What effect does deadrise have on a boat"s performance?

[PAH]

Good Day,
I looked the new 2010 Ranger 621 at the Minnesota State Fair. The bow's deadrise is considerably different than on my 2005 model. What effect does this change have on the boat's handling characteristics?

[Phil T]

A sharp entry (deadrise at the bow) will cut rough water effectively. Extreme deadrise the whole length of the hull makes a boat tender (tippy) at rest, and it will wander at slow speeds. Since more of the hull's surface is in the water, it will also be less fuel efficient.
At the other extreme, think jon boat in rough water.
Actually, one of the most useful hull designs, if you are willing to slow down in rough water, is a semi-vee with a sharp bow to cut through big waves.
It's quite hard to improve on the old Glastron 17 degree deadrise at the stern for overall use. The naval architect that designed that runabout hull knew his business.

[staylor]

....on where the difference in deadrise is located. The 2 most important zones are the last 2-3 feet of the hull by the transom, and the first 2 feet back from the bow after the bow transitions to the actual keel line of the boat. The deadrise at the front of the keel line relates to the ride when the boat is pounding through waves- usually at lower planing speeds. A higher deadrise will give a smoother ride. The transom deadrise effects the ride at high speeds, and the hulls ability to hold a straight line(tracking). A higher transom deadrise will ride smoother and track better at high speeds, but also tends to increase the tendancy to chine walk if the hull has enough power to become fully "aired out". Higher overall deadrise also tends to make the boat more sensitive to rolling when drifting with wave motions and load shift as you walk around the boat. Manufacturers can modify the chine configuration and hull width to try and alter the effects from a change in dead rise- sometimes this works, sometimes not. It all comes down to trading off between ride quality, handling, and performance.
Doug

[ejj]

What is chine walk?

I was in a fiberglass bowrider with a 23 degree deadrise last weekend. When the driven opened it up, the boat wobbled a bit from side to side. (?)

Boat tracked perfectly, and turned on a dime. Mileage would probably be crappy, as it weighs 3100 lbs with motor.

[staylor]

The side to side wobble is chine walk, which on a vee bottom usually shows up at a certain speed- my Starcraft 176 w/150 Opti has chine walk set in at about 56 mph, my old Baja 180 w/175 hp had it set in at 62 and my Checkmate 210 w/225 hp had it start at 69. Lots of seat time in the boat allows you to minimize the walking by what is called "bump steering". In some boats its just a small problem and as the boat reaches a higher speed it goes away. On other rigs it will get worse and worse with increasing speed leading to the boat flipping in a barrel roll if you don't bump steer or back off on the throttle or trim.
Doug

[troutbum13]

can someone explain how you 'bump steer' out of a chine walk?

[flakes]

....on where the difference in deadrise is located. The 2 most important zones are the last 2-3 feet of the hull by the transom, and the first 2 feet back from the bow after the bow transitions to the actual keel line of the boat. The deadrise at the front of the keel line relates to the ride when the boat is pounding through waves- usually at lower planing speeds. A higher deadrise will give a smoother ride. The transom deadrise effects the ride at high speeds, and the hulls ability to hold a straight line(tracking). A higher transom deadrise will ride smoother and track better at high speeds, but also tends to increase the tendancy to chine walk if the hull has enough power to become fully "aired out". Higher overall deadrise also tends to make the boat more sensitive to rolling when drifting with wave motions and load shift as you walk around the boat. Manufacturers can modify the chine configuration and hull width to try and alter the effects from a change in dead rise- sometimes this works, sometimes not. It all comes down to trading off between ride quality, handling, and performance.
Doug

So is the change in dead rise that Ranger made in late 07 a good or bad change in your opinion? I want to say i was like 6-9 inches. not sure on that number

[staylor]

....involves a slight jerking of the wheel with your hand to counter the walking. I steer with my left hand and when the left side of the boat comes up I give the wheel a slight jerk- about 1 inch motion at the wheel to counter the lifting of the left side. You continue this "bumping" motion every time the left side comes up. It sounds hard but you get used to doing this pretty quickly. This is much easier to do with a conventional steering system than with hydraulic steering, and almost impossible to do with NFB steering. Another trick that works very well on many rigs is just to put the boat into a very slight turn to the left when the walking starts- this also tends to minimize the motion. A third trick is to trim down just a little bit when the walking starts, let the hull stabilize, and then slowly trim up a bit. As always, the more seat time you have in the rig, the easier it is to drive fast. If chine walk is really bad, consider lifting the engine up as many holes off the transom as you can, or add a jack plate. The higher the motor, the less the boat will chine walk.
Doug

[Dipstick]

go to www.answers.com/topic/deadrise