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Discussion Starter #1
I am contemplating fabricating a new fuel tank for my bike from scratch. I intend to use fiberglass (maybe w/ an outer layer of carbon fiber) since I do not have the equipment or knowlege for working with sheet metal.

Does anyone have any advice or links to proceedures for doing this? I am already familiar with the absolute basics of fiberglass work; I am looking for some more advanced stuff, or things dealing specificly with gas tanks/bikes.

I am presently in the process of fabricating a tank extension for a friends bike. I am doing that by sticking styrofoam all over it, carving out the new shape for the tank from that, and laminating some glass on top of that. The first coat of glass went on today without incident, but it looks like there will be a lot of filling and sanding work to be done afterwards.


tanks alot,
bc
 

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practice

don't waste your time using carbon unless you feel like throwing money away. if you are intending on doing this without creating a mold than you are better off using plain old glass.

1.you need to make a shape ( plug)
2. once this shape is complete... sanded, buffed, waxed etc etc it is time to apply mold release
3. use the plug as your mold ( then you will have to fair the outside of the finished part or parts

or

you could build a mold ( tool to make several parts that will require little or no finishing on the outer surface.

do not bother using carbon since it is expensive and to fully take advantage of its properties you should be vaccumm bagging it or using prepregs... then you need to invest in a vaccumm pump or an autoclave.

sorry to sound like a composites nerd.... i kinda am one

good luck dude
matt t

yes frank if you are reading this.... i am really working on the three things you built those fancy filler necks for cause i cannot show up at the track with one before i make you 3 of your own
 

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BC,
Monkey is extremely qualified to give advice on this subject. He does this sort of thing for a living.
JohnnyB
 

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Discussion Starter #4
This is a strange sort of co-incidence, but the shop that I am using to do this work in is the same one that I use to build big autoclaves in. I have one at my disposal right now that is a 24"x36"x42" steam sterilizer, though I can run in on air if heat or vapor phase H2O2 is bad. How the hell do autoclaves help apply composites?

the carbon fiber is only for looks, its pretty.. it only matters that the tank is stong enough to hold back gas at 2 Gs (or whatever a 350 2stroke can do).. everything else (like safety) is secondary.

bc




Edited by - bcrawford on Oct 22 2006 10:54:11 PM
 

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no worries

the autoclave is a tool that will apply heat and pressure to compress and cure prepregged epoxy/carbonfiber and or whatever type of prepregged glass you get. prepregged is a term for a woven or stitched cloth pre impregnated with an epoxy resin. it will come on a roll and appear like a sticker. you caut it and apply it to a mold in an engineered fashion untill you have achieved proper coverage and thickness. i would then cover it with a high temp film designed for this process and stick it into the autoclave. the autoclave will compres and cure the layers forming a solid part.

release and play after that. i pretty much use wet preg... a process that involves saturating a dry colth with an epoxy resin then vaccumm bag this to become a solid part.

i could go on and on but this is the caferacer.net board not goo guy.net. i could go further and tell ya intricate details and secrets.. but then i would have to kill you

i usuallly build a few tanks a season for myself and or trade... totally not worth the time to do... it is a very tedious process and anyone who tells ya otherwise is a liar. i have seen peoples tanks split at the track... not so much fun. good luck, practice and do not waste your money on crappy polyester ones.

matt
 

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Discussion Starter #6
Thanks for the tips, when I get some cash together for the materials, Ill try that trick with the sterilizer.

quote: do not waste your money on crappy polyester ones.
so, it polyester itself bad?, or is it just that the commercially available tanks which happen to be make w/ polyester happen to suck?

quote: ..but then i would have to kill you
since its monday, that is actually a tempting offer.
 

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polyester is inferior compared to epoxy. polyester is heavier, and much weaker. also.... polyester is not compatable with gasoline.... it eventually eats the resin away... clogs up carbs etc... poly tanks are usually sealed with a gelcoat or an epoxy sealer..... why not just use epoxy???

matt

ps i am happy to help with any questions you have
 

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matt, i hope my tank doesnt do any of those things!!! we use autoclaves in woodowrking to bend wood. when you steam them, they need to be under some pressure to get the moisture in quickly. slow steaming makes the stuff split like a bannana. ive seem guys use pressure cookers too. i didnt know they ued them for laying glass and stuff. you guys must have a huge one.

jc
 

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actually we don't have one... when using prepregs...we just post cure the part in our massive oven under vaccumm... same thing.


your tank will be fine. it is epoxy... no problemo

matt
 

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i was kidding.

hey, why are you talking about em so much. you keep reffering to prepreg...

i dont know why, i got woman on the brain tonight.

jc
 

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i was kidding.

hey, why are you talking about em so much. you keep reffering to prepreg...

i dont know why, i got woman on the brain tonight.

jc
 

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Greetings! I stumbled across this fine site while in the throes of my street tracker project. Hope you don't mind if I unfurl my bedroll on the living room floor and go see what's in the 'frigerator :)

I've been doing some fiberglass work myself, hope it's okay that I resuscitate an old thread. Here's my first attempt at an airbox as practice:

http://19711007.blogspot.com/2007/07/airbox-fab.html

I'll attest to the need to go with epoxy resins as the Way To Go. I've been using a fast cure marine grade system from Tap Plastics, but I suppose there are equivalents out there. It just seems stronger, more dimentionally stable, doesn't stink to high-heaven, and is perhaps a bit more chemically inert, as even with the Isophthalic poly resins, I've read that you need to use a surface curing agent (e.g. "wax") to render that effect...tricky to do around the complex interior surface of a fuel tank, I bet.

Friends, I have a couple questions about the tank layup process. My tank will just be a one-off job. I'm inclined to use an approach loosely known as the "Lost Foam" method. Here, you craft the essential shape from polystyrene foam, and then do your layup over this object. Once the that process is done, you take a little acetone and pour it into the tank cap hole and watch in utter marvel as the foam melts away!

I've tried this process on a small prototype fiberglass "flask" and while it does mostly work, I see there's still a substantial bit of residue from the reaction. Some of it is indeed a little gooey. More acetone seemed to melt that away. Perhaps a coat of POR-15 along the interior wall will alleviate any worries, but I'm still not sure if this is a sound practice.

Any thoughts to share?

Anyway, thanks for allowing me to participate in the thread, this is a pretty cool site and I admire a lot of the cantankerous banter that goes on here.

Bye!

Adam
 

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adam,

a real interesting idea/concept. i'm sure matt (monkey) will see this and chime in as he is our resident composite expert.

i can only answer questions about love, sex, and hanging sheetrock.

welcome to the forum.

tex
 

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quote:
[...]
i can only answer questions about love, sex, and hanging sheetrock.
welcome to the forum.
[...]
Brilliant! I think by the end of this project I'll have punched a few holes in the wall, strained the relationship with my girlfriend, and ordered me up a few crumpets working on san pablo avenue in haste...Perhaps you're a man with the right experience to guide this thread along to fruition!

Stay tuned.
 

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i'm not advocating this site as i have no experience working with fiber but i saw this page a few days ago and thought i'd share it. this guy built carbon fiber side covers for his guzzi using a vacuum and a plastic bag to form the fiber over a positive.

http://www.webbikeworld.com/t2/carbon-fiber-motorcycle-parts/

i'm looking to redo my fiberglass seat and i'm wondering if you could use a similar technique for fiberglass.

...connoisseur of slack...
 

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i'm not wearing any pants.

ready for all of your pertinant questions!

texy
 

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quote:
i'm not advocating this site as i have no experience working with fiber but i saw this page a few days ago and thought i'd share it. this guy built carbon fiber side covers for his guzzi using a vacuum and a plastic bag to form the fiber over a positive.

http://www.webbikeworld.com/t2/carbon-fiber-motorcycle-parts/

i'm looking to redo my fiberglass seat and i'm wondering if you could use a similar technique for fiberglass.
Seems promising. He mentions sharp scissors for the work, not a bad idea of course. I'd highly emphasize throwing down the extra cash for a good rotary cutter (like a pizza wheel, but sharp as fuck), and a very big cutting board as your glass will be coming in large-ish sheets. You can find this stuff at craft stores. The Olfa brand cutter is very nice! And Friskars makes a tough, flexible cutting mat with gradations; get the biggest one you can fit into your life.

I used a cheap bicycle pump with the plunger reversed and a check valve instead of the vacuum cleaner. Seems to work okay, here's the recipe:

http://www.instructables.com/id/make-a-manual-vacuum-pump-for-under-$20-by-convert/

Vacuum bagging equipment can be had here (though there are many other places,this one sold the check valve in a 1/4" size):

http://www.acp-composites.com/acp-vbes.htm

The WbW writer talks about using sandwich bags, but probably for anything like a seat pan, you'll have to create your own bag for the job. The stuff that they sell on the above website is really strong and stretchy, too.

I've read that the nature of carbon fiber makes vacuum bagging almost necessary with complex shapes, though I find it's helpful even with fiberglass as it can still bubble and wrinkle when doing a layup with multiple layers.


Edited by - shortshift on Sep 21 2007 10:03:10 AM
 
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