John Olsen 1

Didn't a lot of the early German planes use an external ASI? Quite often mounted on a strut on the biplanes. I don't know if an Eindecker would have used one or not. John

The DX5E supposedly does have expo. I say supposedly because I have tried to activate it, but could not tell if it had made any difference...I have hardly used the DX5E because I bought a DX8 before flying the plane that I originally bought the 5E for. Anyway: To activate, hold the aileron trim switch to the right when powering on the transmitter. Release the trim switch after a series of ascending tones to confirm that expo is activated. To deactivate, hold the aileron trim switch to the left when powering on the transmitter. Release the switch after a series of descending tones to indicate that expo is deactivated. Note that I have no idea how much expo this will give, and that there is no way that you are going to be able to change the setting in flight. So if the way it is set is working for you now it might pay to leave it alone. John

Not just the multiplayer...I just tried selecting the F16 and it instantly blows the program away. OK, I admit it, I was going to try the underwater flying thing again to see if they had fixed that. Obviously it won't work with the F16 now, but it still works with the A10...however the behaviour has changed a bit. The rudder used to work quite well for steering in the water, now it doesn't. I haven't tried the multiplayer with k, but with j last night I found I could not join any sessions. Maybe being down under it thinks my lag is too long? I was able to start a session OK but nobody joined it. I've also been trying the Sopwith Camel with each version. With V4 I never used to have any luck flying that, maybe fluke one landing in ten. Of course if the model is true to the behaviour of the original that might be quite realistic. With V5 I can fly and land it just as well as anything else...however with 5.0.k it does seem to have acquired an interesting wing dropping habit that I have never noticed before. John

It is not very likely that a modern receiver would contain anything that would be affected by the stray magnetic field from the little magnets used to hold hatches shut. The older type of receiver with coils wound on magnetic cores might have been, but then those were usually shielded with a can because of that, and also to prevent the field from one coil coupling to another. John

One went at our club a couple of weeks back, same cause, the ESC was packed in with foam inside the fuselage. The result was a bit like Keystone cops, the owner running towards the shed yelling for the extinguisher while another guy ran past him towards the plane carrying it. One point about this is that the ESC is likely to keep on generating heat until the battery goes flat or until it melts a connection, so the extinguisher may not be enough. I had one go, but that was mounted on the outside of the plane so cooling was not the issue...I suspect a vertical dive into the ground in the previous plane may have caused an issue which did not show for a few flights. It went while it was on the ground with the Wattmeter in circuit, so disconnecting in a hurry was not too hard. John

Is this low enough?

Some chargers will discharge the batteries down to the storage level, eg depending on the state of charge, the same setting on the charger will either charge the cells up or discharge them. They can do this because the balancing feature on the charger has the ability to discharge cells. The advantage of using the charger is that you don't have to remember to stop it at the right time since it will stop itself. Having said all that , I have to admit I don't worry about storage charges myself, but then I live in a climate where it doesn't usually get very cold. John

I don't know if you are aware of this, but ESCs can give problems if the leads to the battery are too long. I think this has been discussed here before although I can't remember what the thread was. You may need extra capacitors to supplement the ones on the ESC. Long motor leads are not a problem. John

OK thanks guys, after the silly season is over I will see if I can find some locally. John

Hi Guys, I am just repairing a Parkzone Stinson. I have had to replace the battery box, since one of the strut attachments which is part of the box had broken. The original was glued into the foam with some sort of gummy glue that stays a rubbery consistency. It seems like a good idea to use something similar, since otherwise it probably would have been impossible to get the old box out, and who knows, I may need to repeat the process some time. Anyone have any idea what sort of glue this is likely to be? It sticks OK to both the foam and the harder smooth plastic of the box, but not so hard that you can't get them apart without wrecking things. John

One thing we take along is one of those cheap picnic mats that folds up small. If you do find the need to take something with small screws apart, it is nice to have a mat underneath. John

One of our guys had to call for help from his wife the other day. Nobody at the field had jumper leads, but we all had a lot of fun laughing at him. Discharging and recharging a car battery is quite hard on it and will reduce the life. Leisure cells are better for our sort of service but you still don't want to run them down too far. For smaller Lipos you don't need a very big battery. For a while my son and I used an 18AH sealed lead acid as used for security alarms. That is in theory good for about eight charges into a 2200 3S lipo...I doubt if we ever used more than four or five charges on any given day. A battery like that is not too bad to cart around. Ours is built into the flight box, with a socket that can be used either for the battery charger or for the starter for the IC engines. John

Hi Guys, Just a point about this that occurs to me. If two packs are used sometimes together in one model, and sometimes separately in another, will they tend to age differently? I know with NiCd and NimH the usual advice has been to keep sets of cells together. If one cell has lost capacity due to having done a lot of other work, then you don't want to charge it in series with other newer cells. Now maybe the use of a balance charger would take care of this for the Lipos. But my own feeling would be to keep a set together, whether parallel or series, so that they have the best chance of all staying matched. The investment in batteries does to tend to encourage sticking to one size of model. For charging at the field without taking too long, you just need a good big charger, and of course a decent sized battery to charge from. I'm using a Turnigy Fat Boy from Hobby King which has proved very satisfactory. I have a plane that I have two 6S batteries for, a 4200mAh and a 5000mAh. An eight minute flight uses about 2600mAh, and I can put that back in in about half an hour or so...so by the time I have chatted to the lads and used the battery that just came off charge, the other one is fully charged again. I don't charge at the maximum specified for the battery, if I did I could almost recarge one in hte flight time of the other. I'm trying to persuade the club to put some solar cells and a storage battery in the club hut to save lugging my own battery around. That would be nice. John

The trick is to get something through the path you want to get the snake into. Then you use that to pull the snake in.One technique is to attach a small weight to a piece of thread. You can dangle that into the first opening, then use a bit of gravity, gentle shaking, good luck, and pesistance to get it through all the way. Another is to use a piece of material that has some stiffness of its own to probe a way through...a piece of wire for instance. Soft wire that you can bend helps a lot as you can follow curves. Both of these do of course require that there is a clear hole through. As Gazza says, provided the snake is secured at each end it does not matter if it is secured in the middle. It works like a cable on a motorbike, where one end may be on the handlebars and the other on the frame but the control movement is still communicated OK. Of course hindsight would say that you should use the old one to pull the new one or a pull string in but I guess it is too late for that! John Edited By John Olsen 1 on 06/11/2013 00:14:20

Hmm, I'm going through some thinking about this at the moment. My Balsa USA Morane-Saulnier AI is covered in Koverall, went on very well and shrunk up nicely. Now I have to decide on a colour scheme and type of paint and fuel proofer. The BUSA suggested scheme is of course an American one, eg silver with the allied roundels. The French ones were a camouflage scheme which would look good and allows interesting markings like the little devil with the pitchfork. The trouble is the camo might make orientation more difficult although a plane this big should not be too hard to keep track of. Either way it will need to be either fuel proof paint, or have something suitable applied afterwards. Any thoughts? John

I had a similar problem to the OP on a fully cowled Saito 91. I haven't flown it again yet, but after some chasing around I realised that the internal lead ballast was potentially blocking the airflow a bit. It has now done a long ground run without any sign of problems, so I hope once the weather permits it will be OK in the air. Of course I realise that the engine in question may not be as fully cowled as my Fokker DVII, but it does show that overheating can give the symptoms observed. Mine was gradually losing power in flight, such that you had to land after about three minutes. John

I dunno what is readily available in your neck of the woods, but the various "Stick" incarnations make good introductory aerobatic planes. Hangar 9 have dropped their Super Stick, but I think still have the Ultra Stick, and Great Planes do one in two sizes....I have a 40 sized one electrified at the moment, but they do a slightly bigger one too. They are a shoulder wing design, eg not high like a trainer, but not all the way to a low wing either. Good thick symetrical section. Mine is a little on the overpowered side with a 60 equivalent electric motor, it will go vertical very fast. They are capable of a wide range of manouevres, more than I am capable of yet! John

Oh yes, propellors can fly off. IC engines can throw them if they backfire. (eg the nut comes loose and the whole prop flies off in one piece.) Four strokes running a bit lean are especially prone to this which is why they usually have an extra lock nut, but two strokes can also throw a prop, although more rarely.. The prop itself can break, for instance if it touches something, or if it has been weakened by having a metal spinner cut into the blade. If it loses one blade, the resulting out of balance forces can pull the entire firewall out of the plane. Electric models are not immune either. The colletts used can slip, allowing the prop to work its way off. A drop of locktite here can be a good thing. The same sort of things can happen to the prop itself, eg touch something and get damaged. Again the out of balance forces can do more damage than the initial problem did. I landed an electric Super Stick with the motor hanging by the wires once, after the collett let go and the prop went. We did find the prop and spinner later! John

re Chapter four...if you are a bystander and something like this happens, you should try to get a line on where the loose falling object hits the ground. The pilot will of course be busy trying to get the rest of the airframe down in one piece. We had one locally where the entire engine and firewall came out of a model, the prop having thrown a blade. I got a line on the engine as it fell, and by walking straight towards the point where it had fallen we were able to find it in the long grass quite easily. The pilot had managed a pretty passable dead stick with the rest of it, so it lived to fly again. John

Well, I have not been a radio technician for a long time now, but I can assure you that loose metal to metal contacts can cause interference, and there is actually more than one mechanism possible. First...one of my former bosses did an investigation back in the 1950s (long before I knew him) into interference caused by ordinary wire fences. Standard number 8 fencing wire as used in those days was galvanised, and it turns out that the oxide layer from two wires twisted or looped together at a join can make a crude diode. In the presence of radio signals this will lead to the formation of intermodulation products. If only one carrier is present, you will just get harmonic frequencies, eg A, 2A, 3A etc and as is usual in such situations, the energy in each harmonic will tend to fall off, and they are well out of band anyway. If there is more than one carrier present then more complex products will be formed. For two carriers the most important one will be 2A-B, which will fall in band. For three carriers A+B-C is also important. Note that the resultant carrier will carry the modulation that was on each input, and that as well as 2A - B you will get 2B - A. These effects are very real and I have obseved the products being produced with spectrum analysers. My last major involvement with this sort of thing was writing a program to calculate intermodulation products in a linear amplifier used for single channel per carrier operation at a satellite earth station. Each voice channel used a separate carrier, and these were amplified to kilowatt levels by a linear amplifier. As any engineer will tell you, linear amplifiers are never quite perfectly linear, and get quite non linear if overloaded, so it was important to be able to predect the level of intermodulation products. Getting closer to our own situation, we don't want any intermodulation products generated that lie within band. In the realities of a flying feild situation, it is going to be really hard to know if this was the problem or not. Bonding or insulating loose metal joints is a good precaution...either will do. The second mechanism whereby loose metal connections can cause interference is a bit cruder. If there is current flowing through the joint then the making and breaking of the connection will cause momentary arcing. The current flowing through the joint can be DC or AC. For instance, bad connection in power lines can cause interference. (as also can bad insulators) In our situation, the most likely cause of the current would be radio signals, which need not be from the other guys Tx, they might well be from a broadcasting station. So a vibrating connection acts as a crude make and break, and turns the parts into a crude broadband spark transmitter. Engines are not too likely to cause this sort of problem since most of the motion is taking place inside the metal case. So even if they were generating interference it would be shielded. (Of course spark ignition systems very often require suppressors and shielded leads etc.) In the early days of installing radios in cars, it was sometimes necessary to install special brushes to earth the brake drums, since these could cause interference. These sort of effects are not likely to be a problem on 2.4GHz for two reasons. One is that the amount of randomly generated interference tends to fall off as frequencies get higher, so there is much less energy to cause interference. For microwave systems internally generated thermal noise is more of a problem than external interference. The other is that the more sophisticated modulation schemes used with 2.4 GHz systems can cope with interference better, eg they can detect a corrupted frame and not use it. Interference in general is unpredictable and often unrepeatable and so it is usually best to just take what precautions are reasonably possible and then hope for the best. Erfolg, you can't prove that Pi is 3.142 since it is not! It is of course close enough for a lot of practical purposes. John

We just had a collision at our indoor site between a Vapor and a helicopter. Neither came off very well, although I think on points it would go to the chopper. We usually arrrange to take turns so that all the aircraft in the air are reasonably compatible, but for some reason this did not happen, and the vapor flew beautifully into the rotors of the hovering chopper. Bits of both went in all directions. I also saw a crash at our flying field where the pilot managed to asemble his plane without including the tube between the wing halves...so the only thing holding them in place was the screws at the root rib. It was immediately apparent after takeoff that there was some sort of problem with controlling the plane...when the wings folded upwards it became obvious what the problem was. John

So at the head of the home page...Latest News and articles...The Hangar 9 Sopwith Camel. This is a model that was discontinued quite some time back, over a year IIRC. Good luck in finding one! John

Well, that should look lovely in the air. If you get really carried away you should look out copies of "Simply IC" magazine from around 2000 or so as they published drawings of a working model Anzani engine...Don't know if the size would be right though, and I think it needed castings which might not be readily available. John

Why do you need a special section, why not just deal with your questions in this thread? So for instance looking at your formulae, this is the standard formulae for lift. Like all formulae it expresses the relationship between the factors that determine the result, in this case lift. So lets go through the items one by one... Cl is the coefficient of lift. Usually coefficients mean that there is something missing from our formulae, eg it should probably be much more complex. In this case, what is missing is the airfoil section used and its angle of attack. So what we have to do is look up the tables for the airfoil we plan to use and see what the coefficient of lift is at the angle of attack we plan to use. Back when I was playing with free flight duration models, this was always the maximum coefficient of lift just before stall, but this would not always be the case. (eg you might want best lift/drag ratio, which will be a different angle of attack.) A is for area. The more area we have the more lift we get. So we work out the area for whatever shape we plan to use. (This is the projected area, not the total area of both sides.) There are actually some complicating factors here, like the effect of aspect ratio. Rho is the density of the air, with the formulae I was using back in the day this was expressed in slugs per cubic foot, and for standard conditions was IIRC .00238 slugs per cubic foot. If you try to fly your model in a place with a lower air density, like the Everest Base camp, it will have to fly faster since the density will be less. Higher temperatures also reduce the density, and this is really important for heavily loaded aircraft taking off from high and hot places. V is the velocity, and you will note that it is squared. It is natural enough that you would get more lift by going faster, in fact if you double the speed you get four times the lift. This is because you are acting on twice as much air, by going twice the distance in a given time, and acting on that air with twice as much speed. So the acceleration of the air caused by the curvature of the wing will be doubled, and you will apply that acceleration to twice as much air, so hence four times the lift. Unfortunately the formulae for drag has the same general form, so you also get four times the drag. So why the .5? Well, this is quite a common feature of formulae of this form, you might be familar with KE = .5 MV^2, or S = .5AT^2 If you know any calculus, and if you are serious about getting into aviation design you will need it, the latter formula, for distance travelled by an object under a steady acceleration is actually the integral in terms of time of the formula for the speed . (V=AT) So when you integrate, you increase the power of T by 1, eg from 1 to 2, and you divide by the new power of 2 Another complicating factor that is left out here is the effects of scale. Smaller airfoils do not work as well as larger ones, and the flow will go turbulent, eg stall, at a lower angle of attack. This is actually due to the viscosity of the air, something that is so low that we are not usually aware of it. Reynolds did some work on this, and we can calculate a Reynolds number for any given case...for wings this is determined by the chord and the speed. Wings with the same Reynolds number will behave the same, eg give the same lift coefficient and stall at the same angle. This used to be used with wind tunnel testing by testing a small model at a higher speed, which will give the correct results. There is a limit, since if the test speed starts to get too close to the speed of sound compressibility effects will cause problems. Anyway, that is enough for now.. John