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Antonov AN2

In Depron of course

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Simon Chaddock08/01/2019 22:51:39
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5305 forum posts
2785 photos

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.

frontleft.jpg

I even went so far as to buy a suitable 4 blade prop (10x8.5) and a 950 kV motor.

10x8.25.jpg

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.

cockpitview.jpg

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.

cyclone1.jpg

cyclone2.jpg

After a good few hours of printing a 9 cylinder radial.

ash-62.jpg

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

Colin Leighfield08/01/2019 23:54:16
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5705 forum posts
2355 photos

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.

Mike T09/01/2019 02:59:16
376 forum posts
28 photos

Historical note: a version of the ASh-62 was used in some marks of the diminutive I-16 fighter...

Callsign Tarnish09/01/2019 06:34:39
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71 forum posts
1 photos
Nice work. No concern on motor cooling?.
ken anderson.09/01/2019 10:11:23
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8342 forum posts
768 photos

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.

David P Williams09/01/2019 10:49:10
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794 forum posts
278 photos

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.

Bob Cotsford09/01/2019 10:58:03
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7723 forum posts
428 photos

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 laugh

David Mellor09/01/2019 11:03:00
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1254 forum posts
611 photos

Wow.... the AN2 is a great aircraft.

So slow and graceful. Following this build with interest......

Dave

J D 809/01/2019 11:18:54
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1035 forum posts
65 photos

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.

Martian09/01/2019 12:11:44
2077 forum posts
1010 photos

Looking forward to this build Simon , do you realise you are creating a worldwide shortage of depron 😎

Solly09/01/2019 12:44:05
228 forum posts
1 photos
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 laugh

I was in Corfu in June last year, Yes, it's still there, with a collapsed U/C leg.

Solly09/01/2019 12:44:06
228 forum posts
1 photos
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 laugh

I was in Corfu in June last year, Yes, it's still there, with a collapsed U/C leg.

Simon Chaddock09/01/2019 15:34:26
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5305 forum posts
2785 photos

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. wink 2

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.

Bulkhead 2

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.

Cowl 1 The ASh-62 is quite visible inside.

Cowl 2

Now to build a fuselage to match.

Printed formers with a 3 mm Depron skin?

Simon Chaddock10/01/2019 17:06:01
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5305 forum posts
2785 photos

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.

Fuseprint

A typical former in the main cabin area.

Former C

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.

Tenformers

With the fuselage flat side area cut out of 3 mm Depron the first three formers are glued in and the tail brought together..

Firstforms

This feels like a very 'conventional' form of construction but using unconventional materials! wink 2.

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!

sixscrap.jpg

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

Martian10/01/2019 19:32:37
2077 forum posts
1010 photos

wonderful

Simon Chaddock11/01/2019 17:00:28
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5305 forum posts
2785 photos

After some effort all the formers are in.

Allforms

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.

Allforms1

A close up of the U/C mounting that is part of the printed fuselage former.

UCmounting

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.wink 2

McG 696911/01/2019 17:53:31
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2417 forum posts
976 photos

I just would say... another masterpiece on the board, Simon.

Cheers

Chris

Stephen Jones11/01/2019 19:38:04
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2578 forum posts
1486 photos

Looks like another charmer in the making thumbs up

You are getting your monies worth out of that 3D printer wink

Steve

Edited By Stephen Jones on 11/01/2019 19:38:34

Simon Chaddock12/01/2019 20:07:45
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5305 forum posts
2785 photos

 

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..

PlankCmplt

And it is pretty empty inside!wink 2

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

reg shaw12/01/2019 21:00:47
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637 forum posts
562 photos

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.

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