TIM Shaw
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Everything posted by TIM Shaw
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Hi Nigel Are you saying that if you open the throttle wide and turn the engine over by hand (glow disconnected) it won't "suck" fuel up, but if you block the exhaust and turn it over you do get fuel into the engine? Sorry to be pedantic, but "fuel flowing" could mean anything.... If so, then it sounds like you have an air leak around your carburretor somewhere, check it is properly seated and tightened up, and check all the other screws in the area too, its not unknown for them to come loose with vibration. Is your engine reasonably well set-up at both tick over and full throttle? Do you filter your fuel? that one will cause arguments I'm sure but I always run a filter in my feed line. If you do, has that worked loose? and if you don't, well, I would fit one.... (ducking down behind the parapet for a few minutes now....) And when you say all your pipes are checked, you mean properly secured and leak and split free - particularly if you have a rear mounted remote needle.. Assuming all is as it should be, I would remove the main needle and flush through the spraybar with fresh fuel, using your fuel pump, just to make sure there are no foreign objects in there, then refit the needle, maybe 2 turns open? and try it again. Oh being careful not to cause a hydraulic lock in the process - do the flushing so the fuel drops out of the engine, and turn it over slowly by hand with the silencer facing downwards before thinking about putting a starter on it. HTH Tim
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This does look really good Martyn - I have to admit it is not my thing, way too impatient, but I can at least appreciate craftsmanship at work
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As Martyn said - does it fly ok at normal speed? Is your horn secure and not floating in the foam? I don't know the model, but is the servo pulling the elevator up from a top mounted horn, or pushing it up using a horn mounted on the underside. If the latter, a bendy pushrod may be to blame, again allowing blow back at high speed. Typically, a nose heavy plane will be sluggish on elevator - but failure to pull out of a dive could actually indicate a rearward CG - there is a well-known trimming check for CG, known as the "dive test" Trim for straight and level flight at mid throttle,take it up high, then push the nose down to about 45 degrees and watch what happens. If the CG is correct, the model should slowly recover to straight and level. If it's too far forward, it will snap out of the dive rapidly, while if it too far back the nose will tuck under and the dive will steepen. I know this sounds counter - intuitive, but trust me, it's correct, and is to do with where you have your elevator trimmed for straight and level flight.
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Can my glider be towed using it's hi-start hook?
TIM Shaw replied to Chuck Plains's topic in Flat Field Gliding
I don't think its quite that clear cut, TBH. What control surfaces do you have? If you have ailerons it is possible to aerotow using a hook, but it is certainly a good idea to ensure both the tug and the glider can release the tow if necessary. Without ailerons you simply will not be able to aerotow using the hook, unless the idea is to use masses of power and go up vertically, irrespective of what the glider is doing..... An alternative might be piggy back cradle? -
Ursa Major is very nice Nigel - not unlike the Aurora 45S I have on the board at the moment, but that looks like a much more complete plan. Gangster - certainly if Jon is willing to go down the transplant route it would make perfect sense to drill for both mounts now, and probably stand off the 35 from the firewall a little so the spinner backplate on both engines ends up in the same place, and the lighter, 35 will be mounted slightly more forward. Bit of thought on the throttle linkage to make that adequately adjustable would be a good idea too. I like to think I do understand 2 stroke engines, never got on with 4 strokes, and all I know about elektrikery is that all things electric work on trapped magic smoke, and if you let it escape, they don't work anymore..... A member of our club flies the 63 lite on electric very nicely, but I couldn't even begin to equate the power of his set up to an IC one. Wish this wind would drop a bit - really want to nip up to the field and set up the un-run engine in my new Aerostar 69.....
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Looks very nice to me too Nigel. I've broken threaded rods when I bent them at the end of the threaded bit before now, and I no longer use plastic clevises on any control surfaces after the one I had on the elevator of my second R/C model (KK Student - remember them?) let go at hte bottom of what was supposed to be a square loop..... Guess that's just me though.
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All good advice here, I'm sure the 35 would give you a gentle flying Gangster - but I'm not sure that's really what you're after. And its much more of a pain to fit a bigger mount later, particularly with a built up cowl So my advice would be go for a 46 or 55 for this plane, OS if you can run to it, but don't rule out a modern SC or ASP either. Then take a look at Martin Kinders KwickFly 40 drawings, and build either the Mk3 or Mk4 for your 35, changing it a bit if you want, been meaning to do a sort of retrospective build log on my Mk4 because, as a tight wad Yorkshire heretic I've taken a few liberties along the way and still ended up with a sweet flying plane. I actually have 2 of the 35s, looking at an old USA design called Excalibur 2, and the Prettner Mystic drawings, to find a home for the other..... If the debate has got you into scratch building and even designing your own, so much the better!
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Thanks for that David! I do entirely agree about side winder engine mounting though, better for goo avoidance, better for aligning fuel tank and carb center lines, and (almost) impossible to hydraulic lock even with the brutal use of electric starters. Upright would be a poor second choice, and I hate inverted engines with a passion - bit of a shame really, with a pair of Hanno Specials looking for homes and a Challenger and Touche in the build queue..... Come to think of it, that might be why they're still in the queue.
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The OS 35 AX is a super little engine - I have one in a Kik Fli 4 / 40, built - loosely- to Martin Kinders drawings. This is around 53" span and just under 4lbs, and it flies very nicely. But I consider it is at the lower end of the power requirement for this model, I can fly patterns with it, but Ii do not have unlimited vertical, for example, and while it will probably fly the Gangster 63 lite alright I seriously doubt you will get Pattern style performance from it. Just to expand on that, in conjunction with the question you ask about throttle. It is an unfortunate fact that most R/C pilots do not use their throttles as a fully proportional channel, which, of course, it is. To fly really nice figures you need to be modulating the throttle all the time, and only use full throttle really for take-off and vertical climbs, and getting out of trouble. If you limit yourself to having to fly with the throttle wide open all the time you will lose out on the flexibility a more appropriately sized engine would give you. I am sure - provided the carb is properly set up, engines are best run at less than flat out for most of the time. sadly though, many people seem to be happy with max revs all flight. JMTC TIM
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Parkflier plastics may have something - thought I had a link but it doesn't seem to be working....
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I guess I just learned something too.....
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Posted by Nigel R on 25/04/2017 09:45:08: Another way of looking at it for aerobats - 1lb per 0.1 cu in gets you "good" vertical performance. Excellent Rule of thumb! I find the modern 36s quite capable of powering 53", 4ib pattern type models, while once you get up to 6lbs you need a 61, and a pipe much beyond that.. Drag, due the model size is also significant I guess, so even on a very light Gangster 63 I wouldn't consider anything less than a good 46. I had on original with an ASP 61 in it that was great, also had a 52 with an OS 40 FP which flew nicely - interestingly though I felt it was less nice with Schneurle ported 45 - maybe the additional weight didn't help. And then there was the 42, interesting to fly while the OS21 FSR kept running, had a glide like a brick when it stopped....
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Sorry TP I Really don't think so. A Plane in flight is a compromise between all sorts of different forces acting on it, and the relative positions of where those forces act. So a model will balance on its centre of gravity, yes, but it is the relationship between where that is to the aerodyanamic centre of pressure that governs stability in flight. So while the static measurement of CG is important to determine a "safe" starting point, the model can only really be dialled in while being flown, or rather, between flights, and the way the wing sits relative to the horizontal while on the balancer is not really relevant. I know it's actually even more complicated than that, but I don't think it's worth going into that just that now.....
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Andrew You said you did your tests with the model tethered on the ground? It is my understanding that they should be conducted with the model 1m off the ground to avoid excessive ground reflection, so while your tests provide useful comparisons, an "official" test should come in with a slightly lower result. But I agree with John - Always found APC props to be the least noisy, provided they are properly balanced.
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Posted by Jonathan M on 12/04/2017 08:35:07: I always understood 'stab' to be an abbreviation of 'stabiliser', its usage originating in America. +1 to what he said.... Also, is this model at all related the old Uno Wot that CF used to sell as a trainer? I used to do a lot of instructing and that was my favourite trainer, and yes, it essentially had a glider wing and flew well on a decent 32 or cooking 40 - if its the same model an Irvine 53 is way over the top.
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I don't know the model either, but how is the wing held on? I do know that the UnoWot - which was an earlier version of a trainer from Chris Foss - (and a very good one, IMHO), had the wing held on with rubber bands. More than once I saw beginners turn up with just 2 crossed bands to hold the wings on, and they exhibited a similarly bad behaviour... If it is a banded on wing, make sue you have 2 crossed, then 2 parallel, then another 2 crossed. Otherwise I would think the Irvine 53 is a tad too big for the model - I have one in a DSM Contact 140, which is a serious, old school pattern plane, around 56" span, and that goes unlimited vertical on an 11x9 prop - not what you want on a trainer!
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