Sloping Off - September 2006

The X-Twins
Toys with Potential

by Mike Roach (and others)

A few months ago I took one of those little Aero-X free-flight toy planes to pieces and had a lot of fun making a Depron Spitfire from the bits.  At about the same time the X-Twin came out and one was flown at Calshot for much of the indoor season.  Then Tony Dowdeswell sent me a box of five X-Twins with the comment “have some more fun”.  You can get them at Lesro Models, price £24.99 and I expect they are available at most model and toy shops.

X-Twins are distributed by Flying Toys Ltd and they can be contacted at www.flyingtoys.co.uk or at Unit 9 The Vanguards, Vanguard Way, Shoeburyness SS3 9OJ.  Their glossy catalogue lists hosts of flying toys.  I particularly liked the look of the ducted fan A6 Intruder, but they also do blimps, helicopter, kites, rockets and a cool-looking hydroplane.  The X-Twins come in a variety of interesting shapes, all with the same hardware.  You get:

• A 27 MHx 2-channel Tx complete with battery charger.  The left stick controls proportional throttle, the right stick is just a switch which increases the speed of the “outside” motor to control direction. There are 3 channel options so combat or formation flying is possible.
• An  “unbreakable” model made from Elapor or something similar, with twin pusher electric motors and 2 spare props.  (Why 2 props? All will be revealed).
• A very neat Rx incorporating a speed controller, on/off switch and charging socket.

I divided the models between a couple of lads from my sailing club who have never flown an RC model, my engineering son Jon who has watched my efforts but never flown RC, Trevor Hewson who has definitely flown RC and myself.  Here’s what they say.

Jim Sowden (11)
When I saw the single winged I thought it would work better but get damaged more than the biplane because the biplanes propellers never touch the ground. I got the plane straight out of the box and read the instructions. It was very easy to understand so I got the knack of flying it straight away on my first go. I thought the charging was good and easy. The wind was weak but there still was wind on my first go. It was hard to control with a little bit of wind, but I think it was because I was not very good. The lever to go forwards is sprung so I thought that was good but it probably is better without that spring. I think this because then when you get it flying properly you can hold it there easily. A very good point about the plane is that it is unbreakable so if you crash it down too hard it will not break. With the plane you can’t do any tricks like loops it is not bad just it would be good if it could. I think that this plane is great for all ages and is very fun. I enjoyed playing with it and I think it is a superb little plane. Overall I think it is great and is better in lighter winds than stronger winds.

IT IS GREAT!!!

Dan Sowden (13)
When I first saw the box of the plane I was very impressed and I straight away opened it up.  Next I read it and I thought it was really good so straight away I got some batteries to charge it up. I only charged it for a little time so when I flew it, it didn’t last very long. There was a little breeze so it didn’t fly perfectly. It needed a weight on the front. I used a 1 cent coin which worked really well as it stopped it stalling too much. It was really easy to fly although the biplane looked easier as it just went up and up. I could never get it to fly straight but I think it was due to the wind. On a day with little breeze it flies well but once it started turning I could get it to turn for a long time and once it did turn it turned far too much. Once it started spiralling it just went down and down. I tried it again on a day with no wind and although it was good with a slight breeze with no wind it was so much easier to fly. Again the biplane went higher but this time I preferred the single winged plane as it flies faster. I think this plane is very simple and very self explanatory. I really liked the way to charge the plane but it think it could be made better with a stand whilst it is charging. The only thing I didn’t test was whether it was breakable or not but someone (I think he means me - Ed) got one stuck in a tree and they were throwing tennis balls at it and it didn’t break. Also I crashed it hard it to the ground and it didn’t break. I think this is an excellent feature as a lot of people will buy it simply because it cannot break. I think this is a fantastic present for anyone of the ages 8+ or maybe lower because it is unbreakable. I think it would look good with different colour schemes and patterns on the wings. Overall it is a very enjoyable toy to play with on a calm day.

Jon Roach (35)
What-ho!  Squadron Leader Barney Halibut here.  After I was separated from the Squadron, I was picked up by a rum-looking chap.  Clearly not a military man, nor a flyer.  Give him his due, he read the instructions carefully before he set about preparing the kite.

We chose a calm day to take the kite out for a first spin.  Switched on the wireless, ran up the outer engines (it seems that the centre engine is just a dummy ­ dammed cheek and not the best thing to impress the enemy) and set off down the garden.  Took a few goes to get the kite under control, but after about ten minutes we were looking good.  Jolly sturdy, this crate, it hit a number of trees and hedges but no damage done.  Then, blow me, the chap got all cocky and before I could stop him we were into the hedge and down into next-door’s garden.  Well here’s a rum do, I said.  Chappy got a big rake and reached down over the fence, scooped the wings up with the rake, and lifted the kite back to base without a scratch.  Just as well the boys at HQ gave him the biplane.

Next, we went off to the park on a calm evening.  Full throttle and off we went.  Some turns at first, although the chap was a bit ham-fisted so it was either hard left or hard right, but we were having a lot of fun.  Then it was upstairs as high as we could go.  After a couple of minutes we were about a hundred feet up, but it wasn’t as calm upstairs as on the deck and we were blown away towards some houses.  Forgot to check the met, didn’t he!  Can’t bail out, I thought, the kite might hit a school.  I began to wonder about the range of the wireless.  The box said the kite is controllable within fifty yards, but we were more like seventy-five yards away and still headed towards the houses.  He waggled the stick, and the crate responded like a good’un. So it was full power, and back to base as quick as we could.  We beat up the park with some low level aerobatting and after about ten minutes it was all over and the kite was out of juice.

Jolly good show, I say.

Trevor Hewson (60ish)
The version Mike gave to me to test is the X-Twin Eagle-Wing, a high wing monoplane with a conventional tail and two motors slung under the wing in pusher configuration. Flying surfaces are of EPP and extremely resilient, whilst the fuselage is a plastic tube which is also very flexible.

First test glide attempts in the garden resulted in an extreme stall. I added a little noseweight and got an equally extreme dive. Okay, so a bit less noseweight, then! After one of these untidy arrivals, the tail seemed to be out of alignment. As I tried to twist it straight, it came off in my hand, revealing a length of copper wire running down the fuselage tube - the aerial, I assume. The tail just plugs straight back on without problems. Full marks for crashability.

At the flying field, I first tried the model as supplied, i.e. with no noseweight. Launching with power on, the nose went straight up. Cutting the throttle, then re-applying it after the stall resulted in an even steeper stall. After a few more failed attempts to get away, the penny finally dropped that, if one launches with full power on and holds it on throughout the stall, the model quarter bunts out of the top of the stall and will then climb out. (I have to admit that this is exactly what the instructions tell you to do!)  During this climb, one can steer right or left circles quite easily but, the moment the power is reduced, a series of deep stalls ensues and the only way of exerting any control is to apply and hold full power and resume the spiral climb. With no hope of controlling the descent there is no option but to cut the power and watch the model drift downwind in a series of stalls. Safe, but not very satisfying.

After the judicious application of noseweight to obtain a smooth glide, I tried again. Nice glide from launch, apply power - and power dive into the ground! Reducing the noseweight to allow a moderate stall, I could then climb out under half power, but reducing power again resulted in a stall - I could not manage a transition from climb to descent at any power setting. Full power though still pushed the model down into a dive which I suppose gives an alternative to the stalling descent, but is hardly an improvement.

Mike and I eventually concluded that there was too much upthrust in the model (remember these motors are mounted high behind the cg, so upthrust increases the downward pitching moment). Some brute bending of the motor mountings did indeed bring about an improvement, at least for the first ten seconds or so, before the resilience of the EPP re-established the original thrustline, resulting in a violent tuck under. We eventually managed to achieve controlled flight in a trim setting where the model would climb with low power and, with a bit more power, could be put into a controlled descent. However both extremes of behaviour were still present - power off, and it stalled, full power and it went into a vertical dive. I even managed a full half bunt into inverted on one occasion!

So, good fun, but a trimming challenge. For someone looking for a first step into radio control, this is perhaps not the best of the bunch. As Mike remarked when I was concentrating hard trying to remember to apply power to come down and ease it off in order to climb, "Be careful you don't train your thumbs to do things you might regret!"

And what about mine?
My version, the Turbo GX, is unique in having a foreplane as well as the usual selection of flying surfaces. As supplied it flew safely, turned very tightly and with power off descended quickly in a series of deep stalls.  It was very difficult to fly back upwind because it was so hard to fly in a straight line.  But it was great fun and on a calm evening it would spiral upwards almost OOS on full throttle, but descend quickly and safely.  In it’s “out of the box” trim it is ideal for beginners in a restricted space such as a football field because it flies in a spiral and as soon as the throttle is released it lands very quickly

That evening I moved the balance point 5 mm forward with 2 small self-tappers in the nose and removed the return spring from the throttle stick.  The improvement was dramatic!  Although still a challenge to fly straight, it was much more controllable and after some practice would fly upwind.  I had a lot of fun during the official evening dog-walk, flying around with one hand on the “rudder” stick and one hand on the dog lead (he tends to chase model aircraft if not restrained). 

What’s Inside
If you fancy making something out of the hardware, I have a couple of suggestions based on taking mine to pieces.

• The back of the TX comes off with 6 small screws and the throttle stick return spring can be removed to provide conventional ratchet operation.
• The aerial is very fine copper wire and easily lost when cutting out the RC gear.
• The props are handed and the motors turn in opposite directions ­ a good example of the sophisticated thinking behind these apparently simple toys.  I only found this out after re-soldering the wires to turn the motors from pushers into pullers (silly me).
• The Tx goes into sleep mode if you don’t switch off.
• If in doubt ­ READ THE INSTRUCTIONS.

Conclusions
These are excellent little toys which could easily form the basis of an RC modelling future.  Even complete beginners learn the correct management of throttle and turn very quickly and these skills can be transferred without alteration to a larger more complicated model and transmitter.

As has been mentioned, they are pretty well unbreakable.  Mine had to be de-tree’d twice, one by the tennis ball method and once by a shoe and survived with only a slight crease in the tailplane.  Jim’s had a strut come loose and his charging system failed (maybe a dead AA cell?) but all the models are still flying.

Which model is the best?  Dan Sowden had the other mid-wing monoplane and we agreed that they seem to fly better than the biplanes.  Trevor’s was the poorest flyer and would not have been so much fun for a beginner.

Verdict
Fantastic fun and very good value for money. 

And for my next trick...
I simply could not let my little plane go without some minor modifications.  After stripping out the gear I slung together some 1mm Depron and 1/16th sq balsa.  Actually, it took ages to get everything in the right place and despite testing the electronics at every stage the thing does not work!  It glides well, however. I will have to prize Sqn Ldr Halibut’s plane off him and take out his electrics.  More later!

Right: The Dunne tailless twin pusher (yes, it's a scale model!)

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