Aggressive Mini Speed Boat Sketch...would it work?

Discussion in 'Boat Design' started by LilWake, Jan 17, 2013.

  1. LilWake
    Joined: Feb 2012
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    LilWake Senior Member

    So I sketched up this mini boat idea I had in my head.

    I mainly sketched this from a cosmetic standpoint. Wanted to see something with Lamborghini inspired angular design and sharp stealth body lines. This boat would be approx 12' long with Jet Drive; maybe powered by a Seadoo 255hp Rotax 4-TEC powerplant.

    [​IMG]

    [​IMG]

    So what I wanted from you guys was your ideas and opinions on whether this design could be useable, effective, efficient...or if it is outright horrible, haha. I am no fluid dynamic engineer so you're not going to hurt my feelings! :)

    My thoughts are with the right power, the hull design might almost act like a smaller boat once on plane, but have twice the bow lift for better holeshot because of the hatchet looking keel up front.
     
  2. Submarine Tom

    Submarine Tom Previous Member

    Sure it'll work.

    How much power is needed to make it work will be the question.

    Put a big block V-8 in it and you should be fine.
     
  3. Olav
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    Olav naval architect

    I have my doubts about these (not quite so) little vertical appendices. All they're gonna do is cause some massive drag, provide something to eventually trip over and are prone to being damaged when hit by floating debris in the water.

    Also I spot quite hollow cross sections over the whole hull length, which are not very effective when it comes to providing lift to plane. The strange forefoot shape is something I would redesign as well - it looks draggy when going slowly and would turn out as a source of terrible slamming loads when going in a seaway.

    Make sure you have a clean water flow towards the jet intake. A nacelle like the one in your sketch is fine to lower the jet in a hull with significant deadrise (and in addition, it might improve coursekeeping also), but you have lots of sharp knuckles and corners on your hull which should be investigated very carefully.

    I don't want to stop you from trying something or to think outside the box, but keep in mind that planing boats have been around for quite some time now and that there's a reason why they look how they look...
     
  4. Submarine Tom

    Submarine Tom Previous Member

    You did say aggressive, right?

    "There ain't no replacement for displacement."

    Cubic inchs that is...
     
  5. johneck
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    johneck Senior Member

    Yeah, I agree with Olav. You can do what you want above the waterline, but be careful below. Those side bumps just look like a problem, no useful purpose. The bow sticking down will only cause drag and bad slamming, no real benefit. One of co-workers used to say that if something looked bad it certainly was; if it looked good, it still might be bad, but at least you had a chance.
    BTW, one of the benefits of the jet drives is the ability to trim the jet up and down. This can help get the boat up on a plane quickly.
    Another point is that what matters, assuming you have a reasonable shape, is power and weight. Jetskis for the past few years have increased the power dramatically, but at the same time increased the weight, so they go no faster now than 15 years ago.
     
  6. gonzo
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    gonzo Senior Member

    All those knuckles and protrusions will create a lot of drag and make handling unpredictable.
    The bow has that, whatever it may be called, that will make the boat broach and oversteer.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Simply put, no, for a lot of reasons. Below the LWL, you have a host of issues and with that much rocker, you'll launch all right, but it's not going to go well, after the first second of a WOT blast. Climbing the hump trim, will be in the 45 degree range, so good luck with that.
     
  8. tomas
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    tomas Senior Member

    Could he keep the hull aesthetics mostly intact if it flew on foils just beneath the surface, (assuming a modification for water intake to feed the jet), as a work-around for the hydrodynamic issues but still keep it potentially fast? It could fly just above the surface...
     
  9. PAR
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    PAR Yacht Designer/Builder

    He doesn't have the most basic of hydrodynamic principles covered and now wings and a drop down jet intake? Sure, anything is possible, but you do have to have a clue, when you're climbing way out on a limb, with any expectation it's not going to break.
     
  10. Olav
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    Olav naval architect

    tomas,

    maybe - if it flew. But first you have to get that thing up on the foils. The foils themselves are draggy before they start developing significant lift so you generally need lots of power at the resistance hump before you are fully foilbourne, thus making matters even worse...
     
  11. tomas
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    tomas Senior Member

    Well PAR and Olav, when I see products like the Jet-Lev water jet pack selling at 100,000 Euros each, (which I find to be crazy), and MegaYacht owners towing expensive tenders across the Atlantic (even more crazy to me), I could not rule out the possibility that LilWake could get investors and hire the talent to solve the obvious hydrodynamic issues so that he too, could successfully sell toys to rich clients.
     
  12. johneck
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    johneck Senior Member

    The lawyers In the US would love that toy. Should provide a lawsuit a minute!
     
  13. TANSL
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    TANSL Senior Member

    ... and besides, it's a pretty ugly "utensil" (subjective opinion, of course).
     
  14. LilWake
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    LilWake Senior Member

    OK, as I said feel free to tear the design apart. But please have some tact about it. Please be constructive with your responses. I am not looking to offend anyone with this design; just trying to think outside the box a bit.

    I am all for power, but V8's would be much on the heavy side for this project. This boat would have to be nimble, agile, and light weight.

    About the downward extruding panels on the sides; the idea was to work as sponsons do on a jet ski, which act as a rudder while turning adding more grip and sharper handling. They would sit just above the water line while on plane, just high enough to avoid debri and prevent drag. They wouldn't be as thick as they are shown, but just wanted to enhance them to show dimension so they would be more visible. What are you're further thoughts on these after this explanation? Still no good? Maybe with further design they might be effective?

    I can see now that this may be a problem. I was designing to provide lift but this might be too much where after hitting a wave at speed the impact might be greater because the lifting surface area under the bow.

    I appreciate your in depth response, and that is what I am trying to do. Just think outside the box a bit. That's why I am here is to get feedback to better this design.

    Beauty is in the eye of the beholder. I think it looks great, haha.

    Yes, I am very curious how this would act. It's hard to tell. The design would be very similar to any other boat, but just imagine it as second keel added in front of the first. Both very similar in shape and design. How the two meet is what makes me curious.

    Can you explain this more. I don't understand.

    After the first few questioned the downward extruding "sponsons" I actually thought maybe them could be converted to foils, but with the jet drive this would probably be very complicated unless the foils made the boat sit with the waterline flush with (or just above) the pad.

    I think the power/weight ratio would be high on this boat. Probably around 255hp/800lbs...1hp for every 3lbs. Of course this is in it's stock form. A guy named "Trond" put a custom turbocharged version of

    Why don't you explain why?

    Thank you! That was nice of you to say :)
     

  15. yipster
    Joined: Oct 2002
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    yipster designer

    Looking at the sketches on my less than 4 inch mobile they look like a stepped hull?
    these not to underastimate hulls come in a great variaty, read up on stepped hulls!
     
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