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Old 10-14-2015, 06:48 AM   #11
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Making a plug makes good sense, one of the complexities of this part is that both halves are layed up together, when cured the bladder must be removed, which would make removing a plug impossible. It has been fairly difficult to remove the bladder without harming it, I fused a "rip cord" to the nose of the bladder so it can be pulled from the inside out when the part is cured, this method and vacuum seems to be fairly consistent in getting the bladder out in one piece.

I greatly increased the clamping force and bolt locations, I was able to apply far more pressure on the bladder than ever before, and the parting line is mich more consistent and much thinner, all good. I also attempted to place the entire mold in a vacuum for 15 minutes after layup, while applying 30 psi to the bladder. I will post pics of the part once it is removed. I appreciate all the input!

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Old 10-14-2015, 07:56 AM   #12
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just as a note, stretchlon isn't really self releasing which could explain some of your problems with removing your blader
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Old 10-14-2015, 05:40 PM   #13
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Have you tried applying vacuum to the bladder to help remove it? This way it will collapse, and should make it easier to remove
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Old 10-15-2015, 09:34 AM   #14
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Quote:
Originally Posted by hojo View Post
Have you tried applying vacuum to the bladder to help remove it? This way it will collapse, and should make it easier to remove
Yes, that is currently how I remove the bladder, the cord also gives a way to help remove it by pulling it from the inside, which effectively flips the bag inside out when removed. I performed a few more runs to see where the issues are, here are some pics. There are a few problem areas that are consistently in the same location, indicating that the bladder is either not shaped correctly, or does not have enough pressure to push excess resin out of these areas. It is entirely possible that the resin is getting trapped in these areas and needs a way to evacuate. The red carbon stock was bagged for 10 minutes to evac air from the mold, then the bladder was inflated to 25 psi. The black carbon stock was placed under continuous vacuum and the bladder was allowed to inflate under vacuum, so approximately 14 psi from what I understand. Maybe a combination of vacuum for the entire cure cycle and applying additional pressure on the bladder will improve these areas?





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Old 10-15-2015, 06:56 PM   #15
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Have you considered making a silicone bladder? It seems that your current bladder (I believe its strechlon bag) is not inflating and applying pressure where you need it, the tight corners. Making a silicone one would have a near net shape of the ID and once pressure is increased should get all the tough corners that youre having issues with.
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Old 10-16-2015, 06:35 AM   #16
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Quote:
Originally Posted by hojo View Post
Have you considered making a silicone bladder? It seems that your current bladder (I believe its strechlon bag) is not inflating and applying pressure where you need it, the tight corners. Making a silicone one would have a near net shape of the ID and once pressure is increased should get all the tough corners that youre having issues with.
Hojo,
Are you using silicone bladders or reusable bags? We are using silicone for reusable bags and they don't seem to hold up as well as "promised". I've been spending a ridiculous amount of money replacing bags on an almost daily basis. We are an industrial/production type operation and, unfortunately for me, my predecessor got us going down this path and I'm trying to find a way out while still maintaining volume.

I'd like to get back to LRTM but have some hurdles (product design changes, etc) to clear on that end. For now, I'm stuck with silicone so I'm looking for any suggestions that will help. Got any tips on prolonging the bag life? We're using a platinum cure bag with a polyester resin.

I know this is a slight derail but it may help the OP if he goes silicone.
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Old 10-16-2015, 07:20 AM   #17
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Quote:
Originally Posted by hojo View Post
Have you considered making a silicone bladder? It seems that your current bladder (I believe its strechlon bag) is not inflating and applying pressure where you need it, the tight corners. Making a silicone one would have a near net shape of the ID and once pressure is increased should get all the tough corners that youre having issues with.
I have considered it, and I think it is the next logical step. Since the issue is repeatable in the same locations, it is safe to say that the current bladder is not doing the job. The bladder isn't 100% "anatomically correct", and needs to be stretched to get into these tight problem areas, where a bladder that is formed or cast to the shape of the mold would work much better. Furthermore, there seems to be a build up of trapped resin in these areas, which compounds the problem, pressure and more direct contact of the bladder will hopefully solve it.

Any recommendations for materials for a silicone bladder? Should I make a cast of the inside of the shell, or do you need to account for the thickness of the material?

Last edited by Compositeman; 10-16-2015 at 08:46 AM.
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Old 10-16-2015, 08:56 AM   #18
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There are some paintable latex rubbers that could potentially be built up in thickness. It would need some testing to see how much pressure they can withstand with certain thickness.

Also, since you wet lay the part there might well be these resin rich areas and if they stay like that with no escape path for the excess resin then the outcome likely won't improve in these areas.

OOA prepregs might seem like a less headache prone way to go?
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Old 10-16-2015, 10:17 AM   #19
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sorry ,but i highly doubt a silicone bladder is going to solve the problem , you have a trapped zone. For one, you need to work the carbon more to get it into the corners better, that is quite a big void.

i would highly recommend trying an intensifier before you change bladder setups. use a solid intensifier just to try it out . make up a mix of cotton flox and micro balloons , and stick it in a small plastic bag. push this bag into the area that is causing the problems and allow to cure. use this intensifier to force the carbon into the corner , the bag will press against it and i can assure you will have a much better part

you havnt mentioned how you making your bladder ? do you apply wax to the bladder before use ? i find that not only does it allow for easier removal , but i also allows the bladder to slip into position.
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Old 10-16-2015, 05:32 PM   #20
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The intensifiers are a great idea. I made a few using body filler, just to try, I'll bag them and wax the intensifiers and the bladder. I also put a few resin flow channels in these areas to help evac the excess resin and trapped air. The bladders seem to be coming out in one piece, using the vacuum and pull string method. Hopefully there won't be any issues with the intensifiers getting stuck in the mold. Results will follow!

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