50%scale (how do you scale down a design?)

If I reduce a part to half the original size ,do I want to reduce the thickness of the part also,If I go 50% scale does that mean everything else would be scaled to half also ,like the effective payload or gross weight?I at first thought you just divide every number on the plans in halve but I suspect that it my not be that simple.Please help I can build it ,if I know what it has to be.http://www.mhm-scale-aircraft.com/ if you like the beaver you should check this out.


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  • With the obvious stress points, wing roots and spars, engine mounts, landing gear mounts, think about how much abuse it will have to cope with.
    The other thing you have to take into account is tailplane area, I have found this out the hard way.
    Usually when I build a new design, I make it less than 50cm long.
    My prototypes tend to be VERY cheap! Unguided, simple "chuck" gliders, I find this is the best way to get a ball park idea of how it will perform.
    This is how I found out that a TIE fighter is easier to get stable than an X wing, and gave up on Fireflash from Thunderbirds, although I may revisit that one!
    I start with a single sheet of 3mm (1/8") balsa and/or a family sized pizza box.
    When I scale it up, usually the tailplane size changes. Sometimes larger, sometimes smaller, it depends on how "used" the air flowing over it is.
    Remember the basic rule of thumb,
    If it looks good, it will fly good,
    If it looks like a pig, it will fly like a pig!
    The guy that designed the SR71 said something like that!

    An excellent book on aerodynamics is
    Model Aircraft Aerodynamics by Martin Simons
    ISBN 1-85486-190-5
    published by Special Interest Model Books
    PO Box 327
    BH15 2RG
    It is THE best reference you can have, anyone who builds things that fly should have a copy
  • do what the mythbusters do just make a really big remote control airplane why would you want to scale it down and with an airplane that big just think of all of the equipment you could fit into it!
  • James Hall
    Thanks for your reply James.If controls are reduced,would payload be different than 1/2 the full scale's payload.
  • WOW! Nice picture and plane too!
  • To keep weight down, I would scale the thickness except in areas that are structural such as wing spars, wing ribs. You will also have to take into consideration the pressure on control surfaces as this will be reduced but will also reduce control and require more servo throw. There are some design consideratiosn I have used such as increasing the rudder surface area to allow snappier turns, but thats mostly flying acrobatics, not typical UAV applications.
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