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Thread: Any fiberglass experts?

  1. #1

    Any fiberglass experts?

    I'm in the process of planning a new koi pond build (re shaping & enlarging the existing one).
    The plan is a square pond approx
    12' x 12' square & 7' deep. 4' below ground & 3' above ground with
    a 6' x 2' window on 2 sides. It will be constructed from 7N concrete blocks on their side over a reinforced concrete base with a 4" bottom drain for the filter system.
    I quite like the idea of using on site fiberglassing instead of a liner so was wondering how easy would it be DIY for someone who has never worked with fiberglass and best place / costs of purchasing the stuff, or how much would I be looking at to have it done?
    It won't be before this winter / spring
    Thanks Wingy
    unless you can prove it beyond all reasonable doubt, it wasn't me. If you can prove it then you must be mistaken

  2. #2
    I did it for a year in my apprenticeship and then did Winnebago RV bodies in Canada for aa while.
    Is the structure only to be lined/made waterproof with Fibreglass matting or is it to be like a swimming pool and fully self supporting? The amount of water will need stressing out as the pressure on the sidewalls will be immense and don"t forget the winter freeze-up ice expansion risk.
    4 layers of 1.5 ounce mat & use polyester resin in a stippling hand action with a medium sized brush "clean often with acetone" or it will goe more stiff than I can manage these days" and wet the inner surface with 40% of the resin mix then lay the mat and work the resin in from the middle to the outside to lose the air bubbles. (only mix 2 pints of resin at a time until you have proven out your mixing ability as the exothermic action goes off like a flame thrower if not careful been there & done that) is a starting point, use disposable waxed cartons. CIBA epoxy resin is much stronger but costs a lot more.
    Gel coat for a nice top coat on the visible side and finish the inside off with fine surface tissue (this stops the 1.5 0unce mat ends sticking up like a bad hairdo)
    Use your oldest wellies as they will be thrown away afterwards. The polyester resin stink will follow your nose around for weeks also.
    And do it in the summer with a low or no wind as chills cracks the gelcoat.

  3. #3
    Watched a friend years ago making various things but on each occasion he used a former which he later removed when the fibreglass resin dried. He would then clean it up and cut off all the edges using an angle grinder and snips. It looked easy enough to do as he just laid strips of fibreglass and then brushed on the resin but you would probably need a respiration device so you don't breath in the fibreglass particles which float about.

    All in all I would suggest just buying a pre formed pond as the size your looking at would take a whole lot of materials and a lot of difficult work, especially if you have to get down inside it building up the layers or, enquire what a swimming pool builder would charge or even a plasterer who could render your concrete block form. At 7' deep it is going to be a lot of work whatever you use, good luck.

  4. #4
    Wings you can get a rubber liner you weld with a electric hot torch lot cleaner and quicker

  5. #5
    I have done a lot of fibreglass work in my time, everything from race car parts to huge wind turbine blades and I would have thought that there is a simpler and cheaper way! If you do go for it make sure that you have excellent respiratory protection because you will be in a seven foot hole full of styrene that is heavier than air, on second thoughts use breathing apparatus!
    If you really want to do it then do not mess about with brushes and small mixes, you will be there for months. On a job this size you want 5 gallon mixes and paint rollers to apply, then use a metal roller to consolidate.
    You will definitely need Gel coat to protect the mat from water but seek advice, gel coat will not cure properly exposed to air so you need to add wax or other additives to get it to harden properly in air.

    Could you not render it and paint with a suitable tanking paint?

  6. #6
    +1 to Defender:
    Another Wind Turbine guy here.

    Don't bother with glass and resin as the cost is simply not worth it, especially if you don't gel the surface and you get water ingress.
    I'd really recommend a rubber or plastic liner; consider using a think DPM sheet ( building suppliers ), and use that.
    To get a nice edge and hold the plastic in place then use stone or similar material.

    Uncured styrene resins, or epoxy resulting from a home mix may also poison the water and anything in I !


  7. #7
    youtube for different methods some have used a rubber solution others grp and then this to mix with concrete,
    if you do fibreglass you will need to insulate with foam first.

    the last method looks the easiest atb, wayne
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  8. #8

  9. #9
    Google G4 pond sealer. and go down the headings It will give you a lot of information on koi pond construction

  10. #10
    You wont beat fiberglass pond liner.
    I have kept koi for a long time and the liners are never as good.
    They never look great.
    Fiberglass is easy. Just line the pond with ply first then glass over, followed by a flow coat.
    Use polyester resin as its cheaper than epoxy.
    Buy materials from builders merchants (roofer supplies)

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