Hi

I have had some kevlar/carbon cloth sitting around for some time now. I want to see if it is of any use for props. One layer pure carbon, one layer kevlar/carbon mix. At least it should look good.

But how do I cut the bleedin' stuff? I don't have the special scissors you can get. A roller knife maybe?

I know now why the stuff is used for bullet proof vests!

Michael

Michael,
Go back and look at your CF prop thread. I posted about it there. I tried CF/Kevlar blend cloth and gave up. As far as I'm concerned it was a waste of money and time. I got incredible "fuzzies" on the final molded prop, and cutting it with a very sharp razor blade before molding was a hassle too. I've stuck with pure CF cloth ever since.

Gordon

Micheal,
whatever you use must be SHARP!
even if you intend to drill holes in it you need to sharpen the drill , I even think there is a recemended way to sharpen drills so they dont break . yep its tough stuff
Stewart

Michael,

I've used Kevlar at work for over 20 years, and in that time we've used all kinds of expensive Kevlar scissors and such. They mostly have serrated blades to catch the Kevlar fibres and prevent the cloth simply pushing forward out of the way of the blades.

OR we use a brand of cheap kitchen shears. Over here they are called "Tullen Shears", they are so cheaply made that they have rough ground blades with no post sharpening which is just what is needed to catch the Kevlar. They only last a few tens of metres cutting, but they only cost a few dollars.

Trimming cured Kelar laminate in more problematic. You can use the Tullen Shears, but this will leave a furry edge which cannot be sanded off. I have heard that you can burn away the exposed fibres, but if you try this don't breath the fumes. Generally, we design the laminate so that the Kevlar is just free of any edge that will need trimming, thereby avoiding the problem.

Graham.

Thanks for the advice Graham. I had thought of cutting the kevlar to shape before putting it on the prop blank. The motivation for using kevlar was to have a strong prop, but I have yet to break an all carbon one.

The kevlar/carbon mix does look good though

Michael

I was going to get some of the mixed but after talking with the guy from freeflight supplies I didn't bother. You end up with the worst of both worlds. The carbon breaks and the kevlar bends so you end up with something tht although not broken isn't much use. Then there is the trimming.

Some kevlar tows/thread running lengthways between layers of carbon would probably be good. FF suplies have some excellent thin kevlar thread, much better than the thicker stuff for our needs (PM me if you want some, I have loads)

If it is on the surface the mould must be good, you can't sand it like carbon, fuzzy fuzzy fuzzy

Graham

Michael,

I found that you can cut kevlar with ordinary scisors if you treat the area you want to cut with medium CA. It is important to use mediun and not thin CA. The spreading of thin CA is hard to control and may go much farther than you want it. Mark the line or shape you want to cut. Apply a very thin coat of medium CA glue. Let it cure completely and cut the desired shape. It is important to make sure that your CA bottle opening is small so you could have a control of the amout of CA you are applying .

Zoran

I actually was lucky enough to have complete sucess with cutting this darn stuff.... once. I was visiting a friend of mine at his workplace that does all sorts of special fabrication. Their 5 Watt cutting laser will trim CF, Kevlar, Fiberglass and ham sandwiches with no damage to the host substance and perfect edges. I am planning to get one for myself but am having a hard time saving up the $20,000.00. Oh well, it was fun while it lasted....

-LY

I think it is a little more than 5W if it will cut these materials? I always though that lasers didn't work well on carbon or perhaps that is only the cured type.

Cool things, or is that hot.

Graham

YOU got to cut your sandwiches!!!! AWSOME imagine a laser knife slice through steak with EASE

If your steak is that hard to cut, it's probably a "missteak." Try the Kangaroo, much better.

Now would that be a very nice thing to do, to give me the grizzly end of a kangaroo to chew? Just kidding.... You know, maybe it was more than 5 watts but this thing carved through my CF/Kevlar blank like a chanisaw through a loaf of bread! They also have a "water knife" and a bunch of other HYPER-Cool machine shop stuff that would make any hobbiest pant. Next time any of your are out by Rt. 495 in S. E. Massachusetts maybe if you ask really nice they will let you borrow their stuff........

We can dream.... -LY

Oh, and as for we mortals, I agree completly with Gordon, the stuff is a complete waste of time and money, no matter what you do with the stuff if will cause more problems than you were trying to solve. Stick with the proven materials.

-LY

Santa should give all us nice boys a laser for Christmas

Michael

A little trick that I've seen work is to cover the area you want to cut with a strip of masking tape. Then cut through the masking tape and the mat at the same time. The tape holds the fibers in line. It definitley improves things, but the scissors still wear out quickly.

Geoff