Peter Jenkins

The other useful tools to play games with are different kv for the equivalent power motors and prop pitch. A higher kv will allow you to use a smaller diameter prop with a higher pitch to get the same power. It is quite common for an electric prop to use a higher pitch than you would for an IC solution. As an example, I bought a second hand 70 size aerobatic aircraft that had a Hacker motor with a 425 kv. It was intended for a 6S pack. I wanted to use 5S packs and ended up putting a 17x12 prop on that gave the performance I needed. However, changing to a motor with a 580 kv allowed me to bring the prop diameter down so a 16x10 prop gave the required performance as it was turning faster. It also gave me an extra 1/2 inch of ground clearance that made all the difference in preventing the grass being cut on take off! The aircraft is a tail dragger though.

As Brian Habana said on the radio this morning, there is always a 50:50 chance of winning a game with 2 teams playing. It comes down to who makes the fewest errors during the game and which group is more cohesive on the night! The wonder/fascination of sport!

Well, thst should have been the final. I can't see England beating SA and NZ have not been at this level for at least a yearnor more. SA to win the tournament.

Least they won unlike the cricketers who lost yo Afghanistan for gawds sake!

Well, Dupont is taking a risk going into battle against SA so soon after surgery! Tough guy!

Hot off the press! This evening, someone bought the 1,000 th copy sold of my book from Amazon Germany. My book has been bought in 10 countries around the world despite it being available only in English. Sales through Amazon are 530 paperbacks and 327 Kindles, while I have sold 143 paperbacks. This has surpassed my wildest expectations. However, it also means that 1,000 folk think enough of it to buy it! If you would like a paperback copy then please send me a PM with your name and address. I still have 3 copies available at £18.99 posted first class for UK addresses but will get a quote for sending you a copy if you are outside the UK. If you want a Kindle, please buy that from Amazon. Once I have sold my existing stock of books, I will have to charge £21.99, incl first class post for the UK, to cover the increased cost of printing being charged by Amazon. Note this is a little higher than the £21.68 I quoted in the post immediately above.

Looking ahead, England really ought to beat Fiji. After that, I have my doubts that they will win a semi final as they will be up against either France of South Africa. France v South Africa looks like being a very difficult one to call. To me, it rather sounds like the final! My feeling is that whom ever wins this encounter is favourite to win the RWC. NZ ought to beat Argentina but unless NZ can up their game I cannot see them beating either of France or SA. Based on what I've seen so far, I would say the final will be between either France or SA vs New Zealand with NZ losing!

I didn't say or imply that. I saw a video of an All Black piece of cheating where one of their jumpers at a line out jumped sideways as if he'd been pushed out by the opposition - England as it happens. NZ were awarded a penalty, scored and won the match. There was no video referee in those days. When asked if he would do it again the AB said "Yes". That's what I mean! By any standards, that is blatant cheating. This is a game with rules not war.

Impressive response by Ireland and good to see NZ penalised for foul play. They are very good at hiding their misdemeanors!

Yes, I'm well aware that the XG11 is still available as the T44 at under £1k but does not offer anything better than my current XG11. As I said, for my purposes, F3A aerobatics, the XG11 has been able to meet every demand I have made of it. I currently own 2 x XG11 Txs and will shortly acquire a 3rd so I should be fine for the next 10 years. OTOH I might be tempted by the new Elite Tx if I feel the need for extra functionality since I could continue using my existing JR DMSS Rxs.

Just like to make the point Martin that the JR to which you referred will be the DSX9 and DSX12 versions that utilised the Spektrum radio system - DSM2. I had a DSX9 and it was fine except for 2 occasions when the Spektrum Rx equipped aircraft suffered some sort of radio failure and I lost the aircraft. The second loss was my 10 flight old Sebart Wind S 110. At that point I changed to the full JR system, that is the XG range of Txs, an XG11 to be precise, and have used this since 2011. The radio link, JRs DMSS, has never given any concern during the 12 years that I have used it except for one occasion when during my pre-flight check the elevator stick spring retainer broke! Thankfully, as I say, it was during the pre-flight check. Apart from that, it's been exemplary. So, when you see JR in this context it is the old JR with Spektrum radio in it not the proper JR DMSS radio designed by JR. Sadly, JR went bust due to some illegal financial jiggery pokery. I bought up some second hand XG11 Txs as a hedge against any Tx failure and picked up some Rxs to keep for new aircraft and spares. Thankfully, the JR product, or at least some of it, been resurrected by Dee Force Aviation under the banner of JR/DFA and they have launched a new Tx although it now is over £2,000 in the UK so competes with the top line Futaba, Jeti and Powerbox ranges. For those of us who had and still have the JR DMSS radios, I suspect that we will keep faith with JR but we are a pretty small group compared with the glory days of JR in the 35 Mhz era. As far as I'm concerned, the ease of programming a JR Tx compared with Futaba was what sold me on the brand and led me to move from Futaba when they delayed launching their 2.4 offerings and the JR/Spektrum DSM2 DSX9 introduced me to JR's Tx. When JR launched its own 2.4 offering, the JR DMSS system, I took that route and have never been short changed for performance or capability. Just a great pity that they had a crook working in the old JR!

That should scare a kite or buzzard!

I shall look forward to seeing that!

Well, I don't believe that what Graham has said is that application of rudder will cause the aircraft to pitch down without any yaw and roll. You know that the secondary effect of yaw is to cause a roll in most cases this is on the direction of rudder travel but, occasionally, against rudder. As soon as the aircraft starts to roll, the lift force is split between a vertical and horizkntal elements and the aircraft starts to descend as the vertical component of the lift force is no longer fully supports weight while the horizontal component of the lift force provides the acceleration to turn the aircraft. As the aircraft rolls, the rudder force now has a sideways and downward component and that will accentuate the loss of the vertical component of lift and push the nose down. It doesn't have to be much of a roll for this to happen. A yaw also increases drag, slows the aircraft and reduces lift as the airspeed is reduced. As regards the Lancaster failing to stall, it is a clear indication that there was insufficient elevator force to pitch the wing to its stalling AoA in this particular case. I have heard of a situation where the tailplane had been fitted upside down causing some poor handling but it was years before this was noticed and rectified. As regards increased downwash causing different effects with where the TP is mounted I disagree with as at low speed the downwash effect is felt quite far away from the aircraft as the flow is treated as incompressible at those speeds. Your aero boffin may have not been quite so knowledgeable.

Peter, I agree that most aircraft designed for aerobatics have the rudder area split 50:50 either side of the horizontal axis. But take a look at the Wot 4/Acrowot types and almost all the rudder is above the horizontal axis. The other point if not noticing it is because your flying skill might be automatically compensating for this design feature. However, if you fly precision aerobatics, especially in competition, you are particularly attuned to any minor "defect" in the way an aircraft flies. It comes as a surprise to most club pilots to use rudder to correct the aircraft's heading when "flying the line", indeed to using the rudder knce airborne. It may not be noticeable in their style of flying. A lot of time is spent on top rated aerobatic designs to get them absolutely spot on - 50 - 100 flights is not unusual. You notice these things when you look for perfection because you know the judges will penalise you for every minor misdemeanor in the purity of a manoeuvre. Best regards Peter

Hi Graham IF you look at the arrangement of the rudder on the Pitts, you will find that there is far more area above the horizontal axis of the aircraft taking that as the line drawn through the motor centre line. This is very similar to a Wot 4 or Acrowot arrangement. What this does is to provide a rolling moment around the horizontal axis as there is more rudder area above than below the axis. I would think that you would find that application of rudder also causes a roll to develop very easily and as soon as the aircraft rolls, unless you increase wing AoA, then the lift vector is spread between supporting weight and accelerating the aircraft into the turn. The outcome is the aircraft drops its nose as its natural stability will try and return to the required lift for level flight and does this by increasing airspeed. The KE situation is also fairly typical of this type of design. On purpose designed aerobatic aircraft, the rudder area is designed to be the same on either side of the horizontal axis. Even then, unless you move the CG quite a long way aft you will almost always get the nose pitching down in KE and also either the aircraft trying to over or under roll. If moving the CG doesn't do the trick, then we mix aileron and elevator to the rudder as master to try and fix this problem in KE. It can mean that you make the problem worse in level flight though so putting the mix on a switch will allow you to check this behaviour. On my Wot 4, it was almost impossible to fly a slow roll using the rudder and elevator to maintain level flight during the roll. As you rolled left and started to apply right rudder this caused a reduction in the roll rate you had selected because right rudder was inducing right roll. Once past the inverted stage you start to need left rudder and this induces a left roll that adds to you roll rate and speeds up the roll rate. By mixing opposite aileron to the rudder so that a yaw in level flight produced just a yaw and no roll, solved the problem. There is nothing unusual in this behaviour unless despite the designers best efforts he has failed to resolve the problem caused by the unequal distribution of rudder area above and below the aircraft's horizontal axis.

If you guys would read what I 'd written which is that I wiggle the piston either side of TDC till I fell the contra piston, then undo the comp screw by 1 turn and make sure the engine is free to rotate through TDC before flick the engine over. OK, I accept that the contra piston didn't always go up till the engine fired. I never damaged any of my engines by following this route which, as I say, was a standard method of finding an initial comp setting. I would have read that in my monthly mag, the much lamented Model Aircraft.

In comparison with France and South Africa, England don't look like they know what they are supposed to do! Let's hope hslf time gives them the time to sort themselves out!

Well mine did. The Mills contra piston moved when you flicked over the prop. Obviously, I turned over the prop slowly first to make sure there was clearance. It used to be a standard method of finding an approx correct contra piston position in the '60s when I used to run just dirsels with the Wenmac Hotshot the only glow I owned. All rather tidly these days but it was all I could afford from my paper round!

One way of finding an approximate position for the sub-piston, is to have the engine at TDC and then while working the crankshaft to and fro using an attached prop, screw down the compression screw until you feel the sub-piston as you jiggle the prop. Now back off one full turn, flick the prop over and the sub-piston should then pop back up to the approx correct position to run. Worked for me on a Mills 75 and PAW 249 and 149.

Thanks for posting. That was a great display of skill although why they thought it was OK to fire off anti-missile defences over a display area covered in pleasure boats is a mystery to me.

OK, realistic AUW seems to be just over 5 lb so aim for 1,000 watts output. This is now becoming 5S territory! I mention that as my Fantasista 70 comes in at 2.5 Kg or 5 1/2 lb. I use an Overlander Thumper 5055/06 580 kv in the Fantasista and get 1,200 watts out of it using a 5S and 16x10 prop. If you use a 4S and prop down to pull 1,000 watts you are looking at around 68 A. However, the 5055 is quite a bit heavier at 279 g and £14 more. That having been said, it's a brilliant motor and performs beautifully. The Fantasista will fly the FAI P schedule with this motor and the vertical performance is unlimited.

According to the 4Max website the motor has a maximum current draw of 36 A which using 3.8 x 4 x 36 gives 547.8 Watts. I belive the Gangster 63 lite has a target AUW of 4 lb. This motor on 4S would give 136 watts/lb. For an aerobatic aircraft this means it will not be able to maintain a constant speed when going vertical. That means relatively small loops and stall turns will become rushed with a limited vertical climb. 200 watts/lb is a better target figure which for a 4 lb model means 800 watts. I've used Overlander Thumpers in my F3A 70 size model. Looking at the listing on the attached link the T 5045/10 V3 is rated at 860 watts but needs an 80 amp ESC and on 3S a 14x8 prop. If that exceeds the available clearance you could use a 13x9 or 12x10. Up to you but a good power to weight ratio is essential for good unhurried aerobatics. You use half power for S&L flying and feed in the extra to maintain speed in the vertical.

Had the servo in question been involved in a crash Erf? I've always replaced the gear train of any crashed servos, where they are still available, before using it again. It's rarely the electronics that are damaged unless you really arrive at very high speed! If I can't get spare gear trains I'll scrap the servo.

Don't worry about servo speed for precision aerobatics. It's the heli boys who need it for their applications. They are going to react faster than you can and rapid movement is only needed for snap, or flick, rolls. Even then, the Savox speed would be fine. The key question for the Savox 351 is will it run on 6 v. JR used to be strictly 4.8 v only and 6 v, 5 cell NiMH, would fry them. If they are not rated for 6 v you will be limited to a 4 cell NiMH or turn down the supply from the BEC if you go that route. Torque, again, at 3.2 kg.cm is perfectly adequate for the Gangster. On my 2 m I've used mjni servos rated at 4.2 kg.cm and they were fine. So for the Gangster this shouldn't pose a problem. Futaba S148s were rated at 3 kg.cm IIRC and they would have been fitted, and probably still are, back in the day. I prefer a separate battery supply from the main flight pack and use a Powerbox Digiswitch to provide a controlled voltage. I use a 2S LiPo and set the switch for 7.4 v. I have also used the 6 v settkng whdn using JR servos as a fully charged 4 cell NiMH provides almost 7v when fresh off charge. I also use 2S LiFe packs for 4.8 v servos as the LiFe voltage drops quickly from the max 7.2 to 6.9 v pretty quickly and again have proved not to damage JR 4.8 v rated servos.