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Thread: Hull trueing

  1. #1

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    Hull trueing

    ok after taking a look at my hull i decided to true it out due to a lot of dings from beaching it!! i have my ski upsidedown but have no idea of what else i need to do other than fix the dings! if anyone can give me some tips thet would be great!!

    mahalo


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    My son (mohawk man) jeffsntx's Avatar
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    http://greenhulk.net/forums/showthread.php?t=9690

    This is a previous discussion about hull trueing in the FAQ section. Hope it helps.

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    why so rough? you would think it should be really smooth.. has anyone tested smooth vs rough?

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    800AMSOIL4U's Avatar
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    Quote Originally Posted by Tommy Gun View Post
    why so rough? you would think it should be really smooth.. has anyone tested smooth vs rough?
    Really smooth sticks to the water too much. (slowing you down) Try putting a piece of glass down flat them putting water on it and putting another piece of glass on top of it. Now try to pull it apart. It is very tough to do so. Now if it is roughed up some it is easier to pull them apart.

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    so what gritis the best??

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    EZ Dock of Long Island Shibby1485's Avatar
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    good thread... been reading about this myself past couple days... going to start truing my hull this weekend following the extremeracing website...

    my concern tho is painting it afterwards, if the paint is going to totally kill the truing job... white hull is getting painted a totally different color, and i'm not sure of the best approach

  7. #7

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    i think if you put a clear coat on and sand then buff it should stll come out! ill let you know how it works with my ski!

  8. #8

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    "ROUGH" is a relative thing.

    Some guys on the west coast would drag there hulls in the sand on the beach to "smooth" or "true" there hull in days long past.

    The point is that the GPR was casted from a mold, and as such would shrink from the dry out period. Based upon what a professional boat builder friend of mine said, the GPR hull is not bad out of the box. I trued mine with 220, fixed the dings, primed and resanded with 320, then had painted. My friend told me to maximize the speed that I should use 1200 grit and sand "lightly" across the hull rather than the length of the hull. Talk about going against conventional wisdom!!!!

    His reasoning was to use the "rough" paint to slow the trapped gasses in the water so that the hull would float on trapped gas rather than plow through the water and "stick". Like I have said, "rough" is a realtive thing. In reality, you want a smooth hull that has just enough roughness to trap gasses. As smooth as fish and birds are, even they have rough edges. That is the thinking.

    To "true" the hull, take off just enough material to where a 1 yard straight edge lays flat from back to front.... the back or stern is the most important part. Fill in all devits, and sand all humps.... no more, no less. You are not trying to reshape the hull, just make it straight.

    If you sharpen the squared edges of the strakes, your boat will turn much crisper and tighter... your hull will not roll or slide near as much.

    If you are trueing to increase speed, you will more than likely be disappointed. Unless you have major damage, you might gain 1mph, and that is a lot of work for that much speed. Your boat will handle much better though.... that is if you like a hard no nonsense turn.

    You are going to find a concave or "cupped" area betweent the end of the skeg and the beginning of the intake tunnel. This was put there, according to an enginnering friend of mine to help accellerate the water before it enters the intake gullet. Some have filled this area in and have not reported any down side. My friend suggested that I make it slightly more concave.

    Not all hulls are created equal. I am specificly talking about a GPR, and I know what I did worked. If you are working on a different hull, then beware!

    I believe that some Seadoo hulls, and in particular the RXP have a "hook" built into the stearn to help stabilize the boat. I do not know this for a fact. I do know that before you attempt to "true" anything other than a GPR or a GP, try to find out exactly what the builders intent was. You might be creating a problem that you did not have before by sanding off something that was designed into the hull.

    Hope this helps.

  9. #9

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    what about the pump tunnel, should it be really smooth or rough as well?

  10. #10

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    so you say the gasses? do you mean when the ski is cutting through the water it is spliting hydrogen and oxygen, it that what you mean by the gasses?

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