A Collins Posted June 16, 2011 Share Posted June 16, 2011 Hi, I'm just starting to build a Ben Buckle Galahad and the plans indicate 5" dihedral at the wing tips. For those not familiar with the plane it has no ailerons. I know what dihedral is but what does it do? Has anyone a simple explanation please? Also, what would be the effect if I were to reduce the amount of dihedral? Just curious as I intend to build to plan. Quote Link to comment Share on other sites More sharing options...
Ben B Posted June 16, 2011 Share Posted June 16, 2011 It gives the plane some automatic stability and is needed to convert the yaw induced by the rudder into a banking manoever rather than just a yawing / skidding move. Reducing the dihedral would therefore make the plane less stable and make it yaw in turns rather than bank.Edited By Ben B on 16/06/2011 16:23:51 Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted June 16, 2011 Share Posted June 16, 2011 wot he said, watch a pidgeon, see how it steers, it has LOTS of dihedral, when it lowers one wing, the stability on one side goes, clever bird, and OH so tasty, 2 Alan Cs eh? that could be confusing Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted June 16, 2011 Share Posted June 16, 2011 Dihedral is a way of overcoming a too high centre of gravity above the centre of lift .The lower the wing (for stability -hands off your Tx) the more dihedral you need . ie Cherokee etc . That is to say that the lift due to the A/c design must always be above the vertical component of the C of G to be able to fly hands off (free flight).Edited By Myron Beaumont on 16/06/2011 17:39:08 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted June 16, 2011 Share Posted June 16, 2011 Oh dear - I'm going to have to remember "AlanC" and "Alan C" - this could stretch my mental capacities BEB Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted June 16, 2011 Share Posted June 16, 2011 Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 16, 2011 Share Posted June 16, 2011 had me confused for a minute - Alan C asking about dihedral?Years ago a club member had a Galahad was built from the original Mercury kit with bucketloads of dihedral. He flew it on rudder/elevator/motor and it was amazingly nimble. Quote Link to comment Share on other sites More sharing options...
John Privett Posted June 16, 2011 Share Posted June 16, 2011 My first low-wing R/C model was a Galahad back in the mid-70s. I reduced the dihedral to about half or less the stated amount and fitted strip-ailerons. Quote Link to comment Share on other sites More sharing options...
Richard Harris Posted June 16, 2011 Share Posted June 16, 2011 Alan, The Galahad is a great model to fly as long as you stick to the dihedral stated on the plan. As Myron stated the CG should be below the centre of lift for the rudder to be effective as a roll component. If the dihedral were to be reduced below then ailerons would be needed as the rudder would just yaw the model round. Rich Quote Link to comment Share on other sites More sharing options...
A Collins Posted June 17, 2011 Author Share Posted June 17, 2011 Many thanks for all the replies and the explanations of dihedral. As usual the forum comes up trumps again! Now am I AlanC or Alan C? I've heard of split personality disorders, I think I'm suffering one now. Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted June 17, 2011 Share Posted June 17, 2011 NIce one TFFKAAC If it was good enough for Prince it'll work on here! BEB Quote Link to comment Share on other sites More sharing options...
MarkyMarc Posted June 17, 2011 Share Posted June 17, 2011 Basically, dihedral gives you "wing levelling" stability. If a disturbance causes a roll - one wing low - dihedral effect will cause the plane to regain roll stability and level the wings. It does this because the rolling of the wings causes a slide slip in the direction of the low wing. This side slip causes the lower wing to present at a greater angle of attack than the high wing - thus the low wing creates more lift and so rises to level out the original roll disturbance. Too much dihedral causes a Dutch Roll effect - too little and you get neutral stability in roll. Wikipedia has a very easy to follow explanation. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 17, 2011 Share Posted June 17, 2011 Posted by AlanC on 17/06/2011 10:22:52:Many thanks for all the replies and the explanations of dihedral. As usual the forum comes up trumps again! Now am I AlanC or Alan C? I've heard of split personality disorders, I think I'm suffering one now. LOL - As the longer serving of the two Alans..... you stay put AlanC Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted June 17, 2011 Share Posted June 17, 2011 is this Alan c who stays, or Alanc cor, all confused, Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted June 17, 2011 Share Posted June 17, 2011 Thanks Alan...I see you have changed yours Its easy now - the guy who works for YT International is A Cantwell The guy who doesn't is AlanC Quote Link to comment Share on other sites More sharing options...
Alan Cantwell Posted June 17, 2011 Share Posted June 17, 2011 SHHHHH dont mention YT, Dave will have a fit, Quote Link to comment Share on other sites More sharing options...
Ernie Posted June 17, 2011 Share Posted June 17, 2011 Hi guys, what about anhedral ernie Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 17, 2011 Share Posted June 17, 2011 Posted by A Cantwell on 17/06/2011 17:25:05:SHHHHH dont mention YT, Dave will have a fit, whY noT? Quote Link to comment Share on other sites More sharing options...
Ben B Posted June 17, 2011 Share Posted June 17, 2011 Anhedral makes a plane unstable. Some modern fighters deliberately have anhedral so the plane is fundamentally unstable and then they stabilise it with gryo type electrical trickery. The advantage of having an artificially stabilised unstable plane is that you can do very rapid rolls etc due to the lack of self-stabilising forces. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted June 17, 2011 Share Posted June 17, 2011 You often find anhedral where there is significant sweepback. Sweepback has a similar effect on roll stability as dihedral so the anhedral cancels some of the excess. Quote Link to comment Share on other sites More sharing options...
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