Sep 26, 2008, 08:19 AM Registered User United States, IL, Champaign Joined Sep 2005 126 Posts 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
Sep 26, 2008, 06:39 PM
It works, don't touch it.
Joined Dec 2007
2,935 Posts
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?
Sep 26, 2008, 11:39 PM
Registered User
United States, IL, Champaign
Joined Sep 2005
126 Posts
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!
 Sep 27, 2008, 06:05 AM Registered User USA, CA, Mountain View Joined Dec 2007 933 Posts Please explain why humid air is less dense than dry air. Humid air would have more water molecules in it - making it more dense.
Sep 27, 2008, 08:41 AM
AMA 562227
United States, CA, Bear Valley Springs
Joined Jan 2003
638 Posts
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.
Oct 06, 2008, 02:38 AM
Registered User
Joined Jul 2008
92 Posts
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?
Last edited by Mr_Cash; Oct 26, 2008 at 02:01 AM.
 Oct 06, 2008, 09:09 AM WAA-08 THANK FRANK! Las Cruces, New Mexico, United States Joined Jun 2002 8,563 Posts 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?
 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! Last edited by Yak18; Oct 06, 2008 at 09:50 AM.
 Oct 06, 2008, 09:46 AM WAA-08 THANK FRANK! Las Cruces, New Mexico, United States Joined Jun 2002 8,563 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
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!
 Oct 07, 2008, 09:29 AM Registered User 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. Last edited by dmt; Oct 07, 2008 at 10:44 AM.
Oct 07, 2008, 09:32 AM
Romford, Essex. UK
Joined Mar 2006
208 Posts
Quote:
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.
Oct 07, 2008, 09:48 AM
Registered User
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...
 Oct 07, 2008, 10:16 AM Bazinga! South Africa, KZN, Durban Joined Feb 2007 625 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!