Month: January 2015

It’s Perishing

The temperature was hovering around zero when I left this morning. Today was certainly eventful. I had three flights with the RS352, managing the best landing I’ve ever done so far on the second flight. The wheels touched the grass, no bounce and the aircraft ran along the ground for some distance before coming to a stop just in front of me. I must have just got lucky and hit a flat bit of ground. The third landing was rather good as well, not just for being a good landing, but also for the fact that the right aileron had stuck.

The first I knew of the problem was when I was turning the aircraft back towards myself and it didn’t respond. Going through my mind was that it could be atmospherics, but it feels more like a radio issue. I had just been telling someone that I have never had any problems with my Futaba FAAST setup, so I should know better. Anyway, two turns later and I’ve worked out that it doesn’t like turning right. It’s now lined up for a perfect landing, and when it stops at my feet a quick waggle of the right stick confirms no movement on the right aileron. The differential accounts for the sluggish right response. I’m just glad it was locked in the zero position and the left servo was still working.

The offending right aileron servo which stuck in position

The offending right aileron servo which stuck in position

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Left and right servos in the aircraft

I probably can’t complain as they were the budget EMAX ES08MA servos from Robotbirds and they were 2 years old. I’ve suspected for a while that the elevator response is a bit uneven and the rudder servo might have broken a tooth, so I’m going so swap out all the servos for more expensive ones. Probably analogue ones again as I’m not a big fan of digital.

As for the rest of the day’s flying, the guy with his home made foam board flying wing managed quite a few flights. The our French and Italian firends arrived with a Discovery ST high wing trainer, a very nice silver Hobbyzone SuperCub S (micro plane, similar to the Champ), a micro quadcopter and a Chris Foss AcroWot. Unfortunately I never got to see the AcroWot fly, but maybe next time? One last thing, but when they were fixing a GoPro camera to the Discovery with velcro, I suggested tying a piece of string round it just in case the velcro came off. It’s a simple idea, but in the event that the camera fixing fails, the string means it will trail behind the aircraft and it saves the camera.

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Darker, It’s Definitely Getting Darker

This morning we caught the tail end of the heavy rain that went through overnight. It took me a while to work out why I couldn’t see out of the windows until I realised that the light misty rain was causing them to fog. This is the kind of rain the envelops everything outside, so no flying today. It then got darker, rained more heavily, cleared, turned bright and sunny, then rained again, just because it could.

Cocooned inside in the warm I finished off the undercarriage mounts for my ATOM autogyro, so the fuselage pod is almost complete.

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There’s still an awful lot of sanding to do to complete the front curve though. The second image shows the soft balsa glued to the top of the fuselage and sanded square to the sides, front and rear. Honestly, it really is square, but the camera’s perspective makes it look like there is an angle.

I’ve got some thoughts about making the rotor head myself, but I’ll have to draw up some plans first.

As for the flight simulator, it’s getting close to flyable. I’ve got the joystick working, but the flight model is a bit hacked. I’ve exported my RS352 model into Blender though, so getting a working Collada file into the flight simulator will provide the impetus to get it to the alpha release stage.

Three Jumpers

Definitely three jumpers weather. We’re between two big weather systems today that brought wind and rain yesterday and promise to do the same tomorrow, but today is bright sunshine with 15mph winds forecast and cold. There is not a cloud in the sky to give any visual clue of the wind and I almost didn’t go this morning, but I haven’t flown since before Christmas, so, let’s go fly something.

OK, it’s definitely windy. We used to say that it was too windy to fly when you can see leaves blowing along the ground. I think the wind has blown all the leaves away and there were occasions when I had to hang on to my model to stop it blowing away. Anyway, I started out on my own, but was quickly joined by the guy with the foamboard flying wing, then a little later by a French family with a whole array of aircraft including a DJI Phantom quadcopter, ST Discovery aircraft, Hobbyzone mini Cub (like the Champ, weighing about 15g) and a the HubSan X4 quadcopter that comes with an onboard camera.

In the end I had 3 flights with my RS352, trying out the gloves I bought last year for the first two flights. I got these Tegra work gloves after one particularly cold day last year when my fingers literally froze and I couldn’t move them enough to land. I remember one of the two Polish flyers there telling me that it was always this cold and windy in Poland, so they just ignore the weather and get on with the flying. I should be grateful that I haven’t had cause to use them much because of how unseasonably warm it’s been lately. It’s actually very difficult to fly in gloves, even very thin ones like these. Normally I throw them away for landing, but they do make a huge difference in preventing my hands from freezing. I think the solution is to try them with the flight simulator until I get used to flying in them. Incidentally, I’m in the process of getting the RS352 model from Sketchup into Collada and into the simulator, as well as figuring out how to use my old RealFlight controller as a joystick. Having taken it apart, I’ve got it partially working, so I’ll post some details on the electronics later.

Anyway, back to the flying and in addition to my 3 flights with the RS352 in some really nasty air, the small flying wing was interesting to watch in the windy conditions. I thought at first that it might be a lack of directional stability, as it was yawing back and forth noticeably flying into wind, but I suspect that it might be that the two fins at each wingtip need a small amount of angle before the “bite” into the airflow and start to generate a corrective force. At that speed (it’s very quick), the large corrective force is then under-damped and you end up with it yawing left and right, sawing its way through the wind. My wing also does something similar, so I would like to understand this effect a little better.

The only other flights were the DJI Phantom, which nearly tipped over in the wind, the Hubsan X4, the HobbyZone Cub, and the ST Discovery,¬†which I really wanted to fly. It just looked so elegant and stable in what were really challenging conditions. One minute calm, next minute windy, but seriously turbulent. At one point the RS352 seemed to get tossed around on the spot by the turbulence, which threatened to throw it into the ground. I had to to use full power to climb out while trying to keep the nose vertical. Yes, I really mean vertical, lucky it’s got that kind of power. Now, I’ve flown a HobbyZone UMX Champ in these conditions and the Cub looked just the same. A 15g aircraft really has no right to fly in wind like that, but they do. I’ve also flown my Hubsan when it’s ridiculously windy, but this one ended up drifting downwind badly. The Discovery just looked right for those conditions, flying impeccably.

Just to finish, here’s a picture of the DJI Phantom in the bright sunshine. Note the lack of clouds – they must be hiding.

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RCM&E Atom Build

I woke up to thick fog and freezing conditions this morning, so no flying this week.

I really need to get on with building the RCM&E Atom as I haven’t touched it since before Christmas, despite the required spruce and plywood supplies turning up from SLEC the week before. Their mail order service was certainly very prompt as I was worried about getting caught up in the Christmas mail order chaos, but it arrived in a couple of days.

My main reason for writing this article, though, is to prevent other people from making the same stupid mistake that I made. Now, I’ve built a couple of dozen aircraft from ARTF through to scratch built own designs, so I’m not a complete novice, but I must be getting out of practice. I could try and blame the lack of 3D construction diagrams with the ATOM plans, but the truth is I measure the wood wrong. The photo below shows the problem:

Looking from the back at the sandwich of B1, B3 and B4, plus sides

Looking from the back at the sandwich of B1, B3 and B4, plus sides

Back view of the fuselage with the sides removed

Back view of the fuselage with the sides removed

The base piece, B1 is 5mm balsa, along with B3 which sits on top. Then the top piece, B4 is 3mm. In the photo you can see B1+B3+B4 in the centre with the pencil drawn vertical datum lines visible going up along the end of all three pieces for alignment when glueing. The two sides aren’t glued at this stage and you can see the doublers, D1, left and right sitting on top of B3 and forming a nice square box. It wasn’t always like this though.

My mistake was that B1 and B3 are from the same stock, which isn’t exactly 5mm deep. Either my eyesight is going, or I didn’t measure it properly, as it’s about 0.75mm thicker than it should be, so 2×0.75mm is 1.5mm and the extra height meant that with the doublers, D1, glued to fuselage sides, the sides didn’t reach the bottom. Without any construction drawings on the plan, it took me a long time to work out what was wrong and how everything was supposed to fit together, but then that’s half the fun anyway. I like the idea of the plans being a bit “open ended” as I always like to tinker with things, so this isn’t a criticism, just a bit of advice for anyone else building it – measure B1+B3 together!

Anyway, my solution was to place the base on the flat building board and offer up one of the sides. Then I drew a very fine pencil line along D1 using the top of B3 as a guide. Placing the fuselage side flat on the worktop, I cut very carefully just inside the thickness of my line to remove about 1.5mm from the bottom of D1 so it now fits as in the photograph above. Then I repeated the process for the other fuselage side.

OK, so everything now fits together and I think I understand where all the remaining pieces go, so the everything should just fall into place. I won’t forget to double check all the angles, though, as the modified D1 might have some consequences for the former and mast angles. And the hole is obviously slightly bigger than my 5mm square spruce strip.

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