First Go - FAIL - ! Pics... Have Questions

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#1

Hello all~!

As you are about to see - I am very new to making carbon fiber parts. I have a sailboat that I need to make some fairly large pieces for and right now just can’t get out of the gate! One issue after the other and I’m sure it is all on me.

I’ve vacuumed bagged multiple pieces and they all come out the same, xxxxty. The carbon fiber doesn’t form to the mold very well and carbon itself is very dry - like the resign was sucked out of it.

What I did in this latest fiasco was:
Mold release
Mixed the epoxy and put a thin layer - let it sit for 20 minutes (using 207 hardener)
Laid the first 200g carbon fiber cloth on - put a lot of epoxy.
Laid the second - put a lot of epoxy on - and then laid the third and final - with more epoxy.
Placed a piece of peal ply.
Placed a breather cloth.
Put on the vacuum bagging and attached.

Before the real crappy end result I have a few questions:

Could my vacuum pump be pulling too hard? It isn’t huge but maybe a little too big for this job. It is a 5 CFM 2 stage 1/3 hp Robinair. Tons of resign ends up in the breather cloth… The Carbon Fiber feels very dry and has a mate finish. Is there a specific number I should pull instead of letting it drop all the way to 30?

The carbon fiber doesn’t get down in the corners very well - comes out of the mold rounded with just resign in the corners. Could the breather cloth be too thick? Or am asking my setup to do something it just can’t.

Thanks all for your comments / suggestions / jokes. Communities like this make the world a hell of a lot better as it gives people the confidence to go out and do something they never thought they could!

#2

What is the white item in your pic? Which surface are you trying to get a better finish on? Yes the carbon looks dry.

#3

your pics are showing the Unfinished side of the part that is supposed to look the way it does,
either you are fabricating it backwards or or you are not showing what the problem is,

#4

Hello!
As above, are you talking about the B-side surface? It looks alright and is the way a peel-ply surface is pretty much supposed to look like.
If you’re talking about the mould surface, there are a few things you can do: The mould itself doesn’t look great but the main problem is the control of resin suction. A few things you can do, but the first step is a perforated release film (fine perforations) to control the flow a bit more. If there’s a load still coming out, limit the time under vacuum - eg if your resin doesn’t gel for 2 hours after putting it under vacuum presently, decrease this to say 15 -20 mins by not applying the vacuum for 1.5 hours after you have everything laminated. What resin are you using?

Regarding the fibres getting into the corners; this is called bridging and is due to a number of things, most notably the fibres not being placed into the corners correctly like this
https://fugahumana.files.wordpress.com/2012/07/fibre-bridging.jpg
or the bagging materials (peel-ply, perforated film or bag) stretching over the corner like this instead of into it:
http://www.bertram31.com/proj/tips/void.gif
Cloth type can also influence this but your twill weave shouldn’t be a problem. Take care when laminating to really push the fibres into all the corners and also when the suction is applied to the bag.

Keep at it and it will work!

#5

This just looks like straight up bridging.

I can see the bag in the pic appears to float across the corners.

You need to push the bag into the corners with a safe but sharp tool.

Wet layup vac bagging like this with any detail corners etc is always going to be difficult to get perfection. Best to use infusion I think.

#6

If you put the breather directly onto the peel ply without a perforated plastic film between the two you will have a bad time. The breather will suck up a lot of the resin from the fibre leaving it a bit dry, which is likely what happened.

If you are happy with the look, try turning the fibre 45 deg. When a cloth is at 45deg to the edge it will form up better. If you are not so keen on the look, put the first layer at 0/90 and then the remaining layers at 45degs.

I know it looks good when the bag is flat without any creases but it is better to have extra bag over the part. I like to pinch up a little fold of bag in the corners and edges. Although the bag does stretch a small amount, a pleat/fold allows the bag to ‘slide’ and push into the corner better.

#7

Thanks all! Everyone has been most helpful. Now that I have read the comments and went back to working on a few more items I feel like I was quite the DA…! It is funny - you can read all the sites / watch all the videos - but until you do it you just don’t know.

My end game is to do these parts with vacuum infusion but I’m just starting to do that (did the first one last night).

#8

findhan - I am using West System 105 / 207

#9

also it looks like you’re not using any pleats. Pleats would eliminate bridging in the corners or over any elevation change.