Making a poly boat go faster

Discussion in 'Gear Talk' started by Greenkiteskier, Jun 13, 2019.

  1. Greenkiteskier

    Greenkiteskier Paddler

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    Can anyone tell me how to go about smoothing the bottom of 2004 Looksha iv to get the scratches out and give it more speed.
     
  2. Peter-CKM

    Peter-CKM Paddler

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    Shave off threads hanging down with a razor. Or you could try melting the plastic so it reattaches, and smooth it while doing so, to the hull.

    That said, I doubt doing all the work you could possibly do will make any noticeable difference in speed.
     
  3. mick_allen

    mick_allen Paddler & Moderator

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    Make that thing sitting on the bottom a little lighter and stronger?
     
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  4. Jasper

    Jasper Paddler

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    Take a forward stroke class.

    Seriously, I'm not (just) being snarky. No matter how much experience you have or how many classes you've taken, going back to the basics and refining your stroke will do more for your speed then any material improvement.

    Then remove the seat back and replace the pegs/pedals for something stiffer and fly!
     
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  5. Greenkiteskier

    Greenkiteskier Paddler

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    Thank's Jasper , I'm taking a lesson from an instructor/guide next week. And I'm not slow, can do 4-5.5km/hr at present. Always room for improvement though.
     
  6. Tangler

    Tangler Paddler

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    A typical cruising speed is about 3kn which equates to about 5.5km/hr.
    A few scratches on the hull aren't going to affect speed much unless they have danglers.
    Trim off anything that might create drag, give it a wax, take some lessons, start saving for a glass boat...
    In the meantime have fun paddling. :)
     
  7. Greenkiteskier

    Greenkiteskier Paddler

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    Thanks Tangler. What wax should I use?
     
  8. Tangler

    Tangler Paddler

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    Boat/RV wax is all I use.
    Slap it on. Rub it off. Go faster (especially down gravel beaches when your back is turned...).
     
  9. Peter-CKM

    Peter-CKM Paddler

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    Waxing plastic boats? Never done it, not heard (before now) of people doing that.
     
  10. Greenkiteskier

    Greenkiteskier Paddler

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    Thanks Tangler, I'll try it. I'll ask the instructor if he's heard of it , but I'll try it anyway.
     
  11. Tangler

    Tangler Paddler

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    Not sure I have heard of it either... :)
    However I do wax my glass boats and it does feel like they go faster.
    If the wax is decreasing friction then it "should" work on plastic too.
    "Easier" is probably a more accurate term than "faster".
     
  12. designer

    designer Paddler

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    Wondered about the science behind the waxing because ... the base of xc skis are "scored" so they don't allow surface tension (drag?) to occur. I guess I'm asking is there a point where the slippery (waxed) hull has more drag because it allows this surface effect compared to a rougher surface.

    I wash/wax because it allows me to inspect the boat carefully - reinforcing lessons/options like getting out in shallow water a few feet from shore vs running to boat up on the beach.

    I do have to warn helpers to hold on to the toggle when thye lift the boat because the hull so so slippery it can be pulled from their grip - not in a tug-of-war fashion; they are just not holding it as tight as they needed to.
     
  13. Astoriadave

    Astoriadave Paddler

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    "Friction" is usually in reference to two solids in contact. "Drag" is the more common term to refer to the resistance boats encounter when they slide through water. Mick could probably give us a thorough treatise on the various forms. And, what is known about the factors which enhance drag.

    Turbulence, for example, often increases drag, but is unavoidable. Airfoils passing through air, however, perform better if there is a little turbulence introduced just forward of the maximum thickness of a wing. In models, a very thin thread is sometimes glued to the wing there, running spanwise, from the body of an aircraft to each of its wingtips. Counterintuitive, no? Such turbulators probably have hydrodynamic counterparts, also. Something to consider as you shave the hairs off that plastic hull.

    Hydrodynamics is half guesswork, half empirical knowledge, and half witchcraft. Yeah, does not add up. Because hydrodynamics depends in nonlinear physics, where a tiny change can produce a large effect, aka "the butterfly effect," much bandied about after many natural systems were shown to follow the precepts of chaos theory. Weather, turbulence, and lots of others.

    Maybe the bottom line on whether to wax or not, shave the hull or not, comes down to try it, and then measure the effect on hull speed in quantitative testing. Yeah, get some repeatable numbers.

    EDIT: Designer and I crossposted. Surface roughness, which many think can reduce hydrodynamic drag, is an effect like that of turbulaters on airfoils.
     
  14. Redcedar

    Redcedar Paddler

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    Put some weight in the bow ... that way you are always paddling downhill :D
     
  15. Greenkiteskier

    Greenkiteskier Paddler

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    Hey You guys thank you all. I will try this stuff as soon as I can. Waxing,shaving and weight in the bow(haha). It cant hurt
     
  16. designer

    designer Paddler

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    Are you going on a date or going paddling? Waxing, shaving and a little extra weight in the bow can't hurt.
     
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  17. Tangler

    Tangler Paddler

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    Just found an article on the Epic website (FAQs) that stated that waxing really doesn't help directly, but that having a smooth clean hull will.
    Apparently having small grooves parallel to the flow of water helps a lot but is illegal in racing circles...
     
  18. mick_allen

    mick_allen Paddler & Moderator

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    Holy cow designer:
    gulp, spew, clean off the keyboard! . . . those might be the truest off topic, off colour words ever written here.
    **
    I'm a little distracted now but here's a graph to contemplate: Friction coefficient versus 'speed' [Reynolds number].
    SurfaceRoughness-Sanding.jpg

    It's baseline is a basic painted surface and from there various treatments are done to it. The sample size is a 1.5m x .5m flat sheet aligned with the flows just under 4 knots to just under 8 knots. Don't have time to check, but I think the sanding is circular motion.

    A quick comment is that drag per surface area is not constant, typically gets less along the boat and has a drag hump back at the transition point from laminar to turbulent. And is most important at the front of the vessel.

    All the above is just viscous or friction forces and it sure doesn't seem to be simple.
     
    Last edited: Jun 17, 2019
  19. Astoriadave

    Astoriadave Paddler

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    Good to see that data. Any turbulators?
     
    Last edited: Jun 17, 2019
  20. mick_allen

    mick_allen Paddler & Moderator

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    No surface tripping, 10 repeats for each data point, calculations that transition point was similar for each run.
     

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