Laying carbon reinforcement into wood

11/03/2013 09:36:05
Richard MR3285
Mark....

Here is my contribution

These comments do not relate to the preparation of the wood but just the carbon/epoxy lamination.

With regard to the parcel tape, it is really useful when using epoxy resin as the resin simply will not stick to it. If you wanted to surround your reinforcement area with parcel tape and then use a sharp blade to cut the exact area required you will avoid any chance of getting epoxy where you don't want it. It is also useful for coating any "tooling devices" you may need (eg if you need to clamp something onto the wet carbon/epoxy reinforcement in order to press it into shape). It is basically like a release agent in tape form.

With regard to the peel ply, I think it is wonderfully useful. Although it is a product generally used when vacuum bagging I use it in normal wet lay-ups whenever practicable. When I lay up carbon cloth in a standard wet lay-up, I put the peel ply on as soon as I have epoxied the cloth. Wear latex or nitrile gloves (the latter are supposedly more impervious to epoxy but give slightly less feel than latex). You can then smooth out the whole lay-up. The resin will soak through the peel ply which is exactly what you want to happen. I use a squeegee to express the excess resin (too much resin is not only heavy but is also not strong). Cheap plastic rulers can make wide bendy squeegees. You then leave the peel ply in place until the resin has gone hard whereupon you take firm hold of it and peel it off. It will leave a textured surface which will need sanding (wear a mask) prior to any final finishing (unless you want to recoat with more epoxy). One major benefit of peel ply is that it ensures an even surface to the epoxy. If you just wet out the carbon cloth and leave the surface uncovered you will find that the epoxy will sink into, and follow the weave pattern of the cloth and you will need to flat it off and recoat MUCH more than when using peel ply. Incidentally, there are epoxy resins for laminating and others for coating that have different flow characteristics but generic types do everything pretty well. You could also use unperforated release film instead of peel ply. This would leave a SMOOTH surface whereas the peel ply leaves a textured surface. Personally I always have to refinish the surface anyway and so any texture proves useful as a mechanical bond with finishing coats of epoxy. I also normally want to varnish the surface and so would end up flatting off the surface. Try the unperforated release film if you fancy it! The other significant benefit of using either film or peel ply is that you don't have problems with bloom (amine blushing) that often appears on the surface of newly air-cured epoxy (although if you do get bloom you can simply use hot water to dissolve it away - though not so easy if you are working in an awkward spot!!!!!).
Peel ply is most useful when you are laminating a relatively smooth area (rudder blade, centreboard etc). It is not so useful if you are simply adding reinforcement to an awkward shape. If the peel ply is creased when you get it then it is a good idea to iron it smooth before you use it - those creases will show in the surface of the epoxy and would need to be flatted out later(not really that difficult - it would only be resin and not carbon!).
You ask how to achieve good results. If you want the best cosmetic look from the beautiful carbon fibre cloth you will need to handle it very carefully. There are two main types of cloth. Twill (2/2 twill) has a very attractive weave pattern and it is very flexible but it is easy to distort its weave pattern when handling. Plain weave is stiffer, less flexible (less "conformable") but is more robust to handling. Take your pick. One tip for avoiding distortion when wetting out the fabric is to put a coat of epoxy on your wood and let it go tacky (totally depends on the temperature and your hardener but could be up to a couple of hours). Then take your carefully cut and very carefully handled dry carbon fabric and accurately put it in place. You will not be able to move it around but you will be able to smooth it down by hand. ALWAYS wear gloves ANY time you are working on the project as you risk leaving skin oil on your surface or materials - which would give rise to "fish eye" dimples in the epoxy. Once your carbon fabric is in place it will be stuck by the tacky epoxy and the weave pattern will not move (unless you are very rough). You can then immediately wet out the cloth with resin and apply peel ply and so on. As long as you don't let the initial tacky coat of resin go off fully you will get a chemical bond with the "wetting out" coat.
If you are going to go for carbon sheathing you will need to make sure that water will not be able to get in behind your laminate. Nothing looks worse than carbon lamination lifting off and trapping water in the timber behind. It might be a good idea to have a practice on something else before you start on your boat. It certainly pays to know what the materials feel like and how they behave. Nothing beats a bit of experience!

Hope that helps.

11/03/2013 09:36:05
Richard MR3285
Mark,
Sorry if I misled you. No I didn't mean that you could cut through the carbon cloth when it was (partially) cured and remove the excess because it wouldn't stick to the parcel tape. The parcel tape was really only to protect from overspill of resin. I meant that you could cut the carbon fabric first whilst dry, then carefully apply it to the tacky resin and finally wet it out in situ. If you had "masked off" the working area in parcel tape then you would not have to sand off any resin from the surrounding woodwork. I can see no reason why your suggestion wouldn't work but I have never done it myself (and your timing, technique and cutting skills would have to be perfect). HOWEVER, there is another possibility..... It is possible to buy carbon fabric that is already bonded to a flexible resin film (rather like a pre-preg). The resin film means that this fabric can be handled and cut very accurately in the dry form and then applied and laminated. I have to tell you that I have never used this fabric but I am bearing it in mind for any future projects. I often use a company called "Easy Composites" who also have a sister company called "Carbon Mods". They have a great range of stuff and some videos that I have found very useful in the past. I have put a link to the resin coated fabric (called ProFinish Carbon Fabric below). I must point out that I have NO CONNECTION with these companies. I am just an enthusiast who enjoys a project! Let us know how you get on.

15/08/2013 04:46:37
Edward
Mark - see email

23/10/2013 11:43:01
Mark
So I'm hoping to lay some carbon reinforcement on a couple of small high load / wear areas amp possibly do a little carbon sheathing, the main question I'm struggling with and haven't found a clear answer to is how to lay the cloth into the wood and achieve a result that a) lies flush with the surrounding wood surface and b) has clean tidy edges.

I'm assuming some detailed work with a chisel / router is required in the preparation phase and I've read elsewhere that parcel tape is a useful tool (though without much other explanation), I also believe that peel ply may be another important ingredient but could someone give me some sage advice on whether this is true and how to achieve good results?

Thanks in advance!

23/10/2013 11:43:01
Mark
Edward, Richard,

Thanks both for your responses. I think I'm starting to get an idea of how I can achieve what I'm looking to do. Richard, do I understand correctly that you can lay parcel tape around the area, then cut through the mat at this join to leave a clean edge rather than frayed bits of mat stuck to the surface, I assume this would need to be done after it has dried but before the epoxy has gone off completely? The only other way I can think of achieving a clean finish would be to mould the shape first and then attach it.

05/12/2013 11:15:04
Measurement Man
Mark,

You do not say where you are intending to carry out this reinforcing, but I would add a caution that the rules preclude you from using carbon on the hull shell (see the rules for a definition of Hull Shell).

Regards,

Graham

27/01/2014 05:59:32
Lazy
buy a plastic boat, stockleberry!  ;-)

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