Simon Chaddock Posted January 8, 2019 Share Posted January 8, 2019 With the Albatross structurally repaired but waiting for a major revision to the electric I wondered about building something else. My first thought were to the Short Seamew. I even went so far as to buy a suitable 4 blade prop (10x8.5) and a 950 kV motor. The biggest issue were those long under carriage legs cantilevered off the underside of the mid mounted wing.. Fine for a landing on an smooth aircraft carrier but by comparison any model field is "rough". By chance the Antonov AN 2 came into the picture. A four bladed prop (actually a better match) and it was specifically designed for rough field work. The AN 2 uses a big Ash-62 1000hp radial (a licensed built Wright Cyclone) and in a cowling big enough to really see the engine within it. So how about a near scale printed Ash-62 sized to match the 10" prop and with the motor completely hidden within the crankcase. After a good few hours of printing a 9 cylinder radial. Looks solid but it is completely hollow, even the push rods. and with a ruling wall thickness of just 0.3 mm. It is even printed in two colours, crankcase and push rods silver, cylinders black. Actually it is aa bit of a 'plastic kit' as it is made up of 74 printed parts all glued together! A bit unusual - build the engine first and then scale the air frame to match! Edited By Simon Chaddock on 08/01/2019 22:55:26 Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted January 8, 2019 Share Posted January 8, 2019 I flew in one of these in Croatia in 2002. When I put the seat belt on it came away in my hand. I looked down and found a bolt and spring washer on the floor, vibration had unscrewed it! I screwed it back into the floor as tightly as I could with my fingers. Very interesting flight, bumbling around the coast at about 500 ft. and what seemed to be about 50 mph. Ten seats I think, all pulled along by the big lazy ASH radial up front. A fond memory. Quote Link to comment Share on other sites More sharing options...
Mike T Posted January 9, 2019 Share Posted January 9, 2019 Historical note: a version of the ASh-62 was used in some marks of the diminutive I-16 fighter... Quote Link to comment Share on other sites More sharing options...
Callsign Tarnish Posted January 9, 2019 Share Posted January 9, 2019 Nice work. No concern on motor cooling?. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted January 9, 2019 Share Posted January 9, 2019 I watched the utterly butterly antonov land at Elvington during the 90's...I asked the pilot what it was like to fly he said"it was like a 30 ton tiger moth".....massive aeroplane... ken anderson...ne..1..antonov dept. Quote Link to comment Share on other sites More sharing options...
David P Williams Posted January 9, 2019 Share Posted January 9, 2019 I had the Maxford USA Antonov (since sold to someone else on here) and it flew very nicely, but crosswinds were a handfull with those big slab sides. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted January 9, 2019 Share Posted January 9, 2019 Is there still one parked up at Corfu looking all lopsided? I like your choices Simon, a Seamew or An2. I nearly got one of the Maxford ones on ebay last year but didn't keep my eye on the ball and was outbid. Engine first? Nothing wrong with starting your build at the front and working your way backwards, makes a change from the usual wings or fuselage first conundrum Quote Link to comment Share on other sites More sharing options...
Former Member Posted January 9, 2019 Share Posted January 9, 2019 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
J D 8 Posted January 9, 2019 Share Posted January 9, 2019 Had an AN 2 come to a small local air display. Due to very low cloud [ ceiling about a hundred feet ] most of the display was a washout. However the Antonov put on a cracking display creeping around below the cloud. It was amazing just how slow quite a large aircraft could fly and at the finish plonk down on the grass with little roll out. Quote Link to comment Share on other sites More sharing options...
Martian Posted January 9, 2019 Share Posted January 9, 2019 Looking forward to this build Simon , do you realise you are creating a worldwide shortage of depron 😎 Quote Link to comment Share on other sites More sharing options...
Solly Posted January 9, 2019 Share Posted January 9, 2019 Posted by Bob Cotsford on 09/01/2019 10:58:03: Is there still one parked up at Corfu looking all lopsided? I like your choices Simon, a Seamew or An2. I nearly got one of the Maxford ones on ebay last year but didn't keep my eye on the ball and was outbid. Engine first? Nothing wrong with starting your build at the front and working your way backwards, makes a change from the usual wings or fuselage first conundrum I was in Corfu in June last year, Yes, it's still there, with a collapsed U/C leg. Quote Link to comment Share on other sites More sharing options...
Solly Posted January 9, 2019 Share Posted January 9, 2019 Posted by Bob Cotsford on 09/01/2019 10:58:03: Is there still one parked up at Corfu looking all lopsided? I like your choices Simon, a Seamew or An2. I nearly got one of the Maxford ones on ebay last year but didn't keep my eye on the ball and was outbid. Engine first? Nothing wrong with starting your build at the front and working your way backwards, makes a change from the usual wings or fuselage first conundrum I was in Corfu in June last year, Yes, it's still there, with a collapsed U/C leg. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 9, 2019 Author Share Posted January 9, 2019 Motor cooling? My own view is that provided some air passes over, and preferably through, the motor it does not take a huge amount to dissipate the heat as there is quite a bit of surface area within the motor and inadditon its rotation ensures the air is moved about quite a bit. This the opposite of say an ESC where the heat is generated by a relatively small area which is itself buried within a plastic 'chip' and in many cases further surrounded by thick a heat shrink blanket. In my case the fairly close fitting scale crankcase will help to duct the cooling air entering from just behind the prop and through the motor. Well that the theory. A further interesting item is that despite the AN 2's size and weight the wings are simply pin jointed to the fuselage which means that all the flying loads are carried just by the rigging! My AN 2 will have a span of 48" (1220 mm) so can be built as a 'one piece' plane. At that span and with "working" rigging it is quite possible that the wings can be made of Depron with no spar. We shall see. The cowling on the AN 2 is big and circular which suggest it could also be printed. The motor bulkhead and "cone" that supports the motor mount itself. A single printed component. Note the 4 cooling air exit holes that lead directly into the fuselage. The motor and the ASh 62 are individually bolted to the motor bulkhead with captive nuts behind. The full two part cowling. The ASh-62 is quite visible inside. Now to build a fuselage to match. Printed formers with a 3 mm Depron skin? Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 10, 2019 Author Share Posted January 10, 2019 As it is a Depron build the principle of "hollow" is used where possible so lightweight printed fuselage "ring" formers will be used. The fuselage 3 view tile printed to the correct size to match the cowling. A typical former in the main cabin area. It is 6" ( 152 mm) tall and 5" (127 mm) wide and weighs just under 2 g. After some hours printing the full set of ten. With the fuselage flat side area cut out of 3 mm Depron the first three formers are glued in and the tail brought together.. This feels like a very 'conventional' form of construction but using unconventional materials! . One disadvantage of using printed formers is that there is no possibility of any 'adjustment' once printed as there can be with say a balsa or ply so they have to be "exactly" right. So once construction actually starts a few have to have their CAD files altered and be reprinted. Easy enough to do but time consuming. The six scrap formers - so far! With absolutely nothing inside the fuselage at least there should be no problem positioning the battery. Edited By Simon Chaddock on 10/01/2019 17:13:30 Quote Link to comment Share on other sites More sharing options...
Martian Posted January 10, 2019 Share Posted January 10, 2019 wonderful Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 11, 2019 Author Share Posted January 11, 2019 After some effort all the formers are in. At this point i realised I had completely forgotten the undercarriage mounting that is outboard of the fuselage! Fortunately UHU POR remains soft and rubbery for quite some time (days) so with care it was possible to extract the offending former and replace it with a new one. A close up of the U/C mounting that is part of the printed fuselage former. The bracket carries the top if the spring unit and is also the attachment for the flying wire. The fuselage is still a bit wobbly but the rigidity increases as piece of the Depron skin goes on. Quote Link to comment Share on other sites More sharing options...
McG 6969 Posted January 11, 2019 Share Posted January 11, 2019 I just would say... another masterpiece on the board, Simon. Cheers Chris Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted January 11, 2019 Share Posted January 11, 2019 Looks like another charmer in the making You are getting your monies worth out of that 3D printer Steve Edited By Stephen Jones on 11/01/2019 19:38:34 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 12, 2019 Author Share Posted January 12, 2019 Just fuselage planking. The basic fuselage skin substantially complete using thin strips of masking tape to hold the last plank in place until the glue dries.. And it is pretty empty inside! The ESC will go on the cockpit floor with its fins sticking out underneath in the air stream just about where the oil cooler is in the full size. Edited By Simon Chaddock on 12/01/2019 20:08:30 Quote Link to comment Share on other sites More sharing options...
reg shaw Posted January 12, 2019 Share Posted January 12, 2019 Quality job. This might possibly be the first model An2 to fly at anything like scale speeds! Will it have a mass of flappery Simon? How many printers have you worn out up to now?!! Ian. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 12, 2019 Author Share Posted January 12, 2019 reg I must say I am pleasantly surprised how well the cheap A8 is performing. The only bit I have actually replaced is the extruder heating element. Entirely my own fault as I broke one of its wires when i changed over a nozzle.. Yes it will have all the flaps. Full span on the lower wing, half span on the upper. From this video it appears the upper flaps travel a bit more than the lower. I don't think the ailerons droop. . Edited By Simon Chaddock on 12/01/2019 23:39:04 Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted January 13, 2019 Share Posted January 13, 2019 You wil have some fun with this one Simon, a great choice. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 13, 2019 Author Share Posted January 13, 2019 Now comes the tricky bit the scale printed undercarriage. With the lower wing centre section in place all the undercarriage mounts are available so after many hours of both CAD and printing........ All printed, even the pins are cut off bits of filament. The only metal will be the stub axles' The printed spring units are in about the fully relaxed position but should give nearly 1" (25 mm) of travel once the appropriate rate springs are installed. Part of the design philosophy is that it should shear off before tearing out the fuselage mountings as I can always print more undercarriage. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 15, 2019 Author Share Posted January 15, 2019 With temporary too strong springs in the spring units the fuselage can sit on its printed/Depron wheels. The tailplane and elevator. 2mm Depron skins over a Depron shear web. The 5 g elevator servo. The tail plane is braced. The brace is also 3 mm Depron but with a balsa leading and trailing edge. The elevator halves are joined with a short section of thin wall glass fibre tube. To keep things light and simple the elevator is top tape hinged with invisible (matt) tape. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted January 20, 2019 Author Share Posted January 20, 2019 The bottom wing under construction. A rather unusual construction with 2mm Depron skins and printed ribs but nothing else, no spar. no shear web, nothing! It will rely almost entirely on the rigging for rigidity. Like the full size it also has full span flaps. The complete wing glued in place on the fuselage and temporarily supported with string! At 50" span it is only a bit smaller than the 55" Maxford AN 2 kit but it will of course be a lot lighter! Quote Link to comment Share on other sites More sharing options...
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