How to's....?? single channel,free flight

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bluejets
Posts: 258
Joined: 19 Jun 2019, 04:09

How to's....?? single channel,free flight

Post by bluejets »

With the obvious come back of single channel in the UK at least, thought there might be info floating around out there somewhere that the professionals may be able to point to.
I came into model flying on control line and when I looked at radio, it was at the beginning of proportional sets.
Had many books on the subject of single channel building and flying from the UK but sadly all went in the 2013 flood here.
These days, as long as there is enough grunt up front, one can "make" almost anything fly but the single channel/free flight is an entirely different story. 8-)
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PaulJ
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Joined: 16 Feb 2018, 19:01
Location: Ipswich, UK

Re: How to's....?? single channel,free flight

Post by PaulJ »

Like most things in model flying, single channel isn't difficult but it's more an art that needs to be learned and there are a few things that may smooth out the learning curve........ What kind of "info" are you looking for? :?

Paul
bluejets
Posts: 258
Joined: 19 Jun 2019, 04:09

Re: How to's....?? single channel,free flight

Post by bluejets »

Setting up the aircraft to begin with, for rudder only flight.
Things to avoid etc.
Spike S
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Joined: 16 Feb 2018, 14:59
Location: Salisbury UK

Re: How to's....?? single channel,free flight

Post by Spike S »

Think of S/C RC as "Guided Free Flight" with starting point as mildly-disturbed direction control of a stable airframe. Leave the Sharkfaces till later !
Lots of advice on the SAM 35 sites but if you Google "trimming free flight models" you will get lots of hits & utube vids.
Even better if you get get alongside some FF flyers to better guide on what is relevant and what is not :)
Spike S
(Tune for maximum smoke)
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PaulJ
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Location: Ipswich, UK

Re: How to's....?? single channel,free flight

Post by PaulJ »

I would agree with Spike that you should start with something quite stable that will happily fly itself and to start with, all you do is interfere with it's flightpath...... Something like a Junior 60 maybe? Start with the CG around 25% - 30% of wing chord and trim it for a straight, flat glide over the proverbial long grass. Do persevere with the glide trimming and get it just right so that when you fly it under power, any further trimming is only to the thrustline and possibly the rudder. Under power it should climb steadily but not so rapidly that it will eventually stall/zoom so this you will adjust with washers under the engine bearers..... You will probably need several degrees of downthrust. For this reason I like to have an upright engine and adjust any turn under power with rudder trim. (If the engine is mounted "sidewinder" you can't adjust the thrustline up and down). Personally I prefer "compound"(one for right, two for left) to "sequential" (right/neutral/left/neutral) so I trim the model for a very gentle left turn so left to it's own devices it will fly in gentle left-hand circles and all you need to do to get it to fly straight or turn right is give an occasional blip of right rudder. If you hold the rudder on, the model will drop it's nose and eventually you get a spiral dive so level(ish) turns are accomplished with a series of short applications of rudder. Usually the model will need a dab of opposite rudder to stop it turning but in a right turn, the fact that the rudder cycles through left on it's way back to neutral is often enough. When the model is turning, application of opposite rudder not only stops the turn and eventually starts it turning the other way, it also causes the nose to rise and this is the basis of how you can do some limited aerobatics. By waggling the rudder left/right/left/right you can use this effect to raise the nose slightly to arrest the rate of descent when landing on the glide.

Things to avoid:-

Too much rudder movement.... Obviously it depends on the size of the rudder but you really don't need much!

Too much power..... Power usually means speed, which will give you a big difference in trim between power on and power off and it will only get you into trouble.

CG too far aft..... This is the main difference between trimming a freeflight model and trimming a radio controlled model. Some freeflight models have the CG well aft to the point that the tailplane is lifting. This is ok when the model only flies at one speed but it is not what you want for a single channel model so I would say CG no further aft than 30% of chord

Steer clear of rubber driven escapements! They have their devotees but they are just not reliable...... particularly old ones! I am totally sold on Phil's single channel encoder and a servo to drive the rudder because it works every time and if the model doesn't do what you expect, at least you know it is your fault and not the b****y escapement skipping again! If you also have a propo conversion using one of Phil's 7-channel encoders, you have the wonderful option of trimming the model out using propo and when you feel brave enough you can use the button...... and if you get into trouble you can rescue it with propo!

You have obviously flown other r/c models so maybe you could bypass the J60 stage...... I have just built a Mini-Robot which is easy and a delight to fly under the very modest power of a Mills .75. It has "adequate" power to fly reliably and will just about do a barrel roll but no more, so I am about to try it with DC Merlin or possibly a PAW .80.

Good luck, it's great fun!

Paul
Stew
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Re: How to's....?? single channel,free flight

Post by Stew »

All above advice excellent.

From my POV I started with a Tomboy. Built to the FF plan but single 5g servo with closed loop on rudder (and very little movement).
Few gentle glides into long grass, little bit of packing (1/16) under the t/e of the stab, and then a nice floaty glide. Fire up the Mills and launch. Just a gentle nudge every now and then. Gradually turned up the wick until over progressive flights until it was a mere speck way up when the motor cut. Vic Smeeds Poppet is excellent, and simpler to build than the Tomboy. Both fly very well. Had some amazing relaxing single channel flights with that.
It's mostly free flight, with radio to keep it in the field. Sometimes I put the Tx down on the grass.
I found It's nice to have something that can get 'Two mistakes high' on it's own before even touching the button, and plenty of Vic's designs will do that with the minimum of trimming.

As mentioned Phil's 7 channel encoder with button and sticks is great. If you chicken out or it's all going pear shaped, back to the sticks.

Stew.
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