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Feb 17, 2011, 02:00 PM
Registered User

Seeing the bladder inflate in your mold


I made this mold with a plexiglass half to see what happens as the bag is inflated in a mold. One half was deep and it went to a very shallow end. Not a practical shape to mold, this is for experimenting. I will be able to use the plexi on another mold half if I decide I need to try a different shape. I ran the bladder pressure all the way up to 50 PSI and did not take it any further as I had not tested Gypsum molds past that pressure.
At between 10 and 20 PSI, which is just about where vacuum bagging is equal to the pressure, I got plenty of voids in the corners. You can see as the pressure increases that the voids diminish but do not totally go away. This is an aggressive mold to test the corners. I would not make a mold that has such harsh transitions usually.
The bladder held nicely and there seemed to be no issues with 50 PSI on the Gypsum. I was able to make this whole experiment in a day using gypsum (one selling point of the Ultracal or Hydrocal b11). It gets very hard in a short amount of time so can be layered quickly to make a thick mold. It does not seem to matter that it dries as a thick mass. I would let it set for a couple of days before making a part in it, allowing all the moisture to get out. You can bake it in an oven to accelerate, if you need, I have done that before.

I think the pictures tell a nice story about what you would like to be able to see while looking at your closed mold.

Later,
Dan
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Feb 17, 2011, 02:44 PM
Entropy is happening!
Jim.Thompson's Avatar

Bladder


That is great information Dan! Thanks for posting all the details.
However, I missed any details previously about the construction of your bladders. I have searched back through the thread but can't find it this morning.
Was it you who uses the liquid rubber construction method? If so, what is the brand and supplier please.

Jim.
Feb 17, 2011, 03:51 PM
Registered User
cn0rris's Avatar
Quote:
Originally Posted by miraclesailor
Hope you decide to pursue this.
I'm definitely going to do something. I've started a plug and have been reading a lot about mold making, and learning a lot about inflation bladders from this thread. Your point about making a mold that is compatible with both bagging and inflation bladders is good advice. I can try it the "stock" Bubble Dancer way first, and then do a wet-seamed one to compare the strength and weight.

Chuck
Feb 17, 2011, 04:37 PM
Registered User
Quote:
Originally Posted by Jimbello
That is great information Dan! Thanks for posting all the details.
However, I missed any details previously about the construction of your bladders. I have searched back through the thread but can't find it this morning.
Was it you who uses the liquid rubber construction method? If so, what is the brand and supplier please.

Jim.
Jim:

I have used the wet Latex method for bladder making. It was a long time ago and I only remember getting the latex that the art store had in supply. It is all just latex so I do not see that there would be much of a difference. I made a plaster mold, slightly smaller than the part mold it was going in, that I could pour the latex into. I filled it then poured it out, let it dry and did the same thing again. It was a really thick bladder and barely smaller than the mold I was making it for so it did not have to expand much. Unfortunately it only lasted one time and ripped while taking it out of the part. I still had the mold for the bladder but put the project aside to think about it. I now come back to it 8 years later…time flies.

I am now a big fan of making the bladders from plastic the way Adam teaches in his video: "http://vimeo.com/10665397". I am using 3 mil black and having great luck with it. I have tried using the Stretchalon but have not been able to make a bag from it as my solder iron (25Watt) is too hot and melts the material too fast. I am thinking about buying a 15Watt or trying to regulate the one I have. I think if I can get a good bag from Stretchalon it will be better in the corners.

I mentioned the material in the Video I made on bladder failure:
"http://vimeo.com/19533269". I use a 25Watt soldering Iron pounded flat (hammer/anvil) on the tip to spread the heat for easy sealing. Makes for a consistent seal though it has to be cut with scissors afterward, as there is no cutting with heat action. I use newspaper underneath for a nice bond. Parchment (baking) paper on top and bottom of the seam. I tape the pattern, which is cut out of paper to the plastic and run the iron freehand around the perimeter.

Later,
Dan
Feb 17, 2011, 06:12 PM
Registered User
Dan, it looks like you took your mold off one of those foil covered chocolate Santas....mmmmmm chocolate
Feb 17, 2011, 08:39 PM
Registered User
Quote:
Originally Posted by randyc
Dan, it looks like you took your mold off one of those foil covered chocolate Santas....mmmmmm chocolate
Actually it was a plastic mayonnaise container that I cut on a diagonal . I wanted to find something quick to do the experiment. I was going to make a plug out of clay but saw this and realized it would be perfect if I cut it on the diagonal so I could have a transition from deep to shallow.

Dan
Feb 18, 2011, 12:23 AM
Entropy is happening!
Jim.Thompson's Avatar
Thanks Dan. I also have been doing the heat sealed plastic bladders and having the most success with them. I will be trying the Qualatex balloons again however. I think there is an application for each of them in certain moulds.

Jim.
Feb 18, 2011, 04:29 AM
Registered User
Hello, I am French, I speak very little English, so excuse my language.
I Regad the method since the beginning of Adam, I made bags and I always have one or two air holes, is what it's for your answers normal.Merci
Patrick
Feb 18, 2011, 08:07 AM
Registered User
Quote:
Originally Posted by miraclesailor
Jim:
I have tried using the Stretchalon but have not been able to make a bag from it as my solder iron (25Watt) is too hot and melts the material too fast. I am thinking about buying a 15Watt or trying to regulate the one I have. I think if I can get a good bag from Stretchalon it will be better in the corners.

I mentioned the material in the Video I made on bladder failure:
"http://vimeo.com/19533269". I use a 25Watt soldering Iron pounded flat (hammer/anvil) on the tip to spread the heat for easy sealing. Makes for a consistent seal though it has to be cut with scissors afterward, as there is no cutting with heat action. I use newspaper underneath for a nice bond. Parchment (baking) paper on top and bottom of the seam. I tape the pattern, which is cut out of paper to the plastic and run the iron freehand around the perimeter.

Later,
Dan
To control the heat of your iron use a simple lamp dimmer. Like this http://tiny.cc/5pu8t
The greater mass of a larger iron run at a lower temp gives more consistent heat.
Feb 18, 2011, 10:47 AM
Just fly it!
wyowindworks's Avatar
Thread OP
Quote:
Originally Posted by patrick57
Hello, I am French, I speak very little English, so excuse my language.
I Regad the method since the beginning of Adam, I made bags and I always have one or two air holes, is what it's for your answers normal.Merci
Patrick
Patrick, it's not normal to have holes in the bladder. Is that what you were asking?

Adam
Feb 18, 2011, 04:14 PM
Registered User
Upvector's Avatar

Supra pod bladder joining the halves


Ok.. jumping the gun here before the pics.. Build partner Bob Hammett came up with an idea to join the pod halves... and...
Thanks to Adam's vid, and the terrific info on the forum, we decided to try making a bladder to join the two halves of a supra pod, in the mold.

Surprisingly, the first attempt at making the bag worked well, with only a couple of burn hole glitches that were easily repaired. We are using a 2 mil poly plastic bag, the full length of the bag is about 3 feet, and it was shaped with a particle board template cut to approximate the side view of the supra pod.
The idea is to put the made pod halves back into the mold halves, apply the wet seam joining kevlar and other bits that go into the pod, lay the bladder into one half and close the mold. Then pull the excess bladder material sticking out the back, over the mold, as pictured. Attach the vacuum hose and evacuate.

First trial ( no wet seaming cloth) worked amazingly well, the only difficulty was to convince ourselves that the bag had drawn itself tight against the inside of the pod halves. We could only peer into the rear of the mold with a light to illuminate the front half, but visual clarity was not good. The only indicator was the open pylon hole on top of the pod, where the bladder was touching itself.. it was tight as a banjo head.. I am borrowing a bore-scope from my neighbour to try and see right into the front of the mold ...that should tell us if it is a go for the real attempt. So far it does look promising.

The whole idea with this way, is to make sure that the edge seams of both halves of the pod are cleanly butt joined and the kevlar seam cloth is well pressed onto the inside seams.

We should be attempting a live run on Tuesday, and will try and document the... uhm.. experiment with some pics.
Anyone else tried this..??please chime in

Thanks for looking
Ray
Feb 18, 2011, 05:04 PM
Registered User
stevext's Avatar
Hi

Rather than using a vacuum bag have you tried using a bladder for this as i doubt you'd need much pressure to ensure the kevlar is pressed nicely against the pod sides.

Good luck with your pod's

Stevext
Feb 18, 2011, 06:54 PM
Registered User
Quote:
Originally Posted by Upvector
So far it does look promising.

The whole idea with this way, is to make sure that the edge seams of both halves of the pod are cleanly butt joined and the kevlar seam cloth is well pressed onto the inside seams.

We should be attempting a live run on Tuesday, and will try and document the... uhm.. experiment with some pics.
Anyone else tried this..??please chime in

Thanks for looking

Ray
Nice way to use this thread for an alternative to the mainstream. I applaud you thinking and doing.

For others, This would be a good way to introduce your molds made for vacuum bagging or hand layup to wet seaming. Especially if you have any holes in them. To ask for 15 PSI (maximum vacuum) on a pressure bladder in a mold that has openings is calling for a failure, in my mind. With this method you do not need to worry about bag popping as long as there are no sharp (cutting) corners to contend with.

Dan
Feb 18, 2011, 07:11 PM
Registered User
Ward Hagaman's Avatar
Quote:
Originally Posted by miraclesailor
Nice way to use this thread for an alternative to the mainstream. I applaud you thinking and doing.

For others, This would be a good way to introduce your molds made for vacuum bagging or hand layup to wet seaming. Especially if you have any holes in them. To ask for 15 PSI (maximum vacuum) on a pressure bladder in a mold that has openings is calling for a failure, in my mind. With this method you do not need to worry about bag popping as long as there are no sharp (cutting) corners to contend with.

Dan
I agree....good method for thin molds. As far a molds with a hatch opening, Dc812 and I have used an inner tube for a bladder, and it started bulging out about 1/4" out of the opening at about 15 psi, so we left it at 15. The part came out great.
Feb 19, 2011, 02:04 AM
Registered User
Hello Adam, I still made the bags, there are always small holes in the bag, you can tell me the proper temperature for the soldering iron?.
Thank you Patrick


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