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How much dihedral?

Old 05-15-2011, 12:18 AM
  #1  
earthsciteach
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Default How much dihedral?

I'm putting together an indoor flyer. Its going to be a low wing, 4 channel plane. From what I understand (thanks to folks at this forum) is that too much dihedral is counterproductive to planes with ailerons.

I want it to be nicely maneuverable, capable of snappy rolls (and snap rolls, I suppose) but a flat low wing just isn't aesthetically pleasing to me. IMHO, that's for those fancy, mid-wing aerobatic planes.

So, how much dihedral is not too much?

Thanks!
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Old 05-15-2011, 12:36 AM
  #2  
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hello teach, the question is to simplified since we don't know what it is you want to build.....ws,weight,length...ect..ect... .

true ,to much dihedrial will spoil ailerons,so find a good blue print to build from and go with a tried and true design. and most of all.....have fun!!!
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Old 05-15-2011, 12:37 AM
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Just enough so it does not look droopy. If you want highly aerobatic you need to keep the amount fairly low. Not sure how much because it depends on how large the plane/wing is.
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Old 05-15-2011, 12:44 AM
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Hi Patrick
As the others have stated it all depends on the airframe weight, size and shape and also the airfoils size, shape and camber
Since this is your own original design your going to have to experiment to find out
Let the fun begin
Take care dear friend
Yours Hank
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Old 05-15-2011, 12:56 AM
  #5  
earthsciteach
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Message received loud and clear! Good thing I can make a set of wings for, well, free. My plan is to have "just enough" dihedral to be pretty.

The plane is based on the Globe Swift, in my opinion, one of the prettiest private planes ever built. Wingspan is similar to the PZ ultramicros. Weight is a bit up in the air at the moment. Shooting for around 30-40 grams.
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Old 05-15-2011, 01:02 AM
  #6  
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You got it earth just enough to make her look good. I wish more of you guys would do build threads on the new planes you are building. joe
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Old 05-15-2011, 01:10 AM
  #7  
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I do a lot of design work and there are a number of ways to include Dihedral with out actually have and angle at the root section . Dihedral is use for stability and and aircraft say with rudder elevator control only requires that dihedral for auto stability,the ability to self level if left untouched, ailerons negate that requirement as you have full 3 axis control.
and having excessive dihedral is counter productive on aileron control ,as in fighting against aileron input. Depending on size of model will indicate dihedral require I start at 60" span which normally has 1/2" under each tip . This is achieved by building the wing upside down so the natural taper of air foil from root to tip creates that dihedral on the lower surface of the wing, however the upper surface will be dead flat. If its a foam wing I cut it using the same method. So Basically minimum dihedral is required for an aileron model .

P.S. Good luck with it
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Old 05-15-2011, 01:15 AM
  #8  
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Originally Posted by StephenW View Post
I do a lot of design work and there are a number of ways to include Dihedral with out actually have and angle at the root section . Dihedral is use for stability and and aircraft say with rudder elevator control only requires that dihedral for auto stability,the ability to self level if left untouched, ailerons negate that requirement as you have full 3 axis control.
and having excessive dihedral is counter productive on aileron control ,as in fighting against aileron input. Depending on size of model will indicate dihedral require I start at 60" span which normally has 1/2" under each tip . This is achieved by building the wing upside down so the natural taper of air foil from root to tip creates that dihedral on the lower surface of the wing, however the upper surface will be dead flat. If its a foam wing I cut it using the same method. So Basically minimum dihedral is required for an aileron model .

P.S. Good luck with it
Hi Stephen
Thanks for the great tips
And your Fouga is absoulutely gorgeoussuperb job
Take care dear friend
Yours Hank
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Old 05-15-2011, 01:31 AM
  #9  
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Here's a couple of pics of where I'm at so far. Which is basically a total mess in the kitchen, agitating my wife. I need a work area.

The veneer is the wing template. I'll be cutting that out in a bit.
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Old 05-15-2011, 01:32 AM
  #10  
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oops, no pics
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Old 05-15-2011, 01:57 AM
  #11  
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For what it’s worth… (2 axis control elevator, and rudder) one will know when it’s incorrect; it will not roll and turn properly!
It has been my experience that the aircraft may become so stable that the control inputs do very little to roll/turn the aircraft… ask me how I know (LOL).
Many of the aerodynamics for modeler’s books have good rules of thumb...
Cheers
Dave
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Old 05-15-2011, 02:34 AM
  #12  
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Originally Posted by earthsciteach View Post
I want it to be nicely maneuverable, capable of snappy rolls (and snap rolls,
I don't the near Globe Swift will meet your aerobatic goals by the way. For this project you might want to create a nice flier - then work on a better aerobatic airframe if snaps are what you want. And there is nothing wrong with doing a more scale model first.

For what it is worth, I would use about 1cm of dihedral on that ship with those thick surfaces. Flat plate wings and tail feathers work very well in these small planes.

Mike
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Old 05-15-2011, 02:59 AM
  #13  
earthsciteach
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Thanks, guys. I appreciate the input.

I am not looking to set the sky on fire with this plane, but do want it to be capable of fairly quick rolls and barrel rolls. I know snap rolls are a lot to ask for as the wing has to stall and recover very quickly to accomplish this.

This is my first self-built RC plane (and my first 4 channel plane) so I know I am setting a high bar for myself. Really, I am just having fun experimenting with materials and methods. However, it MUST outperform my friend's micro F4U on back order from Banana Hobby.
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Old 05-15-2011, 03:13 AM
  #14  
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that looks nice make the ailerons 1/3 the wings width and add them to the wing that you have already, dont cut into the wing for ailerons, and make them full length, that will increase your wing area and give you lots of aileron control at slow speeds, for the dihedral, give your plane about 3/4" at the wing tips, no more than that. Also, make your elevator control surface 2/3 of what you have now, so 1/3 will be your stabilizer, hope that helps, Chellie

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Old 05-15-2011, 03:48 AM
  #15  
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Chellie, you have an amazing feel for these things! I did increase the wing area a good bit based on your advice. Haven't calc'd the wing loading as I am not sure of the weight at this point. My gut is that it will come in a fair bit lower in weight than my initial estimate.

So, full length ailerons at 1/3 wing width. Would you use foam or go with balsa for those? I know the rudder is on the small size, but I'm more concerned with the lines of the plane, at this point. I can always make a bigger vert. stab. if I need to.
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Old 05-15-2011, 05:22 AM
  #16  
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Originally Posted by earthsciteach View Post
Chellie, you have an amazing feel for these things! I did increase the wing area a good bit based on your advice. Haven't calc'd the wing loading as I am not sure of the weight at this point. My gut is that it will come in a fair bit lower in weight than my initial estimate.

So, full length ailerons at 1/3 wing width. Would you use foam or go with balsa for those? I know the rudder is on the small size, but I'm more concerned with the lines of the plane, at this point. I can always make a bigger vert. stab. if I need to.
Hi if you have depron i would use that because its a very stiff foam, if not use Balsa, the rudder is fine, just use 2/3 of it for the control surface. your elevator is fine, just use 2/3 of it for a control surface. the wing you have now is fine, just add the ailerons to the trailing edge to make the wing wider. by making the ailerons full length, you will be using the prop wash to help the ailerons out.

BTW what motor and lipo will you be using ? here is a suggestion

http://www.headsuprc.com/servlet/the...0-Sport/Detail motor $10.95

http://www.headsuprc.com/servlet/the...mah-35C/Detail lipo 2 cell $6.95

http://www.headsuprc.com/servlet/the...-10-Amp/Detail ESC $16.95

http://www.headsuprc.com/servlet/the...ers-TWO/Detail $2.25 6x3 prop = 5.5 oz of thrust @ 3.5 Amps

http://www.headsuprc.com/servlet/the...ers-TWO/Detail $2.15 5x3 prop =4.5oz of thrust @ 2.7 amps

2mm prop adapter a must have http://www.headsuprc.com/servlet/the...r-2.0mm/Detail $2.50

Tell Jeff @ Heads Up Rc that Chellie sent you



Power Up 180 Sport Outrunner Brushless Motor



The Power Up180 Sport is a 0.35 ounce (10 gram), 2300KV outrunner brushless motor that works well on very small parkflyers, and on models intended to be flown indoors. This motor comes with 2.3mm male connectors installed, and female connectors are included for the ESC.

The Power Up180 Sport works well on models weighing about 4 to 8 ounces. We suggest using the GWS 7035 prop or the GWS 6030 prop, and our 7.4v 400 20C or 7.4v 600 20C Lipo batteries. The props can be mounted using our 2mm Set Screw Type Prop Adapter.

We recommend using the Power Up 10A ESC with the Power Up180 Sport. This speed control has 2.3mm female connectors installed, which match the male connectors installed on the motor, so no soldering is needed.

MOUNTING OPTIONS: A
6mm Firewall Mount is included with this motor. A Stick Mount is also available, sold separately.

Recommended props when using 2 cell (7.4v) Lipo batteries:

The GWS EP 7035 prop produces about 6 ounces of thrust at 4.5 amps.

The GWS EP 6030 prop produces about 5.5 ounces of thrust at 3.5 amps.

The GWS EP 5030 prop produces about 4.5 ounces of thrust at 2.7 amps.

The GWS EP 5043 prop produces about 4 ounces of thrust at 3.5 amps.


Power Up 180 Sport Specifications:

Weight = 0.35 ounces (10 grams)
Diameter = 0.7 inch (18 mm)
Motor length = 0.78 inch (20 mm)
Shaft = 2mm

Connectors = 2.3mm male connectors installed
Voltage = 6.0 - 8.4 (2 cell Lipo battery)
Current = maximum of 5 amps for 60 seconds
KV = 2300

PRICE: $10.95

Last edited by CHELLIE; 05-15-2011 at 06:50 AM.
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Old 05-15-2011, 01:52 PM
  #17  
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If you are trying to build a 30g airplane there is no choice what you have to use - foam. Again learn from the masters - and see what Horizon used for their stuff to keep it light - and take a look at the T28. It flies wonderfully and has some good "cheater" aspects for this your first design/build. You picked a challenging size by the way!

The Sbach is all all out acrobatic ship. Notice the HUGE difference in control surface size and the lack of dihedral (little if any).

Two different planes for two different goals. Again I say make you choice the Swift scaleish bird but don't expect it to set the world on fire with aerobatics. If you want that you need a different design.

Mike
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Old 05-15-2011, 03:16 PM
  #18  
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I love the Globe Swift. It was a neat little plane. It's not modeled very much. Corvin Miller built a Master Scale one in 1993 for Top Gun. It was awesome.

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Old 05-15-2011, 03:24 PM
  #19  
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If the motor and lipo needs to be smaller, here is a 5 gram brushless motor

http://www.hobbyking.com/hobbyking/s...idProduct=6312

http://www.hobbyking.com/hobbyking/s...dProduct=11871
hook two of these batteries in series for a 2 cell lipo
http://www.hobbyking.com/hobbyking/s...idProduct=4318
6 amp esc


(Jo)Hannes ( members like this guy) 208 thumbs up!First the 10g Brushless and now the 5g, great job UH!!!
I Use 4 of these in my C130 www.link with the 6A Turnigy controllers.
Here are some measured data with various props.
with 2S Lipo:
GWS 3020 prop. 1 amp. ~38g thrust
GWS 3030 prop 1.2 amps, ~44g thrust
GWS 4025 prop 11,000 rpm, 1.4 amps, ~53gr thrust
GWS 4530 prop 9,000 rpm, 1.6 amps, ~62 gr thrust
GWS 4540 prop 1,9 amps, ~65g thrust
GWS 5030 prop 8,950 rpm, 1,83 amps, ~76g thrust
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Old 05-15-2011, 03:36 PM
  #20  
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Thank you Mike for posting this pic, thats what I was talking about wide ailerons, full length, big elevator about 2/3 being the control surface, I agree that foam will be lighter for the main wing, 3mm depron will work great for that. get some 6mm depron too since you like to build even the midwest cellfoam 88 at hoppy people will work well.

http://www.rcfoam.com/index.php?cPat...bf08f91d1db4d9


Last edited by CHELLIE; 05-15-2011 at 04:15 PM.
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Old 05-15-2011, 03:43 PM
  #21  
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on the small micro lipos, dont even worry about balancing them, they are cheap enough if they dont last to long, and before there were balance plugs on lipos, there were none this is a great little lipo charger, i use mine all the time, i have more expensive chargers, but i like this one the best, for my smaller lipos of 1300mah and smaller, it will charge 1 to 3 cells, I use a blinky balancer if my small lipos have a balance plug on them

http://www.aeromicro.com/Catalog/gre...er_3964431.htm





Specifications:
  • Input Voltage: 11-15V DC
  • Battery Types, # Cells: 1-3 Lithium-polymer cells (3.6-11.1V Li-Po)
  • Fast Charge Current: 250, 500, 1000mA
  • Fast Charge Termination: "constant current/constant voltage"
  • Status Indicators: High intensity blue LED, audible buzzer
  • Input Connectors: Alligator clips
  • Case Size: 2.2" x 0.9" x 3.5" (56mm x 23mm x 89mm)
  • Weight: 4.35oz (123g)
  • Length of Input Lead: 27" (686mm)
  • Length of Output Lead: 4" (102mm)
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Old 05-15-2011, 06:00 PM
  #22  
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Thank you so much for the info, guys! The motor/battery info INCREDIBLY helpful, Chellie. I am hoping for performance similar to the Parkzone Ultra Micro warbirds. The planform just isn't an "unlimited aerobatic" performance type plane. For whatever reason, those Extras and Lasers don't appeal to me very much. Maybe I'll look for that type as my skills progress. I'm pretty hung up on warbirds and classics right now.
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Old 05-15-2011, 06:12 PM
  #23  
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Here's the real deal. Such a beautiful plane!
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Old 05-15-2011, 07:12 PM
  #24  
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A couple more pics of progress:
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Old 05-15-2011, 07:26 PM
  #25  
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So many ways to sort out dihedral… a flat plate wing with small kicked up tips would be a simple solution
Fly it as built and see if it is happy… can always add tip dihedral later
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