Conference unifix::sailing

    I hate to do this in such a well run conference - but couldn't resist:
    
    As you know I'm the token stink potter & know little about sailing:
    BUT,
     	It sounds to me that Carl is really looking for a 
            MOTOR HOME  (aka Land Yacht)
    
                                Good Luck Carl,
                                                Lou

    Hi Carl,
    		I think that you end up buying a boat very much like you a
    buy a car. You get very smart on paper, having read masses of brochures
    & tests. You listen to your friends' idea of what an ideal boat should
    have, & in the end you get your family to add in their 10 cents worth
    when you have narrowed down to two or three. The family brings in
    common sense & are pleased to be involved.
    
    		This has worked for me for two very different boats. My son
    & I would have gone for something lighter & sportier, but the final
    choice is something safe in a good blow, that you can handle by
    yourself, with some creature comforts for the family.
    
    		Let us know how you get on...
    						All the best,
    								Nick
     

    You might want to consider a modern cruising catamaran.  Several
    couples won't sail together because one of them don't like to heel.  A
    modern cruising catamaran will meet you requirements except for class
    racing.
    Once you have made the switch you will never go back.
    A few boats are available for charter and note 1631 list a few brokers.
    Unlike monohulls there is a large variation in production catamaran
    designs therefore you should consult with at least one experienced
    catamaran owner.  Multihull owners will be more biased about designs
    than monhull owners possibly because they want something different and
    have fullfilled their need.
    
    
    
    

Carl,

You are obviously much more thoughtful than most boat buyers. I don't 
think I knew enough to ask such questions before buying my current boat. 
But you did miss at least one important reason for choosing a boat:
beauty. I am totally uninterested in owning a boat I don't think is at
least attractive if not downright beautiful regardless of anything else.
Ah, the lovely sweeping sheer of a Hinckley Bermuda 40 ..... Bill Tripp, 
you done great. 

Male chauvinism aside .....

The question of boat motion and comfort in a seaway is one that seems
almost universally ignored, though it shouldn't be. Marchaj's 
"Seaworthiness, The Forgotton Factor" has an interesting little graph 
showing acceleration vs probability of seasickness. The direction and 
speed of a boat is constantly changing (in pitch, roll, and yaw), and 
direction and speed change very rapidly in a rough sea. These changes 
(acceleration) tend to cause seasickness. The greater the acceleration, 
the more likely you are to be seasick. As one who does get seasick, this 
is a question of more than academic interest to me. 

Now, in very general and non-quantitative terms, it is the impact of 
waves on a boat that causes changes in the boat's speed and direction.
The impact or force applied to the boat is roughly proportional to the
surface area struck by the wave. One of the fundamental laws of physics
is that force equals mass times acceleration. So, a light boat (less
mass) will suffer a higher acceleration for a given applied force (from
the impact of a wave) than will a heavy boat. High acceleration is 
generally perceived as less comfortable than low acceleration (which is 
one reason I am not fond of high speed elevators). 

Ted Brewer has proposed what he calls the motion comfort ratio (see an 
article in Cruising World late last year). This ratio is an attempt to 
quantify comfort from readily available numbers.

   RATIO = DISP/(0.65*(0.7*LWL+0.3*LOA)*B**1.33)

   where DISP is the displacement in pounds
         LWL is the waterline length in feet
         LOA is the overall length in feet
         B is the beam in feet

This ratio agrees that, for a given LWL, LOA, and B, a heavier boat is 
more comfortable than a lighter boat. 

It also says some other interesting things. Wide beam reduces comfort. 
Makes sense. A wide boat pitching or falling onto a wave will stop more 
abruptly than a narrow boat -- higher acceleration. The fact that B is 
raised to the 1.33 power indicates that beam has a very strong effect.

The inclusion of length probably takes into account that longer boats 
have more surface area and hence the total impact from a wave is higher.
Why Brewer chose the constants he did was not explained. 

By itself, this ratio doesn't mean much. But comparing several boats 
becomes quite revealing. In general, by the way, the formula for the 
ratio predicts that large, light boats may well be less comfortable than 
smaller, relatively heavier boats. 

Just a few (approximate) numbers:

  J30c            15.9
  C&C 26          16.9
  Farr 40         20.0
  Valiant 32      29.1
  Cape Dory 30    33.8
  Valiant 40      34.2
  Deerfoot 61     34.3
  Riemers 48      50.6

Now I know from personal experience that my Valiant 32 is vastly more 
comfortable in rough seas than my C&C 26 was. I was often seasick on the 
C&C and am seldom so on the Valiant. (The Riemers 48 is Nathanial 
Bowditch, an older wooden boat that I greatly admire and briefly thought 
about buying. She is a boat I would take almost anywhere.)

Anyway, take this for whatever you think it is worth. It does seem to 
have some validity, and Ted Brewer is certainly an experienced naval 
architect. It might be interesting to calculate the ratio for 
boats you are considering.

Cheers,

Alan

    The Brewer formula has been updated to the following:
    
    disp/((.65*(.7*lwl + .3*loa)*b**1.33) * AF**3)
    
    AF is the average freeboard or the Amy factor after my wife who
    discovered it.
    
    What it means is the higher up you are, the sicker you get.  We have
    considerable empirical evidence to support this.
    
    - gene

re .5:

Gene, is the change from Brewer or you (grin)?  But you are absolutely 
right, the further you are from the roll/pitch/yaw axis, the greater the 
acceleration. For this reason I only go to my masthead in flat calms. It 
is also why I'll never buy a center cockpit boat.

    Gene is right on height off the water.      I have a Person Triton
    (1967)  Loa; 28'6", Lwl; 21'6"(design is 20'6"0, Beam; 8'3", disp;
    8400#, freeboard 25"-30".
    
    On a trip out of Oak Bluffs on Martha's Vineyard a few years back
    we had a stiff Northeaster blowing into the jettys as we left for
    Edgartown.     The boat was making like a submarine as we headed out
    and then settled on a close reach with reef main and storm jib.
    
    Your basic day of "square waves" .  My friend's wife who was used to
    being on her brother-in-laws Columbia 26 remarked on how much better
    she felt on the Triton, a good part of it was the fact the Columbia
    had double the freeboard.
    
    The relatively narrow beam and long overhangs are strong contributors
    to comfort as you can watch the more gradual acceleration/deceleration
    as compared to boats with short overhangs and low deadrise.
    
    Of course on a Triton I find a dodger is needed for you do trade the
    comfort for wet.
    
    All boats are a compromise, you pick based on usage and wallet.
    
    Frank

    If you  want  an  easy  to handle boat avoid IOR style hulls. They
    have  very  pinched  sterns  and  lots of beam fairly far aft. The
    combination  is  a real handful in a quartering sea. It's a lot of
    fun  to  try  to  master  it,  but much too much work for any sane
    person to want to try.

    In addition,  there are boats that are considerably faster for the
    same length, as well as being easier to handle.

--David

    	re. -1
    
>    If you  want  an  easy  to handle boat avoid IOR style hulls. They
>    have  very  pinched  sterns  and  lots of beam fairly far aft. The
>    combination  is  a real handful in a quartering sea. It's a lot of
>    fun  to  try  to  master  it,  but much too much work for any sane
>    person to want to try.
    
    A broker would probably advertise this as "Surfs easily". Many cruisers
    that are build for accomodation rather than sailing ability suffer from
    the same problem, and they don't go up wind either.
    
    Obviously don't buy an old IOR racer if you don't want to race. Most
    cruiser versions of IOR designs are fairly harmless though.
    
    Chris.
    

You have asked a long series of very good questions, which require lengthy 
responses, with many qualifications.  My own recommendation would be to 
absorb all you can from a copy of "Skene's Elements of Yacht Design", 
edited by Francis Kinney.  It's the classic first text of modern yacht 
design, and outlines all the main factors influencing comfort, speed, and 
(if you extrapolate) cost.  It's probably the most readable technical 
introduction out there, and the factors he presents are as valid today as 
they were 35 or more years ago when the first edition came out.  

Marchaj is for a more ambitious and mathematically inclined reader, and 
goes beyond hull design alone to consider interactions with sea 
conditions.  Skene's focuses on prismatic coefficient, surface area, 
deadrise, cutaway, keel configuration, sailplan, etc as interacting 
elements in developing a design compromise.  Scan a copy, and see if it 
strikes you.

J.

    I've been reading this note with interest.  You don't say so, but imply
    that you want to continue to race in Naragansett Bay.  If you want
    sturdy comfort and want to race you may well have to settle for a
    relatively "racer/cruiser" like a larger C&C or Saber or Tartan etc.
    But... you will remain in the middle of the fleet.  If that's okay,
    then no problem.
    
    I could never race a compromise boat like that.  Hence my VERY
    uncomfortable Harrier.  It probably has a comfort ratio somewhere like
    a Laser!  Worst motion in heavy seas I've ever experienced.  But very
    fast!  Once I own a cruising boat it will be strictly cruising. 
    Totally different motives.  I share Alan's lust for Bermuda 40's.  A
    Block Island 40 will do as well.  In short, I would take advantage of
    today's depressed market and get a classic older Pearson Wanderer or
    something like that, cruise it and race with somebody else.  
    
    Dave