patch out to the edge and scrape off all the excess epoxy that come out deposit it in a plastic bowl to cure--then I throw it out. After I was satisfied with the patch I placed the precut sheet plastic which is larger than the release fabric and placed a 3/8" closed cell foam disk on top of that. The foam is from an old sleeping mat. Next I placed a small round 1/4" ply disk (small disk if it is a concave surface or a bigger square piece of wood if is it convex). I propped the whole thing in place with a dead-man stick to keep pressure on it and ensure it cures tightly and in the right place. Tomorrow I'll pull the stick, plywood, foam, plastic and release fabric. The patch will be ready for sanding and fairing.
Consequently, this is the same technique I used to make the new deck over the balsa-core I previously repaired on the boat. I used the same technique to fill the instrument holes, engine box control hole, etc. It is basic epoxy hole repair 101.
Prop up "dead-man" sticks in place.
After I removed the release fabric I sanded all eight of the patches with a RO sander and 80 grit paper. Then I vacuumed out the dust and wiped them down with acetone. Next I applied 407/406 thickened epoxy to each of the patch areas and began the process of fairing. It took two applications to fair it properly. I am still amazed at all the holes in the boat. Most boats are like this. Not only does every through-hull become another potential for a disaster but it really increases the maintenance one has to do on one's boat. And if you don't do it, or delay it because it has become to onerous then the change of a through-hull failure increases. Keep it simple. I wanted to eliminate the two through-hulls for the cockpit scuppers but there was no real good way to do it without cutting out the cockpit and reversing the slope so the cockpit would drain at the aft end and out above the waterline. That is the way the boat should have been built. So, I will have four through hulls. The two scuppers, one sink drain, and a salt water intake. The sink in the head, if I have one, will drain into the grey-water box. That gets pumped over the side via the main manual bilge pump.
While the fairing compound was curing, and in-between rolling on the barrier coat, I went out to the SRF and rummaged around in the boxes of boat stuff I have. I dug out the four bronze seacocks and through-hulls I'll use on the Far Reach. Two will handle the cockpit scuppers, one will support the galley sink drain, and the fourth will support the saltwater intake. The first three are 1 1/2" and the saltwater intake is 3/4". I put a wrench on them and they came right apart. I may lap them very mildly but I'll wait till they are all apart, washed in mineral spirts, and cleaned up before I decide. ABYC no longer requires the through-hulls to be bolted to the hull. If I do bolt them it is much harder to do maintenance as the seacock will not come off unless you pull the through-hull. That's something to think about. I also pulled out my rudder post stuffing box and picked up some new flax. I have some Teflon packing material on hold at West Marine as I would like to try the technique that Nigle Calder recommends. He suggest sandwiching the Teflon packing material in-between the traditional greased packing flax.
Who would've thought it takes so long to clean up some bronze seacocks and through-hulls.
I spent a large part of the day cleaning four seacocks and through-hulls. These are the four I selected from the 10 that I took out of the boat. The were pretty groady and covered with green verdigris. I took them completely apart and kept each seacock and its associated parts together so they did not get intermixed. Then, I washed them individually in a small bucket of mineral spirits. Next, I washed them in hot soapy water and brushed on a paste made up of flour and vinegar. I let it sit for 30 minutes or so. I washed it off with water and a scrub brush. I'd say about 80 percent of the verdgre came off. I am satisfied with the results since they are just going to turn green again anyway. The tapered barrels look OK as do the main bodies of the seacocks. I have mixed feelings about using them. Though they are very strong bronze fittings the tapered plug seacocks are notorious leakers. I think the bronze ball valves with the stainless steel balls are better in the long run. But new fittings are not in the budget. It would run about $800 to replace these four seacocks. So, I'll see if I can make them work. They need to be lapped so I'll do that tomorrow. I ordered a small sheet of G-10 that should arrive in the next day or so. I'll cut it into backing blocks for the seacocks and have some left over for backing blocks for deck fittings.
In the mean time I'll wash the hull and prep it for barrier coat. I'd like to have that completely by the end of next week. I also cleaned up the dyna-plate I removed a few weeks ago. I filled the old bolt holes in the hull with biaxial patches inside and outside the hull. The bolts--for lightening grounding--came out in the hull where my grey water tank will be so I'll move it aft. I ordered new bronze bolts and they came today. In the picture to the bottom right the dyna plate is cleaned up and the new bolts are installed. I'll drill the holes tomorrow and then install it after I get a few coats of barrier coat on the hull--same as for the through-hulls.
Spartan bronze seacocks and through-hulls.
I haven't accomplished much work on the boat in the last few days. Instead I have spent a lot of time researching options regarding seacocks. After a lot of reading, emailing, calling, thinking, and a few visits to some marine chandeliers I have decided not to reinstall the Spartan seacocks. I have been moving this way for awhile but anything that pulls me off my rebuild budget gets very close scrutiny. However, this is the right decision for several reasons. First, I don't have a lot of confidence in the Spartan seacocks, not because they are old or poorly made, but because there is some corrosion on the tapered plugs and I have no reliable way to make sure they won't leak. Second, they were leaking when last in the water, and the plywood backing plates were rotten and disintegrated when I removed them. Third, they were very stiff and difficult to operate. Fourth, I don't want to reinstall them and find out upon launching they are leaking without a recourse to repair them or replace them without rehauling the boat.
What to do? There is no question the Spartans are well made. They are classic, heavy, cast bronze, seacocks. Properly taken care of they can last decades. But, if they start to leak, and many do, there are not a lot of options. Tighten the plug to stop the leak makes the handles hard to turn. Greasing them helps but turning the handles can push the grease off the tapered plugs and they start to leak again. That leaves lapping them. Not hard to do, but if that does not correct the problem, you have no option but to replace the whole assembly. It's a lot of work and they are not cheap.
Groco and Apollo make very strong flanged base ball-valve seacocks. These appears to be a pretty good system but based on what I am reading the ball-valves, though water tight and easy to maintain, don't last as long as the integral bronze flange bases--the ball-valve is the weak link (not unlike the Spartan seacock). So, in 10-15 years you have to replace the whole thing. Many folks have been using bronze ball-valves incorrectly, and dangerously, screwing them directly on to through-hulls. Through-hull walls are surprisingly thin. Also, through-hulls have NPS threads and ball valves have NPT threads. They don't match and it is an inherently weak assembly . . . but people do it anyway because the ball-valves are easy to replace. Just screw off the old one and screw on a new one.
Enter Groco. They have developed a special three bolt flange base called IBVF that has NPS threads on the bottom to screw to standard through-hulls and NPT threads on the top to screw to standard marine ball valves. The only problem with this solution is that the seacock and the handle/valve assembly are two parts vice one. This means that the combination, screwed together is not as strong as a single cast unit. Conceivably, some large object, like a battery or tool box, could break its lashings and fall on the ball-valve assembly during a violent knock-down and break the ball-valve off the flange base allowing water to enter into the boat. With the ball-valve broken off there would be no quick way to shut off the flow of water. You would have to resort to locating and driving the old stand-by wooden plug into a hole of gushing water. Not a good situation to be in.
Part of my education this week included learning that ABYC requires that for a seacock to be approved for below the waterline use it must meet the following standard. "Mounted so that 'the assembly will withstand a 500 lb. static force applied for 30 seconds to the inboard end of the assembly, without the assembly failing to stop the ingress of water.' " So, I called Groco today and talked to the tech department about the new flange base IBVF assembly and how strong it is when used with a separate ball-valve.
Here is what they told me. First, the walls of through-hulls are thin, but the threaded top of the flange base is very thick and the threads match. Second, Groco conducted a series of static test to the ABYC standard on all the combinations I described above. Except for the IBFV system (which I will describe below) all the other through-hull to ball-valve combos broke either below the ball valve or just above the nut on the through-hull at 190 lbs. The Groco one piece cast bronze, integral flange base, ball-valve seacock assembly did not deform or break after having 1000 lbs applied to it. But, the IBVF combo, in the picture to the right, deformed, but did not break or leak, at 992 lbs of static force. Thus, the separate IBFV flange base and screw-on ball valve exceeds by two times the required ABYC standard. Third, the tech rep told me the IBVF combo is UL approved for underwater seacocks and approved by the "Pipes and Fittings Committee" of ABYC as well.
What this means to me is, installed properly to include proper installation of other nearby objects, such as water-tanks, tool boxes, batteries, etc, this combination should be fine. What I really like about it is that you don't have to remove the flange base/through-hull when the valve assembly goes bad. You can just carry a couple of spare ball-valves and unscrew the one that is sticking, leaking, or causing some problem and screw on a new one. And, the Groco flange base will take any standard NPS though-hull and NPT ball valve.
Is there some risk? Sure, but it seem very reasonable to me and a thoughtful well thought out installation will mitigate most, if not all risk. Plus, its not terribly expensive. About $170 for a complete, 1 1/2" through-hull, flange base, ball valve, and pipe to hose adapter as ordered today from Jamestown Distributors.
By the way, though I ordered an entire Groco system, I leaned yesterday that Apollo seacocks are cast and assembled in "SC" . . . that's South Carolina and not South China. I like that. I would have gone with them but I chose the Grocos because their handles are reversible which provides me more options when I install them.
Some additional news is that though I previously I reduced my through-hull requirement from 10 to 4, today, I figured out a way to further reduce the requirement to just three 1 1/2" through-hull/seacocks: two for cockpit scuppers and one for the galley drain. The fourth through-hull, a 3/4" one, was to provide salt water to the galley. What I have decided to do is install a bronze "T" fitting in the hose that connects the cockpit scupper to the seacock. The "T" will be installed below the waterline but above the seacock. I'll screw some reducers to the horizontal barb of the T fitting so I can bring a 1/2" or 3/4" line to the galley and put a ball valve on it to provide us with salt water as needed.
I think this will be a good modification to the boat. It will be simpler and easier to maintain and still more than strong enough to meet the requirements I have for the boat. Here are some links that provide more info on the flange base/ball/valve combo for use as a seacock.
Groco IBVF Flange and bronze in-line bronze ball valve.
There is a lot of info out there about backing plates and seacock installation. I have a lot of books that detail the how-to of this important project. It is apparent to me from my own experience and what I have heard and read about that there are a lot of boats with backing plates and seacocks improperly installed. Though most of the techniques are similar there are differences. What I decided to do after gathering all the info is follow Tim Lackey's technique. He does a good job of balancing a proper job with some common sense. Here is a great log of one of his projects that is well worth the read on the subject of seacocks and backing plates.
I used 1/2" G-10 that I purchased from Jamestown Distributors. It is not inexpensive. The first 2'X3' sheet they sent me was damaged in shipping. I decided to cut the G10 in a pattern that follows the outline of the flange base--essentially a triangle. When I talked to a distributor in Virginia about G-10 they told me it would be too hard to cut with normal blades and I would need a diamond blade to cut it. Tim Lackey suggested a carbon tipped jigsaw blade. I could find neither at Lowes and since I did not have the time to order something special I bought three Bosch steel cutting blades for about $7.00 to fit my 5 amp Bosch Jig Saw. I traced the pattern with an indelible marker making the pattern about 5/8" wider than the flange base all the way around. I clamped the G-10 to the table, but on a long sleeve shirt, dust mask, eye and ear pro, and work gloves. I was expecting a big mess of dust. It wasn't that bad. At first the saw cut the G-10 pretty easily and I thought "OK this will work fine." But, after about 6" of cutting the blade was dead . . . just like that. This stuff is hard. I was able to nurse the three blades I had to get the material cut and I also cut a backing plate for the bronze dyna plate as well.
After competing the cutting I took the backing plates to the combination bench top sander and smoothed the edges. Then I sanded both sides with some 40 grit on a RO sander. I sanded a "round-over" on the top edge of the backing plates too remove the sharp edge and make it easier to paint when the time comes.
Next I located the center of each backing plate and cut a 2" diameter hole with a standard hole saw. No problem. I test fit them in the boat with an assembled seacock. I checked that the handle would be convenient to open and close and also I made sure the winter drain plug was on the low side. This meant the handle was not always exactly where I wanted but I know that the drain plug is no good if it's on the high-side. In the end, I think the positioning for each of the three seacocks handles with be fine. I traced the positioning of the base on the hull with an indelible marker. I had one hole that need to be cut. I drilled a 1/4" pilot hole from the inside of the boat. I went to the outside to confirm that it looked good, then used the hole-saw to cut the hole from the outside to the inside.
Next, I sanded the area the backing plates were to be located, vacuumed, and finished with an acetone wash. I retraced the outline for the location of the backing plates. I mixed up some 406 thickened epoxy and epoxied the backing plates in place making sure the holes in the hull were lined up with the holes in the backing plate. Then, I cleaned the area around the base plate with an acetone soaked rag so as not to leave any epoxy runs, drips, etc.
Last, I laid out all the parts I will need tomorrow to install the through-hulls, flange bases, and seacocks.
All three seacocks were installed today. It went smoothly. I used Tim Lackey technique. I followed the below sequence.
1. I measured the through-hull for correct length by placing it through the hole from the inside. Then I mark on the threads where it exited the hull. Then I add the depth of the threads inside the flange base and subtracted 1/4". This makes sure the through-hulls will not bottom-out in the base before it is fully tightened. 2. I screwed on the bronze nut that came with the through-hull, marked the through-hull for the correct length, and taped the threads to protect them and also to steady the hacksaw blade (I also have a special blade I only use on bronze so I don't contaminate the metal with carbon steel shavings. 3. I placed the through-hull in the vise and cut it to the proper length. I never take more than 4-5 strokes with the saw without stopping and checking the angle of the cut. If a hacksaw gets away from you it is hard to correct. 4. I took a file to the newly cut edge to smooth out the sharp edges. Than I took it to the combination belt/disk sander and ground a slight bevel to the outside edge of the through-hull. 5. I cleaned up the threads by unscrewing the nut from the through-hull--it's only purpose. 6. I dry fit all the flanges, through-hulls, and ball-valves and rechecked the alignment. It is very important to number the through-hulls, flanges and ball-valves. They ball-vlaves don't stop in the same place with different flanges and if handle placement is important you need to use the same combination for each hole. I numbered them all with an indelible pen and marked on the backing plate where I wanted the drain plug to be so I would not goon it up. Also, by using the triangle shaped backing plate you loose some flexibility regarding placement of the ball valve if you did not check the fit ahead of time. If you don't like the handle location you have to rotate the whole flange/ball-valve assembly 120 degrees. A round backing plate would give you max flexibility but is not as clean looking or as easy to cut out of the G-10. 7. Once satisfied with the fit, I drilled the holes for the flange base bolts using the flange holes as the guide. A good piece of advise from Tim Lackey is to drill a hole then drop one of the bolts through from the inside to keep the flange from moving around and throwing off your alignment. After drilling the second hole, drop another bolt through until you have all three holes drilled. 8. Remove the hardware and counter sink the holes from the outside. 9. Vacuum and acetone wash the area to include the flange base and through-hulls. 10. I then gooped up (with 4200) one bolt and inserted it from the outside of the boat (the 4200 holds it in place). 11. I gooped up the flange base to include circles of 4200 around each bolt hole. I took it into the boat and made sure I had the alignment right using the one bolt sticking up to hold it in place. 12. I went back below the boat, gooped up the remaining two bolts and inserted them through the holes. 13. Then back into the boat again and placed the washers, lock washers and nuts over the bolts and tightened them by hand until I saw the smallest bit of squeeze out. 14. I went back under the boat and gooped up the through-hull to include the threads and screwed it into place. 15. I used my home-made through-hull removal tool (see tool page) to tightened the through-hull tight. 16. Then I went back into the boat and tightened down the nuts. 17. Cleaned up the excess squeeze out.
I'll cut the excess bolt length off tomorrow and install the ball valves.
I bought a Milescraft right angle drill attachment for $20.00 at Lowes this morning. It worked great. Without it I wound not have been able to get the drill in to the tight spaces required to drill through the flanges holes. I posted a picture on the tools page.
One more misstep to avoid--though I was very careful about checking the alignment and clearances for all the components, I did not simulate screwing the ball valve onto the flange base over the through-hull hole. To my surprise, I had to remove two of the ball-valve handles to screw the ball-valve barrels on the flange bases after I had caulked and bolted on the flanges. I was lucky today and it all worked out. I won't make that mistake again . . . I hope.
I had left the seacocks lightly screwed on but without Teflon tape or pipe dope until I was ready to install the scupper hose. So, I unscrewed them, wiped down the threads, applied pipe dope, and tightened them down with wrenches.
I decided a while back to use white head sanitation hose. It's approved for below the waterline use and I like the clean white color. yesterday, I cut them to fit and of course the boat monster reared its head. The tail piece on the seacock is 1 1/2" and the scupper drain pipe is 1 5/8". Go figure. I tried all my normal tricks to get the hose on to include immersing the hose in boiling water to soften it, coating it with dishwater soap to lubricate it, and then quickly try to push it on before it cooled. No luck. Today I used my heat gun to carefully soften the hose and it went right on. I didn't tighten down the hose clamps as there is no water pressure to worry about right now.
Its another task accomplished . . . small victories . . . I'll gladly take it.
I have worked diligently to avoid having to do things over. I have made a few mistakes that needed to be fixed . . . but not many. I initially installed Shields white vinyl sanitation hose for my scupper lines. I don't remember why . . . it looked cleaner or something--one of the lines is slightly visible from the interior. Anyway, the stuff was beastly to work with. It does not like to bend and it will not go over a hose barb if it is slightly oversized which the barb on my cockpit scuppers are. I used a heat gun to soften the ends but the stuff does not like heat. It was OK but I needed a more durable proper solution. So, I replaced them with Shields Wet/Dry Exhaust Hose. This is a more durable hose. It is wire reinforced and bends much better than the sanitation hose. I used the same line for the galley sink drain.
I replaced the white vinyl hose with Shields Wet/Dry Exhaust Line.
The Hole in the Keel
As I was crawling around in the boat developing the plan for the self-steering windvane control lines I remembered that I needed to replace the rubber hose that supports the rudder post stuffing box. It required me to remove the self aligning bearing (I have heard it called a pillow block) that supports the upper end of the rudder post just below the coupling that attaches the short extension to the rudder post. The bearing is bolted to a 'thwartship steel beam that is in turn bolted to the longitudinal bulkheads on either side of the crawl space under the cockpit sole. By removing two of the four bolts that hold the beam in place I was able to swing it away from the rudder post and slide the locking collar off the top of the rudder post. I unscrewed the top of the stuffing box but I could not pull the lower half out of the rubber hose which was also stuck to the fiberglass rudder port. So, I used a box cutter to slice the hose open lengthwise (there is no wire reinforcement) and peeled if off. Then, I slid the stuffing box up off the end of the rudder post. That ended boat work for the day while I traveled north to Morehead City to buy stuff box hose and some bullet block for the vane gear control lines.
One of the great things about rebuilding your boat is you get to know every part. I think it also increases the odds that you will be able to make repairs more easily in the future. I will be comforted by the fact that I have replaced this part but if, for some reason there is a problem with it in the future and the circumstances are more difficult, I will already be familiar with what's required.
A few years ago I saw some weeping coming from what I thought was a blister. So I dug it out. It was about 1 ¼ inches wide and maybe ¾” deep. As I have looked at it off and on for the last year I decided it was not a blister but a void from when the hull was made. I thought I would eventually grind down the area around it and fill it will thickened epoxy and then put a couple of layers of biaxial over it, fair it, and be done with it.
As I started to prep it for repair I noticed there was some kind of loose grit in it. So I got a chisel and started digging. Soon I had a large pile of grit and a much larger hole.The hole turned out to be exactly 1 ¾” across and perfectly round at the opening.It was a machine cut hole.The hole goes straight back, maybe and inch, but then makes a sharp bend up. Part of the hole angles up, forward, and across to the port side but does not break the surface there. I kept digging out the grit with a ½” wide chisel till I had created a much larger void kind of like an upside down crescent moon with the crescent going fore and aft. I drew the general outline on the outside of the keel that approximates its location on the inside. Most of the hole goes up with the forward part angling towards the other side . . . it goes almost 4”. I have no idea why there would be a machine cut hole there.
16 Mar 10
Today I asked Tim Lackey for some advice on how to approach the repair.He suggested it was likely not structural but probably some kind of void that a PO had tried to repair and never put a patch over.In other words, they just filled the hole with some kind of resin and never covered it with cloth and epoxy as a proper repair would require. So, water migrated in and reacted with whatever the filler was I was digging out.His advice was to avoid making something that is not structural into a bigger problem.In other words, "do no harm."He suggested that I fill the cavity if I could, but focus on a good patch and if done properly water wouldn't get into the void.Good advice and it framed my plan.
I decided to call Gordon Reed at Robinhood Marine to see if he had any ideas about the nature of the machine drilled hole.He knows the Cape Dories inside and out and has always been very helpful to me whenever I have had a question about a construction related issue.He could not think of any reason why there would be a machine cut hole there.He surmised it was an old repair job but was unsure as to why. He suggested it may have been related to the integral holding tank that used to be in the aft most part of the bilge. This past fall I converted that part of the bilge into a water-tight compartment. In my opinion, this is just one more reason to shy away from integral tanks. If you must have one, I think it should be in an area that you can access and repair if need be. The hold holding tank was impossible to do anything with if it had a problem. The entire aft end of the boat has to be torn out to get to it and it is so deep and narrow you can't get any grinders or cutting implements in there to do any repair work . . . but I digress.
I then called West Systems Technical Service to see how I could fill the hole without creating excess exothermic heat from pouring in a large amount of epoxy into the cavity.They told me to take advantage of the cooler 50 degree day we were having and use 404 high density filler that does not get as hot as 406.They suggested a tube and a caulking cartridge filled with thickened 404.That way I could shove the tube up the hole and fill the top of the cavity slowly pulling it out filling all the air space.
Lucky for me I had all that stuff in my West Systems Warehouse. So, I wetted out the inside of the hole and let is sit for about two hours to get good and tacky. I mixed up a lot of 404 and added some 406 to make it thicker (404 seems to get more doughy instead of like peanut butter). I loaded up the caulking tube and filled the top half of the hole then stuffed a paper towel cardboard tube wrapped with some plastic into the hole to hold the epoxy in the top half of the cavity. Several hours later I pulled it out, filled the rest of the hole with more thickened epoxy, covered it with a piece of sheet plastic and clamped it in place with a piece of foam and 1/2" thick plywood. That is it for now. When I mount the rudder later in the spring, I will grind down a bevel around the hole and cover it will three or four layers of biaxial and fair the whole thing in.
Applying Barrier Coat
In the process of sanding off the bottom paint (click here for more on the bottom paint removal project) the entire hull was sanded with 40 girt. Before I applied the barrier coat I went back and touched up any of the areas that needed some more work--again I used the Porter Cable Right Angle DA RO sander with 40 grit paper. Then I vacuumed the hull and wiped it down with MEK to make sure all the residue was removed. Last night I tapped the waterline. Today, I applied the first coat of barrier coat. It was great to finally get all the repair work covered up. It went on pretty easily. I mixed up a total of three batches. I used a total of 3 1/2 quarts (to include the converter). This amount covered everything except the bare spots on the hull behind four of the popits (and the rudder that I previously barrier coated before I shipped it). Tomorrow, I'll move the boat stands and then apply another coat, this time covering the spots left uncovered today. In fact, I'll probably get at least two coats on tomorrow. You might notice the three spots along the bottom of the keel where it sits on the support timbers that I could not coat of course. I'll attack those after we transport the boat to the boat-yard for final prep and launching.
Today, I also cut out the remainder of the patches for the eight through-hull holes that need to be patched on the inside of the hull. I patched the outside of the holes a few months ago.