wlfk

Well, boom strikes still seems a pretty accurate description. I guess that is something that will come with practice. The obvious answer is to only land when the helicopter is level and is not moving horizontally). But of course that's rather glib and doesn't help much. But you will find that when you're in a stable hover, the heli should keep straight and level for a second or two without any control input. You want to land when you've got the helicopter into this sweet spot when it doesn't need any input from yourself, and is roughly stationary above the ground. Perhaps obviously, perhaps not, don't worry yet about where to land. In time you can pick a daisy and land on it. But for the moment, just get it stationary and land wherever that happens to be (within reason). It's a good idea to keep helicopters well away from you for safety's sake, but on the other hand it's much easier to judge whether or not the helicopter's moving if it's relatively close to you. I tend to land about 3-4 metres away. You may be able to get smaller blades - I had a brainwave and bought some 280mm blades instead of the usual 325mm. Performance was pretty poor, but it saved me a lot of boom strikes, and all I was doing was hovering so it didn't matter if the beastie couldn't climb for toffee. Finally, even if the root cause of the problem is that the blades are being knocked out of line, this doesn't make that much difference if the blades are at neutral pitch when they strike. If one blade is knocked back the other might be thrown forwards, but they won't swing closer (or further) from the boom unless the blade grips are angled away from neutral at the time. Finally, I'm not completely convinced by training gear, perhaps because I only ever tried the cruciform type as well. One day I crashed and broke the training gear, but somehow not the helicopter. In my frustration I simply took it off, and suddenly found that I could fly much better without it! It found its way to Ebay soon after. Hope this helps - it does get better! K

How tight are the blades? If they're too loose this can cause strikes. I had zillions of boom-strikes when I was learning to hover. At the time I thought it was all par for the course: it isn't. I rarely if ever have boom strikes when landing now, even though some of my landings are no better controlled than my earlier efforts. Things that contribute to boom-strikes include: lowish head speeds (e.g. a headspeed you might choose whilst learning to hover)negative collective or neutral collective when landinghigh vertical velocityYou can actually get away with 1, or sometimes even 2 of these. But all 3 together and you're in trouble. ~~~~~~ I'm not certain it would be advisable at your stage, but I now do all my landings power-off. Hover about 1-2 feet off the ground. Ensure no groundspeed or gusts of wind. Hit 'throttle-hold' then try to keep the heli from the ground as long as possible by smoothly and slowly increasing collective. Ideally, you land gently and with full-collective and very little headspeed. You don't have a lot of vertical speed, so there's little momentum to carry the blades down to the level of the boom. As soon as the skids hit the dirt the blades un-stall, and because you have full collective they're lifted up and away from the boom. The risk is ballooning up, finding yourself with a stopped rotor and a long way to fall. Even then you sometimes get away with it - on a little helicopter at least. K

To state the obvious, how the heli flies will be largely down to its size, not the power source. By lowering the headspeed, you can tune electric helis to have relatively long flight-times - 10 minutes or more would be a very reasonable target. But for larger helicopters the batteries can get quite pricey. K

Why does stuff have to be broken up - I can see why one stressed bit of airframe bodes ill for the rest, but presumably not the avionics or engine? I've always loved this plane - like someone else who posted here, I had the airfix model on my ceiling a few decades back. Great looking model, Tony. Once I'm finished your spitfire, who knows?! K

I honestly don't know - never seen one in real life, just on the internet. I have a T-Rex 450, which is about the same size - basically looks like the Century is a clone. They take the same parts which is good, because T-Rex parts are relatively cheap. If the Century is equally robust and flies as well, then it would be a very good option. If not, then... Conceptually the idea's fine. I use A123 batteries, 3s. It involved some modification to get them to fit in my helicopter, but I think they're by far the better option. They last much longer and can be charged much faster than LIPO batteries and are also safer. www.brchobbies.co.uk sell them, though you can't use an ordinary LIPO charger. There are several ebay shops that sell the commonly broken parts (booms, main shafts, feathering spindles, main gears) about 1/2 the price of the Align's own parts. By and large I haven't had too many quality issues - some of the tailbooms needed holes drilling but that was about it. All the same, I've easily spent the cost of the heli on spare parts and being realistic you will need to budget for this. K

I'm not disagreeing with you Eric - but there are reports of people actually having got coax helis to fly successfully. Not so for the cheap single-rotor helis. K

I'm going to spoil things by suggesting that you need to spend significant money if you want to buy something that will fly happily outdoors. The co-axial helis are the only cheap ones that generally fly OK, but fixed-pitch helicopters generally have a bad reputation for dealing with wind - even the larger ones. The heli forums are filled with reports of people who've bought cheap RTF helis that they've never got flying in a way you could describe as 'controlled'. Mentioning no brands, my flatmate got stung this way too. A T-Rex comes in at £400 or more, by the time you've bought some half-decent servos, batteries and a gyro. www.clearviewrc.com is a good simulator for the price. K

Clearview (www.clearviewrc.com) is a far better simulator than FMS, and it won't break the bank either.  K

Seems to me it would be simpler to make some reduced-size cowling/canopies than to re-issue a larger sized plan.  K

Bill, Nicely put - that makes a lot of sense. K

Jonathan, Have you seen a good 400 size heli fly (e.g. T-rex 450). It's much smaller than a 30 size but the fact that it is not 'serious' in terms of size doesn't mean that it's worthless. I can fly in 10-15mph winds; I can land on a daisy of my choice, and in good conditions hover within a few inches either way. The fact that it's small simply means I mustn't let it get too far away from me. At my stage, it's not about performance; it's about making mistakes cheaply with a learning curve that's not too steep. "On falling down a 1000ft mineshaft, a mouse is stunned but lives; a rat is killed; a man is broken, and a horse splashes". On the same grounds, a smallish helicopter will be damaged far less than a bigger model would be in a similar crash. There's also the obvious point that 3d pilots choose their machines with different objectives from learner pilots. Today I had a lockout (complicated story - not Futaba's fault) and my heli fell without power from about 20-30M to the ground. Somehow it landed on the skids, had a very minor boom-strike + bent the flybar when it fell on its side. I flew another pack before taking it home and changing the boom. I've seen some appalling small helicopters and regarding those I would agree with you 100%. My flatmate owns one and I don't think it will ever fly in a controlled fashion. K

I was thinking of doing an electric conversion too. I was wondering about an Axi 4120 - shame as I have an Axi 2826/10 knocking around. According to the specs this won't be quite powerful enough... K

I can appreciate the finance thing... On the other hand, that would be 150 wasted if you don't get any good use out of it. My flatmate bought a Walkera #4. I don't know how it compares to the #22, but I have to say I can fly my T-rex but I can't fly his helicopter (neither can he). One way round might be to invest in a good sim and a decent transmitter this year, and buy a decent heli next year. K

As the saying goes... "Standards are important... That's why we support so many of them". I agree that a lack of standards is inconvenient, but I don't see how it is dangerous, unless it's through forcing people to solder connections themselves, which is moderately difficult and could be dangerous if not done correctly (e.g. stray strands of wire; shorting the connections whilst soldering etc. etc. A lack of standardisation generally just means that you can't plug one type of equipment into another. The problems come when it means that you can plug things in back-to-front, which could cause a fire. The other problem could be charging at the wrong rate. This is probably more a concern for serious modellers who buy after-market chargers than the ARTF people, who get a simple plug-in-and-go charger that won't charge their batteries at too high a rate. As Erfolg points out, lithium batteries are used in many types of equipment, but they aren't generally the soft-cover lipo batteries that we use. There _have_ been many incidents of fires and recalls due to faulty batteries in laptops and mobile phones. Lipo batteries are inherently more dangerous than other types, I don't see that the connectors have much to do with it. If I was going to introduce an innovation that could make life simpler and improve safety, it would be an addition to the interface that enables the battery to provide information to the charger about its capacity, temperature etc. My understanding is that mobile phone batteries have temperature sensors incorporated, which is why they generally have so many connections on them. The very simplest interface could simply consist of 1 extra wire and a resistor whose value could be varied, to correspond to the safe charge rate for the battery. e.g. a 1000mAh battery could be charged at 1A and could be fitted with a 1K resistor. A 2000mAh battery could be fitted with a 500 ohm resistor (2ce the current for the same voltage drop). The resistor would be a current-sense resistor, rather than limiting the current. So it would be very light (low power) and cost all of about 10p. It would lend itsself to very simple circuit designs. You could provide an adaptor so that the battery could be charged by existing chargers without breaking compatibility. A more advanced interface could use a 1-wire serial interface (2 additional wires) or industry standard I2C interface (3 additional wires) and simply read out a list of battery parameters to the charger. This could include features such as absolute max rates. Current battery temperature. And so forth. My estimate is that it would cost about 2 pounds in parts. I'm an electronics hobbyist, and this sort of thing would really be very simple - I could design and implement an interface tonight. As always in life, the hard bit is getting other people to see sense. K

Just a reply to my own post. I bought the balsa; built the plane (almost) according to the plans. And I'm impressed how stiff the construction is. Just need to get me some solarfilm and the electrics now. But another question... Does anyone add any ventilation for the battery? K

I'm not sure that our hobby is so innocuous. True there aren't that many fatalities, but neither are there that many fliers... And most flying happens on designated sites. Absolute figures aren't really a good measure of whether or not something is dangerous. Lumps of steel flying around at high velocity are inherently dangerous, especially when they also act as magnets to any small children in the area. Or dogs. In my view, the best approach to safety is something the BMFA does anyway: bulletins of accidents and 'near-misses'. Far more memorable than reading lists of 'donts'. And more likely to be relevant too. As a sideline, now that 2.4gHz is available it's possible to go fly anywhere, whereas before it was advisable to fly at a designated site to avoid being shot down / shooting down others. I wonder whether this will actually cause more conflict between fliers / members of the public than in the past... K

I'm not going to switch from helicopters, but I couldn't resist the EZfan and it's well underway. But I've never flown a plane before except on the simulator. Given that I can fly a helicopter in circuits how steep is the learning curve for an aeroplane likely to be? Common sense is telling me I should build a nice trainer first... K

I've never actually seen an IC helicopter, so in some ways my opinion isn't well informed... I'm also very much biased towards electrical because electronics is another hobby and I understand electric flight. IC engines are a complete mystery to me. But I bought myself a T-rex 450 about 2 months back and I'm now at a level where I could probably get my BMFA A-certificate if I tried. I think it's great. I've taken it out in some reasonable winds (I'd guess 15mph), yet in a dead calm it's wonderfully stable. I disagree with Jonathan. Helis are different from planes. With a T-rex you can practice hovering in a pretty small garden. With a 2.4gHz system, you don't need to go to a flying field as you know you're not going to shoot anyone down. What you need when you're learning is the ability to practice often, so you can learn from your mistakes before you've forgotten what they were. I live next to a park, and can fly most days (unless I'm waiting for parts!). I have 2 batteries at 25 gbp each, and on a good day I get 2 flights in - 2 before work, and 2 in the early evening. Although I only fly when there are very few people about (lovely still air at 6.00AM!) I'm not sure I'd feel comfortable flying a bigger helicopter "in public". I understand that large helicopters are less twitchy than smaller helicopters, but I'm not sure that would have reduced my crash count all that much. Most of my crashes have been due to disorientation or doing stupid stuff where I should have known better. Reading the books, a lot of setting up a heli is throttle/pitch curves. I know you can get governors for IC helis, but in terms of cost and setup complexity ESCs with built-in governors have got to win hands down. Things I have learned... Woodies are a bad idea. I once had a boom strike that killed the blades but not the boom! I got some really short blades (280mm v. 325mm normal). Much less likely to hit the ground or the boom and good for learning to hover. OK - performance was atrocious, but you don't need to do FFF when learning to hover, anyway. Only for calm conditions though. Which bits to keep in reserve. And where to get Alu upgrades for crash resistance. Probably what surprised me most, whilst learning, was the cost of parts. They're not individually too expensive, but boy does it add up. Not sure whether you should mention this in your article. I'm hoping that the more people buy them, the cheaper they'll get! K

I think you should be OK - if the 2 servos are at 90 degrees, then there will be a separate servo for the collective pitch. In that case, you don't need to use mixing at all. There are rare swashplates with funny angles - 140 degrees, and that sort of thing. K

Nice looking plane. It would be silly not to enter!

Just a quick question - looking forward to building this model. I sometimes build parts (tailfins for my helicopter) by glueing thin laminates together with cyano. This makes a very stiff section, without the weak joins that you get when you simply but the ends together (e.g. wing section in the EZEfan). Effectively, it's very lightweight ply, but with the grain directions arranged more carefully. This has a small weight penalty, but it's not more than a few grams and I like the stiff sections. Is there any good reason _not_ to do this? One concern is that if you get any moisture, the wing may warp more if the surface layer is laid in a different direction to the deep layer. K

Erfolg... You're right in pointing out that many activities are more dangerous than flying. As a hang-glider pilot, I used to collect lists of statistics about hobbies that were more dangerous than my own. These included a number that my mother was quite happy for me to take part in, including fishing with my grandfather, and riding horses. Incidentally, the last I heard was that drowning is the single greatest cause of hang-gliding fatalities. Mostly people flying from cliff sites without checking the tide. But on the whole, I'd argue that safety legislation is a good thing. Accidents can often be avoided, and when they do occur their severity can often be reduced. I'd argue in particular with Timbo about the kit cars - maybe pedestrians who get hit by buses don't make it. But as a cyclist, I've had two collisions with cars at speeds over 20mph, and walked away from both. Pedestrian injuries are considerably reduced by measures such as recessed wind-screen wipers, space between the bonnet and engine block. We also have to contend with the fact that other people's acceptable levels of risk are not our own. Some people really would make the decision to go for a walk in the park rather than flying dangerous model aircraft. And it's pretty rough justice if they get impaled by someone whose acceptable level of risk differs. My motto is to do dangerous stuff as carefully as possible. You can still be cautious and have fun. K