hydoplane design engineers ?

Discussion in 'Boat Design' started by afrhydro, Dec 25, 2009.

  1. mark775

    mark775 Guest

    I don't know. This Tcubed obviously knows more about aerodynamics. Dan pointed out that the boat is a tail dragger - for sure, it dosn't look like hydros I know. I am hesitant to say anything - What I would do myself and what I would recommend someone else do are two different things (I would have thot a canard but the aero guy says no). The wrong move could cause this boat to stuff. I, personally, would Google aroung the F1 boats sites and see what they are doing to theirs.
     
  2. afrhydro
    Joined: Mar 2008
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    afrhydro Senior Member

    yea its a rough subject ill get it with hydrodynamics / the air traps on the rear
    the guys that have tunnel boats that go a 100 + cant stand the fact i built this from the hip so to speak and am willing to do the r&d real time they think thats crazy when theres other hulls out there i could have used to do the same thing
    then theres the motor guys
    but i am so close to haveing a good safe 100 mph river running hydroplane that it would be crazy not to finish it and it seems if i make it to a 100 ill gain there respect is it worth it probely not i would be happy with 80/85 im damn proud of 75 mph
    thats deserves respect right there IMO
    my new prop might get her over the hump but its all good
    thanks for helping guys i made it this far and know the boats attitude very well i can tell when it dont feel right
     
  3. Submarine Tom

    Submarine Tom Previous Member

    Well, if you suddenly stop posting, we'll know you got it wrong...

    Good luck!

    -Tom
     
  4. afrhydro
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    afrhydro Senior Member

    lol
    that wont happen till my last day alive and that may never have anything to do with the boat who knows
    but if anyone thinks of anything im still all ears
    i wont ever go over the edge till i see what it looks like first
     
  5. afrhydro
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    afrhydro Senior Member

    heres the overhead shots you wanted
     

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  6. Tcubed
    Joined: Sep 2008
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    Tcubed Boat Designer

    Quick thoughts-

    Horizontal stabilizer with somewhat greater wingspan than the max beam of the boat. This should be large and place aft of the engine, for maximum effectiveness. It also needs to be at a slightly smaller pitch angle than the aerodynamic surface of the hull. The best is to make it adjustable so you can experiment with different settings until you get optimum control. (greater control implies greater speed potential)
    These boats tend to operate with just enough weight on the hydrodynamic bearing surfaces so as to keep it under control. Until there is a gust of headwind which tips the balance of forces in favor of the aerodynamic lift and causes the stabilising effect of partial weight on the contact areas to fall to zero and the truly unstable aerodynamics then make themselves spectacularly apparent.

    The surface effect aerodynamics are actually quite complex as they involve getting the correct heave/pitch coupling, with lift and pitch coeffs which change dramatically with just small differences in height.

    But as a general rule surfaces way aft is what you want. The 'tail' is not really lifting much at all, it is there to correct any deviation in pitch angle.

    Also variable weights such as your fuel should go at the total CG so that the center of mass does not move around as you use up the fuel.

    Someone else who has very in depth knowledge of these aerodynamics is Jon Howes. He is a member here.
     
  7. afrhydro
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    afrhydro Senior Member

    cool im at odds between the side sponsons on the ul or the wing from the ul
    or just add some chines to the center section
     
  8. Tcubed
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    Tcubed Boat Designer

    Clarify please..(?)
     
  9. afrhydro
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    afrhydro Senior Member

    like this boat if ya look real close you can see tha aft sponson and the wing of coarse

    and the extra chine from the allison design first short one off the pad
     

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  10. Dan Ellison
    Joined: Dec 2006
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    Dan Ellison Junior Member

    the air at 75 -100 is ALOT different than @ 200 with a 6500 lb unlimited. I think you have a good boat at the speeds you are traveling. I would move around the weight and try different props before adding apendage drag such as wings. Remember what your target speed is and don't get caught up in trying to go beyond the safe design limits, I think you have a good idea with the strakes as hydrodynamic lift on the tail.
     
  11. afrhydro
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    afrhydro Senior Member

    im thinking the same thing dan i just wont be able to bring them all the way to the step or im afraid it will make my prop cavatate a bit so im thinking bring them back in to o about three iches from the step to give the water a second to re hydrate right before it gets released and goes into the prop
    they also may become airborn from 70 to a 100
     
  12. Jimboat
    Joined: Feb 2002
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    Jimboat Senior Member

    Hi Scott - i agree with Tcubed, that the canard can be troublesome on your boat. I expect your problem is as simple as too much aero lift for the speed you're trying to attain. There's a few ways you can change this, as i think we've talked about before. The low aspect ratio ground-effect wings are tricky to balance at all velocities, so it's always a compromise of design. Call anytime to talk about it, Scott. We can always analyze performance in the TBDP software.
     
  13. afrhydro
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    afrhydro Senior Member

    thanks jim i sold the green hull so im back in the red one which was designed to go 70/75
    we did discuss the changes to the bottom i made one time along with a lot of other things on the red boat
    you did run this red one threw the software one time a few years back as it was set then
    those air slots i put in did give me a bunch of stabilty and handeling and now it runs in the 70,s at just past half throttle so it free-ed up the after plane a ton as you can see i might be able to get some more throttle into it but it starts chine walking and so i ease off a bit
    i was thinking of adding some lifting strakes to the center section for more lift and to stabilize the chine walk this boat has always wanted to and rides the best on the tail
    the pictures i have there from scream and fly are with a 22 et and the shaft hieght was 1 " above the pad with a 3 * negative trim its was ok but as you see its carrying the nose a bit to much so im back with the cleavers
    i have a 4 blade dewald soild hub 14 x26 and a 3 blade
    but i also am moving the trim pin in one more hole to allow for more negative trim up about 6 * so i should be able to find the sweet spot on the next test
    i have only run it three times so far since it got put back together
    its hard to compete with the stv tunnels there a good all around boat thats what i want to do with this hull design if i can or ill just build another one in the future
    the problem is in the hyroplane design you have to compromise ride for speed
    after this prop test session ill know more it may be thats the best it will do as a all around use boat for the river
     
  14. Jimboat
    Joined: Feb 2002
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    Jimboat Senior Member

    Scott - it's all FUN!

    3 degrees of negative trim is too much to be used to balance the hull performance. There must be too much aero lift built into the hull at that speed, or dynamic CG is too far fore. You're right, that with any performance hull, particularly those that use significant aerodynamic forces, the design is always a compromise of ride for speed & performance. Call anytime, Scott.
     

  15. afrhydro
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    afrhydro Senior Member

    cool ill call ya later jim
    dont forget now as the afterplane becomes air born the neagative trim will go away even as much as 0 if it all comes together
    thanks talk soon
     
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