Is there a good way to get carbon to go tightly round a right angle?

Thanks

Hi.

If you use vacuum, it will help. But as always you will need to massage the bag with some tool to help fabric go in the corner. A rubber rectangle would be used there, so it will not make a hole in your bag. You may have to massage the bag several times depending how complex is your shape.

If you lay your fabric  "outside" a mutliple right angle part (a cube for example), some cuts would help.

And also I saw people who would use spray glue (3M 77) to help hold the fabric in place.

Hope it helps.

 



 


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

Where would you place the cuts? It is the the outside I was thinking of and don't have access to a vacuum pump ()).

without a vacuum pump it will be tough to keep the carbon in position.

you could make a (blunt) right angle tool to press on the carbon to hold it in place.  It would need to be release coated so it doesnt stick.

I wish I could afford a vacuum pump .

Hey,

Dont forget the spray glue, it could really help you in a non-vacuum process. i have no idea if it will leave cosmetic marks but I'm sure it will help, as i seen people doing it before wetting their fabric, and the part done and painted.



If you want to lay your fabric on the "outside" of a cube, I would make my cuts on all vertical edges. I know it will not appear as "one piece" anymore, but its better than nothing. If you part is subject to mechanical constraints, you could still reinforce the cut areas by adding some band to "overlap" the cuts, if it makes any sense.

Hope it helps.

 



 


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

Just remember if you cut down the corners, you will need on the structural layers to cut it differently so it doesnt just break on the corners. eg wrap a length of carbon around the 4 sides then use a blob spray tack to hold it.

better still, use a long tow of carbon to in effect tie around the box rather than glue.  it will lay flat nicely and not effect cosmetic finish.

You will find it much easier to use profinish carbon when doing complicated cuts as the edges of normal carbon will fray easily looking messy.

ideally pre-preg would suit such a part as it is sticky so would cut nicely and hold itself in position while you lay up.  However i understand cost may be prohibitative.

Warren's right that ProFinish might help you a lot in getting a good cosmetic finish on right angled corners. You can have complete cut and butt-joined panels with ProFinish and once clear resin or lacquer/clearcoat is over the top, you can almost not see such cut-lines at all. To second Warren on the structural aspect of this then if you did this you would need to ensure that you'd got layers underneith that do span the corner, otherwise you'll have no strength there at all. Of course, if you're just doing this to add a carbon appearance to the outside of an existing part then there's no need to concern yourself with the strength, just use ProFinish and make separate panels for each side, meeting neatly in the corners.

One tip along the lines of what Joe is describing where you put some positive pressure on the laminate to hold it in place whilst it cures would be to put release film over the part after you've laminated it and then use something large and squashy (like a car spong or the sponge out of a sofa cushion) and press that against the laminate, particularly on any difficult corners. It will need to be held in place for the whole cure time (so use something else to wedge it there). This technique should be able to hold carbon in place on the outside of a right angled corner. I guess you could describe this technique as a poor-man's vacuum bag; we've used it to good effect on some awkward mouldings where the carbon doesn't want to stay where it should.

I hope this helps, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

I have just been informed that our inflatable bed inflater actually has a vacuum/deflate mode. While I imagine this is no where near as good as a proper vacuum pump, will it be strong enough just to keep the fibres in the corners? Will it have to be on the whole time while the piece cures?

Hi Joey,

Your right in thinking that an air-bed deflator would not have anything like the level of vacuum normally required for composites, I would imagine that it will have much less than a vacuum cleaner; which isn't normally enough to make any real use of. It may help to hold the carbon down in the corners slightly but you would still need to make a proper vacuum bag.

If you have absolutely no leaks in the bag there is no need to leave a pump running. Like with many areas of composites it may be a case of experimentation, I would be suprised if it yields the results you are looking for, however this industry is full of suprises!

Paul Statham
Easy Composites / Carbon Mods - Technical