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- Aug 6, 2022
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I got the dumb idea that if Estes can make fins out of polystyrene, I should be able to cut nice, smooth, perfectly flat fins out of Evergreen polystyrene sheet. Easy to fabricate. Don't have to color it, but can if you want.
I have some fins made. Cut from 0.030 sheet for BT-20. I like them, and I liked the process. They are flat and smooth. No paint required. All good.
Now to attach them. I'm trying to stick with a clear adhesive so I can just rely on the color of the BT and fin without any paint required.
The preference for clear appearance led me to set aside JB Weld plastic epoxy because it is opaque and grey. I don't really trust my BSI on the non-porous PS without making a bunch of holes in the root edge to act as rivets. I'm assuming CA, even the thick stuff, will end up being too brittle to survive landings.
I know Estes recommends what in most cases works out to be the red-tube Testors for sticking its PS parts to BTs, but my gut says that will not work well here. Lots of reports of it getting brittle over time and not holding up as well as pure solvent weld to rocket abuse.
I tried E6000. Glued a test fin to a sanded BT scrap piece. Went back and added fillets. Found it to remain flexible when cured, which meant it was more subject to peeling failure. Also, it peeled cleanly right off the edge of the fillet where I hadn't sanded off the glassine. It stuck much better to the PS, but I'd have been happier with a little more solvent melting/welding at the interface.
My next attempt is going to be Duco cement. The last time I saw it was when I was a kid, but the local Ace Hardware has it in stock. I've read that it dries hard. Thinking the solvents should work well on the styrene. Have read that the formulation changed a few years ago, making it stiffer and quicker drying, but that it is possible to thin it with acetone and make it act like the old formulation, which I may try in order to get a little more soak into the sanded BT and solvent welding at the interface with the PS.
Anyone else have any bright ideas?
I have some fins made. Cut from 0.030 sheet for BT-20. I like them, and I liked the process. They are flat and smooth. No paint required. All good.
Now to attach them. I'm trying to stick with a clear adhesive so I can just rely on the color of the BT and fin without any paint required.
The preference for clear appearance led me to set aside JB Weld plastic epoxy because it is opaque and grey. I don't really trust my BSI on the non-porous PS without making a bunch of holes in the root edge to act as rivets. I'm assuming CA, even the thick stuff, will end up being too brittle to survive landings.
I know Estes recommends what in most cases works out to be the red-tube Testors for sticking its PS parts to BTs, but my gut says that will not work well here. Lots of reports of it getting brittle over time and not holding up as well as pure solvent weld to rocket abuse.
I tried E6000. Glued a test fin to a sanded BT scrap piece. Went back and added fillets. Found it to remain flexible when cured, which meant it was more subject to peeling failure. Also, it peeled cleanly right off the edge of the fillet where I hadn't sanded off the glassine. It stuck much better to the PS, but I'd have been happier with a little more solvent melting/welding at the interface.
My next attempt is going to be Duco cement. The last time I saw it was when I was a kid, but the local Ace Hardware has it in stock. I've read that it dries hard. Thinking the solvents should work well on the styrene. Have read that the formulation changed a few years ago, making it stiffer and quicker drying, but that it is possible to thin it with acetone and make it act like the old formulation, which I may try in order to get a little more soak into the sanded BT and solvent welding at the interface with the PS.
Anyone else have any bright ideas?
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