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Recommended Dihedral for "Flyer"?

#1
Hi, after my maiden flight of the Flite-Test "Flyer" I built, someone looking at the video suggested that I might need more dihedral. Right now, it's at about nine or ten degrees. The commenter suggested 15 degrees. I arrived at the current angle by following the suggestions in the Flite-Test video, where you lay the wing on top of the power pod.

The YouTube video is titled Maiden Flight of a Customized Flite-Test "Flyer" RC Airplane. The flying starts at about five minutes in. With some things I've added to the model, it weighs in at ten ounces.

I'd like comments on whether or not I should add some more dihedral to the wing. Other comments welcomed too, of course.

Thanks,
Bill
 

Hai-Lee

Old and Bold RC PILOT
#2
If your "Flyer" is flying OK then DO NOT MESS WITH IT!

Too much dihedral can lead to a serious handling issue called "Dutch Roll". In the extreme when you try to turn the overcoming of the lift of the lower wing takes a lot of rudder and as the wing lowers suddenly the lift disappears totally. and the craft will want to roll violently to the lower wing side. There is not enough rudder to counter this when it happens so you are along for the ride. Additionally the rudder to initiate the roll now pushes the nose of the craft earthwards, (vertically). Where there is not much height to play with this leads to a vertical landing often at full throttle! The result of such a landing is well known!

NEVER increase the dihedral for more stability as it causes more problems than it cures. Often I markedly reduce the dihedral of most FT models I build but the reduction is based upon the centre of mass and the crafts weight, (plus add a fair amount of previous experience).

Just what works for me!

have fun!
 
#3
Thanks for the info, Hai-Lee. So, I think I'll leave well enough alone as far as dihedral is concerned.

I know it's a difficult question to answer without having more info about the model, but does 9 or 10 degrees of dihedral seem reasonable? The center of gravity is where Flite-Test recommends it to be. And, as I mention earlier, the all-up weight of the model is about 10 ounces.

Bill
 

Hai-Lee

Old and Bold RC PILOT
#4
Most models I have ever built or flown have had dihedral angles of a maximum of 6 degrees on each side or a total of 12 degrees from one wing to the other. Any more than that and the plane is seriously dangerous as mentioned previously.

generally I tend to have little dihedral especially on light planes where the majority of the weight is below the wing centre of lift. this weight being lower gives rise to something called "pendulum Stability". It is a delicate balancing act to get the correct amount of dihedral and pendulum stability as increasing one normally the other to be reduced.

As stated previously also if the plane you are flying is flying OK do not try to fix it because, "IT AIN'T BROKE". If it currently has poor handling and you are a very experienced pilot then by all means adjust the dihedral but do so in small steps so that the changes can be noted and you can work out if the adjustment is going in the correct direction!

Just what I would do and have done!

have fun!
 
#5
When I said about ten degrees, I was measuring as shown in the attached image. I assume you are talking about airplanes that are controlled by a rudder and not ailerons.

As shown in the video, the flights were short, so it's hard to say what part the dihedral played in the handling issues. Once I've patched the plane up, I'll do some further flying and experimenting.

Bill
 

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