Planning on trying to do wet layup and then vacuum bagging - thoughts, suggestions?

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#1

I have been having trouble with infusion and getting perfect parts and am waiting on some materials to arrive before I try it again. I thought tomorrow I would try to do a wet layup and then vacuum bag. I believe I have most of the materials but wanted to make sure I have the process right. Any input would be great!

This is how I believe it works, please correct me if needed. Any advise is greatly appreciated!

Step 1: Prepare mold with release agent
Step 2: Wet out a layer of carbon fiber
Step 3: Lay carbon in mold and and press to ensure no air bubbles
Step 4: Apply additional layers of carbon and wet out
Step 5: Apply layer of peel ply
Step 6: Apply layer of perforated release film (I don’t have any, what can I use?)
Step 7: Apply 1-2 layers of bleeder/breather material
Step 8: Apply layer of release film (vacuum bagging material)
Step 9: Apply layer of bleeder/breather material
Step 10: Seal mold with vacuum bagging tape and film, pull vacuum
Step 11: Leave vacuum on while curing.

So I believe I have a good idea of what is needed. My big question is what can I use for perforated release film? Could I just poke small holes in some bagging film?

Also, is there a big difference in part finish quality (how nice the surface looks) with just vacuum bagging like this or infusing?

Thanks for the help!

#2

A few thoughts:

  1. I wouldn’t pre-wet the first layer of carbon. You will actually get more pinholes on the surface with pre-wetting. It’s better to liberally paint the mold surface with resin and then lay dry fabric into it. Take a wet brush and work the fabric into the position. You should have excess resin flow up through this first layer. Add more resin if necessary. Skimping on resin on this first layer will cause you problems. Then lay your next dry layer on top of it. This layer will soak up the excess resin from the first layer. Add more resin to anything that is too dry and progress with the next layer. Prewetting won’t give you a higher Vf…just more air bubbles within the laminate.

  2. I don’t use the second layer of perf-ply that you list in Step 9.

  3. Getting hand layups with pinhole free surfaces is a practiced art form. You cannot count on the vacuum bagging process to remove them. The key is to make sure that there are not voids in the laminate before the vacuum is applied. Infact, vacuum bagging can make some problems worse from a cosmetic stand point.

  4. Infusion done properly will give you a more consistent void free finish than a vacuum assisted hand layup. It easier to master infusion than it is wet hand layups.

  5. You can make some perf-ply by rolling some drop cloth plastic with awoodpecker Perforation tool.

  6. Use a resin with a long pot life. If your resin starts to kick before you get the vacuum applied then the compaction of the fibers will be reduced.

#3

If you are vacuum bagging you should look into getting an aluminum roller. If you roll the composite first before bagging you’ll get more air out.

#4

Thanks guys! Maybe Ill hold off and continue to try and master infusion. That is what I really want to do, I just thought a wet layup might be a good option since I am having trouble.

#5

dp, another view

Lay up your carbon on a piece of polythene taped and stretched flat on your work top put the first layer down with the polythene face dry and wet out the back (start in the center work to out to the edges) then the next layer on top wet out the back consolodate with a roller. untaped the edges of the polythene and lift the whole lot off the bench turn it upside down and transfer into the mould the polythene will help hold the weave in position while you ease it into position.

Gently peel off the polythene and use a small consolidator roller or 1 or 2" brush with the hairs cut shorter so they are stiff to push into the mould.

step 4 Peel ply be carefull here dont let the same piece of peel ply stretch across the mould so it covers two inside radiuses at a time as this can cause bridging.

Step 6: Apply layer of perforated release film (I don’t have any, what can I use?)

Try perforated bread wrap, test a piece with your epoxy first

Step 7: Apply 1-2 layers of bleeder/breather material

1 should be plenty be careful to push well into corners

leave out steps 8 and 9

Make you bag bigger than you need and put pleates in to allow it into the courners.

I also agree that “Infusion done properly will give you a more consistent void free finish than a vacuum assisted hand layup. It easier to master infusion than it is wet hand layups”

Happy New Year

#6

How do you excate the air that gets trapped between the mold surface and the multiple layers of wet carbon? I’ve never been able get this technique to give consistent results with respect to the surface finish. What tips do you have?

#7

Wyowindworks I agree it’s very hard to get right and get consistent results. The air between the layers should mostly be removed by consolidating prior to lifting off the bench. When laying in the mould I treat it like I am applying a self-adhesive film or sticker decal start in the centre and work out to the edges don’t just flop it in, you can also use a squeegee to ease trapped air out or large bubbles can be pricked with a craft knife. Very thin polythene works best like they use for spray paint masking on easy shapes and small stacks. In some ways it is no different from using prepreg which can also trap air between layers if care is not taken. Use a fine mesh netting like flow media or garden netting to ensure an even distribution of vacuum on top of the release film it makes a big difference.

Infusion is a much the better method for a production part. For one offs when done with care it can work (some times).

About two weeks ago I needed to make a small short piece of carbon tube with a clear weave finish on show on the inside face with a wall thickness of 3mm. I used the same method to form the tube. Carbon was layed up around a glass jar which happened to be the right diameter peeling off the polythene film and (able to add tension without distorting the twill weave) as I wrapped it around. I did not use a vacuum but it was interesting to shine a light inside the jar and see a few bubbles trapped and how as I did some consolidating on the outside it moved the trapped air about on the inside face simply giving it a good old roll did not help one bit you had to work methodically from the centre out. I then put the jar on a metal plate on top of a oil filled radiator filled the jar with hot water and let it cure at 80 degree C on the heater for five hours it came out much better than expected with a perfect shiny finish .

Wyowindworks by the way I found your website and bladder moulding technique quiet interesting and have a few questions but will save them for another time.