SEMAC NEWS. Newsletter Of The South Eastern Model Aircraft Club Inc. July - August In This Issue

Transcription

1 SEMAC NEWS Newsletter Of The South Eastern Model Aircraft Club Inc In This Issue SEMAC General Meeting Tuesday 6 August- 8pm Dingley Community Centre Mario s Ramblings...2 General Meeting Notes...3 Seagull MXS-R ARF...3 Topflite Piper Arrow - Part Aircraft flight tracker link...4 Mosquito construction link...4 ESM Douglas DC High Tech Quad Copters...5 SEMAC Trader...6 Racer Cat Extra Part Determine a Model s Power Req ts...8 The Little Glider...9 Zero!...9 Dragon Dancer Using Two Receiver Batteries or BECs Book Review Airships Since DIY Wing Incidence Meter Last Light!... 15

2 Front Cover Brendan Perry s electric ducted fan Mirage goes vertical. Painted in RAAF training colours the Mirage, recently acquired from David Shearer, joins Brendan s already formidable jet fighter squadron. You can out find more about this interesting aircraft s background in the November - December SEMAC Postal Address PO Box 4189 East Burwood Vic 3151 Mario s Ramblings - July 2013 Dear SEMAC members, Hope you re all well and enjoying some great winter flying having had some great weather recently, just hope it continues into Spring... After my first year in the President's chair I m still learning the ins and outs of running a club and will be happy to go on as President of SEMAC after the Annual General Meeting in August and continuing the learning curve. Presuming no one else wants to take the job on!! I urge all members to come along to the SEMAC AGM in August. Again this year we need some of you out there to really consider nominating for a committee position, to ensure our club s future and support the ongoing works for a better club for all of our members to enjoy. Not all of the current Committee will go on, with just recently three Committee members resigning due to issues beyond their control. I would like to take this opportunity to sincerely thank all members of the committee for their support and hard work over the last year. I'd also like to thank John Andrews for the great work as Editor, who has done an incredible job in the past years, and wish John all the best... See you at the AGM and I m sure you will enjoy another great newsletter... Regards, Mario Agius (Pres. SEMAC) South Eastern Model Aircraft Club Inc. PO Box 4189 East Burwood Vic COMMITTEE President Mario Agius magius07@tpg.com.au Vice President Peter Short This Issue s Contributors Many thanks for their excellent contributions, to Mario Agius, Justin Cooper, Gary Curtis, Alex Evans, Greg Hewish, John Julian, Graeme Lewis, Mark Limpus, Geoff Mulhall, Richard Stolinski, Colin Vandersluys and Odath Weerasinghe. Secretary Treasurer Richard Stolinski richard.stolinski@me.com Rod Clipstone maria.clips@live.com Committee Members Graeme Lewis Ron Paine Colin Vandersluys Webmaster Michael Turner webmaster@semac.org.au Editor John Andrews editor@semac.org.au Assistant Editor Ian Hunter HYPERLINKS Hyperlink safety can t be guaranteed, so please make sure you have a good internet security system installed before you click on any of those provided in this issue. SEMAC Annual General Meeting Tuesday 6 August - 8pm Dingley Community Centre Marcus Rd Dingley 2 641A Nepean Highway, Carrum Phone Visit SEMAC s website, courtesy of Webmaster Michael Turner.

3 Notes From The Last General Meeting President Mario Agius welcomed fifteen members to the meeting held on 4 June Committee Meeting Minutes Matters discussed at the Committee meeting held on 30 May included: SEMAC membership renewal fees for the 2013/14 financial year: - Senior $300; - Pension Card holder $132 - Junior $130; - Associate $25. New member joining fees: - Senior $400; - Junior $180. Sunday morning sausage roster, including the possibility of funding one person to supply each week. Possibility of selling or raffling the club trainer at the next club event as it s not being used. Car boot sale, possibly combined with Cub Day in Sept/Oct, including lunch. Water tanks to be emptied on runways. Required maintenance, including building cleaning and painting and toilet emptying. Newsletter editor and committee nominations. Safety incidents at Geelong and MARCS clubs. Bomb Award nomination. Sound level meter purchase agreed by committee to replace the old unit. Mario is to check the standard and investigate purchase costs. Colin Vandersluys is to put together a flier to seek feedback from membership on new field options Committee Meeting Follow up Sound level meter will cost $180 based on Mario's research. Graeme Lewis will apply to the City of Dandenong for a grant to fund. Fees discussion as per schedule in the committee meeting minutes. Club trainer discussion. Member consensus was to sell one and keep the other. Roger Puehl is to be asked who donated one of the trainers. Cub Day discussion. The second weekend of August was proposed, a date that would not clash with the Shepparton large scale event AGM - a notice form and 2013/14 nomination forms were circulated. Alex Evans has nominated for the position of Newsletter Editor. Richard Stolinski announced he would be stepping down as Secretary, due to impending long overseas absences over the next 18 months. Correspondence: In from the VMAA, detailing the 2013/14 fees. Treasurer's Report Treasurer Rod Clipstone tabled the financial report to 30 April. The club had 85 members at that date. President's Report Mario suggested a working bee is not required at this stage as the field is in good shape. However painting is being planned for club buildings. Safety incidents at other clubs were reviewed. General Business Alex Evans suggested a scheme to share shipping for mail order purchases. Suggested that members could put their names on the board in the pound. Richard Stolinski is to enquire if there will be a Model Engines warehouse day this year. Show and Tell Graeme Lewis presented his Dragon Dancer, as built from RCM&E plans. John Julian gave an indoor micro model presentation. You can click on to find out more about indoor flying. These notes are my summary only of the meeting s minutes as taken by Secretary Richard Stolinski. They are not the complete meeting minutes. Editor Seagull MXS-R ARF Justin Cooper with his big and very swish Seagull MXS-R. The 1660mm (65.4 ) wingspan model comes with gas or electric motor mounting options - Justin opted to go electric. Justin reckons it was a fairly straight forward build, but he s fitted larger wheels, upgraded pushrods in the tail and a couple of mods to aid in cooling. He s found it to be a great sport aerobatic plane, although not a 3D ship by any stretch. It does huge loops with the present setup. The wing loading s not known but it floats in for landings. Click on vimeo.com/ to see it in action down at SEMAC Field. As it happens, Justin s MXR-S is up for sale. See The SEMAC Trader for details. John Julian photo. 3

4 TOPFLITE PIPER ARROW PART 5 After a long hard haul, Gary Curtis very sharp red and white Arrow is ready to fly. t last the project is finally finished - only taken There were panel lines as a stick on transfer which A twelve months to complete. The wing has finally came with the kit, and these were placed on the wings been covered and what a job it was too, red and white and fuselage as well and the effect was not too bad. covering finished off with gold pin striping around the I finally got the Robart wheels to match from a hobby outer wingtips which matches the stripes on the fuselage. shop in Canberra, as no stores in Victoria had them. It I fitted wheel outer door covers to do something looks better with the scale wheels. different seeing I did not put retracts on, but the effect Overall the final result was pleasing so I hope you like looks quite good. Finished off the grooves in the ailerons the finished product. and flaps which came out looking not too bad, but a heck All the best till the next project, Gary Curtis. of a job to finish. Nylon bolts go through the belly pan, which is attached underneath and holds the wing on to the fuselage. I finished off the body using an artist black scribe to give the look of doors on the cabin. A steady hand was required for this step as one mistake makes it hard to get the ink off. The Arrow, ready for its maiden flight. Twelve months work, but well worth the effort. G Curtis photo What s that aircraft overhead? Until Odath Weerasinghe sent me this link, I d heard how you can track the progress of aircraft in and out of airports world wide, but had never tried it for myself. Just click on any aircraft symbol to follow it s progress. There s a heap of information available, including cockpit views from some flights. You reckon you build big models Another nice link from Odath, this one a 1940 s newsreel showing Mosquito manufacturing. Very interesting video and soundtrack, finishing off with footage of the Mossie in flight. Quality is not too bad, although pretty grainy if you go to full screen view. If you re thinking of building one, I suggest you have a talk with a friendly Heavy Model Inspector first. Jets inbound from Tasmania come right over the top of our place and I ve always wondered about their altitude and airspeed. Now I know - around 8,000 and 260Kts. Be warned though if you haven t looked at it before, it can be a bit addictive. 4

5 ESM Douglas DC-3 Mario Agius is setting up what is certain to be a marvellous aeroplane - his new 103.9" wingspan DC3. F or a long time now I ve been wanting to get a twin engine model, something I could fit two small petrol engines in. After doing some research I couldn't go passed the DC3, which is generally regarded as one of the most significant transport aircraft ever made, So I purchased an ESM make DC3 from Austar. It has a wing span of 2640mm and is1790mm in length. Not too big that it wouldn t fit in a small car and able to fit a couple of Mario and his magnificent big ESM model. Click on the link if you d like to see a similar one making its maiden flight from a very dodgy looking strip. High Tech Quad Copters 20cc RCGF engines, it was the perfect choice. Unfortunately I had to make room, so the Sea Gull Pilatus PC6 had to go. The DC3 will need a heavy permit to fly and should come in at about between nine and ten kilo s. The fuselage and the middle section of the wing that houses the engines and landing gear is reinforced fibre glass with built up outer wing panels. The wing is supposed to be glued in one piece, but I ll be modifying it to have the outer wing panels removable for transporting to the field. The engines will be two RCGF 20cc SBM (Sport Beam Mount). These are beam mounted like a glow engine and only weigh 785gms including ignition and muffler. At 2.8 HP these engines are lighter and more powerful than the recommended 120 four stroke and very economical. The model requires a total of eleven servos: two for throttle, two for ailerons, two for elevator, one for rudder and four for the flaps. I won t be using a power expander from the receiver to servos, but instead will be using two receivers - one for the left side and one for the right, independent of each other with their own battery and switch Hoping to have it done in a couple of months ready for Spring Keep flying, Mario Alex Evans and Richard Stolinski both sent me links (from different sources) to this video clip showing high technology quad copters in action. Raffaello D Andrea demos drones that - amongst other things - play catch, balance and make decisions. These are definitely not your $30 shopping centre quad! The sound track is in Hebrew, as are the default sub titles, but just click the arrow down in the bottom right hand corner to select English subtitles. I used Alex s link because the one Richard gave me was that long it wouldn t fit in this text box! 5

6 The SEMAC Trader For sale Outrunner motors and ESC s - $25 a bundle Turnigy : kv outrunner motor Turnigy : BASIC 18A ESC with BEC built in. Contact Alex at alex.evans@iinet.net.au or on Wanted to Buy Hitec Eclipse 7 36Mhz FM Radios and any Hitec extras. Please phone Des (the Sunday Cook!) on For Sale Seagull MXR-S - as featured on page 3 of this issue 1660mm (65.4 ) wingspan Fitted with a Scorpion motor, 16x10 prop, a Turnigy K-Force 2-6S 150 amp OPTO ESC and 4x Hitec HS5485HB servos. $400 or near offer. Contact Justin at justin@justincooper.com.au or on For Sale 5 X Corona 939MG 12g Metal Gear Servos - selling for $15. Still in the boxes. I have tested them and all are working. HobbyKing link for these is: 1 X Tiger Motor AT 2814 Brushless Outrunner, 35-36mm, 1000KV - selling for $30. Has ~30 15 min flights on it. Comes with the metal mount and prop adapter. In ex condition. See Got something you d like to buy, swap or sell? Then put an ad in The SEMAC Trader. editor@semac.org.au 1 X Hobbywing Pentium 40A Esc to suit the AT selling for $12. As new hardly used. These are the same (identical) as the Turnigy Plush ESC's and can be programmed with the Turnigy programming card. Contact Geoff on Racer Cat 60 Greg Hewish s very sporty balsa and ply construction Racer Cat 60 ARF. Powered by a Thunder Tiger Pro 61 and with a 1600mm wing span and 1450mm length, the pattern ship look alike not only looks good, it s an excellent performer. G Hewish photo 6

7 Extra 300 Part 1 By Alex Evans ell folks, it s been a long time since I worked on a W new scratch build project. The previous one was by far too long, and after three years one can get really sick of it and start cutting corners. So, very uncharacteristic of many of my previous projects of multi motor toys, I opted this time for a single motor project, which hopefully will be in the air before the end of this year, time will tell... Running out of space in my Hangar (Yes Graeme...) I also decided to go for something more modest in size. I looked up the plans chart on Airborne magazine and picked up this one. I then found a Laser cutter, purchased the plans, which also offer cowling and canopy, and asked them to deliver the lot to the cutter, who will subsequently mail to me the whole package. Whenever you start an electric conversion for a design that was intended for an IC power, the immediate question is where to construct the battery tray, so that the battery will place the model into the correct C.G for flight, without the need for any dead weight, which I personally dislike and try to avoid whenever possible. I received the short kit at the start of May 2013 and started looking at the bits. There were several omissions, missing parts and in several places the cuts for the longerons didn t correspond to the slots in the fuselage formers and I had to cut those by hand. Not sure about the level of quality control that went into this job... I decided to start with the fuselage (although the Instruction manual says to start with the wing). Being an electric conversion, it is clear immediately that the Firewall will need to be extended forward, so that the prop will be located outside and ahead of the cowling, here is how it looks at this junction. into a servo tray over the wing as per the plan, or should I place those inside the tail closer to where they are needed and through this attempt, also balance what looks to be at this point a very heavy nose... It is a chicken and egg scenario I will know better only after installing the tail feathers, but by that time it will be very hard to position the 2 servos in there... Another challenge is of course to try and figure out the expected AUW, so as to be able and match the correct power setup to it. I made a guess of 3.5Kg and decided on an AXI 4120 / 14 which I had in my spare motors box, time will tell if my choice was correct. Moving on, I decided to construct the tail feathers and once those were done, I placed those into their intended location to see what the C.G looks like... Well, with those in place, the cowling set into position, the prop and spinner attached and the flight battery in the battery tray and the aluminium undercarriage attached... Hurrah... the C.G looks so good, now I can proceed to place the 2 servos in the intended location, under the canopy! That is indeed a much more civilized proposal... Constructed a light ply tray in between formers 4-5 with some support underneath to also strengthen the fuselage at this critical location, cut the two slots for the normal size servos and installed two snake conduits into the tail, with some extra support along the way, to reduce any chance of binding... OK, now that this is done, I am getting closer to being able to start sheeting the fuselage. Just one more step before this can take place. The motor mount is some very nice and light stainless steel job, I think I received some years ago from Mark, thanks buddy, it seems I have eventually found some use for it. Back to the C.G issue there is a need for 2 servos to drive the rudder and elevator, right? So, should they go SEMAC Annual General Meeting Tuesday 6 August - 8pm Dingley Community Centre Marcus Rd Dingley Melway 88 F6 7

8 I need to make an electrical main power harness / extension from where the ESC is located behind the motor and all the way to where the battery pack will be placed. As I also tend making a power Short outside the fuselage, to facilitate the battery being connected and installed without a need for further fiddling at the club. I just have a U type connector that plugs in from the outside and that arms the model. This is a bit more construction time but easier operation long term, common... you know already that there is no such thing as free lunch! I am using this one to do the trick: The one on the left sits inside the fuselage with the RED battery pack wire cut for IN/OUT and sticks out of the fuselage side for a bit of support while the one on the right is what I use to make the U type connector. So, I install the battery, and leave the U plug in my pocket until I am ready to fly. Simple, and as my flights are relatively short, I can have several flights on that same pack, without the need to disconnect the battery in between sorties. OK, that s done and no more excuses delaying sheeting the fuselage... But, just before starting, I look at the plan again and notice the following: of the nylon bolts that will hold it... Those two are supposed to be at 90 degrees to each other, or else the bolt will never be screwed into the blind nut and finding out about it AFTER the sheeting is done, will be a bit too late. So I started scratching my head again! I don t have many choices here, the wood holding those blind nuts must be positioned as per plan in their slots already cut in the fuselage doublers (ply). The wing trailing edge will have to be elevated from underneath so as to form a parallel line with the nuts surface above it, it will be tricky no doubt... OK, started sheeting and now another head scratching. The plan calls for 3mm balsa sheeting. This thickness is very convenient for getting a nice finish there is a lot of material you can sand down to get the rounded shape, but it also adds more weight. So, I used 3mm in some parts of the tail section behind the turtle deck and opted for 2.5 mm on other parts. It seems now that my fears are that it will be tail heavy (as opposed to my initial thoughts about it being nose heavy), so I must minimise the amount of weight I am adding to that section. Here it is at this stage of the story... This is a side view of where the wing is supposed to be attached at its trailing edge. Do you notice anything strange? I do. Notice the angle where the blind nuts are supposed to be installed and compare that with the angle One immediate problem I had was in that I needed to actually apply the covering material to the elevator surfaces, before I was able to finish the tail section. The reason? The elevator is to be installed WITHIN the vertical fin, and the vertical needs to be glued in place so as to add the balsa blocks that form that end of the turtle deck... And before I go, Thanks Graham Stevenson for the second hand tail wheel... Fly safe, Alex Evans Determine a Model s Power Requirements Building a new electric model and not sure what power system it will need? Then follow the link to read how to calculate the power requirement for any given weight or type of aeroplane (just the first few paragraphs shown here). The link, to one of a handy series of articles published by Horizon Hobby s E-flite, was sent in by Geoff Mulhall. 8

9 The Little Glider The Wacky Waco, AKA Colin Vandersluys, takes a trip back to a time long ago and far away. he voice called how you agoin Mr Col as it T came up the drive (which is uphill) to my garage-workshop. It was Leo, my friendly neighbor from up the street. OK, says me, better to be above the grass than below it. Iva beena cleaning upa garage, says Leo, and I finda this box. It isa model aeroplane which you make. I donta know where it came from but I thinka of you and thinka you might like to be building it. Leo handed me a dust covered box - it was a very old Aeroflyte Heron glider kit. Thanking Leo we talked a while and he was off back to his garage. A few Sundays later it was wet, no flying so after lunch I decided to take a look at Leo s kit. The balsa was still in good condition as was the tissue, the plan and the glue after possibly 40 to 50 years. I decide to build it using cyno glue for a quick build. The glider was much smaller than I thought, however, what the heck a bit of fun. By tea time (phew, five courses) the construction was finished. As I was writing I had not decided what to cover it in, tissue or plastic. I think I will add some light aluminium trim tabs just in case they may be needed. The box also contained a tow line so maybe at the club I may try to fly my little glider and report back to Leo. John, I would like to thank you for producing an excellent newsletter every two months and I hope you will continue to subscribe to the new one with your top class photos - from an appreciative member. The Wacky Waco (Colin V.) Zero! Andrew Battersby s little Zero, very fast and very low along the flight line. Never ceases to amaze, just how well the current breed of little foamie fighters perform. So little cost, so much fun! Mark Limpus photo. 9

10 Dragon Dancer 2 A very stylish aeroplane, scratch built by Graeme Lewis from a RCM&E magazine plan. ontinuing on from my last article, C the Dragon Dancer 2 is nearing completion. Built from an RCM&E free plan supplied with the December 2012 magazine, I have added some changes. The heading that caught my eye said.25 Sport Aerobatic Free Plan so I bought the magazine. The original power was advertised as a.25 nitro, then the plan said.32 nitro and then the article s author said he was fitting a 40 size engine. Totally confused, as were many others in various forums I looked at, I decided to cross the line and go electric and get a best fit solution which also had some challenges. To find a motor and power system that was around a 32 size, and replicated a.32 nitro, presented some problems for me. But after consulting the electric gurus at the club and taking a punt on a best fit arrangement, it was decided that a Propdrive 35-48, 900kv, motor and a 60 amp ESC, powered by a 4s 4000 Amp hour LiPo and driving a 10 x 7 electric prop would work. At this stage the wing and fuselage were built so when the parts arrived from HK some revisions were required. To try and place the prop in the same position as the nitro version, I had to add a box to the front firewall. This as it turns out will also be used for the cowl fixing. The fuselage is nearly the same as the plan except that it is around 15mm narrower and bulkheads have been modified to fit a LiPo battery. The 4s 4000mAhr battery, by luck when it arrived, just fitted the fuselage width. I have also changed the canopy, which on the original was a simple sheet construction and was not removable. I vacuum formed my canopy and constructed a one piece assembly that is now removable for battery access and connection of the power. The wing is built up using conventional construction methods with a location tag at leading edge and a centre retaining bolt to hold the wing to fuselage. There is an aileron servo inserted into the wing each side. It is a tail dragger which will be my first, so it may be a challenge and to some degree limits the size of propeller that I can use. The all up weight at the moment is around 1.7Kg and with a wing span of 1150mm is a nice size plane. I have covered it with film and the cowl is a molded fiberglass assembly. For the first time I used plaster bandage to construct a two part mold over a carved plug and the result has been really good, as you can see with only a little finishing required. I have not balanced the plane as yet but it does appear to be tail heavy and may require some front end weight. A 40 size nitro motor is heavier than the electric assembly so some compensation will be required. The author said his nitro version s flying weight was around 1.75Kg so I am not far out with total weight but the C of G, which is supposed to be 70mm RIGHT The Dancer s power system and complex moulded cowl. It s got a turbo prop look about it, don t you think? BELOW The finished product. You can be assured that anything that looks this good will fly real well! G Lewis photos from the leading edge, needs adjustment somehow. Just a warning. My Dragon dancer is way tail heavy when built to the plan. I have needed to add 50mm to the nose length so I can move the battery and motor forward to allow balancing at 70mm behind leading edge. So build light at the back end. Google "Dragon Dancer" and you will end up at the RCM&E forum, where there is an electric conversion and a little idle chat about the plane. 10

11 Using Two Receiver Batteries or BECs Like to fit your aircraft out with a more reliable power supply? John Julian tells us how. It s almost certain that the majority of radio failures these days are actually power failures. When working, the 2.4GHz radio link itself is very reliable. From the earliest days of 2.4Ghz systems, Spektrum identified the #1 problem encountered as inadequate power supply. Unlike 36 MHz analog, where servos slow down but receivers may still operate at voltages as low as 2.5 volts, the digital microprocessor systems used in 2.4 GHz receivers completely shut down at a specific voltage - often as high as 3.2 volts. In short 36MHz slowly degrades; 2.4GHz suddenly stops. Modern systems are often more tolerant of lower voltages and will reboot very quickly if the voltage rises again but nevertheless low receiver voltage is a serious problem. Digital servos have made it worse since they can draw very large currents for small movements so that the total current drain on the battery or BEC can be high even during normal flight. Just a momentary voltage drop can be enough to cause the receiver to reboot. It is commonly called a Brown out. Big models often use redundant systems with two separate switches and flight packs and sometimes sophisticated monitoring systems like a Powerbox to monitor battery health. A similar idea can be implemented very simply and cheaply for smaller models as well. It is OK to connect two NiCad or NiMH receiver batteries in parallel if they are the same voltage, type and capacity as long as they have the same state of charge. In fact some receivers have two dedicated battery connectors just for that purpose. The idea is that each pack shares roughly half the load and if one pack fails the other will continue. Problem is that if one pack looses a cell or otherwise drops in voltage the second pack spends its time trying to charge the failing one rather than power the receiver and servos. Actual battery failure by shorting internally is a very low risk but connecting up a fully charged and a discharged pack by mistake may not be! It is not OK to connect two BECs in parallel, and most people know to disconnect the red power lead in the throttle lead from the ESC if it has a built in BEC and you use an external one. But why? The problem is that a BEC, unlike a battery, is a fairly precise constant voltage device. If two BECs are connected in parallel and their output voltages are even slightly different, the higher voltage one will continually see a lower load voltage and the BECs will fight one another. Both the dying battery and dueling BEC problem can be very simply solved. The idea is to isolate each battery or BEC from one another but not from the load. All that is required is two diodes. A diode is an electrical one-way valve. It allows current to flow through in one direction but not the other. RCGF Engines Aust. Like us all to see or hear about your new model or equipment in a future issue of? Let Alex know at editor@semac.org.au or disk only thanks. 11

12 m.html? _odkw=&_osacat=0&_armrs=1&_ssn =uk.deal&_trksid=p m570.l1 313.TR0.TRC0.XMBR1545CT.TRS0&_ nkw=mbr1545ct&_sacat=0&_from= R40 The illustration above shows the idea: The blue arrows show the only way the current can flow through the diodes. So current can go through the red supply wire to the receiver and servos from either battery but it cannot go back into either battery from the other. In practice if one pack is a higher voltage than the other it will supply most of the current until the voltages equalize, then the two packs will share the load. With two BECs it is different. Normally one BEC will have a higher voltage than the other and will supply all the current. If it fails then the other will instantly take over. My measurements show that if the two BECs have very similar output voltages they will share the load between them but you would not normally count on this. So each BEC needs to be able to supply the full current. But there is a catch. The diodes themselves absorb some of the voltage. A normal silicon diode will have a voltage drop of about 0.6V between input and output. So your 4.8V flight pack only supplies 4.2V, which is very low and it will be even lower under a reasonable load. Fortunately a slightly more expensive diode design called a Schottky diode has a voltage drop of V depending on the current and this may be acceptable. Normally however, using Schottky diodes is reserved for 6 or 6.6V flight packs. With a BEC it matters less as the voltage is constant and does not fall during discharge like a battery. A 5V BEC will normally deliver close to a constant 4.8V with a Schottky diode in circuit. I found that at a 2.5Amp constant current the diode used in this circuit drops almost exactly 0.3Volts. In practice this very simple solution works very well for the common case where you have an ESC with a built in BEC that is inadequate to supply current for a smaller model with maybe 6 servos and electric retracts such as many of the newer foamie scale models. The 10-15g size digital servos pull a surprising amount of current, as they are fairly inefficient. Stall one of them - or more commonly an electrical retract unit - and the built in BEC just cannot cope. They automatically shut down if they get overloaded or overheat, and they just happen to be sitting on an ESC that is already running hot! The obvious solution is an external switched BEC with a 3A or 5A rating and the internal BEC is then normally disconnected by cutting its red power lead so it is just along for the ride. By adding a diode bridge and leaving it connected it can act as insurance and take over if ever the main BEC fails. Recently an Australian modeler with the user name Aus posted a very simple practical solution to building a Schottky diode bridge on RCGroups. Here s my version. It needs just these three bits plus some heat shrink. And here it is bottom right, in use with two BECs connected to an AR8000 receiver. You need a Schottky Power Rectifier. This is two Schottky diodes conveniently packaged in the one case. Jaycar have a version locally for $ productview.asp? ID=ZR1039 Or you can buy 5 that will do the job on ebay for $3.18 including shipping! The 6 pin connector is this 60cent one: It is called a 6 Pin degree Locking Header pitch. productview.asp?id=hm3426 And finally you need a servo lead cut from a dead servo or extension cable. Use one with a decent wire thickness as it carries all of the current for the receiver and servos. 12

13 Follow these steps to build a Schottky diode bridge. 1. Bend the pins on the diode and connector like this, cutting off one of the outer angled pins. The other one carries the throttle signal if you are connecting the BEC from an ESC. 3. Solder the diode to the connector and trim the ends. Connect the servo lead. The red wire goes to the centre pin of the diode, the brown or black wire goes to the two middle pins of the connector and the white or orange signal lead goes to the uncut end connector pin. Identify that pin with a marker pen so you know which side to plug an ESC into after it is all insulated. That s it - apart from insulating it! makes a nice moulded boot. 2. Match the pins and glue the diode to the connector with some CA. I recommend a bit of HS on the Diode metal heat sink tab. The tab is internally connected to the output pin and so is live at 5V. Given the fairly low power dissipation in the Shottky diode (about 0.9Watts at 3Amps continuous) the reduction in heat transfer isn't going to be a big issue. The two BECs or batteries plug into the 6 pin connector with the black wires in the middle. Hot glue and heat shrink make a very strong strain relief and insulation for the servo lead connection. Shrink the HS at the pin end only; squirt some hot glue in the other end. The hot glue will shrink the HS and distort it a bit but don't worry. Then just hit the whole assembly with the heat gun. The hot glue re-melts and the HS tightens up. When it all sets it The name just about says it all really. Starting with the Montgolfier brother s first manned hot air balloon flight in October 1783, Ridley- Kitts discusses virtually every airship type built, right up until the present time. The first chapter lays the ground work for the rest of the book, explaining the basic concepts involved in the design, construction and operation of lighter than air craft. I have to admit that I hadn t realised that the whole process was so extraordinarily complex! Book Review MILITARY, NAVAL AND CIVIL AIRSHIPS SINCE 1783 Daniel George Ridley-Kitts The History Press Over the rest of the book s 300 pages, Ridley-Kitts examines a very wide range of rigid and non-rigid airships built and operated across the world. And it s a fascinating account. It describes a mixture of success and tragic failure; design and engineering brilliance mixed in with examples of great incompetence; winning operational strategies tempered by political and bureaucratic meddling. Many lessons were learnt the hard way, often at great monetary cost and with seemingly only limited regard for the safety of the flight crews. Much space is given over to WW1 military use, including the successful use of British airships for naval patrol and anti submarine warfare, and the largely ineffectual Zeppelin bombing raids on England. The story then continues with civil use during the inter-war years and WW2 military applications - predominately patrol duties along the US western coast line. There is finally a fairly brief coverage of the use of modern non rigid airships for commercial purposes. Included in this excellent book are a great many excellent line drawings and good quality photographs. A book I thoroughly enjoyed reading and one I would highly recommend to anyone who would like to learn more about the era of the great airships. 13

14 Testing This thing works with any combination of BECs and batteries. I tested it with both two batteries and also with two BECs. Using a NiCad and a NiMH 4.8V receiver pack at about equal charge I got 0.95Amps from the NiCad and 0.73Amps from the NiMH into a 2.0 Ohm load. So the two packs were sharing the load fairly evenly. Using a single NiCad Rx pack and then adding a 6V BEC the current taken from the NiCad instantly dropped to zero as expected as the BEC took over. Using a single 5V BEC I got 2.23A. As soon as I attached a 6V BEC the current from the 5V one dropped instantly to zero. When I attached a second 5V BEC instead of the 6V one, the current in the first 5V BEC dropped to 1.75A so it appears that if the BEC voltage is fairly close you get some load sharing. The output voltage values were exactly as expected - being the highest of whatever sources were connected. And finally, with a bit more work you can add a couple of indicators that will only illuminate if the supplied voltage is adequate. Tells you if both supplies are working OK. I made one with two LEDs and two Zener diodes that does just that. TOPLEFT With a 5V BEC only. TOP RIGHT With a 6V BEC only. MIDDLE RIGHT With both connected. The 6V BEC takes over automatically. ABOVE For just a little extra effort you can add a pair of LED voltage indicators RIGHT I don t know if John s installed two batteries and/or speedies in his balsa and ply construction Fieseler Storch ARF, but it s none-the-less a very striking aeroplane All photos J Julian 14

15 I ve heard a couple of people lately commenting that their aircraft needed a lot of aileron trim to keep it flying straight. While there can be many causes for this, very often it is the result of a warped wing, perhaps built in during construction, assembly or repair. Warps can often be corrected using a heating iron or gun, but it s a bit hit and miss unless you use a wing DIY Wing Incidence Meter incidence meter to monitor the process. The one shown here was featured in some years ago. Designed by Michael Devenport of the Basingstoke Model Aero Club in England, it s quick and easy to build. I made one myself and used it to help stop an old Auster almost turning itself inside out. Cheaper than a store bought one as well. All parts were cut from a sheet of 3mm ply with a Stanley knife and straight edge. The slot in the scale arm was cut by drilling two 3mm holes and then joining with the Stanley knife. The pivot points are all 5mm holes with bolts and nylock nuts, and the centring pin is a 3mm screw as in the section AA. All holes and the slot were hardened with CA to improve wear qualities. Angle Of Attack Meter To use the meter, level the model with the tailplane as a reference using the incidence meter or a spirit level. Clip the incidence meter onto the wing and read off the angle of attack of the wing from the scale. Last Light! I m not sure whose aircraft this is, but it s a wonderfully evocative image, captured by Mark Lumis. 15

16 Up, Up. uite a few years ago, I was Q instructing a student at our old Greens Rd field when I allowed him to fly his trainer just that little bit too far down wind. At about the same instant we both realised that the little high winger was no longer under his control. On grabbing the transmitter it didn t take long to figure out the aeroplane was out of range - and getting both further away and closer to the ground. While I was trying my hardest to dampen out the thing s by then fairly wild gyrations, I could hear the now late Gerry Enery screaming at me from the pits UP, UP. I was inclined to take offence at his advice and screamed back at him WHAT DO YOU THINK I M TRYING TO DO?. At this point, Gerry calmly (and gently) made me aware that he was referring not to the aeroplane, but to the transmitter. On raising the 36MHz transmitter as high above my head as my trembling knees (Elvis knees, as Gary Curtis calls them) would permit, control was miraculously regained and the model safely brought home with smiles all round. Why am I telling you all this? Well, as it happens, I had a repeat episode just a weekend or two ago as I was cruising my Wanderer electric glider at a reasonable height out to the north west of the field. It was a cool and sunny Sunday morning, with a light easterly breeze, very buoyant air and some modest patches of lift. Getting a bit carried away with the sheer pleasure of it all and not paying anywhere near as much attention as I should have to where the glider was, I eventually developed a very nasty feeling that perhaps the aeroplane had gone on to auto pilot. That it had gone into a kind of constant tumbling tight turn was my first clue. After a short period of waggling the sticks, all to no avail, and watching the Wanderer gradually disappearing in the general direction of who knows where, Gerry s words came back to me. Up went the transmitter, more stick waggling, and the glider straightened out and started to steadily get bigger. Phew! The Wanderer on short final for the north south runway. I wasn t sure that the old trick would work with a 2.4GHz rig, but apparently it does. Either that or me old mate Gerry reached down and gave the Wanderer a little nudge back in my direction. and Away After putting together seventy two issues of our newsletter, it s now time to hang up my typewriter. Well actually it s a computer keyboard, but I guess you know what I mean. For the many, many people who have contributed articles and photographs I offer my heartfelt thanks. You are the heart and soul of any newsletter and without you each edition would have been very thin indeed. To those members and other readers who have simply offered me encouragement along the way, I thank you also - it has always been very much appreciated. 16 Mark Limpus photo. And now I m leaving you in the very capable hands of Alex Evans. As well as being a most prolific contributor over a good few years, Alex edited the for a couple years in the middle of my stint. I m sure you will appreciate his future efforts and know that you will give him the support that you have always given me. For those of you who have been around for a while, the very first thing you would have seen when you opened the September issue of the then DKRAC News was the marvellous photo shown below. Taken by Colin Vandersluys, it shows his Steerman on the helicopter apron at Moorabin Airport and was published, of course, in glorious black and white. I thought it was a fitting way to close my last issue. Enjoy your flying, and I ll see you down at the field. John Andrews