Fast, Small, Boat Designed Around Mercuiser 140

Discussion in 'Boat Design' started by jlclar09, Jul 2, 2013.

  1. jlclar09
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    jlclar09 Junior Member

    For those trying to come up with the weight, mine has the M/R outdrive, from what I understand thats pre alpha...
     
  2. tunnels

    tunnels Previous Member

    You are going to get al kinds of ideas and even a few silly answers but at the end of the day design your own boat !! its not that hard ! :idea::(:confused::p
     
  3. PAR
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    PAR Yacht Designer/Builder

    Spoken like someone that's designed lots of high speed powerboats. Small powerboats that will go fast, need a little more then a good guess. Balance on these will be critical, or bad manners that can cause serious injury can occur. The best option is a set of plans, where the balance is worked out.
     
  4. powerabout
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    powerabout Senior Member

    MR had the first round of updated lower unit and top and bottom housing design, so its way stronger the the old 1 drive.
    You cant break a 1 drive with a inline engine regardless of which model it is.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    So he could be shaken, but not stirred ? :D
     
  6. powerabout
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    powerabout Senior Member

    I put them on a pipe on the ground to find the CoG then watch what happens when someone drives or I drive and get vid of it with known trim angles at known times if it not obvious from the vid
    But I dont design them just race them.
     
  7. tunnels

    tunnels Previous Member

    I designed , built but some one else drove the tunnel boats !!
    like what you just said but I used a one inch wide black plastic tape set at a level line fore and aft and found the centre and another vertical tape
    the boat we set to run at different trim angles and we used a two way radio with the driver speed, rpms and trim settings ,. 3 to 4 degrees is the ideal trim of most any hull where it runs most efficient at ! also used the video and laid down on shore close to water level and zoomed in to look at the spray and what was happening at all and any angle that way can re run the tape and still frame and etc and on a big screen and the computer can really get some amazing footage and close ups . you can learn so much by doing these things !!, the next move was a fibre optic down inside the tunnels so watch and see what happens in there but the guy sold the boat and moved away . there's so much we just guess at and never really know for sure . :D
     
  8. powerabout
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    powerabout Senior Member

    all true Tunnels
    he who tests most usually wins
     
  9. Jimboat
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    Jimboat Senior Member

    John - if it is a performance boat that you are looking for, remember that all such hulls are quite sensitive to weight and power. So you should pay particular attention to these items too.
     
  10. jlclar09
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    jlclar09 Junior Member

    When planning the design, should I place weight in the front of the boat to get it ballanced? Does the boat need to be balanced around the C/G or should the boat be rear heavy?

    I realize that I will need to calculate the volume needed to displace the water for bouyancy with this heavy engin but is there a width to length ratio that needs to be maintained? I think I have rulled out the tunnel hull design in favor of the Q-boat charachteristics. i think it would be eaiser to design/build with the existing power plant. With this in mind, should the engine be above or below water line or somewhere in between?
     
  11. Jimboat
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    Jimboat Senior Member

    Good question, John. Best to consider the Dynamic balance of your hull that considers all the acting forces throughout the operating velocity range. (The acting forces change magnitude and location significantly at different velocities). Balancing static weight of the hull around the static CofG is only of particular interest when boat is at rest (freeboards, etc). Performance/handling is significantly influenced by the Dynamic balance of the hull at velocities.
     
  12. jlclar09
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    jlclar09 Junior Member

  13. 805gregg
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    805gregg Junior Member

    Find a used boat with a bad 4 cyl engine and just repower
     
  14. tunnels

    tunnels Previous Member

    Yeah Baby !!!! Thats me

    Allison boats has a really good reputation and if you look really closely at there hulls underneath there a few tell tails as to how they have achieved good speed and good handling and minimised hull friction in the process .To have a fast boat you have to have a fast motor to go with it the two need to become one , the set up and making everything work properly is a gift and most important is the fine tuning .:D:p
     

  15. PAR
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    PAR Yacht Designer/Builder

    The Allison hull form would be easy to replicate, though don't try to mimic the odd strakes and strippers, just use a couple of straight ones on each side. The hull shown wouldn't be able to carry a 3.0 and MR, just not enough displacement, but this could be sorted with an accurate weight study and appropriate adjustments to hull volume. The form itself is a classic monohedren, though it does have stylized aft sections to the chine and strakes. Leave these styling features alone, as poorly placed, they'll cause trouble, though designing a similar, more voluminous monohedren, shouldn't be too difficult, if you have these skills.
     
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