Martyn K Posted December 14, 2016 Author Share Posted December 14, 2016 Hi Peter 72" span. Its an easy scale up as the model is now in CAD. I think I would reduce the root chord thickness by about 1 or 2% though. Make it more manageable in blustery conditions. Martyn Quote Link to comment Share on other sites More sharing options...
Peter Burgess Posted December 15, 2016 Share Posted December 15, 2016 Hi Martyn, At 72" span I have a 26cc petrol looking for a home The only problem at these larger sizes is that wire under carriages are not so good. Peter Edited By Peter Burgess on 15/12/2016 11:14:26 Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 15, 2016 Author Share Posted December 15, 2016 Perfect. I'll start work on the drawings Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 15, 2016 Author Share Posted December 15, 2016 Sorry Peter - what weight is the engine - or alternatively, what is it? May need to tweak the front end to get it to fit.. Martyn Quote Link to comment Share on other sites More sharing options...
Peter Burgess Posted December 15, 2016 Share Posted December 15, 2016 The engine will be/is a MVVS 26 petrol or Evolution 26GX (basically the same thing) weight 940g Peter Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 15, 2016 Author Share Posted December 15, 2016 Cheers Peter Its slightly lighter than the OS120FS III. That surprised me Stock Number: OSMG0935 Displacement: 1.2 cu in (19.7 cc) Bore: 1.197 in (30.4 mm) Stroke: 1.083 in (27.5 mm) Practical rpm: 2,000-12,000 Output: 2.07 hp @ 12,000 rpm Weight w/o muffler: 32.5 oz (921 g) Weight w/muffler: 35.3 oz (1000 g) Recommended props: 14x9, 14x10, 14x11, 15x8, 15x9, 15x10, 16x6 Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted December 15, 2016 Share Posted December 15, 2016 bet it ain't lighter once you add a realistic silencer on! Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 15, 2016 Author Share Posted December 15, 2016 LOL I dont think that the Evo has a pumped Carb. I was planning on doing an inverted engine for this one as there is sufficient space to play with. Peter - can you give me some guidance on the tank position please and how big - I suspect that 10oz will keep it going for a while Thanks Martyn Quote Link to comment Share on other sites More sharing options...
Nigel R Posted December 15, 2016 Share Posted December 15, 2016 "Its slightly lighter than the OS120FS III." Which is quite a weighty beast for a 20cc four stroke, by current standards. Nice motor though. I weighed mine at 960g with the silencer. The replacement, 110alpha, is (if the internet is to be believed) quite a lot lighter, about 700g. Much the same weight as Saito 125 I think. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 15, 2016 Author Share Posted December 15, 2016 Agreed, its no lightweight. Just going to hazard a guess as to where the prop disc will be... It fits very well on the straight scale up.. Martyn Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 23, 2016 Author Share Posted December 23, 2016 Progress has been steady. Its been mainly a case of adding and finishing off the detail bits but I managed to get the KF4-40 completed No dramas It weighs this much with 3000mAh 4S in Kg - which is just on the 4lb target. It looks like this.. and this and underneath its a lot like this.. I'll take a few more detail shots in the next few days. Radio has been installed and EPA/Rates/Expo set. I'll probably change the wire for the u/c legs - one of the piano wire legs feels very cheesy They are both ready for a maiden - perhaps next week if the weather dries up a bit and the wind drops I promise that I'll never try and repeat this challenge again, looking back, I started this on the 12/10 - and effectively completed the model today - 2 models in 10 weeks (I have also been building a 2m glider as well at the same time but that has another weeks work to go on it). So whats next? Digital Crayons at the ready. Best wishes for Christmas and the New Year Martyn Quote Link to comment Share on other sites More sharing options...
Paul C. Posted December 23, 2016 Share Posted December 23, 2016 Looks great I am sure it is going to fly as good as it looks 👍 what motor did you use any issues getting the cog in the right place? This has to be next on my list once I have completed the flea. Did you mould your own canopy or is it a purchased one? Paul. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted December 23, 2016 Share Posted December 23, 2016 Looks excellent Martyn, love the colour scheme John Quote Link to comment Share on other sites More sharing options...
Ian Jones Posted December 24, 2016 Share Posted December 24, 2016 I don't know how you do it Martyn, takes me ages just to do one model, let alone multiple models simultaneously. Hope she flies as good as she looks. Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 24, 2016 Author Share Posted December 24, 2016 Thanks all A bit of a panic on the KF4. With the rear mounted R/E servos - midi digital metal gear and the LiPo as far forward as it will go the CG was just in front of the main wheels - which is just where I wanted it. We tend to get a bit too hung up on CG position. I was more concerned with carrying dead weight rather than a lively elevator. That can be trimmed out with mechanics providing the design is sound and it's stupidly too far forward or back. My scaled down Curare has the CG behind the main wheels when it's dry of fuel. It flies far better than it's power v wing loading. I think they will both be ok. The CG is in the same relative place on both - slightly further forward on the KF3 as it will be carrying fuel. Ian - the trick to fast throughput is to have at least 2 models on the go so you are never waiting for glue to dry. It also gives you time to plan the next steps. Best wishes Martyn Edited By Martyn K on 24/12/2016 01:10:29 Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 24, 2016 Author Share Posted December 24, 2016 Posted by Paul C. on 23/12/2016 22:04:56: Looks great I am sure it is going to fly as good as it looks 👍 what motor did you use any issues getting the cog in the right place? This has to be next on my list once I have completed the flea. Did you mould your own canopy or is it a purchased one? Paul. Hi Paul CG I have mentioned. If you think that is too far back for you then there is plenty of space in the fuselage for the R/E servos. The motor is a a Turnigy D3548/6 790KV driving a 12x6 and a 40A ESC. Its a similar setup that I used on my Kanga Fun Flier and that is far more draggy than this - about the same AUW though. The canopy came from Vortex Vacforms - the part number is on the plan, Its not quite as raked back at the front as I would have liked but its a fair representation. They also do a straight flat windscreen version about the same size for those who may prefer a P51D look I'll update the plans over Christmas and make them available for download. Best wishes Martyn Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted December 27, 2016 Share Posted December 27, 2016 Good micro servos might be enough with short links to the (not very big) tail surfaces. I have used Hitec mighty feathers in a 46 size acro trainer with good results. 10 grams in the tail makes a difference. Happy landings in 2017! Lucas Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted December 27, 2016 Share Posted December 27, 2016 By the way Martyn, she looks good. I have just started on the Skywriter but am tempted..... Lucas Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 27, 2016 Author Share Posted December 27, 2016 Both maidened today. No drama and no disasters. Take off run for the IV was about 5m. The III needed about 10m but it was perfectly powered in the air. Enough for decent sized. square loops and long verticals before a stall turn. Both knife edge far better than they should do. Both are slightly over elevated - probably the CG too far back on both but the dive test is about right for me for both. The IV is under propped with a 12x6 just a bit too tame. I'll try again with an 11x9 or 11x10. The III is perfect with a 10x8 although it was trimming the grass strip slightly. On a slightly down side, The IV isn't very well laterally balanced but that is easy to fix and both need the travel reducing further for A and E. But both are in one piece and I am feeling pretty chuffed at the moment. Quote Link to comment Share on other sites More sharing options...
Ian Jones Posted December 27, 2016 Share Posted December 27, 2016 Congrats and well done. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted December 27, 2016 Share Posted December 27, 2016 Quite an achievement in just a few weeks, Martyn. Really well done. Cheers Chris Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted December 27, 2016 Share Posted December 27, 2016 Very good Martyn, pleased all went well for you, though never doubted it John Quote Link to comment Share on other sites More sharing options...
Lucas Hofman Posted December 27, 2016 Share Posted December 27, 2016 Congrats Martyn, It is always a great feeling when many hours building lead to a successful first flight! Lucas Quote Link to comment Share on other sites More sharing options...
Martyn K Posted December 28, 2016 Author Share Posted December 28, 2016 Thanks all I was pretty comfortable with these two. They are quite a simple re-scale of a proven original. Any disasters would have been of my creation. I ordered a couple of new props last night - an 11x8.5 and an 11x10 for the IV. Hopefully they will make it a bit more lively. Its not massively out but it will get better. As its is at the moment it would make an excellent Aileron and Aerobatic Trainer. Ideally, the elevator and aileron horns need to be bigger than the ones that I made - I'll revise the plans accordingly and may get them out later this week. I cant change my aileron horns as they are built in so I'll have to play with the servo horns. I realy wish that servo manufacturers would provide a reduced travel = higher torque servos - 45deg each way would be more than enough for most of my models That's basically it though. Any changes, I'll update here Martyn Quote Link to comment Share on other sites More sharing options...
minty morton Posted December 29, 2016 Share Posted December 29, 2016 Very very well done Martyn. Looking forward to seeing them next year. Minty. Quote Link to comment Share on other sites More sharing options...
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