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#1
posted to rec.boats.cruising
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Round and round we go, or, "sand in your eyes"
On Tue, 24 Apr 2012 11:55:25 -0400, "Flying Pig"
wrote: If you've been paying attention, you know I've dropped my rudder and have been removing prior attempts to epoxy pits in the shaft - done in a convoluted, upside-down manner, inside the boat - which turned out badly. With the rudder out, I have access to it conveniently, to do it up right (well, as best as possible in that it can't be sent off for grinding, rewelding, and machining to round again). I believe I have all the prior epoxy out. Some of the pits have tunnels up or down, too, which, as I worked them out with the pick, displayed remnants of prior packing material. Not so good. The good news is that nearly everywhere I managed to pick off shows very bright under the old epoxy, so it's clean (or will be when I use a brush and acetone to remove all solubles which may be hiding on the surface, and which would impede bonding). The area covered by the packing gland has minimal reduction in diameter - mostly 2-5, and at worst, ~8 thousandths of an inch (out of 2"). However, I'd like not to have even that, if I can avoid it... === Well everyone else has had a shot at this so I'll dip my oar in the water also. Rick is on the right track with his mold approach but I'd do it differently. I'd buy a sheet of heavy duty mylar which is available at any art supply store or sailmaker. Next I'd coat one side of the mylar with wax or mold release. After filling the pits with Devcon/epoxy/Colloidal Silica or whatever, I'd wrap the shaft tightly with the mylar (wax side down of course) and try to squeeze out any excess epoxy as I wrapped. Leave the mylar on until cured by wrapping it with masking tape or some such. If done properly, this will minimize the high spots and the amount of sanding to be done. The sanding should be done with long strips of emery cloth or wet and dry sandpaper, using them like a shoe shine cloth wrapped around the shaft at about 180 degrees. Change the angle frequently to avoid making an oval shape. I have successfully dressed the shafts on anchor windlasses in this way after they've become dinged/distorted. |
#2
posted to rec.boats.cruising
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Round and round we go, or, "sand in your eyes"
On Tue, 24 Apr 2012 21:28:47 -0400, Wayne.B
wrote: Well everyone else has had a shot at this so I'll dip my oar in the water also. Rick is on the right track with his mold approach but I'd do it differently. I'd buy a sheet of heavy duty mylar which is available at any art supply store or sailmaker. Next I'd coat one side of the mylar with wax or mold release. After filling the pits with Devcon/epoxy/Colloidal Silica or whatever, I'd wrap the shaft tightly with the mylar (wax side down of course) and try to squeeze out any excess epoxy as I wrapped. Leave the mylar on until cured by wrapping it with masking tape or some such. If done properly, this will minimize the high spots and the amount of sanding to be done. The sanding should be done with long strips of emery cloth or wet and dry sandpaper, using them like a shoe shine cloth wrapped around the shaft at about 180 degrees. Change the angle frequently to avoid making an oval shape. I have successfully dressed the shafts on anchor windlasses in this way after they've become dinged/distorted. Good thinking, Wayne. May I add a "mod" or two? Your post triggered a memory. Saran wrap makes a great "mold release", actually better than mold wax. It could be wrapped around the shaft first. Heavy duty mylar sounds good, as well as thin metal, aluminum or maybe better stainless. Pre-formed by working around the shaft before the epoxy. How about however many engine piston ring compressors needed to "wrap" the mylar/metal sheeting? You know, those things that squeeze the rings down on a piston so you can slide it into the cylinder? This method will leave a slight ridge where the mylar/metal overlap, but should be a problem. I agree 100% with the "shoe shine cloth" method of finishing. Rick |
#3
posted to rec.boats.cruising
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Round and round we go, or, "sand in your eyes"
On Wed, 25 Apr 2012 06:23:53 -0500, Rick Morel
wrote: Your post triggered a memory. Saran wrap makes a great "mold release", actually better than mold wax. It could be wrapped around the shaft first. === I have used saran wrap and also light weight plastic sheeting. They both "release" well but tend to leave wrinkles in the finish. Heavy mylar sheet like pattern making material will not. |
#4
posted to rec.boats.cruising
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Round and round we go, or, "sand in your eyes"
On Wed, 25 Apr 2012 07:55:17 -0400, Wayne.B
wrote: On Wed, 25 Apr 2012 06:23:53 -0500, Rick Morel wrote: Your post triggered a memory. Saran wrap makes a great "mold release", actually better than mold wax. It could be wrapped around the shaft first. === I have used saran wrap and also light weight plastic sheeting. They both "release" well but tend to leave wrinkles in the finish. Heavy mylar sheet like pattern making material will not. Good point! Rick |
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