Twin Jet Boat Build

Discussion in 'Metal Boat Building' started by Sms986, Oct 15, 2020.

  1. Sms986
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    Sms986 Junior Member

    ..I wouldn't say all of them lol.
     
  2. Sms986
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    Sms986 Junior Member

    Here are some pictures of one of the engine/pump assemblies
     

    Attached Files:

  3. Sms986
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    Sms986 Junior Member

    And a few cad drawings of the proposed hull
     

    Attached Files:

  4. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    I had an RZ350 Yamaha bike for seven years.
    Rebuilt the engine the second day I had it.
    New reeds and pipes.
    Ridiculously fast and light.
    I can't believe I survived.

    What's your thesis on?

    Thing about custom jet installs is getting it too work optimally.
    The smallest little thing can set them off.
    Are they indeed Hamilton jets?

    But this project is a recipe for FUN!
     
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  5. Mr Efficiency
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    Mr Efficiency Senior Member

    Sounds like some women, mercifully few, of course ! :D
     
  6. Sms986
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    Sms986 Junior Member

    My thesis is a on separation control via ground effects for road vehicles (CFD).

    I'm not too worried about optimal performance, good performance will be good enough for me!

    No, they are not Hamilton jets. They are the stock yamaha gp1200 jets
     
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  7. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    With such high jet losses to begin with (up to 50%), a misplaced anything could lose you another 40% and your going nowhere fast.
    I'm not referring to worrying or even concern about efficiency, just trying to keep it from being a dog and waste of money and time.
    Replicate to original instal configuration and hope for the best.

    I guess you are familiar with the changes this year in F1 racing regarding ground effects.
    They are essentially back on in an effort to clean-up dirty air for the following car.
     
  8. Sms986
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    Sms986 Junior Member

    Lol, it sounds like you are an Aero guy. I'm still an Aero "kid." I also honestly don't follow the F1 as much as a lot of fellow students do. I am much more interested in passenger cars and such (and boats). I actually wanted to be an IC engine guy but certain people who I will not name here are making the IC engine dream less practical.

    I planned on doing some CFD on this hull (basic RANS is all I am really comfortable with at the moment) to see how these will do. I may publish a paper on it. If I do, I'll get much better insight on the performance. May be able to make my own design. But nonetheless, nothing will be cut in stone until I run some simulations. Possibly a comp between the ski hill and the boat hull. I do think these will work fine though, as the pumps are flush mounted on the bottom of the ski with no dip or spoon fore the intake grate.
     
  9. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    You may get a kick out of this:
    I put an air dam made out of a strip of old conveyer belt on my Datsun 510.
    It hung straight down and straight across from a pair of 2x4's bolted to the bumper mounts.
    It was an ice racing car but I drove it for transportation. I was young.
    The dam came down to within two inches of the road.
    Didn't go any faster (95MPH in third or fourth gear, didn't matter),
    but the ride stability was astonishing, felt like a 2-ton Cadillac.

    Thanks for indulging the thread drift and my apologies.
     
  10. Sms986
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    Sms986 Junior Member

    That is awesome haha.

    I always get a kick out of the tuners with huge wings that create 10x more drag and will never get their cars fast enough to see the beneficial downforce (on a front wheel drive car anyway lol)
     
  11. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    So, did you get your thesis done?

    And, how's the jetboat coming along?
     
  12. Sms986
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    Sms986 Junior Member

    Unfortunately, the thesis is not yet done. I had some issues with the CFD software that were making some wild results and I just traced down the source and got it fixed over the weekend. Now I have to redo my mesh sensitivity study (yay)

    Regarding the boat, the project is basically on hold until I can meet with the hull fabricators to go over the design in detail.

    I'm also looking for a more sturdy water intake assembly than the factory Yamaha one, and on top of that I found that one of the two engines I bought had a hole in the bottom of the case.
     
  13. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    Huh.

    Well, that'll slow things down.

    How about starting out with just one jet in the centre?
    You could test the new style intake assembly, if it works,
    twin the install.
    Or not.
    Standing-by...
     
  14. Sms986
    Joined: Oct 2020
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    Sms986 Junior Member

    I actually got in touch with the guy who builds intakes just now. So that's under way. He's sending me some pictures and dimensions now. Also, the $1500 per pump was in canadian dollars...so I just knocked off $700ish from my original estimation!

    The problem with testing with only a single jet is that I would have to taper the keel so that it is flat (horizontal) in the middle at the transom for a single jet. With two jets, I can have the 8 degree keel go all the way back to the transom. If I would do that I would need to have the hull overhauled after testing with one jet-if even possible.

    Rebuilding the engine is no task. It would take a day start to finish, if that. The engine issue is more of frustration than a hinderance.

    People buy something, break it, then get upset that it's lost almost all value because they broke it.

    So, instead of accepting the loss, they try to sell it off to some unsuspecting sucker (me) and get all of their money back, passing along their rightful losses to someone else.

    In my opinion that should constitute jail time. It's such a petty little crime. Selling something "As is" should conform with "As advertised."
     

  15. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    I hear ya.

    I'm looking forward to seeing this project move ahead... at 60-knots!
     
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