Chine Walking

[davedpc]

Refering to the previous post on the Sealine 41/42/43 have i always had the wrong understanding of chine walking? Most flybridge boats i have driven with top hamper lean into a cross wind which can be corrected by extendind the t/tab on the opp. side of the lean. I understood that c/walking was the unpredictable direction the boat sometimes takes when coming back into the water over a wave or some other boats wash. I once had a phantom18 [ring] with a 200hp o/b and at speeds over 50 knots without the help of the bow water ballast tank would be unpredictable which way it would turn when re entering the water off a wave depennding which chine 'bit' first. The boat was definitely overpowered. This is why it was named Ex Lax.

 

[Wiggo]

My understanding of chine walk is where the boat lifts so high out of the water that it starts to fall over. As it tips one way, the chines dig in and flip the boat upright, but because it is too far out of the water, it carries on the other way and the boat flops from side to side. A bit like porpoising, but side to side rather than fore and aft.

 

[oldgit]

15. Chine walking and loss of steering control. At high speed, boat lays over on its side. Trim tab inputs result in extreme and unwieldy responses. The causes of this are complex, but well known. The main reason this occurs is that the designer didn't know what he was doing, and the builder didn't bother to test the performance, or bother to correct the problem. He gets away with this by ascribing the problem to "operator error." Large numbers of boats are affected with this problem. Courtesy of www.yachtsurvey.com.

 

[landlockedpirate]

Like you I didnt really know what Chine walking was, untill I tested a Zodiac RIb.

Boat was about 6m with the maximum recommended size outboard, it had seats like bar stools (rather than jockey or bench seats) and accelerated smoothly to just over 50kts.

At this point it started to rock from chine to chine, it scared the sh*t out of me, it felt totaly out of control and because of the seat configuration I felt like I could fall out at any momment.

Zodiac are a big manufacturer, with millions spent in R&D over the years-so why did this boat Chine walk ?

Could the outboard have been incorrectly positioned on the transom?

Mark

 

[HattonEdge]

The boat creates lift from the chines, and at speed - particularly over-speed from a design viewpoint - one chine lifts, but unsustainably, and the boat drops over onto the other side where it is picked up by the opposite chine, ad infinitum. A well designed boat like a Sunseeker XS, even with 880hp, will run with sustainable lift even at 65kts

 

[Greg2]

Experienced the same thing in an Avon Searider - very well known make and lots of experience building them. Also reputed to be good seaboats so not sure I understand why the chine walk. Is overpowering a factor?

 

[KCook]

Chine walking is common on OB powered bass boats here in the US. Though it only happens in one of the higher speed ranges. So long as it is mild our bass boat operators are used to it, they can compensate with carefully timed steering input.

I/O boat operators are not so accepting of chine walking.

Note, no chance of chine walking with catamaran designs.

OB boats can usually have this fixed by adjusting the mounting of the motor. As already mentioned here by Mark. Of course I/O boats don't have that luxury. Prop selection can affect chine walking to a degree. But if the boat has it bad, may as well trade it in for a different boat. Or go slower.

Kelly Cook