The Boating Forum - What is dead rise???

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View Full Version : What is dead rise???

07-19-2002, 06:33 PM
What does it do for a boat?Also why are some boats lenghts listed as LOA others not.

07-19-2002, 07:10 PM
deadrise is the slope and lenght of the bow from the waterline to the stem of the bow. LOA means lenght over all. LOD means lenght on deck. LWL means lenght onwater line /infopop/emoticons/icon_biggrin.gif /infopop/emoticons/icon_wink.gif


07-19-2002, 07:17 PM
I must humbly disagree with sloopy, /infopop/emoticons/icon_wink.gif now hang on a minute sloopy.

Deadrise is the the term given to the degree of angle of the hull at the transom. A greater degree of deadrise at the transom will give a smoother ride through rough seas by cutting through them better, usually 22 degrees or higher, (See Contender-go fast boat) but is a more unstable platform when sitting still, and is subject to violent rocking when hit abeam by the seas. This design also creates more drag and therefore uses more fuel.

No deadrise would be a flat bottom skiff and will beat the living crap out of you in a 2" chop.

Most boats try to find a happy medium that will be useful to more everyday boaters.

07-19-2002, 07:21 PM
every hates me, join the club! /infopop/emoticons/icon_frown.gif


Jack Hexter
07-19-2002, 07:24 PM
Dead rise is applicable to planing power vessels only. It is the angle of the bottom of the boat from horizontal at the transom measured from the center of the hull to the chine. In other words, If you take a horizontal plane and place it on teh botton of the hull at the transom, the angle between this plane and the hull is "dead rise." Thus, if you are looking at a boat with a 24* dead rise, the Vee at the transom would be 48*.

The amount of Dead rise affects how a boat will run or cut thru a chop. Generally, a higher degree of deadrise will cut thru a chop easier and produce a softer ride. Conversly, a flat bottomed boat will pound. The trade off comes when you stop. A Deep Vee hull (24* dead rise) will rock and roll more than a flat bottom boat or modified vee hull while drifting

07-19-2002, 07:24 PM
so dead rise is measured from the center of hull up towards starboard and port like the v in the hull the more of a v the more it cuts the water better but rocks more i see now thanks.

07-19-2002, 07:32 PM
Deadrise from the MariSafe website is: the angle of a boat's bottom relative to the horizontal.

This can apply to a planing or a displacement hull.It extends the length of the hull, not just at the transom.

Sloopy nobody hates you. /infopop/emoticons/icon_smile.gif

07-19-2002, 07:49 PM
quote: Sloopy nobody hates you.

Your like the friends I never had /infopop/emoticons/icon_smile.gif I'm sorry I was very wrong, y talking about the bow, its the sides!!! /infopop/emoticons/icon_frown.gif


Ed P
07-19-2002, 08:06 PM
Jack was SO close...

A boat's "V", with a 24-degree deadrise, would be 132-degrees (180-24-24=132)...

A flat-bottom boat has 0 deadrise, and a 180-degree "V" (horizontal, i.e. no "V").

Picture a boat out of the water, as if on a trailer or davits. Hold a board, yardstick, (whatever) exactly level under the hull, at the transom. Measure the angle from the board to the hull bottom (on one side only)--that's the deadrise. Of course, the other side should be the same size angle /infopop/emoticons/icon_wink.gif We know that the board is 180 degrees, so 180, minus the two angles from the board to the hull, leaves you the angle of the hull itself.

Deadrise is the angle from the board to the hull bottom on one side.

Ed P., St. Pete., FL

07-19-2002, 08:07 PM
I'm surprised nobody here yet told you it is a horror movie! /infopop/emoticons/icon_biggrin.gif /infopop/emoticons/icon_wink.gif

There real experts on hull design here, but here are my 2 cents.

1. Deadrise is ONLY ONE factor for hull design criteria. It perhaps the most important for a soft ride. The steepness of the hull at the bow is usually greater compared to at the transom though that angle is not usually quoted.

2. A steep deadrise is usually preferred for offshore boats to handle the waves, but at the expense of both roll stability at rest(as others have mentioned) as well as horsepower requirements. You need more powerful engines compared to a shallower deadrise hull and this can be significant both in initial capital cost and fuel expense.

3. The beam of the boat also contibutes to the overall ride softness as it affects the hull shape. Multihull boats exploit very steep narrow beam hull shapes producing a very soft ride.


07-19-2002, 08:58 PM
well that ruins my future of a yacht desighner! /infopop/emoticons/icon_mad.gif /infopop/emoticons/icon_mad.gif /infopop/emoticons/icon_mad.gif


07-19-2002, 09:17 PM
slackerbeme, I forgot one important bit of advice.

After all that has been written and talked about hulls, "The Proof Is In The Pudding" as the Brits would put it.

A sea trail is the only way you will really know how a hull performs. /infopop/emoticons/icon_biggrin.gif /infopop/emoticons/icon_biggrin.gif


Snapper Head
07-20-2002, 02:08 AM
I thought deadrise referred to the folks leaving Tabman's house the day after the big blowout /infopop/emoticons/icon_biggrin.gif

Sloopy, no one hates ya. The annoying signature, maybe, but not you /infopop/emoticons/icon_cool.gif /infopop/emoticons/icon_biggrin.gif /infopop/emoticons/icon_razz.gif

Big Al

07-20-2002, 07:08 AM
Try this:

for a good article on deadrise.

07-20-2002, 09:00 AM
Well, OK - I guess /infopop/emoticons/icon_confused.gif BUT....

If deadrise isn't what JC said to Lazarus - then we've all been misled! /infopop/emoticons/icon_wink.gif /infopop/emoticons/icon_biggrin.gif

Now 0 if Deadrise is this V at the transom....what prey tell is "variable deadrise"? /infopop/emoticons/icon_razz.gif

Lemme guess theat bottom V "varies up n down" flappin like a seagulls wing? /infopop/emoticons/icon_wink.gif /infopop/emoticons/icon_biggrin.gif /infopop/emoticons/icon_cool.gif

Methinks it refers all along the bottom of the hull in fact from bow to stern but is as most have said usually referred to as the angle of the dangle divided by the heat of the meat, times the lust of the thrust, factored by the throb of the knob...aaahhhh at the Stern ..I think! /infopop/emoticons/icon_smile.gif

Then again - I mightta skipped that bit of nautical knowledge 101 class..(what was her name again?) /infopop/emoticons/icon_confused.gif..tis all a blurrrr!


07-20-2002, 12:45 PM
Trouty you are correct. The deadrise changes in the length of the boat. The posted deadrise of a manufactor's boat is always measured right at the transom. /infopop/emoticons/icon_smile.gif

08-02-2002, 08:41 PM
And remember all, this is for planing boats. In a round-bilge no chine displacement boat, the number would be meaningless. In those boats they care more about a/b ratios, metacentric height, prismatic coefficient, etc.

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