Andrew Price 2 Posted November 6, 2017 Share Posted November 6, 2017 You just do not do easy do you Simon? Quote Link to comment Share on other sites More sharing options...
Andrew Price 2 Posted November 6, 2017 Share Posted November 6, 2017 You just do not do easy do you Simon? Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 8, 2017 Author Share Posted November 8, 2017 The wing plan printed out to give an idea of how big, or not, it is going to be. It gives a 66" (1980 mm) span but like all modern airliners it is very highly tapered. 14" (360 mm) root chord but only 2.5" (65 mm) at the point where the tip starts to 'curl up' by 90 degrees. That's a 6:1 taper which would normally be considered to give 'horrible' stall characteristics. I suspect at my flying speeds the outer bit of the wing won't do much apart from create drag! Still it does have a reasonable area of just about 2 sq ft. Now whether the whole plane will come in anywhere near my target of 24 oz (680 g) is too early to say. Quote Link to comment Share on other sites More sharing options...
Erfolg Posted November 8, 2017 Share Posted November 8, 2017 Now this will be interesting Simon. The tip chord is very small relative to the root. It is also so narrow, that I wonder how well the tip area will work. At a personal level, i defiantly would have a good few degrees of washout. Probably so much that often the lift contribution would be near to zero. Being a mardy, I would be after some control near or at the stall. Again being me, I would also cheat at the wing tip, I would increase the chord. Yes, i am definitely chicken. Considering the model, it really is not the sort you would normally loop, roll, fly inverted, stall turn (intentionally). Best suited visually to circuits, low passes, to avoid brown trousers. That Russian aircraft really does look good. It is a great pity that I will never see it fly in the Depron. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 8, 2017 Author Share Posted November 8, 2017 Erfolg My intention is to keep the wing exactly to scale as it is very much part of the design. I will just have to live with any 'undesirable' characteristics. In my experience swept wings tend to have 'gentle' stall characteristics due in part to the outward airflow but also their flexibility giving 'automatic' washout. I will have to watch out that the same flexibility does not result in reduced aileron effectiveness! On the plus side the long fuselage and substantial fin (required in the full size for single engine operation) should mean it will recover rapidly from any 'wing drop' situation provided of course there is sufficient height! Aerobatics? I doubt very much it will be able to roll effectively but I will be a bit disappointed if it can't loop!. Edited By Simon Chaddock on 08/11/2017 22:30:41 Quote Link to comment Share on other sites More sharing options...
Martian Posted November 9, 2017 Share Posted November 9, 2017 Loving your journey with these materials really excellent stuff for me though it would be like juggling with jelly Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 12, 2017 Author Share Posted November 12, 2017 The next critical component is the motor and fan or rather the tiny (3x3!) prop. They have been purchased through HK and are intended for racing drones. Obviously these are the latest 'thing' so are surprisingly cheap and were on offer too! The Trent nacelle. At this early testing stage I decided to mount the prop as a pusher right at the back of the nacelle. I have used this layout on a previous ducted prop (as well as a couple of EDFs) on the basis that there is nothing in the high speed slip stream so it is likely to give the maximum static thrust.. This layout also results in a compact & rigid unit ensuring the prop stays clear of the duct walls. I have tested it on a 3s and although it pushes quite hard I suspect it will need a 4s set up to deliver the thrust I would like. In addition the pusher layout precludes using a scale Trent tail cone so the 'flight' version may revert to a tractor arrangement with the prop forward well inside the duct. The next task is to build a test stand so I can accurately measure the thrust. Edited By Simon Chaddock on 12/11/2017 17:36:09 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 13, 2017 Author Share Posted November 13, 2017 After a bit of consideration I actually printed a test stand 'mushroom' to fit directly onto the motor mount. It is filled with plaster both to support the thin walls and to add a bit of mass. Sitting on the kitchen scales it generates 121 g thrust with a fully charges 3s drawing 4.1 A. Even with two this level of thrust is sufficient for a 680 g plane but on 4s hopefully it will be - assuming it all hold together! Quote Link to comment Share on other sites More sharing options...
Callsign Tarnish Posted November 14, 2017 Share Posted November 14, 2017 Simon, I'm very much of the old school, traditional builder, mentality but I have to say it's quite inspirational seeing what the more adventurous of us can achieve with new materials. Enjoying this. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 15, 2017 Author Share Posted November 15, 2017 CT Thanks for the kind words. I have just noticed in my previous post I missed out a word! It should have read "..this level of thrust is not sufficient for a 680 g plane...."! The internal diameter of the first test duct was set slightly 'generous' to ensure it cleared the prop. As it turned out not only was the motor mount and duct quite rigid but the prop was also pretty accurately centred as well. To reduce the prop tip clearance and so hopefully improve the thrust I printed a thin narrow ring to be glued inside the duct. .The prop tip clearance is now about 0.5 mm. And it worked! On the same fully charged 3s in generated a reliable 132 g of thrust.. Not a dramatic increase (about 9%) but it is virtually for 'free' as there was very little change in the current draw. My best guess suggests the complete nacelle is likely to weight 75 g. A large part of this total is from the 'printed' parts as the motor and prop themselves only weighs 30 g. I would like to get the weight of a 'bare' nacelle down to 30g by incorporating some improvements to the printing technique although it is likely to fill up my waste bin with more 'unsuccessful' prints! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 17, 2017 Author Share Posted November 17, 2017 Still awaiting delivery of the 4s ESCs so in the mean time move on to designing the nacelle pylon. To save weight the intention is to print the pylon in conjunction with the motor mount and as before include a 'channel' within it to carry the motor wires into the wing. The light weight 'pusher' motor with an integrated pylon. By reducing the print wall thickness and using a Depron external skin the motor mount ends up about 12 % lighter. However due to the way the pylon and motor mount are designed it does not print well and lacks some rigidity. Unfortunaely I cannot see a way round it without adding additional weight. The tractor prop version has a slightly different internal structure and does not have the same print issue so this layout will be the chosen development route. There is a slight weight penalty but worth the extra rigidity gained. As the motor now faces forward it allows a 'representation' of the Trent tail cone to be used. The forward part of the nacelle is next. Overall this is proving to be a rather protracted development process, I probably could have simply built a complete nacelle in Depron quicker, but by using printed major components I know the second nacelle will be much quicker to do and be exactly the same! Quote Link to comment Share on other sites More sharing options...
Erfolg Posted November 17, 2017 Share Posted November 17, 2017 If it were my project or model, one of my concerns would be what will happen to the Nacelles and supports when the model lands? Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted November 17, 2017 Share Posted November 17, 2017 I just know it’s going to work! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 19, 2017 Author Share Posted November 19, 2017 Erfolg Landing is a concern however: 1 The landing speed will be low. 2 Without flaps the landing will be markedly nose high The nacelles are well ahead of the CofG so providing the grass is short the hope is it will '3 point' using the generous rounded underside of the nacelles as skids. The 'bare' 77 mm nacelle with a planked Depron skin alongside the all printed 50 mm version. The 4 blade 3x3.5 mounted as a tractor within the nacelle. Complete with the pylon it weighs 70 g. Edited By Simon Chaddock on 19/11/2017 00:03:22 Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted November 19, 2017 Share Posted November 19, 2017 Wow their is a big difference in size when seen side by side. Steve Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 23, 2017 Author Share Posted November 23, 2017 With the test nacelle finished the next issue is to design the bit it has to fit to - the inner wing panel. Like all modern airlines the wing is broad and remarkably thick right at the root but rapidly tapers down to a thin transonic section once beyond the engine nacelle. I decided to use 'printed' wing ribs as each is of a very different size and section. By pure luck rather than intent the biggest root rib just fits on the printer bed! The rapidly changing set of ribs. The biggest asset doing it like this is all the ribs have been generated from a single master set of dimensions by changing just the rib length and depth. they are accurate to 1/100 of a mm and repeatable at the press of button. To make life a bit harder the wing has to built upside down as only the top surface is truly flat. The single balsa/Depron/balsa spar is full depth such that its balsa flanges are flush with the surface of the 2 mm Depron skin. Although light and stiff the big downside of such lightweight printed components is they are virtually non repairable and have to be completely replaced if damaged in any way. Not easy to do with a wing rib. . Edited By Simon Chaddock on 23/11/2017 12:03:52 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted November 27, 2017 Author Share Posted November 27, 2017 The first inner wing panel complete. The nacelle pylon fits in the wing slot. The complete wing and nacelle (including the motor and ducted prop) weighs 98 g. As it all seems to fit together the 8 individual parts for the second nacelle are printed off. This is where printing really excels. Although the above represents about 4 hours printing it only requires a touch of a button (well almost!) and all the prats fit together perfectly. Just out of interest a comparison if the root and tip wing ribs. It does show just how tapered the wing is and the curved up tip "winglet" is even smaller still! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 1, 2017 Author Share Posted December 1, 2017 The outer wing panel is a remarkably simple affair. All 2 mm Depron with no ribs or spar just a pair of shear webs. The 'curled up'wing tip is sanded from a pre-formed blank of 4 laminations of 2mm Depron glued together and held with rubber bands over a suitable diameter cardboard tube until dry.. The tape top hinged aileron is cut out from the wing. and a 3.7 g servo inserted through the wing bottom skin. At the inboard end of the aileron the wing is just thick enough to hold the servo which is simply glued between the top and bottom surfaces. The linkage has considerable mechanical differential incorporated in the linkage. The inner and outer panels glued together. This shot does rather highlight its extreme root to tip taper. With no ribs in the outer panel and open braced inner wing ribs feeding the servo wire through is fiddly but no real problem. The half wing and the nacelle, complete with motor and prop, weigh 140 g which suggests the target weight of 24 oz (680 g) is achievable. Edited By Simon Chaddock on 01/12/2017 11:09:25 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 5, 2017 Author Share Posted December 5, 2017 To save weight the motor wires are extended using 16 AWG lacquered magnet wire. A short test on a 2s to make sure the soldered connections are sound. With the nacelles glued into the wing and all the wires brount through the wing down to the root the wing halves can be glued together. The nacelle glued into the wing. All complete it weighs 9 oz (255g) Quote Link to comment Share on other sites More sharing options...
Martian Posted December 5, 2017 Share Posted December 5, 2017 it is looking brilliant Simon Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted December 5, 2017 Share Posted December 5, 2017 I'll second Martian here, Simon. You're an extraordinary model builder. Cheers Chris Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 6, 2017 Author Share Posted December 6, 2017 Thanks for the kind words gentlemen but things do go wrong! The centre part of the fuselage was originally just a 'test' to prove the construction technique but it got incorporated into the working fuselage. At that time I had not even considered the wing construction or its section so the bottom line is the wing does not fit properly onto the underside of the fuselage! After a bit of thought the only solution was to reprofile the wing mount which required the fuselage underside to be cut open and I would then have a find a way to repair several un-repairable printed formers. . Printing new cross beams and simply gluing them in proved relatively simple. The wing will now fit 'snugly' and more important at the correct angle of incidence. With the fuselage underside temporarily 'open' it will also make running the long rudder and elevator servo wires a great deal easier so the tail plane and fin are top priority! Edited By Simon Chaddock on 06/12/2017 00:55:39 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 8, 2017 Author Share Posted December 8, 2017 The tail plane in progress. It is quite modest in area but by comparison the elevators are pretty generous. There are no ribs, just a shear web and 2 mm Depron skins. A printed U channel spar supports the elevators. The elevators them selves have a hard balsa leading edge to provide the necessary torsional stiffness. The horn will be on the inner edge of each elevator as the micro servo can only contained within the tail plane at its root. The fin will be built directly onto the tail plane. The rear of the fuselage will then be cut open and the whole tail assembly glued in place Well that's the plan! . Edited By Simon Chaddock on 08/12/2017 16:46:26 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted December 9, 2017 Author Share Posted December 9, 2017 the tail fin fixed to the tail plane. On the full size the fin spar passes in front of the tail plane so it needed some 'printed' brackets to fix securely and with the right sweep angle. When the tail plane assembly is mounted in the fusealge all the bracket will hidden. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted December 9, 2017 Share Posted December 9, 2017 Looking forward to the video Simon. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.