Help with understanding deadrise....

[RobDar]

In looking about at boats...I came across dead rise. I had not heard the term before so I started looking into it. I have yet to find any information that REALLY explains deadrise and how it effects the boats handling.<br />I read less than 14% deadrise is unstable at high speeds...but what is considered high speeds??? Is 45 a high speed? or do they mean 60 is a high speed?<br />14-17% is considered a Mod-V and is more stable.<br />17% and up is V hull and is best for rough open waters...<br />I emailed Tracker, Lowe, and PolarKraft about their Mod-V boats and none of them are in the 14-17% deadrise range...so I am getting goofy info here...<br />Can some one explain this to me???

 

[markvan]

Re: Help with understanding deadrise....

Deadrise is the angle from level that a boats hull is at and is measured as individual sides. So if we take a boat and set it on the floor so that it is level at the top of the transom then measure the angle created by each side of the boat/floor intersection at the transom we have the deadrise. If the transom is totally flat at the bottom the boat is said to have 0 degrees deadrise, and the greater the angle from flat at the transom the greater the deadrise.

 

[shmalik]

Re: Help with understanding deadrise....

This should answer your questions:<br /><br /> http://forums.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=015169

 

[RobDar]

Re: Help with understanding deadrise....

yeah...I got that...understand how it is calculated...what I do not get is how it effects the boat, classifies the boat, yadda yadda yadda...

 

[stevens]

Re: Help with understanding deadrise....

A steep deadrise will allow the boat to slice through the water instead of bouncing on top of it.<br /><br />The classification of various hull designs; flat, modified V, deep V, etc. - I don't really know, except convention has it that the optimal ocean-going deep-V is about 21+ degrees.<br /><br />So many factors will affect handling (deadrise at entry, length, width, weight, load, strakes, chines, balance, etc). that transom deadrise angle means less in itself.<br /><br />Edit: Here's a picture of one of my favourite boat brands , made right here in my hometown. They're extremely seaworthy fast boats and all their hulls have a deadrise of 24 degrees:<br />

 

[KCook]

Re: Help with understanding deadrise....

I read less than 14% deadrise is unstable at high speeds

That is simply untrue. "unstable" would mean that the boat is at risk for rolling over. Which it is not. There are race boats with under 14deg deadrise that run near 100mph.<br /><br />Instead of "unstable" what should have been said is "pounds in rough water". Which IS true. But you have to assume rough water first (low deadrise works fine in quiet water). And getting bounced around is not as serious a situation as being "unstable".<br /><br />Kelly

 

[RobDar]

Re: Help with understanding deadrise....

to Kcook...I did not say unstable...that is what I read,...which I questioned...which is why I posted these questions...because what I was finding on a quick net search left me scratching my head.

 

[RobDar]

Re: Help with understanding deadrise....

the thread posted by shmalik was very heplful...thanx...<br />some good info in there...the info I was looking for...like how dead rise effects acceleration...how it related to draft, the chines etc etc etc....