Deadrise???

[jbezanson]

I have heard the term deadrise referred to in degrees on this site many times. I understand it is relevent to how a boat does in waves.<br /><br />My question: What is deadrise, and how do you determine how much your boat has?

 

[calwldlif]

Re: Deadrise???

Angle formed from the keel (lowest point)<br />to the edge of the beam (highest point)<br />at the transom. The greater the distance<br />from low to high the greater the deadrise<br />giving better wave "cutting" ability,<br />at the sacrafice of stability from rocking.

 

[KCook]

Re: Deadrise???

Another thread on this topic - Difference in Deadrise <br /><br />Kelly Cook

 

[Boatist]

Re: Deadrise???

I agree with Wildlife. However if the boat has reverse chimes it can still be just as stable. More dead rise means a little smoother ride in the chop but it also means need more power to plane and lower top speed with the same power.<br /><br />If a boat has a nice sharp entry and flatens out toward stearn can ride very nice but still plane easy and have good speed. Reverse chimes also helps to plane quicker.

 

[QC]

Re: Deadrise???

I agree with most said here and on the other thread, but the speed of the boat makes a huge difference in this discussion. If the boat runs 40+, transom deadrise becomes more important. Yes, bow entry matters too, but once the bow is trimmed up, skipping from top to top is done further aft. Higher transom deadrise makes a huge difference in comfort in those situations. That other thread mentions 17 vs 21 degrees. In my experience that 4 degrees means the difference between slogging along at 18 MPH and being able to run 40+ in pretty rough water. Just depends on what you want to do and who is in the boat with you . . .

 

[Stratocaster]

Re: Deadrise???

 

[KCook]

Re: Deadrise???

Nicely done Mike

 

[Stratocaster]

Re: Deadrise???

Thanks Kelly...a picture's worth at least 458 words.

 

[KCook]

Re: Deadrise???

Vee need a ThumbsUp smilie here

 

[jbezanson]

Re: Deadrise???

Thanks for the explanations guys...Mike P the drawing was just the ticket!!! I now know more than I did before!

 

[mattttt25]

Re: Deadrise???

and just to add... usually, the more transom deadrise, the more power needed to produce the same speed. so a big center console or performance boat with lots of deadrise needs a ton of power to get the speed up. but when you have the deadrise and power... what a ride!!!

 

[Texasmark]

Re: Deadrise???

But don't forget about lifting strakes....those "notches" in the hull that run from fore to aft. The faster you go, the more lift you get from them and they help get that "deeeeeeep V" up and on the water and reduce required hp for a given setup/speed... Also help cusion you when you crash through the larger waves at your higher speed.<br /><br />Mark

 

[KCook]

Re: Deadrise???

Sorry, but strakes are no "cushion" under any circumstances. In many boat designs the strakes are overdone, the builders know they make the hull bottom look racier, and sell a few more boats.<br /><br />Kelly

 

[Texasmark]

Re: Deadrise???

Well, they make sense to me and the deep V boats that I have owned/ridden in, all have them and as oncoming waves crash against each one you can see puffs of spray going out.....which translates to me as cushioning. Now how much?<br /><br />Mark

 

[stevens]

Re: Deadrise???

There's this Swedish boat designer, Mr. Ocke Mannerfelt, who has designed a great number of very fast boats, including many produced by the Swedish standard bearer Nimbus, Sealine, plus others (more info on link ).<br /><br />From Ocke's drawing board has also come the so-called Roca Speed Rail, which is an aluminum profile to be glued on to existing strakes to make these point drastically downwards.<br /><br />The have been in use for 10+ years over here and many people swear by them, saying the downward spray from the rail produces additional lift and thus higher speeds.<br /><br />More information on: link <br /><br />

 

[KCook]

Re: Deadrise???

Nice illustration Stevens. That particular style of strake should result in a cushioning effect. As the downward hanging fence helps confine (entrap) the air flow. On this side of The Pond it's very rare to see this style strake, though we do have a few designs with a similar chine. Our brand that has used an entrapment chine on a lot of its production is Scout. ActionCraft, Glastron, and Wellcraft also have some history with this.<br /><br />Kelly

 

[studlymandingo]

Re: Deadrise???

That is an interesting design, I wonder if there is anything here in the states that works similarly.