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Nov 19, 2008, 05:28 AM
Slip the surly bonds...
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Scale Neuroses


Well, not neuroses in the strict sense of the word, but you will see what I mean, I hope.

My new model is the Canadair CL-415 (now made by Bombardier). It has a number of interesting features: being built along the lines of a Norman castle being the main attraction, as it makes construction so much easier!

I have a few photos and "done so far" notes on my website.

But how far do you go in pursuit of even the most basic scale details? One unmissable feature is that the subfins are built at a 5 degree angle and will induce a turn to port. I've actually made the tailplane so that it accommodates this feature, but having done so, it looks ridiculous, not aesthetically but aerodynamically! I've checked on the main website, and the engines turn the same way as ours do, so to my bewildered mind, on a model, the subfins would just encourage the beast to spin in from 100ft, as the torque reaction would be adding to the turning effect. Or is my man-flu brain just too tired?

A feature relevant to Ivan's plan builders is that it has a real, full-span NACA cuff! Now this would be quite easy to build into the model (if I had not already made the wing, that is) by using a flat-bottomed section and extending the LE down a mm or two, then fairing in the resulting step with some soft balsa or even Depron.

Now, there is an interesting paradox in building a scale model (no, not whether ALL the rivets are necessary) but how you alter the basic structure to retain the features of the original, but use a non-scale modeller's airfoil and angle of attack. This is particularly relevant to flying boats, because to get a smooth take-off the wing chord should be at about 4 degrees to datum. Add to this the use of the thinner airfoil, and how do you build the nacelles and fuselage attachments so that they correspond closely to the original, which has perhaps one degree of incidence and a big fat airfoil? Answers on a postcard.....
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