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Old Mar 15, 2006, 09:16 PM
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flieslikeabeagle's Avatar
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English terminology is a world apart from American, and very much more colourful: gudgeon pins, tappets, con rods with big-ends and little-ends, where here in the USA we have mere piston pins, lifters, and piston rods, for instance. The educated English person knows the difference between the words "knowledeable" and "smart", while in the USA we think they're the same thing, if we've ever heard of the word "knowledgeable" at all.

Okay, then, guess I'll go fly some bunts next time I'm at the field!

-Flieslikeabeagle
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Old Mar 15, 2006, 11:30 PM
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Quote:
Originally Posted by flieslikeabeagl
Thanks for the link. FWIW, I don't see the term "push" used in the description of an outside loop on that page, either!

As I've heard it used, "outside loop" simply means the canopy points away from the center of the loop; inside loop means the opposite. But I haven't spent any time at pattern competitions, so I've no doubt I have plenty of terminology to pick up here.

-Flieslikeabeagle
You may want to look through some descriptions of FAI F3A aerobatic schedules:

http://www.australianpatternassociat...scriptions.pdf

You will find "push into an outside loop" quite often there (P-05.9, P05.12 for example).

Jürgen
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Old Mar 16, 2006, 12:28 AM
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Quote:
Originally Posted by flieslikeabeagl
...

Okay, then, guess I'll go fly some bunts next time I'm at the field!

-Flieslikeabeagle
The "bunt" is something only flown in England - but what do you expect from guys who drive on the wrong side of the road.

Jürgen
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Old Mar 16, 2006, 02:13 PM
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Bill Glover's Avatar
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Quote:
Originally Posted by Jurgen Heilig
The "bunt" is something only flown in England
Bet the term is shorter than the equivalent word in German

Actually, it's quite useful to be able to distinguish between the two types of outside loop (starting from level upright, or starting from level inverted).
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Old Mar 16, 2006, 05:04 PM
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Quote:
Originally Posted by Jurgen Heilig
The "bunt" is something only flown in England - but what do you expect from guys who drive on the wrong side of the road.

Jürgen
The "English Bunt" is an internationaly recognised aerobatic manoeuvre (that is the international english spelling of manoeuvre).

Tony
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Old Mar 16, 2006, 05:25 PM
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Hey guys,
Bright red base coat is on and drying Why red? I had three cans of the stuff. Prolly do blue star bursts on the bottom and yellow starbursts on top.
We'll see how I feel in the morning, so far, so good...
RobII
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Old Mar 16, 2006, 06:39 PM
Hold my beer and watch this!
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Rob, did you have a look at some of the paint jobs on TS2s over at Patrick's website? Some of the more plain ones look the best to me. (Red wing-tips, red elevator tips)

http://plawner.net/4/twinstar2/galle...2_gallery.html

flieslikeabeagl, How ironic is this? I've been hassling you all along to get that bird in the air and quit theorizing. Now, you're a breath away, and mine's under the knife. If I hurry, I may be able to beat you up there again, hehehe. (one brushless wing's done, one to go.)

English terminology is a funny thing. (to me) My wife and I may move there some time in the next year or two, and it will take some getting used to for me. She's purebred Polish, and learned UK English since she was a little lass. Me? American English since I was a lad. It'll be tougher for me, even though English is my native tongue.
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Old Mar 16, 2006, 11:33 PM
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Quote:
Originally Posted by ModelTony
The "English Bunt" is an internationaly recognised aerobatic manoeuvre (that is the international english spelling of manoeuvre).

Tony
That is correct, but you won't find this maneuver called "Bunt" in an F3A sequence. It would be called "half outside loop" starting from level flight.

An "English Bunt" is only half an outside loop anyway - and I don't think a full loop would be called "Double Bunt" or "Two Bunts".

I would not consider the TwinStar II for a good aerobatics trainer anyway.

Jürgen
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Old Mar 16, 2006, 11:42 PM
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Jeremy, you may beat me to it yet, I still haven't finished the build...this evening I had the time to do some building, but I bolted for the flying field instead and stayed there till it was cold and dark, chatting with a couple of flying buddies after it was too dark to fly.

Be prepared for lots of spelling changes too, after that move to the UK! Color becomes colour, analog becomes analogue, meter (the unit of length) becomes metre, you no longer get a paycheck but rather a pay cheque. When you work hard you tire, but what you put on your cars wheels are tyres, not tires. Go to a restaurant in the USA and you pay the check with a (dollar) bill, in the UK you pay a bill with a cheque. And so it goes.

I was asked to elaborate on the wiring I did to allow one BEC to feed the two aileron servos, while the other feeds the rudder and elevator servo. So attached below is a rough wiring diagram. I used colours that correspond to the actual wires. Wires that connect have a little blob at the intersection, wires that do not connect run straight across each other.

If you look closely, you'll see that that the BEC in ESC 1 powers the two aileron servos; because the red +5V wire is NOT run to the receiver's aileron channel, ESC 1 does not power the receiver itself. Also the two red +5V wires from the two BEC's never meet, so they never fight each other or get the chance to share the load unevenly, burning one up while the other does no work at all.

Meantime, the BEC in ESC2 powers the receiver, and through it, the rudder and elevator servos. But why the heck is the black wire from ESC 2 not connected to anything? How can ESC 2 power the reciever if the black wire is left dangling? Well, the key is that the black wire from the BEC (in both ESC's) is internally connected to the thick black battery wire from that ESC. So the receiver gets grounded through the black wire going to the aileron channel, and the BEC in ESC 2 is already grounded to its black battery cable, which goes to the other ESC's black battery cable...so everything gets grounded as it needs to be!

Please not that the aileron servos are commoned, as they would be if you used a Y-cable. Similarly, the two ESC throttle signals are commoned also. If you have a 7 or 8 channel receiver and a transmitter with lots of mixing capabilities, you need not do it this way - but the Spektrum DX6 has limited mixing capability and only 6 channels available, so I chose to do it this way. This leaves the channel 5 and 6 outputs of the receiver unused...so you could turn on night lights, release paradroppers, or what have you with those two channels if you want.

-Flieslikeabeagle
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Old Mar 17, 2006, 05:04 AM
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spudandretti's Avatar
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Quote:
Originally Posted by flieslikeabeagl
but the Spektrum DX6 has limited mixing capability and only 6 channels available, so I chose to do it this way.
-Flieslikeabeagle
It has enough for what I do, I am running seperate aileron channels so I can adjust seperately and have flaperons and spoilerons if I choose.Bud
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Old Mar 17, 2006, 07:14 AM
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Quote:
Originally Posted by flieslikeabeagl
...
Also the two red +5V wires from the two BEC's never meet, so they never fight each other or get the chance to share the load unevenly, burning one up while the other does no work at all.
...
-Flieslikeabeagle
Actually, most modern ESCs allow you to run two BECs in parallel. Quite often they even use two BECs on one ESC. Have a look at Kontroniks Rondo 600 series, or Castle Creations TB 18.

I have three models with differential motor control and have both BECs active. Two Schulze slim-15be, two Kontronik Rondo 300 and two Smile 40-6-12 - never had a problem.

Jürgen
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Old Mar 17, 2006, 11:07 AM
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Jurgen, I understand that most BEC's can be run in parallel without hurting the BEC's. However I think they have to be extremely well matched in voltage, otherwise one of them will basically do nothing while the other supplies all the current. You also create the chance of RF oscillation, as Franck found out and reported earlier in this thread.

This is inherent in their design: most voltage regulator chips (which is what is in a BEC) can source current, but not sink it. That means if I connect a 6 V battery pack to a 5V BEC (voltage regulator chip), no current flows back into the regulator, so it isn't hurt. Also no current flows from the BEC to the battery, because 6V is bigger than 5V.

However: if I have two BEC's with slight factory mismatches, say one of which puts out 5.0 V, and the other 5.05 V, and I connect them together, the same thing happens. When I load up the combination with servos, the 5.05 V regulator puts out all the current, while the 5.0 V regulator does nothing.

Modern regulators have very tight voltage regulation - the voltage from the 5.05V regulator hardly drops under load - and ironically, this normally desirable feature actually makes things worse in this particular situation. If the 5.05V regulator were to drop to, say, 4.95 V under load, then the other regulator (the 5.0 V one) would start to share in the work, though not equally. But todays high quality voltage regulators don't typically drop that far, and that means the second voltage regulator (BEC) just sits on its fanny, twiddling its fingers, and doing absolutely nothing while the first BEC overheats and cooks.

I've seen high-power voltage regulator circuits that used multiple voltage regulator chips or output devices, and usually small resistors are added to the circuit that force the devices to share the load more or less evenly. Perhaps this is done in the Kontronik and TB 18 ESC's you mention. But depending on exactly where those resistors go in the circuit, they may or may not do the same job (enforcing equal current sharing) when two separate BEC's from two separate ESC's are paralleled.

Short version: if you parallel the two BEC's, you may or may not have a problem. If you avoid paralleling them, as I did, you certainly will not have a problem.

-Flieslikeabeagle
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Old Mar 17, 2006, 11:18 AM
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Quote:
Originally Posted by spudandretti
It has enough for what I do, I am running seperate aileron channels so I can adjust seperately and have flaperons and spoilerons if I choose.Bud
Bud, I have dual aileron servos in my 8-oz Multiplex Stuntman, and after some tedious minutes with the DX6 manual I managed to get them mixed as I wanted. I don't want flaperons on that model, just conventional ailerons, so I wasn't expecting to need the "flaperon" menu item on the DX6. I tried to do the job with one of the programmable mixes, and got differential movement, but also huge offset - with the stick centered one aileron was way up, the other way down.

With the Twinstar, in the back of my mind I'm thinking about a lighting system for dusk flying, or actual flaps cut into the wing a la Franck, or perhaps a payload release setup to drop parachutes. So I wanted to keep some channels free on the AR6000 receiver. With a four channel plane and only six channels on the receiver, I chose to just parallel the two throttle signals, and the two aileron servo signals. That leaves me the "gear" and "aux" channels free for any future use.

Quite likely I will never actually do anything with them, but it's fun to daydream.

Hobby Lobby recently put the Scorpio Fox aerobatic sailplane on sale at a blow-out price, and I couldn't resist buying one. This is a good sized lightweight, moulded Depron model, pretty much a flying eggshell like my Multiplex Stuntman. I can't help wondering if the Twinstar might not make a good tow plane for the glider...

-Flieslikeabeagle
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Old Mar 17, 2006, 11:38 AM
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I just picked up the April 2006 issue of Quiet Flyer. In it is an article on using Motocalc 8 to choose power systems for model airplanes.

The author happens to use a Multiplex Twinstar II as his example. It is interesting that MotoCalc found the stock power system so inefficient it would not even consider it! Here's an excerpt from the article, starting at the point where the author had just input the airframe numbers into Motocalc:

"...it recommended 907 acceptable drive trains. After I restricted it to brushed direct-drive motors, that number fell to 184. Restricting it to an 8-cell NiMH or NiCd battery dropped it to 6. <SNIP> Getting curious, I then limited the motor choice to the stock Speed 400 6-volt cans, and propellers to the stock 4.9x4.3 in Gunther Spoon. Motocalc then reported that no drive train at all was efficient enough to consider."

Of course, a biased person can always just dismiss that result and believe that the Multiplex 400 and Gunther prop have magical properties and it is MotoCalc that is wrong. But a person with less bias may know that technically knowledgeable users of MotoCalc typically report 10% accuracy with most of its predictions, very good considering all the variables involved.

I don't use MotoCalc, because I switched to Linux years ago and there is no Linux version of MotoCalc (though I did run it under a Windows emulator once for fun a year or so ago). I independently came to much the same conclusion that MotoCalc did, though.

-Flieslikeabeagle
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Old Mar 17, 2006, 11:40 AM
Honey,just one more thing
spudandretti's Avatar
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Quote:
Originally Posted by flieslikeabeagl
some tedious minutes with the DX6 manual I know that for sure I can't help wondering if the Twinstar might not make a good tow plane for the glider...I was thinking that too, but I would probably need a brushless setup. Can you recommend a setup for me Bud
-Flieslikeabeagle
Had to throw alittle jest in there.
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