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Old 01-28-2009, 10:32 PM
  #41  
Yak 52
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Join Date: Jan 2009
Location: UK
Posts: 64
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Some very good advice chaps...

So... If you want to fly 'scale':
Add lightness!
(and fly on calm days!)

The only problem with building too light will be if you end up with a structure that is not strong enough for loads required to fly, land etc.... but with good design that can still be VERY light!

I think an awful lot can be learned from free flight scale models (especially for RC models as small as your 36" span)

Check out www.ffscale.co.uk - Mike Stuart's page. These guys are building peanut scale (13" span) models with near scale rib spacing and construction, to under 12g (half an ounce) and they are far more likely to crash or land heavily.

Although they aren't carrying the weight of radio gear, you can learn a lot about making light and strong structures from the free plan downloads. You might want to use similar ideas for your design but beef them up a little in the wing spars, undercarriage, and areas of the fuselage where Rx/servos/batt/motor are located.

As regards your areas:

There are 144 sq inches in 1 sq foot - not 12...

1ft x 1ft (1sq ft) is the same as 12" x 12" (144 sq in)

so
Area in ft sq x 144 divided by your scale = Area in sq in

I would just work in ft2 though as wing loadings are usually expressed in oz/ft2.


You definitely have to make compromises with 'scale' when it comes to flying - true scale weight, aerofoils and
even construction will give you a model that is hideous to fly! So it's up to you to judge what looks best and weigh it against what fly's best.

You have to treat your model as a whole new aircraft - flying in the same environment as the original. Although it looks the same you are actually giving it a very diferent job to do - aerodynamically speaking...

Interestingly, in free flight scale competitions, marks are given for static appearance and also flying appearance as well as total time so you can see a balance has to be struck somewhere.

If you try to keep to under 10oz/ft2 I think you will probably still have a decent model but obviously the lighter the better...

Yak 52

PS attached is a pic of a Yak 52 - classic russian warbird trainer. Not a Yak 54 crazy composite aero beast!
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