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What is deadrise?

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  • What is deadrise?

    I am guessing the degrees of deadrise have to do with the angle of the transom, but I have no clue what it really is or whether more or less of it is desirable. Is there anything I can read to smarten up on the subject?


    Win Davis
    It\'s a Mako.[br]\'82 20B,\'90 E-150[br]Woodbridge, CT

  • #2
    Davis.. I'll give you the super scientific definition...More deadrise= more "vee" in the hull. more V cuts thru the water better than a flat bottom. Trade off is when you drift.. more V = more rocking back and forth. Less V is able to drift with less side to side motion. Below is the easy definition

    For those interested in calculating the deadrise of a hull, the easiest location to do so is at the transom. Measure the bottom width of your hull at the transom and divide this number by 2. The value of a 64-inch bottom would be 32. Then measure the drop at the center of the transom. With a scientific calculator, figuring the deadrise is easy. Divide the drop (A) by half the bottom width (B), and then toggle the key labeled TAN-1. The answer is your deadrise. Perhaps this is taking things a bit too far, all most of us really need to know is that a 3-inch drop in a bottom range of 68 to 58 inches equals a deadrise of 5 to 6 degrees (See Figure 1).
    22 Tiara pursuit[br]Greenwich,Ct


    • #3
      just an FYI, the new 65 Hatteras only has something like 7 degrees deadrise at the transom.
      1978 Mako 25 - Blind Hog
      1985 Mako 20c - sold
      Fort Walton Beach, FL


      • #4
        Thanks, Byram & Sailor. I think I am getting the idea. Now, as I look through the hull specs - like those on the Mako web site - I see some models have degrees of deadrise listed and some models simply have an "X" in the chart. Does this indicate zero dead-rise, which I guess would indicate a dead flat bottom at the stern?

        Thanks for your patience with me.

        It\'s a Mako.[br]\'82 20B,\'90 E-150[br]Woodbridge, CT


        • #5
          No, it just means they don't have it listed.
          [br]***[br]\'82 Ski Nautique - Lake Martin, AL[br]\'80 236IB - Lake Martin, AL[br]\'03 Pursuit 2670 - Destin, FL


          • #6
            I would say from what I see on the spec page at Mako that on the 1991 page I looked at the deadrise for the 28 footer was not listed. Once you get to a certain length the dead rise at the transom dosen't really matter, unless it's a Bertram The orginal deep vee hull. At the longer hull length the hull angle forward of amidships is what counts the most because the hull weighs so much you have to have a flatter aft section or you will need to much horse power to get the boat on a palin. Further explanations will require a course in Naval design
            Alabat - Cajun for \"Hey over there\"[br]1973 - 17 Mako Angler 115HP Suzuki[br]Houma, Louisiana[br]Home of the best Red fishing in the world


            • #7
              It's really quite simple. As you are looking at the transom of your boat, while out of the water, the dead-rise(at the transom, that all literature refers to)refers to the angle of each side of a vee, on a vee-bottomed boat. That's it. If your boat is level on a trailer or boat lift, etc..., simply use a common protractor to determine your deadrise. You know, that little clear plastic, half-round scale that an architect or draftsman uses to draw with. Don't add the two sides angles together or anything like that. Your deadrise is just the angle of one side of the vee. High tech, huh? There are two conventional deep vee types. A variable dead-rise vee & a constant dead-rise vee. The variable vee changes as it goes forward from the transom(into a sharper vee with more & more dead-rise). The constant vee stays the same as it goes forward from the transom, and then sharpens more suddenly. Constant dead-rise vee designs are generally used on calmer to medium rough water boats & variable vee's on rougher water hulls, large or small. Hope this helps clarify your question. Ed[]


              • #8
                Thanks for the explanation, Ed. Now I really understand what it IS. Thanks to you and the others who replied, I not only know what it is, I know what it does, what the deadrise specs mean, what missing specs mean and don't mean and how to calculate it two different ways. Another benefit is that, thanks to Alabat's suggestion, I've decided to cancel my registration for the Naval Design course. I may not yet be qualified to write a book called The Joys and Heartbreaks of Deadrise - Coping With the Hull Truth, but I may change my forum name to include the term just to remind myself just how clueless I am on so many subjects. [?]::laughing::

                I really do appreciate the time you and the others took trying to smarten me up. Thanks again!

                It\'s a Mako.[br]\'82 20B,\'90 E-150[br]Woodbridge, CT


                • #9
                  Now I'll give you my quick and easy way to know exactually what the deadrise is on any boat out of the warter. You already know where to check it at.

                  With this little tool, at a cost of $5.99


                  It doesn't matter if the boat is sitting crooked on the trailer or not level. Check the angle on the port side and write that number down. Now check the angle on the stb side and write that number down.

                  Now add them together and devide by 2. That's the deadrise angle.