DH 91 Albatross

As I hinted to in the Cafe this could be quite a long build process.
First a 3 view.

An elegant design but with some features that could raise issues in a model.
The fins extend well below the tail plane so would be likely to strike the ground in an 'untidy' landing.
The elliptical wing might pose some stall issues unless some washout is included.
On the plus side
The single main wheel is a relatively big diameter although the one piece folding U/C door would be a bit of a challenge!
Scale ailerons are fairly generous as is the prop ground clearance.
The next big question is what size to make it?
By measurement from the 3 view the prop diameter to wingspan has a ratio 1:10.95
So a 6" prop will give a wing span of 65.7", a 7" prop 76.7", a 8" prop 87.6" etc
I had originally thought of using a 9x6, as it is a good match for a cheap 1200kV 150W out runner, but at 98.6" span the Albatross would be a good bit bigger than I would like.

"I think I had better think it out again!"

As stated before Q, you love a challenge, and we like to see your problem solving skills, looking forward to seeing the build

I can only echo Boz's post

Go for it!
Mike

After some cogitation I have decided to go for 6" props and a 66" span.
Rather small for a multi so everything will have to be really light but a 6" prop is quite a popular size in small racing drones and there are quad motor/prop/ESC deals on Ebay! As an added bonus you get CW and CCW props as well!
Although strictly not scale, the full size was all CW, on a small(ish) super light RC plane eliminating motor torque is no bad thing.
A bit of internet searching is called for.

one tenor wrote:

Quorneng wrote: As I hinted to in the Cafe this could be quite a long build process.
First a 3 view.

An elegant design but with some features that could raise issues in a model.
The fins extend well below the tail plane so would be likely to strike the ground in an 'untidy' landing.
The elliptical wing might pose some stall issues unless some washout is included.
On the plus side
The single main wheel is a relatively big diameter although the one piece folding U/C door would be a bit of a challenge!
Scale ailerons are fairly generous as is the prop ground clearance.
The next big question is what size to make it?
By measurement from the 3 view the prop diameter to wingspan has a ratio 1:10.95
So a 6" prop will give a wing span of 65.7", a 7" prop 76.7", a 8" prop 87.6" etc
I had originally thought of using a 9x6, as it is a good match for a cheap 1200kV 150W out runner, but at 98.6" span the Albatross would be a good bit bigger than I would like.
As I have posted elsewhere on the forum robotbirds are doing some good motors at very reasonable prices.

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www.robotbirds.co.uk/default/mt2213-935-...combo-cw-thread.html

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is the one I bought recently but there are loads more with loads more makes. Have a squizz for yourself. Just Google Robotbirds and go to motors... Nice Idea go for it.

"I think I had better think it out again!"

BTW this comes with a pair of opposing props O/T

The design of the DH 91 is credited to A E Hagg who rose to become Chief Designer from an Airco draughtsman in 1916. He also designed the DH 86 Express (A DH Rapide with 4 engines). He left DH in 1937 so had no direct influence on the design oft the Mosquito.
In 1943 he joined Airspeed as technical director and was responsible for the design of the Airspeed Ambassador which shared some 'family' resemblances to the DH 91.

Quorneng wrote: The design of the DH 91 is credited to A E Hagg who rose to become Chief Designer from an Airco draughtsman in 1916. He also designed the DH 86 Express (A DH Rapide with 4 engines). He left DH in 1937 so had no direct influence on the design oft the Mosquito.
In 1943 he joined Airspeed as technical director and was responsible for the design of the Airspeed Ambassador which shared some 'family' resemblances to the DH 91.

You're right I recall the ambassador from when I was a nipper Never seen a DH86 Express . Were many made.?Thanks for the info.O/T

The DH 86 went into series production. 62 were built being used by the RAF and as a civil airliner by UK and Australian airlines.
Fast and efficient however it did not have a particularly good safely record being difficult to handle in adverse conditions. After three fatal total loss crashes in Europe an A&AEE report concluded the plane had significant stability issues which were largely cured by adding additional fins to the tail plane. It appears these mods were never communicated to the Australian users where its poor safety record continued. None remain.
The Ambassafor (Elizabethan in BEA service) is forever remembered for the 1958 Munich air disaster which killed 23 including 8 members of the Manchester United football squad and 3 coaching staff. The publicity around the crash hastened the withdrawal of the type in favour of Viscounts.

The X2204 2000 kV racing drone motors arrived this morning.
First job is to workout the pitch of the mounting bolts and the size of the aperture for the wires.

Most of the DH Albatross nacelle is virtually circular so it seems logical to 3D print it. After a bit of experimentation it should be possible to do it as a single piece.

The 28 mm diam motor bell is a very close fit within the nacelle.

Bolted from the rear.

The bare nacelle weighs just under 6 g.
It will need a 30 mm spinner.

Looking good!
Mike

A quick question please Q.

The cowls you've made look really good, but for a competition scale model the finish would have to be a lot smoother. Can the 3D prints you've produced be sanded or turned to produce a smooth finish?

You've probably guessed that I have a vested interest in the answer...

you can wet sand the 3d print or i fill and sand mine if i need a smoother surface.
the finer the layers the smoother the print but the longer thee print time.

Tony B