Scott Dufour Posted June 5, 2004 Posted June 5, 2004 Before I go an mess this up next week, a quick question. When I glass the centerboard, should I wrap the glass around the really tight turn on the leading and trailing edges? I get the feeling the glass won't want to make that kind of corner after it begins to cure. If I can't wrap it around, how do I protect the weak but critical edges that I know are going to take a beating? Quote
Gordy Hill Posted June 5, 2004 Posted June 5, 2004 When I redid my centerboard and rudder I first used a 3 1/2 inch hole saw to cut a hole for lead shot and epoxy as low on each blade as possible. I taped one side and filled it overfull to account for shrinkage. I really liked the results. At Grahams suggestion, I planed the leading edges back to about a 3/8 inch flat and tacked on a section of 1/4 inch nylon rope that I had soaked in very slow epoxy. After it was nearly cured I took out the tiny nails I had used to hold it in place and faired it with Cabosil-thickened epoxy. After curing and sanding it fair I glassed one side at a time, overlapping just the leading edge each time, giving two more layers of protection. This gives a very solid composite leading edge. Reefs feared me. I finished with a few coats of epoxy with graphite added. I really liked the graphite finish. If I were to do it again I would add graphite to ALL epoxy throughout the procedure so there wouldn't be any white showing through after sanding. I sanded down to 600 grit and got a finish reminiscent of the Space Shuttle before some white started showing. Otherwise I would have gone to rubbing compound and polish! Gordy If at first you don't succeed, skydiving may not be for you. Quote
PJPiercey Posted June 5, 2004 Posted June 5, 2004 When I layed up my rudder and daggerboard I did it in layers so I was able to install about 30 oz of cloth along the edges as a middle core. This made for a very durable edge. Paul Piercey Quote
Brent Posted June 7, 2004 Posted June 7, 2004 I used a procedure very close to what Gordy describes, intalling a 3/16" rope soaked in epoxy on the leading edge and then layering the glass on each side, but not trying to go around the edges. Then coated all with several coats of carbon. WORKS GREAT. That leading edge is very hard! Quote
mustangermatt Posted June 7, 2004 Posted June 7, 2004 I layed glass on each side and JUST around the edges so they had twice as many layers as the sides. The best way I found to do this was stretch an oversize piece of glass cloth (6 oz in my case) over and around the wetted side and then cut off the extra with a razor knife after it had partially cured. This of course means you can only do about one layer per day. Quote
Scott Dufour Posted June 8, 2004 Author Posted June 8, 2004 I just ordered the graphite powder, and I think I'll go with the rope idea. Pretty cool and sounds like it's within my abilities. I'm also going to pick up the okoume plywood this week. Very exciting stuff... Quote
Klaus Posted June 8, 2004 Posted June 8, 2004 Mention was made above of adding graphide powder to ALL epoxy. I would say it's perhaps better to use just plain epoxy for the first wetting out of the glass cloth. If there was graphite powder mixed in at this early stage it would be very difficult to see if all the glass fibres were thoroughly wetted out. With plain epoxy, the fibres become translucent when fully wetted out and its easy to spot the dry areas where the remained white. Regarding the glassing process, I have always glassed my foils in one go on both sides. For that one needs a little jig that holds the blade between sharpened screw points horizontally to the table top. The jig should place the screw tips high enough above the working surface so that the board can completely rotate on the screw tips. Why screws and not nails? Screws can be fixed through a hole in the jig and adjusted for the right distance, then locked in place with a nut or two. I had first drilled shallow holes on the top and bottom side of the foil for the tips to bite into. These were filled after the board was finished. For the glass cloth I found that either getting a bias weave (the fibres run diagonally) or cutting the cloth on the bias (possible for smaller foils) it will drape much easier and smoother around the foil. I leave the cloth to extend past the trailing edge by at least 1 inch and clip both sides together with plastic cloth pegs to prevent slipping while applying the resin. Letting the epoxy cure with the foil suspended leading edge up allows one to eliminate any runs easily. After curing the glass cloth is trimmed to about 1/16" past the trailing edge, to give a glass filled edge. I never tried that leading edge rope trick, which sounds interesting, but have always had a shaped hardwood stave at that location instead. If one is worried that frequent dragging on the bottom would wear the glass layer through to the wood core and, thence, water can ingress it, try the following: Before any glassing takes place cut off a section from the bottom edge and epoxy it back on. This provides an epoxy layer, stopping any water wicking up past it. The cut is made a little higher on the leading edge, so from a side view it looks like a wedge. Good luck. Graphite powder filled epoxy makes for a very slick surface but at the expense of it being hell (and messy) to sand smooth :wink: Klaus Quote
Scott Dufour Posted June 8, 2004 Author Posted June 8, 2004 I'm thinking of graphite more for its strength than its slickness: I figure I won't know the difference between a 7 and 8 knots anyway. I put the epoxy coated rope on tonight, and I'll do some sanding tomorrow morning. I'm going to fair it all smooth with an epoxy/silica mix, then glass it with a regular epoxy wet-out. I'll fill the weave with epoxy/graphite. Then, since it's strength and not speed I'm looking for, I'll probably paint it. New question then: what primer and paint to use on the graphited epoxy? Anybody got experience painting over that tephlon-like surface? Quote
capt jake Posted June 8, 2004 Posted June 8, 2004 Oh my gosh, Scott you opened a can of Ray worms. New question then: what primer and paint to use on the graphited epoxy? Anybody got experience painting over that tephlon-like surface? Quote
Scott Dufour Posted June 9, 2004 Author Posted June 9, 2004 What 'cha got Ray? Also, Gordy: Did you just pour in the lead shot instead of melting it? Seems safer to work with. About how much weight is did it end up being, and where can a city-born Yankee find some? Do I need to learn to chew tobacco and find my way into a gun club? :wink: Quote
Klaus Posted June 9, 2004 Posted June 9, 2004 What kind of paint? Easy! just use a good quality two pack paint. Anything else is not hard enough for use on a foil and its a waste of paint & effort to put on something like single pack paint - it just rubs off. my 2 cents :wink: Klaus Quote
Gordy Hill Posted June 12, 2004 Posted June 12, 2004 First, I really really wouldn't paint the graphite-epoxy surface. First, there's no need and second, if you wet sand it with really fine grit it looks fantastic. Scott: I bought a box of 12 gage shotgun shells at Walmart with the smallest shot I could find and just cut them open. If you go to a gun shop you can buy a bag of shot. This is a better idea because now I have all those shells with live primers and powder in them. Finally I found a friend who wants them for training his dog. It doesn't really add a lot of weight. but both the centerboard and the rudder blade float much lower and work better with it. A few more smaller holes full of the shot and epoxy might be even better. I was concerned about weakening the board, but I think shouldn't be much of a problem if you use your head. Gordy "No good deed goes unpunished." Quote
Frank Hagan Posted June 12, 2004 Posted June 12, 2004 I bought a box of 12 gage shotgun shells at Walmart with the smallest shot I could find and just cut them open. If you go to a gun shop you can buy a bag of shot. This is a better idea because now I have all those shells with live primers and powder in them. Finally I found a friend who wants them for training his dog. Wow! Tough dog! Quote
Gordy Hill Posted June 12, 2004 Posted June 12, 2004 For the NOISE Frank! He wants the dog to get used to the sound of the gun. .......................................maybe I could have been clearer... Quote
Scott Dufour Posted June 12, 2004 Author Posted June 12, 2004 I was thinking I would paint it because it would look better than the black, then, of course, I realized that nobody ever sees the centerboard :oops: . I'm going to try the lead shot idea too. What weight fiberglass do y'all think I should use? To go back to the painting graphited epoxy thing again: If I glassed the bottom of the whole boat and filled the weave with graphited epoxy - then I'd want to paint it. Crazy idea or good one? I have a 1995 McMaster-Carr catalog I've been ordering parts out of for eight years - with them updating the prices, of course. They really do have just about everything in the universe. Quote
Gordy Hill Posted June 13, 2004 Posted June 13, 2004 Scott, If you're going to paint the bottom there's really no reason to use graphite and the paint might not stick to it very well. Gordy Quote
Frank Hagan Posted June 13, 2004 Posted June 13, 2004 For the NOISE Frank!He wants the dog to get used to the sound of the gun. .......................................maybe I could have been clearer... Yeah, I know. It just struck me as funny at the time. He probably is going to use him as a hunting dog. If he's a duck hunter, he doesn't want the dog to freak out instead of going out and getting the duck that he's bagged. Lead shot makes a lot of sense, because you don't have to try to melt it down and pour it into a mold. Steel shot would not be as good a choice because of rusting. But lead, that traditional keel material, encased in epoxy, it doesn't present any danger to the environment, so its a good all-around solution. I used to be able to get lead that was extruded into a rectangular shape, and small enough in cross-section to be bendable. I'll have to check my source again on that; it would be nice to have a non-floating rudder! Quote
Ken_Potts Posted June 14, 2004 Posted June 14, 2004 You should be able to get 20 lb bags of shot at any store that sells reloading supplies. Around here that includes most gun shops and the occasional Wal-Mart (yes, their stock DOES vary a bit from store to store). Don't worry too much about the shot size, most of it is pretty small. I guess the smalles shot would make the most dense epoxy/lead mix, though. Quote
Scott Dufour Posted June 14, 2004 Author Posted June 14, 2004 And IIRC, the diameter of a group of spheres doesn't affect the density of the whole composition. 20 larger spheres offer the same mass as 200 small ones in equal volumes. There are more spheres and more holes in the little stuff, but the density stays relatively the same. I think. I know that the lead should go as close to the tip as structurally possible, but how about the fore/aft direction? Does it matter, or should I just put it in the middle and call it a day? Gordy, I was reading on the main forum how a couple of people had graphited the bottom of the Weekenders and found them to then be nearly indestructable; dragging over sharp rocks and stuff. Having never really sailed, I thought that might be a good idea - you think that's overkill , though? If so, I go with your advice and just glass and fill the weave as normal. Quote
Gordy Hill Posted June 14, 2004 Posted June 14, 2004 Scott, I would strongly consider graphite ONLY on the bottom. Besides giving a fantastic finish, the color runs clear through the fiberglass. A scratch, therefore, is pretty much invisible. I don't think the graphite makes the fiberglass any tougher. Gordy Quote
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