Please Help With my Hull And fitting trim tabs

Discussion in 'Boat Design' started by rich99uk, Feb 27, 2008.

  1. rich99uk
    Joined: Jan 2006
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    Location: portsmouth

    rich99uk Junior Member

    Ok Can anyone tell me anything about my hull.
    At present when i open her up the front lifts up quite high its like so close to getting on the plane.
    While i have her opened up there is not alot of boat in water, at the back the water rushes through the tunnels and the botom off the transom.
    There is no water that actualy touches the back of the transom. But it doesnt seem to be on the plane bow is up to high ?
    how is is ment to sit in the water?
    The boat originally was designed for two outboards and i put a inboard in it on a shaft. PLEASE NOT THERE IS NO KEEL ON IT ANY MORE!! I put it on the decided to cut it off as it was to much drag.
    I think i am getting stuck on my bow wave. so i thought about putting trim tabs on but if you look at the shape of my transom it looks impossible any ideas?? Please see pics
    [​IMG]
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    [​IMG]
     
  2. Landlubber
    Joined: Jun 2007
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    Landlubber Senior Member

    What is the boat displacement and engine hp?
     
  3. lazeyjack

    lazeyjack Guest

    good question Lubs, maybe you dont have enuff boogie? trim tabs wont lift her if she wont lift now
    that is a big screw there, need know the bhp and the gear, and the prop size
     
  4. Meanz Beanz
    Joined: Jun 2007
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    Meanz Beanz Boom Doom Gloom Boom

    Mebe a different pitched prop?
     
  5. charmc
    Joined: Jan 2007
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    charmc Senior Member

    LL and LJ are asking the right questions; need more info before anything else: full engine and gear info, hull dimensions and loaded displacement, prop dimensions, etc. Just an observation: There is a lot of rocker in that bottom; she'll always run bow high, IMHO.
     
  6. Meanz Beanz
    Joined: Jun 2007
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    Meanz Beanz Boom Doom Gloom Boom

    What RPM delivers what speed might be useful in determining if the prop is right.
     
  7. rich99uk
    Joined: Jan 2006
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    rich99uk Junior Member

    Thanks for all ur replies so far
    Ok i got a 80 HP Ford Transit engine on a borg warner 2:1 gearbox opened up i do about 12 knots
    ok before i cut the keel off it only did 7 knots the bow come up but not as high. after i cut the keel off it does about 12 knots and the bow rises even higher.
    before i put a shaft on it i had a single 270 out drive leg with the same engine and on this set up the bow didnt lift it used to plow through the waves sometimes digging in them like a scoop.
    However i have changed the wait distribution round the boat completeley i swapped the engine and fuel tank round for starters.
    The Prop i think is 17" x12" its not the same one as the one thats on the pic as that was to BIG
    But please remeber It is a very Heavy boat
    weight wise the fuel tank is at the very back which is a fair size tank the engine is just behind behind where the cabin ends. Not alot at the front bar the toilet.
    What other info do u need i will be more than happy to supply lol
     
  8. rich99uk
    Joined: Jan 2006
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    rich99uk Junior Member

    The engine opened up at full revs is 4500
     
  9. Pericles
    Joined: Sep 2006
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    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

    rich99uk.

    Your posting history indicates you are really committed to making your boat perform. You've been working at it since 1st January 2006 and I admire your persistence. You do seem to need more thrust to get onto the plane, once there you could perhaps throttle back a little to maintain a reasonable economy. Your earlier weight estimate was 2 tons, but now you write that the boat is very heavy. How much more than 4500 lbs?

    You also mentioned the boat was designed for 2 outboards, then it received a Volvo 270 I/O leg. Do you know the HP of these previous installations? Have you tried "kicker" assistance to get over the hump? The temporary use of a second more powerful "kicker" could help with your evaluations.

    Regards,

    Pericles
     
  10. rich99uk
    Joined: Jan 2006
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    rich99uk Junior Member

    The boat does weigh 2 ton i thought that was heavy for that size may be it isnt i dont know.
    Yes when i bought it it did have a splash well and was ment for two outboards which were rated at 100hp each. but i never saw how it went with them on it.
    then i modified it to have a 270 leg then i changed it again to shaft.
    I agree it does need a bigger engine but untill i have finished saving :) i was trying to make the best of what i have.
    Can i as what you mean by kicker ?
     
  11. Pericles
    Joined: Sep 2006
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    Pericles Senior Member

    The kicker is the "get you home" or trolling outboard hanging on the transom. Add more thrust and see if the boat planes. :D

    Regards,

    Pericles
     
  12. lazeyjack

    lazeyjack Guest

    quite simply put you a re way down on bhp
    weight of the eng and all is killing it

    Look this boat as you have it will never get up

    you have 2 choices
    one
    just put up with disp speed-- a crawl
    or
    2 chuck that useless engine away and go back to say a 140 4 cycle eng outboard, in which case you will beway over capitalized
    or 3
    sell it to some dumb bugger and buy a real planing boat
    sorry me lad, I am not being rude, just practical
     
  13. Meanz Beanz
    Joined: Jun 2007
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    Meanz Beanz Boom Doom Gloom Boom

    Does the engine work hard to hit the 12 knots? If it has plenty of torque maybe it can carry a prop with a flatter (?) pitch. Not sure that's the right way of saying it, but it may be worth a conversation with a prop expert. From what little I know its a very complex subject working out the ideal prop for the engine hull combo but it can make a massive difference. Definitely a job for a pro IMO.
     
  14. Meanz Beanz
    Joined: Jun 2007
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    Meanz Beanz Boom Doom Gloom Boom

    Or mebe LJ is right, just not enough grunt.
     

  15. Landlubber
    Joined: Jun 2007
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    Location: Brisbane

    Landlubber Senior Member

    Listen to Lazyjack, but with caution as his first two ideas are NBG, the 3rd idea is great!

    No good flogging a dead horse mate, reinvest and start all over again, I am sure that you have learned a lot from this exercise, apply what you have learned and get on with it.
     
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