Switching to electric gliders from fixed wing large scale electrics

[Steve Houghton 1]

1 hour ago, Frank Skilbeck said:

Adrian, if you could replace the wing retaining bolt with a plastic one that may help in an "arrival" breaking instead of pulling the bolt through the fuselage or the fixing out of the wing root. 

None of my gliders using a wing retaining bolt, they either use the wing snap locks e.g. Multiplex Multilock or just a rubber band between the wings, these will both give in case you happen to do a one wing low landing.

You took the words right out of my mouth Frank!

[Adrian Smith 1]

I never did understand why the butterfly bolts were included in the kit, even if they could be fitted. Bad design. I take your point on board + low wing landings, Frank. I have had a chequered career with plastic/nylon bolts as it hasn't taken me long to strip the threads on the cheap ones given they screw in metal claw nuts. In my defence I have used metal bolts on all my I/C aerobats without incident (apart from crash nose diving my Extra 330SC recently), but then the wings are much shorter!! I will have look at the plastic bolts I have in my spares box to see what I can find. Experience shows that the sizes and thread count in plastic bolts don't always match the claw nuts insitu. Anyway I will give it a try although it might be a problem finding some with a small enough head to fit next to the former. Anyway, I will report back.  

 

Edited November 24, 2021 by Adrian Smith 1

[Adrian Smith 1]

Sadly couldn't find some suitable plastic bolts so back to my regular supplier .....

 

https://www.modelfixings.co.uk/nylon_screws.htm#cheese head

[Adrian Smith 1]

For info I set the working surfaces as a starting point as follows:-

ailerons via a Y-lead 15mm +/-

elevator 15mm +/-

Rudder 12mm +/- which was as much as I could put in.

the flap/brake +/- needs a bit of thought as I have no idea how much to dial in (I am using channels 7 & 8 for port and starboard resprctively. 

Edited November 25, 2021 by Adrian Smith 1

[Frank Skilbeck]

For starting flights I would also add in around 50% aileron differential to counter adverse yaw etc. do they have to be on a Y lead?

 

For flap/brake you use a crica 5 degrees for thermal flap and then 60+ degrees for landing, you would typically have the thermal flap setting on a switch (flight mode) and flap on proportional control and set up for crow braking, i.e ailerons raised/flaps down with some elevator compensation. Glider guiders would normally put this on the "throttle" stick so they can modulate this during landing, but power fliers often find this a bit confusing so go with what you are comfortable with.

 

The difference with a glider is that you modulate the brakes to control the landing and leave the throttle shut, whereas with a powered plane with flaps you would drop the flaps and then adjust the approach using power.

[MattyB]

11 hours ago, Adrian Smith 1 said:

For info I set the working surfaces as a starting point as follows:-

ailerons via a Y-lead 15mm +/-

elevator 15mm +/-

Rudder 12mm +/- which was as much as I could put in.

the flap/brake +/- needs a bit of thought as I have no idea how much to dial in (I am using channels 7 & 8 for port and starboard resprctively. 

 

@Frank Skilbeckis absolutely right - you need to ditch the Y-lead and setup ailerons on separate channels with a mixer, otherwise you will not be able to use differential. Diff is absolutely essential on high A/R models such as this - start with at least 2:1 (up:down) for your first flights, but you may need more.

 

PS - When you deploy crow brakes you may want to reverse the diff (to 50:50 or maybe even more down thatn up), as there may not be sufficient up movement to retain full aileron control. This can feel worrying when you look at it setup on the bency, but the wing is washed out enough that the downgoing aileron drag is not really an issue.

 

Edited November 26, 2021 by MattyB

[Adrian Smith 1]

Frank, Matty.

I can see I have a lot to learn about this section of the hobby! As a I/C power flier, details such this were like a foreign language compared the straightforward job of setting up an aerobat such as an Sbach or Edge 540.

Firstly, I have spare channels on my Futaba RX therefore that won't be a problem. Furthermore my T14SG TX has plenty of scope for mixing along with an array of switches I can assign. I just need to get my head around the terms such as adverse yaw. I have never flown a I/C aircraft  with flaps as most of my experience is with modern aerobats. Thanks, much to study. 

Edited November 26, 2021 by Adrian Smith 1

[Frank Skilbeck]

Download a copy of the Multiplex Heron manual, Multiplex do a good job of explaining the set up and it would be a good starting point for your glider, unfortunately a lot of the far east gliders just seem to come with a standard generic setup as though nobody has really flight tested the model.

 

Did a set up with a friend a few years back of a glider with thermal/speed flap settings, mixed aileron/flaps and crow (or butterfly in Futabaeze), the only issue we had was finding the flap servo offset function, I think it was in the dual rates menu (but it was a while ago so may be wrong)

[Geoff S]

3 hours ago, Frank Skilbeck said:

For starting flights I would also add in around 50% aileron differential to counter adverse yaw etc. do they have to be on a Y lead?

 

 

 

Adrian is using a Y lead for ailerons, he won't be able to add aileron differential electrically but he might be able to do it mechanically by adjusting the servo arm position on the servos.

[Adrian Smith 1]

Very helpful, Frank, I will do that. The TX manual is really detailed with whole section devoted to glider set ups. I must admit I have tended to ignore that part until now, but needs must. My glider manual, I hesitate to call it a manual, is basic to the extent of being useless. The only guidance is aileron throw up/down 20mm and elevator up/down 25mm. Not very helpful you will agree. I think you right about non-flight testing in the F/E.

 

Geoff.

I will dispense with y-lead and use separate channels and looking at the Futaba TX manual I should be able add aileron differential as there are all sorts of options/mixes for gliders. 

[Adrian Smith 1]

 

An interesting article I found online explains all to a novice like me ?

 

https://www.rc-airplane-world.com/aileron-differential.html

[Frank Skilbeck]

Yep, that's basically it and on a glider with longer wings the downgoing aileron drag has a larger moment arm than on a regular powered model. But I even put aileron differential on my scale biplanes and warbirds, some times different amounts in different flight phases. We are getting a bit off topic but full sized designers did/do use aileron differential and also things like frise ailerons where the leading edge of the upgoing aileron would protrude below the wing to add drag on that side to balance the down going aileron on the opposite wing.

 

From what i recall of the 14sg, you will have to select glider mode to access things like butterfly and thermal/speed flap settings, you might need to check but on the earlier releases of the 14sg I think when you were in glider programming the "throttle" stick was allocated to butterfly by default.

[Adrian Smith 1]

? right noted, Frank. looks like I have a bit of reading/fiddling to do over the weekend!

[Adrian Smith 1]

Couple of questions which you gliding experts will know have simple answers, but I now realise more than ever every day is a lesson day.

 

Would a simple fix of mixing some rudder with the ailerons correct adverse yaw without aileron differential dialled in?

Am I right in assuming in a port turn the rudder mix should be to port too?

Would I be right in saying that both aileron differential and rudder mix at the same time in a given situation would be overkill? One or the other or both?

I know I am sounding a bit dumb on this, but bit of learning curve for me. Thanks.

 

 

 

[Frank Skilbeck]

Adrian, my thoughts as follows

 

Would a simple fix of mixing some rudder with the ailerons correct adverse yaw without aileron differential dialled in?

- Yes, but often on a glider you will instigate a turn with the rudder and then control the bank on ailerons and use ailerons to come out of the turn

Am I right in assuming in a port turn the rudder mix should be to port too?

- Yes

Would I be right in saying that both aileron differential and rudder mix at the same time in a given situation would be overkill? One or the other or both?

- No, on my Heron in aerobatic mode I have slightly reduced aileron differential and no rudder mixing, with the flaps also working as ailerons (but only upward) to give a crisper roll rate, but then the model is typically flying faster, in thermal mode I have aileron differential and little rudder dialled in for flatter thermal turns, for landing I have the butterfly control active aileron differential and rudder mixed in, with aileron differential reducing as both ailerons are raised.

 

The model you have got will most likely be prone to tip stalling, unfortunately smaller thin chord gliders often are, so it's wise to avoid this, when you are hooning around at speed then you probably would notice the adverse yaw, but in slow thermal turns you will probably get a sudden wing drop (same on landing if you are too slow) and this is where aileron differential will help.

 

I am not sure where you will be flying but one of the biggest differences you'll note flying the glider as opposed to an aerobatic model is how shallow the glide slope will be, and putting the nose down will give you a big increase in speed so when you do go to flare out it will seem like it wants to go on forever, hence some form of airbrakes are very useful, especially if you don't have a very long obstacle free approach.

 

If you spend a bit of time now setting up the radio to allow aileron differential then you can tweak it easily at the field to suit your preference, starting like Matty says with a 2:1 ratio.

 

 

[Adrian Smith 1]

That's really helpful of you, Frank. I am sure I read somewhere about these models being prone to tip stalling which you confirm. 

Fortunately, I do have a long obstacle free approach being as it is an old WW2 USAAF airbase. No clubs are permitted there given the presence of a light aircraft whose group allow me as a solo flyer up there to "do my thing". The problem with that, if it is a problem, is I have no club mates to ask such questions. 

 

I am going to delve into the specifics on my TX this afternoon and try a bit of programming. I will adopt the 2:1 aileron strategy by doing away with the y-lead and using separate channels and mix in a little rudder too. It will be a cautious start although it might be a while before the maiden flight. 

When I have sorted that out I will start to think about the flap/brake function at some point. Thanks again.

 

 

[Jonathan M]

Adrian

 

Its not actually that hard learn to feed in rudder manually as you need it (after having set up the right amount of differential of course) especially as your rudder thumb should already be quite proficient from your power aeros experience.

 

For thermal model flying:

 

1.  Roll gently into turn using ailerons, plus a bit of same rudder to iron out any adverse yaw, and as much elevator as you need.

2.  Maintain turn using rudder (and elevator as needed), apply some opposite aileron as needed (won't be much) to prevent rolling any further in - also a lightly banked wing will obviously be more efficient in terms of generating upward lift than a tightly banked one.

 

You'll see from the above that if you have rudder coupled to ailerons (CAR), then your turn-direction rudder input will be countered by the opposite-direction rudder (via the ailerons) and you won't know where you are at all!

 

 

[Adrian Smith 1]

Makes sense Jonathan. By my own admission my use of the rudder in power aeros could be more extensive - I only use it for knife edge, stall turns and flat spins and of course on take off! I have looked at the TX and it seems straightforward to dial in aileron differential. Just need to go to the work shop to try it all out. I like less complication therefore not adding an aileron- rudder mix too will simplify things. After all this particular glider is not that sophisticated compared some of the bigger ships.

[Adrian Smith 1]

Right, managed to get the ailerons sorted out. The differential is 20 mm/10mm to counter adverse yaw. The flaps are 30mm down which is as much as I can get given the servo housing is restricting it from more. The other related coordinated controls for the ailerons and flaps I haven't programmed in yet.

The other thing I noticed is the aileron/flap alignment on the starboard wing. The aileron at neutral aligns with the wing tip and the inboard side of the flap aligns with wing root. It's just that the outer part of the flap doesn't align with the inboard side of the aileron. Either there is twist there or something else. As can be seen from the photos the port side all aligns up nicely. Not sure what I am going to do there.

 

[Jonathan M]

Re the slight twist on the starboard side - can you check whether it is in (a) the flap, (b) the aileron, or (c) the wing itself?  If it's in one of the control surfaces then you might be able to work (or bully?!) it out somehow, if it's in the wing that'll be a bit more difficult.  A small residual error shouldn't be too problematic but, just like on a regular power model, the trick will be to initially manually trim the twisted control surface to an average position, then tweak it via the trim on the RX while test flying.  You'll lose a teeny bit of efficiency due to drag on that wing but not sure you'd notice it in practice.

[Simon Chaddock]

It will require some good eyeball but if you are happy the left and right flaps and aileron are not twisted it could simply be the rear of tip that has got deformed and could be safely be "reworked2 more for cosmetic reasons than aerodynamic.

If there is even a hint that the one or both of the control surfaces have a twist you will have to decide if it is significant. The danger is that trying to untwist by manipulation and the use of heat may do more damage than it fixes.

My money on the tip being out of line but in any case the plane will fly perfectly well just left as it is.  

[Jonathan M]

Re your initial settings - surface travels, differential, etc - are those as given in the manual?  Are you going to programme in flaps as 'flaperons' (i.e. with up/down movement at a proportion of aileron travel in normal flight)?  Does the manual say anything about this?

 

On a non-scale four-servo wing competition thermal glider the following is normal:

 

• Flaps normally move as a proportion (say 50%) of aileron movement.
• In Thermal Mode an equal amount of camber is applied to both flaps and ailerons.
• In Cruise Mode both flaps and ailerons are flush with the wing root, i.e. in a neutral position.
• In Speed Mode an equal amount of reflex is applied to both flaps and ailerons.
• The amount of camber (say a few mm max) or reflex (just a mm or two) is normally specified by the designer/manufacturer as a starting point, then can be tweaked by the flier to suit their own flying style.
• Selecting between flight modes is normally done using a 3-position switch, although some fliers like to then have the exact amount of Thermal Mode camber further adjustable via a slider (but only active when that mode is selected).

 

• With crow-brakes (aka butterfly) for slowing down for (spot) landings, the amount of down-travel on the flaps is much more than the up-travel on the ailerons.  So some down-elevator needs to be mixed in to stop the nose from pitching up, and this is usually on a curve (found by trial and error) where the down-elevator compensation is greatest initially, then continues but at a lower rate as more braking is applied.
• Most competition flyers put braking on the throttle stick (rather than a slider), where normal flight is carried out with the stick fully up (think of it as 'full-throttle') and maximum brakes with the stick fully down (i.e. similar to 'idle').

 

• As braking is on the throttle stick, it is then normal to put throttle on a slider (on the same side of course as your normal throttle-stick).  While this gives less physical range than a stick, the fact is that throttle is only normally used for launching where (after a soft-start) you want maximum beans until you reach motor-off altitude.

 

This is how the TX then looks - based upon the setup I'm using with my Taranis, developed for Open TX by RC-Soar:  template for F5J class electric sailplanes with 6 servos + ESC

 

 

All this might be much more than your own model is designed for, but I hope it gives you a helpful overview - from which you can pick and choose the basics.

 

Edited November 29, 2021 by Jonathan M

[Adrian Smith 1]

Yes, Simon I will give it a good eyeball examination tomorrow. I think you are right though in that it is probably the tip that is out. I will report back tomorrow.

 

The answer to your question, Jonathan is no. There is nothing about differential. In fact there is not much about anything in the manual!! All it says for the ailerons is 20mm +/- which clearly ignores the need for differential. What a novice would make of it I don't know.

Furthermore, there is nothing about flaperons/flaps at all. It conveniently ignores the whole issue. The implication appears to be that the owner knows all about it ..... I do think the glider is meant to be something that resembles a scale subject, however!

It's interesting what you say about the travel on crow brakes. Clearly I need to reduce the EPA from where I arbitrarily put on the flaps this afternoon.  I can easily mix in some down elevator at the outset to counter the effect of the nose pitching up. There is the TX facility to do this on a "curve". Thanks for all your other info by the way.  

 

 

[Adrian Smith 1]

 

Interesting clip of the same glider as mine. Seems to use a lot of throttle though!

 

https://www.youtube.com/watch?v=ucnYv2zqPUk

[Jonathan M]

In which case 50% differential as you've done is a good starting-point! ?