SAFE may be better than I thought

[paul devereux]

I have said I have very limited experience of SAFE, but what I had experienced I didn't like. I have a HZ Champ (I mistakenly called it a Cub) and found it almost impossible to fly with SAFE, and a handful without it. A couple of days ago I went to our local rec where people fly their little Eachine 400 mm warbirds. One saw the Champ in the air, thought it looked tail heavy, and suggested taping a pebble to the nose to see if it helped (pebble is pictured). It transformed its flight. I've since replaced the pebble with a more aerodynamic penny. Now that the model flies straight and true, SAFE is no longer a liability. Not that I use it anyway.

I am surprised it came out of the box tail heavy. I thought they were designed down to the merest detail. And I hadn't read the manual so I didn't see the recommended CoG even if it was in it. It just goes to show.

[leccyflyer]

Have you now checked that the CG is correct, as stated in the manual?

[Wookman]

It goes to show that no amount of clever tech will cure anything that is fundementally wrong

[Ron Gray]

A lesson learnt, never assume that just because it came 'ready to fly' that it is, always check CG and control movements before flying!

[PeterF]

But unless the manufacturer actually fits the battery, which I have never seen how can a model like that definitely have the right CoG. The actual CoG will be affected by user battery choice and location,  different makes have different weights and dimensions for the same capacity so it always needs checking.

[Peter Jenkins]

The C of G position is the single most powerful trimming tool available to us.  It is not a fixed position, as has been pointed out, but can be varied to either increase stability or reduce stability.  You should not be afraid of experimenting with moving the CG a little bit to see how it affects the model's performance and how it feels to you the pilot.

 

Stick on weights (5 g and 10 g are good ways to test out CG changes.

[paul devereux]

4 hours ago, leccyflyer said:

Have you now checked that the CG is correct, as stated in the manual?

I can't check the manual as I threw it away with the box. But I usually balance a model on my fingers, between 25-30% back is good for a first flight, I reckon (I'm drawing on 50-year-old memories of aeromodelling as a child). I assumed because it is so small and light it wouldn't be critical. It now balances on the one and only spar. But it now flies where I point it and flies level hands off, which is the main thing.

[leccyflyer]

Here's the manual

 

https://www.horizonhobby.com/on/demandware.static/-/Sites-horizon-master/default/dwc0c65b8e/Manuals/HBZ4900-Manual.pdf

 

CG should be 28mm from the leading edge of the wing.

 

Good to hear that the model is now flying as it should do.

[Nigel Heather]

It’s decades since I last flew IC fixed-wing so I can’t recall what it was like but it does make me wonder these days.

 

With an IC fixed wing, you have 100s grams of fuel in the nose at the start of the flight and tending towards 0g when you land.  The CoG must move backwards quite significantly with the plane becoming more lively as you fly.

 

I don’t recall this ever being a problem, but as we didn’t know anything different, had no real option but IC and no electronic helping aids, maybe we just accepted it as normal and our brains just adapted and got on with it.

 

Cheers

 

Nigel

[leccyflyer]

Thing is that you usually balance the model empty, with no fuel in the tank, so at the start of the flight you will be a little nose heavy, but during the flight the CG will migrate back a little.  I've often thought that with twist and turn retracts that you should balance the model with the wheels up, as you are moving some weight behind the CG when you put the gear up. That will tend to move the CG forwards just a little when you come to land.

 

Looking at the Hobbyzone Champ manual, it's a small 1s model, with a small 150mah single cell battery fitted. It would certainly be worth investigating whether a larger 1s battery would fit, giving longer flight times and being able to lose the ballast that was added.

[Nigel Heather]

29 minutes ago, leccyflyer said:

Thing is that you usually balance the model empty, with no fuel in the tank, so at the start of the flight you will be a little nose heavy, but during the flight the CG will migrate back a little. 

That's true, because a nose heavy plane is 'safer' than a tail heavy plane.

 

The other thing I recall (and miss to be honest), reminded as I have recently dusted out a now unused IC plane to put on the classifieds.  It is just a standard 'second plane' high wing but I struck by several things

 

1) how nice it looks with its wood and film construction

2) how big it is - 60" wingspan was the typical size for beginners

3) how heavy it is compared with whatI fly these days

 

To be honest,I miss that size and weight, so much easier to see, so much more robust on landing, and stable in moderate winds and gusts that keep my foamies grounded.  I seriously considering keeping it and flying it.

 

Don't miss the fiddling with IC engines and cleaning up the mess afterwards though.

 

I would like an electric plane that size but I shudder to think what the specification and cost of the power train and batteries needed.

[Frank Skilbeck]

1 minute ago, Nigel Heather said:

 

 

I would like an electric plane that size but I shudder to think what the specification and cost of the power train and batteries needed.

Yep, at our club we have recently seen some 6s lipo models converted to IC.

[Nigel Heather]

42 minutes ago, Frank Skilbeck said:

Yep, at our club we have recently seen some 6s lipo models converted to IC.

Doesn't surprise me - those batteries must be pushing £100 each these days.  On top of that you need to consider replacing them every 2-3 years.

 

Wouldn't mind if that was getting you something special but you practically need that sort of thing for a 60" sports plane that we used to throw around the sky with a 45 IC engine. 

[leccyflyer]

7 minutes ago, Nigel Heather said:

Doesn't surprise me - those batteries must be pushing £100 each these days.  On top of that you need to consider replacing them every 2-3 years.

 

Wouldn't mind if that was getting you something special but you practically need that sort of thing for a 60" sports plane that we used to throw around the sky with a 45 IC engine. 

You mean as opposed to the multiple gallons of fuel @ £20-25 a gallon that you would get through in those two-three years? 

 

If you look after your packs by a few simple means they will certainly last longer than 2-3 years , plus perfectly good battery packs are around 50-60% of that £100 cost that you mention - £117 for two HRB 6s1p 4000mah 60C packs on Amazon this morning.

[Ron Gray]

1 hour ago, leccyflyer said:

you should balance the model with the wheels up

I always do CG checks with wheels up, after all the model is going to spend most of its flying time in that configuration.

1 hour ago, Nigel Heather said:

Don't miss the fiddling with IC engines

Once correctly setup then very little adjustments should be required. But it is that initial setup that is crucial, get that wrong and you will be fiddling.

1 hour ago, Nigel Heather said:

I shudder to think what the specification and cost of the power train and batteries needed.

Obviously depends on model but I’ve recently carried out some cost comparisons between electric and IC (Lasers in my case) and over a 5 year period there isn’t a lot of difference.

1 hour ago, Nigel Heather said:

cleaning up the mess afterwards

Get a Laser running low oil and the mess at the end of the day is minimal.

19 minutes ago, Nigel Heather said:

those batteries must be pushing £100 each these days

I’ve just bought a 6s 5200 from Amazon which cost £75. A couple of months ago I bought the same capacity battery from China Hobby Line for £57 but they haven’t been in stock since!

Edited June 14, 2023 by Ron Gray

[Peter Jenkins]

Most "proper" aerobatic IC aircraft have their tanks mounted on the CG but that needs the engine to have a pumped supply.  That's easy enough to do even if you have to buy a pump as you "just" need to drill and tap the engine backplate to get the compression pulses needed to work the pump.

 

Absolutely agree with Ron that once set up it's just a case of fill up, prime and away she goes!  May need to tweak the slow running needle for extremes of weather but that's it.

 

Oh, on cost comparisons, I found that I was spending £3 per flight for IC engined aerobatic aircraft (Saito 180 in Capiche 140) but I get to £1 per flight for the equivalent electric that uses 10S (2 x 5S packs in series) provided I got 100 flights out of the pack.  After the 100 flights the cost per flight drops.  I have also found that budget packs will die before more expensive packs - there are exceptions to that rule of course!  OK, I've not included the cost of the chargers in that calculation or the cost of charging but the electricity used is miniscule in comparison with your normal bill.  The cost of a decent charger and power supply is probably around £300-£400.  If I spread that cost over 2,000 flights I've conducted since I got the chargers then you add around 20p per flight.  If I say I have 2 such setups that takes me to 40 p per flight - so a total of less that £1.40 per flight compared with the £3 per flight for the IC setup.  The 2 charging setups allow me to charge 4 flight packs as 2 x 5S  in parallel in an hour.

 

I have a couple of Turnigy packs that have done well over 100 cycles and are still going strong but I no longer use them for competition.  Some died at around 50 cycles and I have a Vant pack that died after 4 cycles albeit I bought that one second hand but unused.  I'm currently using ONBO packs and they seem to be lasting well but the lead pack has only just passed 50 cycles.  However, internal resistance and cell voltage balance is still excellent with no puffing whatsoever.

Edited June 14, 2023 by Peter Jenkins
Cost of chargers added.

[paul devereux]

4 hours ago, leccyflyer said:

Here's the manual

 

https://www.horizonhobby.com/on/demandware.static/-/Sites-horizon-master/default/dwc0c65b8e/Manuals/HBZ4900-Manual.pdf

 

CG should be 28mm from the leading edge of the wing.

 

Good to hear that the model is now flying as it should do.

Well, you could knock me down with a feather! The CG is spot on now, it was over a quarter inch out previously. No wonder it was a pig to fly- I did wonder why it was recommended for beginners. And why SAFE made it worse. (I didn't realise the Tx had D/R either- it is quite sophisticated for a little model). I wonder why the manual didn't stress the CG stuff a bit more, I was using it straight out the box, so their QR should have told them it was variable? Not that I would have read the manual, of course, but some people might.

[GrumpyGnome]

Lesson learnt - hopefully. 

 

Always read the manual for key things like balance point, throws.  It also pays to do a quick internet search as some of these details are way out...

 

If you were in a club, your instructor/flying chums would have helped you with this prior to the first flight. 

 

I suspect a large number of people just take these out of the box and try to fly them without reading the manual for anything but basics....... e.g 'this stick moves this piece of the aeroplane'

[Cuban8]

On 14/06/2023 at 07:01, Nigel Heather said:

That's true, because a nose heavy plane is 'safer' than a tail heavy plane.

 

The other thing I recall (and miss to be honest), reminded as I have recently dusted out a now unused IC plane to put on the classifieds.  It is just a standard 'second plane' high wing but I struck by several things

 

1) how nice it looks with its wood and film construction

2) how big it is - 60" wingspan was the typical size for beginners

3) how heavy it is compared with whatI fly these days

 

To be honest,I miss that size and weight, so much easier to see, so much more robust on landing, and stable in moderate winds and gusts that keep my foamies grounded.  I seriously considering keeping it and flying it.

 

Don't miss the fiddling with IC engines and cleaning up the mess afterwards though.

 

I would like an electric plane that size but I shudder to think what the specification and cost of the power train and batteries needed.

My first proper power trainer back in the 80s was a 60" four channel Hi-Boy with OS 40. Certainly no lightweight but it flew well in most conditions and given its far from low wing loading, had to be landed properly. No dragging it in under power as you can get away with, with some featherlight foamies now. Not a difficult or bad model as some label it, but a model that was intolerant of mis-handling. To be fair, I had already flown gliders both on the flat and slope for a number of years , so wasn't a total novice. Still was a new skillset to master though at the time.  If you have a similar type of model - hang on to it!

Although the cost of electric power trains have become considerably more expensive compared to several years ago - and like them or loath them, Hobbyking's demise as a source of cheap batteries and kit, I don't believe the cost of electrifying a larger type of sport model is so out of the question, providing one shops around and sticks to models designed originally for say .40 to .46 two strokes or thereabouts.

Properly installed and set up, IC engines shouldn't need fiddling with and although not totally free of 'mess', modern lower oil content fuels using synthetics only are vastly superior to the 'orrible sticky mess that we endured with castor based stuff.

Edited June 16, 2023 by Cuban8

[Martin Harris - Moderator]

I’d like to see manufacturers specify wheels up or down during measurement but we need to remember that the C of G is really a range which gives acceptable elevator control authority and the point shown in most instructions/plans is a starting point for individual preference and usually on the safe side. 
 

Full size are always measured wheels down due to the practicality of taking weight measurements for calculations due to the general unavailability of giant fingertips! 
 

If in doubt, err on the safe side for the first flight - there’s nothing truer than the old saying that a nose heavy aircraft flies badly but a tail heavy one usually flies just once…

[Nigel Heather]

23 hours ago, Cuban8 said:

My first proper power trainer back in the 80s was a 60" four channel Hi-Boy with OS 40. Certainly no lightweight but it flew well in most conditions and given its far from low wing loading, had to be landed properly. No dragging it in under power as you can get away with, with some featherlight foamies now. Not a difficult or bad model as some label it, but a model that was intolerant of mis-handling. To be fair, I had already flown gliders both on the flat and slope for a number of years , so wasn't a total novice. Still was a new skillset to master though at the time.  If you have a similar type of model - hang on to it!

Although the cost of electric power trains have become considerably more expensive compared to several years ago - and like them or loath them, Hobbyking's demise as a source of cheap batteries and kit, I don't believe the cost of electrifying a larger type of sport model is so out of the question, providing one shops around and sticks to models designed originally for say .40 to .46 two strokes or thereabouts.

Properly installed and set up, IC engines shouldn't need fiddling with and although not totally free of 'mess', modern lower oil content fuels using synthetics only are vastly superior to the 'orrible sticky mess that we endured with castor based stuff.

My mate had a Hi-Boy, I had a Yamamoto.  With hindsight I did everything wrong by following ‘sound advice’ in magazines and the ‘guy in the LHS’.  I went for three channel (no ailerons, huge dihedral) - at the time the ‘sage advice’ was that beginners couldn’t handle ailerons, they should start on 3 channel and then buy the aileron wing when they were more confident - fortunately buying another wing and the fibre glass joining kit and the covering was not the extortionate price it would be today.  The other thing I did was to buy a 35 engine, not a 40, not a 45/46 (though not sure the 45/46 existed back then), a nice little OS 35 FP - the ‘sage advice’ at the time was that beginners could not handle the enormous power of a 40 and should buy a 35 and upgrade later.  The 35 worked fine in my Yamamoto but I quickly found that every option for ‘next plane’ demanded a 40 as a minimum.

 

But that aside my Yamamoto was a lovely plane, and I remember it being robust - in fact, despite lots of hard arrivals nothing was bad enough to confine it to the bin bag - it got patched up several times but it lasted a lot longer then any of the foamies I’ve had since.

 

Still have that OS 35 FP - I’m sure it still runs fine.
 

Cheers,

 

Nigel

[Tom Gaskin 1]

In the days before buddy-boxes & auto stabilization the three channel trainer was the preferred ab initio model. In the early '70's I learnt to fly on an Enya 09 powered 3 channel Keil Kraft Outlaw.

 

When buddy-boxes became available the higher powered 4 channel model became a far more practical trainer.

 

Tom

[Cuban8]

Cost was also a very significant factor affecting one's choice. Larger size engines and 'full house' radios were eye wateringly expensive for many people and usually out of the question for a youngster to get his hands on as well. As a kid in the 60s I used to dream of owning one of the blue Macgregor outfits that were displayed in all their glory, from a single channel unit up to a five, or was it a six channel kit in a local model shop's window. A friend gave me a single channel Macgregor tranny a while ago - so I did get one in the end although fifty years too late. Have it in my workshop, and it still gives me pleasure just to look at it now.

The three channel is best argument is also probably a  throw back to the old free flight power and single channel days - as Tom says, with the advent of cheaper and better equipment, four channel models became much more common and the old single speed, highly stable trainer models gradually faded away. Not totally redundant though, depending on what one is trying to achieve, I suppose.

Not many affordable  radios did have 'buddy boxes' so the old 'grab the box' method did carry on for ages until cheaper Japanese makes included them as standard.

As for good advice........we had a local model shop owner who gave our club no end of headaches. He'd sell an unsuspecting beginner a bunch of kit as 'the perfect beginner's outfit' but was really only what he couldn't sell and was happy to clear off his shelves, before pointing said tyro in the direction of our club.

I remember having an argument with him over a second hand engine that he'd sold a new chap, and that was, to me, only fit for a door stop. He eventually relented and took the motor back when the newbie said he'd buy a new OS 40 or whatever it was, from him. Was glad when he eventually closed up shop.

Mention of the MFA Yamamoto got me thinking. Firstly, a curious name to choose, being that of a notorious WW2 Japanese Admiral and secondly, I remember it as being a very popular trainer (a favourite with our model shop owning friend) but a model with a bite in the hands of a beginner. The old Hi-Boy would complain if flown a bit too slow, but the Yammy would flick on you if you weren't careful. I think they did a fibreglass fuz version that was particularly prone to being a bit hairy. All a long time ago.

Edited June 17, 2023 by Cuban8

[Simon Burch 1]

Looking back at the title of this thread, I'd be interested in other forum members' views on SAFE-type systems.  

 

Personally, I think that they have a part to play in helping to introduce people to model flying, and their increasing confidence during the early stages. However, at some point, trainees will need to be weaned off stabilisation to prepare for an A Test.  In doing so, I've found that flying an unmodified SAFE-fitted aircraft in 'expert' mode can be more difficult than it needs to be, which risks demoralising the trainee and making life harder for the instructor.

 

Last year, I was with a club member who was working towards his 'A' Certificate.  He was flying his SAFE-fitted E-Flite Apprentice quite well in 'beginner' mode, and he asked me to demonstrate the figure-of-eight manoeuvre.  We weren't using a buddy-box, so I flew the manoeuvre using his TX.

 

I found that, in 'beginner' mode, SAFE stabilised the model so well that I felt it interfered with control inputs too much.  In 'intermediate' mode it was better, but still not ideal, so I switched to 'expert' mode. With no stabilisation, the model was extremely sensitive in pitch and roll.  To me, was surprisingly difficult to fly, and it would certainly have been a challenge for a beginner.

 

The Apprentice is a traditional high-wing trainer which, judging by its appearance, should have had benign handling characteristics with or without SAFE.  However, its aileron and elevator control throws were, to my eyes, unusually large, and no rates or expo were set for fully manual flight.  With SAFE selected ON, this wasn't a problem because the stabiliser was helping to maintain the model's attitude but, in manual control, the model was an unexpected handful to fly.

 

Eventually, we adjusted the Apprentice to fly nicely in full manual control by adjusting rates and expo.

 

I wondered whether large control throws are deliberately set by the manufacturer to enable rapid recovery from an 'unusual attitude' when the panic button is pressed.  I also notice that some of these systems feature automatic aerobatic manoeuvres which, presumably, require larger control throws on trainer types.  If this is the case, the model's handling in 'expert' mode (ie fully manual) is likely to be compromised.

 

Finally, I think that flying a model with an autostabiliser requires a subtly different handling technique, because the system masks some control effects.  For example, a turn may be achieved by using aileron alone; the stabiliser introduces 'up elevator' for you as the model tries to maintain pitch attitude.  Normally that's not a problem, but I think it impacts upon the model's suitability as a trainer.

 

Many of our new members are turning up with small to medium sized RTF or AFTF autostabilised models.  Some have a pre-programmable flight path control system.  Whether we like it or not, SAFE-type systems are becoming ubiquitous, and RTF model flying controls are likely to be set up primarily to suit the system's needs.  This will affect the way that we use these models for training, and, as such, we'll need to work out the most effective way to get the best out of them.

 

Any comments or thoughts welcome.

[Colin Carpenter]

Test flew club mates Spit with SAFE . It flew so far away that I thought it would never turn , even with full rudder. Got it down and the owner threw away the Rx. Not for me after that but AS3X is excellent! Colin