PDA

View Full Version : Chine Walk



Vern S
05-21-2001, 09:23 AM
My brother is running a 79 Sleekcraft tunnel. It has a 300 Promax, CMC jackplate with 12 inches of setback. At about 67 mph as you start to trim it out the boat develops what I think is called chine walk, the boat rocks from side to side. Not a good feeling. Can someone tell me what causes this and how to fix it?

drewvir
06-07-2001, 08:06 AM
Vern,
Check to make sure all the slop is out of the steering cables(I assume u have 2 cables)if that doesn't help go to screamandfly.com the guys there will help
drew http://free.***boat.net/ubb/biggrin.gif

BillyD
06-14-2001, 11:57 AM
Chine walk is pretty rare in a tunnel hull. I run a 1977 20' 2" SleekCraft tunnel with a Merc 225 Pro Max. Impossible to make it chine walk unless I'm trimmed out WAY too much for best top speed. Are you sure top speed is not obtained at a lower trim angle before this starts? Your rooster tail for best top speed should be low and long, not short and high (the later looks cool, but you will find that it is actually much slower with that much trim unless your entire setup is way off). I suspect your real problem is that heavy 300. At 467 pounds, it is MUCH heavier than that boat was ever designed to carry. With my 225 ProMax (375 pounds and about 11" of setback), the water is within a few inches to the top of my transom at rest. I hate to think how little freeboard the boat must have with that big 300 on it. A four blade prop (Merc Trophy maybe?) can help stop chine walk, as can push-pull steering with absolutely no slop (but hydraulic steering would really help with control and steering torque feedback on that rig). Does it have the Sportmaster gearcase (pointed nose cone)? If not, it should. With that much weight, less setback would probably help (0"-6" max). Almost 500 pounds mounted 12" back is asking a lot of that boat. Setup correctly, however, it should be "scary fast". Finding the right transom height can also help stop chine walk. Too high or too deep can cause some weird problems on fast boats. Experiment with several different trim settings at each of three or four different jack plate heights and find the best "sweet spot". For hole shot (and skiing), all the way down and all the way in will almost certainly be the best (then trim out and raise to the sweet spot for best top end). Good luck.

WS6_Keith
07-20-2001, 05:42 PM
Typically not a problem with a tunnel. I'm not familiar with that hull design, but I have seen an STV (Mod VP style tunnel w/center sponson) "chine walk" when trimmed out too far. Basically, you get so much trim angle that you over stuff the tunnel until it pops up one side to blow off the pressure, then that side settles and the other side does the same.
If it's true chine walk, when the side comes up, turn into it slightly. Port side comes up, feed in some port steering, then it will go starbord, turn starbord. Subtle. When my dad used to drive J-production (back in the day), that was just something to deal with on the old Allisons and Actions (V-bottoms).

dragally
07-20-2001, 08:12 PM
I have an STV with hyd steering and there isn't any such thing as chine walk. Check your steering and motor mounts. I dont know if the big pig has solids or not but if it doesn't get em. Try a bravo thru hub 26 or 28 on that setup. I have a friend that has one and thats what ended up being the best prop for it. Good luck
dragally

WS6_Keith
07-22-2001, 07:17 PM
Dragally, if you trim it up enough (too much) it will act like it chine walks, even though it's not REALLY a chine walk. Even Roark has said this. In the STV, signs of overtrim are first a porpoising effect, then this "chine walk" as the tunnels spil excess pressure.
We have run a Mazco 29 up to 109 with a 2.4 EFI Bridgeport.
http://www.speedcraving.com/keith/stv1.jpg

dragally
07-23-2001, 08:39 AM
You must have a setup problem cause mines been 117 w/mod 260 and it's smoooooth. Now why are we showing pictures? http://photos.classifieds2000.com/photos/internet/generic/63/1730563.jpg

dragally
07-23-2001, 08:41 AM
Damn,I goofed.
http://photos.classifieds2000.com/photos/internet/generic/63/1730563.jpg

WS6_Keith
07-23-2001, 05:19 PM
Drag, I think you're missing this: you can MAKE the boat do it...it doesn't want to. If you trim it out way too far, it will exhibit that instability. During normal running you shouldn't get to that point. http://free.***boat.net/ubb/smile.gif

dragally
07-23-2001, 06:16 PM
You're right. I had a brain fart. Oops, can I say that? Mines for sale if ya know anybody interested.
Dragally
PS: I also talked to Roark and he told me ifn it bounces side to side (chine walk) ya got it trimmed too far.

WS6_Keith
07-24-2001, 07:43 AM
Drag, looking at your pic there, do you have a jack plate on there? If so, are you running a 20" or 25" midsection?

dragally
07-24-2001, 01:23 PM
Keith,
yes it has a detweiler on it. I'm runnung a 20 mid. I dont really use the plate for anything except beaching.
Dragally

WS6_Keith
07-24-2001, 05:54 PM
Gotcha. I had considered running a 25" c-section with a plate once so I could ski and rat race, but to get the motor up that high really puts the COG up there.

dragally
07-24-2001, 09:19 PM
Hell man I ski behind this boat just fine. Damn thing wants to pull my arms off tho.
dragally