Ron Gray Posted March 28, 2020 Share Posted March 28, 2020 Not too sure if anyone is interested in this 'project ' that I've just started, so dipping my toe in the water, so to speak. To cut a long story short, when flying this model last year (May / June) I suffered a dead stick whilst quite low which resulted in me putting it down in a ploughed field short of our runway. The damage was quite severe, the belly was ripped out and there was also some damage to the wings and tailplane. I put it all to one side but with the current C19 situation I decided to get to work on the repairs. I decided that I was going to re-engine it with a DLE35 RA which was going to be a challenge bearing in mind the fuse was not designed for a canister type exhaust. This as it before the 'landing' And here are some photos showing the damage to the fuse Note that I've already started on the work to house the can by cutting out a hole in the bulkhead to allow the exhaust through. Now the challenge is not just to get the can in place but also to make sure that the U/C will fit, bearing in mind that it will have to be lowered to allow the can through underneath. Edited By Ron Gray on 28/03/2020 22:50:45 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted March 28, 2020 Share Posted March 28, 2020 Interested Ron, you gonna build the can in and repair around it ? Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 28, 2020 Author Share Posted March 28, 2020 Hi John, the plan is to build a tunnel for the can so that it can be removed! Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted March 28, 2020 Share Posted March 28, 2020 I'll be watching then, I've a Sukhoi could do with a mod. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 29, 2020 Author Share Posted March 29, 2020 The first part of the re-build was to build new formers / part formers as a lot of them had been ripped out in the crash (see photos above). A couple of months ago I bought a 3D printer so I decided to use my newly acquired skills to design replacement formers but where strength and heat were involved I would stick with traditional ply ones. This is the basic shape that most of them followed, the legs allowing me to graft them onto the remains of the original ones. And the various different sized ones stuck in place. Ply formers used where the can is going to be located with cutouts for the tunnel. And the tunnel formed with thin balsa which had been wetted and bent around the can to give the basic curve. Thin balsa extended up the sides of the tunnel and longeron supports added plus end cap. I then glassed the tunnel with 2 layers of glass fibre cloth. And trimmed back. And then the tunnel was lined. Edited By Ron Gray on 29/03/2020 09:34:11 Quote Link to comment Share on other sites More sharing options...
Former Member Posted March 29, 2020 Share Posted March 29, 2020 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 29, 2020 Author Share Posted March 29, 2020 The can is shown unsupported, when it has its rear support in place it will raise it to give an air gap although it will be quite close at the front of the tunnel. I'm not too concerned about it as the tunnel will be open to the air. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 29, 2020 Author Share Posted March 29, 2020 Rear support bracket fabricated and fitted, hopefully you can see the air gap between the can and tunnel. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 29, 2020 Author Share Posted March 29, 2020 A bit more progress, this part of the re-build is very slow as I am really making it up as I go along plus replacing missing parts as I do. I'm also trying to build in additional strength where it is needed. Talking of which, I added some 'load spreaders' to the rear of the U/C former: Some additional strengthening for the U/C bearer plate Which form a nice 'chamber' around the exhaust pipe (more on that later, but keep in mind that I do have a 3D printer!!) There is a former here which supports the outside fuse sheeting, you can just see it curving away in the background. Its opposite number was torn out in the crash so needs to be replaced. A new piece was cut out using the scroll saw (I haven't gone completely over to 3D printing!) And stuck in place Using the offcut as a clamping 'tool'. Next up will be the sheeting in of the front section and side sheeting around the U/C. Unfortunately I have discovered that I'm out of 5mm sq strip so have ordered a load plus other bits from SLEC. C19 is a bit of a nuisance in that regard as SLEC are only about 15 mins drive from me so normally I would have gone and picked it up. Hey ho, lots of other things to do whilst I await its delivery, the wings need a careful inspection, I know one took quite a hit along its root, so I'll peel back the covering to see what we have to deal with! Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted March 29, 2020 Share Posted March 29, 2020 Ah leaving it out in the air, hadn't realised. Not much wood in a wing these days, as long as it's still true it'll be straight forwards ish. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 29, 2020 Author Share Posted March 29, 2020 I just found some more sq strip in a bundle of balsa etc that is was earmarked for another build, so on with the fuse! Quote Link to comment Share on other sites More sharing options...
Peter Jenkins Posted March 29, 2020 Share Posted March 29, 2020 Well done Ron. Repairing these lightly built models is not easy so using a 3D printer to make some of the formers is an interesting idea. Which make of can are you using? My 35RA with a JMB can only failed the 82 db test on a windy day with the wind blowing into the back of the prop - an unrealistic scenario in the real world! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 29, 2020 Author Share Posted March 29, 2020 Thanks Peter, it certainly is a challenge, this Sbach was certainly built light! Regarding the can, 'unfortunately it's the DLE one, I say unfortunately because I would have preferred a Zim one but I already had this one sitting, unused, in the workshop. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 31, 2020 Author Share Posted March 31, 2020 Continuing on with the repairs I finished off the fitting of the longerons and then decided to sheet the whole of the repaired section of the fuse. Next up the covering Now in a post above I mentioned that the 2 ply U/C formers made a nice chamber around the exhaust so I am utilising this as a vent chamber and have designed and printed an air scoop for it which will also vent the can tunnel. Now time to re-fit the can And to cut down the exhaust deflector I'm quite please with the end result. Now i've got a couple of bits to fix on the inside of the fuse then it's onto the tailplane and main plane. Just noticed tonight that one half of the tailplane has been knocked back and looks like the root rib maybe damaged. Good job it's a bolt on, that will be the next job after the fuse. Onwards and upwards! Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted March 31, 2020 Share Posted March 31, 2020 Nice work Ron. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 31, 2020 Author Share Posted March 31, 2020 Thanks John, I’m hoping that the repairs to the tail and mainplane won’t be as fiddly as the fuse! Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted March 31, 2020 Share Posted March 31, 2020 Hi Ron. Nice repair work. It's a job I hate doing, so good on you for making such a nice job and improving the model at the same time. I have a question though if you don't mind. What's the thinking behind your 3D printed air scoop? The way my mind works, it looks like it will push air into the fuselage, creating a high pressure area, preventing hot air from escaping - and possibly opposing the natural flow from cowl to tunnel. Wouldn't it work better the other way round, sucking hot air out? Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted March 31, 2020 Author Share Posted March 31, 2020 Hi Gary The problem with the way the 'plane is designed is that there is no air flow from cowl to tunnel, after all it wasn't designed for a canister type exhaust. Also there is no direct route for air to get into the fuse as the can tunnel is sealed off from the rest of the fuse apart from a small slot. So the logic is that I do want to force air into the tunnel, I don't see that being a problem as the can tunnel is completely open to the air but in forcing air into it, some will go through the small slot into the fuse directly onto the fuel tank which sits above the can tunnel. I will fit an extract hole in the rear of the fuse to allow a flow of air. To be honest it's all guesswork and I haven't a clue if it will work or for that matter make any difference, after all my GP Giant Revolver and SU26 both run with DLE 55s exhausting through cans and neither have had any heat problems and they haven't got air being forced through them! Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted March 31, 2020 Share Posted March 31, 2020 Yep, guesswork on my part too. It just looks to be the wrong way round to my eye. At least you have several options to try for best results - both ways round, blank plate or left open Quote Link to comment Share on other sites More sharing options...
Peter Jenkins Posted March 31, 2020 Share Posted March 31, 2020 Good job Ron! Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted April 1, 2020 Author Share Posted April 1, 2020 You are correct in one respect Gary, I have used a naca duct shape but it is upside down and the wrong way round! But, like I said, this is guesswork hence why it is a removable piece. Thanks Peter. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted April 2, 2020 Author Share Posted April 2, 2020 No too sure if anyone wants to see more of this re-construct or have I bored the pants off you already? Not a problem if I have!!!! (well, let's face it. if I have then it's too late anyway ) Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted April 2, 2020 Share Posted April 2, 2020 Carry on, we can always learn from others, recently repaired a Slick wing/aileron for a mate, it's interesting once you get under the covering. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted April 2, 2020 Author Share Posted April 2, 2020 Well one thumbs up is enough for me John, so I'll continue. On first inspection the damage to the tail wasn't too bad, a crack in one half was my initial thought. However, when I looked at it again I saw that one half was not only damaged but was also bent back from the fuse. No problem, the tail is in 2 halves so simply unbolt it and remove to fix. Uh, no, the previous owner had glued the alloy wing spar tube into the carbon tubes so a simple slide off was out of the question. After careful (well not so careful) brute force I was able to break the tube free, trouble was it was the the carbon tube that broke free and it was the other tail half it broke free from! Damage The wing tube pulled out from the wrong half At least I was now able to bend the alloy tube straight so that the broken half sat parallel to the fuse, but in doing so the dowel locator pegs had to be cut off. This meant that I then had to somehow fit new ones but I couldn't get the tailplane off to drill out the old one! Using a small drill bit at an angle I managed to remove enough of the dowel. But how to fit a new dowel if I can't pull the tail away from the fuse? answer was to make a long dowel that went right through the fuse and would also serve for the other tail half. Having spent far too long on this part I decided to rest my brain and tidy up a couple of things inside the fuse. Firstly I had to raise the rudder servo due to the new can tunnel. And the last (hopefully) fuse job was to re-attach the RX mounting tray (mustn't forget the second RX which is in another 'plane!). Now back to the tail. The covering was stripped back and the repairs made. Then recovered So that completes the fuse re-build. Next up, the wings and I was not looking forward to this part as my memory told me that one was in a bit of a state! Funny how memory can play tricks with you, damage was nowhere near as bad as I remembered and considering the state of the fuse it really is quite amazing. However, I tell myself that it must have been good flying to have landed it level in the middle of that ploughed field! One wing, looks like a spat puncture Other wing, goodness knows what caused this Repairs to these areas tonight. Edited By Ron Gray on 02/04/2020 17:11:09 Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted April 2, 2020 Share Posted April 2, 2020 Looking good Ron, a bonus there's no fancy film job to redo ? A model I've always wanted. Quote Link to comment Share on other sites More sharing options...
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