Month: February 2015

In the Calm Before the Storm

Today’s weather forecast is for heavy frontal rain by about 1pm, so flying is cancelled this morning. Despite this, it’s a rather annoyingly lovely calm, bright, sunny morning when I get up. It doesn’t last though. Sure enough, the wind soon starts picking up and by 12:30 it’s overcast and the rain is here for the rest of the day. I wouldn’t have got much flying in, so it is definitely a building day.

The ATOM is coming along, honestly. I’ve sanded the front section between the cowl and canopy and I’ve started adding the side pieces to the back of the fuselage.

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One bit about the fuselage still puzzles me though. In the instructions it mentions glueing a piece of soft 10mm balsa sheet behind the ply U/C mount on the bottom of the fuselage. There is no pattern for this on the plan, so I’m scratching my head wondering about the dimensions? It obviously blends the U/C mount into the fuselage base as you can see from the photos that there is no step, but I’m wondering whether this piece is supposed to go right to the back. Also, 10mm is a bit too big. The ply is formed of two 3mm pieces, so a 6mm bit of soft balsa should do fine. That is unless I’ve misread the plans completely?

OK, I did some Googling while I was writing this and my guess was right. There is another piece of soft balsa that needs to be added to the underside of the base to allow the ply U/C parts to be blended into a smooth curved fuselage. There’s a picture on the RCM&E building blog here:¬†http://www.modelflying.co.uk/forums/postings.asp?th=98774&p=2

I’m off to find some more wood…

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Acrostik Flies Again

I’ve been meaning to fly my Acrostik again for a while and finally managed it this morning:

The Acrostik is the black aircraft with the white flash

The Acrostik is the black aircraft with the white flash

Pictured next to the RS352, it’s surprising to see how much smaller the Acrostik is. This model is almost 15 years old, as it was designed by Andrew Taylor one weekend when he had had a number of crashes and was left with nothing else to fly. His original Acrostik was made out of pieces he had lying around and was then featured in a Quiet and Electric Flight plan in October 2000. Terry Stuckey gave me one of the first plans to be printed to build as a test, and it turns out that the tail on mine is smaller than the prototype as it was reduced to fit the paper size. It’s still flying after 15 years, and it must be at least 18 months since I flew it last, but it still flew like it was new. The first attempt at launch was aborted due to no power in the LiPo. They’re quite old too. The second battery had power and it flew perfectly for almost 15 minutes on the 3S 2200mAh with no trim changes at all. This included some mild aerobatics just to test it out, followed by an almost perfect landing.

The weather was looking pretty grim this morning and I was starting to think that I was going to be on my own, but the next arrival turned up on his electric bike with an EFlite UMX Spacewalker and Champ just as the Acrostik flight was nearing the end. My next flight was with his Spacewalker, which was interesting because the designers have had to add excessive dihedral to the low wings in order to make it fly. Control is rudder, elevator, throttle only. While flying it around I remarked that the dihedral looked really excessive, as it was like flying a V-shaped aircraft, while it looked as though there was more dihedral on the right wing than the left, with the wings flexing quite a lot during flight. It turns out that the strengthener on the right wing was damaged, so my comments while flying were quite accurate. After that I flew the Champ, going out of range at one point which was a bit of a wake-up call. I’m not entirely convinced that there wasn’t something else going on, as it also locked out quite close to me and it seemed to make some sort of strange servo or motor type noise. I can’t believe you could hear the small servos over the motor at that range, but for an instant it sounded like the servo was running up and down its worm gear. Maybe it was some sort of radio glitch that momentarily affected the speed controller, motor power and controls?

Just after flying the Champ, another two guys came across the field carrying a couple of Easy Stars. This was a bit weird because we said hello to them and exchanged a few words while still examining the Champ and its controller. When we turned around, they had continued to walk straight past us and had stopped about 100 metres down the path. I think we really should have offered to help them, as it then appeared that they didn’t know how to fly. I was a bit pressed for time at this point, so I left it to the others.

Then another guy turned up with his Multiplex Cularis glider. I’m still waiting in eager anticipation for his Wots Wot biplane. Anyway, three flights with the RS352 followed. I only had one serviceable pack for the Acrostik and it was going to take at least an hour to charge, so that wasn’t going to be flying again. It’s interesting how flying lots of types of aircraft gives you a different perspective on your flying. After flying the Acrostik, the RS352 seems so solid and assured in the air, that I think my flying was much improved for the change. I just seemed to be flying smoother, with landing number two almost perfect, followed by landing number three which was a perfect greaser, rolling along the grass on the wheels to a stop. It’s interesting, because on the third landing it was coming in a lot faster and I cut the throttle completely at just the right point. On the landing before, I was balancing throttle and elevator to bring it in and had a bit less forward velocity when it touched the ground. It’s all a bit of luck though, as it depends on what patch of grass you hit whether it’s going to roll or not.

Finally, they guy from last week with the Hexcopter and small helicopter arrived and proceeded to fly the small one while I was packing up to leave. It actually turned into quite a busy morning for a day when the weather was really grim and I was anticipating nobody else turning up.

It's never a good sign when the cars have their lights on

It’s never a good sign when the cars have their lights on

First Flight

It’s a good day for a test flight. The sun is out and there is absolutely no wind. OK, so there aren’t any excuses left, I have to fly the RS352 for the first time with four new servos. I needn’t have worried though, because it went up and a few clicks here and there had it sorted. I’m still worried about the “buzzing” servos though. When I turned it on at the field, the ailerons and the elevator looked like they were jammed and were buzzing away frantically until I moved the surfaces on the TX. I really don’t understand this as they are all brand new Hitec HS65MG units, so they’re not cheap servos. The problem definitely isn’t to do with the control surfaces or the linkages binding, as they still do it even without the servo arm attached. I actually broke one of the aileron linkages while trying to fix this yesterday, so had to replace both anyway. The problem does seem to be electronic, so the next thing to try is eliminating the receiver.

The RS352 before its first flight with four new servos

The RS352 before its first flight with four new servos

Anyway, with the new servos, it’s definitely slightly different in the air. The elevator seems a bit more responsive and is holding the inverted part of a loop more easily. Not sure why this is, but maybe the Hitecs have a bit more torque? Response does feel crisper all round though. My only niggle was almost hitting the ground a couple of times. There were a couple of occasions where the elevator to pull out of a downward section didn’t happen quite like it normally does and I had to correct again. I did wonder whether this might be to do with the elevator servo buzzing in the air and not finding its position immediately? Further trimming and testing is going to be required to get the aircraft sorted out again, but it is a bit like having a new aircraft to play with.

It must have been the weather, but I had lots of company this morning. In addition to three flights with the RS352, I also flew a Mini¬†Twister Sport helicopter and an EFlite UMX Beast biplane. The helicopter was interesting, largely because I don’t fly helicopters, but also because the trim was a long way out. It was getting a bit windy by this point, but even with full forward, the aircraft still drifted backwards. After a lot of fiddling about, we noticed that the push rod with the ball links going to the rotor head is threaded. The ball link unclips very easily, so I added four turns of forward to it, moved the trim back to centre on the TX and had another go. This time it flew really well, but it was getting much too windy for such a light helicopter by this point.

Next up was the Beast, which was interesting to say the least. One problem with this type of aircraft is that the control linkages are very light and vulnerable to bending. The ailerons must have been a long way out, as it would only go left, even with the stick at the full right limit! Luckily, I knew I could flick the aileron rate off and rapidly found the new centre point for the stick and landed it. To be honest, it was a bit windy for such a light aircraft by this point, so we gave it up after that.

In addition to all this, another guy with a big helicopter turned up, somebody else with a big hex copter and a Walkera QR ladybird micro quadcopter, which looked very like a HubSan X4, but seemed to fly a lot smoother. There was also the Solius Multiplex glider which went really well despite the cold conditions and lack of thermals. Then the guys with the HobbyZone Sport Cub turned up, along with a HobbyZone Firebird Stratos. Unfortunately, the Cub crashed into the ground while I was there and I think it crashed again just as I was leaving. I didn’t see the cause of either crash, but looked round the first time just in time to see it bounce up into the air after impact and obviously survive almost unscathed. They must be made of some tough stuff these Super Cubs. These guys also met up with another friend who had a new foam Cessna and an FW190 which I never got to see flying. All in all it was quite a fun morning.

It’s Windy. It’s Very Windy. And It’s Cold.

No flying this week as the weather is terrible again. The wind is about 30MPH, but that’s probably a good thing as I replaced all four servos in my RS352 this week and there are still a few teething problems. Normally replacing servos is just a case of unscrewing them and putting in the new ones, but it’s a lot messier when all four are held in foam with hot melt glue.

The reason for replacing the servos was the stuck right aileron which I experienced last week. It turns out that the elevator was also faulty, but in a really weird way. All the original servos are ES08MA servos with metal gears. The elevator servo had an issue whereby it was causing all the servos to flutter during power on and also as the elevator was operated. I had thought this was just the start up cycle of the radio, which is a Futaba FAAST set using an old Field Force 8 with FAAST module and R617FS receiver. It must be some kind of electrical fault causing either noise or excess current, but operation of the elevator would cause spurious glitches on the other channels. I’m now anxious to fly the aircraft with the new servos to see how much this was happening during flight. My feeling is that coming out of a loop and releasing the elevator to neutral would have caused an aileron and rudder glitch.

Anyway, two days after placing an order with RobotBirds, four brand new servos and a pin vice arrived on my doorstep. All four servos have now been replaced with the new Hitec HS65MG servos, which operate so much better than the cheap ES08MA servos that didn’t seem to centre very well and were much slower. The only problem is that I’ve now got another weird issue with the ailerons. When I flick the switch to bring the ailerons down as flaps, occasionally one or both servos will appear to jam and not find the position, fluttering wildly as if it has stalled or the control surface is stuck. The problem is that with the servos stuck in with hot melt glue I can’t easily remove them again to check what is wrong. Initially I thought it might be due to a low voltage on the 4.8v Rx NICAD I was using for safety reasons, rather than plugging the LiPo into the ESC and having the motor system live when I was setting up. I took the propeller off and used the bigger LiPo with the same effect, so it isn’t lack of voltage. However, I suspect that it’s to do with the new servos being slightly bigger than the old ones with the servo arm very slightly higher up. I’m going to try cutting some of the material out from around the servo head and see if that is what is causing the problem. Otherwise I’m going to have to extract the wing servos again for further inspection. They definitely worked before they were installed though.

How To Remove Wing Servos from Foam Wings

I had to remove the servos from my RS352 recently because of the right aileron servo failing. As the wing is EPP and the servos are held in with hot melt glue, this isn’t a particularly easy job. My eventual solution was to use a large piece of plywood placed on the surface of the wing to provide a hard point for a lever with which I could carefully prise the servo out.

As you can see from the photos, without the plywood, there is nothing solid to use. While you could grab the servo lugs with a pair of pliers and pull, this will likely pull a large chunk out of the top of the wing. This method loosened both servos enough so that they could be wiggled free without any damage to the surrounding foam or top of the wing. The hot melt glue remaining in the hole was removed by slicing it into small strips with a sharp knife and peeling it off. The operation was a complete success with the two new Hitec65MG servos then fitted into the holes.

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