I need an opinion or two…
Let’s say I build a hollow board with 1/8" wood “skins”…
Advantages and dis-advantages of Carbon Fiber on the inside, compared to Kevlar , compared to Fiberglass…
Thanks in advance…
Paul
Im planning on doing a hollow board at some point in the near future, and planning on using kevlar in the interior for stringers/spars whatever you want to call them. I’ll try to explain why I like this material.
Kevlar and Carbon composites have roughly the same failure strength in tension. The difference between the two is the stiffness, or in engineering terms Young’s modulus. This is a measure of how much a material will strain (stretch) under a certain load. So, Carbon has the highest “stiffness” of the three materials, then kevlar, and glass has the lowest. Under the same load, carbon wont elongate as much as kevlar… BUT kevlar will allow more flex to occur before failure. Since wood is relatively flexible, and will strain a decent amount before it fails, I would say kevlar is most compatible with wood.
BUT, I wouldnt use kevlar unless you are going to vacuum bag it onto your part. It doesnt like to wet out with epoxy in a normal hand layup. Carbon does fine with hand layup, so it would probably yield better results if you arent going to use vacuum bagging. Another apparent problem with kevlar is that you have to keep it out of the sun, as discussed above in this thread. But if you are using it in the interior, I guess that isnt an issue.
Glass is also an option, but you will have a much heavier finished product than if you use kevlar or carbon. The biggest plus with glass is that it sands well once cured in epoxy, carbon and kevlar dont at all.
hope that helped and didnt serve to confuse you.
EDIT
Here is a good point made in the leaf spring thread as to why kevlar is good as a rail material - or any component that serves to transfer deck/bottom load through the thickness of the board = hi shear stress → kevlar is far superior to carbon in shear strength, which is why it is used in ballistic vests.
Took all my bamboo scraps/offcuts and spliced them together to make the first layer
of 2 that will go on to the deck. it didn’t take much time and saved me about 40$ in
materials.
once I got all the surface area I needed, I spliced it to fit within the kevlar tape
then I removed the skin, put down a layer of 4oz cloth, wet it out and put
the bamboo on top
then I wrapped the whole board and slid it in to the bag
the thing was bagged with less than 5hg, but that was sufficient to bring some
excess resin up in to the gaps between the bamboo which left me with a really
nice surface when I pulled it all out this morning.
this will get sanded smoothly, patched as necessary (gaps/voids) and then I
will bag on the second layer of bamboo with 4oz cloth over, lapped around the
rail to the border of the bamboo being bagged on to the bottom.
the bottom layer will get 4oz cut within the kevlar border, then bamboo veneer
that will extend over the kevlar, hiding the wobbly tape and allowing me to
cut a nice smooth line around the edge of the board.
still going to need to paint the rails…looking for assistance from any swayfolk
in the LA area that have access to painting equipment…I don’t have a sprayer
and I’ve never done anything like this before so any experienced volunteers
will be richly rewarded for their help.
durbs. Good insight on Kev, Carb, glass, wood. I make my frames with glass sandwiched between 2 layers of wood. So far I have stayed away from Carb and Kev just because of the expense. Also I am finding that the best woods are the ones with the most flex, you can cut them thinner and have more strenth. I am finding that balsa is not always the best unless you want thicker sandwiches. Ahui hou- Wood_Ogre
Nice work Tyler, I like your use of the scrap materials. As for painting that I think you can get some sort of nozzle for your air compressor for reasonable cheap… not sure though. At what stage in glassing are you going to paint the rails, and are you going to add any fiberglass over the rails?
Vac’d on a skin today with the new relay controlled fridge compressor vac pump (RCFCVP?) and it worked great. After running for four hours the compressor was still cool to the touch, and I didnt blow out the relay either. Maybe I wont need to buy a pump soon after all… worked much better than I had anticipated.
Some bamboo/eps composites with various rail materials (kevlar, carbon ,cedar)
so hot!
these boards are untouchable.
The Kevlar will protect the rails - but you really need a Kevlar vest, because people will probably be shooting at you as well as the board (boat). Unfortunately while it has great impact resistance, Kevlar won’t protect you from ridicule.
Quote:
KevBoo - GOT IT, wow I am a loser…
…
I think I’ve got it: kevlar bamboo SUP = KevBoo SUP
do I get a prize like what 9N78W got on the hull V egg thread?
Quote:
I need an opinion or two…
Let’s say I build a hollow board with 1/8" wood “skins”…
Advantages and dis-advantages of Carbon Fiber on the inside, compared to Kevlar , compared to Fiberglass…
…
ok, I’ll have a go at answering your challenge question Paul, I’m really just theorising here as I don’t have direct experience with these materials.
Carbon outperforms kevlar in everything except impact resistance and fracturing while bending. However your boards don’t heel dent so withstanding bending is not an issue. Your question is about the inner laminate only so this will be protected by the wood, over the wood you laminate glass and epoxy, so the inner laminate is well protected against impact. Therefore you don’t need kevlar.
I’ve been able to see your boards and IIRC you have already been using carbon, plus I’ve been paying attention to the “what you working on thread” and it looks like glass has been tried too. So I think the best choice is between these two.
Quote:
Some bamboo/eps composites with various rail materials (kevlar, carbon ,cedar)[/img]
Standing ovation! Looking at that board has me seeing stnad up barrels! Pray for surf.
Does Moonlight do any of your eps/epoxy work? If not, who ? Looks flawless.
I believe Allan glasses these himself but I may be mistaken. Either way his shapes and use of materials are simply amazing. All those boards are super light too. Last year when I was working on #1 Allan gave me some advice/help and showed me one of his boards in person, I aspire to build boards that look 1/10th as good.
Sorry if I sort of hijacked the thread.
These types of construction (and there are many, many more types) are available to any motivated and imaginative home-builder. Whether its cost-effective or not is another story, but for for people who want to have fun and experiment, there’s a whole world of possibilities out there. And it doesn’t take much in the way of special tools or equipment. A vacuum-pump is the only specialized item, most of the rest can be had at the hardware store, any surfboard supply house, and from online sources. Getting fancier, its pretty easy to rig up a simple curing oven, which can greatly improve the lamination.
Quote:
Quote:Standing ovation! Looking at that board has me seeing stnad up barrels! Pray for surf.
Does Moonlight do any of your eps/epoxy work? If not, who ? Looks flawless.
Thanks!
Maybe in the future I’ll send them out for glassing after the skins are bagged on and prepped. Up to now, though, I’ve been doing them all myself, start to finish. Partly out of curiosity to see what it was like to do, as well as to allow me to break it down- time-wise- and get a realistic cost in labor, and mostly to be able to feel what’s going on with the boards as they move through the process, and so to get feedback to make adjustments to the shapes as well as to the process(es).
got the first layer (scraps) on the deck…this will get another layer of bamboo
over it fit cleanly relative to outline.
got the single layer fit and bagged to the bottom.
started painting
but then I noticed something funny about my test panel…
krylon h2o over bamboo with an epoxy laminate over.
was trying to figure out the best rattle can product to use to put some color over the kevlar.
was not sanded prior to lam…
after you spray painted did you sand at all?
Quote:
Some bamboo/eps composites with various rail materials (kevlar, carbon ,cedar)
Allan, The only thing about these boards are WOW!!! UNREAL job. Mahalo,Larry
you don’t read so good, college boy…
hello Afoaf, I’m assuming that you haven’t yet done the final glass lam? if so then thats good you did a peel test before you got too far. Even with sanding the paint I’d be questioning the ability of further lams to stick to it. My suggestion is to sand off all the paint then lam over that. An easy solution to protect the kevlar from UV would be to paint over the epoxy gloss coat on the rails only. This would be prone to scratching but at least you will preserve the integrity of the kevlar lam to glass lam bond.
A question for an epoxy expert (depending on the epoxy you use) would be how much UV protection does the clear lam give - maybe that is sufficient and no paint needed in which case the kevlar weave will look rather cool?
these are just my thoughts, there are many possible solutions.