Gary Manuel Posted June 21, 2018 Author Share Posted June 21, 2018 Posted by cymaz on 21/06/2018 18:17:06: Ah, the cunning plan comes to light! No, the cunning plan was in case I needed to fit the baffling from the front - AFTER the cowl was in place. I was going to glue some tabs with captive nuts onto the rear face of the outer rim of the cowl. Then I'd screw a circular disk, just the right size to fit the cowl opening onto the tabs. The disk would have had the required baffling glued onto the rear. Maybe I'll try this on another model some time. Quote Link to comment Share on other sites More sharing options...
Bruce Collinson Posted June 21, 2018 Share Posted June 21, 2018 Gary, Meant to ask; are you proceeding with the standard alloy wing tube? The reason I ask is that as well as the muddle re the c of g, I picked up from an American forum that the tube is prone to bending in enthusiastic flight. I spent too long trying to source a carbon replacement but apart from a Chinese source (call me old fashioned, but ...) I couldn’t find an exact fit and ended up with a loose fit inside the alloy tube. Then, I couldn’t get a consensus from my elders and betters as to whether the carbon needed to be packed out and if so, with what. I’d be interested to hear your opinion on that. My amateur structural engineering instinct was that as soon as the alloy deflected by say 2 or 3 mm, the carbon tube would accept the bending load and the alloy would recover. BTC Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted June 21, 2018 Author Share Posted June 21, 2018 Bruce. I'm using the standard wing tube. I know a few people in the UK who have owned one of these models and have never reported any problems with the wing tube. I've even had a go myself and not bent one. I'm no structural engineer, but I do know that close fitting tubes work by distributing the forces along their length. An ill fitting tube will only have three points of contact - one at each end and one in the centre. They need to be a tight fit along their entire length to work properly. Quote Link to comment Share on other sites More sharing options...
iqon Posted June 23, 2018 Share Posted June 23, 2018 Well done !!! Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted June 23, 2018 Share Posted June 23, 2018 I've got the other colour scheme one, with a CRRC 26 petrol, which is perfect for it. Am looking for this colour scheme, but not seen one. Inwood had the same one as mine, thought it was this scheme, but he can get one, so might call him to order on the next shipment, if one doesn't turn up at a forth coming show. Want to do it in a JCB scheme, where I now work and where I've seen one at a Ashborne scale meet a while back... Will use the new logo, similar to this: Edited By Paul Marsh on 23/06/2018 22:03:47 Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted June 23, 2018 Author Share Posted June 23, 2018 Hi Paul. Yes, I prefer the yellow and black scheme too. Available HERE for £174.90 including delivery! Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted June 23, 2018 Author Share Posted June 23, 2018 Maiden today went very well. Model flies well although the elevator is a bit twitchy. Inverted flight also curved to the wheel side and it wanted to drop into a harrier a bit on landing. All point to CoG a bit too far back. Will try moving batteries forwards a bit. Had a bit of an issue on the third flight. The canopy fell off in flight! I thought the canopy bolts may have worked loose. Turns out the ply tabs on the bottom of the canopy, that the bolts screw into had pulled out of the canopy - and no wonder. They were pretty much a butt joint with a short length of triangular balsa glued with PVA (or similar) onto the underside of the canopy. Took nearly an hour to find the canopy in the adjacent wheat field. A couple of puncture wounds in the wing covering where the canopy hit them, but no real damage and easily fixed (properly this time). Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted June 23, 2018 Author Share Posted June 23, 2018 P.S. What's the JCB pilot doing in the passenger seat? Quote Link to comment Share on other sites More sharing options...
Bruce Collinson Posted June 23, 2018 Share Posted June 23, 2018 Well done Gary. It is beginning to occur to me that, especially with ARTFs, anything which can fall off in flight will do so. I lost a canopy from an Extra (Great Planes) and the battery hatch from an Acrowot. You had a better day than me, I totalled a Wot 4 with signal loss. At least I can stop wrestling with it and it’s engine and crack on with the Yak, reinforcing its canopy tabs etc. Will you post the new C of G position in due course? Is the cowl ducting ok? BTC. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted June 24, 2018 Author Share Posted June 24, 2018 Sorry to hear about the Wot4 Bruce. I'm not planning on moving the CoG very far. I might not even bother. It was quite windy when I flew it, which may have affected how it flies. I'll try again when it's a bit calmer before I decide whether to move it. Aim for the forward end of the recommended CoG range and you'll not be far off. I'll never know whether the cowl ducting was necessary because I've never tried with out it. The engine runs nice and cool with the ducting in place, so it's staying. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted June 24, 2018 Share Posted June 24, 2018 Excellent news Gary....glad it went OK. Does it have a tendency to flick if you apply too much up elevator at all? I had a smaller Yak54 which was a lovely flyer but would bite & bite hard if you were a bit rough with the elevator.....note the use of the word "had" What's the power like with that engine? Does it do nice "Up" lines?...big loops? Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted June 24, 2018 Author Share Posted June 24, 2018 Steve. It didn't flick on me, but I noticed that if I overdid the loops, it would corkscrew as though one of the tailplane sides was stalling. Big loops and bunts were no problem with the power reserve I've got. I have a feeling that there is more to come once I find the right prop for it. In my shed now - just epoxied the canopy tabs back in. Removal of the old glue didn't take long!!! Quote Link to comment Share on other sites More sharing options...
Bruce Collinson Posted July 16, 2018 Share Posted July 16, 2018 Gary, Now I've finished repairing an Acrowot (u/c plate) and a Wot 4 (2 bulkheads, wing retention tabs etc) and have flyable go-tos again, I can turn back to the Yak which has been at a standstill. May I ask, where's the c of g at the root? I might as well try for a good starting position the first time I fix the batteries etc. Thanks in anticipation. BTC Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted July 16, 2018 Share Posted July 16, 2018 C of G is dead centre of the wing tube BTC And on most models constructed that way Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted July 16, 2018 Author Share Posted July 16, 2018 Posted by Bruce Collinson on 16/07/2018 11:07:00: Gary, Now I've finished repairing an Acrowot (u/c plate) and a Wot 4 (2 bulkheads, wing retention tabs etc) and have flyable go-tos again, I can turn back to the Yak which has been at a standstill. May I ask, where's the c of g at the root? I might as well try for a good starting position the first time I fix the batteries etc. Thanks in anticipation. BTC Hi Bruce. See the top post on page 3 of this thread. I am happy with the CoG at 15cm from the leading edge at the wing root (7cm at wing tip), which is the forward end of the recommended range. Posted by Denis Watkins on 16/07/2018 11:24:27: C of G is dead centre of the wing tube BTC And on most models constructed that way Not quite on this model Denis. My wing tube is 127mm from the wing root, which means that the recommended CoG positions are between 23mm and 33mm behind the wing tube. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted July 16, 2018 Author Share Posted July 16, 2018 I mentioned that my model was throwing the occasional tailplane stall at me. I've found the problem. The tailplane has warped since I built the model. I'm going to try and straighten it by the application of heat, possibly in conjunction with moisture / steam. If this fails, I may need to make a new tailplane but it will be tricky cutting the old one out. I also have another problem. I noticed quite a bit of oily gunge inside the cowl from the beginning, which I assumed was oil from the exhaust being sucked back into the cowl. Eventually it showed up inside the fuselage so I had a closer look. I had forgot to put a tube onto the crankcase oil breather tube and vent it outside the cowl. . Major clean-up operation before I will fly it again. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted July 16, 2018 Share Posted July 16, 2018 It owt to do with the braces ? Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted July 16, 2018 Author Share Posted July 16, 2018 Posted by john stones 1 on 16/07/2018 14:11:42: It owt to do with the braces ? No. The braces were slack (neither pulling nor pushing) when I assembled the model and after the warp was noticed. Edit - I did think whilst building and still think that it would be better with braces top and bottom, rather than just underneath, to allow both sides to be tightened till under slight tension. It would also allow the pushrods to be replaced by wires. Edited By Gary Manuel on 16/07/2018 14:20:57 Quote Link to comment Share on other sites More sharing options...
Bruce Collinson Posted July 18, 2018 Share Posted July 18, 2018 Hi Gary, Latest issue, i cant find any cowl fixing points/pinpricks to start setting out the cowl fitting process. Were yours marked? Am wondering if i have a variant, or a Friday afternoon product! Also,I haven’t fitted the tail braces (nor the tail, till the cowl is finished) yet. Would you do them differently? I made up two carbon tube struts, adjustable by clevises, for the Mentor on the basis that they would work equally well in tension and compression and would leave the underside a little cleaner; the tail hasn’t failed yet! BTC Quote Link to comment Share on other sites More sharing options...
john s Posted July 18, 2018 Share Posted July 18, 2018 Hi, I got my yellow/black version this morning and like Gary have done a fair amount of research online noting quite a few people having problems finding a good balance point, even those using the correct procedure as Gary described. I put the fuz on my bench and set it up square using the canopy seat as reference, at this the wing and t/plane incidences are 0 degrees so to me this seems OK, then I move to the eng b/head and find that it has upthrust of 1.5 -2 degrees and around 1 degree of right thrust. So upthrust and very little right side thrust, I'm definately no expert but this seems wrong to me, Upthrust!!! any suggestions ? Hope I've posted this in the right place. john Quote Link to comment Share on other sites More sharing options...
onetenor Posted July 19, 2018 Share Posted July 19, 2018 Gary Manuel Thicken the carbon tube with a wrap of carbon cloth ( OR glass cloth ) and epoxy resin.. Made initially a fraction oversize then sanded back ( better still lathe turned ) to fit tightly and epoxied in the alloy one. Or find another alloy one to fit ( epoxied) into the existing one Vhat does Alexander say? I would use a slightly flexible epoxy mix. Resin and finely chopped cotton fibre mix would be ideal..but getting any into the tube if the fit is really tight: which it should be, is the problem... Yer pays yer money etc. Edited By onetenor on 19/07/2018 04:46:59 Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted July 19, 2018 Author Share Posted July 19, 2018 Posted by Bruce Collinson on 18/07/2018 22:30:20: Hi Gary, Latest issue, i cant find any cowl fixing points/pinpricks to start setting out the cowl fitting process. Were yours marked? Am wondering if i have a variant, or a Friday afternoon product! Also,I haven’t fitted the tail braces (nor the tail, till the cowl is finished) yet. Would you do them differently? I made up two carbon tube struts, adjustable by clevises, for the Mentor on the basis that they would work equally well in tension and compression and would leave the underside a little cleaner; the tail hasn’t failed yet! BTC Bruce. I wouldn't worry too much about the missing pinprick holes. From what's been said in one of the earlier posts, it's not unknown for them to be in the wrong place anyway. My advice would be to look at the internal construction to find out where the strong bits are and then mark the position yourself. Regarding the tail braces, I don't think that there is anything wrong with the supplied ones or that they are anything to do with the warping. If I was building again though, I would probably make some changes here. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted July 19, 2018 Author Share Posted July 19, 2018 Posted by john s on 18/07/2018 22:53:56: Hi, I got my yellow/black version this morning and like Gary have done a fair amount of research online noting quite a few people having problems finding a good balance point, even those using the correct procedure as Gary described. I put the fuz on my bench and set it up square using the canopy seat as reference, at this the wing and t/plane incidences are 0 degrees so to me this seems OK, then I move to the eng b/head and find that it has upthrust of 1.5 -2 degrees and around 1 degree of right thrust. So upthrust and very little right side thrust, I'm definately no expert but this seems wrong to me, Upthrust!!! any suggestions ? Hope I've posted this in the right place. john I didn't measure mine John but I will do it once I get the cowl off later. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted July 19, 2018 Author Share Posted July 19, 2018 Posted by onetenor on 19/07/2018 04:24:58: Gary Manuel Thicken the carbon tube with a wrap of carbon cloth ( OR glass cloth ) and epoxy resin.. Made initially a fraction oversize then sanded back ( better still lathe turned ) to fit tightly and epoxied in the alloy one. Or find another alloy one to fit ( epoxied) into the existing one Vhat does Alexander say? I would use a slightly flexible epoxy mix. Resin and finely chopped cotton fibre mix would be ideal..but getting any into the tube if the fit is really tight: which it should be, is the problem... Yer pays yer money etc. Edited By onetenor on 19/07/2018 04:46:59 Presumably, this is answering Bruce's query towards the top of page 6 about fitting a second wing tube snuggly inside the original? I've gone with the standard wing tube. Quote Link to comment Share on other sites More sharing options...
john s Posted July 19, 2018 Share Posted July 19, 2018 Thanks Gary that will be interesting to know. Mine arrived with the pilot rattling around inside the canopy so I cut him and most off the flooring away just leaving a 15mm cross brace and the fwd inst panel, it's now 108g lighter and still strong enough. john Quote Link to comment Share on other sites More sharing options...
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