Kevlar Cloth?

[Brushless55]

has anyone used Kevlar cloth insted of Carbon cloth in side their hulls?

http://www.jamestowndistributors.com/userportal/show_product.do?pid=4264&PTECH#

The look could be killer!

[RandyatBBY]

I have found it is good sandwiched between FG and CF. By it self a little flexible. great for armor, special needs to cut. I re sharpen my scissors to cut. and do not want the material on the cut line of a layup. I use 1 to 3 Oz material.

[j.m.]

You can get twill weave carbon...

But most kevlar isn't going to look that good once it's saturated with epoxy. Usually a much darker color:

http://www.f3k.nl/tl_files/Modellen/xp5.jpg

[Gerwin Brommer]

Kevlar is great.
Much stronger than carboncloth.
Make sure you use enough epoxy. Every fiber
that is not filled with epoxy will absorb water.

[ED66677]

I think Kevlar is heavier and more difficult to work than carbon.

[Brushless55]

Kevlar is great.
Much stronger than carboncloth.
Make sure you use enough epoxy. Every fiber
that is not filled with epoxy will absorb water.

That's what I've read, that it is stronger and all so lighter than some CF..
that's one reason it is used in kayaks

I like the color and wanted to try something different than the norm for these boats..
BUT, they do have a Carbon/Blue weave that would look sick with my Titan 29 that's on its way with the Blue hardware!
what to do?

[befu]

I shouldn't even post this......

I think Kevlar is heavier and more difficult to work than carbon.

Yep, 5 oz carbon is lighter than 5 oz kevlar......

Ok, seriously now. Read up on them, they both have thier place. I really like kevlar. In my light layups, I use a thin layer of glass, then light carbon, a medium kevlar followed by more carbon. The kevlar is tougher, the carbon stiffer. Makes a sandwich layup.

Take carbon and bend it over your fingernail, you can break it. Lay up carbon in a light layer and you can crack that. Try it with kevlar or lay up kevlar and try to break it. Good luck. You can crush the resin out of it and fold it, but it doesn't break.

They both have thier place, benefits and shortfalls. Kevlar is VERY tough stuff, Carbon is very strong stuff. kevlar is fantastic, but everyone wants the sexy carbon!

Most people use carbon because a proper layup can be stiffer and lighter. But most people also use way to much resin, so strength per weight is lost. Either will work.

Normally I do not post recommendations like this, just causes an argument so go with the sexy carbon. That is what all the experts want to see. Is the epoxy you are using compatible with the binder used on the cloth? 90%+ of the people do not even realize that there is 3 parts to your composite, but don't bother to bring that up. Is your hull epoxy or polyester? Was wax used in the layup? Was peal ply used? Smooth surface or roughed? Kevlar works with polyester, also offers a chemical bond if not waxed or sanded, epoxy is a mechanical bond when you add more. Basic question that you could write a book about.

Go with the sexy, helps resale!

Brian

[Brushless55]

Thanks Brian!

I do like the sound of a Kevlar FE!

[DISAR]

You can also use the carbon-kevlar which can be seen in some H&M hulls. It combines both materials' properties I think

http://www.jamestowndistributors.com/userportal/show_product.do?pid=4297&familyName=Carbon+Kevlar+Hybrid+Cloth

[Brushless55]

You can also use the carbon-kevlar which can be seen in some H&M hulls. It combines both materials' properties I think
http://www.jamestowndistributors.com...r+Hybrid+Cloth

looks nice man!
what kind of epoxy did you use? It looks like a matt fininsh

[RandyatBBY]

Yep, 5 oz carbon is lighter than 5 oz kevlar......

Ok, seriously now. Read up on them, they both have thier place. I really like kevlar. In my light layups, I use a thin layer of glass, then light carbon, a medium kevlar followed by more carbon. The kevlar is tougher, the carbon stiffer. Makes a sandwich layup.

Take carbon and bend it over your fingernail, you can break it. Lay up carbon in a light layer and you can crack that. Try it with kevlar or lay up kevlar and try to break it. Good luck. You can crush the resin out of it and fold it, but it doesn't break.

They both have thier place, benefits and shortfalls. Kevlar is VERY tough stuff, Carbon is very strong stuff. kevlar is fantastic, but everyone wants the sexy carbon!

Most people use carbon because a proper layup can be stiffer and lighter. But most people also use way to much resin, so strength per weight is lost. Either will work.

Normally I do not post recommendations like this, just causes an argument so go with the sexy carbon. That is what all the experts want to see. Is the epoxy you are using compatible with the binder used on the cloth? 90%+ of the people do not even realize that there is 3 parts to your composite, but don't bother to bring that up. Is your hull epoxy or polyester? Was wax used in the layup? Was peal ply used? Smooth surface or roughed? Kevlar works with polyester, also offers a chemical bond if not waxed or sanded, epoxy is a mechanical bond when you add more. Basic question that you could write a book about.

Go with the sexy, helps resale!

Brian

I have to agree with all you say, But I do have a question. The wax is used as a sealer to promote the curing of the Polyester, what do they use with out it?

[befu]

wax

Nothing added. The outer layer of the polyester does not cure. Have you ever noticed on a polyester hull or even bondo, that the outer layer stays a bit tacky? Even on Bondo, when you start sanding, it will gum up the sand paper quickly. That is uncured Bondo. Once you remove that, it sands much better.

One of the things that this does is help the next layer stick. Since thier is some non-fully cured resin present, when it is coated, it will then cure. This allows the chemical bonding to take place throughout the entire layup.

It is one reason I really like doing light layups with polyester resin using kevlar and carbon mat, both of which have binders that are compatible with polyester. Thier must be some reason why carbon cloth does not use a polyester resin compatible binder, but I never looked into it.

Another way to get rid of this uncured layer but promote adhesion like epoxy, is to use peel ply. After it is cured and you remove the peel ply, you are left with a rough fully cured base.

[RandyatBBY]

Nothing added. The outer layer of the polyester does not cure. Have you ever noticed on a polyester hull or even bondo, that the outer layer stays a bit tacky? Even on Bondo, when you start sanding, it will gum up the sand paper quickly. That is uncured Bondo. Once you remove that, it sands much better.

One of the things that this does is help the next layer stick. Since thier is some non-fully cured resin present, when it is coated, it will then cure. This allows the chemical bonding to take place throughout the entire layup.

It is one reason I really like doing light layups with polyester resin using kevlar and carbon mat, both of which have binders that are compatible with polyester. Thier must be some reason why carbon cloth does not use a polyester resin compatible binder, but I never looked into it.

Another way to get rid of this uncured layer but promote adhesion like epoxy, is to use peel ply. After it is cured and you remove the peel ply, you are left with a rough fully cured base.

I do not use Pollyester I would loose my lease on my shop. So that is why I asked. To put it in laymans terms use lay up resin and not top coat.

I do work with Epoxy a lot and I do use peel ply and I still think it is a good idea to roughen the surface whare the peal ply was when adding another layer. You are right it, discussion can go on for ever. (or write a book)

[Gerwin Brommer]

@ brushless 55 :

That's no matt finish, that's just using just enough epoxy.
A shiny surface means too much resin has been used.

[befu]

cloth to resin

Cloth to resin. This is another sore point with many people, how much resin they use. A composite is just that, made up of more than one thing. If you use carbon and epoxy, the resulting strength is a combination of both materials.

First a note on resins:
Now you hear people talk about how much better epoxy is than polyester. Made from real glass, not polyester. Well, neither is glass, they are both resins. Glass is a form of reinforcement. Polyester is usually in the low 9,000 psi tensile strength (TS) range. If I remember, it is 9200 to 9300, depending on quality, where epoxy is 9,800-10,000 psi TS? Epoxy is only about 10% stronger. Not bad and it is great stuff, but it is not like polyester is garbage! Epoxy does allow you to use carbon cloth as it is compatible with the binders in the cloth, this is the big payoff.
I am not sure if it is all epoxies though. Does anyone know the answer to this? Your laminating resins are formulated to work with the binder in the reinforcement. I have no idea if the cheaper epoxies sold under hobby use will work with the binder. Sure, it will set up and get hard, but it is not properly bonded together. This is complicated chemistry that I do not understand, that is for the manufacturers to know. Glass mats should never be used with epoxy, incompatible binders.

Composites:
Let’s say you are using carbon which is 170,000 psi TS. And you lay it up with epoxy which is 9,800 psi TS. People see that 170,000 and go WOW!
Carbon layups should be about 40% resin to 60% carbon by weight. Let’s go a little heavy on the resin and use 50/50. 9800 for epoxy, and 170,000 for carbon gets you a composite strength of 90,000 psi TS. (you have ½ epoxy, ½ carbon) Ever see those layups people do? Nice and shiny, like the resin was smoothed over the carbon! I would say people are using 3 to 5 times the epoxy to the carbon, which puts your strength down to 50,000 to 36,000 psi TS. Hmm, where did that sexy 170,000 go?
Think about this, if you use a 17” x 17” pc of 5 oz carbon to reinforce your cat, that cloth at 5 oz/ sq. yard should weigh in at 1.1 oz. That means you should use 1.1 oz of resin to saturate that cloth! How much resin have some people used in their boats? If you did 5 oz of resin resulting in a 5:1 ratio, that means you could have put down 3 properly saturated layers of carbon, or even two layers with a resin content of 67%!
Now, someone uses Kevlar at 49,000 psi TS and polyester at 9,000 psi TS and does a proper layup using 1:1 cloth to resin, they end up with a layup that has about 30,000 psi TS. Still below the wet carbon layup, I will give you that. But if the original hull is polyester, and it is unwaxed, it will make a VERY strong layup taking a lower skill level to pull it off. This used to be of great benefit due to cost. Well, lets look at that now….

Now cost.
Gotta admit, much of my thunder from above is gone when you look at modern pricing. OK, when I got into this carbon was pricey, about $50 a yard. If you go to the major supply houses, it is still in that range. Kevlar used to be much cheaper. I would buy a partial roll that was “seconds”. What that meant was that a strand in the fabric got tweaked or pulled so it wasn’t a perfect weave. Anyone ever try to cut Kevlar and see what it looks like when you’re done cutting it? It was perfect for me and I think I used to buy it for like $10 a yard. Built quite a few gas and scale warship hulls from that stuff in the past.
Now days, with Ebay and end of cuts for carbon, I do not think the cost difference is their anymore, or as great. I have to admit that I am kind of shocked at what I found on ebay. It seems you can find better deals on small pieces of carbon than you can on Kevlar. Hmm, maybe I need to go sexy…..
OK, seriously, sorry for putting that image in your mind. If you can find a deal, go for it. But two major things. First, do NOT use too much resin. And use a good resin. Two places that I know of and have used, is US composites and Fibreglast, both great places with good products. Second, do not discount polyester and Kevlar. Polyester on a polyester hull with carbon mat and Kevlar cloth can work fantastic. I am looking at making a little mystic cat at 20” this winter, I think I will start watching Ebay for some bargains.
Oh, just to add. Try multiple layers of lighter fabrics also. With the high strength of carbon, try a 5 oz layer of Kevlar topped with a 2 oz layer of carbon. Get the strength as well as the impact resistance.
Good luck, do your research and do not be afraid to step outside of the “sexy” box!

Brian