Deadrise measurement

[Aaronhl]

Specifically for outboard offshore style powerboats style approx 20-30 ft in length,

What would be the approx deadrise in the bow, middle, and transom areas?

How much concave (from keel to chine) is used in each of these three areas?

Are these traits an important part of the compromise on speed, handling, and stability? (being able to go fast over waves)

[Aaronhl]

48-50 degrees?

[Jim Speros]

Most boats have a deadrise at the transom of 22 to 26 degrees. 22 is a popular deadrise. 26 is a deep v.

How much it varies moving forward varies with builders. Your Velocity pictured is a stretched, stand up version of the 22. The 22 has a long flat pad and a 22 degree deadrise that extends pretty far forward. The 30 Velocity progesses to a sharper deadrise moving forward. I enjoyed how both run and are different. The 22 runs flat and kind of hard but carries weight extremely well is is fast. The 30 can run on its tail in calm water and can be laid over with a lot of cut in the bow to run well in Rough water. They are different they most other deep V's.
Early Fountains were similar. Cigarettes Sutphens Pantaras Carreras all have a deeper V ride smoother but generally power for power are not as fast.
Step bottoms are entirely different.

Just a general opinion for many years of opertating many different brands. I have run and raced the velocity and fountains I mentioned. I have also raced a 29 mirage, 31 and 34 Sutphen, 26 Corsa, and a number of step bottoms as well.

[Aaronhl]

Thanks for your input Jim
So the 22 Velocity has 22 degrees through the middle of the hull,
I am wondering what the bow entry deadrise would be, maybe it varies with builders but would 45-50 degrees be a rough idea when most of the rear deadrise is in the low to mid 20s?

[Jim Speros]

I guess that is a fair assumption. Not sure how it translates into anything useful.

[Aaronhl]

I'm not sure either - but what lead me to this question was the news to me that "variable deadrise" is the change in deadrise along the LENGTH of the boat, not from keel to chine like some describe. The keel to chine rise/change in deadrise is more commonly referred to the "concavity". You can measure deadrise at a single point, however the transom measurement only is not considered "variable" but instead concave

[Jim Speros]

Nearly every boat built has a variable deadrise over the length of the boat.

Its nothing new just something to take up space in a brochure.

[TooStroked]

I'm not sure either - but what lead me to this question was the news to me that "variable deadrise" is the change in deadrise along the LENGTH of the boat, not from keel to chine like some describe. The keel to chine rise/change in deadrise is more commonly referred to the "concavity". You can measure deadrise at a single point, however the transom measurement only is not considered "variable" but instead concave

And some manufacturers - Progression for instance - vary the deadrise at the stern as well. The 22 for instance starts at 24 degrees closest to the pad, then drops and you head towards the outside chines.

[FUJIMO]

...the deadrise number noted in a any v-bottom boat brochure, is at the transom, as pretty much, thats the only one that really matters, since its the trailing edge of the boat...

[Lake X Kid]

Most boats have a deadrise at the transom of 22 to 26 degrees. 22 is a popular deadrise. 26 is a deep v.

How much it varies moving forward varies with builders. Your Velocity pictured is a stretched, stand up version of the 22. The 22 has a long flat pad and a 22 degree deadrise that extends pretty far forward. The 30 Velocity progesses to a sharper deadrise moving forward. I enjoyed how both run and are different.

The 22 runs flat and kind of hard but carries weight extremely well is is fast. The 30 can run on its tail in calm water and can be laid over with a lot of cut in the bow to run well in Rough water. .

This seems to describe how I always thought of the benefits of a sharper deadrise angle proceeding towards the bow, and the lower degree angle at & near the stern area.

It comes down to choosing the ride you want, in the water you most frequent to be on.

[Aaronhl]

And some manufacturers - Progression for instance - vary the deadrise at the stern as well. The 22 for instance starts at 24 degrees closest to the pad, then drops and you head towards the outside chines.

Like Jim S said - most Vs are already variable dead rise (along the length) Progression has "concavity" from keel to chines...Thats why I was confused looking at some designs including Progressions that say variable deadrise... thinking that maybe they were the same thing again variabel deadrise is along the length...you rearly see fixed deadrise hulls

[Chaz]

I gotz two nice digital inclinometers that measure down to the tenth of a degree. And a handful of Ace / Lowes / Home Depot .. $10.00 specials.
I'll bet a canoli' that if ya really wanted to know .. you'd get the best meter you could afford .. and measure the hull for yourself. Ya might be suprized to find out that it may vary from side to side ... @ different places along the hull ... cuz they think that no one gotz the gumption to mead-ure fer thrmselfs. I rekkon, for the most part .. they rite

[Forkin' Crazy]

I think my 20' Allisons start at 24 and taper from there. It also has reverse strakes, when going slower speeds or in level flight, the wave or spray will be deflected downward causing lift.

My 23 Howard is the same I believe but has a huge pad. I think it also has reverse angles on the strakes. I think the steepest part is 26. With a 6' beam, it is definitely the smoothest ride of any boat I own.



Hell, the XB 2002 has a slight V in the pad as do other Allisons. SMH .... Every time I edit it does something different!



No V on the Howard pad. FLAT, FLAT, FLAT!



EDIT: For some reason it is difficult to upload pictures. Every time I edit it does something different!

[David]

Powerboat used to list transom deadrise in their boat tests. This got dropped eventually

25 Velocity 25 degrees, 1983
22 Velocity 22 degrees, 1985
Hustler 32 24 degrees, 1983
Fountain 33 23 degrees, 1983
23 Cougar 22 degrees, 1992
24 Schiada 22 degrees, 1990
21 Schiada 15 degrees, 1988
SS2000 specs.pdf

[Jim Speros]

There are so many ways bottoms can be different from each other. Countless boats are splashed from something that works then lengthened or some how modified. It seems a 30 Velocity was a modified 29 Mirage. Steve added a pad and a notch. The 10 meter Fountain was a modification of an Excalibur. It already had a pad not sure but I think a notch transom too. Reggie added the beak and he modified the the deck to enclosed big engines.

About the beak, many people are quick to criticize. I am here to say it is an awesome thing. Only a few boats the 30 Superboat and Fountain boats have a bow that likes to be punched through the top of a sea. When it gets rough you need to push the boat straight ahead. In these boats you can go over 2 and thru one. Its a special feature when racing to punch through the tops of the big seas you encounter. Instead of flying off the top of a monster, you put the bow thru the top of it and take 4, 6 or 12 inches of water up the deck and over the fairing. When properly done you don't even slow down. Nearly every other offshore V bottom wants to stay on top, veers sharply to a side or folds the boat at the numbers and oil can crushes the deck into the cabin.

Every nice boat has a strong point designed into it. Great boats do many things exceptionally well.