Page 4 of 4 FirstFirst ... 234
Results 31 to 33 of 33

Thread: Whiterabbit's 2015 Mercedes GLA 45 AMG

  1. Back To Top    #31

    Re: Whiterabbit's 2015 Mercedes GLA 45 AMG

    There is much more to glass than thickness, but you knew that already.

    Chopped matting has some key advantages. The primary advantage being the non-directionality of the fibers. This provides superior pinhole resistance, unlike a weave which can pinhole with the fibers get spread in an area, compromising the box seal.

    There are two very key disadvantages to chopped matting. First is it cannot conform to compound corners. If I wanted a flat panel, I'd just use MDF anyways. We work around this by cutting strips or squares, and in extreme cases using loose fibers to make a slurry. Second, it DRINKS resin and fibers separate. This makes it super-easy to get a target panel thickness with a minimum of material, but super-hard to do it with the strongest glass-to-resin ratio. Weave or roving doesn't puff up, so you need more fiber to get it thick. But the strength is higher because all your strength of course comes from glass, not from resin. So matting is a false economy.

    Beyond that, matting is a nightmare to finish. I remember many a discussion on CAF, ECA, and DIYMA about the best body fillers to use, the best techniques to pre-grind the box, obtain a smooth surface for filling, etc. What a nightmare! Doubly so when the matted fibers start poking up during the layup, creating a surface layer that looks like pinhead form hellraiser, and just as unpleasant to handle. That's fixable my making the surface layer a cloth mat, but it's going ot be bumpy because the under layers are a hodgepodge of matting squares. You'll probably find you don't even need to add resin to the surface cloth layer, it'll soak in from underneath because there is so much extra unused resin pooled into the matting.

    ------------

    None of this was your question. Your real question, was is it cheaper? my guess is from a materials perspective, no. However, I used ZERO body filler on my box, and would have needed zero bodyfiller even if I had exposed fiberglass in compound corners on the top side. Good bodyfiller is expensive, so we're getting closer to parity.

    Factor in labor hours, even though it's a labor of love, and it's not even close. I did the whole thing in ONE layup, and I was done after that. No building up layers, no sanding, grinding, filling the weave, fussing over this or that. It was: make the layup, press the base wood rings into the layup, ensure the wood is soaking up enough resin to adhere, and let cure. Pop out and done. No followup, no "milkshake", no fuss. Just filler-primer and paint.


    I am blessed to have several TAP plastics close to me, so I don't pay shipping, only sales tax which in California is about 75-90% depending on your county and city.
    -------

    NOW, the elaborate material stackup was just for fun on my part. I could have easily bought a few yards of 8 ounce woven cloth and used only that material to build up my layers to get the desired thickness and off I go. I would have ended up with the same result. But it was more fun to experiment with novel materials, because this layup was frankly so easy. small compound corners, a relatively flat surface. It makes it easier to experiment with materials so I have the working familiarity with them should I want to do something more advanced in the future, tight compound corners, vertical surfaces, etc. So it was fun.

    But you WILL NOT make a panel as strong as mine using only chopped matting, unless you make your panel thicker, heavier, and uglier. But yeah, it'll probably cheaper before you start using bodyfiller.

  2. Back To Top    #32

    Re: Whiterabbit's 2015 Mercedes GLA 45 AMG

    That's definitely a fair assessment. I did some google searching last night about using coremat. From what i could gather from old diyma, and 12 volt forums. It was that Coremat really wasn't a great idea for enclosures. I never found an actual reason but the guys who were "glassing pros" all unanimously said don't use it.

    I also did some YouTube searches of coremat and it looks like it may be a little bit tricky to actually use on anything that wasn't a fairly easy curve.

    What i did find was that most people recommended using a base of 2 layers of mat for a solid mould, then knytex then mat(to absorb extra resin from knytex) then Knytex and repeat until you get desired strength.

  3. Back To Top    #33

    Re: Whiterabbit's 2015 Mercedes GLA 45 AMG

    Coremat will not easily conform to compound corners. Most of those "pros" are likely glassing corners far tighter than the compounds I'm dealing with in the photos above. The panel I made is highschool-level glassing, which is why I can get away with using it. Those pros are likely tackling top-tier difficulty projects, which is why most of them end up looking like kindergarden-grade on the inside and need so much followup to clean up the structural mess.

    No matter what the stack, there can't be any air bubbles for peak strength! We're not making airplanes here and can tolerate some bubbles, but big gaps are definitely a waste. That's likely where those guys are coming from.

    I still prefer to add a layer of twill on top and bottom even if the next layers are knytex. Maybe it's aesthetic overkill but it is just so much easier to get a nice surface with a standard cloth, then put the thick stuff in the middle. The knytex has a thin layer of matting (thin enough to conform to compound corners), and I've been stabbed by needles of stray matting enough in my life. I want that stuff LOCKED up deep inside any layup I ever do. Ever.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Back To Top