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Old Sep 26, 2008, 08:19 AM
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United States, IL, Champaign
Joined Sep 2005
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Yes, absolutely. In short, thermals are created when cool ground is warmed during the day. The sun heating pavement during the day can cause thermals, heat generated by buildings can cause thermals, etc.

http://en.wikipedia.org/wiki/Thermal_column
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Old Sep 26, 2008, 06:39 PM
It works, don't touch it.
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Joined Dec 2007
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Quote:
Originally Posted by ram008
Yes, absolutely. In short, thermals are created when cool ground is warmed during the day. The sun heating pavement during the day can cause thermals, heat generated by buildings can cause thermals, etc.

http://en.wikipedia.org/wiki/Thermal_column
Ah thanks. Sorry to be off topic but one more question. On humid days, do planes have a harder time flying/getting lift? It seems that when i feel all hot and sticky, you know those horrible days that are very hot and humid, my planes wont fly as high. It feels like they are underpowered somewhat. Humidity is water in the air so it probably weighs down the plane then?
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Old Sep 26, 2008, 11:39 PM
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United States, IL, Champaign
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From a USA Today article on air density and humidity:

Quote:
Aircraft pilots don't do as well as baseball players when the air's density decreases. Lower air density penalizes pilots in three ways: The lifting force on an airplane's wings or helicopter's rotor decreases, the power produced by the engine decreases, and the thrust of a propeller, rotor or jet engine decreases. These performance losses more than offset the reduced drag on the aircraft in less dense air.

Pilots use charts or calculators to find out how temperature and air pressure at a particular time and place will affect the air's density and therefore aircraft performance. In general, these calculations don't take humidity into account since its affects are so much less than the others. When the air's density is low, airplanes need longer runways to take off and land and they don't climb as quickly as when the air's density is high.
Humid air is less dense than dry air. Hope this helps!
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Old Sep 27, 2008, 06:05 AM
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USA, CA, Mountain View
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Please explain why humid air is less dense than dry air.

Humid air would have more water molecules in it - making it more dense.
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Old Sep 27, 2008, 08:41 AM
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United States, CA, Mojave
Joined Jan 2003
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Quote:
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.
The density we're referring to here the ratio of air molecules to total molecules in the volume being measured. I believe the effect is that the water molecules don't behave quite the same as the air molecules, changing the viscous effects and kinetic behavior of the atmosphere. This may not be rigorously technically correct, and I'll defer to someone with more knowledge than I...

I've always thought that humidity's effect on density altitude had more to do with power production from IC engines, where the higher ratio of water molecules and lower ratio of air molecules in a given volume reduce the amount of combustible air available to the engine and thus reduce the power output.
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Old Oct 06, 2008, 02:38 AM
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Joined Jul 2008
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Quote:
Originally Posted by Dave Eichstedt
The Radian does require a much larger flying area, however! For a beginner, think about an open area at least the size of a football field, preferrably two. It has an amazing L/D (glide ratio), especially if you're not used to flying sailplanes. It takes a little practice to master the energy management to make a spot landing. The good thing is that with rudder/elevator sailplanes, it's very relaxing. Things don't happen too fast, and they're usually fairly smooth.

David
David,

Why no ailerons?

Will they offer a aileron version soon at the same price?

With no ailerons, there seems no incentive to upgrade, from a 55" wing 3 ch. Harbor Freight Wild Hawk, on sale every few months for $65 RTF with tx, rx, everything.

If Radian had ailerons, and was still under 2 lbs. to qualify for the AMA park $28 lower cost membership, And under $200 with free shipping, I would buy it.

If no ailerons, I can continue with the already owned 3 ch 55" Wild Hawk, a great low cost glider when trimmed well, upgradeable to brushless & lipo for $40 to $90.

No ailerons on Radian gives big incentive to pass, until an aileron version arrives.

Its a shame. Radian has a nice over 76" wing, under 2 lbs to qualify for the lower priced AMA park membership, and new 2.4 ghz tx & rx.

Why didn't Parkzone finish Radian, and add ailerons, ... like other 77" wing planes, such as the 'on sale' under $200 with free shipping 4ch ailerons Grand Distributions Icon Hawk glider.

You may want to suggest Parkzone offer both aileron and non-aileron versions, at the same price, and see which one wins more orders. I would guess a 5 to 1, or greater, interest in the 4 ch aileron version.

If Radian had 4 ch ailerons, my pre-order might be in now, at $250 with free shipping that redrockeyhobbies is offering for the non-aileron version.

If Radian with ailerons was under $200, under 2 lbs., with free shipping, like the current on sale under $200 77" 4 ch. aileron-brushless-1800mah/lipo-foam Icon Hawk offering, my order would definitely be in.

Summary:

David,

1) why did Parkzone leave ailerons off the otherwise interesting Radian?

2) when may an under 2 lb. aileron Radian version be available?
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Old Oct 06, 2008, 09:09 AM
WAA-08 THANK FRANK!
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Las Cruces, New Mexico, United States
Joined Jun 2002
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Mr_Crash - if the Radian is not right for you - then move on and get over yourself! Why in the world do you think that HH and Parkzone needs to meet YOUR needs? If you want, why don't YOU develope the perfect model and make a million dollars off of it?
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Old Oct 06, 2008, 09:41 AM
Garry Owen!
Florida
Joined Oct 2004
341 Posts
I have the EasyGlider Electric with brushless motor...I like it but it flies too fast to land in my backyard (100X100) I consider myself an expert pilot after flying for over 30 years but even with spoilerons deployed and clearing my 6 foot privacy fence, my EGE touches down and slides into my fence on the other side of the yard. What I need is a floater that will land slooow and slide only a few feet before stopping. In a sailplane ailerons are not that important so it doesn't bother me in the least that it doesn't have them...Actually it's nice to have the simplest airplane there is when you are flying in your backyard after supper. I hope the Radian is capable of floating into my feet or even slow enough for a hand catch...that would be terrific!
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Old Oct 06, 2008, 09:46 AM
WAA-08 THANK FRANK!
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Las Cruces, New Mexico, United States
Joined Jun 2002
7,178 Posts
YAK - there is a new motor glider that is about to hit the market. The helium from www.stevensaero.com will be a 2m T/R/E/S glider. It is a laser cut kit - but don't let that put you off. The kits from Stevensaero go together really easy and are a pleasure to build. There is a thread on it in the parkflier forum.

ETA - soon
How soon? I don't know.

JimNM
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Old Oct 06, 2008, 09:53 AM
Garry Owen!
Florida
Joined Oct 2004
341 Posts
Quote:
Originally Posted by JimNM
YAK - there is a new motor glider that is about to hit the market. The helium from www.stevensaero.com will be a 2m T/R/E/S glider. It is a laser cut kit - but don't let that put you off. The kits from Stevensaero go together really easy and are a pleasure to build. There is a thread on it in the parkflier forum.

ETA - soon
How soon? I don't know.

JimNM
Thanks for the heads up Jim...I'll be looking for it! I love laser cut kits!
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Old Oct 07, 2008, 09:09 AM
dmt
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near Gangneung, Korea
Joined Jul 2004
688 Posts
It's a bit strange for me to see people ragging on the Radian for not having ailerons -- because, the fact that it doesn't have ailerons is its primary attraction for me! RE is the classic recreational glider setup -- think 'Gentle Lady'.

If you want ailerons, there are a ton of models out there. In the electric-powered foamie category, there is, for one, the very popular Easy Glider Electric.

For thermal soaring, ailerons actually aren't particularly useful. A properly designed sailplane with a polyhedral wing will pretty much automatically coordinate your turns for you [with the pilot only using rudder]. Aside from that non-use (coordinating turns, that is), there's not much to do with ailerons on a sailplane besides fine-tuning the wing camber and making final approaches (particularly when deflected up as spoilerons) and spot landings. Actually, that is quite a bit, isn't it?! That's of course why many people fly "full house" [REAF] gliders. With non-electric gliders, slightly drooping the ailerons can give extra height on a hi-start launch. This kind of wing camber can also be useful thermalling. When traversing an area of sink, ailerons might be used to put the wing in a different camber so you can get through the sink faster. Okay, so there's a lot you can do with ailerons! However, this is really very much 'fine-tuning' sort of stuff.

If you're really into the performance of your sailplane like that, you'll want to invest in the appropriate [full house] aircraft and radio. The Cularis [and an appropriate seven channel-or-so radio] might be a good way to get yourself started in this area.

Also, ailerons can be used to amuse yourself with aerobatics on the way down. Nothing wrong with that.

If you're slope soaring, ailerons-enabled aerobatics might be the main purpose of your flight. With the aircraft pretty much right there in front of you [when sloping], ailerons definitely make things more interesting. Or, you can just motor around your field with the motor on and use your electric-powered sailplane as an airplane. If those kinds of flying sound like what you want, then the Easy Glider Electric is probably the way to go. The Easy Glider isn't a dedicated sloper, nor is it a dedicated thermaler. It's more of an all-arounder. It can be used to thermal, and it can be used to slope, both with good results. In the electric version, it can be flown around as a park flier airplane too.

BUT, the basic idea of a thermal sailplane is that you go up a few hundred feet (which in our case is more than solved by the electric motor, which you then turn off) and glide around [in a pattern] searching for lift. This gliding is done basically in a straight shallow descent, and then eventually with a shallow-to-medium bank turn to enter a new leg of the pattern. When your aircraft indicates lift, you [attempt to] turn into it and go up! You then continue turning (in circles), attempting to keep your turns centered in the rising (and expanding) bubble of air (that is, the thermal). If you're skillful and/or lucky, you can ride the thermal all the way up until the aircraft is becoming in danger of disappearing from your sight. Either when you lose the thermal or are forced to abandon it (because of going to high or too far downwind), you enter a level glide (probably after turning back toward your field, if you've gotten far away) and resume a search pattern for another thermal. The point is, thermalling generally involves long minutes staring up (with your neck craned backwards) at a small shape in the sky that you control to turn circles. With appropriate dihedral, ailerons aren't important for this. In fact, if you have a flat wing and ailerons, it's a lot of work to keep the plane level and coordinated when it is so far away (which is hopefully most of the time). Remember -- hopefully it's way up there and you can barely see the thing!

I have and enjoy an Easy Glider Electric (actually two of them, plus a third non-electric Easy Glider), but what I'm looking for now is more of a dedicated thermaler. Basically, I'm looking for a[n electric-powered] foamie version of my Sophisticated Lady. Or you could say, a more dedicated glider version of my Easy Star. Something that's inherently stable -- an RE ship. Something where I can just concentrate on the hunt for thermals and staying within them, while the plane meanwhile basically flies itself. I want something relaxing, where I also don't have to worry about all sorts of complicated mixes on the radio. It's looking to me like the Radian is the plane for me!

Sorry for the long post, but I just wanted to explain why a lot of people are going to think the Radian is a cool ship. Parkzone didn't "drop the ball" by "leaving out" ailerons, but rather RE for Thermalling is a legitimate, established sailplane category. It's a category especially suited for beginners or those who want to have very relaxing flights -- which is the category of pilot that the Radian is aimed at. If you're looking for a glider with ailerons (which is also a very legitimate category!), simply look for a different aircraft. Maybe Parkzone will eventually put out a model in that category too. But the rudder -elevator Radian is in a different category, one that many pilots will enjoy.
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Old Oct 07, 2008, 09:29 AM
dmt
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near Gangneung, Korea
Joined Jul 2004
688 Posts
A competition category of sailplanes that seems to be enjoying a revival is RES (that is, Rudder, Elevator, Spoilers). Spoilers are nice for escaping a boomer (a really powerful thermal) or for increasing your descent rate and angle when making a landing approach over obstacles, and to help you get a floater onto the ground in smaller landing areas.

For me, that's the one thing I wish the Radian had -- spoilers. I guess we all have our own wish list, don't we?!! Anyway, after I get mine, that's the first mod that I'll be looking into. The flex-y wing could make that tricky though...

Of course one can always get the prop windmilling to increase drag, but spoilers are more fun and, well, "sailplane-y" somehow (at least for me). Deployed on a slider, they're more controllable too.
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Old Oct 07, 2008, 09:32 AM
Slope convert/addict
DelUK's Avatar
Romford, Essex. UK
Joined Mar 2006
208 Posts
Quote:
Originally Posted by dmt
It's a bit strange for me to see people ragging on the Radian for not having ailerons -- because, the fact that it doesn't have ailerons is its primary attraction for me! RE is the classic recreational glider setup -- think 'Gentle Lady'.

If you want ailerons, there are a ton of models out there. In the electric-powered foamie category, there is, for one, the very popular Easy Glider Electric.

For thermal soaring, ailerons actually aren't particularly useful. A properly designed sailplane with a polyhedral wing will pretty much automatically coordinate your turns for you [with the pilot only using rudder]. Aside from that non-use (coordinating turns, that is), there's not much to do with ailerons on a sailplane besides fine-tuning the wing camber and making final approaches (particularly when deflected up as spoilerons) and spot landings. Actually, that is quite a bit, isn't it?! That's of course why many people fly "full house" [REAF] gliders. With non-electric gliders, slightly drooping the ailerons can give extra height on a hi-start launch. This kind of wing chamber can also be useful thermalling. When traversing an area of sink, ailerons might be put in a different camber to get through the sink faster. Okay, so there's a lot you can do with ailerons! However, this is really very much 'fine-tuning' sort of stuff.

If you're really into the performance of your sailplane, you'll want to invest in the appropriate [full house] aircraft and radio. The Cularis might be a good way to get started with that.

Also, ailerons can be used to amuse yourself with aerobatics on the way down. Or you can just motor around with the motor on and use it as an airplane. If that sounds good to you, then the Easy Glider Electric is probably the way to go.

BUT, the basic idea of a thermal sailplane is that you go up a few hundred feet (which in our case is more than solved by the electric motor), and then you glide around [in a pattern] searching for lift. This gliding is done basically in a straight shallow descent, and then eventually with a shallow to medium bank turn to enter a new leg of the pattern. When your aircraft indicates lift, you [attempt to] turn into it and go up! You then continue turning (in circles), attempting to keep your turns centered in the rising (and expanding) bubble of air (that is, the thermal). If you're skillful and/or lucky, you can ride the thermal all the way up until the aircraft is becoming in danger of disappearing from your sight. Either when you lose the thermal or are forced to abandon it (because of going to high or too far downwind), you enter a level glide (probably after turning back toward your field, if you've gotten far away) and resume a search pattern for another thermal. The point is, thermalling generally involves long minutes staring up (with your neck craned backwards) at a small shape in the sky that you control to turn circles. Ailerons aren't important for this. In fact, if you have a flat wing and ailerons, it's a lot of work to keep the plane level and coordinated when it is so far away (which is hopefully most of the time). Remember -- hopefully its way up there and you can barely see the thing!

For sloping though, where the aircraft is right there in front of you, ailerons definitely make things more interesting. The Easy Glider isn't a dedicated sloper, nor is it a dedicated thermaler. It's more of an all-arounder. It can be used to thermal, and it can be used to slope, both with good results. In the electric version can be flown around as a park flier airplane

I have and enjoy an easy glider electric (actually two of them, plus a third nonelectric easy glider), but what looking for now is more of a dedicated thermaler. Basically, I'm looking for a[n electric-powered] foamie version of my Sophisticated Lady. Or you could say, a more dedicated glider version of my Easy Star. Something that's inherently stable -- an RE ship. Something where I can just concentrate on the hunt for thermals and staying within them, while the plane meanwhile basically flies itself. I want something relaxing, where I also don't have to worry about all sorts of complicated mixes on the radio. It's looking to me like the Radian is the plane for me!

Sorry for the long post, but I just wanted to explain why a lot of people are going to think the Radian is a cool ship. Parkzone didn't "drop the ball" by "leaving out" ailerons, but rather RE is an established sailplane category. It's a category especially suited for beginners or those who want to have very relaxing flights -- which is the category of pilot that the Radian is aimed at. If you're looking for a glider with ailerons (which is a very legitimate category!), simply look for a different aircraft. Maybe Parkzone will eventually put out a model in that category too. But the rudder -elevator Radian is in a different category, one that many pilots will enjoy.
whoaa, long post! But you are totally spot on. Parkzone have probably got a winner on their hands in my opinion, appealing to both beginners and those looking for an efficient lazy thermalling floater. I wish it had come out earlier to be honest.
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Old Oct 07, 2008, 09:48 AM
dmt
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near Gangneung, Korea
Joined Jul 2004
688 Posts
Quote:
Originally Posted by DelUK
whoaa, long post! But you are totally spot on.
I guess I kind of have some time on my hands these days!


Quote:
I wish it had come out earlier to be honest.
Me Too! 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...
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Old Oct 07, 2008, 10:16 AM
Bazinga!
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South Africa, KZN, Durban
Joined Feb 2007
614 Posts
I saw the Radian in action today... very impressive! It climbs vertically with no problem, glides really slow, turns on a dime, and is an overall good performer. It looks and feels very strong and light. I'm definitely getting one!
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