cutting kevlar .... lay-up and vacuum bagging

[wet-foot]

what's the best way to cut kevlar cloth, what about carbon fiber? Also do these materials wet out like regular fiberglass cloth, I'm using epoxy for resin?

Any advise on vacuum bagging? I was wondering what other release material and breather material works in the bag? I hear you can use pink insulation for breather and nylon ( bug ) screen for release. Any pro baggers with advice? thanks in advance.

[Tim B]

Carbon can be cut with sharp scissors. Carbon poses no great problems to wet out.

The easiest way to cut Kevlar is to paint the line you want to cut with thinned Cellulose Dope (ask the model aircraft world about this). This should dissolve later on contact with epoxy, but it will just hold the fibres together well enough to cut them.

Kevlar is a pain to wet out. If you can get away without it it will make laying up much cheaper, easier and quicker.

nb. If you were using Pre-preg there wouldn't be that much difference.

Cheers,

Tim B.

[DGreenwood]

I have never used bug screen.I can't imagine it? I have, however, at times when I didn't have anything else, used nylon flag bunting. Available at fabric stores. Not as good as the real thing though.
Breather can be lots of things. Bubble wrap works as does may other things. If you need to absorb excess resin then blanket material is the best choice. Again it is hard to beat the stuff sold for this purpose.

[wet feet]

There are special shears for cutting Kevlar.The brand name escapes me but I can recall that they are made in New Zealand and they last quite well.You must have a compelling need to use the properties of Kevlar as there are disadvantages to it that need to be considered.Besides being hard to cut,it fuzzes badly on cut edges of the laminate and it suffers from degradation in ultra violet light.

[Jimbo1490]

The best cheap shears to cut Kevlar are the large Fiskars, BION. You will need to purchase thier sharpener with the large shears and resharpen a few strokes after each 4 foot cut, but it will work. All the other shears I had in the shop were good quality Wiss and Mundial steel shears but the metal was not hard enough. The Fiskars are made of a very hard steel and hold up to Kevlar OK albeit with frequent re-sharpening. Remember this ONLY applies to genuine Fiskars, NOT cheapo Chinese copies of Fiskars. I paid $28 for the large Fiskars at Wal-Mart, so they are not the cheapest scissors you could buy.

A good way to wet out difficult materials is to make your own 'pre-preg' by laying the cut reinforcement on a work table on a sheet of 6 mil clear polyethylene, then pour a sufficient quantity of resin right in the middle. Then lay another sheet of clear poly over the top and commence spreading out the resin with a squeegee. Since you will be working on dry plastic to spread the resin sandwiched between, it's very quick and clean. And it's completely obvious when an area is wetted or dry. When it's all wetted out, firmly squeegee out to the edges all of the resin that you can. This will approximate to proper resin/fiber ratio so there is not too much squeeze out later, or worse yet a rich layup. It makes no sense whatsoever to use an expensive reinforcement if you are not going to pay attention to fiber fraction and use vacuum bagging to boot.

When you are ready to apply, peel the plastic off of one side only, place the wetted cloth in its spot, squeegee it down then peel off the remaining plastic. If the pieces of cloth are cut to shape, you'll need to keep straight which is top and bottom.

Jimbo

[Jimbo1490]

On the release, sail cloth, Ceconite aircraft covering and the like work OK and leave the desired texture for subsequent bonding. This is of special importance with a Kevlar layup since you do not want to sand it AT ALL.

For the bleeder/breather layer just use the sheet polyester fiberfill, the kind they use in the furniture businees between the polyurethane foam and the outer upholsetry. It's really substantially the same stuff as genuine bleeder. I have never heard of anyone using pink fiberglass insulation; sounds a little whacky to me, but you never know what you do until you are pressed

[wet-foot]

'pre-preg' ......... I had heard the term but wasn't sure of the process. In guessing how to do it I missed the top polly sheet. Is the purpose of the top sheet to protect the fabric while using the squeegee?


I lay everything up with epoxy and glass. I picked up a bit of carbon fiber and Kevlar to see what it is like to work with. Sounds like the carbon is no problem, will see how I make out with the Kevlar, will definitely do the pre-preg thing.

My project is a small, 3 sections of about 6 sq feet each so it should be pretty straight forward. I will bag everything to obtain the superior results. Because of the small lay-up area I was not too concerned about the top finish as sanding it out takes only 10 minutes or so. That’s where I was going with substitute bagging material, if something else gives me the strength but requires a bit of sanding it is no big deal. I will do bagging tests to see how it goes. “Pink insulation” …….. I’ll be the guy in the little boat that looks like candy floss or it is wearing a pink mohair sweater. Hey this just might turn on the chicks!!!!!!

[fiberglass jack]

if you are in toronto , there are a few companys that sell all the baging stuff, i see your going to buy carbon and kevlar and epoxy, most of these places will give you a good deal if you buy the cloth and resin off them. u could use regular poly for the bag not the best though, and the pink will work fine but messy, u will need a release fabric nylon will work ive used wax paper that is perforated work good, but save yourself headaches and get the real stuff

[buckknekkid]

I was about to send out the hounds Jack, where ya bin?

[fiberglass jack]

busy fixing botes, god love all those bad captains in toronto.

[wet-foot]

I bought all my cloth from Noah's in the Toronto area, are there other retailers that you know of that I can try, their websites?

Does anyone have experience with resin infusion bagging? I have found a few places that sell their info along with kits, but very little free info.

[fiberglass jack]

lots of places try smithcraft on the queensway, rayplex in oshawa, compasites canada in missisauga, give me a call 416 5001250

[marshmat]

Hey wetfoot,
Vacuum infusion is a really effective process for a production builder, but it's way too expensive and difficult to get it to work right for a one-off. There are so many fittings to mount all over the place, all of which have to be perfectly airtight, etc.... and infusion does not tolerate ANY leaks, while plain old bagging (wet layup) is a lot more forgiving.
I use mostly Airtech materials for bagging.... http://airtechonline.com/ they've got some fairly economical stuff as well as the aircraft-grade bagging supplies. It really does help to use decent releases, peel plies, etc; substituting other things has generally led to a lot of frustration and a few broken parts.
I don't have much experience with wet-lay Kevlar/carbon, I work mainly with prepregs for these fabrics.... in my experience, though, neither wets out quite as easily as glass but they don't pose many problems either. Kevlar's notoriously tricky to cut, sharp scissors are best for the dry fabric while a utility knife does the trick on the prepreg.
Jimbo's little trick of wetting out between plastic sheets, then laying that on, can work pretty well. Make sure you do some practice/test pieces before going all-out though.

[wet-foot]

I will stick with vac bagin, can experiment with some techniques to find what works best. Will research the supplier list to, thanks for all the info and I will definetly give the prepreg ago.

[buckknekkid]

Lets all get together at the Boat Show and bring our scissors. We can huddle around a fire of burning Canadian Bacon and toss in those ridiculous frickin Bell Beavers. Who's in eh?