Coming back after 50 years: bit lost

[David Davis]

The yellow model seems to be a Peter Russell STOL but a 42 inch wingspan seems to be a bit short. Peter designed three wings for the STOL: the original if I remember correctly had a 48 inch wingspan; the Mark 2, which incorporated flaps, ailerons and slats had a 55 inch wingspan, and Peter also designed a simple "Trainer Wing" with more dihedral so that the model could be flown as a three channel trainer. It would appear that this is the version that Hillclimber has, though perhaps someone has produced a smaller version of the original.

I have no qualms about a sixty-something novice learning to fly on a vintage model. I myself learnt on a Junior 60 but I was rather younger when I started flying r/c! Vintage models are nice and stable and will sort themselves out if the novice loses control providing that the model has sufficient height to recover. Just cut the throttle and take your hands off the sticks and given sufficient height it will sort itself out. It's true that a beginner would have some difficulty flying one in a wind but absolute beginners should not fly in anything much stronger than a Force 2 in my opinion.

However, I have a few qualms about both of your models as basic trainers Hillclimber. The Super Scorpion is a bit too pretty and the STOL at only 42 inches in the wingspan is too small and may prove to be difficult to see. If you want to start on a vintage model I would recommend that you buy a Ben Buckle Super 60 or Radio Queen kit. The Super 60 has probably taught more British aeromodellers to fly than any other and is quite happy in a bit of a breeze once you've gained some experience. The Super 60 has a five foot wingspan and is pretty tough. The Radio Queen has a seven foot span and is easy to see at that size. Pictures of my specimens blow. One sold, one crashed when I flew across the disc of the sun and became disorientated. Lesson learned.

Having said all that if you join a club and get an experienced instructor to take you up on linked transmitters so that he can take over control at any time, the so-called buddy box, then a four channel ARTF trainer comes into the reckoning. My personal favourite is the Seagull "Boomerang." I'm just finishing one off at the moment. I am the unofficial deputy chief flying instructor in my club and I'm assembling the Boomerang as a reserve trainer. Its semi-symmetrical wingspan will enable it to fly in a breeze and to perform aerobatics which other trainers won't allow you to do, not that you'll be doing any aerobatics at first. It comes with all of the parts you will need to finish the model for either electric or i/c power. Steve Webb is quoting the Boomerang at less than £100 and you can even buy a builder's kit of the same model. Mind you the price is the same! Other suppliers are available.

OK, just my two pennorth!

Edited By David Davis on 05/01/2018 11:19:16

Edited By David Davis on 05/01/2018 11:20:47

Edited By David Davis on 05/01/2018 11:22:18

[Piers Bowlan]

A model weighing 2lbs 12oz should fly well on 200W with 16.4oz/squ.ft wing loading. I would not be surprised if the electric setup is a bit lighter than the Enya too. The ESC is of course the Electronic Speed Controller which not only controls the motor RPM but also includes a BEC (battery eliminator circuit) so that your battery also supplies power to your receiver (Rx). I believe the ESC is working hardest at mid throttle positions.

Additionally the ESC, has a PCO (power cut off) which cuts power to the motor when the battery drops to appx. 3.2v per cell. This is not only to maintain power to your Rx but also to protect the LiPo from being over discharged. Should the voltage in any cell drop below 3v then it will be permanent damaged and probably it will not be possible to recharge it. Usually people land before the PCO cuts in, and for the longevity of the battery it is probably best to land with 30% of the charge remaining. This is all a matter of personal choice. If you wish you can disable the BEC and use a small additional battery (usually a 4cell NiMH 4.8v) to power the receiver if the extra weight is not an issue. The internal ESC BEC usually is limited to 3A which is enough to power the receiver and three or four small servo. For larger models with digital power hungry servos another Rx battery or alternatively an external BEC, called a UBEC, is often connected to the power battery. If the ESC overheats in flight and fails, the internal BEC will fail also, resulting in the receiver to stop working and resultant loss of control. Provided the ESC is adequate (i.e. 20A current draw/30A rated ESC) and there is sufficient cooling to motor and ESC, all should be well!

[Simon Chaddock]

Hillclimber

The big benefit of an electric motor is it can be fully throttled from zero to 100%. in flight. as many times as you like and can be run continuously at any level in between.

They do require some cooling air but as their net efficiency in converting energy into power is much higher than IC their cooling requirement are rather less.

On the other side of the equation is the associated electronic speed controller (ESC). This has to handle the same power as the motor and although efficient it does generate some heat and needs a proper supply of cooling air too and even the battery gets warm.

Just remember on the electrical side of a brushless motor set up there are no moving parts so it will either work or it won't and electronics are very reliable provided the electrical load is kept within their specification.

These characteristics not to everyone liking!

[Rick Tee]

I agree with David Davis, for my two penny's worth I'd go further and suggest your best bet is to buy a Boomerang artf and an SC46 or ASP46 engine. An IC engine with a 10oz tank will give you 15mins - 20mins of flying. Allowing your instructor to take off, trim, hand over, giving you at least 10mins on the sticks with plenty left for landing. Also as soon as your instructor is available again you only need to re-fuel and go. With electric you'll need 3 batteries to maximise your time flying rather then waiting for batteries to charge. You'll get 7mins - 8mins flying time, once your instructor has taken off and allowing time for him to land it for you, you'll be lucky to get 5 mins on the sticks. Add to that very light models require very little wind, waiting weeks for the right conditions will drastically reduce the rate at which you learn.

I've been a club instructor for 10 years+, people who learn quickly do so by flying 4 - 6 times each visit, visit often and use a good sim (preferably not Phoenix).

My advice is to visit the club before you buy anything.

Edited By Rick Tee on 05/01/2018 14:09:42

Edited By Rick Tee on 05/01/2018 14:13:47

[911hillclimber]

This is a great forum!

Committed now, all parts except the servos on order.

As to the servos, I bought a futaba set about 15 years ago (for the Scorpion) and the servos from that set are in the Stol. # FP-S148, direct drive. The Futaba is a 35mHz (crystal?).

Will these old but new servos be compatible with the Spektrum DX6 I have which is 3 years old?

[David Davis]

You will need to cut off the little tags on the side of the Futaba servo plugs to get them to fit a Spektrum receiver, or any body else's receiver for that matter. These tags are there to prevent you from inadvertantly fitting them the wrong way round in a Futaba receiver. You may also need to taper the leading edge of the plugs with a file or some sandpaper. Having done that they should fit.

Let us know how you get on. I promise not to say, "I told you so!"

[911hillclimber]

Progress needs to be on my head, so going with what I have and have ordered.

If all fails this (electric conversion) has cost me £100, and I can always convert back to the Enya or PAW diesel as I have them. That will fix the time-in-the-sky, the weather will be much harder, but as I'm retired now I hope to have a bestter choice.

The local flying club bans IC on a Friday and Wednesday I think, electric is 7 days a week.

I appreciate I'm coming back to the hobby in an awkward way governed by using what I have, but challenges are good...

Most parts ordered this morning are in the post from UK sources, so should be much advanced by end of next week. I'll detail the installation, but going for 3 deg down thrust and 3 off-set.

Still not sure of the CofG position as I do not have the plans for the Stol, any suggestions please?

[David Davis]

My STOL Mk 2 plan has a wingspan of 55", a chord of 8.5" and the c/g range of between 2.5" and 3.5."

If yours balances on the main spar that should be alright.

[911hillclimber]

Thank you David.

This Stol has a chord of 9" and the spar is 4" back from the LEdge.

There are 2 marks on the cabin top, 2.25" and 3.25", maybe these are this model's C 0f G range. At least I know where to place the parts to get close without ballast.

EDIT: Just found the plans on the internet, the marks on the cabin are the C of G range. Nice to have a classic plane, my main interest is Classic cars, so fitting.

Here is the current RC layout, currently all Futaba parts, batteries and Rx will go for the new parts, be nice to use the elevator/rudder servos I put in 15 years ago. I'll see if your mod to the connectors can work for me.

 

Edited By 911hillclimber on 05/01/2018 16:28:55

Edited By 911hillclimber on 05/01/2018 16:29:33

Edited By 911hillclimber on 05/01/2018 16:47:09

Edited By 911hillclimber on 05/01/2018 16:56:56

[john stones 1 - Moderator]

Lot off what's being said is good advice 911, you go your own way though, once you get going options and problems encountered may change your thinking, but enjoy the journey.

[911hillclimber]

Hope I will John!

As I say, if all fails I can revert the model to IC. The engine is mounted on a bolt-on nylon moulded bearer.

If the plane is far to tricky and my enthusiasm is still with me then I'll plump for a Junior 60, just hope I don't loose the motivation too quickly! I'm not known for giving up, my job needed a lot of determination...

I don't like the look of modern RC trainers, so this route will be a bit rocky come spring.

 

Sorry for the million questions, but the Stol design has the wheel 'axis' just behind the LE of the wing. This looks too far back to me and I've reversed it so the wheels are directly under the front bulk head, about 7" forward of the plan design. Obviously moves the C of G forward, but if the position of the CofG is restored to the design's range it should fly ok /take off and land ok?

Edited By 911hillclimber on 05/01/2018 17:07:25

[Denis Watkins]

Am following your journey 911

Wheels on, or just in front of the leading edge is fine for take off and ground handling

[911hillclimber]

Thanks Dennis.

Should get the parts on Monday and the prop turning by end of the week.

[Jonathan M]

Posted by Rick Tee on 05/01/2018 14:08:02:

I agree with David Davis, for my two penny's worth I'd go further and suggest your best bet is to buy a Boomerang artf and an SC46 or ASP46 engine. An IC engine with a 10oz tank will give you 15mins - 20mins of flying. Allowing your instructor to take off, trim, hand over, giving you at least 10mins on the sticks with plenty left for landing. Also as soon as your instructor is available again you only need to re-fuel and go. With electric you'll need 3 batteries to maximise your time flying rather then waiting for batteries to charge. You'll get 7mins - 8mins flying time, once your instructor has taken off and allowing time for him to land it for you, you'll be lucky to get 5 mins on the sticks. Add to that very light models require very little wind, waiting weeks for the right conditions will drastically reduce the rate at which you learn.

I've been a club instructor for 10 years+, people who learn quickly do so by flying 4 - 6 times each visit, visit often and use a good sim (preferably not Phoenix).

My advice is to visit the club before you buy anything.

I completely agree with this - having the learnt the hard way! This isn't to criticise the OP's heart, and I know lots of clubs have IC restrictions, but I struggled to make progress for a long time with an electric trainer, even though it was a modern four channel model (but also foam, which I found to be too lightly loaded for these windy isles). I now reckon I'd have been much better off and learnt to fly more quickly with fewer bad habits with a proper, heavier IC trainer with longer and less rushed flight times.

But electric does have the advantage of not having to faff around with IC motors, so the student can concentrate more fully on the flying side of things. Just make sure you have lots of fully-charged Lipo batteries, 3 minimum but 4 or 5 better. I had three, but used to charge each depleted one with a 12v battery in the pits while flying with the next one - or just resting and watching others fly!

[David Davis]

Hillclimber, if you join a club, you may find that the club has its own trainer so that you can learn to fly without risking your own models. My club, admittedly in the middle of France, has three or four i/c trainers, an electric-powered trainer and a Radian three channel electric-powered foamy glider.

Beginners can use any of these models on a buddy box.

[cymaz]

+1 ...Any club should welcome you, show you around, introduce you to other club members and offer you a go on the club trainer...we do here in Cornwall. If they don’t,move on and find one that does. IMO that’s the best way to make possible memebers at ease and Interested in joining.

[Trevor Crook]

You should be fine with your electric set-up. These models will have a similar weight with electric power to their i/c equivalents, so should fly in a similar fashion. Duration should be adequate as you will be using little power.

[911hillclimber]

Again, thank you all. I'm impressed at all the sound advice from everyone as you are all experienced and I am not.

I have embarked on this little project as winter is a time for such things, but I think I will be done way before the weather starts to get better, but then that is time to find the local club and see if I can get some training in before wheeling out this plane!

My very first thought (knowing nothing) was to revive the Scorpion, cover it, transfer the radio from the Stol and pop to the flying field and take it from there, what could go wrong?

Well that plan did not happen.

I'll carry on and see what confronts me in the late Spring and re-visit the local club to see about trainers. I didn't know clubs had trainers sometimes and buddy boxes. From my other pursuits I know there will always be someone else there to help and advise.

[David Davis]

This should help you locate the clubs which are nearest to you. **LINK**

Not all clubs have their own trainers.

[Piers Bowlan]

Hillclimber, using the servos you have makes a lot of sense especially as the Futaba 148s are a traditional 'cooking' servo, sold in their millions. If you get into the hobby saving weight can become something of an obsession, at least it is with me! A couple of 148s weigh 89g whilst a couple of Corona 939s weigh 24g. So you could have a 65g larger battery whilst not increasing the AUW. The 148s on the other hand would be ideal for the Super Scorpion.

As you have sorted the C of G and mindful of the motor down thrust/side thrust as per plan, what can possibly go wrong? Just research the control deflections and take advantage of the rate switches on your transmitter and use a bit of exponential. Other than that I think it will be a pussycat to fly in the right conditions. A calm Summer's evening would be perfect. Roll on Summer!

[911hillclimber]

Thanks as ever! Hard to keep up with you lot!

I am now feeling a lot less 'lost' as a direct result of all the positive help, most excellent gents.

The motor and ESC and prop arrived today all off ebay and separate suppliers for the $/£ equivalent of using Asia.

The motor is small in comparison but that makes it much easier to slot into the existing Stol cowl. From what I've noticed on the endless YouTube vids I've watched, I will locate the ESC under the motor on the deep bulkhead in the cooling air stream and the battery just inside the cabin, again for cooling and easy change.

The Futaba servo's seem really robust to me being a much older design and are of course in the plane already . I'll pull the IC motor servo out which sits right under the C0fG position so that should not affect things.

Chasing down weight affects my other interests so fully understand the 'passion' for that goal, but at a FAR greater cost.

This aero modelling lark sure is cheap by comparison.....

I noticed in a recent RCME that there is an idea to mount the motor on 4 lengths of allthread, say M4, and to allow adjustment by moving the 4 motor-end nuts and washers to dial in the angles, seems a good way forward if a little crude.

Why do electric motors need so much down thrust? I understand the side, but not really the down thrust 3 degs.

[Piers Bowlan]

Posted by 911hillclimber on 06/01/2018 12:02:53:

Why do electric motors need so much down thrust? I understand the side, but not really the down thrust 3 degs.

In producing lift the wing will also produce drag (you don't get something for nothing in this life!). Thrust opposes drag but as the centre of thrust is below the centre of drag the resulting couple causes the model aircraft to pitch up (full sized does too) with the application of full power. A few degrees down thrust will tend to counteract this characteristic. I say tend, because the relationship is not linear but at least it gets you in the right ball park. Whether and how much a model will pitch up with power will depend on several factors but suffice to say on vintage models I suggest that down thrust will dampen the models enthusiasm for ballooning straight up into the air after you launch it (even if the C of G is in the correct place). Alternatively you could program your transmitter to apply some down elevator with throttle (mix) or a bit of both, as I have done on one or two of my e-gliders. There is a thread about the merits of engine side-thrust and down-thrust here.

Edited By Piers Bowlan on 06/01/2018 14:22:01

[Trevor Crook]

All I would add to Piers' comprehensive explanation, in response to the original question, is that the same downthrust would be required if an i.c. engine were fitted.

[911hillclimber]

Right, that even made sense to me, just 3 deg seems a lot.

Some youtube vids show some vintage planes once off the ground (just) going up like a Harrier and nearly stalling! Guess this is why.

Braved the local model shop this afternoon, quite an intimidating place, everyone stares at you...

Got served by the 11 year old, but got there in the end.

Should get the motor and things in place tomorrow, but not worked out how to dowl the main wing to the fuselage.

A solid connection seems like a disaster to the frame on a hard landing where the 'bands-only' clamping would be more forgiving?

The plans have no dowls, just a step of about 1/4" for the wing to come up to by virtue of the bands. This is not enough, the wing LE rides over it very easily.

The location is not very positive, so my thoughts are to have 2 vertical dowls in the corner of the front of the cabin, 10mm long so the wing registers against them but not dowls through the wing.

[Denis Watkins]

Just thoughts 911, nothing is written in stone in this game

Only my micros have down and side thrust, everything over 40" span is zero, just straight line thrust.

6mm dowel will hold most wings up to 60"

Have the U/C removable yes, but solid enough not to fold under and go through your wings

Keep going