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#11
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Bending Plexiglass
On Mar 25, 5:14*am, wrote:
As mentioned in my previous post, the heavy duty, double sided trim tape works quite well. *It is available at most auto parts stores. *I am sorry I can't remember the exact number. *Most of what you find is made by 3M. *There are different grades and you want the one that is used for holding moldings to the outside of the car. *Should say heavy duty or Very High Bond, etc. *It is usually gray foam about .060" thick, but sometimes is black. *(3M does make a VHB tape that has white foam and is strong, but needs a special primer and is not as easy to work with - not to mention, it is more expensive) * All of the heavy duty stuff I have seen has a reddish-orange (or, orangish-red?) backing tape. Clean the canopy frame well. *The tape will conform pretty well, but if there are any sharper bumps, you might want to sand them down a little. *Stick the tape down and rub it on really well. *I have a hard rubber wheel that I screwed onto a scrap of wood for a handle and roll it. *Pressure is key to getting a good bond. *Peel back a little of the protective film from around the edge of the glass and lightly scuff the glass with fine Scotch-brite in the area where it bonds. *If possible, try to leave the rest of the protective film on until you are finished. *I have seen some Lexan with a paper covering, which you might want to peel back a little around the edge so you can see how you are doing when you stick the glass to the tape. *You should be able to just blow the dust off, but if you feel the need to clean it, just use soap and water. *Different manufacturers claim different resistance to various solvents like alcohol. *There are too many different formulations, so in the absence of actual information from the manufacturer, I would avoid using any hydrocarbon solvents. *(An earlier post mentioned using alcohol to clean acrylic, which is usually a bad idea as it will craze and crack many acrylics. *Some are resistant to ethyl alcohol, but most of the alcohol used for cleaning (denatured alcohol) has some methanol in it which is really bad for acrylic.) When you are ready to stick the glass to the frame, test fit it and make some index marks - I make a mark on a couple of the pieces of masking tape that I use to hold it while fitting it. *Then just cut that piece of tape rather than peeling it off. *You have to be pretty accurate. *Peel a short piece of the backing away from the tape in a few key places. *It is a good idea to start in the middle of the bend and work out from there, but you also need a few spots to stick initially all around the perimeter. *Lightly put the glass in place. As long as you don't press it much, you can reposition it. *Once it is in place, you can start pulling the tape backing out from under the glass and sticking it down. A couple of cautions: If this is for a removable canopy, do this on the glider as you can distort the shape a lot. *Don't start in one corner and work your way around as you will wind up putting a twist in the frame and glass. *Work, more or less, from the middle of each side toward the corners. *Do a few inches in each direction, and then go do the same on the opposite side. *It is kind of like torqueing down a cylinder head. Once you have it all stuck down, go around with a roller (or you can just use you finger and press as hard as you can) to really stick it. The acrylic adhesive on the tape is supposed to be very resistant to UV - and even get stronger with continued exposure - so you can just leave it like that, or you can put a strip of tape of whatever color you prefer around it. *It might look nicer that way too. If you have any more questions, feel free to email me. Doug On Mar 25, 5:00*am, Tony Condon wrote: Alright well I bought a sheet of polycarbonate (Lexan) tonight and got it cut to fit the canopy. *Next trick is to get it glued in place. *The canopy frame is a steel tube wrapped in fabric and coated with something that turns it brown. *the fabric is still for the most part intact, a few bits here and there were sacrificed during plexiglass removal. *Any recommendations on glue? -Tony Condon Cherokee II N373Y- Hide quoted text - - Show quoted text - Old conservative mechanical guy speakin' now. To be safe, I would add a row of screws or rivets, at least along the sides, to handle most of the peeling force that will remain after installation. If the plastic were to be formed, this would not be an issue. Most simple way would be Pop rivets with holes in plastic slightly bigger than rivet body. About 4 inch spacing would be fine. If you put one in the center of the top, forward and aft, this would give you a good way to position and index the plastic on installation. Rivets on your canopy frame might be a bit ugly, but not as ugly as blown off canopy and doing it again. Good Luck UH |
#12
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Bending Plexiglass
wrote in message ... On Mar 25, 5:14 am, wrote: Old conservative mechanical guy speakin' now. To be safe, I would add a row of screws or rivets, at least along the sides, to handle most of the peeling force that will remain after installation. If the plastic were to be formed, this would not be an issue. Most simple way would be Pop rivets with holes in plastic slightly bigger than rivet body. About 4 inch spacing would be fine. If you put one in the center of the top, forward and aft, this would give you a good way to position and index the plastic on installation. Rivets on your canopy frame might be a bit ugly, but not as ugly as blown off canopy and doing it again. Good Luck UH Another old conservative mech guy: I would not recommend using pop-rivets of any type on acrylic plastic (Plexiglas). You may get away with it on polycarbonate (Lexan) or other mechanically strong plastics, but it may crack Plexi. Even if you over-drill the holes to help prevent cracking, the pop-rivet itself is set by drawing in a metal bead at the end of the mandrel to expand the rivet. This will apply pressure to the Plexi and may well cause stress cracking. Note that you might get away with it if the "factory head" (the original rivet head) is on the Plexi side and the "shop head" (the part that expands) is on the poly side - - still, I wouldn't risk it. Safer to drill (using plastic drill bits or drill bits ground to reduce relief angle - again, to help prevent cracking the plastic) and then tap the plastic for small machine screws (just like Mecaplex does). bumper maker of the world famous QV and MKIII zz Minden, NV bumper |
#13
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Bending Plexiglass
On Mar 25, 2:09*pm, "bumper" wrote:
wrote in message ... On Mar 25, 5:14 am, wrote: Old conservative mechanical guy speakin' now. To be safe, I would add a row of screws or rivets, at least along the sides, to handle most of the peeling force that will remain after installation. If the plastic were to be formed, this would not be an issue. Most simple way would be Pop rivets with holes in plastic slightly bigger than rivet body. About 4 inch spacing would be fine. If you put one in the center of the top, forward and aft, this would give you a good way to position and index the plastic on installation. Rivets on your canopy frame might be a bit ugly, but not as ugly as blown off canopy and doing it again. Good Luck UH Another old conservative mech guy: I would not recommend using pop-rivets of any type on acrylic plastic (Plexiglas). You may get away with it on polycarbonate (Lexan) or other mechanically strong plastics, but it may crack Plexi. Even if you over-drill the holes to help prevent cracking, the pop-rivet itself is set by drawing in a metal bead at the end of the mandrel to expand the rivet. This will apply pressure to the Plexi and may well cause stress cracking. Note that you might get away with it if the "factory head" (the original rivet head) is on the Plexi side and the "shop head" (the part that expands) is on the poly side - - still, I wouldn't risk it. Safer to drill (using plastic drill bits or drill bits ground to reduce relief angle - again, to help prevent cracking the plastic) and then tap the plastic for small machine screws (just like Mecaplex does). bumper maker of the world famous QV and MKIII zz Minden, NV bumper I agree. I was assuming he would be using polycarbonate and did suggest oversize holes. UH |
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