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quinn
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Group: Forum Members
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+x+x+x+x+xSounds like maybe you should just commit to the quality split female alloy moulds and make a start. The moulds can be used with a number of different techniques so you change your mind or try other things with the same moulds. Your going to have to just get into it and learn along the way, that's how it goes. Maybe just make the moulds a little over length at the ends to allow for some excess part or fitting in bladder ends etc. Positive pressure for internal bladders from bag material or other, inner tubes? Expanding core like expancell Expanding silicone core Internal bag with external bag and vacuum. Others? yeah thats true, no matter what im gonna need some nice female molds so i guess start there and experiment. maybe even start with fiberglass while experimenting to keep cost down. Exactly, it's more about refining the process. Heated moulds will work great but you may as well build a small oven as then you have a more versatile setup for making other parts too. added an edit to my post, not sure if you saw it, "so if doing this with vacuum, i assume you just have to push the bag through the length with a long stick or something, then the remainder of it gets doubled back over the outside of the mold? so what i really need is a long tubular bag big enough for the mold to fit inside, and a little more than double the length of the mold?" Exactly, or you can lay the bag inside as you close the moulds. This can work fine (with practice and the right pre pregs and cure ramping etc) but will only make about 14 psi pressure whereas the bladder or expanding core techniques can make 90 psi so far more pressure can often mean better part finish with less air bubble issues. ah, makes sense. basically atmospheric pressure with full vacuum. unless you then placed it all in a larger tank and pressurized it, but that sounds complicated. oh, read your edit, im basically thinking autoclave heres something i tried yesterday just for fun. pretty much a 200mm long version of my boom. i glued up a few layers of mdf, machined the negative into it plus a 2mm offset, built the 2mm back up with bondo, machined the finished negative shape into the bondo, sand and clear coat. made some pretty decent molds relatively quick for only a few bucks. definitely wouldnt work for prepreg though and im sure aluminum molds are MUCH nicer, but i might consider this method for some larger stuff that i need like the canopy 
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Fasta
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Group: Forum Members
Posts: 468,
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+x+x+x+xSounds like maybe you should just commit to the quality split female alloy moulds and make a start. The moulds can be used with a number of different techniques so you change your mind or try other things with the same moulds. Your going to have to just get into it and learn along the way, that's how it goes. Maybe just make the moulds a little over length at the ends to allow for some excess part or fitting in bladder ends etc. Positive pressure for internal bladders from bag material or other, inner tubes? Expanding core like expancell Expanding silicone core Internal bag with external bag and vacuum. Others? yeah thats true, no matter what im gonna need some nice female molds so i guess start there and experiment. maybe even start with fiberglass while experimenting to keep cost down. Exactly, it's more about refining the process. Heated moulds will work great but you may as well build a small oven as then you have a more versatile setup for making other parts too. added an edit to my post, not sure if you saw it, "so if doing this with vacuum, i assume you just have to push the bag through the length with a long stick or something, then the remainder of it gets doubled back over the outside of the mold? so what i really need is a long tubular bag big enough for the mold to fit inside, and a little more than double the length of the mold?" Exactly, or you can lay the bag inside as you close the moulds. This can work fine (with practice and the right pre pregs and cure ramping etc) but will only make about 14 psi pressure using a regular oven whereas the bladder or expanding core techniques can make 90 psi so far more pressure can often mean better part finish with less air bubble issues. If you had an autoclave then you can get the higher pressures using the inside/outside bag technique but autoclaves are very expensive.
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quinn
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Group: Forum Members
Posts: 155,
Visits: 992
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+x+x+xSounds like maybe you should just commit to the quality split female alloy moulds and make a start. The moulds can be used with a number of different techniques so you change your mind or try other things with the same moulds. Your going to have to just get into it and learn along the way, that's how it goes. Maybe just make the moulds a little over length at the ends to allow for some excess part or fitting in bladder ends etc. Positive pressure for internal bladders from bag material or other, inner tubes? Expanding core like expancell Expanding silicone core Internal bag with external bag and vacuum. Others? yeah thats true, no matter what im gonna need some nice female molds so i guess start there and experiment. maybe even start with fiberglass while experimenting to keep cost down. Exactly, it's more about refining the process. Heated moulds will work great but you may as well build a small oven as then you have a more versatile setup for making other parts too. added an edit to my post, not sure if you saw it, "so if doing this with vacuum, i assume you just have to push the bag through the length with a long stick or something, then the remainder of it gets doubled back over the outside of the mold? so what i really need is a long tubular bag big enough for the mold to fit inside, and a little more than double the length of the mold?"
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Fasta
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Group: Forum Members
Posts: 468,
Visits: 3.5K
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+x+xSounds like maybe you should just commit to the quality split female alloy moulds and make a start. The moulds can be used with a number of different techniques so you change your mind or try other things with the same moulds. Your going to have to just get into it and learn along the way, that's how it goes. Maybe just make the moulds a little over length at the ends to allow for some excess part or fitting in bladder ends etc. Positive pressure for internal bladders from bag material or other, inner tubes? Expanding core like expancell Expanding silicone core Internal bag with external bag and vacuum. Others? yeah thats true, no matter what im gonna need some nice female molds so i guess start there and experiment. maybe even start with fiberglass while experimenting to keep cost down. Exactly, it's more about refining the process. Heated moulds will work great but you may as well build a small oven as then you have a more versatile setup for making other parts too.
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quinn
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Group: Forum Members
Posts: 155,
Visits: 992
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+xSounds like maybe you should just commit to the quality split female alloy moulds and make a start. The moulds can be used with a number of different techniques so you change your mind or try other things with the same moulds. Your going to have to just get into it and learn along the way, that's how it goes. Maybe just make the moulds a little over length at the ends to allow for some excess part or fitting in bladder ends etc. Positive pressure for internal bladders from bag material or other, inner tubes? Expanding core like expancell Expanding silicone core Internal bag with external bag and vacuum. Others? yeah thats true, no matter what im gonna need some nice female molds so i guess start there and experiment. maybe even start with fiberglass while experimenting to keep cost down. so if doing this with vacuum, i assume you just have to push the bag through the length with a long stick or something, then the remainder of it gets doubled back over the outside of the mold? so what i really need is a long tubular bag big enough for the mold to fit inside, and a little more than double the length of the mold?
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Fasta
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Group: Forum Members
Posts: 468,
Visits: 3.5K
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Sounds like maybe you should just commit to the quality split female alloy moulds and make a start. The moulds can be used with a number of different techniques so you can change your mind or try other things with the same moulds. Your going to have to just get into it and learn along the way, that's how it goes. Maybe just make the moulds a little over length at the ends to allow for some excess part or fitting in bladder ends etc. Positive pressure for internal bladders from bag material or other, inner tubes? Expanding core like expancell Expanding silicone core Internal bag with external bag and vacuum. Others?
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quinn
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Group: Forum Members
Posts: 155,
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+xMost research I've read so far comes to the conclusion, that uv resistance has a very low to zero effect at the mechanical propertys of crp. The fibres itself got very strong uv resistant molecular bonds and protect the deeper layers of the resin from degradation. So the major problem is the yellowing of the outer resin. An aesthetic problem. Aesthetics is definitely a concern. Doesn't need to look great as a prototype, but i need to develope a process that will eventually be capable of making a really nice looking part once prototyping is done. Is this sort of thing ever done with both a male and female mold with calculated wall thickness between? With a tapered part like this, I could imagine that making a very efficient part. Layup is done on the male (could be sleeve) then is drawn into the female mold with with some kind of draw bolt mechanism to really put some intense pressure on the walls. Obviously that would only work with a tapered part, but that's what I have. Right now prepreg with seams sounds like the most realistic option and I just need to figure out the heating, but I want to explore any other options that could potentially make a better part
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oekmont
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Group: Forum Members
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Most research I've read so far comes to the conclusion, that uv resistance has a very low to zero effect at the mechanical propertys of crp. The fibres itself got very strong uv resistant molecular bonds and protect the deeper layers of the resin from degradation. So the major problem is the yellowing of the outer resin. An aesthetic problem.
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Fasta
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Group: Forum Members
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+xIt's easy: you don't. But all regular roll wrapped tubes are made that way. With a bit practice and the right materials you can get a finish like commercial tubes, wich for most people will be good enough. Do you have to finish it at all? The spiral tape finish is often quite acceptable to look at although it would have poor UV resistance if left in the sun. Since you are still developing/prototyping don't worry about it.
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oekmont
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Group: Forum Members
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It's easy: you don't.
But all regular roll wrapped tubes are made that way. With a bit practice and the right materials you can get a finish like commercial tubes, wich for most people will be good enough.
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