Bob Cotsford Posted August 8, 2015 Share Posted August 8, 2015 Posted by Colin Leighfield on 07/08/2015 23:21:14: The co-axial motors are magic. People don't realise that it's a twin! Well, no Colin. I don't suppose many would expect to see a cruciform tail pusher twin engine plane using contra-props. i doubt many would believe it was a scale model either. That's class. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 8, 2015 Author Share Posted August 8, 2015 Cliff, thank you. It's nothing like as adventurous as your Constellation though, that is really ambitious. My Supermarine 317 project is similarly complicated and is on the back burner while I get some more practice in on this and other projects. Bob, you are very kind and from a chap with your experience and expertise, your words are greatly appreciated. There is scope to improve this now, so I will. The dimensions are exact scale and proving to be ideal for a stable and very flyable aeroplane. Perfect for a first venture with a contra-prop set-up. Quote Link to comment Share on other sites More sharing options...
Cliff Bastow Posted August 8, 2015 Share Posted August 8, 2015 Colin, The Connie is a bit of a challenge in some areas but hopefully it will be ok. I have realised that my models are never going to be the best finished or detailed but as long as they look like the real thing in the air and fly ok then thats good enough for me. I dont know how you keep so many projects going at the same time, I get distracted far to easily sometimes. Keep it up and Cant wait for your next project. Quote Link to comment Share on other sites More sharing options...
ROY DAVIES 1 Posted August 9, 2015 Share Posted August 9, 2015 Colin, This model is a great achievement. I have been watching the build to fly log from the side via my 'phone, computer time seems to be a bit short these days. Like everyone on here I await a video of this impressive model. It has a great sit in the air to be sure looking like it is meant to be there. I was curious to it's origins in the development phase mainly looking at the North American *"Welsh Hat" (* The Ian Allen spotters guide 1950s) rudder/ fin assembly, so I had a look at the A26 Invader. I was amazed to find that there were similarities between the two aircraft. The Mixmaster's span was 21 metres or so the invader 21. The lengths were 'Mix 16 metres the A26 15, the weights were Mix, 9.475 lbs. the A 26, 10365 lbs. Looking at the 3 view the wing plan, form except for the swept L/E's on the Mixmaster it looks very similar so does the tail unit. The fuse' of the Mixmaster is a really large low stressed unit and the lighter weight allied to the large power unit would give it the performance it had. Very quick and clever and a well tried way of achieving a project goal Quote Link to comment Share on other sites More sharing options...
ROY DAVIES 1 Posted August 9, 2015 Share Posted August 9, 2015 Colin, I have to tell you your next project awaits in the form of the Bugatti "Reve Bleu" - Blue dream. I have just viewed the test run prior to flight on 'P Prune' Rumour and news. It is due to fly VERY soon and looks magnificent. I wouldn't like to be the pilot he has a drive shaft under each arm. I don't know if that's better than an Aircobra/Kingcobra's drive shaft between the legs though. Regards, Roy (Wales) Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 9, 2015 Author Share Posted August 9, 2015 Hi Roy. Thank you. The design must have been very efficient because despite the size, as you point out, being similar to the Invader, it had a similar performance on much less power, the two Allisons together giving a total,of about 2750hp. To have a bomb-load of 8,000lbs with a long range was remarkable really. I hadn't thought about getting a flight video, I will see if it can be done. I mentioned the Bugatti P100 on the first page of this thread with a photo, 04 May? I can't wait to see it fly. I share your reservations about the drive shafts, but,I'm sure that they will be ok! They reckon that although the P39/P63 shaft spinning and flexing between your legs was a bit disconcerting, you got used to it! Quote Link to comment Share on other sites More sharing options...
ROY DAVIES 1 Posted August 9, 2015 Share Posted August 9, 2015 It must have been a bit disconcerting trying to pilot one with an oscillating sphincter - going at shaft speed as well. Quote Link to comment Share on other sites More sharing options...
ROY DAVIES 1 Posted August 9, 2015 Share Posted August 9, 2015 Yesterday I saw my friend test fly his, Canadair CL-84 Dynavert by Shenzhen Unique Model. It flew well and quite fast into wind with good control authority as well. Early models had a nasty pitch over before transitioning into a vertical landing but it must have been sorted on his. Flying it is a real cart load of monkeys as in the vertical phase it is a heli' but changes to fixed wing in forward transitioned flight, and the transmitter works like that too. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 9, 2015 Author Share Posted August 9, 2015 Maybe that's why the P39 got a reputation for "tumbling" in some circumstances, it was probably the pilot squirming on his seat, I'm sure I would be if it was as excruciating as you suggest! That Dynavert definitely sounds beyond my modest flying capabilities Roy! I don't think that I'll be experimenting to that degree just yet. I'll watch someone else make a mess of it instead! Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted August 10, 2015 Share Posted August 10, 2015 Nice one Colin, sorry been out of range and missed that this had flown Cheers Danny Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 10, 2015 Author Share Posted August 10, 2015 Thanks Danny. It was something I had to do! It's been very satisfying as well, I was starting to doubt my judgement so this has been a confidence booster for me. A bigger one would be spectacular, but not yet! Back to the Chipmunk now. When I saw you at Old Warden, the reason that the engine bearers seemed to have come undone was because I had trapped them in the tailgate of the car! An easy fix fortunately. I will start writing up on the thread shortly. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 12, 2015 Author Share Posted August 12, 2015 I'm adding a bit of cosmetic detail now. Exhausts next, then I will do a bit of lining. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted August 13, 2015 Share Posted August 13, 2015 It has the look of a decent slope soarer Colin John Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 13, 2015 Author Share Posted August 13, 2015 That thought crossed my mind too John. It would have been nice to join Mark Kettle and the PSSA boys at Long Orme over the weekend and take this along, I keep saying I'll do it one of the days. Probably the best route would be to take it up to 1/12 , around 70". As we've said before, too many things to do. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 14, 2015 Author Share Posted August 14, 2015 I've stuck the exhausts on. A touch crude, but they add a bit of realism. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 21, 2015 Author Share Posted August 21, 2015 I've tidied it up a little more. Also realised that I'd fitted the ventral fin too far forward. Not sure how I did that because I'd got it right on the plan. I've re-worked the back end and got it in the right position. This is as good as it's going to be now! Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 22, 2015 Author Share Posted August 22, 2015 I don't know if this thread has raised anyone's interest in contra-props. Yesterday I bought the September issue of RCMW and in there David Chinery has written a feature on the subject, in connection with his Bristol Brabazon. He features the 1550 Kv motor combination supplied by HK and as used by me in the Mixmaster. He shows it as currently supplied, with 2 8x4 props. I have bought one of these as well, although the one in the XB42 has the original pair of GWS 3 blade 7x3 1/2, which perform perfectly well and I have no intention of changing because they look brilliant! I though it was about time that I did a check on performance. With a freshly charged 3S2200 Lipo it shows 18A and 220W. The all-up weight since the repairs after the first flight incident and adding some detail and more paint is 890 gms, 31 ozs, so it has more than 100W per lb. and the spritely performance shows it. The wing loading is now 14ozs./sq.ft. rather than the 13 I originally reported. Although you might expect to lose some efficiency by comparison with a single 2 blade prop, it doesn't seem to be any big deal and I don't see it as a concern at all. A great opportunity to do a Fairey Gannet, Westland Wyvern, Seafire 47, Martin Baker MB5 etc. The only problem there is sorting out the spinners, I admit that the Mixmaster isn't scale in that respect! I hope that this has been of interest to a few colleagues. Unless the weather is favourable tomorrow, I won't be able to fly this again before the electric day at Fradley on 08 September because of being 9 days away in the Isle of Man for the Manx GP and Classic TT. Time to focus on the other ongoing projects now. Quote Link to comment Share on other sites More sharing options...
Erfolg Posted August 22, 2015 Share Posted August 22, 2015 As a comparison, one of the Vulcans in our club, a 69" span, originally used 2 by 3 blade props. The model struggled to leave the ground and was pulling a lot of watts. These were changed to 2 by 2 blade props, everything else the same. It now pulls less watts, and is now very convincing. The mammoth difference in performance is breath taking. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted August 22, 2015 Author Share Posted August 22, 2015 Erfolg, I pretty much expected that. However, there is no lack of go here, there is almost enough thrust to take it vertical from the hand. So although the two bladers may well give more thrust, the plane doesn't need it, I'm flying at half-throttle most of the time anyway. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 5, 2016 Author Share Posted September 5, 2016 As part of rehabilitating myself after a frustrating few months in which everything has been on hold, I've done a quick repair and renovation job on the Mixmaster after throwing it onto the runway and bashing the front in a few months ago. It's such a great flyer that I want it back in the sky. With the Depron structure it is easy to fix and here it is in progress. It is at the detail finishing stage now, I will finish it some time tomorrow. The silver finish frankly looked awful close up, so I have tried to smooth it out a bit and repainted with light grey, which actually masks much of the poor surface and I think looks a bit better. Looking at the photos of the original it does appear that it originally flew in the natural metal finish I tried to imitate originally, but was painted in a light grey later. I used some Tamiya Haze Grey that I happened to have and I think it looks good, although a bit darker than I assumed it would be from the cap on the aerosol can! It will do though and when I have painted in a bit more detail in the canopy and nose glazing, plus the exhausts and also some red trim around the nose that the prototype featured, I think it will look a lot better than before. I'm still in love with the contra-prop set-up and I've got three more contra-rotating motor units ready for future projects. Very exciting stuff. (For a simpleton like me anyway)! Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted September 6, 2016 Share Posted September 6, 2016 very nice model Colin. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 6, 2016 Author Share Posted September 6, 2016 Thanks Tony, your kind of model I think. You ought to have a look at these contra-prop set-ups. They're not that expensive for what they are, particularly bearing in mind that you are getting two motors and they come with props as well. The slightly bigger 375W version from HK looks really useful, with Depron it would fly a decent size model. I've got one. There are some really interesting planes that used these and it makes them a lot more interesting. Also, the lack of torque reaction means that they fly like a jet. Sound good as well. Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted September 6, 2016 Share Posted September 6, 2016 there are a few models that i would like to build with contra rotating props, but i worry about the power output as these would be fairly large models. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 6, 2016 Author Share Posted September 6, 2016 No problem at all mate. You might lose a bit of efficiency at the prop but it's not much and modern brushless motors have power to spare. Particularly with a light Depron build there's no problem and there are real advantages. You don't need any side-thrust for a start and there's no lateral change of trim as you power up or down. The 375W HK set-up would fly a reasonable scale model up to 5lbs, if you weren't going for a non-scale aerobatic performance. If you look at Himax you can go a lot bigger, but then you are getting expensive. You could build a pretty big Short Sturgeon with two of the HK 375W co-axial motors though. A Depron model weighing 7/10 lbs. is getting pretty big. Quote Link to comment Share on other sites More sharing options...
Tony Bennett Posted September 6, 2016 Share Posted September 6, 2016 i was thinking of the saro princess. that would have 6 contra rotating motors and 2 normal ones, but would have to have an 80" wingspan to fit it all in the space. hmmmmmmmmmmmmmmm Quote Link to comment Share on other sites More sharing options...
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