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Thread: What is scuffing and how do i do it?

  1. #1

    Question What is scuffing and how do i do it?

    People have recommended scuffing the bottom of my boat to get more speed and i wanted to know what exactly that means.

  2. #2

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    Scuffing the bottom causes air bubbles to form along the hull and actually makes it slicker than the smooth painted fiberglass. It breaks the friction/suction that develops between the water and the hull. It's only really necessary for the last half of the bottom of the hull that was below the water line in operation.

    Most use either a red Scotch-Brite pad or wet/dry sandpaper in a linear motion, bow to stern. I don't recall what grit# for the wet/dry paper though.

  3. #3

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    Just take some 400 or 600 paper with water and knock the shine off anywhere that runs in the water...mainly just the bottom. decrease water tension on the hull and runs faster.

  4. #4

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    ok thanks for the info

  5. #5

    Cool

    Scuffing the bottom causes air bubbles to form along the hull and actually makes it slicker than the smooth painted fiberglass....
    Actually, air bubbles will not support a model boat and they do not reduce friction. When the shine is removed from a hull bottom - if done correctly - it allows the water to adhere firmly to the hull surface rather than just beading off. This reduces overall drag because there is less friction between water and water than there is between water and a solid 'dry' surface. This is why waxing a fast boat hull increases overall drag.

    As Jeff stated, use 400 grit wet-or-dry to remove the shine - you still want a smooth surface. Depending on the surface, block-sanding works well.



    .

  6. #6

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    does it also reduce heat buildup?
    Stiletto tunnel,EPV135 (53") twin cat, CT06"Spirit of Qatar", FD 47" mono, Twin Mini Cat 23.5"

  7. #7

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    Quote Originally Posted by Mel279 View Post
    does it also reduce heat buildup?
    Funny...

  8. #8

    Cool

    Funny...
    Actually it can, although the amount of heat reduction would probably be minimal. Anything which frees up a hull will allow the motor to unload, reducing amp draw and lowering heat buildup.



    .

  9. #9

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    I assume this will also be effective on an ABS hull? I am thinking about doing this on my SW 26 now...will it really make a difference?

  10. #10

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    After scuffing my sponson bottoms, they measured.000000000000000000000128 degrees cooler.
    -t

  11. #11
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    The heat thingy depends on the speed of the boat. Some boats have to worry about ice buildup. Me - I'm somewhere in between ice and heat...........................................

  12. #12

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    Quote Originally Posted by D&D View Post
    The heat thingy depends on the speed of the boat. Some boats have to worry about ice buildup. Me - I'm somewhere in between ice and heat...........................................

    hay d & d
    did you do it to the cat in the pic?
    gonna try it on my ekos...any tips

  13. #13
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    Scubasteve95, Yes we all started "roughing" up the bottom after the "Secret" came out concerning Dennis Connor's boat when it won back the Americas Cup" in 1987. The "Secret" was a 3M milar that they developed for (I believe) Boeing to reduce drag on some plane Boeing was working on. 3M offered it to Dennis Conner to try on one of his many hulls he was preparing for the Americas Cup. In testing Connor's discovered that the hull with the milar was running up to three-quarters knots faster under all conditions. During the Americas Cup Connors kept the bottom of his hull covered much like the Australians did when they won the previous cup from the US.

    It's kind of like when the Australian Wombly(sp?) set the 300mph on water and in one of the filmed documentary work they showed him tourching off three inches from his rudder to increase speed. Heck, we had boats in the Capitol RCers that wouldn't even turn after we all saw that and no one had a method to really measure whether or not we had gained any speed. (My MM's rudder is 4 and three-quater inches long......)

    Bottom line, is yes I roughed up the bottom of my MM and tried by best to "blueprint" the bottom to make sure it was reasonalbly flat.

  14. #14

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    Just a note... I also use painters taper...blue stuff to tape off the bottom of the hull to form a nice "edge".... that way it doesn't take the nice look away from the whole bottom of the hull and it looks like it was meant to be that way.... kinda like a real boat...lol.

  15. #15

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    I thought about trying a coat of bed liner spray...it is rough but not sure how it would do.

  16. #16

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    awesome....thanx for all the good tips...now were did i put that sandpaper?????????

  17. #17

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    OK,
    this is the route i took...
    taped then sanded sponces and then coated with spary bedliner.......let you
    know how it worked in a few days.

  18. #18

    Cool

    Guys, "rough" is not the secret. You want the bottom to get "wet" so that the water sticks to it. It is this film of water that does the trick. I know what the bottoms of the world's fastest FE boats look like because I've seen and handled them - and they aren't "rough". They were very smooth.

    BTW what works on a full-scale displacement sailboat at 15 knots is not at all what's going on in a planing hull going three times that speed. And it was my recollection that Connor used mylar on his carbon-dacron wing sails, that's what gave him a speed advantage. Hmmmm.

    .

  19. #19

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    Does anyone have any recorded data that supports that scuffing your hull will produce any noticeable increase in speed? I'm all for going faster, but don't want to sand down the nice finish on my hull for only a fraction of a mph.

  20. #20

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    No data and it is not as obvious on a small hull but you can gps it and see what you get.

    I do have some footage somewhere on the few of the big cats like CMC, etc that shows dimples (outteys not innies) in the ride pads and asked them if that was to help resistance and he said yes...I will have to dig it up but they were there. Of course you are talking a 10,000 pound boat.

    You can do it or not....this is an old idea that proved out long ago. Again, you are only scuffing the shine off...should feel smooth like a babies butt...LOL

    I also saw some racing boats with a sand paper mylar on the bottom....even many hydroplanes and dragboats use it. I am sure it is a spray coating but it proves they are doing something.

    It works...just do it or not...no harm either way.... On a cat it is the bottom of the pads only is all I do. Hydros I do the sponson and the last few inches of the rear end that may drag.

  21. #21

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    OK GENTS,
    here is the look and monday will be the test.
    top speed was 41.2mph...so lets see what happens before
    we all get worked up
    ps:
    thanx jeff i think i see the problem now,
    just needed a second pair of eyes...
    Attached Images Attached Images

  22. #22

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    well here are the results,
    no diff.........speeds were the same........
    looks cool so i'm going to keep it....so the answer is
    smooth,scuffed,rough.........zero change......

  23. #23

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    Quote Originally Posted by forescott View Post
    Does anyone have any recorded data that supports that scuffing your hull will produce any noticeable increase in speed? I'm all for going faster, but don't want to sand down the nice finish on my hull for only a fraction of a mph.
    bogus....but thats about all...if any
    i had high hopes

  24. #24

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    Thats kinda what I expected. Theoretically sound, but not at this scale. Thanks Mythbusters!!

  25. #25
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    It definately isn't bogus. Scuffing that is. I sure wouldn't spray bedliner on my ride pads either. I generally just use the 3m red scotch brite pads to scuff. With that coat of bedliner, you have also gotten rid of any nice square (sharp) edges that you need for the hull to corner well at speed.

  26. #26

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    You need to read what Fluid said about 400gt sand paper not bed liner! You did it all wrong with the black stuff. they do 400 to 600 on wind surfers for speed runs. I used to do it when I raced for Bandit Boats we did lots of testing and it works if done rigt.

  27. #27

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    Does look cool but hate to see you did that. I was thinking maybe some sandpaper or somthing glued on. Scuffing will be better...BUT...no speed change means it did not affect it badly so we know that now!

  28. #28

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    Quote Originally Posted by Jeff Wohlt View Post
    Does look cool but hate to see you did that. I was thinking maybe some sandpaper or somthing glued on. Scuffing will be better...BUT...no speed change means it did not affect it badly so we know that now!
    EXACTLY,
    had it scuffed before i spayed it....as i said ...no change...zero
    i knew rd would have something to say(as always negitive),
    but thats what makes the world go round...
    boat turns the same..edges are just fine...wad...
    and lets see some numbers..alot of talk but no data..hhmmmmmm

  29. #29
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    How was that a neg. comment? It was on topic, and fact. You think you're the only person to attempt to change the ride surface of a boat? Scuffing has been done for a long time. The results, can vary from model to model. Also, If your boat is running too wet, it isn't going to make a bit of difference.

  30. #30

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    Data! Bandits gas mono went 4 mph faster when scuffed on the gun we ran it then scuffed it and ran it again all in about 5 min so there would be little change. if done right it works

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