DIY Kydex fuel tanks?

Discussion in 'The Garage' started by moontower, Feb 15, 2014.

  1. moontower

    moontower Adventurer

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    Recently, I have been contemplating making a larger fuel tank for my wife's plated klx140. I have a lot of experience with fiberglass and have made gas tanks in the past so I know that I have the ability. The problem with a fiberglass tank involves the new ethanol fuel mixtures reacting to the fiberglass and the fact that the tank will overhang the frame and be susceptible to damage.

    I also make custom gun and knife holsters out of kydex for local law enforcement officers and have become pretty skilled with the material. After a brief search, it appears that kydex has no reaction to fuels of any kind, including brake fluid and jet fuel. I can easily mold the kydex around the bottom of the existing tank and then fill the mold with foam and shape a new tank before molding the top and welding them together.

    Is there any reason that this wouldn't work?
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  2. Tripletreat

    Tripletreat Been here awhile

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    That's an interesting idea. I'm totally ignorant of that material, but after watching a couple of vids on YouTube, I have to ask, how would you close up the tank after you remove the buck or whatever you call the piece that gives it the shape? I think you have to make a tank in two halves, then join them, right?
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  3. SloMo228

    SloMo228 World Class Cheapass

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    Cool idea, I never thought of Kydex as a potential material for building a gas tank. If it's resistant to petrochemicals and ethanol, I don't see why it wouldn't work. It's a pretty tough material but you'd have to make sure you use an adequate thickness to prevent punctures/cracks in a crash.

    Definitely not going to be DOT legal, but I don't think that matters much for your specific application. The two biggest issues that come to mind are UV resistance and warping from engine heat. I've never worked with Kydex, but as I understand it, it doesn't require a terribly high temperature to soften it up, correct? If it's not more than two hundred degrees or so, I might be a bit concerned with it warping.
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  4. redprimo

    redprimo Been here awhile

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    fiberglasss works perfectly fine with ethanol, it's the polyester resin that is not comparable. Switch to a vinylester resin and you would be good to go.
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  5. GH41

    GH41 Been here awhile

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    Wouldn't hanging a couple of 1 gallon Roto-Pax containers off of the back of the bike make more sense?? I wouldn't play around with a homemade fuel tank fabricated with an unproven material. GH
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  6. moontower

    moontower Adventurer

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    Yep, after forming the two halves, i weld them together with abs plastic rods.
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  7. moontower

    moontower Adventurer

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    Thanks! You are right, not DOT legal, but for my application it doesn't matter. I form Kydex at 350 degrees and it begins to turn elastic at 250ish (maybe). I will definitely test it with my laser thermometer soon. If warping turns out not to be too huge of a concern, I may just make a heat shield for the tank to protect from the engine or possibly an insulated material on the tank itself.

    Your post did inspire a new idea though. I could very easily make an auxilary fender tank for the bike. From what I have read on the manufacturer websites, Kydex is very UV resistant (marine applications) and even with a moderate thickness will stand up to most drops without damage.

    I might fab something up this weekend and put it through some abuse while its filled with water to test its durability.

    Thanks for the tip, I may be able to use this in other applications, but in order to gain the extra fuel capacity on this tank, I will need to hang the material in an area that will be susceptible to damage. I think this is where plastic begins to outperform fiberglass.

    Mounting rotopacks would be a possible solution, but then I would have to fabricate a mounting system that would require a lot of work and the end product wouldnt be as useful as a larger tank or an auxilary tank. Plus the 140 is a pretty small bike and space is limited.
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  8. moontower

    moontower Adventurer

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    [​IMG]

    Here is what Im thinking for the kydex tank.
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  9. Plaka

    Plaka Brevis illi vita est

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    I made a part out of fiberglas once (my first project) that covered the back and half the roof of a VW rabbit (a camper that swung back and open). Later I wanted to destroy it so I took it to the dump and asked the bulldozer driver to run over it. D9 Cat went up one side and down the other. Not so much as a crack. Maybe I should have skipped the rovings on the inside? I also broke up a friends old hot tub. I came with a stedge hammer. All it did was chip the gelcoat. I ended up having to saw it up.

    You can make a FG tank that will bend the bike frame before it so much as cracks. Alternate layers of cloth and mat, nail the glas/resin ratio. maybe some rovings. I would make it in one piece with the lost foam process. No seams, little more finishing on the outside. Set the metal fittings into the layup. No bolt-on and seal later. Much easier fit-up to the bike, you can work out every contour before you get sticky. I'm doing some new luggage this way to fit the standard Krauser racks. Avoid Kevlar and CF.

    For kydex I would check your welds first. Do one in some scrap and see what it will take. Also with that kind of construction you can do internal baffles to give more strength and control fuel slosh which can make for instability when riding in the rough with a large tank---half empty.


    RotoPax is the fast and simple solution. Not crazy about their size/volume ratio but if space is limited, make the rotopax the rack you pile everything else onto, y'know? They can be used as structural elements in a design. You can wax 'em up and pull glas right off them to make holders that contact a lot of surface area. Ditto other sturdy fuel cans.
    #9