Fiberglass hand layup help

Discussion in 'Boat Design' started by savagescout, Jan 7, 2011.

  1. savagescout
    Joined: Jun 2009
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    Location: australia

    savagescout Junior Member

    Hi guys,

    I am currently undertaking a hull extension (transom extension) on a 23 foot hull. I was hoping to get some advice/tips and techniques large layups.

    The approximate surface area of mould area is approximately 50 square feet with about 30 square feet consisting of vertical surfaces. I am using vinylester resin with alternating layers of 450gm Chop Strand matt and 600gm double bias with a layer of 250gm chop strand matt stitched to it. My intent is to layup the extension to a consistent thickness of approximately 10-12mm or 3/8-1/2 inch.

    I was hoping to be able to do in one session 1 layer mat, double bias, another layer of mat, double bias before allowing to cure and then repeating. I was hoping to get peoples advice on doing large areas layups like this and in particular any tricks/tips on wetting out these large areas quickly (both horizontal and vertical surfaces).

    I really appreciate the advice and look forward to what people recommend.


  2. Roy Berntsen
    Joined: Jan 2011
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    Location: Oslo

    Roy Berntsen Roy Berntsen Design

    You do it part by part, not the entire area at once. Of course you should know the working window of your glue(vinylester).

    Anyways you typical start with one layer of ccm and you wet one of the 1/2 sides of V bottom. The wetted surfdace should be as long as the with of the fiber

    You cut the length of the fiber as long as the with of 1/2 your Vbottom + an overlap 5-10cm in the V + 5-10 cm in the V/vertical

    You finish this layer and then wet the next part of your 1/2 V in the lenght direction as long as the with of your fiber.

    When done with the 1/2 V, you should do the other 1/2 V.

    You then let this harden before laying your next layer. This due to heat and mold displacements. - to thick layer will harden to fast and might deform the mould and or face of the finished product.

    Next you layer the vertical portion in the same manner. You want to do the whole area of one layer ccm before moving on to your bia.

    I dont se why you want to use ccm between the layers as you write. Usually the added ccm layer on the bia is for gluing purposes and give little streghth. ccm adds much more weight than bia so you should consider using rest of the layers as bia.

    You can for the next layers do 2 layers of bia at the time, letting it cool off before the next patch. Same procedure as the first layer.

    I hope some of this was helpful... :)
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  3. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    It would be much more helpful if you offered some photos or drawings of what you're attempting, some back ground on the boat, the design alterations, general scantling schedule, type of mold, etc., etc., etc.

    Is this a sugar scoop type thing or an outboard bracket or what? Your proposed 3/8" to 1/2" seems thick for a small boat and terribly inconsistent (25% difference).
  4. savagescout
    Joined: Jun 2009
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    Location: australia

    savagescout Junior Member

    Thanks very much for the responses already.

    The hull and mould picture is as follows.


    My idea was to do layup of just the mould first (with no connection to the hull). My aim was to achieve a layup of approx 3-4layers. Then tab this to the existing transom. I could then remove the mould and grind the external edge where the hull meets the new moulded section. From here i would be able to apply 2-3 layers of 450gm csm mat and filler (i'm not after strength with this external joint).

    I could then cut out the existing transom and grind a large taper of 1 foot between the existing hull side and new extension and run full lengths of glass layers to achieve my thickness of 3/8". The reason for the 3/8" thickness is because that is the thickness of the existing hull.

    Any further help with the extension layup would be much appreciated.


  5. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    As a rule, you'll what to do you hull prep first, so grind back all your tabbing area with the mold off the boat. Then reattach the mold and preform your layup in one shot. What is this, an outboard bracket, I/O, straight shaft or what? Judging by the general size of that hull, you'll need 3/8" in the topsides, but like will have considerably more in the loaded areas on the bottom.

  6. couch
    Joined: Dec 2010
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    Location: NL (Can)

    couch Junior Member

    For hand layup after all prep is completed :

    Cut and test fit all pieces of materials and sort accordingly.

    Gel coat stop
    skin coat (2 X csm) stop (especially if you are concerned with print thru).

    Remainder of laminate - keep in mind that if you are outside of the time frame for secondary bonding you will have to scuff and clean the skin coat layer lightly to ensure proper bond.

    If you do not care re print thru and are careful re exotherm / resin open time / etc. you can do the full layup in on shot - if not experienced though too much laminate can lead to warping / shrinkage of the part.
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