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  1. #1
    shiftarno's Avatar
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    hull trueing gp1300

    whats the best way to square the tailing edge of the hull


  2. #2

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    There are a lot threads on hull trueing on this forum. Mike Thorne, aka:Pistonwash had done a thread years back along with others. On the GPR most of the results that I read about were minamal speed increase with improved handleing. I haven't got any speed results for you, but the water does seem to be released from the hull much better, because while I am decellerating from a speed run, my hull seems to slide forever, and I am having to rethink when to begin slowing down.

    On my GPR, the turning became much crisper, especially in the mid to high speed range. You have to be careful though, you are not trying to reshape the hull, just knock off the high edges and fill in the low spots. Sharper strakes as compared to the rounded factory ones make your hull turn sharper, and you have to be prepared for it.

    Back to your question: I used the West System Epoxy resin (105) with the 205 hardner and the 404 high density adhesive filler purchased at West Marine. Fairly expensive, but it gets it done.

    As I was trueing the hull, I allowed the resin to semi harden, then along the trailing edge I built up the rounded corners with the resin. I went from side to side rather than front to back to build it up. I block sanded it with 100 grit, then cleaned it up with 320, then 400.

    It took me 3 passes to get it right, but it is dead on. I did every trailing edge, including the trim tab area... even the sides of the trim tab area.

  3. #3
    shiftarno's Avatar
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    ok that answers my question pretty good i didnt know if i just start sanded alot of the hull away to make it square....or add some material with epoxy and the square it off

    dam u even squared the sides of the trim tabs??

    so all this squaring in the back really wont give me any top speed increase?

  4. #4
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    how hard is the intake grate ,pump shoe and ride plate alignment?? and what exactly has to be done

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  6. #6

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    I only squared the trailing edge of the trim tabs. I squared the side of the hull that was cut for the trim tabs.

    When the hull is upside down you can find the center of the intake tunnel by measureing its width. You then mark it half way across on the transom plate. You find the center points of the ride plate and shoe and mark these spots with a center punch or nail etc. You then align the center punch dings.

    With the intake grate, mount it loosely then slide it completely to the side of the intake tunnel until the front wing comes in contact with the side f the tunnel. Using a gap gauges, find the distance of the gap between the wing and the tunnel on the other side of the grate that is not in contact. If the distance for example is 80 thousandts, you split the difference to where the wing has 40 thousandths on each side of the wing and the side of the intake tunnel

    I've trued 3 GPR hulls and the last one seemed to give me the best speed increase, but to date I have not done any speed runs on this boat.... it has other issues. I will say this though of the three hulls that I have done, the last hull was done down to the finest detail and it accellerates and handles much better than the other two.

    I am not a professional boat builder of any sorts, just a rider. My experience is that if I were looking for speed gains, trueing this hull would not be my first choice for increasing speed. I am so impressed with how it handles though and have to give it high marks for that.

    If you square the hull up, the "working" part of the hull, that is the part of the hull that is still in the water at high speed has actually increased about 1/4 of an inch. (The length of the hull has increased) Factor in the width of the hull times 1/4 inch and you have that much extra surface area to help support the weight of the hull and rider when you are at high speed. The hard 90 degree angle that you shaped aids in releasing the water and allows the boat to slide through the water more efficiently. In theory, it should go faster.

  7. #7
    shiftarno's Avatar
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    alot of usefull info thanks

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