Who's worked with kevlar fabric?

[erikgreen]

Hey, I have a question for anyone who's worked with kevlar fabric.

I'm working on the BOM for my new project, and I'm looking for something to impart a significant abrasion resistance and puncture resistance to the below the waterline hull.

Since this will be a home-built boat, it'll be wood cored (I can't afford foam) and any puncture will add moisture to the hull, which will be very hard to get out again.

So I'm thinking the final layer of laminate could be epoxy and kevlar, painted to protect the epoxy. Or could I use vinylester?

Other suggestions welcome, I'm still in the design stage while I work on my workshop space.

Erik

 

[oops!]

Re: Who's worked with kevlar fabric?

VE or poly wont give you the stregnth equal to kevelar.....so the added benefit you get from the composite will be lost against the VE resin.

it would be kinda like appling a steel patch over wood with white wood glue.

epoxy is the only way to go with composite fabrics.

the problem is that you would really have to give it a lot of coats of epoxy as kevelar is not water impervious....that would mean 5 coats.

and im confused....a kevelar bun on your hot dog?

 

[erikgreen]

Re: Who's worked with kevlar fabric?

Oddly, that's part of what I was thinking

Is there something besides kevlar that would provide puncture resistance? I suppose I could just put an extra layer of glass on the bottom, and extra tape on the keel and chines instead.

I saw some woven fabric somewhere that was half glass, half metal mesh, although I think it was decorative more than functional.

Hm.

 

[oops!]

Re: Who's worked with kevlar fabric?

ill think on it.....its not only puncture proof you want....its also to protect the core from getting wet......

i think kevelar is a great idea.....but youll have to sell the house and garage to afford it

 

[erikgreen]

Re: Who's worked with kevlar fabric?

ill think on it.....its not only puncture proof you want....its also to protect the core from getting wet......

i think kevelar is a great idea.....but youll have to sell the house and garage to afford it

Would I get to keep my boat?

 

[oops!]

Re: Who's worked with kevlar fabric?

actually....i know a guy up here with a bolt of it just laying around.

i was thinking of getting some of it for an idea i have.......if i can score the whole bolt !!!!

 

[erikgreen]

Re: Who's worked with kevlar fabric?

Hmmm.. I'm looking at 16.50 a linear yard here, at 38" width. So I'd probably need to buy about $300 worth to get one layer on the boat bottom. Compared with $180 for 18 oz. e-glass or $120 for biaxial with stitched mat.

I've gotta think on whether the kevlar will be worth it. Anyone have numbers for how much more puncture resistant kevlar is than plain e-glass?

Erik

 

[NelsonQ]

Re: Who's worked with kevlar fabric?

This might help.

http://composite.about.com/od/aboutcompositesplastics/l/aa050597.htm

 

[Bondo]

Re: Who's worked with kevlar fabric?

Ayuh,...

Old Town Canoe sells Kevlar Skidplates for their Canoes,...

I've put a few of them on,...
As far as Skid Resistence,... It's just Unbelievable...
I can drag the canoe across a blacktop road, with nary a scratch....

It goes on with epoxy, just like any other fabric...
Except it's softer,+ doesn't cause the Itch...

 

[oops!]

Re: Who's worked with kevlar fabric?

according to legend.......you cannot puncture it......except raw cloth and a needle.......

i hear even cutting it is a chore

 

[i386]

Re: Who's worked with kevlar fabric?

I've worked with kevlar, sort of. My trailer slides are covered with think kevlar fabric which was salvaged from the sheath of a retired fire hose.

This is interesting. What kind of rock proof craft are you designing Erik?

 

[jonesg]

Re: Who's worked with kevlar fabric?

I bought some yrs ago and use it for reinforcement inside joints,
its a gag to have someone try and cut it with scissors or a knife or an axe.
Ceramic blade scissors cut it by chopping.
I think mfgers use laser.
One thing I'd try avoid is having it in a finish coat, its not sandable , it just produces more fuzz if it comes through, so I use on inside layers then glass over it.

Kevlar tape is much easier to handle than the cloth for reinforcement of joints.

 

[daviscfad]

Re: Who's worked with kevlar fabric?

I have had to sand kevlar and it sucks so be sure to get some paper suits several of them and a full face mask and a spray sock for your head.. Get you some gloves also.. did i mention it sucked sanding it?!?!?!.. If you do it right its there for your lifetime.. At the boat yard i worked at we mad 72 and 80 foot sport fishing yahts and the hulls were constucted with corcell and kevlar

 

[SnappingTurtle]

Re: Who's worked with kevlar fabric?

The “rowing club” where we keep our boat, has skulls completely made of Carbon and Kevlar. The designs are really complex, but light and strong as a tank.

I don't know what is used as the final coating to water proof them. The fiber is visible, and smooth as glass. It is obvious it is molded and vacuum cooked, just not sure how or with what. I asked and they just shrugged their shoulders. They just row, they don't build.

Could you not layer up an outer skin of Fiberglass/Epoxy, or Gelcoat over the Kevlar for water proofing?

There are also several local race shops working with it for "one off" pieces, but they do a lot of work for the big Auto & Plane manufactures, and their shops are guarded around the clock, like Fort Knox.

I have spoke to them, and while nice and helpful, they are at the same time worried about industrial espionage. Understandable. They all use the molded and vacuum cooked method, and have often let me in to watch, but won't go into details about their recipes.

If you ask questions, they get real jumpy. So I don't.

 

[jonesg]

Re: Who's worked with kevlar fabric?

in a mold prepped with partall wax and pva spray...
I first went with epoxy paint (or gel coat) , then epoxy resin, light cloth then heavier cloth then chop' matt , cloth, the kevlar then more glass cloth.
The point was to keep the kevlar away from the outter shell.

 

[erikgreen]

Re: Who's worked with kevlar fabric?

I'm sure I could do a layup like that, but I thought the point was to keep the kevlar near the outside of the layup in order to provide resistance to damage?

Or would it just be good to have it deep in the layup in order to be a last defense against a deep puncture?

I'm basically wanting something that will prevent a puncture through to the core in certain parts of my hull that are likely to hit the occasional sharp rock.

Erik

 

[daviscfad]

Re: Who's worked with kevlar fabric?

I am trying to think how i remember them laying up the hull I know they waxed the mold sprayed gel coat. I wanna say they used some 1708 after that a 1" or 2" corcell then the kevlar. I know kevlar was the last thing they used but i dont know if they used it 2 times or just the last layer

 

[jonesg]

Re: Who's worked with kevlar fabric?

I'm sure I could do a layup like that, but I thought the point was to keep the kevlar near the outside of the layup in order to provide resistance to damage?

Or would it just be good to have it deep in the layup in order to be a last defense against a deep puncture?

I'm basically wanting something that will prevent a puncture through to the core in certain parts of my hull that are likely to hit the occasional sharp rock.

Erik

something would get damaged , epoxy resin cracked etc, the idea is to avoid having the kevlar show through, its easier to repair glass than kevlar.
Then it would just be cosmetic repairs.
I got my cloth and tape from fiberglast, they said to keep it towards the inside layer rather than the outter layer.

 

[daviscfad]

Re: Who's worked with kevlar fabric?

oh yeah when you sand kevlar it like shrivels up doesnt get smooth unless you add a faring compound

 

[erikgreen]

Re: Who's worked with kevlar fabric?

Urg.

It's sounding like I might want to just try for the same results with an extra couple layers of biax in a few places.

Since the hull's going to be relatively heavy (I'm not going to portage it I won't get any advantage from the kevlar that I'm not getting from extra glass, and it will definitely be a problem to work with, and expensive.

I expect if I hit a rock or the shore hard enough to punch a hole through the glass, I'll inspect the hole at the first opportunity and dry/patch it. It's not like it's going to happen without my noticing, right?

Erik