RE: 2 gliders in same thermal one is circling normally
The optimal strategy for climbing in a thermal is to fly at a constant angle of attack. Only one problem: we don't know how to do that. Jets have very good AoA sensors, and use them to good effect (especially in carrier landings!) but making one that will function at glider airspeeds and stand up to the ground-handling environment that goes with them has been elusive so far. And that's just in full-size gliders; in models, you'd have the added problem of providing a telemetry capability to display AoA on the transmitter.
Posted on: 5/17/2013 8:49 PM by Author "abelard" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=11514860

RE: Cost of glow fuel
I'm afraid I don't get the point of your post. [quote]AvGas is what amateur drag racers call 100LL.[/quote] Of course it is. That's also what aircraft operators call it. 100LL is 100-octane, low-lead aviation gasoline. [quote]Try running Jet A in your gasser and see what happens.[/quote] Whatever does Jet A have to do with it? Jet A is kerosene with some additives, and it's unrelated to avgas.
Posted on: 5/17/2013 7:05 PM by Author "abelard" in the forum "The Clubhouse"
http://www.rcuniverse.com/forum/fb.asp?m=11514787

Terrorism at the hobby shop
Some Florida counties are setting up an online system for your neighbors to report what you [link=http://jacksonville.com/news/crime/2013-05-16/story/tipping-law-enforcement-possible-terrorist-activity-purpose-13-county]buy at your LHS[/link]..
Posted on: 5/17/2013 8:04 AM by Author "abelard" in the forum "The Clubhouse"
http://www.rcuniverse.com/forum/fb.asp?m=11514186

RE: Reflex XTR2
Oops, my mistake...the 8.40 euro price was for the connector, not the disk. But the order page still gives 29 euro as the shipping charge. I'll drop Herr Küsel an email and see if I can arrange a download...I can make my own connector. rj
Posted on: 7/6/2009 12:58 PM by Author "abelard" in the forum "RC Flight Simulator Software"
http://www.rcuniverse.com/forum/fb.asp?m=8910778

RE: Reflex XTR2
Thanks for the reply. The good news: -No problem with the German site...ich kann Deutsch lesen. -XTR2 is version 5.05 and the software upgrade from 5.04 is only 8.40 euro. The bad news: -They only deliver the software on disk, no downloads. -Shipping from Germany is 29 euro. So, guess I'll wait for MRC to figure out how to market what they're advertising... rj
Posted on: 7/5/2009 3:01 PM by Author "abelard" in the forum "RC Flight Simulator Software"
http://www.rcuniverse.com/forum/fb.asp?m=8908224

Reflex XTR2
Sitting here looking at the ad for Reflex XTR2 in the new M.A.N., and a few questions arise: -Is there an upgrade deal from version 5.04? -Will my existing SlimStick work with XTR2? -I've just changed radios. Which of the three Airtronics connectors they list will work with an RD8000? Their home site, reflex-sim.de, now says almost nothing about XTR, and since it's a holiday, MRC isn't answering the phone... rj
Posted on: 7/3/2009 3:36 PM by Author "abelard" in the forum "RC Flight Simulator Software"
http://www.rcuniverse.com/forum/fb.asp?m=8903946

RE: Thrust line, Datum line, Center line?
The horsepower made a great deal of sense in its time. It was defined by James Watt as 550 foot-pounds of energy per second, and it enabled him to go to prospective customers for his steam engines and say "Now if you buy one of my engines, this is how many horses you can get rid of"... We know now that the horse or any other biological "machine" really sucks as a standard, because its power output depends a great deal on how it's coupled to the load. When Bryan Allen pedaled the Gossamer Albatross across the English Channel in 1979, he had to AVERAGE 1.3 hp for four hours. rj
Posted on: 5/17/2009 6:52 PM by Author "abelard" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=8777002

RE: Why make both engines critical ?
Sorry if some of the sentences in the above message are hard to interpret. I normally use a double hyphen to make a dash, and the message editor apparently deletes them completely... rj
Posted on: 9/14/2008 3:38 PM by Author "abelard" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=7953510

RE: Why make both engines critical ?
A propeller applies some torque around the yaw axis depending on the pitch angle of the airplane. If the airplane is in a nose-up attitude, the descending blade is at a higher angle of attack than the ascending blade, and produces a little more thrust. The formal name for this is "P-factor". If the rotation direction is "conventional" clockwise as seen from behind this thrust offset will make the airplane want to yaw left. That's why taildraggers need some right rudder on takeoff. If you lose one engine on a twin, you have a BIG thrust offset, and the airplane wants to yaw toward the dead engine. You counter that by applying rudder. This is no problem at cruise speed, because the rudder can deliver all the yaw torque you need. But if you slow the airplane up which you're certainly going to do, because you will really want to land the rudder will progressively lose authority and you'll have to apply more and more rudder. Eventually the rudder will hit the stop, and if you slow up any more you'll get an uncontrollable yaw, followed by an uncontrollable roll, followed by a splat. So that determines the minimum speed at which you can fly the airplane. At low speed, you're also in a nose-up attitude, so both engines will make the airplane want to yaw left. If the right engine quits, the P-factor of the left engine will be helping you on the rudder; if the left one quits, the P-factor of the right one will be fighting you...so losing the left engine hurts your low-speed controllability more than losing the right. Thus the left engine is called the "critical engine". One of the performance figures for a twin is Vmc, the minimum controllable single-engine speed, and it's defined as the lowest airspeed at which you can maintain yaw control with the critical engine dead and feathered, and the other one at full throttle. You never, ever get below Vmc on an approach, and never lift off the runway below it, because if you lose an engine you're in deep yogurt. If you build the airplane with counter-rotating props, there is no critical engine, and in the definition of Vmc you can substitute "either" for "critical". If the descending blades are on the fuselage side of the engines i.e., the right engine rotates "backwards" the P-factor will help out in a failure of either engine. If they rotate the other way, the P-factor will always hurt, and Vmc will be higher. But this really isn't a BIG factor: it's a matter of a few knots. Various airplanes, including the P-38, have realized benefits from "wrong way" rotation that outweigh a small increase in minimum speed. Interesting to note that certain extreme single-engine airplanes, like the P-51, have what amounts to a Vmc: you can't do an unaccelerated stall at full throttle, because you will run out of rudder before you get down to stall speed. rj
Posted on: 9/14/2008 12:27 PM by Author "abelard" in the forum "Aerodynamics"
http://www.rcuniverse.com/forum/fb.asp?m=7953047

RE: Unassembled Robart hinges?
Actually I'm not as interested in making the surface removable as I am in getting precise alignment of the hinge axes. It would be nice if I could use a single long wire, under tension, to line up the hinges on one surface and epoxy them in place; remove the wire and assemble the hinges with rivets; then epoxy the other end of the hinges into the mating surface. Precise alignment, but no long kludgey-looking wire. rj
Posted on: 12/29/2007 5:11 PM by Author "abelard" in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=6822457

Unassembled Robart hinges?
Does anyone have experience with using the unassembled version of the Robart Hinge Points? The hinge pin in the assembled units is actually a very small rivet, obviously installed with a special tool. Robart advertising offers no information about these pins or the tool. So what do people use? Thanks... rj
Posted on: 12/28/2007 8:22 PM by Author "abelard" in the forum "Scratch Building, Aircraft Design, 3D/CAD"
http://www.rcuniverse.com/forum/fb.asp?m=6818364

RE: Airline Humor
Alternative ending to the same story: "I just shut down an engine." rj
Posted on: 11/23/2007 10:32 AM by Author "abelard" in the forum "RC Humor"
http://www.rcuniverse.com/forum/fb.asp?m=6662019

RE: Airline Humor
Okay, somebody has to do it... An airline pilot was taking his 6-month physical, and the doctor asked "How long ago was your last sexual experience?" The pilot replied "Oh, let's see, that was...ummm...about 1957." The doc said "Kinda been a while, hasn't it?" The pilot replied "Well, yeah, but I had to leave at 2015 to come over here." rj
Posted on: 11/19/2007 11:55 PM by Author "abelard" in the forum "RC Humor"
http://www.rcuniverse.com/forum/fb.asp?m=6648140

RE: Airline Humor
IFF = Information, Friend or Foe. An early radar transponder deployed during WW2 to distinguish friendly aircraft from enemy aircraft by returning an encrypted pulse. rj
Posted on: 11/19/2007 11:51 PM by Author "abelard" in the forum "RC Humor"
http://www.rcuniverse.com/forum/fb.asp?m=6648124

RE: Airline Humor
One more: P: #3 prop leaking oil. S: Leakage is normal. P: #1, 2 and 4 props lack normal leakage. rj
Posted on: 11/16/2007 6:38 PM by Author "abelard" in the forum "RC Humor"
http://www.rcuniverse.com/forum/fb.asp?m=6633915

RE: Hostetler Skybolt
I've just started on one. I've molded the cowling, welded the cabane, and and I'm making ribs in between applications of glass to the wheel pant molds. Watch this space...;-) rj
Posted on: 11/16/2007 5:40 PM by Author "abelard" in the forum "Giant Scale Aircraft - 3D & Aerobatic"
http://www.rcuniverse.com/forum/fb.asp?m=6633658