Let's build a carbon fender!

[tygaboy]

really? the pre-impregnated stuff turns out stronger??

It should in that it is the EXACTLY right fabric to epoxy ratio. Combine that with the fancier epoxies, autoclave and specifically controlled cure cycles (ramp to temp over a certain time period, hold at temp for x time, ramp down) that stuff is the best it can be.
All that said, you're talking way overkill issues for the stuff we've made. If you're building an F1 car chassis or other structural component, this is the only acceptable approach. State of the art and all that...

 

[EASTcoastRIDAH]

yeah pre-preg is cool stuff...not only is it stronger and look better but it also increases production rate for factories

the hard part is that not only does it have to be heated but heated under pressure (mechanical or atmospheric) it also can only be bought in large quantities (very expensive) and has to be stored below freezing since it will cure at room temp

the picture from Dreher in NH where i fabricated the oars that u see in the picture, the boat and the rigger is also 100% carbon

 

[GearSlammer]

i was watching an episode of RIDES on TLC where these guys were building show cars for big shows like SEMA and CES. one guy was building a scion tc and used the pre-preg stuff. i honestly thought it would be weaker since it didnt seem like they had too much epoxy.

 

[com3]

//awaits final product.

 

[Hooli]

//awaits final product.

+1

 

[ZXR400SP]

I had a friend doing aerospace work, shuttle stuff, satellites, etc.... He gave a a piece from a layup for a 747 nose that didn't come out quite right. It took me half a dozen jigsaw blades to cut a dash plate for my race tach. It was as hard or harder than steel and stronger too.

Their autoclave is bigger than my house. I used to use an autoclave for sterilization at the lab where I used to work. It would be just about the right size for a fender.

 

[tygaboy]

I had a friend doing aerospace work, shuttle stuff, satellites, etc.... He gave a a piece from a layup for a 747 nose that didn't come out quite right. It took me half a dozen jigsaw blades to cut a dash plate for my race tach. It was as hard or harder than steel and stronger too.

Their autoclave is bigger than my house. I used to use an autoclave for sterilization at the lab where I used to work. It would be just about the right size for a fender.

So...let's find someone who is still in the aerospace biz! All we need is access to some of their 'scrap' prepreg and some 'after hours' access to the autoclave! I mean, how big a deal could that be?
And yes, I know I'd have to build all new molds that would stand up to this method. Good thing I save all my plugs!

 

[Harsh]

We use some prepeg where we teach composite repair. We don't have an autoclave perse (sp) (thinking tattoo stuff here), but when we vaccuum items we can also apply heat to them. I am going to go back and read through the tank thread and see about making a mold for a carbon hugger. I could use my current hugger as a baseline and modify it as I want. Too bad I am on the opposite coast we could probably help each other out.

 

[auntiebling]

sooo, i think this is my longest post ever... sorry about that i get dhiarreah of the fingers when i actually KNOW something relevant

Autoclaves are essentially specialized curing ovens. The cool (hot?) part is that with access to something like this, we could use prepreg carbon fiber that is impregnated with a different sort of epoxy - one that needs the elevated temps to cure. You end up using a specific cure cycle and get stronger, lighter parts.
Super fancy, super neato, super expensive...

an autoclave isn't mandatory for prepreg, only the elevated temp, typically that is only about 400F max, and bagging so the material conforms to the shape (I believe you already can do this?). at work all of the CF parts are prepreg and most of them cure in ovens with only vacuum bagging. the nice thing about autoclaves is getting better compaction from a laminate or helping the fibers conform to complex gemoetry such as the recessed mounting screw.

It should in that it is the EXACTLY right fabric to epoxy ratio.....

not always, but it is the industry standard for the most part. we use prepreg that is intentionally resin rich so we have to bleed off some during cure. to some extent you get more control over fiber volume, but i'm not convinced it's worth the effort...

yeah pre-preg is cool stuff...not only is it stronger and look better but it also increases production rate for factories

the hard part is that not only does it have to be heated but heated under pressure (mechanical or atmospheric) it also can only be bought in large quantities (very expensive) and has to be stored below freezing since it will cure at room temp

prepreg isn't inherently stronger than dry fabric. in fact you could get the EXACT same fiber without the resin in it and with care and practice make a part that is indistinguishable in any way from one made from prepreg. the increased production rate would come from the elevated cure temps accelerating the chemical reactions in the part, not the fact that the material already has resin in it. prepreg can be a real PITA to deal with when it gets tacky, like handling a sticker that is sticky on both sides. a RTM (resin transfer molding) process would be just as fast and not use prepreg

there is no way around the low storage temps and even then it has a finite life span. however even after the material is “out of date” you can still use it, it’ll just be harder to get to conform to a mold as the resin is partially cured.

i was watching an episode of RIDES on TLC where these guys were building show cars for big shows like SEMA and CES. one guy was building a scion tc and used the pre-preg stuff. i honestly thought it would be weaker since it didnt seem like they had too much epoxy.

Resin content affects strength in two ways:
- not enough resin and the plies won’t stick together, making impact resistance an issue as well as the ability to post machine the part (mounting holes, cleaning up edges etc) the laminate will delaminate instead of just behave nicely.
- Too much resin and the part gets heavy, and the actual strength goes down as the effective modulus goes down

I had a friend doing aerospace work, shuttle stuff, satellites, etc.... He gave a a piece from a layup for a 747 nose that didn't come out quite right. It took me half a dozen jigsaw blades to cut a dash plate for my race tach. It was as hard or harder than steel and stronger too.

this kind of strength has nothing at all to do with an autoclave cure. abrasion resistance is dominated by the fiber used in the layup. as i stated before, you could get the same fiber dry from the manufacturer (though you won't like the price tag)

So...let's find someone who is still in the aerospace biz! All we need is access to some of their 'scrap' prepreg and some 'after hours' access to the autoclave! I mean, how big a deal could that be?
And yes, I know I'd have to build all new molds that would stand up to this method. Good thing I save all my plugs!

you know it already, but there isn't much usable scrap in the aerospace biz or i'd be all over it already....

anyway, if you envelop bag your molds they might do better than you think in an oven/autoclave environment. i wouldn't take them all the way to 140psi or the really agressive cures but they might work with a little modification.

i think you're definitely capable of stepping up to an oven cure with some research, a craigslist oven, and a timer. maybe find one of these nerdy barfers to build a temperature controller for it in exchange for some kind of parts?

one thing to watch out for is the exothermic reaction of the cure process. when you put it in an oven the reaction can actually drive the part temp past ideal cure temps and the control system can't do a damn thing about it, unless you have active cooling too.... there is a reason that autoclaves have an inert atmosphere

 

[ZXR400SP]

sooo, i think this is my longest post ever... sorry about that i get dhiarreah of the fingers when i actually KNOW something relevant

this kind of strength has nothing at all to do with an autoclave cure. abrasion resistance is dominated by the fiber used in the layup. as i stated before, you could get the same fiber dry from the manufacturer (though you won't like the price tag)

Yea my buddy told me about the cost of the fabric. They acturally laid the prepreg for the 747 nose 3X. The first two as laid out by the engineers, the last time they did it way the fabricators thought it should work, and it did. A couple million dollars lost in the first two tries. He quit and moved to the midwest or I'd have a few small parts made by now.

 

[machete]

So I'm curious if you will have another workshop for fabricating a carbon fender.

I have the fender below that I would like to make into carbon fiber. sure, I could do a long search on ebay and just buy it. but how cool to have your own fabricated stuff? right?

If you ever feel like making a plug and fender for this style of Ducati front Fender (pre-1999 M900 Ducati) I would be more than happy to donate this fender for the cause.

allright, enough beggin'.

very cool stuff on your SV fender. any new photos.

antibling: dude, we should talk CF, I never knew you were so smart.

 

[auntiebling]

Yea my buddy told me about the cost of the fabric. They acturally laid the prepreg for the 747 nose 3X. The first two as laid out by the engineers, the last time they did it way the fabricators thought it should work, and it did. A couple million dollars lost in the first two tries. He quit and moved to the midwest or I'd have a few small parts made by now.

as much as i tell the production guys what to do regarding ply orientation, seams etc etc i follow their advice a bunch too. it's hard to beat 20+ years of actually working the material

antibling: dude, we should talk CF, I never knew you were so smart.

i don't know the garage DIY stuff, just low volume production stuff...

follow tygaboy's lead, he's got pretty damn good writeups. i can help you with vendors if you want to go into production i'll be happy to bullshit anytime though

 

[machete]

follow tygaboy's lead, he's got pretty damn good writeups. i can help you with vendors if you want to go into production i'll be happy to bullshit anytime though

it was just an excuse to drink fancy beers with you dude.

I will follow tygaboys instructions first.

 

[auntiebling]

i SAID i'd be happy to bullshit anytime. gosh!

i'm going to rock bottom tomorrow night, fly your arse up here and we'll have a few.

 

[tygaboy]

If you ever feel like making a plug and fender for this style of Ducati front Fender (pre-1999 M900 Ducati) I would be more than happy to donate this fender for the cause.
[/B]

Haven't I convinced you to give it a try on your own? It's not that big a deal. Start with something simple and build a base of knowledge.
I may do anouther seminar but at this point it wouldn't be until springtime. So come on - have a go and post what you're doing. There is no shortage of BARF "experts" who will chime in and offer opinions/guidance along the way.

 

[RideToLive600RR]

Start with fiberglass since it is cheaper and will give you a good idea of what you need to do.

 

[machete]

Haven't I convinced you to give it a try on your own? It's not that big a deal. Start with something simple and build a base of knowledge.
I may do anouther seminar but at this point it wouldn't be until springtime. So come on - have a go and post what you're doing. There is no shortage of BARF "experts" who will chime in and offer opinions/guidance along the way.

I hear ya man.

just thought I'd offer it....just in case.

I thought about starting with a small "dash" for the SV. just something to hold my toggle switches, some indicator lites. i've got a mock up with a small piece of sheet metal.

I've been browsing all the "how to" posts and will get back to you.

awesome work, by the way. and that tank is SWEET!!

 

[DougZ]

OK, so I broke down and joined this board to be able to reply to these threads of your's.

With that said, I do have a question or two. Also, I appreciated your responses to my questions on the SVR site.

With a project like a fender, I have noticed from google images of the fenders online, made of either CF or Kevlar, that you can definately see the cuts in the outside layer of fabric, in the final product. I know you did that with the CF tank project, to get the fabric to lay the way you wanted.

Now, in making the final fender itself, do you make the whole fender with one piece of fabric with cuts in it, or lay up seperate pieces for say the fender itself and the legs seperately? I know you use other glass for the backing layers, so the question above is really only refering the outer most, "show" layer of material.

If you do do seperate lay ups for the legs vs the fender itself, I guess you bond them as some secondary step?

Lastly, once you make a certain part, how do you go about cutting it so the edges look as good as they do?

Lastly II...LOL...how do you know when to use the vacuum bag set up vs when to use the roller technique, like you did with the making of the tank mounts?

 

[tygaboy]

OK, so I broke down and joined this board to be able to reply to these threads of your's.

With that said, I do have a question or two. Also, I appreciated your responses to my questions on the SVR site.

With a project like a fender, I have noticed from google images of the fenders online, made of either CF or Kevlar, that you can definately see the cuts in the outside layer of fabric, in the final product. I know you did that with the CF tank project, to get the fabric to lay the way you wanted.

Now, in making the final fender itself, do you make the whole fender with one piece of fabric with cuts in it, or lay up seperate pieces for say the fender itself and the legs seperately? I know you use other glass for the backing layers, so the question above is really only refering the outer most, "show" layer of material.

If you do do seperate lay ups for the legs vs the fender itself, I guess you bond them as some secondary step?

Lastly, once you make a certain part, how do you go about cutting it so the edges look as good as they do?

Lastly II...LOL...how do you know when to use the vacuum bag set up vs when to use the roller technique, like you did with the making of the tank mounts?

Welcome to BARF and thanks for the questions.
As you've correcly said, the different pieces are used to address the drapability issue. And you don't lay up each piece (fender vs legs) in a separate process. You just lay in each picece, wet it out and lay in the next piece. The entire layup of seperate pieces is done all at once. A far better final part results when the layup is done all at once and is consolidated in a single cure. "Secondary bonding", as it's called, is not a bad thing and is required for things like the gas tank, but if it can be avoided, I like to avoid it. Plus, a fender is a 'one layup' kind of part, so no problem there.

As to finishing the edges, you can either design the part to wrap a bit near the edge so the actual edge is hidden or at least visually 'softened'. It can change the look of the part, too. And look back at the tank thread - I rough trim with a pair of metal shears and then hit the edge with a Dremel and/or sand paper - it comes out just fine. And I sometimes run a Sharpie down the edge just to blacken it up a bit.

The vacuum bag vs roller is all about how much a combination of variables matter: Overall strength requirement, ease of bagging, visibility of the part, etc. Vacuum bagging always gets the best epoxy/fabric ratio and therefore, the best strength. Not to mention it also tends to result in the best finish since it forces the composite firmly into the mold and helps eliminate bridging, air bubbles, pin holes in the surface, etc. But it's a bunch more work, too. Not sure I'll bag the fender or not...I'll post as I get to that point in the process.

Hope that helps answer your questions.

 

[#1Freak]

i have a few spools of both kevlar and carbon fiber thread, high quality stuff for the production of rocket cases. but it is not woven. is this of use to anybody?

Brian