Archive for August, 2011
It takes about three years for me to forget how much sanding is involved with regelcoating the bottom of a catamaran hull to get a good finish and fair bottom. It’s a lot. A whole lot. At this point, most of the doing is done and I finally have something to admire! After filling the void and incision I made in the hull, I built it back up using 2.5oz S-glass fiberglass cloth and epoxy resin. I then sanded that smooth and fair(ish) using my hand held, homemade, long board. I then faired with epoxy and micro-balloons and later with bondo professional filler to finish out the surface and fill pin holes.
I also fixed and faired out several dents and chips elsewhere on the hull – including the road rash we acquired somewhere.
The daggerboards on this boat had some pretty serious vertical scratches from sand and other debris in the daggerboard wells – and just from general use. I attacked them with a palm sander and then checking that I had sanded away the scratches by spraying on some dark sandable primer and sanding it away. I was surprised that I still had quite some distance to go to remove the scratches. I ended up getting almost all the way through the gelcoat on one side of each board…so I was going to have to gelcoat more than just the tips. One board had also seen a pretty bad impact and about four inches of the tip was previously repaired but left raw with epoxy and carbon showing. I reshaped that tip and filled / faired it as well.
Everything was then masked and protected. I put brown paper down on the major areas of the garage floor to protect it (I plan on coating it with epoxy when the garage is finished).
It’s go-time for gelcoat! I didn’t have time to take progress photos here because A) I had gloves on with nasty nasty chemicals and b) gelcoat was on it’s way to curing in my HVLP paint gun. Of note, I did purchase a new HVLP gun from Northerntool for about $40 (a href=http://www.northerntool.com/shop/tools/product_200319459_200319459LINK/a). It has a larger tip at 2.3mm and it sprayed the gelcoat quite well. Even with the gelcoat un-thinned, it sprayed pretty well. It could have sprayed a little faster and I would have been happier…but if I thin it 5 to 10% next time, I think this gun will be perfect. After mixing and metering 8oz of gelcoat at a time to extend the amount of time any gelcoat stood in my paint gun (it took three 8oz batches), everything was well coated. I had already prepared my other smaller (1.5mm?) tip HVLP gun with PVA and immediately switched to it and laid down a top skim coat of PVA (poly-vinyl alcohol) that after flashing off the alcohol leaves a saran-wrap-like film and very effectively seals the gelcoat from the air allowing it to cure hard all the way through. I’ve tried other curing systems / additives with gelcoat but find that this is the purest and most foolproof method of getting a full cure. Removal of the PVA is easy – simply peel away what you can and wash off the rest. It’s very water soluble and on takes a few minutes with some water and a rag to remove it completely.
Time to sand some more! Thankfully, I had some seasoned help from Ted Bogardus who sails with me locally. In one day, we had both daggerboards and hull sanded and polished (120 grit, 220 grit, 400 grit wet, 600 grit wet, heavy rubbing compound, light rubbing compound). We had to chase the shade as the sun moved in the sky…the dolly made that really easy. The end result is good – I’m happy and can’t wait to splash it. We do have a little more polishing to do on the sides and top of the boat before that can take place, however…
Be sure to click on this and zoom to 100% on the Flickr site. I’m pretty proud of the fairness of the bottoms – this is not easy to do and requires a lot of mediation with closed eyes while mimicking the flow of water over the hull with your palms to figure out when your “there”.
….and a little cleaning.
strongLearnings: /strong1) when sanding away the orange peel on the bottoms, either go straight to 220 grit or only use 120 just to knock the high spots off. I carried the 120 too far and had to work really hard to get the sanding scratches gone. Even then, I was left with a few spots where the scratches still existed – but they were minor enough to not be noticeable but for the most close inspection. 2) I’m going to try to thin the gelcoat a little. I learned last time that thinning it too much is a bad thing and was left with soft / partially cured gelcoat. I compensated this time by not thinning it at all and left a little more orange peel surface for me to deal with by sanding. 3) Having help is awesome! Thanks Ted.
strongTips I can share:/strong 1) Hotel Key-cards make EXCELLENT resin squeegees. I collect them from sales and service guys to keep a bunch on hand so I can just toss them when done. 2) A top-coat of PVA on top of freshly sprayed gelcoat is a sure fire method to get a solid cure and it cleans up really easily.
Up next; Our good friend Bill at Mainsail Marine has restitched and reinforced the trampoline and it’s ready to go on once the boat is cleaned up and the last polishing completed.
Oh, anyone have any spider removal advice? This is the fourth Black Widow I’ve found around the garage and I’ve about had enough of that (maybe they’re so prevalent because I removed a wooded area to build the garage or all the nooks and crannies with the exposed framing?)…and this woman was a monster!
иконографиясвети илияWith fall regattas and an F18 North American Championship approaching, it was time to put down the framing hammer and pick up a grinder/sander and wheel out the epoxy kit. Our Team Seacats Formula 18 has some areas that needed attention. Both hulls were showing a tendancy to take on water. While a little water in the hulls is normal after a day of sailing, the amount we were getting was a little much. While Frank and I spent a recent weekend training in Charleston, we made a detailed inspection of the boat and found a worrisome crack in the gelcoat on the outboard side of the port daggerboard trunk. You could press on it with your thumb and see some movement…which is a good indication that this feature has gone from cosmetic to structural. Ted Bogardus, who also sails with me often, provided valuable help today to get the boat flipped and start the work on the hulls and cleaning up the foils. Before starting the work, however, I finally found a use for the double stack wood rack I’ve used for the last several years to trailer my A-cat on top of our Nacra 20 to the Keys. It has cut-outs to receive rear and front beams (on a N20) and corner gussets. I thought this might make a great dolly for an inverted F18 and after bolting in four casters, whalla…a great dolly! It works great and I can wheel the boat inside and outside for whatever needs to be done:
So, now it’s time to get to work…here’s the crack (you might need to click to zoom in):
There was also some road rash that the boat got somewhere along the way home from Charleston. I’m guessing a trailer tire kicked something up from the road and punched the starboard hull:
I also found a pretty significant hull leak in the starboard hull at the rudder pintle (a close exam showed that these gelcoat cracks were just cosmetic). I later resealed the rudder hardware to the hull:
I also figured that while I was this deep into the repairs that I should give the bottoms a sanding / fairing. Fortunately, in most areas, the gelcoat is incredibly thick giving plenty of room to remove scratches and rebuff without having to recoat. After going over the hulls with my longboard with 100 grit, 150 grit, and 220 grit, I moved on to the daggerboard trunk repair. Using my side angle grinder and an 80 grit sanding flapper disc, Ted and I went to work and made some nervous discoveries along the way:
I was thinking that we were in good shape now and ready to start rebuilding. When I used my compressed air blower to clean out the incision, I notice there was a spot that kept getting wet when I hit it with air (I have a pretty good air drier so it was unlikely that it was coming from the compressed air supply). Upon further inspection, I noticed that there appeared to be a cavity behind a small void in the seam between the daggerboard trunk and the hull.
I started to get a sinking feeling about this…so I decided to explore it further by opening up the void and putting in a copper wire to see how expansive the void was…watch this: Here’s the full copper wire:
Here it is in the void…yep…it’s easily entered into the interior of the hull. I’m thinking this is a pretty good candidate for a significant leak issue (not to mention structure).
Poop! Now I have to open it all up and figure out how far this void goes and what it looks like so I can figure out how to make it stronger. I’m beginning to think that this void may have been the cause of the crack to begin with. After some more careful grinding with a dremel…wow. I see now that the inner hull skin isn’t even close to being attached to the daggerboard trunk. There’s no filler, no nothing. Just air. I’m glad that I’ve found the cause for the crack – but now I have to figure out how to fix it. Look into my hull!:
I cleaned up the incision removing the jagged edges and making a taper on the edges. I then mixed up some epoxy and cabosil (fumed silica = very hard when cured and awful to try and sand post cure) to make a thick peanut-butter like mixture. I then took a zip-lock bag, spooned the mixture inside, and cut a tiny slice of the corner off to make a cake-icing like bag to inject the filler in the void. My goal was to get the filler to bond the inner skin and the daggerboard trunk and it went in the hull in a very controlled fashion with a very neat finish. It’s possible that I might have to cut an access hole in the hull to put glass on the interior of the hull – but I’m guessing this will probably take care of the issue. Epoxy is, afterall, stronger than air!
After several layers of S-glass, things are looking good. Now I just need to fair it and shoot some gelcoat.
Hot. That’s been the word of the day around here for about two months now. Working outside, especially in the upper level with no ceiling or insulation to offer protection from the radiant heat coming from the roof, is brutal. I’ve been working in the early weekend mornings upstairs until it gets too hot and then moving downstairs until I’ve had enough (usually around noon). I then retreat into the house to catch up on things there. During the week, I’ll sometimes wait for the sun to go down and put on a head lamp to do some work in the garage and office followed closely by a fan.
I’ve been slow to get updates here – I have several to make and will break it up a little into different sections. For now, a simple post about sofit baffles. Sofit baffles protect the vented sofits from insulation and other debris that might block the air flow into the attic. They’re needed especially when you will be working with a blown-in type of insulation. I was a little unsure about the ridge vent roof ventilation system having heard some negative things about it. Since then, I’ve become convinced that most of the time folks have issues with a ridge vent, it’s probably because of inadequate intake ventilation in the roof…i.e., the ridge vent can only vent as much air as can be drawn into the attic. So I studied sofit baffles and settled on this particular ABS plastic type. I had to order these because most of the readily available baffles are of a lightweight foam type that are exceptionally fragile and just tuck straight down into the sofit. They offer very little shielding from the top plate and if pressed lightly, can buckle and fail. You can’t really tuck insulation in with those foam ones without risking breaking them. The baffles I ended up with first staple to the top plate of the wall and they lay across the top plate horizontally toward the roof sheathing where they bend sharply and follow the roof sheathing upwards. A few staples through the baffle attaches it to the sheathing and holds it in place. The molded stand-offs in the baffle allow multiple channels for air to flow from the sofit into the attic space while still allowing insulation to be tucked in deeply above the top plate to reduce any (very common) cold spots during the winter around the perimeter of the ceiling/wall joint. I first thought I was going to use a pneumatic stapler to attach these but the staples were shot so violently that it was shattering the ABS plastic. A manual stapler didn’t have the same issue…so I ended up manually stapling them in place.