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How much dihedral for low wing 3Ch. plane?

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How much dihedral for low wing 3Ch. plane?

Old 02-13-2007, 09:08 AM
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fokker20planes
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Default How much dihedral for low wing 3Ch. plane?

I have been in a long process of kit bashing a 3 channel low wing plane. All I want is something with rudder elevator and throttle. It will resemble a Tidewater Pronto, but I want to use a Sig foam wing instead. I'm sure I will have to cut the wing and add dihedral but I was wondering what the minimum is I will need. Wing is about 47", power will be Max .20. Fues is already completed. Any help wil be greatly appreciated.
Thanks!
Old 02-13-2007, 02:49 PM
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red head
 
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Default RE: How much dihedral for low wing 3Ch. plane?

I'm just guessing ( that way someone that knows will jump in ) but I'd say with one side of the wing laying flat you should have about 3" from tip to building board on the other wing half. ENJOY !!! RED
Old 02-13-2007, 03:43 PM
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2slow2matter
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Default RE: How much dihedral for low wing 3Ch. plane?

My kadet plans (high wing) called for 6 inches in the above described manner. I cut it to 3 (1 1/2 on each side) and added ailerons. why not just add ailerons? I don't believe I've seen a 3 channel low wing plane. sounds like a lot of wingtip scraping to me.
Old 02-13-2007, 04:19 PM
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Default RE: How much dihedral for low wing 3Ch. plane?

with a 47 inch span the usual amont would be about 4 1/2 inches.just remember that as you decrease the amount of dihedral the rudder will become less effective.low wing 3 channel planes fly just fine if thr rudder is effective.the minimum would be an amount that would bring the wing tips to the centerline of the fuse,in other word if the fuselage is 3 inches deep[top to bottom at wing saddle] then 3 inches would be the minimum .
Old 02-14-2007, 05:43 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

I'm with 2slow2matter why 3 channel?
Old 02-14-2007, 07:33 AM
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fokker20planes
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Default RE: How much dihedral for low wing 3Ch. plane?

Okay, Jetmech and 2slow, because after 27+ years of flying I've learned that most 3 channels are as much fun as 4. One of my fellow local flyers even flys single channel planes even though he owns a four channel radio. (and has been in this hobby loooong before me!) Ever see a Tri-Squire fly with rudder only? It's not only a hoot but it takes some talent to fly. You know what they say. Different strokes for different folks!

Thanks aerowoof and red head, that sounds like a reasonble place to start.
Old 04-11-2013, 01:57 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

ORIGINAL: fokker20planes Okay, Jetmech and 2slow, because after 27+ years of flying I've learned that most 3 channels are as much fun as 4. One of my fellow local flyers even flys single channel planes even though he owns a four channel radio. (and has been in this hobby loooong before me!) Ever see a Tri-Squire fly with rudder only? It's not only a hoot but it takes some talent to fly. You know what they say. Different strokes for different folks!
I know this post was made 6 years ago, but after reading this thread, just wanted to say how much true this statement is. Not always is one required to have full house to have fun. Sometimes the greatest fun is through simplicity, pure and simple. [8D]
Old 04-11-2013, 02:59 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

Wow, I posted this six years ago? Time sure fly's! Sorry, but I never did complete that plane. It still sits half built. Probably when I retire I'll have time to build and fly. I agree though that 3 channel planes are as much fun as 4.
Old 04-11-2013, 03:36 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

Your post confirmed for me to go ahead and prioritize my Tidewater Pronto as the next build.
Old 04-11-2013, 05:45 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

I realize this thread is an old one but its a good questions that deserves a good answer and it was answered by Aerowolf but may have been been passed over a bit.

Without getting into an argument over channel counts There are many viable reasons why one may want to use control over only two axis or even less that can range from simplicity to cost or even nostalgia. So I wont go there.


Yes it is quite possible and practical to use no ailerons on a low wing airplane. The key as pointed out by Aerowolf is dihedral. Dihedral is required anytime only rudder is used for directional control and its works
because when an airplane yaws from rudder imput the dihedral will cause a roll in the direction of the yaw (this is roll coupling) and now the airplane can turn after the roll has occured.

The speed at which this roll is caused from the yaw is dependant upon how much dihedral is used. The more dihedral the faster the coupled roll will occur and the smother the turn will appear.

So Roll response is actually opposite of what occurs with an airplane that uses aileron. With full three axis control reducing the dihedral will have the effect to a point of increasing roll response but with an airplane using only two axis control (rudder, elevator only) reducing the dihedral will reduce roll response. This to a point that all roll control is lost, A totally flat wing will not work with only rudder.

John
Old 04-11-2013, 05:52 AM
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jester_s1
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Default RE: How much dihedral for low wing 3Ch. plane?

Not to be argumentative, but I'd have to disagree with your last statement JB. A high wing plane with a fairly thick fuselage will still have some roll coupling with rudder use. It may not be enough to make 3 channel control practical, but it is a factor in deciding how much dihedral is needed. My Cub that has no dihedral will roll into a rudder only turn fairly well due to the fuselage blocking airflow to part of the inside wing. A low wing plane won't have that effect, so it will need a lot more dihedral to work with rudder only control than a high wing plane does.
Old 04-11-2013, 06:21 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

Sure I would not argue and it is a matter of degree but a flat high wing will still not be very controllable even with a high wing but the subject was a low wing if I read correctly and that would be completely uncontrolable if totally flat and no ailerons.

I remember one low wing ship I built in the past with to little dihedral and no ailerons that was a nightmare in flight. In desparation since cutting the wing in two to change dihedral did not appeal to me I cut the wing tips off and reconnected with lots of dihedral and it worked like a charm.

Now ya wanna talk crooked wings how about a high wing with anhedral That really makes for cool flying airplanes. Hm wonder how that would work without ailerons? bet it would gotta try that someday.

John
Old 04-11-2013, 07:27 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

The merit to the Pronto is simplicity at its best. It is 48 inches (1219 mm) wingspan, solid balsa rudder and stabilizer, slab sided fuselage and constant chord wing make for quick building. Using a .19 to .25 motor and 2-1/2 lb weight will give it better windy weather handling than an .049 sized plane that weighs half its weight. Being a low winger, it has a healthy amount of wing dihedral, so it should roll well in turns.

Regarding ailerons versus rudder with dihedral, one picks and chooses their poison for 3 channel airplanes [:-]. They both have advantages and disadvantages. I think they are both fun. [8D]

I think even rudder only is fun. I don't do it because it is nostalgic, I do it because it is fun, pure and simple.
Old 04-11-2013, 07:52 AM
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fokker20planes
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Default RE: How much dihedral for low wing 3Ch. plane?

So, now that my interest is piqued again on this topic, what amount of dihedral is the Pronto calling for? I'll file this info away so that "SOMEDAY" when I get back to building I wont have to look this post up to find the answer.
Thanks GG!
Old 04-11-2013, 08:09 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

A friend wanted me to build him an old timer so I built him the Satyr designed in about 1946 for free flight. To convert it over to three channels I removed about half the dihedral so it is at about 4.5 inches. Two and three channel is a hoot to fly. Takes a bit of getting used to but once upon a time it was all we had. All but one of my electrics have been three channel. My first RC plane was a two channel 1/2A Cub. I have never built a three channel low wing though but on high wing free flight conversions I remove about 50% of the dihedral. Old three channel kits I find and build I leave it as designed. OK, I see they really fixed the photo problem!! Now it lets you think you have posted a photo instead of giving you an error 500. That's much better then it was.
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Old 04-11-2013, 09:20 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

I've heard the same advice by others to take out half the dihedral, Gray Beard on converting free flights to R/C, particularly those with considerable dihedral or polyhedral. (BTW, RC Universe is having server problems again, your pictures aren't showing unfortunately. [&o])

I concur with your statement on the 2 and 3 channel planes. At one time it seemed a most cost effective way and superior to escapements was flying on 3 channel Galloping Ghost, an acceptable proportional control with rudder and elevator behaving interactively (turns gave up elevator), and auxiliary throttle control sequentially through a push button. One "servo" was the single analog 3 function Rand electric motor actuator to make it all happen. Also remember the 6 channel reed systems providing 3 channel control.

Regarding true proportional control, I remember those Orbit multi channel proportional servo systems costing over $500 in the 1960's, which was a considerable amount of coin for those days. Inflation has gone up with say what? 6 or 7 times, bringing the cost of those radios now up to the jet turbine engine cost levels. I remember America's Hobby Center ads in the model mags advertising a single channel transistorized mini single escapement system (dry) for $40 then.

fokker20planes, when I get a chance to pull the box out and look over the plans, I'll post the Pronto dihedral requirements.
Old 04-11-2013, 09:30 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

The Tidewater Pronto has 7 inches of total dihedral, or 3.5 inches in both panels. There's your answer. Dave Robelen knew what he was doing.

Jim
Old 04-11-2013, 10:41 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

The plane I tried to show was the Satyr, it was a free flight design but looks just like a lot of the old RC planes. Back in around 1960 I was in Calif. flying U-Control and Free flight at the dam basin. RC was way beyond the cost of a kid but we used to always go over to the RC area and watch the big guys crash there planes. Just getting them off the ground was fun to watch. We were thrilled to see them cranking up the rubber bands and counting knots to make sure they had enough power to operate the controls. Computer radios have made RC a bunch better not to mention servos and receivers. I'm still building my own planes though but CA glue has made it another easy thing to do. Dihedral has always been a hot topic but I do usually remove it about 50% on the really old FF conversions. Seems to work OK and the planes are still big floaters and easy to fly.
Old 04-11-2013, 11:37 AM
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Default RE: How much dihedral for low wing 3Ch. plane?

Gray Beard, I think you mean this one:

[link=http://www.outerzone.co.uk/plan_details.asp?ID=3127]Outerzone.co.uk 65in Satyr FF Plan[/link]



Yes, I remember the advice, it had something to do with having better rudder control by reducing the dihedral to norms. The rudder planes by Ken Willard had moderate but not excessive amounts of dihedral. Low wings require more dihedral for stability under rudder control due to location below center of gravity. I guess too much dihedral is as bad as not having enough under radio control.
Old 04-11-2013, 12:22 PM
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Default RE: How much dihedral for low wing 3Ch. plane?

For a 3 Ch Aileron-less airplane 3° is typical.
Old 04-11-2013, 12:43 PM
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Default RE: How much dihedral for low wing 3Ch. plane?

It depends on several factors, the most important being wing location. A high wing plane gets a dihedral effect even from a straight wing. It's not enough for good three channel flight, but it doesn't need a lot of dihedral. A low wing has an anhedral effect with a straight wing. The OP asked about something "like the Pronto" which is low wing.

If he builds a low wing plane with no ailerons then using the dihedral recommended for a high wing plane will result in skidding turns at best. That's why Robelen put so much dihedral in the Pronto. Look at his high wing 3 channel designs and you will see much less dihedral.

The Pronto is a well-known and well-liked airplane. Why wouldn't you use what has been proven to work?
Old 04-11-2013, 02:31 PM
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Default RE: How much dihedral for low wing 3Ch. plane?

both my full scale cub,,a clip and a stadard would takie a mile to turn around using rudder only. it would be a very long flat slide. my instructor told me that the elavator turns the airplane,,,the vaerilon and rudder makes it cordinated.i can make a real plane dance but after years of rc flying my turns arestill crapy but fun!
Old 04-11-2013, 03:38 PM
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Default RE: How much dihedral for low wing 3Ch. plane?

A Cub has very slight dihedral, not enough for good rudder only turns. But a low wing plane with the same dihedral as a Cub would have adverse roll with rudder, i.e., give it left rudder and it would roll right. Much worse. Low wing planes need more dihedral than high wing planes if you want to do rudder only turns.
Old 04-11-2013, 03:42 PM
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Default RE: How much dihedral for low wing 3Ch. plane?

I'd say you need enough dihedral to resemble the letter
V
Old 04-11-2013, 03:42 PM
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Default RE: How much dihedral for low wing 3Ch. plane?

I checked the plans just now, yes, the Pronto is 3.5" (89mm) per wing tip or total of 7" (179mm) if one wing panel is laid flat on the building board as stated by buzzard bait.

I certainly don't have flying down to a science. I'd like to think of myself as a sport pilot / perpetual learner / beginner, fred985.

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