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  1. #1
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    sanded hull bottom. Mythe or no?

    I've heard that sanding the bottom of the hull is beneficial. Is it true if you use course sandpaper in continuous strokes, front to back, that these scratches act like many small rudders? It's supposed to help keep boat going straight? Anyone try this or know if it's true? I know it's not pretty to look at, but if it helps control at speed, I want it. Anyway, it's WAY WORSE, losing to, or barely beating an ugly ski.


  2. #2
    ph2ocraft's Avatar
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    From the files of Group K

    "HULL FINISHING - When you take delivery of any new 1050, the bottom surface of the hull is very smooth and shiny. While this finish looks real nice, it is totally non-functional. The ideal bottom surface finish is a non-shine finish created by numerous full-length front to rear "scratches". The best way to accomplish this finish is with a piece of very coarse emery (40 - 60 grit is best). All the sanding strokes should be front to back (continuous) for the full length of the hull. The deep, full length, scratches should eventually eliminate any part of shiny surface. While this preparation may not look attractive, these scratches will act as thousands of small rudders that will make the hull track "a lot" straighter in all water conditions. These scratches will also allow for much better surface holding in high-speed turns.
    We consider this preparation to be mandatory for our 2 seater 1050's. The added nose lift, offered by our ride plate modification on the two seater, means that there is slightly less "steering" hull contacting the water surface. A shiny hull, at this attitude, can tend to "seek" at high speeds. This sanding preparation allows the same 2 seater hull to run arrow straight at peak speed, along with much more responsive steering control."

    I don't know that I would like this speed run without the prepped hull, I remember at lower speeds with the "shiny" hull it was slippery back there. We attributed the better speed to the straight tracking ability, right or wrong I don't know.
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    Last edited by ph2ocraft; 12-22-2006 at 12:27 AM.

  3. #3

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    al you still got that boat that thing is a 3 seater 2 stroke dream

  4. #4
    ph2ocraft's Avatar
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    I'm keeping it until I have to sell it for the room, I just bought Liz her new Yaptor 700 so room is getting REALLY tight. I'll sell the SLTX when my Ultra 250 hits the dealer.
    I guess I better say thanks to Kevin for storing a couple of my boats.

  5. #5
    Hydrotoys's Avatar
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    Don't sand your hull, unless you want to go slower.

  6. #6
    john zigler's Avatar
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    Quote Originally Posted by hydrotoys View Post
    Don't sand your hull, unless you want to go slower.

    why do you say this?

    on our boats, we have always sanded the bottoms. ( full size boats, not skis). it is a well known fact, a blue printed, sanded bottom will yeild better preformance than a smooth shinny one. water will cling to a smotth surface. you want it to break away easily from the hull. i sand all my skis too.

    zig

  7. #7
    Hydrotoys's Avatar
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    I sanded a GPR hull per the "experts". It lost speed and handled no different. I paid a few hundred dollars to have a painter put it back shiny.

    Theory is nice, but it didn't work for me. Never again!

  8. #8
    john zigler's Avatar
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    something must have been done wrong. ( although i am not sure how you could screw it up).

    i have a 20ft hydrostream boat, with a 250hp yamaha outboard. i gained 300 RPMS buy sanding the bottom. also made it feel much more secure at speeds over 90mph.

    in the boat world, it is a well know fact. it needs to be done if you are going fast. ( PWC are really just small boats).

    personally i ride stand ups, but we have always spent alot of time paying attention to the bottoms, and have proven results, through lots of testing. i know many others have too.

    the only thing i can think of is maybe you had a flaw in your GPR hull. ( a hook, or rocker) and it the problem was amplified.

    we treat all lower units, props ect the same. anything that really touches the water will benifit from being dull. i usually wet sand with 400 grit, and sand from bow to stern. make sure all strakes, edges, ect are sharp and true. it is also a big benefit to shapen the transom. ( make it very sharp).

    zig

  9. #9
    Quote Originally Posted by hydrotoys View Post
    I sanded a GPR hull per the "experts". It lost speed and handled no different. I paid a few hundred dollars to have a painter put it back shiny.

    Theory is nice, but it didn't work for me. Never again!
    Hydro- I respectfully disagree to a point, what needs to happen for GPS runs is have a chemical that will create a "bubbling affect" on the bottom of the hull creating a non-pressure point. Meaning you don't want the hull "sucked" to the water scrubbing speed. I think sanding it is too extreme as well, as you can create too rough of a surface. There should be a happy medium there on PWC's. Maybe Richard can chime it about how race boats do this!

  10. #10
    Hydrotoys's Avatar
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    Just sharing my real results. Yours may vary. Sand them till you are happy.


    I never EVER will again. You can keep that theory.

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