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Antonov AN2

In Depron of course

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Simon Chaddock12/01/2019 23:38:04
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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

Colin Leighfield13/01/2019 21:49:53
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You wil have some fun with this one Simon, a great choice.

Simon Chaddock13/01/2019 22:23:46
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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........

UClegs1

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. wink 2

Simon Chaddock15/01/2019 11:26:55
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With temporary too strong springs in the spring units the fuselage can sit on its printed/Depron wheels.

UCwheels

The tailplane and elevator. 2mm Depron skins over a Depron shear web.

Tailplane1

The 5 g elevator servo.

Eleservo1

The tail plane is braced.

Tailbrace

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.

Simon Chaddock20/01/2019 16:12:47
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The bottom wing under construction.

Bottom wing1

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. wink 2

Like the full size it also has full span flaps.

The complete wing glued in place on the fuselage and temporarily supported with string!

Low wing1

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!

Simon Chaddock23/01/2019 00:12:05
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The top wing complete with its 4 servo.

Wings cmplt1

Not actually fixed, just resting.wink 2

David Mellor23/01/2019 12:55:40
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611 photos

Looking very nice, Simon.

Bob Cotsford23/01/2019 13:40:39
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Another sprint builder! Your work rate is mightily impressive Simon, and the result looks really good. Do you have any reservations regarding the strength of printed components such as those used in the undercarriage?

I like the printed formers but isn't it a lot of work for a one-off?

Edited By Bob Cotsford on 23/01/2019 13:41:49

Simon Chaddock23/01/2019 16:54:29
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Bob

Yes it is a lot of CAD and printing time for a one off but for me part of the fun is seeing if I can actually make the printed parts 'fit for purpose' which for a Depron build really means light enough.

The intention with the undercarriage is that it will indeed "rip out" hopefully leaving the fuselage mounting points intact. Its easy enough to print a replacement undercarriage. wink 2

The saving grace is that in any "crash" will be its light weight with a correspondingly low flying speed.

The nearest comparison I can find is the Maxford AN 2 kit which a 55" span weighs in at 96 oz. Mine is a bit smaller at 50" span but should weigh just a fraction of the Maxford figure! smile o.

The latest picture with the wing struts in place.

Wing struts1

Now to work out how to secure the load bearing rigging to Depron!smile o

Simon Chaddock25/01/2019 23:08:38
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5306 forum posts
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A short video of all six wing servos under test coupled up to a servo tester in 'auto' mode.

Still got to work out how to do the functional rigging.

Geoff Sleath26/01/2019 17:07:04
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3188 forum posts
247 photos

Quite an ambitious model Simon. I hope we'll see it at Ashbourne some time. You're one of the people I know who make me wonder why I bother

I witnessed a full-size crash caused by an Antonov AN2 (Utterley Butterly). It was being used at Hucknall for people to jump out of for some reason (they did have parachutes ). We were flying models at one end of the runway. The Antonov took off, presumably back to its base, and a Jodel followed it about a minute later. The Jodel stalled and crashed just after leaving the ground and hit the ground just short of the RR factory fence.

Fortunately neither occupant of the Jodel was seriously hurt but seeing a full-size aircraft crash is very sobering.

Apparently the crash was caused by the turbulence created by the large biplane., not something I'd ever considered before.

Geoff

Simon Chaddock26/01/2019 21:45:46
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5306 forum posts
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Geoff

Thanks for the kind words.

It is easy to forget that the AN 2 is big and heavy plane with nearly 10 times the power of Jodel.

I have only witnessed 1 crash when an Auster at Biggin Hill suffered some sort of failure on the climb out and crashed just outside the perimeter. Did not see the actual impact but it burst into flames and I belive both occupants perished. Very sobering.

The latest trial has been to fix attachment points for the load bearing rigging.

The first panel.

Rigging1

The wires have been painted black so the camera can see them!

Really just a 'test' to see how practical (and rigid!) it is. It will be removed and only fully installed once the air frame has been painted.

Edited By Simon Chaddock on 26/01/2019 21:48:51

Colin Leighfield26/01/2019 22:47:07
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As with all of your projects Simon, ultra-light weight is the passport to success. I don’t doubt you are going to get a very scale-ish air speed, probably in the range 5-10 mph!

Simon Chaddock30/01/2019 15:45:51
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As the rigging would make the painting a bit more difficult its getting painted!

Paint1

Nothing very clever. The acrylic blue has added a bit of weight but the bare Depron was a bit rough so a light sand between two coats has produced a reasonable finish.

The white Depron wing only needed to be 'shown the brush' to get an even colour.

The undercarriage spring units have been reprinted to accommodate the softer smaller diameter softer springs there is now a full inch of travel available. wink 2

Simon Chaddock03/02/2019 22:43:59
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Somewhere along the line I made a silly mistake as the printed cowling was 10 mm too long. Only really noticed it with all the rest of the plane in place! Still not the end of the world as it is just a mod in CAD and 4 hours printing. Fortunately the ASh-62 can be simply transferred across.

So with the new shorter cowling on.

Cowl on 1

I suspect the wheels will need to be moved forward a bit as it seems to topple forward rather too easily with the CofG in about the right place. Again with a bit of CAD work it is not difficult to alter the U/C leg geometry and reprint them with the wheels 10 mm.forward.

At least the printed ASh-62 looks the part.

Cowl on 2

It just needs a printed representation of the AN2's characteristic variable pitch hub. wink 2

Edited By Simon Chaddock on 03/02/2019 22:55:30

Bob Cotsford03/02/2019 23:24:29
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7724 forum posts
428 photos

Simon, so how did you anchor the rigging in the end? It certainly looks the part now. I could almost be tempted to try a Depron build myself.

Simon Chaddock04/02/2019 01:33:32
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5306 forum posts
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Bob

I eventually used these.

Rig anchor 1

Not metal but silver painted acetate sheet!

Each is glued (UHU POR) on the outer face of the appropriate rib through a carefully placed fine slot cut through the Depron skin.

Rig anchor 2

once the glue sets it takes quite a pull to dislodge them as the glue is in shear.

The rigging is 15 lb mono filament line. It does have some stretch but as it is grossly over strength for the actual load it wont actually "give" that much before something else breaks!

As long as the AN2 ready to go can be lifted by its wing tips (a test least equivalent to pulling 4g) I will be happy. wink 2

Simon Chaddock05/02/2019 11:58:20
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At last its all but finished and taken outside for the first time!

05jan19a

05jan19c

Just a few details to add like painting the cabin windows and fixing the battery on the cockpit floor to give a suitable CofG.

With a 2200 mAh 3s it weighs 25.5 oz (723 g) giving a wing loading of 6.4 oz/sqft.

One problem of doing a "design it as you go along" type build is you end up with lots of areas where you could do better next time!

Hopefully when the weather is right there will be a video of its maiden! wink 2

Martian05/02/2019 19:31:43
2077 forum posts
1010 photos

she is looking brilliant Simon good luck with the maiden

Colin Leighfield05/02/2019 22:33:47
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5705 forum posts
2355 photos

I think this one is a safe bet, it is going to fly well.

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