Epoxy fillers and ratios for epoxy fabrication

Discussion in 'Materials' started by likelylad, May 31, 2017.

  1. likelylad
    Joined: May 2017
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    Location: Suffolk, England / Okayama, Japan

    likelylad New Member

    Hi everyone

    Apologies for my first post here not being related to boats - but I'm looking for advice on some fillers and ratios to add to epoxy to fabricate a motorcycle seat pan. It's going to be sitting across the frame of the bike with multiple points of contact on the frame (but not a flat surface).

    I'm using Kevlar pulp first (supplier's recommend ratio of 1:15) to get some descent tensile strength but need to create a thick clay-like substance to roll onto a piece of fibreglass cloth before laying it into place on the frame to cure.

    What would be the best additives to use and roughly what ratios would be best? Done some research and found out there are thixotrope fillers, microballoon fillers etc but still clueless on specifics for this application.

    I'm aware of ready-made marine products like wet and dry 700 that contains Kevlar but it's not available where I live.

    Cheers for any help!
     
  2. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Have you seen the "Gougeon Brothers on Boat Construction" or the instructions for West System epoxy?
    http://www.westsystem.com/wp-content/uploads/GougeonBook-061205-1.pdf is a free download for the "bible" of wood/ epoxy construction ( has information about glassing also).
    West system website has "projects" of many diverse types, perhaps one would have something that matched your needs.

    However, if you make something "clay like" it is probably not going to penetrate the glass enough to actually strengthen the glass.
    According to my experience.
    You would probably need to put a thick plastic film draped over the frame to make the shape you want and get a piece of glass/ epoxy to stay in the shape you want and not drip thru and ruin frame/ equipment below.
    You might also need to support the plastic with something like styrofoam to get smooth surfaces between the frame.
    Will you need a raised lip around the edge of the pan? That was typical of seat pans many years ago, so the actual seat covering had something to be attached to and support the seat foam.
    Most seats are supported on some kind of a rubber bushing to help keep the contact points from grinding off the paint.

    What bike?

    Cloth is much easier to get tensile properties than any chopped fiber - but I'm not familiar with using Kevlar pulp.
    Do you have a link to the pulp method? I might have a use for it on a boat. :)

    Good luck
     
  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Welcome to the forum.

    I've used Kevlar fibers and pulp, but as mentioned, not the best approuch for your needs. Also I'm not sure I fully understand you application approuch which seems a drape style of thing, with wet, thickened goo that you're hoping will be moldable/shapeable? Without a fabric (cloth or stitched) you'll have a very difficult time with this. What you want is something that will drape and form the shapes, which a fabric will do. Once this is setup, you can add a bulking layer or two.

    Specific ratios aren't as easy as you might think, being environment and cure rate dependant. If I was doing a seat pan like this, I'd coat the bike contact areas with plastic packaging tape, so the pan can be removed once cured. Next I'll wetout a pre cut to size hunk of 12 or 17 ounce biax, draping as desired. This will tend to sag in unsupported areas, so maybe some cardboard (also protected with packaging tape) cut to fill these voids to hold up the fabric. It all depends on how much butt shape you'll want, frame rail locations, etc. as to where you might need additional support. After this initial laminate has cured or while it's still "green", you can bulk it up with a few layers of a combo fabric, like 1208 (biax/mat).

    You can also use the technique that sound box builders do, when making custom woofer and speaker boxes, which is to stretch a headliner material over a frame (or the bike), which is then wetted out as mentioned above. Again, like mentioned the headliner fabric serves to hold the shape, until the initial wetout coat dries, at which point you can go back and bulk it up or in their case (the box makers) just start apply bondo to smooth it up. A seat pan will need a fair bit of bulk to tolerate a serious butt, so consider it's total thickness as you go.
     
  4. jorgepease
    Joined: Feb 2012
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    Location: Florida

    jorgepease Senior Member

    Im prob misunderstanding but why not laminate some wood into that shape as a mold and then just build a carbon fiber pan, will be much stronger than the mud method.
     
  5. likelylad
    Joined: May 2017
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    Location: Suffolk, England / Okayama, Japan

    likelylad New Member

    Thanks for your input guys! Spent an hour or so scouring the west systems site last night looking for similar projects. Were a few involving fabrication without wood but none that were really load-supporting I think. I've downloaded the Geourgeon PDF, it's gonna take my a while to absorb all the good stuff in there!

    After your comments thinking more now about making more of a makeshift mould on the bike using duct tape and batons, laying some cloth down first and then using more of a putty (rather than a clay) spread over the top and allowed to cure.

    I've actually managed to track down the YouTube vid a saw a while back which inspired me in the first place. It's a seat pan kit they were selling (although can't track down a retailer now) with a two part epoxy clay. There are a few steps but this one has the guy actually mixing the clay and rolling it out onto the cloth to be laid onto the frame (as you suggested PAR, covered in tape with tape stretched over gaps to give support).


    (This one has the guy putting it onto the bike )

    There's one point which is bothering me - he rolls it out to a thickness of 5/16ths. Seems a little thin? Yet he assures the finished pan will be 'stronger than you'll ever need'.

    Upchurch - here's a link to the Kevlar pulp. Don't have any experience with this supplier so can't vouch for them though: Fillers - Kevlar® Pulp http://www.fibreglast.com/product/Kevlar_Pulp_544/Fillers

    The bike is a 1984 Honda GB400. Reason for fabrication is because there's a little 'dip' for the front rider to sit in on the stock seat which my other half keeps slipping forward into when she's riding pillion, causing me to in turn be gradually squashed groin-first into the tank. So going to create a flatter, lower and narrower version which is a little more comfy. Going to use the original rubber bushings and attachments pulled from the stock seat, as well as a couple more to give some more support and protect the frame.

    Snapped a photo to give a rough idea. Sorry about all the crap attached - it's my daily runabout bike. Got some general clean up and restoration to do.

    [​IMG]
     
    Last edited: Jun 1, 2017
  6. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    You could use the original pan and attachments since it is so complex.
    Get some mini-cell foam , shape it to match the seat base, then shape the top to your desires.
    Much simpler and it will fit.

    You will still have to come up with a new seat cover.

    Minicell Foam at nrs.com http://www.nrs.com/product/2076/minicell-foam
    You can glue this stuff together with contact cement
    This stuff is stiff, but it works well for seat cushions - you don't need 3" to get a comfy seat - 1/2 to 1" will do. It is commonly used for kayak seats.
     
  7. likelylad
    Joined: May 2017
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    Location: Suffolk, England / Okayama, Japan

    likelylad New Member

    I thought about that, but unfortunately (not really visible in the photo due to the toolkit cover) there's a built-in toolkit compartment on the pillion end, which the pillion sits on top of. There's actually hardly any foam butween that and the pillion's bum - a problem that I want to resolve in my new design. Would love to cut that bit off and fabricate a new end but with the hassle of figuring out how to attach it, I'd rather just build a new pan the way I want.

    There's the added advantage that if I can figure this out, I can use the same method for future projects. I've got a bad habit of acquiring rare bikes with few aftermarket parts and stock seats are rarely things that I get along with!
     
  8. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    Use the old pan as a mold.
    That's the only way you are going to match the mounting.
    Good luck.
     
  9. likelylad
    Joined: May 2017
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    Location: Suffolk, England / Okayama, Japan

    likelylad New Member

    That's very true! I'm setting myself up for a world of pain getting those attachments to line up.
     

  10. upchurchmr
    Joined: Feb 2011
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    Location: Ft. Worth, Tx, USA

    upchurchmr Senior Member

    I'm still stuck on doing this easier.
    How about just cut off the toolkit compartment, then do your composite trick over the opening?
    Should be easy to make a temporary backing over that limited area, then bond the glass/kevlar/ whatever to the seat pan.
    Matching the foam would be easier and you could get enough foam depth while reducing the height of the back of the seat.

    I'll quit now, you might just want to do this your way to get experience for other projects - which is what you said!!

    If it doesn't work so well, you can still fall back to using the original modified pan.
     
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