I have never used the stuff and I have an order sitting in my shop for a knee board with a Kevlar deck. The blank is a regular Clark type. It has carved out knee wells. Will both Epoxy or Poly resin work with Kevlar? Will the Kevlar wrap around the rails…and if not, can I cut it with a razor blade at the cut lap? Anything I need to watch out for? Any tricks? Thanks for any info!
Kevlar does not sand at all, any edges that might need sanding need to be buried under another layer. Test your scissors to see if they’ll cut, I’ve had good luck with special kevlar cutting scissors, they’re on the web for as inexpensive as 20$. Epoxy is the standard use resin, the cloth finished “siezing” is the determining factor, the suppliers know the compatibility to various resins for a particular cloth.
Kevlar will wrap, and it can be cut with a blade. You’ll know the resin has set enough to trim when you’re able to cut it. When you try to cut it and the resin hasn’t set enough, the blade will skip right across it. Once it’s firmed up a bit, you can trim it like a cutlap. I put the kevlar on as a deck patch then glassed over that. As the poster before me stated, you cannot sand kevlar, it just fuzzes up. However, if you do hit it and it fuzzes, you can glass over that and it will lay back down. Also, scissors made for braided fishing line will cut kevlar, you can get 'em at most tackle shops for about 5 bucks or so. Only problem is that they’re only 2-3 inches long. For a one off use, they’ll get the job done.
I have special scissors coming from FH. I plan to put a layer of six and four oz regular fiberglass over the Kevlar. Considering the foamstain I need to do on the blank, I really need to use Regular resin as opposed to Epoxy, unless I am looking at a possible disaster. I will be sure that the Kevlar I purchase will be compatible…
If I use Epoxy resin, I will have to do my foamstain with Epoxy, (I think) which will be a pain in the arse due to cure time, and I have three different colors to do, so… I don’t know if I would want to risk an Epoxy Glass job over a poly foam stain…
Not much experience in this area but I am soon to get some! Thanks for you comments!
I have done a few polyester resin foam stains on a polyurethane blank with an epoxy lamination over it - no problems except for it eventually shrunk but every polyurethane foam blank I laminated with epoxy resin did this - ResinResearch on Clark Foam. But there were no problems with the poly foam stain and epoxy lamination bond.
Use poly for the foam stain, glass with epoxy. Epoxy sticks to poly much better than poly sticks to epoxy. Not to insult your intelligence, but don’t put kevlar over anything you want to be able to see! It won’t go clear with resin.
I 2nd grasshopper and surfthis…kevlar only where you want to see Kevlar…and there are different types of Kevlar 28, 49, etc…
The poly foam stains will be fine under epoxy.
Good on you for having the sense to ge shears that will work. Pricey eh?
You must be a glutton for punishment doing this project.
Good to hear that I can do a poly foam stain with an epoxy glass job. Epoxy foam stain would be SO messy. Also FH has scissors for Kevlar that run $16. Not so bad. As for being a glutton for punishment, well, work is work. Besides, I like doing things I have never tried before. I just hope the thing turns out good so I don’t have to stick my head in the sand! Any more insights on Kevlar are appreciated!
Thanks guys!
Good news about the kevlar shears is that they’ll work for your regular glass as well. Whatever you do, don’t get resin on 'em and let it set up! They don’t work nearly as well on the kevlar after that even after removal of resin. Don’t ask me how I know this!!!
poly resin will work with kevlar but you’ll get the best out of it if you use epoxy. the compression strength of kevlar is shithouse and your customer will still get pressure dings on the deck. It also looks really nice until it starts to setup and cure and then it is not that beautiful gold colour but goes a shitty caramel colour.
As everyone else has said you cant sand it so cut lap is the way to go. The problem you may face if you use epoxy, and lam in stages is washing or wiping or sanding the blush you can get with epoxy. Carbon has much better compression strength and is much easier to use.
Afew test pieces may be the way to go.
Daren
Cover and kevlar you can with glass so sanding isn’t a nightmare. Any place you do get fuzzies you can remove that with 400 grit. It’ll knock it down. Epoxy over poly is fine. Stuff is kinda pretty looking when done right but not that useful for standard lay up on urethane. Really good under veneer.
mike daniel posted not too long ago that you MUST protect Kevlar from UV. Just a layer of epoxy does not suffice. so… just hearsay…
because it does not sand, if you insist on wrapping it, you will need to make relief cuts and lay things tight practically by hand.
you do not need special scissors, just buy some cheap shears from Joann or something for 12 bucks and go on using them once you’re done with the Kevlar project. it will dull the shears, but not to the point of unusability.
I did Kevlar on the rails of my SUP…I’d use it only if it was mandatory…impact resistance is its strength, so it makes sense for a kneeboard deck.
the fact that you can’t really effectively sand down the cloth, clean finish work implies glassing over it or using copious amounts of resin to fair if you don’t lay it down tight and perfect the first time.
search Kevboo SUP if you want to see my build thread.
Kevlar or Aramid cloth is great at resisting stretch or creep. But, it is not resistant to compression. Consequently, it only makes sense to put any kevlar cloth on the bottom of your board to resist buckling. But, kevlar or carbon deck patches don’t really make any sense. You’re relying upon the compressive properties of what ever resin matrix at what ever thickness to resist deck crushing. Not an un-preloaded low stretch fiber cloth.
All VERY good sound advice my friends! However…The customer this is for is completely stuck on the whole Kevlar deck thing. Personally, I would rather go with Carbon fiber, but then again. what do I know. I have no experience with that either! I think I will go with the epoxy lay up over the poly foam stain. My biggest concern with that is how to keep the epoxy from “Pooling” up in the knee wells which are quite deep. Any suggestions would be greatly appreciated! It is the main reason why I was considering glassing with regular Resin.
I do plan on doing a cut lap all the way around the Kevlar lay up and putting at least 6oz of fiberglass over it. More than likely I will put several layers over top…so sanding should be a non issue…I hope. Should be no problem trimming my cutlap since I don’t have to flip the board.
I agree that a Kevlar bottom would make a very bullet proof board, but this is a case where the customer wants what he wants, so That is what I will do for him. It’s what he has on all of his old knee boards, so, there ya go.
Thanks again guys!
I’d pour around the knee wells…brush some resin downward to wet them out and then gently squeegee away…it doesn’t pool if you manage how much resin you lay out in to the concave areas.
please post pictures as you go through the process; keep the camera in the garage!
Hi Leslie. Have you considered using Vinylester resin to do your Kevlar lams. Far superior to poly. Conpatable with poly. Works the same as poly. Only drawback is the colour. It will not be noticable with the Kevlar but if you use it with fibreglass the lams will look like you have added pale green tint. Great for that old school look. I would not recommend using poly with Kevlar. The thing with kevlar is it does not absorb the resin like fibreglass. So all the resin is doing is bonding the Kevlar to the foam and the next laminate. Plus as far as I know poly does not adheare to Kevlar all that well either. platty.
Don’t forget this! It is really important to hide the kevlar from sunlight! Best is to cover it with a layer of paint.
Another thing, kevlar sucks resin like a sponge. Laminate it under vacuum or the board will be heavy.
I have never used Vinylester but I have heard is is stronger than Polyester. I think I will stick with the Epoxy this time around so that the Kevlar will saturate…
Also, A vaccuum is not an option at this time. I need one, but I don’t have one. It is on my “To Do” list which is so long I am beside myself!
As far as progress pictures…I will try to take some…that is unless I might embarass myself too badly. I’m sure if things go wrong, I will be crying about it here and asking for help! Maybe I should just do some artwork on the board to make it look like Kevlar and hope the guy dosen’t notice!
Not knowing how sharp your customer is, but he or she may not really know what they want. Also it may not be worth it to ask and rather easier to just do what they want. So try http://www.acp-composites.com/home.php?cat=252 and order some 1.7 oz. Kevlar. It is very nice stuff, very tight weave (kevlar scissors are a must), and won’t suck resin. Cover it with some S cloth and you have a winner. The 5 oz. is like a sponge and can be expensive.