Chine walk speedboat

Discussion in 'Stability' started by Starholk, Aug 27, 2019.

  1. Starholk
    Joined: Aug 2019
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    Location: Sweden

    Starholk Junior Member

    A6BC3266-65E4-4828-AE07-13B95FE4971C.jpeg C17C713A-0D4A-4052-BAEA-D2C2E492C4F5.jpeg 30928267-AE2A-42BC-BA1E-63B7DEE849B0.jpeg 27962D87-8D88-4ADE-BF67-16C136D0FBB2.jpeg 150438F8-9B13-41CA-B13B-A3B70603755F.jpeg A19E402B-31C5-4DA4-BAFC-D6ED4EE25FB5.jpeg Hello. My name is peter and im from sweden. I bought a italian boat Albatro 28 with 2 mercury 250hp. I have full hydraulic steering and also hydraulic jack plate.

    Its very unstable and when i hit 70mph .its starts chine walk so much that i loose control. When i look at other hulls they have alot more strakes. I think that is the problem. I think the boat is coming to high on the water line. From the center of the boat to the strakes its 60cm. I think its in the air when i drive fast. If someone is kind to tell me what to do? I am very good at fiberglass and can do almost everything. I dont just have the right knowledge to know what to do. I want to drive without risking my life in about 85-90 mph.
    Thanks / peter
     
  2. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Hi Peter,

    Welcome to the forum.

    Sounds like what I know as chine hopping.
    Happens at speed when the engines are trimmed too high.
    Lowering the engines by trimming down eliminates it.
    But my experience is only up to 52 knots and your hull is way more complicated than the Zodiacs I'm familiar with.
     
  3. Starholk
    Joined: Aug 2019
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    Location: Sweden

    Starholk Junior Member

    Thanks. I have tried that too. Even tried with Tabs down. Nothing works. Its like i have to balance it like a bicycle. When you get out of rytm i lost total control. I have driven alot of boats really hard but nothing like this.
     
  4. messabout
    Joined: Jan 2006
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    messabout Senior Member

    It is conceivable that you may have an aerodynamic problem as differentiated from a hydrodynamic one. The configuration of the enclosure does not marry well with the two power heads of the Mercs. At 70 MPH there is the potential for a whole mess of turbulent activity that can influence the behavior of the boat. That includes the possibility of oscillating lift and/or pressure areas.

    If Tom Speer, our resident aero guy, is out there, he might have something to say about this notion.
     
  5. Yellowjacket
    Joined: May 2009
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    Location: Landlocked...

    Yellowjacket Senior Member

    This sounds like classic chine walking, and even at 70 mph that's not likely to be an aerodynamic issue. You should first talk to the people who made the boat. You are not likely the first person who's had this issue with this hull. If you don't get specific directions you need professional help. The person you need to talk to for that is Jim Russell.. Here is a description from one of his pages... Chine Walk Secrets by Jim Russell https://aeromarineresearch.com/publications/chine%20walk.html

    Here is a link to his web site. Jim Russell, AeroMarine Research https://aeromarineresearch.com/about.html

    Your boat has a lot of steps and that complicates the issue. Chine walking is a potentially dangerous thing to have. Just adding strakes may help or could make it worse. You have a lot of v below the strakes, so if you're going really fast you may not be really using those strakes very much. In that case perhaps a lower set of strakes could help. OTOH you have a very deep v and this could be part of the issue. You really need someone who has direct experience in this area that that's probably somebody like Jim. You're in an area where you need real honest professional help and unless the person has direct experience with this same hull it is not something to be getting amateurs involved with. There is a lot more people with this kind of experience on the "Scream and Fly" board, but again unless they've worked on your exact hull model and length I would take any advice with a grain of salt....
     
  6. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    If it is a popular boat, find some owners to discuss the problem with, that way you may benefit from the trial and error of others. It is dangerous to be fiddling with high speed boats, but my feeling is that if small tabs could be installed on the outboard pod, without fouling what is currently there, it might offer a possible solution, but proceeding cautiously at all times ! There is a lot of reverse angle on those strakes, and it could be a case of it oscillating between the concentrated lift generated there, when the boat has risen sufficiently at speed.
     
  7. Ad Hoc
    Joined: Oct 2008
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    Ad Hoc Naval Architect

    Firstly welcome to the forum, and i would ask:

    1) What are the actual - manufactures - performance figures given for this vessel?
    2) Did you try before you buy?
    3) Do you know THIS vessel has actually matched the speeds noted by the supplier?

    I agree with Yellowjacket - seems to have far too many steps and also your first point of contact should be the manufacturer.
    Once going over 60knots on such small boats - it is all about a very very fine balance and any one small thing can upset the balance.
     
  8. Mr Efficiency
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    Mr Efficiency Senior Member

    How common is the reverse angle used on those strakes, that appears to be 20 degrees plus ?
     
  9. Ad Hoc
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    Ad Hoc Naval Architect

    agreed..does seem to be a very high angle....my thoughts too.
     
  10. Starholk
    Joined: Aug 2019
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    Location: Sweden

    Starholk Junior Member

    7E23ED8D-194E-4C8C-B8B0-D30822BC4122.jpeg CAF61214-6B81-41D7-B293-D4E513A80B7B.jpeg ACA6C0DC-F864-40BE-A077-2D3A573A0EED.jpeg BF1B3EE2-DB06-4352-8507-7198923645C6.jpeg 6F600FCA-7CEF-4F52-AF23-F61E16BF0AC1.jpeg Thank you very much for replys.

    Yes i did testdrive the boat but i only checked that it worked. I did not top speed it. I dont think there is alots of this boats but i know they race with them in italy. The boat has a ce-certification on maximum 2x320hp. So its not overpowered. The owner before me bought this boat from the manufactor with this setup. I will contact them today and maybe they have some suggestions on the problem.
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Does it run level with the tabs off ?
     
  12. Starholk
    Joined: Aug 2019
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    Starholk Junior Member

    Without tabs it starts to get unstable at 45mph. I have to start to steering it to balance.
     
  13. Mr Efficiency
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    Mr Efficiency Senior Member

    Ok, you had best consult the makers, the retailers, the owners of similar boats to get a better understanding of whether this is a known issue.
     
  14. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    I see that both your engines are right turn. Do all those boats run engines that turn the same way, or do they have counter-rotating ones?
     

  15. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    The props are counter-rotating, or my eyes are gone.
     
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