New to everything composite based! lots of questions after reading

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#1

Hi guys, so glad I have came across this forum, I’m from Australia and started to play with carbon. I have no previous experience with carbon or fibreglass so going through a massive learning curve. I’m starting off with skinning parts (anything I can get my hands on, timber, spare car interior parts and such) with an overall goal to eventually mould and make parts with vacuum bagging or possibly infusion.

Sorry for the long post!

Here are what products I’m using
fabric - 3k 2x2 twill carbon fibre
resin - west 105 epoxy with a 205 slow hardener (also have 206 “normal” hardener on its way)

Question or issues I have

I’m having the same issue as most people of the carbon not sticking down right, lots of the parts I’m doing I don’t want the cloth around the back so I want to trim it tight to finish at the face or edge of the part. The steps im taking are as follows,

1 - sand my part down with 120 grit wet and dry
2 - Wash part and wash again then wipe down
3 - Tape up all places I don’t want resin to get to and trim excess.
4 - Wipe down again
5 - mix up resin and apply first coat, now this west resin seems rather thin and I’m having some fun learning the stages of curing. I have waited till its “tacky” and i can see my finger print in the resin but don’t get resin (or very little) on my finger
6 - lay my cloth down.
7 - recoat with resin and let part dry over night.

Some things I know I’m doing wrong here!

  • Mixing my resin a little fast as I’m getting some air bubbles.

  • Cutting my cloth way over size and having trouble trimming excess once i lay it, I seem to “move” the cloth around a little.

  • Putting to much resin into the fabric (this seems to be a major cause of fabric lifting from what I have read on this page)
    So now to the issues.

  • Cloth lifting in step 6, cant exactly work out why here but it seems to lift at edges and corners. I use tape to hold down the cloth on the back side of the part but still have issues in some places of lifting.

  • Cloth lifting in all the grooves or dips when I apply the resin to wet out the carbon, from reading threads on this site im thinking I should be placing my fabric and rolling it into the tacky resin and leaving that to cure.

Questions I have.

  • What is the best way or at what stage is the best time to cut the cloth back to be a at the edge of the part. I understand there will be some sanding here, im going to take a guess and say it would be after the first base layer of resin has hardened.

  • With skinning complex shapes is it worth vac bagging the part to get a tight fit in all the dips, groves and corners or edges? the set up seems a little tricky but also looks to give better adhesion to the original part (cloth will not lift). This will give lines and creases but will that only be in the resin?

I had a “ok” finish on one of my parts, it was basic but I was unable to keep the fabric down on some edges and grooves. it was a pain to cut with 3 layers of resin that I mostly rubbed back anyway so looking to refine my process to limit the time that I have wasted doing extra work.

thanks for taking the time to read this and I am so happy I found this site, loads of great information.

#2

Learning the ropes of working with these materials and processes is a long road and best learned from trial and error along with all the studying you are doing.

You could try West 105 with 207 hardener (3:1 ratio), this hardener is especially for surface coating, it’s thicker and tacks off reasonably quick too. Then use the same 105 resin with the other hardeners for wetting out.

#3

Thank you I’ll give that a go. Getting a stack of spare interior items on the weekend to play around with as my drag car shell but got lots to learn before I do te body on this thing.

#4

So,

I gave it another go, was out of carbon so used some Basalt I had laying about (dont know why I had it)

Still had some lifting issues but I took my time with this one, also used 80 grit to prep the parts. Its looking much better and and I just finished the last coat of resin. Lets see how this one turns out!

I’ll be trying super 77 next as from the reading it seems to hold the cloth in position better.

Thanks for the help so far guys, im guessing ill have lots more questions when I progress further!

#5

Have you tried wiping the item with paint prep wipes to ensure 100% no grease or dirt? also as the item has been sanded is it possible some moisture is still in the scratches?
I have tried wrapping a couple of things too and had similar issues so very interested in how it goes as I just ordered some more carbon cloth.

#6

I would not prefer to use slow hardener for small parts. I like fast for that

#7

Alibro,

I sand the part with 80 grit, wash it, let it dry and then wipe with acetone, let that flash off and sit for a bit then start. I got my super 77 delivery today and 5m of carbon cloth so ill be playing some more on the weekend. I’ll post up my results.

#8

Look forward to hearing how it goes.
I am new to this business too. I have made a few moulds and parts in Glass but have only wrapped 2 parts so far with carbon, one was quite successful but needed a lot of sanding and fettling to look good, the other was a disaster and ended up in the bin.

I really must spend more time in the tutorials section. :slight_smile:

#9

So i have been on line for a bit but also playing with carbon still. I found the super 77 very very helpfull with skinning items. The few items I have done are great and I must get some photos up.

Running into a few other issues when it comes to placement of the carbon when there are holes that the carbon needs to sit into (like a glove box cover where the handle is) but will try a few methods to over come this.

Im getting real keen on making a mould of something next,

Thanks for all the help guys!

#10

You might want to check out what these guys do. They wrap car parts for a living and you can see the whole process here.
http://ocarbon.com/blog/

This is how they make the foam mounts for the pieces
http://ocarbon.com/blog/2011/03/making-simple-molds-for-the-b8-vent-and-mmi-pieces/

It looks like he has made a frame out of 20mm electrical conduit and drilled holes along the length of each side. I presume he has the pump attached to the conduit somehow so it pulls the bag down evenly. It also looks like there are holes in the foam so the vacuum pulls the bag down in the middle of the part.

I saw a guy using these with prepreg parts.
http://www.ebay.co.uk/itm/LARGE-JUMBO-VACUUM-STORAGE-SPACE-SAVING-BAG-BAGS-VAC-BAG-SPACE-SAVER-BAG-/130926965594?pt=UK_Storage&var=&hash=item1e7bdaf35a
If you haven’t got access to proper vacuum bagging stuff it might be worth a try when wrapping to hold the carbon in shape while it cures.