Chinewalking Theory

Hi Randy,

    Have just been reading your advice about chine walking and was interested to see that you believe chine walking to be controllable with driving experience. I have spent the last 6 months looking into boat dynamic stability and have found that trying to balance chine walking from the helm a very dangerous practice, chine walking should be known as 'Chine talking' it is the hull saying that it is going to fast for the hull design/setup. It is possible to delay the inception of chine walking with careful setup of the running gear such as raising the engine in some cases raising the cavitation plate up to 2'' above the keel, this reduces the effect the motor torque has on the hull by reducing the moment arm. The added bonus is the reduced wetted area decreases drag and so potentially increases speed if the hull can handle it. One of the most effective ways of reducing chine walking is to run large trim tabs mounted on the hull as wide as possible so that they are in contact when running at close to full speed. The other more drastic option is a twin motor setup, this gives the advantage of counter rotating props and so cancels out the torque affect which is believed to lead to chine walking inception. There is a great paper on planning boat dynamic stability titled 'Dynamic stability of planning boats' written by Donald L. Blount and Louis T. Codega published in Marine technology journal Vol29 Jan 1992. It is a very interesting read and throws up seem really interesting questions that I can't answer. Would be good to see what you make of many of the points in the journal and if you agree with my statements above.

Kind Regards,

Tim

 

Tim, 

How do I say this without offending you. Your deductions and the journal you refer to are straight out of the 1960's. Hydrostreams, Allison's or any other pad V-hull go faster as the wetted surface decreases. Chine walk will increase and stability will decrease as the boat reduces its contact with the water. If it did not, or you used the tabs you refer to, the boat would be slow, end of story. This summer, I ran an Allison XR2002/Merc Drag engine at 129 mph in a standing start 1/2 mile. This combo weighs 1500 lbs with me in it. Trying to balance this boat on a 6" x 10" contact surface is only possible with steering and trim inputs. ALL Hi-Perf. V-Bottoms have this trait. Even a 40' Fountain will chine walk at speed. Chine walking is not a bad thing. It is your boat performing at a level that moves it out of the Bayliner category. The "raising the motor up to 2" above the keel" reads like 1960 Boat 101. The object of a pad hull is to get up on the pad, period. We need to get you to forget what you have read so far and move you to the next level. Mercury publishes a good Hi Performance boat operation manual. The part # is:  90-848481. This was written in the mid 1980's and unfortunately is the best over the shelf literature on the subject. Mercury goes in to quite good detail on the chinewalk subject. I will try to obtain permission to post this manual on Tech talk.  

In closing, just remember chine walk is not bad or a flawed boat, setup, or exceeding the desire dimensions. Chine walk is your boat talking to you. If you give it what it wants it will be controlled and you will go faster. Just like a bike or better yet a unicycle, balance is the key. By using steering and trim inputs to control the torque of the motor against all the forces working against it, pad V-Bottom boats are a very efficient way of travel. By trying to control it by adding tabs or another motor (which will not stop a pad V-bottom from walking) you just end up going slow (so long as 2 motors don't exceed the power the single engine had). Unfortunately most of all the material available out there is so outdated that it's like 1970's computer compared to that as of today. Obsolete.

 

 

Please submit whatever questions you have to IHRTechTalk@yahoo.com.  All questions and answers selected will be displayed on this page as they come in.  Note: though all boaters are welcome, priority may be given to I.H.R. members.  Randy can not be held responsible for any advice given.  Though his information and expertise is second to none, he has no control over what you do with your boat.  It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.

Thanks,
Mark C.

 

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