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Thread: Q's about fiberglass and epoxy!

  1. #1
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    Q's about fiberglass and epoxy!

    Ok guys, I want to gather somem info before I venture my self into doing a custom panel for my car. I was wondering were does everyone buy the fiberglass cloth and the epoxy and bondo? Any local stores where you can find all of the stuff needed or should I go ebay?! Reason why I ask, is because 3 days ago, some @sses broke into my car and stole everything so I would like to make something better than stock to hide my stuff...

    Israel

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    Maximum Bitrate GoHybrid's Avatar
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    i go to a local plastics supply shop (www.plasticareinc.com). Truly though, for 99% of in-car fiberglassing, you don't need anything exotic, so you could just go to your local hardware store and get chopped strand mat, polyester resin, bondo, brushes, masks, gloves... you name it. I could find everything i need to do a custom form project at Lowe's or Home Depot.
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  3. #3
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    Quote Originally Posted by GoHybrid View Post
    i go to a local plastics supply shop (www.plasticareinc.com). Truly though, for 99% of in-car fiberglassing, you don't need anything exotic, so you could just go to your local hardware store and get chopped strand mat, polyester resin, bondo, brushes, masks, gloves... you name it. I could find everything i need to do a custom form project at Lowe's or Home Depot.

    Thanks man.. So lowes or home depot should have the fiberglass/strand mat? Strand mat is the same as fiberglass right?!

  4. #4
    FLAC
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    There's two main types of materials that are used in fiberglass fabrication: mat and weave. Mat looks like a bunch of strings pressed together with no real order because they take a string and chop it at intervals and then press it together once they have enough of 'em. Weave or cloth, looks like what you see in a nice carbon fiber piece, nicely arranged rows and columns of strings.

    Mat, if applied correctly is IMMENSELY stronger than cloth but it's hard to get a finish on without a ton of work. Cloth is still strong, but doesn't soak as much resin up as mat so it's a bit weaker. Cloth is easier to finish because you get a nice uniform surface to work with and it usually takes shapes and curves more readily than mat.

    Lowe's, Home Depot, Auto Zone, Advance Auto Parts all have cloth and mat. Some may not have resin, some may not have body filler it's really a crap shoot.

    They all also sell nitrile gloves. I'd recommend these because they're stronger than latex and they keep you from getting resin/body filler all over yourself.

  5. #5
    Phillie Escalade182's Avatar
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    commonly refered to as CHOPmat.

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    I just did (started) this messy job over the weekend.
    Lowes sale Elmo brand resin, mat, and cloth. Homedepot and everywhere else sale Bondo brand. If you use mat, buy a roller. Otherwise, it is a BIG STICKY MESS.
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    Maximum Bitrate GoHybrid's Avatar
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    i tend to disagree about the strength of chopped strand mat versus woven cloth. Perhaps chopped mat is more omnidirectionally strong, but it's ultimately the glass that takes the load. resin is brittle and merely serves to keep the glass strands aligned to whatever shape they've been given. a longer strand more closely oriented in opposition to a load is going to be stronger. I believe that'd be the reason you don't see things like "chopped carbon fiber". The whole point is to try and align the longest possible strands to the load. There are threads here and elsewhere that discuss how to take advantage of this and orient adjacent layers at 45 and 90 degrees to eachother.

    also... i think it is far easier to get chopped mat to follow compound curves than cloth. Cloth has a tendency to bunch up unless you cut reliefs and darts around tight compound curves. Mat is held together with a resin-soluble binder. Once that binder dissolves, you can move strands more or less completely independent of eachother to follow a curve. with no bunching up.

    as far as finishing goes, that depends partially on your methods. As an experiment, I made a form with chopped mat and polyester resin, and instead of just stippling it with a brush to get air bubbles out, i used a vacuum bag and a squeegee to work air bubbles out. Between the pressure and vacuum, the part i pulled was not only glass smooth (with very minor imperfections) but it was almost completely transparent.

    just food for thought. not trying to start any fights.
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  8. #8
    FLAC
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    Mat is stronger because there's a bunch of different overlapping strands. It's the same reason that OSB is stronger than sheet ply.

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    Maximum Bitrate GoHybrid's Avatar
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    http://www.fibreglast.com/contentpag...inates-84.html

    this link explains some of the differences between woven cloth and chopped strand mat.

    i think mat can appear stronger because it is more rigid across all axes, whereas you could easily flex an equivalent thickness of woven cloth off it's two axes. I still have to maintain that given an uniaxial load, parallel to the fibers, a woven fabric will be stronger than chopped strand mat.

    We should probably clarify at this point that it's all the same glass... so it really all boils down to it's orientation in opposition to a load.

    Think about structural concrete. Concrete buildings are reinforced by creating matrices of steel rebar typically oriented parallel to anticipated loads. House construction uses 2x4s and beams oriented in direct opposition to the major loads. I have no doubt you could create something structurally sound by cutting tiny bits reinforcement and cramming it randomly into a matrix of binder...

    but i think the real question here is strength-to-weight ratio and structural efficiency. In this case, woven fabric laminates are going to be superior to chopped strand laminates PROVIDED that the plies are oriented adequately in opposition to the load.

    Composite engineers chime in anytime and correct me if i'm wrong!
    Et ipsa scientia potestas est.

    Worklog for my 2007 Civic Si ...f*** it...
    Pictures of the Corolla (retired)here
    Need to make something? Here are a few ideas.

  10. #10
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    BSME in composite materials engineering chiming in...

    Clif's notes: either will be fine for our applications. Use what's easier to work with for you. I use cloth just because I don't have good luck with chopmat.

    As is referenced in GoHybrid's link, the woven cloth is stronger in an on-axis tensile situation. In a subwoofer enclosure, I would say that either cloth or mat would be acceptable, given proper layup techniques. The key here is to minimize voids and inclusions in the resin. While it is there simply to hold the reinforcement in place, the resin ultimately contributes to the overall strength of the composite part. If a crack propogates in the resin, it will ultimately find it's way through the part around the fibers and cause the entire part to fail. The point: Get rid of all of the air and don't allow contaminants to get into your cloth or resin. I would also do whatever I could to do all of your structural layup in one step to maximize strength. Don't lay up new layers over hardened ones. The new resin will not chemically bond with the hardened stuff and there is the chance of failure along this surface.
    Granted, this probably isn't going to be an issue with a reasonably designed enclosure, but it is an issue none the less.

    You're experiment with vacuum bagging was exactly what we can do to maximize strength and uniformity of resin. My experiment years ago was to build an enclosure using flat sandwich panels of 1/2" closed cell foam with 3 layers of 90 degree carbon cloth on each side. Layed the panels up, bagged them and let them harden. Then we assembled the panels with a baffle of 2 layers of 3/4" MDF (Density for subwoofer mounting.) After initial assembly, we filament wound the entire enclosure with carbon fiber and bagged that. The result was quite strong because the entire enclosure was wrapped with continuous fiber (Look at a fiberglass nitrous bottle or soft water bottle...) The entire enclosure was probably less than 30 lbs (48 by 12 by 10 or so), and plenty strong for 4 10W3s sharing about 2kW.

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