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Feckin Eejit!
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Discussion Starter · #1 ·
So I asked this in chat:
[10:33 AM] Ahks: So, if you werent worried about structural integrity and cosmetics, could you lay up cf just like fiberglass?

Mike responded:
[11:50 AM] MikeGyver: Cf lays just like glass.....get a thread started on this

What prompted this was
https://www.youtube.com/watch?v=BJFSXIP6Vw8&list=PL1B713C2239BF7D60&index=1&hd=1

http://www.bxrmotors.com/

What I'm looking at doing is using his idea to build some simple bits for my project. Out of carbon instead of glass.

My process will be something like:
1. Rough design in mspaint
Heres mine.

The tail is a blatent rip off of the ronin bikes from the47.com but I don't care. Those bikes are sexy as fuck and that tail fits my style.
2. Model it out of cardboard (mainly because I have a glut of the shit due to my current job)
3. Build the wooden frame thing like the guy in the video did (mine will probably be cardboard, glued together... I really have a shitload of small worthless boxes. And my model doesn't need near the size of his)
4. Add foam core
5. Shape, Sanding, grinding, electric carving knife, etc. I think one of the tools the guy was using to model the first BXR was a small steel cable stretched taught between 2 sticks, I'm oversimplifying, but not by much.
6. Tape, this is HVAC foil tape. Apparently the shit has a very thin cello-tape layer or something that allows the part to easily "release" from it or the foil from the thin layer... Who knew.
7. Lay cloth, wet it down with resin, roll it out and try to fight off the bubbles with heat.
I think you wait a day for it harden for the first layer so have a firm base with which to work.
8. Sand the surface dull so the next layer bonds well
9. Lay cloth, resin, roll/heat, wait till tacky NOT dry. You want it just barely dry enough to not come off when you touch it. Any wetter it's a mess to work with, any drier and your layers don't bond right (I think... wtf do I know, I've never done it :D )
10. Repeat step 9 for desired thickness. I'm guessing some non structural bits like I'm looking at doing only need like 3 layers. More if I need hardware attached, and mounting tabs, etc will need a bit more as well. If I get around to building my fender, I'll probably need like 5 for the main fender and maybe 7 for support bits. Anyone reading this, please correct me if you know better.
11. At this point, wait for it to cure.
12. Dance around your workshop like nobody is watching because you potentially just used $75 in materials to make the same type of part that Ducati 748 owners pay $400 for :rock:

13. At this point you can either sand and paint or sand, wet sand, rub it out, polish it.


A question for any knowledgeable person reading.
Does laying the layers in different directions increase the strength in this application?

Any input? Questions?

Edit:
When I actually get moving on this I will take pictures. I have some preliminary design ideas that I'm tossing around with a friend. And I think I have to chop my subbie before I build anything for it. :p
 

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30,379 Posts
On trying to do this on my phone. ..


1. Looks good.

2. making it out of a block of foam may be easier since it looks small.
3. Whatever works
4. Sure
5. I used a cheese grater thing and a serrated bread knife. I couldn't get the hot wire to work. Not sure about the HVAC tape thing.
7. Yup.
8. Yup
9. I go non stop until I have my desired layers. I don't wait for anything to tack. Hell, I'd skip step 8.
10. Depending on your fabric, 3 maybe too thin. Maybe 5 for the seat assembly.
11. Sure
12. Ducati guys pay for prepeg autoclave parts.

13. Sure, rub one out.

"Does laying the layers in different directions increase the strength in this application?"

Yes it does.

"Any input? Questions?"

Yes:
Use epoxy, not polyester. Practice with fiberglass first! Then practice with fiberglass second. Then practice on carbon twice.

Consider making a mold and pulling a quality smooth part from that. You are spending the money on carbon, why not do it right?

Read the directions for your epoxy and then read them again.

Don't get raped buying shitty carbon.
Take your time. You won't the first time, hence the fiberglass for practice.

Use a rotary cutter and a self healing mat to cut your fabric.

I'm sure there is more but I'm going to bed.
 

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Ridin Dirty
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377 Posts
You really can't lay carbon like fiberglass Matt, is will not lay flat.
The whole point of a carbon part is to create a certain epoxy/ resin ratio that is obtained by vacuum.
Otherwise, the part will not be uniform in thickness, and the epoxy weighs to much.
For the thickness, often two different materials are used, top and bottom layer is made with a tighter, thinner weave, the buildup layers are thicker, and the weave is loose and has a less attractive weave.
Pva release agent is what I would suggest, it's worth it ..among a few others where carbon fabs are sold..
It's easy to vacuum a part, just takes a few items..all the unneeded resins are sucked out, and the shape ends up uniform and compressed.
 

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Feckin Eejit!
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Discussion Starter · #5 ·
It wont lay flat? Do you mean if I wrap it around a part it'll try to straighten out as if the sheet is held under tension?

At this point I'm probably going to do a glass mold, at least as practice. I've got a huge roll of wide glass tape that would be good to practice with. And if I make my model the right size then the glass practice piece would be the right size for a mold.

I just need time now. :p
 

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not sure what is meant by CF not laying flat. Unless he is talking about thicker mil cf.
A mold will be best, but you can survive with a foam buck. I say this, because unless you are an absolute perfectionist, a mold will cause more trouble.
trade me your 955 fairings and Ill make your parts :thumbsup:
 

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Ridin Dirty
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377 Posts
When you make a multiple layer part, it can take around 10 layers
For a part, each layer will pull up on the lower layer, making thick spots around corners or voids between layers I might try 3 layers without vacuum, but as much as the stuff cost, I would prefer to do it right.

The people that make parts with carbon for a living have access to carbon that is pre-pregnated.
Kept at about 50degrees f, it has pre-mixed epoxy in the fabric, and will not start to harden until over 80f
This gives them a huge advantage as each layer they work with has its own timeline for sorting out.
You have to work really fast to sort out more than 6 layers with the same batch of epoxy..
Vacuuming is the only way to wrap edges also..
 

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hate us cuz they ainus
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Yea I'm with mike. But I hafta ask, if it not for strength or cosmetics why do you wanna do it? It sounds to me like your just gonna end up with black fiberglass.
 

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Feckin Eejit!
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Discussion Starter · #12 ·
I think I see the pattern... lemme see if it's sunk into my thick skull.

So most of the weight comes from whatever resin is being used? The difference in carbon vs glass isn't enough that simply replacing the fiber with carbon would be an effective weight loss of a part if they are constructed identically. The lightness of CF parts comes from the fact that carbon parts, when made well, have excellent resin impregnation and lower resin mass as compared to an equal fiberglass part?

Thus, making a part like I'm talking about by laying the part up like in the videos I linked would...
just gonna end up with black fiberglass.
 

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The same is true with fiberglass. Less resin is a lighter and stronger part.

Carbon is lighter than glass, but in your instance I'd go with glass with black pigment on the resin then skin it with carbon. Unless you are going all out with vacuum bagging or vacuum infusion then it really isn't worth trying to do wet layup of carbon to achieve weight savings.
 

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trogdor, the burninator
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392 Posts
i dont know wtf dude is talking about but im not trying to argue. carbon will lay flat, curved, compound curve... it can even go just fine around corners, and can be strong even without vacuum... no, its not as ideal, and yes you have to take extra care to get a better product... correct that your ratio will be heavier on the epoxy, but it will still be strong and lighter than fiberglass

i think this forum has a general "make it work" attitude so i'm not going to tell you that you cant do it but will share my actual experience not just conceptual "no-no's"

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first carbon piece was a tiny tail fairing like you. i sculpted my desired shape out of clay and baked it.



i used fiberglass for the first 2 layers and carbon on top (but same epoxy resin for all of it)



you can see in the above pic that i wrapped the corner just fine, just wait til its tacky and keep pushing it down. people also tape down the edgers. for the "point" at the end i just used a clothespin.

came out good but not smooth because it wasn't made from a mold (like MikeGyver iwas referring to)

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here is an intake shroud i made, just putting pics to show the edges, pic one they aren't wrapped.. waiting a bit for the epoxy to tack up. pic 2 shows them wrapped around nice and smooth with just keep pushing everything down with a brush





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timelapse a bunch of trial and error later, i'm working on another bike and i made a mold for a carbon seat.





its super smooth and strong, about 5/6 layers of carbon fiber and i can stand on it just fine

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so to answer your specific questions I think everything looks good but i would recommend using clay instead of foam. good luck!
 

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trogdor, the burninator
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392 Posts
The same is true with fiberglass. Less resin is a lighter and stronger part.

Carbon is lighter than glass, but in your instance I'd go with glass with black pigment on the resin then skin it with carbon. Unless you are going all out with vacuum bagging or vacuum infusion then it really isn't worth trying to do wet layup of carbon to achieve weight savings.
yes. this ^
 

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Feckin Eejit!
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Discussion Starter · #18 ·
The in progress pics with annotation is EXTREMELY helpful. Thanks a ton.

I think in order to get the part "right the first time", or as right as I can, I'm going to make my model like in the Bailey BXR vids. Make it full size. Then lay the part in glass as clean as I can so I can turn it into a mold.

While I'm doing all that I'll see if I can swing some of the bagging hardware. I've seen a few methods that are pretty cheap.

bored at work. really like the look of your bike with this tail

And thanks for this too :D Added it to my imgur album for this project.
 

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trogdor, the burninator
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I'm going to make my model like in the Bailey BXR vids. Make it full size. Then lay the part in glass as clean as I can so I can turn it into a mold.

While I'm doing all that I'll see if I can swing some of the bagging hardware. I've seen a few methods that are pretty cheap.
Sounds great except you dont need to fiberglass the clay "plug" you can go directly on the clay like i did or use tinfoil or tape... like this video:

https://www.youtube.com/watch?v=UHdJYL7iiRk

also... cheap vacuum bagging? let me know what secrets you have! :excellent:
 

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Refridgerator pump is a vacuum pump after a trip to lowes for some fittings. works well too
 
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