18 Handling problems

[Madcow]

I have a 1979 18 Classic. It has a small block Chevy with a Bravo shortie (2"). When I run over 70 MPH with the boat it wants to rock frim side to side progresivly worse each tilt to the point where I have to slow down or the thing seems like it willl go out of control. Anybody else expirence anythink like this?

[Cuda]

Do you have hydraulic steering?

[Madcow]

Do you have hydraulic steering?

No, internal power.

[Last Tango]

What you are experiencing is called "chine walk" and EVERYBODY with a Donzi has that issue eventually at some speed. It is not a design flaw. It happens to every sport boat with a deep V configuration.
It has to do with the speed at which you are traveling, the angle of trim lifting the boat out of the water, and the basic fact that you have no hull left in the water on which to balance the boat. Basically the hull is "hunting" for a stable platform on which to ride. Mechanical steering may make the onset of chine walk come sooner since there is more play in the steering/drive. However, even hydraulic steering has a limit since the issue is how much hull is running in the water.
The "cure" is to either drop the drive trim (lowering the bow and putting more hull in the water), or lower your speed (same) , or put the trim tabs down and create some more surface area for the boat to balance on (if you have them).

[MOP]

A touch of tab until you are through it works on some, what also works with many is to put the boat into a slight turn not enough to scrub speed but to get through the walking. Hydraulic steering or a steering stabilizer will pretty much get rid of it.

[osur866]

I have similar set up, full hyd. steering will help, prop selection will help, and as mentioned running a tad too much trim will also induce chine walk a tad more trimmed in/down will stop seat time on learning how to counter steer will also stop before it gets too wicked. Steve

[A2VeeDub]

Same as everyone else said. Different combinations of tabs and trim will have different effects.

I find that I can pretty much control it with trim alone if chop is not too great. I speed up with trim at near full negative. As I reach full rpm I start trimming up as much as the conditions will allow. If it starts walking too much, trimming down a little will usually get rid of it for me. I am running between 65 and 70mph on an 18C.

[gcarter]

My old Minx w/a M+ would chine walk badly from cruise until I ran out of throttle.
W/a Hydro Q4, it was rock steady until I trimmed up to about 3/4.
Amazing what a difference a prop makes.

[mphatc]

Madcow,

My Corsican has a Bravo and the same hull bottom as your boat. The stock power steering spool valve has a huge amount of free movement , the Bravo prop is much further behind the boat than an Alpha or a Volvo, so side to side movement will cause chine walking very easily on this small hull. .

Experiment with props. A four blade will likely be more stable, I've been running various 3 blades and did run a labbed 4 blade Hydromotive that was lent to me, it made a huge difference!

Make sure that your Gimbal ring is tight and eliminate as much clearance in your existing PS set up, play with props before adding external PS.

Mario L.

[Madcow]

I did try a Quad-4 this weekend. Can't say I noticed a lot of difference. Seemed that it is worse on dead flat water. Everything in the steering is as tight as I can get it, however it is cable steering and ther is a very small amount of play, and at that speed that may be enough. Has anyone had sucsess with steering sablizers in high speed applications?

[osur866]

These are my steering stablizers and they work well, if your running in the 70's I'd very much consider adding full steering on it you won't be disapointed if you choose to, will not totally elimiante chine walk but should help. Steering with a lil less trim and the right prop that works well on your boat will be the ticket. Think you will find the right 3 blade will work the best for you, least that was my experience. Steve

[3rdDonzi]

I have similar set up, full hyd. steering will help, prop selection will help, and as mentioned running a tad too much trim will also induce chine walk a tad more trimmed in/down will stop seat time on learning how to counter steer will also stop before it gets too wicked. Steve

Steve,
I'm quite familiar with and understand the physics of countersteering motorcycles but could you explain how countersteering pertains to boats????
3D

[BlownCrewCab]

Steve,
I'm quite familiar with and understand the physics of countersteering motorcycles but could you explain how countersteering pertains to boats????
3D

Pretty much the same concept, when the boat starts to lean left, counter-steer with a small amount of right steering, then when it starts to lean right counter back with a little left steering. you have to be pretty quick with good hand/eye coordination.(and depending on how fast your boat is-Ballz )

[osur866]

Yep Blown described it, think of it this way, if you took your boat off the trailer and dropped it on your driveway it's going to fall port or starboard, as it starts to fall a quick steer the oppsite direction will counter act and balance the rounded hull and keep it flying straight, yes it does take a good bit of concentration and you do need to be quick but if you catch the chine walk early you stop it before it gets too violent, once you get used to how much left or right counter steer it really isnt as hard as it sounds, it has gotten a few looks from my passangers when they see the wheel getting jercked left and right as the nose flys straight

[3rdDonzi]

Ok. I got it.Just a different use of the word countersteer.
You are refering to steering the boat counter to the way its wanting to go however we always steer in the direction we want the boat to go.
Countersteering motorcyles refers to actually turning the handlebars in the opposite direction than we want to turn in order to create "lean" for the actual direction of the turn.
Same word, two different but correct uses.
3D