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Old Feb 25, 2012, 01:16 PM
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Originally Posted by Zor View Post
In a nutshell for a given airfoil there is an angle of attack for highest lift to drag ratio that will produce the smalles rate of descent. At this angle of attack the wing must have air forces (speed) that combined with gravity (weight) will result in balanced forces and thus stable gliding. The incidence angle of the tail will be set to maintain this balance at the best angle of attack and speed.
Zor
The first sentence is almost correct. The highest L/D ratio yields a glide that covers the maximum distance in still air. At a higher incidence angle, we get to the condition of minimum drag which yields the longest duration flights. At an even higher incidence angle, we reach stall. The horizontal tail feathers (stabilizer and elevator together) are adjusted to provide the desired incidence angle for any given situation.

When trying to achieve maximum distance upwind, the optimum angle of incidence is lower than that for the highest L/D. This yields a higher gliding speed. RC sailplane competitors and full-scale sailplane pilots adjust the elevator trim to achieve the optimum for each situation. That optimum differs depending on whether there is a headwind, tailwind, sink or lift The optimum depends on whether the goal is maximum duration, distance or speed.
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Old Feb 25, 2012, 01:48 PM
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Originally Posted by Lilienthal View Post
Zor, I don't want to get into the middle of your debate with kaptondave ...
There is debate as far as I am concerned. I am reporting facts based on personal experience with the decalage mod. Zor has no such experience, does not own the standard Radian for which the mod was designed, and therefore has no standing from which to debate facts.
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Old Feb 25, 2012, 03:01 PM
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United States, CA, Laguna Niguel
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FASST compatible OrangeRX in servo bay

Think I need to remove a little foam in front of the receiver to give the servo arms a bit of room to move. What might be a good attachment for a dremel to remove the foam in front of the receiver here. I already chipped out that one bit of foam so the receiver could lay flat, but would like to find a cleaner way to machine out the foam without it being chunky
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Old Feb 25, 2012, 03:40 PM
220 221 Whatever it takes
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USA, IL, Belleville
Joined Dec 2009
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Quote:
Originally Posted by g725s View Post
Think I need to remove a little foam in front of the receiver to give the servo arms a bit of room to move. What might be a good attachment for a dremel to remove the foam in front of the receiver here. I already chipped out that one bit of foam so the receiver could lay flat, but would like to find a cleaner way to machine out the foam without it being chunky
Why not use a small heated tip on a soldering iron to melt a small area? That's what I would do.

YMMV

LOL
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Old Feb 25, 2012, 04:19 PM
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United States, CA, Pleasanton
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Extended Wing Span Radians ?

Guys,

Who's been successful extending the WS of the Radian?

Given the eliptical wing planform I wondering if this is best done at the root or near the tip.

The mod itself looks pretty easy with some careful cutting and the installation of a sup-spar insure good load transfer at the point where the extension is made...

Thoughts, experiences and horror stories welcome

TIA.

:harry
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Old Feb 25, 2012, 04:24 PM
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Originally Posted by g725s View Post
Think I need to remove a little foam in front of the receiver to give the servo arms a bit of room to move. What might be a good attachment for a dremel to remove the foam in front of the receiver here.
A Dremel router bit does it for me. For larger areas a hot cutting tool which consists of a Xacto blade clamped in an electric soldering pencil works good.
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Old Feb 25, 2012, 04:52 PM
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I also use the Dremel "Router" bit, but first I cut the perimeter with an Exacto knife. This makes for a very clean cut. If you check my blog, you can see how I did this when I added spoilers to my Radian.
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Old Feb 25, 2012, 05:59 PM
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Riverside, Ca
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#60 grit sand paper and hemostats

Quote:
Originally Posted by g725s View Post
Think I need to remove a little foam in front of the receiver to give the servo arms a bit of room to move. What might be a good attachment for a dremel to remove the foam in front of the receiver here. I already chipped out that one bit of foam so the receiver could lay flat, but would like to find a cleaner way to machine out the foam without it being chunky
take a 1" wide strip of #60 sandpaper, fold it in half legthwise for strength and if you want put a thin piece of wood inside the fold,like a popcicle stick, and that will grind away or smooth out the foam. If more or different excavation is need, i use a a hemostat to pull one small chunk of foam out at a time



js
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Old Feb 25, 2012, 09:19 PM
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Thanks to everyone for the suggestions. I went down to the hardware store and picked up a router bit for my Dremel. Got home and could not find my Dremel case. So time to think of another option.

I was a bit hesitant to use a soldering iron on the foam. But it actually worked fantastic. Practically no smoke and super quick. As if the foam just magically disappears with the touch of the soldering iron. You just have to be careful not to get the iron close to any part you don't want to disappear. It's quick. I also thought it might gunk up the tip of the soldering iron but it was as if the foam just evaporated, no gunk.

Of course, for precise depth cutting like Lilienthal mentions above for his spoilers, the Dremel would be the option. But I just needed to rough out the foam so my RX would fit better.
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Old Feb 25, 2012, 10:17 PM
Zor
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Quote:
Originally Posted by williamson View Post
The first sentence is almost correct. The highest L/D ratio yields a glide that covers the maximum distance in still air. At a higher incidence angle, we get to the condition of minimum drag which yields the longest duration flights. At an even higher incidence angle, we reach stall. The horizontal tail feathers (stabilizer and elevator together) are adjusted to provide the desired incidence angle for any given situation.

When trying to achieve maximum distance upwind, the optimum angle of incidence is lower than that for the highest L/D. This yields a higher gliding speed. RC sailplane competitors and full-scale sailplane pilots adjust the elevator trim to achieve the optimum for each situation. That optimum differs depending on whether there is a headwind, tailwind, sink or lift The optimum depends on whether the goal is maximum duration, distance or speed.
Hi williamson,

Gliding for distance is done at the angle of attack for the highest lift to drag ratio.

Gliding for endurance is done at a slightly higher angle and lower speed than for distance because by reducing speed below that which gives the flattest glide we gain more by the lower airspeed than we lose by the speeper glide.

The full size pilot can make the adjustment since he has an airspeed indicator on his instrument panel.

The model plilot has no way of judging the small difference in nose attitude or judging accurately enough the airspeed of the model.

Zor
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Old Feb 25, 2012, 11:00 PM
Zor
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Originally Posted by kaptondave View Post
There is debate as far as I am concerned.
Debate or discussion or exchange of understandings; call it whatever you wish, that is fine and changes nothing.

Quote:
I am reporting facts based on personal experience with the decalage mod.
You are making statements of your personal experience or at least what you feel is happening but we do not see any explanation in terms of the logic of the physical and aerodynamic laws. You can have any feelings and that is fine but your feelings do not change the facts as they exist.

Quote:
Zor has no such experience,
Another example that you talk with feelings and not with facts.
Many readers and participants in the forum have knowledge of Zor's experience in aviation and also as a modeler. Radians do not fly by any different principles than any other airplanes.

Quote:
does not own the standard Radian for which the mod was designed,
That mod (modification) in terms of cutting a bit of the fin is needed only to make an adjustment to the stabilizer angle of incidence.
I would hardly refer to that as "a design"

Quote:
and therefore has no standing from which to debate facts.
Well Kaptondave . . . now that you have publickly disclosed your feelings about this case, this discussion and about Zor . . . I am glad that hopefully it made you feel better.

I restpectfully wish you some more knowledge and experience in the domains in which you are expressing your "feelings" even if you like to call them "facts".

With all due respect to you as a modeler friend . . .

de Zor
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Old Feb 25, 2012, 11:39 PM
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I don't wish to criticise any individual or this thread in general but it seems mildly amusing. I came into this thread just because purely for fun I purchased a basic Radian merely to compare it with my Easy Glider Pro. I got here to find extended, relatively heated, discussions on the aerodynamics of what appear to me to be a basic albeit very good flying electric sailplane.

I understand the desire to tinker with or modify the model because it is so cheap a total loss isn't the end of the world but it simply is what it is a good flying foamie. If it isn't can someone explain?
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Old Feb 26, 2012, 08:18 AM
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I understand you being perplexed David. Your assessment of the Radian is spot on. It is a basic yet good-flying machine as it comes out of the box. However it invites tinkering because the foam construction makes it easy to do and cheap to recover if a mistake is made. People are willing to do things with a Radian that they would never try with an expensive composite glider.

Are you familiar with the GWS Slow Stick? To me there is a parallel there. The Slow Stick has a huge following of tinkerers. There are more posts about it on rcgroups than on any other plane. The reason is the same. It is simple, cheap and easy to modify. The same goes for other models including the Multiplex Easy Star.

On the Radian there are two types of popular mods - those intended to improve durability and those intended to improve performance. Both enhance the enjoyment, and that is why we do them.

It may be that there are one or more individuals who take aerodynamic theory over the top a bit but that is their form of enjoyment, and we can live with that.
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Old Feb 26, 2012, 11:09 AM
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Quote:
Originally Posted by Zor View Post
The full size pilot can make the adjustment since he has an airspeed indicator on his instrument panel.

The model plilot has no way of judging the small difference in nose attitude or judging accurately enough the airspeed of the model.
Competition RC sailplane pilots make frequent elevator adjustments for differing conditions. Indeed, the RC pilot can't see small differences in nose attitude, but he has some sense of airspeed just looking at the plane. Skilled pilots have a keen sense of when a plane is in lift or sink. Coming home with a head wind is a challenge. To cope with all of these conditions, the pilot makes changes in elevator trim. RC competition sailplanes end up being flown much like their full-scale counterparts despite not having the full range of cockpit sensors available in a full-scale sailplane. With recent advances in on-board instrumentation (e.g., speed, altitude, variometer..) and down links for RC sailplanes, pilots can now fly these like the full-scale sailplanes.
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Old Feb 26, 2012, 11:38 AM
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Originally Posted by kaptondave View Post
A more important question is why make the mod? If you have not already done so you should read this.

http://glidefast.typepad.com/glidefa...-ups.html#more
I have read all this and think the mod makes sense. It is interesting to me though as to why the plane was designed as it comes. The advatages to the designers didn't come out in the discussion.
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