Hy guys. 
I work on a project that requires wraping wooden tapered ellipsoid object in 2 layers of carbon fiber. Carbon is added for stiffness and visual appearence so nice layup is must.

Carbon goes from bottom of part and goes on sides, it doesnt go all the way around.

I have to use wet layup method combined with vacuum so my plan is to:
1. Cover wood with black tinted epoxy
2. Wait for tacky stage and add first layer
3. Add resin to saturate fabric
4. Wait for tacky stage to add other layer
5. Add resin to saturate fabric
6. Place peel ply and breather and use around 20% vacuum to remove excess resin

My questions are:
1. Will 20% vacuum remove excess resin since most of resin reached tacky or beyond tacky stage?
2. Is there anything to change in the process to ensure good bond and appearance?
3. Process is like skinning with carbon only using 2 layers instead of one and using vacuum to remove excess resin. Should I do like plan above or should I do 1 layer, wait it to cure, key whole surface and repeat process for 2nd layer?

Thanks

Why not with vacuum?

I planned using peel ply an breather anyway. Shape is not just plain ellipse, it has some grooves on body.

Also, with straight wet layup there would be too much extra resin

I agree with Fasta on the doing both in one shot and not letting it gel between plies.  You should be able to get a tight-enough part with less than full vacuum - but it would be easier to use perforated film and a bit more vacuum especially if you have groove features that might need more pressing.  

If you need to vacuum (it will be more compact and will reduce the likelihood of bubbles which will make your finishing hard - especially with grooves) it is good to make sure that all the wrinkles or pleats of the bag are in the off-the carbon bottom or back part.  You want to be able to pull the bag tight so wrinkles in the bag don't print into the part - but not so tight that it bridges the grooves.  Peel ply cut on the bias can help avoid wrinkles too - as will a thinner breather/bleeder like bias-cut light fiberglass cloth.  Going over the bag after its pulled down and pressing the bag into the grooves very evenly will help.  Without a picture or sketch it's hard to know precisely what the shape it - so this is guessing.

It's probably going to be necessary to use some clear primer or high build coat of epoxy to finish before you apply a final coat of UV blocking topcoat. 

The downside of using thin peel ply and wrapping it is that unless you have nicely sliced peel ply it will leave a mess on the edges that will make finishing harder.  Also - the grooves will bridge.  A long drape of bias-cut nylon peel ply over the leading edge and carefully pressed into the laminate - a dry chip brush is great for this - just start at the "nose" and work down.  You didn't mention the orientation of the carbon +/-45 to the tube will conform most easily but 0/90 will look way better if it's twill.

Good luck - and please follow up with pictures if you can!

We get asked the same a lot for cosmetic skinning.  I would say use vacuum only as a last resort and the minimum level of vacuum necessary to hold the fabric in place.  As mentioned, its too easy to distort and crease the fabric ruining everything in the process. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Thanks for your replies. I plan on using 15 to 20% of vacuum, no more than that. 

I will post pictures of object that needs wraping soon so it might be easier to give some advice.

https://ibb.co/g6ht9Mk
https://ibb.co/Rz0MSx6
https://ibb.co/g7Mh6D1
https://ibb.co/QYbt5wq
https://ibb.co/rv45znP
https://ibb.co/ZHm8BJp

There you go guys. Object is actually speargun body and bottom part is that where 2 holes can be seen. Not entire body needs to be wraped, only bottom and sides where most hits and scratches will occur from rocks.

Any extra resin is problem because it will affect buoyancy and thats the main reason why I consider vacuuming it. Also there are some slight curves that might be better done using vacuum.

If this was one layer skinning I think it could be done as regular wet layup skinning, but it needs to be visually nice and with as less as possible extra weight with 2 layers. I am afraid that if I go with layup without vacuum, fabric might float on resin and it will create mess that will be very hard to sand without destroying wooden part.

Extra resin will affect the buoyancy very little, as it has almost the same density as water.

I honestly feel vacuum will make a big mess of this. You'll get resin going all over the place, you won't be able to do it without atleast some pleats in the bag on the surface of the carbon, which will affect the appearance, and it still won't really help THAT much with getting the carbon into those grooves. Atleast not enough to make it worth the trouble of doing.

I would do it wet, without vacuum. At the most possibly a shrink tape, but this will cause the carbon to bridge the grooves, and you may have trouble on the top of the gun where you don't want the carbon to go, the tape may shrink too much and snap there.

Those holes will be cut out afterwards so no need for carbon to go in there. 

Can someone explain in detail how would vacuum ruin it if using peel ply and breather just for the sake of expanding my knowledge?