diahedral??
 

hey out there!! i'm building a rudder and elevator plane and want very good aerobatics, i think the diahedral should be somewhere around 12 to 15 degrees?? is that a good place to start?? thanks, bill w.

diahedral??
 

Hi Bill,
Dihedral>
Basically this is a stability factor, tends to right the craft laterally.
All airplnes without ailerons should have some dihedral.
Amount depends up other design factors, such as wing location
vertically. A high wing design requires less than a low wing for
example. Also amount of lateral area which is depicted by a side
profile. Lots of L.A. requires less dihedral.
A high wing cabin style craft does well with 5 degrees,
A low wing would need 10 deg, or more.
Excessive dihedral limits maneuverability.
Hope this is of some help.
Good luck!

Hal deBolt

diahedral??
 

hi hal, it sure does, thanks a bunch for the info...i've been building models for over thirty-five years and taken out and put in diahedral....built a couple of the .049 planes that came as full size plans in model builder, but never wrote down any numbers....mostly did a TLAR, (that looks about right), when building, but, didn't want to start my combat "bat" rudder plane with out a known starting point....and from your info it looks like i need to start between 5 and 10 degrees..the wing sits on top of the flat side of the bat and the tail surfaces are just less than an inch lower than that....and its a short coupled platform also.. thanks again, bill w.

diahedral??
 

brickwoodward,

If you want to be able to do what most people consider aerobatics, you will probably want ailerons. I don't think elevator & rudder will do it.

banktoturn

diahedral??
 

I'm a little confused here..... Hal wrote "Excessive dihedral limits maneuverability. "

With a rudder and elevator plane the primary roll response comes from the interaction of the dihedral responding to the yawing that is induced by the rudder. So if you want a snappy rolling model then you want lots of dihedral. If you go back to model designs of the late 50's and early 60's when Class1 for rudder only and throttle and Class 2 for rudder, elevator and throttle the aerobatic designs for these models used closer to 10 or 12 degrees of dihedral per panel and at least one model biplane design used closer to 15 degrees. Sure it looked like a pigeon with broken wings but this was how they built them to work with the class rules. Yes the model will want to return to level flight quicker after the rudder is neutralized with the dihedral but if you don't have the dihedral then it's not going to roll very fast in the first place.

At one point in my modeling life I had a left over 6 foot span Malibu glider. I added an Enya 09 to the nose and took it out to re-aquaint myself with radio control flying after a 6 or 7 year layoff. That glider turned out to be VERY aerobatic thanks to the gross amounts of poly-hedral and a large rudder. Full rudder would yaw the model visibly from it's flight line and then the polyhedral would make that puppy roll like it was on a string. And I don't mean lazy barrel rolls. These were surprisingly axial at a roll rate of about one roll in 1 1/2 seconds or so.

So to my way of thinking you'll want to aim for closer to the 10 degree mark rather than the 5 degrees. And I suspect using a flat center panel with tip dihedral at a higher 15 or 20 degree angle would work even better because you'd concentrate the dihedral effect out at the tips where the leverage would make the roll coupling force more effective.

And incidentally. You can fly inverted with a rudder elevator model very successfully provided you're airfoil isn't too high lift a type. Just use the rudder control like it's an aileron control. Sure the rudder moves the opposite way with the model inverted but then the roll couple works backwards too so the net result is that you have a model that flies inverted just fine but it needs a bit more attention because the dihedral obviously wants to try and roll it back upright so you need to catch it with a little bit of rudder to correct it. I flew a fair amount of inverted flight during a slope soaring session with a poly hedral Top Flite Metric a bunch of years ago also. At first I didn't think it would do it but it wasn't any worse than balancing a broom handle on your finger tip. I ended up figure 8'ing back and forth across the slope inverted the whole time and STILL going up in the strong lift dispite the thermal glider airfoil. Great fun....

diahedral??
 

Just to amplify BMathew's explaination a bit. The greater the dihedral, the less yaw (rudder authority) it will take to produce a given roll response and the less "barrel" there will be to the rolls. The more dihedral, the more the plane will try to right itself from inverted and the more difficult it will be to sustain inverted flight. The trade off between the conflicting objectives of inverted flight capability and near axial roll capability will determine how much dihedral is best for you. If your reflexes are faster you can use more dihedral than if your reflexes are slower. Low dihedral aileron ships don't have to deal with that dilema.

diahedral??
 

I don't know much about aero engineering but i recently saw a combat event for class B. There were 2 guys with R/E only planes and they were Very good. One placed 3rd in the event. The foam wings had 30 deg. dih. Wing deminsions are 45 x 10 1/2 . Looked very strange but they flew well. KEITH

diahedral??
 

i sure do want to thank all of you that responded...i read each, studied, held the wings up at various angles, and after using a little TLAR and combining all your responses, i settled on 16 degrees.....wings are 48 and 11 1/2 chord......for Class B open.... thanks again, bill w.

Dihedral for Aerobatics
 

Hello

For expierience I should tell you that a RUDDER/ELEVATOR plane with high dihedral doesn't work well as an aerobatic should, I strongly recommend to get ailerons instead of rudders with 0° or 1° dihedral in case you don't want to be overcontrolling the plane for steady flight.


Best Regards, Roderick

diahedral??
 

hi roderick, the plane will be used in AMA open combat, class B. it probably will never see steady flight except to and from the combat zone...i had a chance to see both aileron and rudder only planes in the same meet and the rudder only planes could manuver every bit as good as the aileron planes and in some manuvers, they were more agile.....i did have a rudder only sport plane one time and it was almost the most fun i'd had with any plane....very aerobatic and nimble.....thanks for your response and have a great day, bill w.

diahedral??
 

Aerobatic is usually taken to refer to the ability to do predetermined precision aerobatics as in aerobatic competition.

Maneuverability (the ability to change speed, direction and orientation quickly) is what you want in combat. In my opinion, 12 degrees of dihedral on each side will give you just about all the maneuverability that you will want. When you go inverted you won't stay there long and neither you nor your opponent will know which way you are going to roll out. The spiral stability imparted by dihedral will allow you to take your eyes off your model briefly to look around without loosing control. This is a big advantage in combat. It also reduces the pilot work load which is another advantage. There is no particular combat advantage to being able to do axial rolls or to do sustained inverted flight.

diahedral??
 

very well put ollie!!! thank you....i shall build another set of wings and make it 24 degrees.....i bought a sheet of blue foam and i intended to experiment with different settings....thanks again, bill w.

diahedral??
 

Hi y'all,
Most if this info neglected to say if the angle was for one panel
or the entire wing. If panel angle was 5 deg, entire wing would be
10 deg.
A bit of AMA history> Prior to the 53 Nats R/C was flown as classes, rudder only class one, rudder and elevator was two,
three was multi.
One of the last Nats with classes saw the Ambroid "Charger"
clean up the troops in class one.
An earthshattering event was when Jack Port and his rudder only
"High Q" in the first open class Nats beat all the multi reed planes.
If one is looking for aerobatic rudder only it would do well to check these two out.
As memory indicates I do not believe either one had excessive
dihedral.
Good luck and have fun!

Hal deBolt

dihedral.

diahedral??
 

Good grief, I've actually got that Charger article. It's a 25'ish sized high wing cabin model that used an older .35 on it. It was designed by a Milt Boone and was published in the Jan 1960 American Modeller. I guess Ambroid picked it up as a kit after that.

The amount of dihedral isn't excessive. It's a 48 inch span with 2 1/2 inches under each tip. The fin and rudder aren't particularly large. I suspect the smaller vertical area has something to do with it being snappy. A little spirally unstable perhaps.

If any of you are interested in this old classic I could scan the magazine article I have sitting here in front of me and get it on in the next few days.

diahedral??
 

thanks ya'll, i'll check the space under each wingtip..i dont think it is much more than 2 1/2, got me thinking about a couple of old mags i have out in the building room.....a jan 1962 model airplane news and a dec 1967 man.......neat looking thru them....electric free flight with a foam wing and one time use battery packs.....plane is a dollar and battery packs are 20cents each......oh, for those days.....but then i didn't even have 20 cents!!!!!!thanks to all for the help....bill w.

diahedral??
 

Hi Bruce,
Nice to hear from you and to know you are aware of the Charger.
Milt Boone was Bob Dunham's Orbit superintendant. Bob once said it was Milt that operated Orbit, not him.
I have no use for the Charger other than to know it was a fine
design. Perhaps an example of putting everythiong properly together to accomplish a purpose. Result also made a nice sport
flyer with reasonable power.
The Vintage R/C Society objective is to pomote the use of antique designs many being equal or better than todays
It would be nice to see some Chargers at the coming reunion.
I will attach the meet announcement, it will be another great one!
Good luck and be good!

sorry about the attachment forgot this is not E-Mail
If you would like it drop me an E-Mail note, OK?

Hal deBolt [email protected]

dihedral math
 

For those that want to compare Degrees to inches , the math is ---.017 per deg. per inch. Example -- If you want 5 deg. Its 5 X .017 X length of wing . KEITH

diahedral??
 

Thanks for the offer Hal but if it's not being held in Washington or Oregon it's probably a non starter for me. I like some of these older designs but not enough to go out of my way for them.

Although I seem to be developing a desire to master rudder only after all these years. My first ever radio model was a Goldberg Jr Falcon with a, ready for this one?, Command Master brick in it. It was the one type of flying that beat me.

Actually I've since flown a Littlest Stick on rudder only using an old ACE pulse setup and get good flights on it so I guess I've mastered rudder only after all. I'd still like to try one that was a little bigger though.

I've still got my old Controlair Galloping Ghost rig........ Perhaps I should make up a Jr Falcon or a Minnie Mambo or something...... Nah, the range was so bad on that reciever that I had to use a vertical whip on the model to keep it from going out of range in ony a few hundred feet........Ruined about 3 or 4 models until I figured that one out.

By the way. It's sort of funny in a nice way after all these years of seeing your face with a corncob pipe stuck in it from the magazines to actually be chatting with you. :cool:

RE: diahedral??
 

Hi Hal
I just came across this thread when searching the net for the Charger - I got into some nostalgic mood today and just remembered when we all used Ambroid cement (or similar (we had Cemento Aerobrás down here in Brazil) and that reminded me that I built 2 of them, in one of those old Ambroid ads there was a 3-view which I enlarged and freely built over these plans. I modified them to full house controls.
I enlarged one some 20% and powered it with an Enya.19 Controlline engine fitted with an OS Carb, and controlled it with a Graupner/JR Radio.
Later on I built another one, this time in the original size and powered it with an OS .10 and later converted it to electric power using an surplus Mabuchi-Type 550 can motor, from a crashed Goldberg Mirage 550. Radio as always my old, reliable Graupner/JR.

Well, that´s it.

Marcus