Starflite - How fast when chine walk?

[hemibeep]

Trying to determine what speed a starflite starts to chine walk at?

Yes a loaded question..

225 merc. 25p trophy plus 4bld. 6300 rpm. speedo says 65. about 2" below pad, 5" setback. 3/4 tank of gas, 400 lbs of people.

I am getting closer to figuring it out. Trying to decide if I should add more setback without rebuilding transom. It seems very strong, but a few soft spots up front by footrest bar and under the battery.

If I add more setback, will the transom expolde if weak, or crack and show signs of stress slowly? I don't want the motor to pass me on the lake.

 

[merc245]

What type of steering is on hand & is there solid mota mounts are couple of questions that need answered first.

With solid mounts, tight dual steering and couple weeks in the seat I really never had a proplem with chine walking at any speed!

If you add more setback build yourself the largest steel over the lip bracket that could possibly also tie in forward to the front of the well too and then just get it powdercoated to clean it up.

The transom won't explode it will just crack and keep on cracking and the mota will move to and fro,to and fro.

 

[hemibeep]

dual steering, I have to check on the mounts. It is not scary, just a slight rock back and forth. I rode in a boat with a pad a looong time ago, it kind of reminded me of being up on a pad and trying to balance. I am still learning the boat, and trying to figure out how far off the 65mph is on the dash speedo. Someday I will borrow a GPS.

 

[ezstriper]

water conditions and trim will change that...Rob

 

[illMATTic]

mine starts to get loose at 65 gps. I am running the same setup but more power. I am just used to it from the years driving my predictor so I am able to drive through it.

you just have to be in tune with what way its going to walk and counter steer just right. my friend said its like i go into a trance and don't see anything but the boat.

more weight will raise the speed that it gets loose.

 

[Jimboat]

Chine Walk

hemibeep - the speed that a boat will start to chine walk is predictable, but it depends on many factors. You may wish to check out the article on "Chine Walking" .

Chine walking can arise with most high performance vee-hulls. 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. When that surface becomes sufficiently small, it becomes very tricky to “balance” the hull on its vee or pad. The result is a rocking of the hull from side-to-side, from port-chine to starboard-chine, back and forth. 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.

So the hull will rock from port chine to starboard chine – back and forth – with more motion and faster motion. This is called “chine-walk”. 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.

Check out the Chine Walking article in HotBoat magazine.

/Jimboat

 

[rowdy1]

Mine starts to walk about 65mph if I hold it there, or creap up to that speed. If I stand on it @ about 35-40mph & blow right past 65mph, the boat rocks about 3 times before it comes out the other side, rock solid.
Thats with hyd. steering, solid lower motor mounts & 6" of setback. Thats also with a motor that measures 48" from the floor to the top of the cowling.

 

[JUPITER PULSARE]

You already answered your question in the opening post...2" below the pad may be too low....increase your setback to 10", raise the motor so the propshaft is even with the pad, make sure you have low water pickups to retain water pressure, make sure you steering is tight with very little play...solid motor mounts will also help. This alone may alleviate your chinewalking altogether on a Starflite hull and your speed should creep into the 70's! You may need to go up in prop pitch to 26/27.

 

[merc245]

{"My friend said its like i go into a trance and don't see anything but the boat."}

I think it as your balancing an egg out on your bow and always anticapating one move ahead to keep it centerd.With a nice 1+ ft chop the better.

 

[Mr. Buss]

after installing solid mounts and jackin' up the motor, it was like night and day for me, but there is no replacement for good ol'e fashion seat time, heck if gas prices stay down, we all can get more seat time!!!

 

[kingsbiship]

I had the same problem with my Predictor! Raise the engine and it'll go away... almost
totally!

 

[hemibeep]

Funny thing is, It does not feel threatening. Just a slow little rock. I'll try to raise the motor more, and I finally bought a GPS. I'll keep playing.
thanks

 

[Mark]

I am 2" below the V and I don't have any chine walk either. Solid up to mid 60's and then just a slow rock approaching 70 MPH. Unfortunately...that's where she runs out of jam.

 

[aaronmt]

Seat time!!!!!! The first day I took mine out it was scary as heck at 64 with a 225 yami mounted directly to the transom. After a summer of set up and messing with it I was neer 80 without a trace of chine walkin. My allison in the mid 90s is a whole differnt ball game to drive.,Aaron