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Conference vicki::boats

Title:Powerboats
Notice:Introductions 2 /Classifieds 3 / '97 Ski Season 1267
Moderator:KWLITY::SUTER
Created:Thu May 12 1988
Last Modified:Wed Jun 04 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:1275
Total number of notes:18109

496.0. "Transom deadrise angle" by CDR::SPENCER (John Spencer) Mon Aug 28 1989 13:43

Unable to find a relevant existing note, let me ask this question in a new 
one:

Why is 24 degrees deadrise apparently such a magic number?  I've seen 22, 
22.5 in some cases, but a majority of performance offshore boats, 
including many outboards (even down to 14' in the Musling line) are 24
degrees.  Never 25 or greater, it seems. 

I understand that of course there's a practical limit to the amount of 
deadrise, but does anyone know why it seems to be 24 degrees?

Thanks for your thoughts,  

John.
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496.124=good compromiseNUTMEG::KLEINTue Aug 29 1989 13:2714
    
    24 degrees was the original number from Aronow back the early days
    of offshore racing. the number seemed to offer the best compromise
    between ride comfort, final freeboard to be offered, horespower
    needed to achieve desired top speed, etc.
    
    there are actually quite a few boats coming with 20 - 22 degree
    deadrise hulls which seem well suited to lakes/inland waterways
    ...also there are 26 degree hulls which ride like
    plush autos in very sloppy seas buy which take enormous amounts
    of horsepower to 'break free'.
                             
                
    
496.2DEAD RISE? SOMETHING ABOUT HALLOWEEN?OTOOA::LEBENFri Jul 28 1995 13:4810
    I have seen the term 'dead rise' used in the brochures I've been
    reading lately and the amount of degrees associated with each boat, but
    I have no idea what they are talking about.  Could someone please
    enlighten me so my wife and I don't look like complete bumpkins when
    shopping.
    
    Thanks in advance,
    
    Rick
    
496.3LEEL::LINDQUISTLies, damn lies and managementFri Jul 28 1995 14:4242
��                       <<< Note 496.2 by OTOOA::LEBEN >>>
��                   -< DEAD RISE? SOMETHING ABOUT HALLOWEEN? >-

��    I have seen the term 'dead rise' used in the brochures I've been
��    reading lately and the amount of degrees associated with each boat, but
    This is what you say about someone of your sexual-target
    persuasion.   e.g. {s}he could make the dead rise.


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        -------------------------------------------------------------------

    Deadrise is the measure of the angle show in the rather crude
    picture above.  It is customarily measured at the transom. 
    0� would be a flat bottomed boat.

    In general, the less the angle, the faster the boat will go
    (with comparable power), and the less suited the boat will
    be for rough water.

    Conversly, the larger the angle, the better the boat will
    handle rough water, while needing more power to achieve the
    same speed.

    Flat bottomed boats also generally produce smaller wakes,
    so you often see very small dead-rise angles in boats used
    for water skiing.

    So, you might expect a boat which will be used on a small
    lake to be nearly flat bottomed, while a boat intended for
    ocean use will have a fairly large deadrise.  A large
    deadrise is often called 'deep vee'.   But, 'deep vee' is
    a pretty much meaningless term -- like sports car.  If the
    manufacturer wants to portray an image, they call whatever
    it is 'deep vee' (sports car).
496.4THE DEAD RISE ONLY FROM THE STERN...OTOOA::LEBENMon Jul 31 1995 09:117
    Thanks very much for your answer on the term 'deadrise'.  (Got it right
    now...)  You explained it well enough so that even we understand it.
    
    Thanks again,
    
    Rick