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  • OT - Fiberglassing

    I'm in the process of patching up my lawn tractor hood (plastic). I need to sandwich on a piece of plywood (or maybe sheet metal) to one corner where the hinge swivel is. But it's not really a flat surface, so I'll have to build up a thickness of about 1/4" in some spots.

    My question is, would it be better to build it up w/multiple layers, or just try to lay down one thick layer? ..and if building up multiple layers, is it best to let each layer cure and then sand, or just immediately slap on the next layer?
    With the temp around 90F, the stuff cures pretty fast.
    Lynn (Huntsville, AL)

  • #2
    If it were me. I would biuld it up and use epoxy resin not polyester resin. Make sure you bolt thru and use a larger insert than you would think to use. It helps a lot to drill holes so that you get thru bonding. Epoxy will bond to just about anything but metals have to be clean, oxide free and scuffed to about 60 grit so as to provide a good substrate. Jim
    Jim, By the river enjoying life...

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    • #3
      from what i know about f/glassing,you wait until the resin has just lost it's "tack",and then put on the next layer.It depends to some extent on the brand and/or type of resin,but usually this is 10 to 15 minutes.with polyester this could be overnight,so for speed(and less smell!),i'd also go with epoxy.BTW,old credit cards make great epoxy spreaders.good luck.

      ------------------
      Hans
      Hans

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      • #4
        A old caster off a bed with a handle tacked on it a excellent roller to mash the matt into the resin. I saw a Discovery channel special where they vacuumed and fed the resin into the double hull mold and it filled every matt cavity making a super strong hull.

        fixin cracks?
        I put a brace in when I do this, a wire or tig rods then glass over them, Not all resins will bond to metal thou.

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        • #5
          <font face="Verdana, Arial" size="2">Originally posted by ibewgypsie:
          I saw a Discovery channel special where they vacuumed and fed the resin into the double hull mold and it filled every matt cavity making a super strong hull.
          </font>
          Seeman Composites Resin Infusion Molding Process (SCRIMP) is a vacuum-assisted resin transfer molding process that produces parts excellent for marine, aerospace, transportation, and infrastructure applications. My interest is an ultra light weight strong hull for our racing yacht. Last Old Dog
          Not affiliaated with the authentic "Your Old Dog"

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          • #6
            What I've been using is polyester resin (Bondo) that I gotten from autoparts stores. Would've preferred epoxy but haven't found any locally. Checked with a Dupont auto paint store and while they had some higher price stuff, it too was polyester. Different brandname, but the fine print showed it also was a Bondo product.
            Lynn (Huntsville, AL)

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            • #7
              I'd lay up multiple layers, as quick as you can. The previous layer needs to be at least tacky when you lay a new one down.

              Use the autobody bondo. I made a pretty nice replacement fairing for a snowmobile with it. Redneck engineering at its finest!

              [This message has been edited by CompositeEngr (edited 09-18-2005).]

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              • #8
                Try a marine supplies store. They should have patching outfits for boats at the right price.
                bobby.
                boef

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                • #9
                  You can order epoxy from West Marine
                  http://www.westmarine.com/

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                  • #10
                    Sorry Lynn I should have put in where to get small quantities of needed materials. Most hobby shops that build rc planes and boats will have small quantities of epoxy resin and cloth of various weights. For your application I would think that somewhere around 7oz cloth not mat or roving as these don't have the omnidirectional strength you need. Though you could use cheaper mat for building thickness between the cloth layers. By the way most of the hobby shops around here also stock carbon fibre cloth and layups
                    Jim, By the river enjoying life...

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                    • #11
                      polyster resin seems to have difficulty bonding with some plastics..might be worth testing a piece before going "whole hog" into it. Also, if there's any cracks (stress/vibration type) in the damaged area would probably be worth drilling the ends of these with a small hole to keep them from radiating...I'd also go for the multiple layup here...take care & good luck

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                      • #12
                        the fiber glass & epoxy resin kits you get for boat repair realy work good , I used 2 $20 patch kits to fix some good size holes in an old boat.

                        It was realy fun , it was about 100F that day so I was drinking lots of beer, then the fumes from the resin got to me and I was blasted stoned.

                        anyway the repair turned out great.

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                        • #13
                          Yeah, I take 'Wooden Boat' magazine (great magazine BTW), and it has numerous sources' ads for this sort of stuff.
                          But when I finally decided to jump in and tackle the project, I knew if I waited for orders to arrive my enthusiasm would die.
                          I should've tackled it long ago. By waiting it permitted the weakened structure to crack and break in more places. ...the classic "Stitch in time saves nine" effect!

                          Oh BTW, a brief comment on Bondo's business practices. One kit I bought at Autozone listed the contents: 8 fl Oz of Resin, 1 tube (6ml)of hardener, and 8 Sq Ft of fiberglass cloth, and 1 plastic spreader. The box container was shrink-wrapped in plastic. When I got it home and opened it, inside the box I found a little slip that read: "Attention A printing error has contributed to a misstatement of kit components. ...kit contains 3 sq ft of fiberglass mat, not 8 sq ft as listed on the box. Thank you for your continued patronage."

                          Now if they were really interested in correcting the misprint, it would have been a simple matter to put the correction on the outside (underneath the shrinkwrap) where it could've been seen. Hmmm. Can you spell fraud?
                          Lynn (Huntsville, AL)

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                          • #14
                            <font face="Verdana, Arial" size="2">Originally posted by chkz:
                            polyster resin seems to have difficulty bonding with some plastics..might be worth testing a piece before going "whole hog" into it. Also, if there's any cracks (stress/vibration type) in the damaged area would probably be worth drilling the ends of these with a small hole to keep them from radiating...I'd also go for the multiple layup here...take care & good luck
                            </font>
                            I've already patched several areas, and it sure seems to have bonded nicely. I've been coarse sanding the plastic beforehand, but didn't think about drilling any stopper holes. Shoulda done that I guess. However I did extend the fiberglass well beyond the end of the cracks.

                            My biggest problem is in building up the areas with small chunks missing, that involve curves and such, and places requiring butt joins.
                            Lynn (Huntsville, AL)

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                            • #15
                              For a build-up that needs strength, I use "flox," which is chopped up cotten that's mixed with epoxy to make a putty. It's strong but heavy and a little lumpy.

                              www.aircraftspruce.com/catalog/cmpages/flockedcotton.php

                              For a build-up that's just for looks, you can mix "micro" into the epoxy (also sold by aircraft spruce). It makes a beautiful smooth filler, but doesn't have the strength of flox.

                              10F

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