Conference vmszoo::rc

    I just received a catalog from Zenith Aviation Books, they have
    one of the best R/C book assortments I've seen, including some on
    sailplane design.  Call them for a catalog.
    
    		Zenith Aviation Books
    		P.O. Box 1
    		Osceola, WI 54020
    		1-800-826-6600
    
    Scott Cox
    

    There is a book written by the venerable Frank Zaic which is excellent.
    Although this book was written in the 1940's it is still one of
    the best books available.  I will send you the information on where
    to order this book.  It is a paperback and very inexpensive.
    
    Regards,
    
    Jim Blum

            There is a paperback I think is called Model Aircraft
    Aerodynamics. It is sold mail order through most model magazines.
    It is so complete that I have heard it is sometimes used as a
    college text.It has airfoil coordinates and polars and also has
    a lot of material on balance and dynamics with an emphasis on
    gliders.
    
    
    
    
    
    

    This is the book that I have, somewhere (sigh).  It is an
    excellent theoretical text on the design of, principally, model
    gliders.  It thoroughly discusses just about everything you'de
    ever want to know about aerodynamics, like Lift to Drag ratios,
    Renolds numbers, laminar flow, turbulent flow, center of lift vs.
    aerodynamic center, the effects of CG postion, and tons of other
    stuff I don't remember anything about.  The worst part about it is
    that it's not really a "cookbook" type of manual that will tell
    you how to design a plane.  It teaches you what you need to know
    about plane design in terms of mathematical formulas, and you have
    to put the "pieces" together.  In order to really use what the
    book has, you have to work through it like you're taking a course
    in aircraft design, so that you understand all the areas covered
    in the book.  I'de recommend it, though, since even a quick
    reading will teach you things you probably didn't know.

    Randy (8^|) 

Chuck Cunningham, in RCM, has over the years republished a
series on plane design, including a segment on glider design.
The last time this was done, to my knowledge, was in '86 -- give
or take a year.  I have his articles as published in the late
'70s, but I'm sure what I have is not substantially different
from the latest version.

Chuck adheres to rules of thumb, what I call the Good Ol' Boy
Method, in which he specifies the surfaces in terms of percentage
of the wing area, and the moments in terms of chord lengths.  His
proportions are classic in that you will find them similarly
stated in free flight design texts also. 

Personally, I've used Chuck's recepie in conjunction with other
sources to design several variations on an original glider (Yes,
despite my misadventures in learning to fly, I've attempted to
fly my own design too!  It takes more money than brains...).

Anyway, I'll send you copies of the articles if you send my your
mailstop offline.  That goes for nearly everyone else too.

    Hi,
    
    Thank you very much for your information.
    
    I'am living in Barcelona (Spain) and ussually is dificult to obtain
    information about foreing books and magazines about aeromodelling.
    
    Regards.
    
    Jordi

    I used to fly gliders at one time. Back in 85 when I was in CXO
    working on a project. Since then I've wondere why most gliders
    that run ailerons and rudder still utilize such large amounts of
    dihedral? In my eyes extra dihedral than what is minimuly necessary
    causes the wing to yaw to much which should slow down the ship.
    Insufficient dihedral would cause adverse roll. I was wondering
    why a design isn't developed that minimized that amount of dihedral
    so that rudder only produced a yaw rather than a roll in the direction
    of the rudder deflection. Anyone have any ideas??
    
    
    						Tom

    The more dihedral a glider has, the more inherently stable it is(ie
    the greater its ability to resume straight level flight after a
    maneuver).  A straight wing glider with little or no dihedral that
    does not have ailerons is incapable of roll when rudder is deployed.
    Hence the glider just slips along akin to a sailboat trying to come
    about with its centerboard up.  Dihedral allows one wing to be
    partially stalled which is why the glider rolls when rudder is
    deployed. Gliders with generous dihedral are usually very stable
    and easy to fly.  There is currently a 6 part series in Model Aviation
    discussing all the aspects of dihedral.
    
    Regards,
    
    Jim
    

    Jim here is where I'm coming from;
    
    I one wants a glider that turns quickly but with miminal drag I
    would think that the best way to do this would be a slight deflection
    of the ailerons and the deflectionof the elevator and rudder. this
    would tend to make the turn tight and flat which I would think would
    result in minimum drag in the turn. If I correct then I wonder why
    anyone hasn't designed such a ship?
    
    
    						Tom

    You are exactly right, however the low dihedral aileron ships will
    tip stall much more easily than their polyhedral complements and
    usually fly much faster due to higher wing loading and lower drag.
    These flying characteristics make a low dihedral, aileron ship hard
    to handle for inexperienced or slow reflexed flyers.  If you are
    a skilled flyer the quicker response of an aileron ship might be
    desireable.  For slope soaring straight wing aileron ships are the
    norm, but it appears polyhedral ships still hold the edge for thermal
    duaration contests.  At this years NATS 2/3rds of the gliders were
    polyhedral and I believe all the top placing ships were polyhedral.
    The debate among people much more knowledgeable than I goes on over
    which design flys better.  However all agree that a polyhedral ship
    is easier to fly!
    
    Regards,
    
    Jim

    The four part dihedral series by Blaine Beron-Rawdon appeared in Model
    Aviation in August through November of 1988.  The current issue,
    September 1990, has the first of a two part expansion into Spiral
    Stability by the same author.