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Thread: T shirt material for fiberglassing?

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    T shirt material for fiberglassing?

    Basically trying to save myself a drive to a JoAnne 3 days after they re-introduced a mask mandate.

    I'm making pillars to hold a 2" Dynaudio/Volvo dome, a Bohlender Graebner Neo3 PDR planar, and a Focal TN52 tweeter per side.

    I have the structural work done using ABS and a plastic welder. Needs a few alterations and more shaping but basically it's far enough to see the next steps:

    From hereI think I can most quickly and easily tackle the cosmetic layer by starting with a fabric stretch as the base for the bodywork, vs more ABS patching and forming.

    Normally I'd use spandex and brush resin in for light stuff like this but I don't think I have any -
    But I do have a bunch of old T shirts I don't mind sacrificing. I've just never used jersey for this purpose.

    I imagine it'll be a little less stretchy, and soak up a little more resin, but otherwise work OK...

    Anyone able to confirm or caution against?

    Sent from my LM-G820 using Tapatalk

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    Owner BigAl205's Avatar
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    Re: T shirt material for fiberglassing?

    I don't see where it would be a problem, I've used old socks and grill cloth for backer material before. It just gives you the basic shape, then reinforce it afterward.

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    Wave Shepherd - aka Jazzi Justin Zazzi's Avatar
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    Re: T shirt material for fiberglassing?

    Quote Originally Posted by BigAl205 View Post
    I don't see where it would be a problem, I've used old socks and grill cloth for backer material before. It just gives you the basic shape, then reinforce it afterward.
    Yep, exactly that.

    I am not a fiberglass hero but I've certainly done this before!
    Measure with mics, mark with chalk, cut with torch, grind to fit, sand to finish, paint to match.
    Updated Justin tuning sheet (Justin and Erica tuning companion for SMAART and REW)
    Do it for them.

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    Noob TheTodd's Avatar
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    Re: T shirt material for fiberglassing?

    I’ve used old T-shirts in multiple pillar builds before. No issues so far.

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    Re: T shirt material for fiberglassing?

    I've always had it in my head to keep pillars as light as possible, because of their role covering the airbags. Putting mids up here is relatively new to me, personally.

    The more I think of it here, though - it might be better than a spandex - a little thicker should make it a little stiffer.

    I say that because notice a little flexing happens each time I need to remove or install them, mainly because of the two locking tabs at the base.

    So I do want this area rigid so my body work and finish doesn't crack, even if it makes them a little more of a pain to install.

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    Re: T shirt material for fiberglassing?

    The only thing that matters in a material for wrapping to fiberglass is the materials stretchiness and its absorption. You want something that wet outs extremely easily and conforms to many different angles.

    Somehow fleece got introduced as a great way to make fiberglass stuff. Fleece is fucking horrid. It takes soooo much resin to get fully soaked. It sags from the weight of not pulled super tight. All around it's just terrible.

    Aim for something stretchy and thin. T-shirt material is perfect.

    Sent from my LM-Q730 using Tapatalk

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    Re: T shirt material for fiberglassing?

    Quote Originally Posted by geolemon View Post
    I've always had it in my head to keep pillars as light as possible, because of their role covering the airbags. Putting mids up here is relatively new to me, personally.

    The more I think of it here, though - it might be better than a spandex - a little thicker should make it a little stiffer.

    I say that because notice a little flexing happens each time I need to remove or install them, mainly because of the two locking tabs at the base.

    So I do want this area rigid so my body work and finish doesn't crack, even if it makes them a little more of a pain to install.
    keeping pillars light is not good! Focus all the weight where the drivers are and it will sound better, and if youve ever seen an airbag go off you really shouldn’t worry about it staying put in any way, even if deadened, it’s the clips that need to remain factory, don’t go adding screws unless factory, but reinforcing the pillars won’t do anything to stop an airbag deployment

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    Re: T shirt material for fiberglassing?

    Quote Originally Posted by dumdum View Post
    keeping pillars light is not good! Focus all the weight where the drivers are and it will sound better, and if youve ever seen an airbag go off you really shouldn’t worry about it staying put in any way, even if deadened, it’s the clips that need to remain factory, don’t go adding screws unless factory, but reinforcing the pillars won’t do anything to stop an airbag deployment
    That's true - I'm lucky with my selection, this is an odd collection of drivers.

    Down low, I already have wooden rings with braces of 1/8" ABS welded to hold the Volvo/Dynaudio domes. Those themselves are already in their own sealed, steel cups, which means I don't need to make these A-pillars acoustic environments, and that's nice. That portion is definitely rigid already. I'm lucky with these, that way.
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    The more interesting part is up higher on the pillars - those really are pair of drivers teaming up to be "tweeters", and that's it:
    I have two Bohlender Graebner planar speakers that really essentially have no moving parts - less motion than a dome tweeter. I do want to see how low I can get them to play, but still we're only talking 2000hz and up, probably. Maybe I'll get lucky, 1500hz?

    I mocked them up in the basement rig (photo shows it in the process of teardown, but that's the main structure - my fiancee can't wait to see that gone) with the windshield, dashboard, and you can see all the passive Xovers - the tweeter output of the JL XR comp set Xover feeds into the white 10khz Xover on the front of the 'dash'. So in the test rig, the BG Neo3 panels were playing from probably 2500hz (I'm just pulling that from memory, which shouldn't be trusted since I bought those JL XR's in the late 90's) up to 10khz, then my Focal TN52's playing the role of supertweeters, from 10khz up. I just loved the BG's but they only go up to about 15khz. This also avoids beaming, and I think 10Khz is high enough to not be an issue - but I have room to push that Xover point up as well.

    I definitely still do need a good baffle surrounding those though. I wouldn't leave it with just a layer of impregnated T-shirt, I do agree with you.

    But fortunately, really it minimizes my needs, structurally and acoustically even.
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    There's still the chance that I have to do something a little more than an open-back pillar panel with some stuffing and CCF behind it, I'll probably start with a patch of MLV sealing it in, but I don't think I need to do much - I even tried to make a "worst case scenario" for these BG Neo3's when playing with them -
    Originally, they were in an evaluation box with an angled back and stuffing, and they sounded great. Then I moved them into the shallow, flat enclosure below... it's a tiny chamber with a scrap of whiteboard as the back panel, exactly parallel to the driver, even. Still sounded the same, I ran some sweeps and didn't notice much variance in the curves either. Seem very forgiving.
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    So I think some CCF with some MLV making it so it isn't a pure open baffle will be better than the half-assed kludge that it sounds like.
    Easier than needing to make some sort of a cabinet out of the pillars, since the domes and the TN52's have their own enclosures.

    I can't wait to get them installed in the car, on a DSP, and see where my Xover points will ultimately end up.

  9. Back To Top    #9

    Re: T shirt material for fiberglassing?

    Quote Originally Posted by dumdum View Post
    keeping pillars light is not good! Focus all the weight where the drivers are and it will sound better, and if youve ever seen an airbag go off you really shouldn’t worry about it staying put in any way, even if deadened, it’s the clips that need to remain factory, don’t go adding screws unless factory, but reinforcing the pillars won’t do anything to stop an airbag deployment
    You also got me thinking today during a slow day of work, having looked at Parts Express junk mail today -
    I only own the Bohlender Graebner Neo3's, but GRS appears to have borrowed/stolen/rented the architecture identically. I own both the 8" Bohlender Graebner and GRS flat panels, and did listening, and to my ear they sounded identical. I even measured the two, and they seemed identical as well. So I presume the GRS 3.5" and the BG Neo3's are as close to identical as matters.

    I say that because I'm looking at the specs and plots for the GRS ones - just had them up as I was thinking and eating my lunch. Both BG and GRS sell the 3.5" version open (as I own) and with a back cup (which is tiny), so I'm just checking that out-

    Predictably, the response with the cup just impacts the low end-
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    vs with the cup:
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    For reference, here's how tiny the cup is (highlighted yellow) - Oh, and check out that impedance plot!:
    Click image for larger version. 

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    So I'm theoretically liking the idea of a non-rigid wrap around the backside of these, but the structure supporting the driver will be rigid.

  10. Back To Top    #10
    Noob DubScientist's Avatar
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    Re: T shirt material for fiberglassing?

    That cabin mockup rig is hard core

    Things will sound very different in a vehicle, but still, kudos!

    Interested to see where this goes.
    HU: Pioneer P99 RS
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