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Jan 09, 2019, 05:55 PM
Registered User
Thread OP
Question

Elevator Drag During Launch.


Because of my physical limitations, I am unable to use a momentary switch for my launch mode. I have my launch mode on a two way switch with up elevator. After launch, depending on when my hand gets on the transmitter, I flip the switch to flatten out the elevator. This usually happens about 3/4 of the way up, but sometimes it doesnít happen until I push over into level flight. I generally get about 90-110 feet in my launches in calm conditions and itís been pretty consistent for a few years now.

Iíve also recently developed an alternate method for a launch mode where I flip the two way switch prior to my hop/spin/launch and through a timed method, my elevator automatically flattens out on its own as it ascends (about 1/3 of the way up, I think). This method is a bit more complicated and it makes quick turnarounds impractical, which is a bummer.

So an aeronautics question... with the first launch method, since Iím plowing quickly upward through the air with some up elevator still activated though most of the journey, how much drag is being produced and what is it costing me? Is the drag bad enough to cost me, say, 20-30% of launch height compared to what it would be if I were able to use a momentary switch? Or am I only losing a few feet in the grand scheme of things?

If itís a very significant cost in overall launch height, Iíll continue to tweak and hopefully perfect this new method to flatten out the elevator as soon as possible post release. But if Iím only going to gain a few feet, Iíll probably just stick to my original simple method.

Thanks for any input and expertise.
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Jan 09, 2019, 09:16 PM
G_T
G_T
Registered User
If you had too much up elevator, you'd be doing a loop. Don't worry about it, you don't have too much.

It is more likely you don't have enough up elevator. But then you couldn't get it removed fast enough with your current methods. Anyway launches are a compromise; this is just your compromise.

You can launch at a somewhat upwards angle, PROVIDED you have good control of the proximity of your outer wingtip to the ground on the swing. Launching upwards some will improve your launch height. I do that and many others do as well. However we don't teach that to beginners or intermediate pilots as planes co$t more than launch height!

What about putting a long switch on the transmitter, and hitting the switch against the body, or against the throwing arm, to remove the up elevator? Ideally your up elevator time will be fairly short as you are essentially pulling a portion of a loop to end up going upwards at (in your case) appropriately about 70 degrees, moderately short of vertical.

At about a 30m launch height, you don't need to use a speed mode for the climb. It will not make much difference. You can just use cruise for the rotation and climb, and the pushover into horizontal flight. I'm thinking it won't cost you a meter. But if this simplification allows you some other options it might be worth considering. You will of course need some way of having up elevator applied before you let go of the model and release it very shortly thereafter.

A string which attaches to a sprung switch that is pulled when you cock your transmitter wrist into a football carry position?

Good luck with whatever you try!

Gerald
Jan 09, 2019, 11:55 PM
Registered User
Thread OP
Thank you Gerald. So in short, if Iím not doing a loop over my head, then Iím not getting enough elevator drag to make that much of a height difference. Good to know. I will do some experiments with the elevator and my launch angle to get more vertical.

I actually have mulled over ideas involving the use of strings or various switches... manual, magnetic, and otherwise to help get better launch height. But, I feel that the more complex it gets, the greater the chance of disaster. Thatís why Iíve tried to keep it as simple as possible. Though I do use the ĎHí switch on my TX, which is the longest switch, and is usually easy to locate unless I really fumble myself during launch.
Jan 10, 2019, 11:01 AM
Flying Low
cbarnes0061's Avatar
Can I ask what limits you from being able to use the momentary switch? Another option one of the local guys here did was add a momentary pushbutton to the back of his radio that falls right in line with his grip on it to begin with so all he has to do is squeeze his grip a little during launch.
Jan 10, 2019, 03:58 PM
JimN8UAY
Jimn8uay's Avatar
One handed launch...

Doug, just a thought outside the box...I'm sure a pressure switch, like a vario, would be able to detect the height after launch and could trip a logical switch in programming. Oh yeah, varios aren't permitted in comps...hmmm, some kind of microswitch or pressure pad on or near the launch peg that when released, sends a signal somewhere...I'm sure someone here will come up with an idea. I know you can program a delay in logical switches with some radio software, maybe you can program the launch to be only active for a set time frame and return to climb or zoom mode. This wouldn't allow you to hold for long unless you could easily reset it. Hope you can find something that works!

Jim
Jan 10, 2019, 04:35 PM
Registered User
Thread OP
Jim, the vario is a fascinating idea, but the problem could arise where I go back into launch mode when I’m flying closer to the ground.

I have used a servo delay programming in a launch mode that actually works ok. The problem is that it only slows the movement to the time selected. So a 5 second delay when the switch is activated means that it slowly flattens out over 5 seconds instead of holding it for 5 seconds and then releasing.

A proximity switch of some type would be ideal, or a magnetic or push button on a length of wire have possibilities, but then you start getting into complex things that can fail and destroy an expensive plane...
Jan 10, 2019, 07:49 PM
I'm not as bad as they say.
How about we make a bite switch that does launch mode?
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Jan 10, 2019, 11:06 PM
JimN8UAY
Jimn8uay's Avatar
I like that! Use a pressure switch you could chomp on, hardwired to your tranny! Just be careful not to swallow it...

Not sure what your radio system is you're using but Open TX would probably have the ability to work something with both hardware and software.
Jan 11, 2019, 01:10 AM
Registered User
Thread OP
Interesting idea. I use a Spektrum DX7 2nd Gen. I could probably hardwire it to a two way switch ‘harness’ and run a few feet of thicker gauge wire to make it sturdy.

Is a bite switch something that exists already?
Jan 11, 2019, 06:29 AM
Gone with the Mistral
ztoon13's Avatar
Quote:
Originally Posted by DougMaxwell
Is a bite switch something that exists already?
Yes it does for photography.
Jan 11, 2019, 08:08 AM
Flying Low
cbarnes0061's Avatar
Not sure how easy it would be to do wirelessly but having a wired bit switch would be really simple to do.
Jan 11, 2019, 08:14 AM
Wayne Wimbish
wdwimbish's Avatar
I think the switch on the throwing peg idea would be the most practical. Could even be an open circuit closed by a conductor on your finger or your glove if you use one. As soon as your finger comes off the peg the switch is triggered in your telemetry. You could program in a delay to give time to complete rotation to the vertical.

This would be a passive system so it would not depend on a positive action to make it work. Nothing to reach for, bite, or swallow.

Wayne
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Jan 11, 2019, 11:56 AM
Flying Low
cbarnes0061's Avatar
Quote:
Originally Posted by wdwimbish
I think the switch on the throwing peg idea would be the most practical. Could even be an open circuit closed by a conductor on your finger or your glove if you use one. As soon as your finger comes off the peg the switch is triggered in your telemetry. You could program in a delay to give time to complete rotation to the vertical.

This would be a passive system so it would not depend on a positive action to make it work. Nothing to reach for, bite, or swallow.

Wayne
How would you get the wires to the throwing peg without just taping them to the wing?? Not trying to knock your idea as I do like it.
Jan 11, 2019, 12:11 PM
Registered User
How about some sort of side Force sensor / accelerometer? If this idea is possible, a threshold could be set such that the launch command would only be sent to the transmitter during a launch spin / SAL. This way, there are no physical switches or wires and no need to reset anything.

Surely, a tiny "COTS" side Force sensor/accelerometer is available from Omega or such.

I bet there are some crafty FrSky/OpenTX/electronics folks on the forum whom could put something like this together, right?

Just a thought ....

Woody
Last edited by Tower_City_Woody; Jan 11, 2019 at 01:38 PM.
Jan 11, 2019, 08:23 PM
Wayne Wimbish
wdwimbish's Avatar
Quote:
Originally Posted by cbarnes0061
How would you get the wires to the throwing peg without just taping them to the wing?? Not trying to knock your idea as I do like it.
You could make a channel in the wing from root to tip during construction with a long piece of music wire and run some servo wire through it. Or you could just embed two pieces of music wire and they could be the conductors.

Connect them to conductive pads, one on each half of the peg. Put a matching pad on each of your throwing fingers coonected by some servo wire.

Thus fingers complete the circuit, and the cicuit is open upon release.

An alternate way would be by using some conducting trim tape on the surface with an insulating adhesive.

Making the peg into a conductive switch would not be too dificult. My question is what type of sensor would you connect it to, in order to initiate a change of flight modes?

Wayne
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