Deadrise questions

[KC8QVO]

How much of a difference does a few degrees really have on the deadrise of comparable boat designs? Say, from 16-17deg to 19-20deg? Would the shallower deadrise angle really be noticeable in roughness of ride/bounce in chop?

I know there are other factors, but negating those affects and figuring the boats are identical except for the dead rise...

 

[Bob_VT]

Re: Deadrise questions

Well deadrise is one factor and a steeper one will cut the water different (notice I did not say better). The ride of the hull and how it handles rough water depend on design, hull material, weight, loading....... there is always a tradoff. I zip around in a 16' Starcraft aluminum boat. It can ride rough but not where near as bad as a tri-hull. I also had (Past boats) a 23' marathon cuddy cabin that ALWAYS rode smooth but it was a handfull in shallow water.

With everything being equal the higher deadrise number will ride better in the chop. a small 2-4 degrees would be negligible but a hull with a 24 degree will absolutely out-ride a 16 degree in the chop.

73's
KB1JOI

 

[superbenk]

Re: Deadrise questions

I believe the higher dead rise angle will also cause more roll. I have a fairly narrow beam with a steep dead rise and my boat will roll significantly, but cut through chop quite well. In all honesty, I'd love more beam and a more stable ride over what I currently have.

 

[JoLin]

Re: Deadrise questions

Desirability depends on where you boat and in what conditions. Lake, Great Lake, ocean, etc? I boat in a major bay that's always choppy, and can get snotty enough that the 40-footers head for home.

My 24' Chris*Craft express had a terrific hull design and 22 deg. deadrise at the transom- it was the best rough water boat for its size that I've ever been on. My Four Winns has only 17 deg and the difference is very noticeable on a rotten day. The FW will pound if I push it- the C*C never did. Since I don't go out in truly lousy conditions, however, the practical difference between the two isn't enough to make me miss the other boat.

 

[Mischief Managed]

Re: Deadrise questions

All things being equal other than deadrise, the boat with the deeper deadrise will always ride more smoothly. It was also have a longer time to plane, use more fuel, draw more water, be less stable at rest, and have a higher minimum planing time. It may also wander more at displacement speeds, but that I'm not sure of.. There are trade offs when it comes to deadrise, otherwise all boats would have deep deadrise...

 

[Home Cookin']

Re: Deadrise questions

actually when you use deadrise as a single number ("deadrise of 17 degrees") it is a completely irrelevant number as to how the boat rides, becuase that number is deadrise at the transom. How the bow approaches, cuts or rides over, recovers and sheds water is way more important. There's deadrise at the bow waterline*, all along the hull, and finally at the transom. There are deep V's and semi V's but even they have varying rides depending on the width at the waterline.

A deeper keel won't slide on turns but some flat boats have chines to compensate for that.

So not that the comments above aren't true as far as hole shot, handling, stability, etc. but that one number really isn't what gives the whole picture.

And then there's a classic boat called a "deadrise" with a perfectly flat bottom--no deadrise at all!


*meaning the waterline while underway on a plane

 

[dingbat]

Re: Deadrise questions

actually when you use deadrise as a single number ("deadrise of 17 degrees") it is a completely irrelevant number as to how the boat rides

Yep... all things equal, the heavier boat will ride better as well.