Keith Miles 2

Mission accomplished! Many thanks, guys. Yep, simple job as said to flip the small cog to the opposite side. Just had to slacken the leg pivot pin screws and two of the small adjacent cross head screws holding the brackets together to flex them apart for clearance then two tiny cap head screws to loosen the cog on the strut and rotate it. Job was a bit tricky, though, as there is virtually no slack in the air lines to allow the raising of the whole assembly enough for easy access. Likewise, getting the air lines off and back on again would be extremely difficult so I had to be very careful there in order not to create a bigger problem! Always good to learn something new and my friend, Tom, will be happy now as well. 😊

Bob and Chris, may I introduce to you the eagle eyed Thomas Barwick who started all this! 😀😀😀 Hello, Thomas! Seems there's no hiding place! I'm only doing this to keep you happy and make myself worthy of having beaten you to a bargain! Sorry, old chum! Tried to post something on our club Facebook page but Facebook was playing up. Got frustrated! So, nothing personal! 😊 Apologies also to Rob Mac who I only spoke to briefly on Sunday and didn't quite grasp his point at the time and before he disappeared. I was also being careful, on Sunday, not to embarrass or offend the previous owner!

Bob, thanks for the picture link. Those do look very much like my units. Using "Gear finder" didn't work so thanks for finding that for me. Thanks to both of you. I think I get what you are both saying and now see how it works. I think the legs themselves are merely clamped with a screw at the top, in fact, one leg seems to be slightly loose as I can turn it a few degrees either way. The other leg is tight. Also, without having yet removed either unit it does indeed look as though there are punched holes on both sides of each bracket. Due to other distractions, thought I'd give you an initial prompt response and I promise to get back to you in due course when I've had a chance to take a proper look and, hopefully, sort the problem out.

Bob, nope! Clicking icon says "No albums found". Tried copy and paste from "Pictures" folder. No go. So, next question, how do I post a picture? I have an I-Pad and a Windows10 PC. As for the retracts, I'm led to believe that they are good quality Robart units and they have the triangulated locking mechanism. Pending further input, I might just try to take one out to see if I can figure it out. I am reluctant, however, to disturb or disconnect any air lines unnecessarily for fear of creating further problems, hence my initial posting! As you suggest, it does indeed seem odd that such units would not be handed or adjustable. Web searching has got me nowhere thus far. In the current absence of a picture, I should have perhaps explained that these units are fitted to a 63" Corsair and move forwards/down and rearwards/up. Both wheels rotate 90 deg in the same direction coming down and, obviously, 90 deg in the opposite direction going up to finish fully flush in the wheel wells.Currently, this results, therefore, in both wheels sitting to the same side of their respective struts when down. That said, it seems that you did work that out! Whilst, in practice, it might not be a problem, it does look rather odd and detracts from the overall appearance of the model.

Bob, trying to post a picture. Here goes...!

Does anybody know if rotating air retracts are supposed to rotate in the same direction or opposite to each other. This is all new to me! I have recently bought a model second-hand which has yet to be flown. Retracts operate beautifully but when down, due to the common rotation the axles both point in the same direction thereby creating an albeit slight offset of wheel position. No big deal, just curious and wondering if there's a simple fix.

Promised a report back of first test flight so here it is. With the downthrust removed, much less tail lift on the bench. So that worked as I had expected. Was then happy to do a taxying trial armed with that! Yep, as others have said, it was fine, just the usual up elevator as a precaution. With almost ideal conditions today, decided to go for it! Usual slight touch of rudder during initial acceleration, no drama on take off and she climbed away perfectly at a sensible angle without any significant correction. Throttled back to medium speed, she flew straight and level with only a couple of clicks of down elevator. At that speed slow rolls and gentle loops were easily accomplished. Very nice flyer indeed! No nasty surprises. Approach and landing, again, no drama. Oh, and I greased it! So, (a) a really nice model and (b) I remain unconvinced that low wingers should ever require downthrust unless (a) the design is flawed or (b) the construction of it is flawed or (c) a pilot prefers all of his models to fly straight and level, at full power, without needing any trim correction! On the last point, any pilot of full size aeroplanes would confirm that speed is controlled with elevator whilst throttle/power, as it is meant to do, controls the rate of climb and descent. Thanks to all responders for the contributions.

Martin, many thanks for the confidence booster! I did wonder about the restraint but as I've said it's not something I've seen before and the effect was also greater than I would have expected. Probably won't get chance to test again until next weekend. Will report in due course! Hopefully, I will be able to report also how it flies without the down thrust. Oh, and how it handles when landing!

Posted by McG 6969 on 06/08/2016 15:25:10: ... Surely that's just a parachute? 😄 Otto Lilienthal's First Film from Johannes Hogebrink on Vimeo. ... imo, this could be named a "controlled flight", as well? ... 1893 > 1896. Chris

Posted by trebor on 06/08/2016 13:39:13: My Astro hog is a bit like that, just blipping the throttle pops the tail up. The c of g is set as it should be and its a slow build up on the throttle for take off otherwise it's a nose over. Once airborne it's all ok Funnily enough, my brother-in-law has one and, yes, with down thrust on a four stroke. We were discussing that comparison recently, as it happens! However, whilst it does, indeed, fly well, I have never taken it off or landed it myself and have never noticed it raising its tail on the bench! Similarly, my four stroke powered Wots Wot will tend to nose over without a little up elevator but, again, not on the bench, even at full power on a 13x6 prop! In due course, it was my intention with the PT19 to use your take-off technique anyway! Hoping to test again in the next few days. Will report the results, hopefully without any mention of a carrier bag!

Peter, yep, with you on this and with my PPL head on it smacks of an aerodynamic post design adjustment/bodge. My little indoor Aeronca Champ has a LOT of down thrust but then it is made of very light foam and has a high wing with no aerofoil, i.e. a thin sheet of foam simply bent into a curve to give under camber. I suspect that this is due to a wish to simplify manufacture and keep cost down. It is probably over-powered for the same reason, hence the bodge!That said, it's a lovely little thing to fly around indoors! Nice model you have there, by the way. Sadly, I lack both the funds and a suitable vehicle!

Hi, Jon Harper. Further to my reply to John Stones, CG range, as you probably know, is stated as 65 - 75mm from leading edge measured at the tip. My method, due to the limited length of my arms (!) is to extend the measurements inboard and tape piano wire to the wing in order that I can feel where the points are with my finger tips (apologies If I'm teaching grandma to suck eggs! ) I then view the model from the side by standing in front of a mirror! At 65mm the model sits perfectly level. At 75mm it sits about 15-20 deg nose down. My model, therefore, seems fine for balance in accordance with the spec. Also, these measurements place the CG range at about 7mm ahead of, and about 3mm behind, the rear edge of the main spar. This doesn't suggest that the given CG measurements are suspect and I remain unconvinced, at present, that the CG is the issue, or the only factor. Also, if I were to add sufficient weight to keep the tail down when under power, on the bench, I very much doubt that it would be flyable! 😊

Thanks for reply, John. Your point had been considered although nobody present at the time had apparently experienced such a marked tail response. Whether restraint of the wing leading edge under power was emphasising the nose down tendency also remains to be seen. I suspect (hope?) that having reduced the thrust angle that this will at least reduce the nosing down enough to give me more confidence about taxiing it for the first time, although probably still with the application of full up elevator! As I said, with no power, I can tilt the model forward without it displaying any abnormal (for me) desire to plop forward prematurely. I could, as you say, try raking the u/c forward but this would obviously alter the balance in addition to reducing the prop clearance! My brother-in-law also feels, like you, that the down thrust is not a significant factor although, despite over 40 years in the hobby he was also somewhat puzzled but nevertheless more confident than I currently am about a pending taxiing/flight test! If all goes well, I might also feel more confident about possible further testing minus the the thrust wedges! Having recently lost a Wot4 in a recent mid-air collision, I don't fancy smashing another model just yet, especially one as pretty as this! Will keep you posted.

Recently completed assembly of a Seagull PT19 ARTF. Took it to the field for, hopefully, a test flight. Sat it on one of our club's purpose made benches fitted with padded uprights to restrain models at the wing leading edge. Started up the recently run in OS52 four-stroke. Began to raise the power and the tail immediately came up. Significantly! Luckily, a helper was on hand to prevent the prop from chewing the bench. At full power, with full up elevator, the tail remained determined to fight the opposing force holding it down! Not good, I thought, and abandoned any idea of taxiing it for the time being, even on the club's beautifully mown strip! My current theory is that the model does not need the apparent built-in down thrust for the following reasons (a) a relatively high thrust line; (b) a low centre of drag; (c) a seemingly symmetrical wing aerofoil with, seemingly, zero positive incidence; (d) a tailplane parallel with said wing and (e) perfect balance in accordance with the specified fore and aft CG limits. At this point in time, I have added wedges to remove the downthrust, for obvious reasons! Second bench test pending! I would add that without the engine running the tail can be manually raised well above horizontal before the nose begins to drop forward tending to confirm that balance is okay and that it is not nose heavy. Interestingly, my brother-in-law is building a similar sized PT19 from a plan. The plan, apparently, recommends 3 deg of down thrust although the design is slightly different. Time will tell if he will experience the same problem. He, too, is fitting an OS 52 four-stroke. Any comments on this post would be most welcome!