Laying up fabric on Bladder

General Composites Discussions Composites Talk
#1

Are there any online sources…here in the archives (I searched) or at manufacturer sites that show bladder molding lay-ups? I’ve toured some facilities and have seen it from a far, but I’d like to study it more closely.

My goal is small hollow parts with a 2-part mold and an inflatable bladder.

I really liked how the poster from last year did that broom stick for broom hockey. His technique made sense since he was using carbon sleeves and a wet lay-up.

I would be using prepreg and differing fabric orientations.

My specific questions are related to

1 - overlapping fabric pieces (how much overlap is generally used, will it move when bladder is inflated)

and

2 - how exactly to lay up the layers. (in the mold? on the bladder? bladder partially inflated? etc. etc. etc.

That’s why I need to see some good step by step instructions, videos, photos.

Thanks,
DY

#2

generally ive seen a .5" requirement from most venders ive delt with as far as overlap goes.

i think it would be tricky to get prepreg to work and get a strong seam at the 2 part mold line.

plus there isnt any pre preg tubing that im aware of.

keep at it youll figiure it out

#3

Would be very interested in knowing about this process in more detail too

#4

I know this is an old thread but I’ll throw out a few ways to handle the situation for future searchers.

  1. You can do the layup on the bladder but eliminating pinholes on the surface is the challenge. Essentially the bladder in inflated inside an correctly undersized sized mold (I make them with plaster), filled with BB’s, and then vacuum is applied. The bladder is now correctly sized and can be firmly handled. The prepreg is applied to the bladder, the mess is stuffed into the production mold and inflated. After cure the beads are poured out and the bladder is removed.

  2. You do the layup into each mold half, insert a packable bladder, join the two mold halves, inflate, and cure. These bladders are typically a one time use. I use a stem to pack the bladder with vacuum to keep the bladder out of the way while sliding the mold halves together. In some applications I slide the bladder in after the mold is closed. After cure the stem is twisted which winds up the bladder for removal. I’ve included some pictures of the layup below. It works best to template cut the prepreg/fabric so no trimming is required. You can use this same process with a wet layup.

#5

Since you brought this up I was wondering… in one of your videos you’re referring to “bog seam” and “tape seam”, could you please explain more, I’m always interested in new techniques. Thanks

#6

A bog is made by trimming or laying the fabric flush with the mold halves and just using thickened resin or bonding adhesive to make the seam. This joint works well with things like wings that allow a greater bonding surface area. Many full scale wings are made with a joggle gasket on the LE and a bog seam at the TE. Smaller wings use a bog seam at the LE and TE.

A tape seam is often used with unassisted wet-layups. Again the farbic is trimmed flush with the mold halves. Usually the tech waits till the resin greens/gels and then slides a razor blade along the flange to trim off the excess. Then glass tape is used to span the joint and roller is used to press it in place. It requires some internal access holes.

#7

Thanks for your reply, so If I understand correct concerning Bog Seam: After cure you cut flush the fabric in both molds top and bottom and you use thickend adhesive on the edge and bolt both molds together. Is this enough if making a tube or the next step is the tape seam?
Also in your video you’re using something like clear tape on the inside edge of the mold

#8

Your understanding of the bog seam is correct. I wouldn’t use it to make a tube. It will be very prone to cracking at the joint. The tape seam would perform much better.

Also in your video you’re using something like clear tape on the inside edge of the mold.

I’m not quite sure what you are referring to. Which video and which portion of the video?

#9

The video is the “Composite Mold & Fabrication” http://vimeo.com/13433861 at 00:47. Is this fiberglass tape? You’re laminating it on the edge and as soon as it dries you bond both halves together??

#10

You are seeing is a resin saturated strip of fiberglass. It’s put into position before the mold is closed. The mold halves are slid together, bolted/clamped shut and then rolled to press the tape into position.

#11

so simple but so efficient!!!I had never thought this way of bonding tubes.Thanks!

#12

It’s definitely one way to do it…although I never do it that way. :smiley:

I prefer to work with template cut fabrics and use the technique that is shown in post #4. This way there is no trimming necessary, no tape to mess with, and the seam is lighter and stronger. You would roll this just like the tape. It is the hardest to do cosmetically though. Add a bladder to the process and you will have the tightest, strongest, and prettiest seams around.

The tape seam is easy to get cosmetically clean though.

#13

I need to master my bladder technique, the problem is that where I am at, I can only find baloons to use as bladder. If there is any online shop which sells latex bladders please share.

#14

Here is a video that I made on how to make your own.

http://vimeo.com/10665397

I now use a 40 watt soldering iron which allows you to go much faster than in the video.

Adam

#15

Thanks, I’ll try it!

#16

If you run into problems just post them here. I’ve ran into most problems that occur with the process. :slight_smile: I’ve had epic failures and successes.

BTW, if your are working with simple tube shapes or don’t mind some wrinkles on the inside you can use poly tubing. You can just seal the end or tie a knot. The wider poly tubing also make speedy envelope bags. Just seal the end with an impulse sealer. No tacky tape required.

Adam

#17

piercan usa google will bring it up.