Chris Armstrong Posted June 8, 2012 Share Posted June 8, 2012 Hello, As I fancy getting back into slope soaring, especially as it's always windy down here on the South coast, I got some Impala plans off ebay. I have read that the aerofoil used on these was a bit limited in the speed range over which it worked. As I'm building it up from scratch I thought I'd have a fiddle with the aerofoil, however having googled the subject I am somewhat spoiled for choice. The good old Clark Y aerofoil looks like a good starting point as an upgrade. Any comments/recommendations on the aerofoil choice ? It needs to be a bit docile as I haven't flown a sloper since 1991. Quote Link to comment Share on other sites More sharing options...
Andy Blackburn Posted June 8, 2012 Share Posted June 8, 2012 I wouldn't have thought it'd be that quick even with a fast airfoil as the fuselage is quite bulky, so on that basis I'd suggest eppler E374; it's used in a fair few traditional sport models, has good manners at low speed/in light lift, good acceleration/speed if pushed and is reasonably thick so you should be able to keep all the wood sizes and construction the same without building a bendy wing. Quote Link to comment Share on other sites More sharing options...
PatMc Posted June 9, 2012 Share Posted June 9, 2012 Chris, I don't think changing the wing aerofoil would be that much of an advantage but changing the tail from a lifting section to a flat plate - say 1/4" thick - would be a good idea. I never had an Impala of my own but have flown other's peoples a number of times in the distant past. The thing I always noticed about the Impala was a pronounce dutch roll which I put down to too much dihedral. I think reducing the dihedral to about 75% with rudder/elevator only or to 25% & converting to ailerons would make it a better model. If you do change the wing section to something like the E374 then I think ailerons would be an obvious consideration. Edited By PatMc on 09/06/2012 10:22:16 Quote Link to comment Share on other sites More sharing options...
Barrie Dav 2 Posted June 9, 2012 Share Posted June 9, 2012 Yes E374. OK for the slope. Quote Link to comment Share on other sites More sharing options...
Chris Armstrong Posted June 9, 2012 Author Share Posted June 9, 2012 Cheers guys. I'll give the E374 a go. PatMC, I agree with you about changing the tail as I was always taught that the tailplane generally acted downwards which is a bit at odds with it having a lifting section ! I'll let you know how it goes. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted June 9, 2012 Share Posted June 9, 2012 A lifting tail does just that but lifts less than the wing. Good for overall efficiency but not so good for longitudinal stability outside a rather narrow speed range which was ok as it was designed for a single channel. Edited By Simon Chaddock on 09/06/2012 22:20:32 Quote Link to comment Share on other sites More sharing options...
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