I agree, a 20 ft spanning motorglider would probably perform very well for an R/C model. You might be able to win numerous R/C model contests with it. Or you could have it piloted by a small Chihuahua or Rhesus Monkey, and it would achieve very good soaring performance.
I have actually once flown a 20 ft spanning motorglider myself, it was designed by the same aircraft engineer who designed the aircraft in the photos above. It had an unusual feature for motorgliding... after climb to gliding altitude, the propeller spinner departs from its mounting and strikes the propeller. This feature causes a very effective warning alarm, which reminds the pilot to shut down the self-launch engine. This results in approximately 45 seconds of memorable gliding flight.
It also provides a delightful souvenir of the gliding experience, the remaining portion of the (post-alarm) propeller, which is suitable for hanging on the wall of your living room.
Thank goodness it was an RV-3 aircraft. One of a very few that fly just as well power off as power on.Cool...what a ride !
No you don't. Because the moment you turn off the motor, it's not much of a glider.Well...I like the idea of a 20 ft spanning motorglider anyway.
I can see what caused the problem. The prop was a little out of balance.
Pffft, maths is only for people who need stuff to actually work.No you don't. Because the moment you turn off the motor, it's not much of a glider.
L/D performance is dependent directly on span and equivalent drag area. Minimum sink rate is dependent upon aircraft weight, equivalent drag area, and span loading.
Note that "span" figures into both of those critical glider-related performance parameters. A 20' span "glider" isn't going to be much of a glider unless it's exceptionally light and clean - in fact, it'd have to be a model, just like VB is saying.
Physics doesn't care what we want. If you want to design airplanes, Topspe... er, Speedboat100, you have to go beyond pretty drawings and start doing the math.
Oh, THAT.Pffft, maths is only for people who need stuff to actually work.
Hi, no response to e-mail or phone from here. Peter has bought a plane and is cheerfully commuting Cowra/Canberrra/Orange (J170, I think). So curses, I don't get to build one with/for him. Back to dreaming.To bring this thread back on topic, has anyone heard any news about Earthstar or the Thunder Gull lately? It really is an attractive little ultralight.
I corresponded With Mark briefly a few years back. He said that 250 Lb pilot would be no problem with soaring wings. He did a staggered tandem version too.A couple of questions regarding Earthstar in California. Airplane is Thunder Gull 2000:
1. Is Earthstar still a going concern? So far, no response to e-mail or phone, but my mate has only been trying for a couple of weeks. The web-site feels pretty current.
2. Peter is 1.87m and 95kg and 71. Roughly 6'2" and 200lbs. Any ideas on cockpit size, pilot weight and electric start?
3. Are the Gull 2000's only kits, or can one get a fully built one?
4. Does anyone know if there are any flying in Australia (or, at a pinch, NZ - though international flight restrictions could be a problem for a while yet).
Cheers,
Michael.
Hi Craig
The Load limits are 6+ 4- and we have tested the wing to failure. It yields as a bow in the wing and fails at the aileron flap juncture as it was designed to do. Every structure has a failure mode and I wanted it to fail in a manner that would present the best stability and clearance for the ballistic parachute, if you install one.
All the models are designed to the same limits and characteristics.
The power system complete with battery's and all is currently $13000 The Soaring Gull 2000 kit is $14,590.
Yes the electric power system should be purchased last.
The wing structure is a Dcell with the wash out built in, in our jig. The Dcell ribs are foam bonded in to the Dcell. The main spar is built up of aluminum angles riveted and bonded to a shear web. The aft ribs are formed from aluminum sheet. and the wing skins are of varying thickness sheets in relation of the local load. The skins are riveted and bonded.
The airfoil is my own design, the product of 20 years of study and 10 tests by taking a wing on a flying airplane and changing the airfoil by cutting the new shape out of foam and attaching it to the wing and measuring its characteristics.
It generates a lift coefficient of 2.0 as compares to the Cessna at 1.6 and the average ultralight at 1.1 this means that my wing only needs to be 1/2 as big as, say a rans for instance.
I am still studying ducted fans but I don't think that they are ready yet for prime time.
I really like Joby motors and will be spending several days at his place this week end doing testing and design work with him, JoeBen.
The Internet is a wonderful source for design information.
290# is not to much but I would encourage you to loose some weight since it takes power to lift every pound.
I hope I answered enough of your questions for now, feel free to ask whenever you come up with more questions.
Happy Flying
Mark
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This was a good advice. I got it now at 36 ft span.No you don't. Because the moment you turn off the motor, it's not much of a glider.
L/D performance is dependent directly on span and equivalent drag area. Minimum sink rate is dependent upon aircraft weight, equivalent drag area, and span loading.
Note that "span" figures into both of those critical glider-related performance parameters. A 20' span "glider" isn't going to be much of a glider unless it's exceptionally light and clean - in fact, it'd have to be a model, just like VB is saying.
Physics doesn't care what we want. If you want to design airplanes, Topspe... er, Speedboat100, you have to go beyond pretty drawings and start doing the math.