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cdgatti
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Excuse me again, but it would be good to see how this turned out and to know how your bladder worked. Finally what pressure did you use? did you have pores? Thanks a lot.
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quinn
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Group: Forum Members
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+x+x+x+xBeen doing a little more reading and feeling a bit less confident about the latex bladder. Seems that latex isn't all that resistant to heat and deteriorates pretty quickly. I already have some wax sheets that I ordered a while ago when I was planning on making my own bladder, so I went ahead and ordered some silicone too so I'll also have that option. The thick sausage type party balloons survived 120 deg C with no issues. Ok good to know. It sounds like latex can work well, but maybe not for that many repeated cycles if using a more permanent reusable one. I guess even if I use the latex bike inner tube, it's still only a few bucks for each one. Maybe use it a couple times or even use a new one each time. Not a big deal. Having a hard time finding balloons that are long enough and expand enough at the large end. I ordered some "rocket balloons" on Amazon and they inflate enough to fill the cavity, but they are just about at their limit at the large end and they aren't very durable. Large end is 40mm×46mm. Look for something like these: https://www.ebay.co.uk/itm/Pack-of-10-Qualatex-Latex-Modelling-Balloons-160Q-260Q-350Q-646Q/142279076152?epid=1010298085&hash=item21207e6938:m:mEGch4FK9sgwAfjs6GsXwcg:rk:2:pf:0 Perfect, the 6 inch ones should should fill it nicely without thinning out too much. Was only able to find the standard size ones before. Now I know to search for 646q. Plenty on amazon
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Steve Broad
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Group: Forum Members
Posts: 408,
Visits: 4.1K
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+x+x+xBeen doing a little more reading and feeling a bit less confident about the latex bladder. Seems that latex isn't all that resistant to heat and deteriorates pretty quickly. I already have some wax sheets that I ordered a while ago when I was planning on making my own bladder, so I went ahead and ordered some silicone too so I'll also have that option. The thick sausage type party balloons survived 120 deg C with no issues. Ok good to know. It sounds like latex can work well, but maybe not for that many repeated cycles if using a more permanent reusable one. I guess even if I use the latex bike inner tube, it's still only a few bucks for each one. Maybe use it a couple times or even use a new one each time. Not a big deal. Having a hard time finding balloons that are long enough and expand enough at the large end. I ordered some "rocket balloons" on Amazon and they inflate enough to fill the cavity, but they are just about at their limit at the large end and they aren't very durable. Large end is 40mm×46mm. Look for something like these: https://www.ebay.co.uk/itm/Pack-of-10-Qualatex-Latex-Modelling-Balloons-160Q-260Q-350Q-646Q/142279076152?epid=1010298085&hash=item21207e6938:m:mEGch4FK9sgwAfjs6GsXwcg:rk:2:pf:0
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quinn
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Group: Forum Members
Posts: 155,
Visits: 992
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+x+xBeen doing a little more reading and feeling a bit less confident about the latex bladder. Seems that latex isn't all that resistant to heat and deteriorates pretty quickly. I already have some wax sheets that I ordered a while ago when I was planning on making my own bladder, so I went ahead and ordered some silicone too so I'll also have that option. The thick sausage type party balloons survived 120 deg C with no issues. Ok good to know. It sounds like latex can work well, but maybe not for that many repeated cycles if using a more permanent reusable one. I guess even if I use the latex bike inner tube, it's still only a few bucks for each one. Maybe use it a couple times or even use a new one each time. Not a big deal. Having a hard time finding balloons that are long enough and expand enough at the large end. I ordered some "rocket balloons" on Amazon and they inflate enough to fill the cavity, but they are just about at their limit at the large end and they aren't very durable. Large end is 40mm×46mm.
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Steve Broad
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Group: Forum Members
Posts: 408,
Visits: 4.1K
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+xBeen doing a little more reading and feeling a bit less confident about the latex bladder. Seems that latex isn't all that resistant to heat and deteriorates pretty quickly. I already have some wax sheets that I ordered a while ago when I was planning on making my own bladder, so I went ahead and ordered some silicone too so I'll also have that option. The thick sausage type party balloons survived 120 deg C with no issues.
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quinn
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Group: Forum Members
Posts: 155,
Visits: 992
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Been doing a little more reading and feeling a bit less confident about the latex bladder. Seems that latex isn't all that resistant to heat and deteriorates pretty quickly. I already have some wax sheets that I ordered a while ago when I was planning on making my own bladder, so I went ahead and ordered some silicone too so I'll also have that option.
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quinn
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Group: Forum Members
Posts: 155,
Visits: 992
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Got some stuff in the mail to try for bladders. Some long balloons and a latex bike inner tube. I think the inner tube is gonna work well as a reusable bladder. It will be secured at both ends in the endcaps I'm going to mill. End caps will have a few small channels milled into the mating surface against the mold so air can escape as bladder fills. After thinking about it, it would be very easy to combine both vacuum and pressure with this setup. I can just envelope bag the whole thing with the ends of the bag sealed around the outside edge of the end caps. Really quick and easy to bag it this way. When pulling air out of the bag, air will be pulled out between bladder and mold wall through the milled channels. The bladder should basically inflate itself inside as air is pulled out, then I can add more positive pressure inside the bladder through a fitting in the endcap. Then it really will be just as good as an autoclave. I'll try with and without vacuum to see if there's much difference. If not, the process is a bit quicker without the bagging.
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Steve Broad
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Group: Forum Members
Posts: 408,
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+x+x+x+xIf your item is, say, 24 inches long and 4 inches in circumference, then 100psi is around 5 tonnes of pressure. That's equivalent to over 4 Ford Fiestas!. Talking to my carbon supplier, they suggested that 2BAR (approx 44psi) was more than enough when making a carbon/aramid hockey stick using the bladder process, so 7BAR is a massive overkill! It sounds like a lot, but think about a much larger, much thinner walled aluminum scuba tank holding 3000 psi. My mold is held together with 12 m6 bolts with enough thread depth that the bolt snapping is definitely the failure point. A single m6 bolt can hold 2 tons, so theoretically, if one side of my mold was fixed to something, you could hang about 20 ford fiestas from it before shearing the bolts. Not to say 100psi isn't overkill, but I'm pretty confident it would be well within the safe range. I'll try much lower pressure if you guys think 100psi is far more than what's useful. Also, when applying any pressure at all, I'll test it in a safe place with a long hose and go quite a bit higher than I will when pressurizing near myself just to make sure its safe. I'm sure things also change when heated, so I'll stay away from the oven while cooking and be mindful of what direction aluminum is gonna fly lol. I wasn't saying the bolts wouldn't cope with the pressure, just trying to show how much weight 7 BAR is equivalent to :-) I consider that 3BAR is more than enough and any extra pressure won't make any noticeable difference to the finished product but will add to the risk. However, as I will be nowhere near it's your call :-) Keep us informed as this will be interesting. I'll try 50psi or so. I'm sure there's a point of not much return. The resin ratio is set with prepreg, so as long as there's no voids with lower pressure, going higher isn't gonna make anything better Correct, once the air is removed there is nothing left in the composite that is compressible.
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quinn
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Group: Forum Members
Posts: 155,
Visits: 992
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+x+x+xIf your item is, say, 24 inches long and 4 inches in circumference, then 100psi is around 5 tonnes of pressure. That's equivalent to over 4 Ford Fiestas!. Talking to my carbon supplier, they suggested that 2BAR (approx 44psi) was more than enough when making a carbon/aramid hockey stick using the bladder process, so 7BAR is a massive overkill! It sounds like a lot, but think about a much larger, much thinner walled aluminum scuba tank holding 3000 psi. My mold is held together with 12 m6 bolts with enough thread depth that the bolt snapping is definitely the failure point. A single m6 bolt can hold 2 tons, so theoretically, if one side of my mold was fixed to something, you could hang about 20 ford fiestas from it before shearing the bolts. Not to say 100psi isn't overkill, but I'm pretty confident it would be well within the safe range. I'll try much lower pressure if you guys think 100psi is far more than what's useful. Also, when applying any pressure at all, I'll test it in a safe place with a long hose and go quite a bit higher than I will when pressurizing near myself just to make sure its safe. I'm sure things also change when heated, so I'll stay away from the oven while cooking and be mindful of what direction aluminum is gonna fly lol. I wasn't saying the bolts wouldn't cope with the pressure, just trying to show how much weight 7 BAR is equivalent to :-) I consider that 3BAR is more than enough and any extra pressure won't make any noticeable difference to the finished product but will add to the risk. However, as I will be nowhere near it's your call :-) Keep us informed as this will be interesting. I'll try 50psi or so. I'm sure there's a point of not much return. The resin ratio is set with prepreg, so as long as there's no voids with lower pressure, going higher isn't gonna make anything better
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Steve Broad
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Group: Forum Members
Posts: 408,
Visits: 4.1K
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+x+xIf your item is, say, 24 inches long and 4 inches in circumference, then 100psi is around 5 tonnes of pressure. That's equivalent to over 4 Ford Fiestas!. Talking to my carbon supplier, they suggested that 2BAR (approx 44psi) was more than enough when making a carbon/aramid hockey stick using the bladder process, so 7BAR is a massive overkill! It sounds like a lot, but think about a much larger, much thinner walled aluminum scuba tank holding 3000 psi. My mold is held together with 12 m6 bolts with enough thread depth that the bolt snapping is definitely the failure point. A single m6 bolt can hold 2 tons, so theoretically, if one side of my mold was fixed to something, you could hang about 20 ford fiestas from it before shearing the bolts. Not to say 100psi isn't overkill, but I'm pretty confident it would be well within the safe range. I'll try much lower pressure if you guys think 100psi is far more than what's useful. Also, when applying any pressure at all, I'll test it in a safe place with a long hose and go quite a bit higher than I will when pressurizing near myself just to make sure its safe. I'm sure things also change when heated, so I'll stay away from the oven while cooking and be mindful of what direction aluminum is gonna fly lol. I wasn't saying the bolts wouldn't cope with the pressure, just trying to show how much weight 7 BAR is equivalent to :-) I consider that 3BAR is more than enough and any extra pressure won't make any noticeable difference to the finished product but will add to the risk. However, as I will be nowhere near it's your call :-) Keep us informed as this will be interesting.
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