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Piers Bowlan

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Piers Bowlan last won the day on June 19 2022

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  1. So what part of your SC400 radial failed Jon? I only ask as I have an ASP400 radial I bought from Hobby King yonks ago but never run! I bought it to go in a World Model crop duster but life got in the way! What fuel/oil ratio would you recommend if I ran it?
  2. All wings can stall if their critical A of A is reached or exceeded, even ‘unstallable’ ones. At the point of stall if any yaw is present (out of balance) one wing will stall first causing a loss of lift on the ‘trailing’ wing. The wing will drop causing the angle of attack to further increases on that wing with a consequential increase in drag and more yaw... The result is that this doom-loop causes the aircraft to auto-rotate into a spin, ultimately. Some aircraft are benign while others exhibit ‘viscous’ characteristics at the point of stall, depending on their design. Some don’t want to spin, simply transitioning into a spiral dive, while others are very reluctant to come out of a spin without very positive action by the pilot. For instance tapered wings, thin wing sections and an aft centre of gravity can all exacerbate ‘tip stalling’. Also, if any warp in the wings is present or other misalignment of tail surfaces and miss match of the wings respective weights, will increase the likelihood of this unwelcome behaviour. Watching a slow flying lightweight model can be very absorbing but if it is allowed to get too slow or the wind changes direction/speed it can result in a departure from controlled flight. Modifying the design, washout for instance or moving the c of g forward can improve things but keeping one speed up is a good thing too!
  3. Konrad, with or without winglets the Boeing 747-400 (B744) didn’t experience wing flutter. I don’t know why you think it has a low Mcrit either when it is M.83, the B737-200 is M.615. Mcrit (critical Mach number) is just the point at which part of the airframe experiences sonic airspeeds, usually the wings although I think above the flight deck was one area in the B744’s case. Above Mcrit there is an increase in drag and fuel burn due to compressibility effects. Incidentally the B744 was designed to cruise at M.86 although we normally cruised at approx. M.84 as it was more economical, the actual cruising speed determined by the FMC on the basis of weight, altitude and temperature. Alternatively, schedule regularity might determine your chosen cruising speed. A more important speed was MMO which is the maximum certified Mach number (M.92). If you found yourself flying in significant standing wave the aircraft could quickly accelerate towards MMO requiring swift action to close the thrust levers and even pulling out some speed brake on occasion (a 400 tonne 600mph glider!). The auto-throttle could be slow to react. If MMO was exceeded, the high-speed clacker was designed to sound, requiring a lot of paperwork and a visit to the chief pilot’s office (without tea and biscuits!)
  4. My recollection of the Configuration Deficiency List (CDL) for the B744 was that there was a fuel penalty of 1% for each missing winglet although it might have been 1.5%. I can’t be sure as it was nine years ago when I retired and I don’t have access to the CDL now to check. My understanding is that winglets delay the formation of the wingtip vortices and reduce drag at the expense of a small about of structural weight. The B744 winglets are 1.8m high and have a similar effect as increasing the span, which would consequently cut down your choice of gate. Without winglets a 2% increase in fuel burn on a 747 LON-LAX flight might cost you an extra two tonnes of fuel, for example. So the winglets were certainly not cosmetic!
  5. I haven't built one but I do have a Ben Buckel Kit. Personally I don't think it is the spars that are the problem but the wing joiners when using larger engines. The joiners look pathetic and when I do get around to building it, it will be replaced with full-depth ply joiners. I remember seeing a Super Sixty clapping wings over Epsom Downs many years ago. Such a same to witness the demise of such a fine model. Yes, use several rubber bands to secure the wing to avoid tears too!
  6. That is a shame, I enjoyed the video. In my rare dealings with the CAA (full sized aviation) they are pragmatic, sensible people. Please don’t waste their time with reports of ‘I lost sight of my model for a couple of seconds, down wind in low cloud’.
  7. Barracuda, definitely an acquired taste. When it comes to ugly aeroplanes I prefer the Blackburn Firebrand. (thinks… I must finish mine!) at least it has a ‘proper’ undercarriage.
  8. I have had a Skipper, Libelle, and Multiplex foamies attacked by mice in my garage/workshop. I used to catch them in a home-made bottle trap and release them outside but they loved it so much they kept coming back! Every morning I would find a cross looking mouse drumming his fingers on the inside of the plastic bottle waiting to be let out! Now I use less humane bate boxes and the model attrition rate has fallen significantly. ☠️
  9. If you do find a matching female connector to plug into your motor, you will still have to solder it to the pcb of your Rx. The key to painless soldering, in my view, is 1) make sure wires, pcb and your iron is clean 2) buy a quality iron of the correct size and wattage 3) use leaded pre-fluxed fine solder wire 4) practice a bit to get your hand in 5) with a hot iron solder quickly. 6) is 1) again… check everything is clean! My 2p worth. Good luck 🙂
  10. I’ve seen that too. Pilot desperately hanging onto wingtip while pilotless aeroplane goes round in circles. Bit like full sized control line! 🤣
  11. In a previous life as a flying instructor I always taught my students to never touch the propeller. If they had to turn the engine over always to treat it as if they expect the engine to start, even if they had checked the mags were ‘off’ not ten seconds before. A simple bad connection could make a mag live even when off.
  12. Maiden flight of my KK Conquest glider many moons ago. Dad and I took Mandy our neurotic wire fox terrier with us, - what could possibly go wrong? The model tracked up the tow line like an arrow, manically chased by a barking Mandy. I had an inkling this wasn’t going to go well as the little model slipped off the line. Eventually, as it returned to terra firma Mandy tore round and around in circles getting totally tangled by the cotton line and eventually dancing all over the model excitedly. It didn’t do a lot for the delicate tissue covering and in fact the glider was never the same again!
  13. Probably because the pilot thought, ‘What can possibly go wrong?!’ Back in the day I had a D31 Druine Turbulent. I carried a small pair of lightweight chocks plus a double spike to pin the tail skid to the ground to stop the aircraft tipping onto its nose when I swung the prop. No broken props or fly aways in my ownership fortunately. 🙂
  14. My club has the use of a lake for water planes so no problem with crop rotation and you can always land and take off in any direction. 🙂 So what sort of helicopters do you fly Flybar? I had a dabble with them a long while ago. Fun but I am sure they are much, much better now.
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