Hi guys how does one get such a finish from dry carbon fibre or the only way is via prepreg, see the picture below
thanks
I’m not sure I understand what you mean when you say “dry carbon”. If your referring to using cloth and resin then that finish could be attained a few different ways.
One way being vacuum resin infusion.
All methods can produce a finish like that with some experience and skill, whether it be hand layup, wet bagging, vartm, prepreg etc.
Start with wet layup, it takes the least amount of equipment and teaches you a lot. Don’t rush the mold, it is the most important part in achieving a perfect surface finish.
It takes some time to perfect any method, I usually use fiberglass the first time just make sure everything is right, then I don’t waste expensive carbon fabric.
Also, search this forum, most questions have already been addressed.
Good luck
Jacques
Hi Extreme/Cyclone101, thanks for the response i have attempted both hand lay up and resin infusion but i have not attained that perfect finish, attached is a pic of the latest finish i just got from wet lay up and vaccum bagged, see the attached pic where 2x2 twill was used
thanks
a double,
The part you did looks pretty good in the picture. What is wrong with it?
You can get that finish by infusion. Wet layup will always have pinholes. Take a look at this showcase trhead
If you want that deeper, wetter more 3d like look, try to paint it with a clearcoat!
I’m guessing your problem is that the weave does not look square?
To get it like that you need to compact it more and get it wetter. If you use more resin on your first layer, the fibers will move around more freely and then when you vacuum it you will get a better finish.
You can also sand the fibers down till everything is level, then coat it with a clear coat. Just be careful that you don’t sand too deep.
Hi cyclone, yeah i’m looking for that square look :), i guess it also has to do with the compaction cos on some sections i can see that square look. i will try one more time.
thanks.
Hi DDCompound, on my 1st infusion attempt i didn’t getting that look maybe its because i used wax and PVA on the mold and maybe is i had gone ahead and clearcoated the part it would have looked great, on the picture i attached i moved away from wax and tried Frekote and the results were 100 better the part just popped from the mold as compared to wax+pva where i had to pry the part from the mold coz it got stuck and i ended up ruining the part 
thanks
While I am still pretty new to carbon fiber work I have no idea what you two are talking about by more compact square look?
Can you show me a picture of what you are talking about?
Don’t sand in to the fibers, I would think you would want to avoid doing that at all cost as it will ruin your part.
By “square” I think the idea is to lay down the carbon without distorting the weave? So you end up with the carbon laid down in as straight lines as possible?
I think it would be best to focus on achieving your desired result using wet layup only (don’t use vacuum). This will reduce the variables & possible issues caused by using vacuum. Also if you aren’t laying the carbon down straight, then no amount of vacuum is going to straighten it out for you… My understanding is that vacuum is used to achieve better consolidation of layers - that is all. If you have any layup problems, go back to your original process and look there first.
I also don’t agree that wet layup will always produce pinholes. In my (very) limited use of visual carbon with epoxy surface coat I have managed to create pinhole free pieces. There is plenty of info here on the forums that will help you in that area (tips like using a heat gun on the surface coat to disperse bubbles, lightly spraying acetone, etc.)
Go back to square one and do some plain wet layup tests. If you’re using a large piece of carbon you may need a 2nd person to help lay it down square. If you hold the fabric by a corner and lay it down that way I would almost guarantee the weave will not be square, it will distort while you’re holding it and once it’s touched the tacky resin you’re not going to be able to move it.
It may be an idea to stop using carbon and try twill weave glass instead, until you’re happy that you can lay it down square (or square enough to your satisfaction) - if you want to save some dollars.
The surface finish will be the same as the surface of the mould… If you have a satin mould the part will be satin… Simples… As for pinholes. I dont see any reason for pinholes with wet lay and I dont have a problem with using a Vac bag to get a good part either… I just think if you have problems dont spend money on expensive Epoxy resins as it is just throwing money away and I would suggest getting some time making parts using polyesters… just general purpose ones too… Then practice… As Mugget points out get some twill glass and practice with cheap materials… If you worry about air inclusions then add a little black pigment to tint not make the resin fully black and lay up as you would normally… It will help you see air and you will still see your weave… Put a polyester gel coat down too… Dont add any pigment to that… Keep it simple and practice… I still have failures and problems but they get less and less with more and more practice… Dont get too caught up in epoxy resins to start off with… It is an expensive waste if your parts are bin fodder…
All the images are just wet lay polyester parts done in a vac bag…
As i said… My parts are not all perfect and I know some are down to my first moulds and inexperience too… But the key is practice with cheap and simple parts
The part on the left is a pain to lay up due to its shape and small size… It is no bigger than 5 inches by about 2.5 inches… I can make more of them for the same material as I can one of the larger parts… That way I get to practice over and over and throw away cheap parts if they are wrong and I can learn from my mistakes cheaply. I have made one of those covers using a scrap of Carbon Kevlar and used a clear gel coat then when I laid it up I used a tinted resin behind it to see where my mistakes were… I will get a photo later… It shows some bridging and I now know where the problems lie…
Ok as promised… I had some Kevlar scraps that had some pulls in them and odd sizes so I had a go at this engine case protector… I clear gel coated the mould. (It is meant to be satin) then laid the Kevlar Carbon into the mould and worked the material down into a none tacky surface. I was not sure where any problems would be although I had a feeling where the bolt holes go would be tight and could give some bridging. So I mixed the resin for the lay up and added some black pigment. I thinned it down a little too and laid up the part as normal… As you can see it does look a little “Dirty” but I was more interested in bridging ect… The edges where it gets trimmed look a little darker and on the lower right there is a little bridging where the bolt goes in and some just on the lower edge of the circular cover too where it has a transition from another section… This is only a test but it was just made using polyester and scraps so it was thrown away and now I know where to work on. I also use some woven glass at times and just make a couple of throw away parts when I have a new mould to use… If I used epoxy it would be a lot more expensive and this is where I have been practicing my techniques over the past 18 months since I made my first parts…
Hi morepower, realy dificult shape you have there. Which vac bag do you use?
It is not too bad to lay up but like even the most basic shapes I do make some test parts to see where any problem can happen… I use VACFILM450V and just ensure it is not too dry as it does make it hard to get into tighter corners if it has dried a little too much…