Ron Gray Posted June 19, 2020 Share Posted June 19, 2020 Having just finished the Lavochkin LA-7 my next project is the CF Xtra Wot so is anyone interested in seeing the build progress? I’m happy to record the progress with photos and videos but equally no problem if Forumulites think it is a bit of a boring subject! Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted June 19, 2020 Share Posted June 19, 2020 Is this the ARTB version, then I'll follow with interest. Quote Link to comment Share on other sites More sharing options...
Gary Spicer 1 Posted June 19, 2020 Share Posted June 19, 2020 Hi Ron, I will follow it, I was thinking of building one myself, another Laser for power? Gary Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 19, 2020 Share Posted June 19, 2020 Be interesting to see how similar or otherwise it is to the ARTB AcroWot. Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted June 19, 2020 Share Posted June 19, 2020 I have 2 Xtra Wots, good model. First one has a OS 120 FS Pump (originally has a Saito 180) and the other a OS 120 AX two stroke. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 19, 2020 Author Share Posted June 19, 2020 It is the kit version, not the Ripmax Acro Wot XL and it will be leccy powered! (shock, horror, not a Laser 155). I was going to go down the Laser route but I was 'challenged' by a colleague to 'lectrify it so it will be 10s. For the colour scheme I want to mimic the Hamilton orange and black so already have HK and Solarfilm covering film in stock for that. I also ordered it with the longer can of peas. Edited By Ron Gray on 19/06/2020 10:00:40 Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted June 19, 2020 Share Posted June 19, 2020 The first one was one of the first that Chris Foss had off the production line. It was sold at a special price - abit like a prototype and test report, think I only paid £160 for it. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 19, 2020 Author Share Posted June 19, 2020 I first saw one, in the flesh, a couple of years ago and it was powered by a Laser. It flew really well and I was impressed although, at the time, didn’t like the tail skid in place of a wheel mainly because it made such a noise on our tarmac! So when lockdown arrived I decided to go ahead and get one and I even have plans for that tailskid. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 19, 2020 Author Share Posted June 19, 2020 The box of bits, excellent quality of balsa and ply, good CNC cutting and pretty good destructions too. Edited By Ron Gray on 19/06/2020 10:55:46 Quote Link to comment Share on other sites More sharing options...
Paul Marsh Posted June 19, 2020 Share Posted June 19, 2020 How much are they now? Can't find a price anywhere... Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 19, 2020 Author Share Posted June 19, 2020 I paid £270 with postage and the larger canopy. Quote Link to comment Share on other sites More sharing options...
Gary Spicer 1 Posted June 19, 2020 Share Posted June 19, 2020 You did well to get it for that Ron. Leeds Model Shop have them for £299.99 and direct from Chris they are the same price, Leeds have them in stock just landed today! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 19, 2020 Author Share Posted June 19, 2020 I did think it was a competitive price from Chris, maybe he took sympathy with a lockdown build project! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 19, 2020 Author Share Posted June 19, 2020 And we're off! Following the excellent instructions and sketches the fuse was first up on the agenda and joining the balsa outer pieces using masking tape over the joints, folded back, glued then pinned onto the workbench tape side down. I'm using Gorilla Glue White for most of this build as I find that it sets quite quickly is strong and dries clear, oh and it sands very well too. Excellent quality cutting of the parts means very little sanding required to get a good fit. Once the glue had set then it was fitting the ply doublers (yes making doubly sure that I had a left and right part!). Balsa stiffeners and longhorns added together with the tail post. Quickly progressed to the formers which have to be removed from their parent sheets but you can see the quality of the CNC routed parts And this is the tool that I use on ply parts to cut them from their parent sheet Engine bulkhead and first former fitted making sure that everything is lined up correctly, lots of clamping and good use of 6s batteries! Opposite fuse side fitted with other formers temporarily fitted in position (the fuse has to be drawn in at the tail for these other formers to fit. And to support the tail whilst the glue was drying an offcut from one of the parent sheets I keep meaning to make myself a jig but progressed without one using set squares and front to back aligning to make sure everything was square. To be fair having made sure that the front end was square when I fitted the first 2 formers, very little adjustment was necessary to make sure the fuse wasn't twisted when it came round to pulling in the tail end but a jig would have made it easier (make one!!!!). And then it was a matter of fitting the remaining 2 formers and the servo tray. And that was the first day and a bit of work, coming along quite nicely. Quote Link to comment Share on other sites More sharing options...
Brian Cooper Posted June 19, 2020 Share Posted June 19, 2020 The Xtra Wot is a great performer but make sure the tailplane is "solid". The tails have been known to fail during a bit of "spirited" flying. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 20, 2020 Author Share Posted June 20, 2020 God point Brian, Chris Foss does say, in the instructions, that if a larger engine is to be used or if the proposed flying is to be somewhat spirited then the tail should be reinforced with carbon. The tailplane was redesigned so that the elevator counter balances were removed and those pieces stuck to the horizontal stab (sorry about the use of an Americanism) as I believe that was another weak point. Mine will be reinforced! Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted June 20, 2020 Share Posted June 20, 2020 If I remember correctly it wasn't just the tail plane that failed but also the fuselage just in front of the tail plane could break. I built one for a club mate some years ago with a YS 140 for power. Great plane and no vices to speak of. The rear the was strengthened with some thin doublers. The model is still around with a Moki 180 Glow in it now . Great model enjoy . Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 20, 2020 Author Share Posted June 20, 2020 I just thought I'd weigh the powertrain I propose for this model and, with batteries (10s) it comes out at 2Kg. Now a Laser 155 weighs in at, say 1Kg and a full tank (500cc) weighs about 120g, that's a lot of difference! Am I missing something here? Quote Link to comment Share on other sites More sharing options...
Keith Berriman Posted June 20, 2020 Share Posted June 20, 2020 Maybe worth a quick call to Chris' Foss Monday morning to check on electric set up ?? for that model before going much further Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 20, 2020 Author Share Posted June 20, 2020 There's a chap on RC Groups with an almost identical setup to mine but he's running it on 12s and he changed his from IC to leccy so I've asked him what it's like. Quote Link to comment Share on other sites More sharing options...
Braddock, VC Posted June 20, 2020 Share Posted June 20, 2020 Posted by Ron Gray on 20/06/2020 14:54:20: I just thought I'd weigh the powertrain I propose for this model and, with batteries (10s) it comes out at 2Kg. Now a Laser 155 weighs in at, say 1Kg and a full tank (500cc) weighs about 120g, that's a lot of difference! Am I missing something here? 500 cc of fuel weighs more than that, probably nearer 400 - 450 grammes. You also get free noise with a laser. I had a turnigy 26cc gas engine in one of mine and an OS 120 surpass mk2 in the other. The engine doctor is spot on regards the inherent weakness abaft the trailing edge of the wings, exacerbated if one fits the servos back there. Lovely well mannered plane even crashes gracefully. Rudder is a pain if you flip them over on landing though. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted June 20, 2020 Share Posted June 20, 2020 120gm for fuel? Are you sure Ron, that's only 4oz, I'd have thought you would be looking closer to 16oz, if it were water it would be 500gms or 17ish oz. Add on a servo and linkage, maybe 40gm so we're up to nearly 1.6kg, then what size LiPos, what duration do you expect compared to going glow? I don't think you're as far off as you think. ah, BVC spotted it quicker Edited By Bob Cotsford on 20/06/2020 16:11:23 Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 20, 2020 Author Share Posted June 20, 2020 Well I weighed a can of fuel, 1.8Kg for 4.55 litres. Therefore, based on a 500 fuel tank, 1800/4550x500 = 197 (ignore the weight of the can). So I was a bit out with my guess but not by that much! Intended setup is: Motor Hyperion Z4045-12 275Kv ESC 4-Max 90a Prop APC 19x10 Batteries 5000 10s Hoping for about 8 mins flight time. Regarding the potential tail weakness, I was going to mount the tail servos at the rear but was going to add some thin ply doublers to the inside of the fuse sides in that area. Edited By Ron Gray on 20/06/2020 16:58:19 Quote Link to comment Share on other sites More sharing options...
BackinBlack Posted June 20, 2020 Share Posted June 20, 2020 4.55 litres of methanol and oil should weigh approximately 3.7kgs, a little more if high nitro content. 500cc will weigh just over 400 grams, again, depending on nitro content. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted June 20, 2020 Author Share Posted June 20, 2020 Bingo! I had the wrong settings on the scales, the fuel weighs 3.9Kg, so recalc 3900/4550x500 = 429g. So, just as Bob says, 1.6Kg plus servo. Therefore the difference isn't too scary! Back to leccy plans then. Thanks guys. Quote Link to comment Share on other sites More sharing options...
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