Hi,

I am planning to build a carbon bike frame and have a couple of beginner-questions.
I will wrap the carbon fiber around a plug and vacuum-bag it.


Q1. When I wrap the cloth around the plug and use peel-ply. I wonder when the carbon is done and I remove the peel-ply. Don't I need to sand the carbon at all before adding the next layers?

Q2. When can I saw and use sand-paper on the carbon fiber with minimal risk for my body.
I read in a forum that you should wait more than one week until you can sand it (the epoxy has to really harden before).
I have bought the resin and cloth from you

Q3. If I want to wrap the cloth around an irregular plug. Is it ok (strength-wise) to have small pieces that I use to wrap around it or must I use a cloth that is bigger than the plug.
Naturally I will use several layers, but can I use pieces that are much smaller (say 10 cm long) and put them on the plug like a bandage?

/ Marcus

Kolla här:

Thanks. Yes, I have seen his videos.

My main question is how long does I have to wait until I can safely sand the carbon fiber.
I intend to use a breathing-mask and do it outdoors, but in this video (produced by http://carbonmods.co.uk/ )
it seems as you can sand just after a night. Is that correct?

http://www.youtube.com/watch?v=gCY8tLHyeJQ

/ Marcus

Hi,

The time you need to wait before sanding your composite depends on a few things:

01). The resin you choose. Some will cure in 8 hours, some will cure in 16, some will be fully cured in 1 week but demoldable in 24 hours. If you buy your resin from EC, you can see their datasheet listed on the website, in which you can find the cure time. When you can demold it, usually you can sand it.

02). The room temperature. Usually resins cure time is "calculated" on a given room temperature. Say if it cures in 12 hours at 25°C, it may take a WHILE longer at 15°C. You may even ask yourself if you put the catalyst (reminds me of someone I know   ).

So, you need to check datasheet of your resin to have an idea of cure time. If you work in a colder area than what the datasheet sez, I suggest you to put a few drops of the resin you used for your part in a liner or on a sheet of whatever that will resist resin (scrap metal for example). Put this liner or sheet in next to your curing part, so your part and the resin drops will be in the same temperature. After some time, depending on your resin datasheet, try to force your nail in the drop. If resin shows an inprint, its not cured. Repeat "nail test" untill resin resist your pressure.

From my experience in hand laminating, thats all I can suggest. I bet other would have some neat advice to share.

Hope it helped.

 



 


    A $1000 electronic device will always protect a 10 cents fuse

Hi Marcus,

With regard to your sanding question, you can sand the material as soon as it is hard enough to do so, using a good quality dust mask and doing the sanding outside should provide adequate protection, essentially you must try to avoid breathing the dust, sanding with water can help to reduce air-bourne particles too.

With regard to your question on using smaller peices, although with sufficient overlap you will be able to acheive good strength you should aim to use continuous lengths wherever possible as this will keep the weight to a minimum. obviously around the complicated bottom bracket, headtube, seat stay-seat tube areas you will need to do these in smaller peices, you should aim to wrap these first with your main tube peices lapping over them.

Peel-ply will give you a surface that is ready to be wrapped straight onto, you will probably find that a little bit of sanding to level the surface will still be needed. A neat trick I have seen used is to 'bandage' the peel-ply around the wetted out carbon, this squeezes out the excess resin really well.

Paul Statham
Easy Composites / Carbon Mods - Technical