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DH 91 Albatross

Exceptional streamlining?

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Simon Chaddock14/06/2018 00:34:08
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5249 forum posts
2738 photos

Just before starting the rear end I though I had better get the retracts working.

First cut out the wheel wells. A bit tricky when the actual retract units are completely buried under the skin!

Wheel well1

The U/C legs are bent from 1/8" SS wire.

Wheel down

Wheel down

Wheel raised.

Wheel up

As the legs have absolutely no 'give' in them the wheels incorporate some spring movement within the hub.

Sprung wheel

All 3D printed the outer covers are only glued on at their perimeter so allowing the axle to move,.not a lot (4 mm) but better than none!

A 'tyre' made of 3 Depron rings is glued on around the hub perimeter to bring the diameter up to 60 mm.

The finished wheel weighs 5.1 g

Simon Chaddock18/06/2018 11:03:58
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5249 forum posts
2738 photos

The completed retracts under test.

The original had additional hinged panels to completely cover the wheel wells when retracted.forbisherfront.jpg

However apart from the difficulty of actually moving them I fear they would be far too vulnerable for a 'non scale' grass field so they will be left off! wink 2

Simon Chaddock21/06/2018 19:28:58
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5249 forum posts
2738 photos

The L & R tail planes.

Tail plane 1

Just 2 mm Depron skins over Depron shear webs so creating a symmetrical section. Each elevator half has 3 3D printed hinges.

After much thought I decided to use individual servos (4) for each surface. Even using micro servo this will add weight right at the back but worth it to avoid complex linkage.

The servos are almost completely hidden with only the arms and horns exposed.

Tail front

The LH elevator servo.

Elevator servo

The LH rudder servo.

Rudder servo

Of course the RH servos have to be the other way round so the paired surfaces move in unison.wink 2

The RH tail plane under test using a servo tester.

Still slow going but technically all the servos are now installed but just in 3 separate pieces of the plane!

Simon Chaddock25/06/2018 12:40:11
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5249 forum posts
2738 photos

The rear portion of the fuselage is next using my usual planked Depron skin but over over the printed formers.

Fuse rear 1

Not too difficult as this part of the fuselage is a straight sided cone although it is offset vertically.

Completed

Fuse rear 2

It weighs 16 g.

The tail plane halves glued in place.

Fuse tail 1

Despite my concern at the weight using 4 individual servos was probably the right choice as the tail end of the fuselage has very little room inside!wink 2

It has been tested so the next job is to wire up the motors and the ESCs in the wing.

Simon Chaddock20/07/2018 11:25:18
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5249 forum posts
2738 photos

This is a very slow build but a bit of progress, the motors do all turn and the desired way too! Of course having counter rotating props is not actually scale as on the original they all turned in the same 'Gipsy' way - or in other words the opposite to virtually every other small engine manufacturer!  

Only 'tick over' as the wing was not restrained in any way but very slow and stable none the less.
Just a test 'lash up' so there is quite a bit more to organise the wiring and to install the BEC as well.

Edited By Simon Chaddock on 20/07/2018 11:30:23

Simon Chaddock31/07/2018 14:53:33
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5249 forum posts
2738 photos

The wing centre section showing the Lemon 'stab' Rx, the four ESCs and the UBEC.

Stab Rx

A full test of the wing functions using RC.

The final operation is to install the wing retaining bolts but to do this I also need the fuselage centre section.wink 2

Simon Chaddock07/08/2018 10:39:21
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5249 forum posts
2738 photos

The fuselage mid section built vertically using my "terribly wobbly to start with" technique. wink 2

Mid fuse 1

The formers are 3D printed.

The 6 mm Depron plate between two formers has a 3D printed surround that incorporates the 'nuts' for two of the wing hold down bolts.

Wing mount box

The holes are printed the correct size to be tapped to suite the 4mm nylon bolts.

Mid fuse 2

The completed centre section showing the wing mounting cut out.

Fuse mid wing

More small printed bits will be needed to secure the bolts to the wing.

As this is taking so long I placed the bits together to get an idea of what it will look like.01 Aug 18a

Also to convince me that some progress is actually being made!smile o

Simon Chaddock20/08/2018 01:00:22
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5249 forum posts
2738 photos

With the wing bolt mounting complete the tail and centre fuselage sections can be joined and with removable nose section built the fuselage is structurally complete.

fusecmplt1.jpg

The nose section is retained by four lugs with a twist on/off action courtesy of special 3D printed formers.

Once in place the nose is prevented from turning by a retaining pin activated by sliding the shallow dome. In the full size it is one of 4 top hatches.

nosepin1.jpg

Yet more 3D printed parts! wink 2

Time to start filling , sanding and painting.

Simon Chaddock24/08/2018 18:00:15
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5249 forum posts
2738 photos

Very slowly but its getting there.

All the bits together. the nose paimted and sitting on its undercarriage.

Assembled 1

After a but more filling, painting and windows stuck on the virtially complete fuselage.

Fuse paint 1

Now to do the same to the wings. wink 2

Erfolg24/08/2018 18:07:09
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11124 forum posts
1086 photos

I think only the Lockheed Super Constellation looks nicer, or perhaps the Boeing Stratocruiser comes close.

Even so, a tremendous model to build, ad I stand in awe of your willingness to embrace 3d printing in conjunction with Depron to build an outstanding model.

Is this the way of the future for home building?

Simon Chaddock25/08/2018 00:57:43
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5249 forum posts
2738 photos

3D printing certainly makes it relatively easy to create small scale parts - like this exhaust pipe.

Exhaust pipe

It is a true hollow pipe so it only weights 0.4 g. As there is one for each bank of cylinders 8 identical are needed.

The down side is it takes longer to get the design exactly right than it does to print 8! wink 2

 

Edited By Simon Chaddock on 25/08/2018 00:59:57

cymaz25/08/2018 07:02:35
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7994 forum posts
1053 photos

Slightly off thread Simon, isn’t that an old wooden ruler from Her Majesty’s Stationary Office?? My late father used to be in the civil services and all his office stationery was HMSO stamped

Simon Chaddock27/08/2018 19:49:26
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5249 forum posts
2738 photos

cymaz

Yes it is. twelfths (good for inches and feet scaling) and sixteenths (good for halves and quarters) on the front. Tenths and metric relegated to the back!

The Albatross is finally complete, apart from the reg numbers.

27aug18a complete

27aug18e complete

65.5 " (1660 mm) span. It weighs 25.4 oz (720 g) with a 1500 mAh 30C 3s.

With 350W (measured) it has 220W/lb available, not that I am likely to need all of it.

Do far it has only been moved!

Mike Etheridge 128/08/2018 13:44:49
1464 forum posts
403 photos

This picture has just appeared on Facebook, courtesy of Alan Beardmore

Image may contain: outdoor

Simon Chaddock28/08/2018 22:51:03
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5249 forum posts
2738 photos

G-AEVV I believe, the second prototype both of which were built as mail planes (which is what the the original spec called for) after it had been converted with the fins and rudders placed at the end of the tail plane to overcome lateral stability issues.

Odd think that a very advanced plane was funded by the Air Ministry just to carry mail around the Empire.wink 2

The 20 seat passenger version (5 built) had more windows with the passenger door further aft and it used Fowler flaps rather than the simple split flaps of the mail planes.

All seven were pressed into military transport duties when civilian flying ceased after the outbreak of WWII.

Stephen Jones28/08/2018 23:53:06
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2534 forum posts
1448 photos

Looks impressive Simon.

Loved watching your build log thumbs up

Steve

Mike Etheridge 129/08/2018 12:04:28
1464 forum posts
403 photos

Another of AB's photos. When I visited Croydon Airport in the early 1950's the Albatross was out of service by then-what a pity!

Image may contain: outdoor

J D 829/08/2018 13:03:13
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959 forum posts
59 photos

They were all lost during war service due to accidents,storm damage and lack of spares. The only surviving part is a Gypsy 12 engine at the DH museum.

Erfolg30/08/2018 11:25:33
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11124 forum posts
1086 photos

There is a good description and a good many photographs of the Albatross in a book I have "de Havilland the golden years 1919-1939", which is a collection of articles "Flight International".

The book claims that the requirement of the mailplane version was a range of 2,500 miles carrying 1000 ib against a 40mph headwind.

There is a quite a bit dedicated to the construction which seems very Mosquito like.

There is a passing similarity to the FW Condor IMO in general outline although constructionally they fundamentally differ.

Geoff Sleath30/08/2018 12:11:35
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3022 forum posts
247 photos

A stunning design/build project, Simon. I take my hat off to you! I hope we see it at the Ashbourne Scale day in October. I think it's the 14th with the 21st as a reserve.

Geoff

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