Parkzone radian - New 2m Span RTF Glider. - Page 5 - RC Groups
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Oct 07, 2008, 08:40 PM
Up Up and Away!
lightspeeddud's Avatar
where ya see it? Im still deciding if I want this plane for the parkzone corsair.
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Oct 07, 2008, 08:50 PM
It works, don't touch it.
skiesthelimit's Avatar
I wish that it came out earlier like in the summer or spring instead of fall/winter. Its getting cold now, but i bet that wont stop me from thermaling.
Oct 08, 2008, 01:08 AM
Moelich73's Avatar
Originally Posted by lightspeeddud
where ya see it? Im still deciding if I want this plane for the parkzone corsair.
A friend's got a demo model which we flew after work.
Oct 08, 2008, 12:31 PM
Registered User
does anyone know what kind of range does the out of the box RTF rx/tx combo has (AR500)?

here's my predicament...I figure if i need to get a new rx and battery I may as well just get the RTF version for $90 bucks more...i'd really like to fly it high w/o fear of loosing reception. so...i have the dx7 with an AR6100 (which i wouldn't use for this).

Any recommendations??:
1) get a full range rx (e.g. AR6200), and a new battery (there's 90$ there) and use existing dx7
2) go for the RTF version
Oct 08, 2008, 12:52 PM
Moelich73's Avatar
The specs on the Parkzone site says "Spektrum 2.4GHz DX5e with AR500 full-range receiver (included)" and by full-range I understand it to be the same or close to the range of other "regular" radio setups. Someone said it should give you at least a mile, which should be far enough!
Oct 08, 2008, 01:05 PM
Registered User
cool, thanks Bestview. i saw that note as well and i would agree with you that full range means full range across the board.

in any event this looks like a neat plane. look forward getting my hands on one and to some relaxing flights ahead
Oct 10, 2008, 01:59 AM
Registered User
Originally Posted by dmt
This is, at least spec-wise, exactly the type of aircraft I wanted to start out on. Instead, I went through a bit of a frustrating progression. Thank God I finally found the Easy Star, which finally got me rolling. Oh well, now I'll just work backwards and get the kind of plane I had wanted all along. Not the most direct journey, but as long as I get to my destination...

Your Easy Star, is like my two RTF Harbor Freight 3-ch 55" Wild Hawks. My first rc buy was a new $65 WH last July 2008, and bought a 2nd used $16 WH a month later. Both operating, and enjoying flying both, ... one with faster flying lighter 6 cell ni-ca battery packs, the other with a longer flying 7 cell ni-mh pack.

So, I'm still new to rc, and found I enjoy the beauty of glide fight, when its so high it's barely visible, or on landing approach, or anywhere in between.

Thanks for your discussion of "with and without" the ailerons. I have not yet had ailerons, and thought, maybe, it would be an interesting new addition to my next rc experience and plane.

If you were at my stage, never having ailerons, new to rc for 3 months, and all your experience had been only with your 3-ch Easy Star, (like me with the 3-ch 55" Wild Hawk), ...

knowing what you know, about the "Easy Glider" with ailerons, but pretending you had not yet experienced the Easy Glider and ailerons yet,

and knowing what you know so far, about the Radian,

would you tend to go next for the Easy Glider with ailerons (having not yet experienced ailerons, like me, now),

or the Radian without ailerons?

Second, could you compare, the $249 brushless/lipo 3-ch Radian, with an on sale $192 free ship 4-ch with ailerons bushless/lipo Grand Distribution Icon Hawk, ... as if you had never yet experienced ailerons, like me, but knowing what you do know now, about planes with ailerons like your Easy Glider, ... and without ailerons, such as the Radian.

On a final note, my Wild Hawks fly so well, at the smaller of the two fields I fly, its sometimes hard to land without running out of runway, and nearly hitting trees at either end and sides. So, at the smaller field, maybe flaps, or spoilers, or ailerons in a flap position, could slow it down some for landings?

Last edited by Mr_Cash; Oct 10, 2008 at 02:46 AM.
Oct 10, 2008, 06:30 AM
Registered User
dmt's Avatar
Mr Cash, hi!

When I first developed an interest in flying RC, I really, really wanted ailerons. As a long time "full scale" pilot, the idea of flying without ailerons just seemed terribly wrong to me. I thought that without ailerons, it wasn't "really" flying.

Learning to fly RC though, I had to learn to disregard a lot of my "full-scale" knowledge and skills. Flying RC is really quite a bit different. Basically, once I found success with the Easy Star, I became much more comfortable with rudder-elevator.

BUT, I still wanted to experience ailerons. Also, having flown "full-scale" sailplanes a little bit, I felt spoilers were very important to the sailplane experience. So, I was really interested in the easy Glider Electric.

But (another but!), the whole reason I got into RC was to fly sailplanes like I'd first seen some of my friends do a number of years ago. They were flying unpowered Rudder-Elevator balsa kit gliders in thermals -- I thought it was one of the most magnificent things I had ever seen, with the three sailplanes dancing together in the rising morning air! Launching is a problem for me though in terms of practicality, so I knew I'd have to go powered. I also learned the hard way that I don't enjoy building and/or repairing balsa kits. I'm a "foamie" guy, it seems.

So, the answer is I would have gotten the Radian first, because that kind of RC flying was my first and strongest dream. But I would have eventually gotten an Easy Glider too (or even a Cularis, which I had the major hots for for a while, though that has faded), to satisfy my aileron jones. I was just too curious about and infatuated by full control to have never gotten an aileron ship.

Basically, I would have gotten both; though in reverse order (the Radian first), if the Radian had been available a year or two ago.
Oct 10, 2008, 10:38 AM
Registered User
dmt's Avatar
Originally Posted by Mr_Cash

On a final note, my Wild Hawks fly so well, at the smaller of the two fields I fly, its sometimes hard to land without running out of runway, and nearly hitting trees at either end and sides. So, at the smaller field, maybe flaps, or spoilers, or ailerons in a flap position, could slow it down some for landings?

Flaps increase lift and (especially if deployed far enough) increase drag. That means that you can fly a slower approach without stalling, as well as come in at a steeper angle (without speeding up). This helps with clearing obstacles on the landing approach, as well as giving lower touchdown speeds and shorter after landing rolls (not exactly critical on an aircraft with no wheels!).

Spoilers (and spoilerons) decrease lift (and also increase drag to an extent). The aircraft flies at the same airspeed, but descends at a steeper angle. This can be useful for clearing obstacles at the edge of a field, and then still getting down onto the field. For example, say there's a line of trees before your landing field. You have to stay high to stay above the trees, but then that leaves you very high above your field and in danger of overshooting your landing area. Of course you could dive it down after you get over the trees, but then you would speed up and float forever and then again possibly overshoot the landing area! With spoilers on the other hand, you come in with enough height to clear the trees, then deploy the spoilers so the wings will produce less lift, sending the aircraft descending at a steeper angle while still trimmed for the same airspeed (you don't speed up). So, after getting over the trees it descends nice and steep and then touches down without floating. If you have your spoilers on a slider (on your transmitter, if your transmitter allows that), you can vary the amount they are deployed to use them just as much as needed, or to shallow out or steepen your descent angle (that is, make adjustments to your glide path).

With a computer radio, you can (probably, depending on the exact radio and other elements of your setup) program your ailerons to either both drop together like flaps, or both go up together like spoilers. Either and/or both of them can be useful for getting into a short field or getting over obstacles on approach.

If you don't have spoilers or flaps, a windmilling propeller can increase drag and help you descend a bit steeper without speeding up. Windmilling means that the prop is turning, but not producing power (in other words, put in the minimum throttle setting to just get the prop spinning). Of course, just a little bit too much throttle and any thrust the motor produces will serve to either speed you up or decrease your descent angle, so it can be a fine line.

The other thing you can do is come in on the "backside of the power curve". This has nothing to do with any device like propellers or flaps or spoilers, but rather flying technique. If you get the plane really slow (getting down near stall speed) it's flying in a high drag situation and it actually takes more power to fly this slow [and hold altitude] than it does to fly at a medium-slow speed [and hold altitude]. So, you fly it that slow (and thus high drag) but don't give it so much throttle, and you'll descend. You keep the nose up so hold your desired airspeed, and add or reduce throttle to decrease or increase your descent rate as needed. The basic idea is that a very slow approach can get the aircraft descending steeply without speeding up.

[If it's windy or gusty, you can't fly that slowly without stalling, so you'd have to throw in a bit more airspeed as needed. Calm or low winds are the best for applying this technique. Then again, if you're landing into a strong headwind, you should have no problem at all making your field! As always, practice something like this "three mistakes high" before trying it close to the ground]
Oct 10, 2008, 10:52 AM
Registered User
dmt's Avatar
Wow, that Icon looks exactly like the easy glider!

So, which should you get? I'd say get the one that most attracts you. I'd also say that you probably shouldn't expect any one plane to be your final perfect design though (although there's always the possibility!). There's probably going to be a process (might take a few years) of trying a few different things out and seeing what you like. You might end up wanting to keep a few different models on hand. Obviously that can get expensive [especially when you choose the wrong model -- it sure sucks to make expensive mistakes!]. But you don't have to do it all at once -- and you already know you enjoy the Wild Hawk. You can keep coming back to it.

But anyway, get the one that most attracts you, the one that's going to get you jazzed to go flying. If the main thing you want to do next is explore ailerons, get some kind of aircraft with ailerons. If the main thing you wanted to is explore thermalling, well ailerons can certainly be a part of that, but ailerons do make it a bit more complicated (and expensive) than just learning to thermal with an RE ship. But either way will be fine. An aileron-equipped glider like the Easy Glider Electric (or, I'm sure, the Icon) is fine for learning to catch thermals.
Oct 10, 2008, 04:04 PM
AndyTheLegend's Avatar
I definitely agree that ailerons aren't needed on a sailplane. I've seen many people learn to fly/thermal without them. I'm not sure though whether or not to just buy the RTF or PNP.... I already have the DX7 , yet to buy the $60 AR500 and 1 or 2 1320 3S from is probably over $250... What's everyone else doing?
Oct 10, 2008, 04:39 PM
Home of A-10 - Farmingdale NY
boiko's Avatar

Could Wing Flutter ever become an issue on the Radian..?

Now I fully realize that the Radian is neither a Hotliner, nor a Warmliner.

But since the foam Multiplex Blizzard has been experiencing significant wing flutter on rapid decent/dives...I just thought I would ask...

Is it safe to say that flutter should never be an issue with the Radian...even in high altitude dives. So far there are no video's showing any type of altitude dives. What would happen if you tried it....nothing..something.

Just curious...

Oct 10, 2008, 06:58 PM
Registered User
Dr Kiwi's Avatar
Originally Posted by 7rider
Please explain why humid air is less dense than dry air.

Humid air would have more water molecules in it - making it more dense.
Density of air
From Wikipedia, the free encyclopedia
(Redirected from Air density)
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The density of air, ρ (Greek: rho) (air density), is the mass per unit volume of Earth's atmosphere, and is a useful value in aeronautics. Air density decreases with increasing altitude, as does air pressure. At sea level and at 20 C, air has a density of approximately 1.2 kg/m3.

The density of water, which is about 1000 kg/m3 (1 g/cm), is about 800 times more than the density of air at sea level.

* 1 Effects of temperature and pressure
* 2 Effect of water vapor
* 3 Effects of altitude
* 4 Importance of temperature
* 5 See also
* 6 References
* 7 External links

[edit] Effects of temperature and pressure

The formula for the density of dry air is given by:

\rho = \frac{p}{R \cdot T}

where ρ is the air density in kilograms per cubic meter, p is pressure in pascals, R is the specific gas constant, and T is temperature in kelvins.

The specific gas constant for dry air is:

R_\mathrm{dry\,air} = 287.05 \frac{\mbox{J}}{\mbox{kg} \cdot \mbox{K}}


* At IUPAC standard temperature and pressure (0 C and 100 kPa), dry air has a density of 1.2754 kg/m3.
* At 20 C and 101.325 kPa, dry air has a density of 1.2041 kg/m3.
* At 70 F and 14.696 psia, dry air has a density of 0.074887 lbm/ft3.

[edit] Effect of water vapor

The addition of water vapor to air (making the air humid) reduces the density of the air, which may at first appear contrary to logic.

This occurs because the molecular mass of water (18) is less than the molecular mass of air (around 29). For any gas, at a given temperature and pressure, the number of molecules present is constant for a particular volume. So when water molecules (vapor) are introduced to the air, the number of air molecules must reduce by the same number in a given volume, without the pressure or temperature increasing. Hence the mass per unit volume of the gas (its density) decreases.

The density of humid air may be calculated as a mixture of ideal gases. In this case, the partial pressure of water vapor is known as the vapor pressure. Using this method, error in the density calculation is less than 0.2% in the range of −10 C to 50 C. The density of humid air is found by:

\rho~_{_{humid~air}} = \frac{p_{d}}{R_{d} \cdot T} + \frac{p_{v}}{R_{v} \cdot T} [1]


\rho~_{_{humid~air}} = Density of the humid air (kg/m)
pd = Partial pressure of dry air (Pa)
Rd = Specific gas constant for dry air, 287.05 J/(kgK)
T = Temperature (K)
pv = Pressure of water vapor (Pa)
Rv = Specific gas constant for water vapor, 461.495 J/(kgK)

The vapor pressure of water may be calculated from the saturation vapor pressure and relative humidity. It is found by:

p_{v} = \phi~ \cdot p_{sat}


pv = Vapor pressure of water
\phi~ = Relative humidity
psat = Saturation vapor pressure

The saturation vapor pressure of water at any given temperature is the vapor pressure when relative humidity is 100%. A simplification of the regression [1] used to find this, can be formulated as:

p(mb)_{sat} = 6.1078 \cdot 10^{\frac{7.5 \cdot T-2048.625}{T-35.85}}


* This will give a result in mb (millibar), 1 mb=100 Pa

* pd is found considering partial pressure, resulting in:

pd = p − pv

Where p simply notes the absolute pressure in the observed system.

[edit] Effects of altitude

To calculate the density of air as a function of altitude, one requires additional parameters. They are listed below, along with their values according to the International Standard Atmosphere, using the universal gas constant instead of the specific one:

* sea level standard atmospheric pressure p0 = 101325 Pa
* sea level standard temperature T0 = 288.15 K
* Earth-surface gravitational acceleration g = 9.80665 m/s2.
* temperature lapse rate L = −.0065 K/m
* universal gas constant R = 8.31447 J/(molK)
* molar mass of dry air M = 0.0289644 kg/mol

Temperature at altitude h meters above sea level is given by the following formula (only valid inside the troposphere):

T = T_0 + L \cdot h

The pressure at altitude h is given by:

p = p_0 \cdot \left(1 + \frac{L \cdot h}{T_0} \right)^\frac{g \cdot M}{-R \cdot L}

Density can then be calculated according to a molar form of the original formula:

\rho = \frac{p \cdot M}{R \cdot T}

[edit] Importance of temperature

The below table demonstrates that the properties of air change significantly with temperature.

Table speed of sound in air c, density of air ρ, acoustic impedance Z vs. temperature C
Effect of temperature
C c in m/s ρ in kg/m Z in Pas/m
−10 325.2 1.342 436.1
−5 328.3 1.317 432.0
0 331.3 1.292 428.4
+5 334.3 1.269 424.3
+10 337.3 1.247 420.6
+15 340.3 1.225 416.8
+20 343.2 1.204 413.2
+25 346.1 1.184 409.8
+30 349.0 1.165 406.3
Oct 10, 2008, 07:18 PM
Registered User
7rider's Avatar
Dear Dr. Kiwi,

Thank you for blowing my mind on a Friday afternoon

This is where my intuition was wrong:

Wait a minute, you might say, "I know water's heavier than air." True, liquid water is heavier, or more dense, than air. But, the water that makes the air humid isn't liquid. It's water vapor, which is a gas that is lighter than nitrogen or oxygen.

Every so often, I'll demonstrate the Bernoulli effect to the kids with two strips of paper. It still seems pretty amazing to me.
Last edited by 7rider; Oct 10, 2008 at 07:38 PM.
Oct 11, 2008, 05:41 AM
Got shenpa?
flieslikeabeagle's Avatar
Originally Posted by dmt
They were flying unpowered Rudder-Elevator balsa kit gliders in thermals -- I thought it was one of the most magnificent things I had ever seen, with the three sailplanes dancing together in the rising morning air! Launching is a problem for me though in terms of practicality, so I knew I'd have to go powered.
Have you considered the E-Flite Ascent? (The original red one, not the much heavier new blue PNP version).

Yes, it's balsa and fibreglass, but the thing is a floater and extremely unlikely to need repairing unless you practice landing nose-first into a concrete wall.

I know as much about thermal soaring as a politician knows about honesty, so I won't pretend to tell you how good the Ascent is at soaring - but on the now very long Ascent thread, many experienced glider pilots will be happy to tell you so.

With a lightweight brushless motor to replace the boat-anchor brushed Speed 400, two small servos, a lightweight Rx, and a small lipo pack, you can build the Ascent really light - under 16 oz, at which point the wing loading drops under 7 oz/ sq ft. Charles (Everydayflier) describes one such setup:

Today you could have similar performance for much less money using a cheaper motor, ESC, and lipo pack.