What can be done to prevent chine walk? I was thinking that I'm getting too much stern lift. Is this normal for these hulls above 100? So far, the only thing that stops it is putting the tabs down about an inch past being parallel to the running surface. With the stock engines, drives and props I ran it tabs up drives out hammer down and never had a problem.

A lot of Fountains come from the factory with spacers in the trim tab ram to keep them dragging slightly for this very reason. Loose is fast...

Chill - chine walk is pretty common on performance hulls like yours.

As the hull accelerates, lift increases and the wetted running surfaces that are required to support the hull are reduced (more Speed = more Lift = less Surface). As the speed increases throughout the velocity range, the hull often gets to a point where the lifting surfaces become very much reduced and the hull is now "balancing" on a small area of the vee-portion or the "vee-pad" of the hull (or aftward sponson pads on tunnel hull). When that surface becomes sufficiently small, it becomes more tricky to "balance" the hull on its vee or pads. The result is a rocking of the hull from side-to-side. This rocking can tend to get a little more extreme with each motion, and so the "balancing" must then be provided by additional driver (steering/throttle/trim) input in order to maintain the hull in a balanced state.

With some driver input, the condition can be stabilized. With changes to hull setup and/or changes to the driving technique the condition can be alleviated.

Chine walking is predominantly characteristic of vee-hulls with deep Vees (more deadrise), hulls with deep or narrow running pads and hulls, with a Veed pad or no pad (straight vee). These bottom designs are just more inherently difficult to balance at higher speeds. Another contribution to chine walking can be seen at higher speeds from "propeller slap" (usually seen more with props of fewer blades). As the prop turns, each blade enters the water and another exits the water. This irregular in/out of every blade, changes the dynamic forces at the location of the propshaft, repeatedly putting an imbalance on a hull that is trying desperately to balance on it's vee or pad, and ultimately initiates chine walking.

Setup of your hull and driver "seat-time" are the best solutions to the problem. Usually an alteration to the hull, or hull setup and/or modification to your driving methods (read seat-time) will improve the problem.

Some established steps toward minimizing chine walking include:

Also, see full article on "Chine Walk"

/Jimboat
AeroMarine Research
'Secrets of Tunnel Boat Design' book
'Vee Pad Design' paper
'Tunnel Boat Design' software V7.10 with "Vee Hull Design" & "Porpoise Analysis"

usually on 32"s

There's things with the setup that will make it better but at a 100 plus its gonna take some driver input.