Wings! What wings? The Bombardier Q400

So far I have only built one 'airliner' - Concorde - I have in mind to go a bit more conventional but still rely on Depron's light weight for a plane that might be difficult to do other wise. The Bombardier Q400

This design started life as the De Havilland Canada Dash 8 as a cheaper to run and faster flying development of their 4 engine STOL Dash 7.
Developemnt of the Dash 8 was rather forced on DHC as sales of the Dash 7 with its extreme STOL characteristics were disappointing.
As a result DHC was bought out by Boeing with the prospect of shared production for a large order of Boeing airliners for Air Canada. With allegations of bribery over the contract ultimately won by Airbus Boeing promptly sold DHC to Bombardier.
Nevertheless the Dash 8 'high speed' formula has proved popular with production of over 1000. Progressive fuselage stretches and ever more powerful engines have lead to the Q400 with a fuselage significantly longer than its span and a pair of 5000hp turbo props. As a result it is nearly 100mph (30%) faster than its nearest rival the ATR72.

My intention is to build a modest 'park flyer' that performs appropriately for its modest wing area rather than its overall size so it will need to be light, Depron light!

Scale 6 blade props would be a nightmare (although not quite impossible ), 2 blade would look wrong so it has to be 3. Even then the range is very limited so the final size of my Q400 may well be determined by the size of the props available!

Time for doing some sums!

Blimey Q, I take my hat off to you with this sort of project !!!!!!

Watching this one with great interest

Garry

So here are some tentative sums.
It had imagined using 8" props but cant find any. The nearest 3 blade I can find are 9x5 so if sized for those we get:-
Span 56"
Length 65"
Fuse diam 5.3"
With a wing area of just under 2 sqft.

The nearest twin I have to that is my Cessna O-2. It uses a pair of 2 blade 9x4.7 but it has no less than 2.7 sqft from its 53" wing.

Hmm!

Perhaps it would be better if it were just a little larger but kept to the same 9" diam props.
Make the length say 72"
Span would be 62"
Fuse diam 5.6"
Wing area 2.45 sqft.

With a similar power set up as I used in the Cessna and hopefully about the same total weight the wing loading would not be that much higher.

My intention would be to put a battery and ESC in each nacelle behind the motor. The scale turbo prop intake and exhaust provide a convenient 'front to back' cooling path.

On the Q400 the wing is mounted completely above the fuselage diameter so it should be relatively easy to make it 'bolt on removable' with only 2 connectors required for the rudder and elevator servos mounted in the fin. The fuselage itself would thus be completely empty.

It looks quite doable but my biggest concern at the moment would be the potential flexibility of a 6' long, 5.6" diameter 'tube' built in Depron.

Perhaps a bit of a 'test' fuselage to find out!

Quorneng wrote: It looks quite doable but my biggest concern at the moment would be the potential flexibility of a 6' long, 5.6" diameter 'tube' built in Depron.

Perhaps a bit of a 'test' fuselage to find out!

Could you not use a single thin carbon tube down the center of the fuselage to provide the rigidity? ... The weight would be very little & flex would be almost non existent. .... Rigidly joining 2 lengths of tube would be the heaviest part.
If you use a lot of thin Depron formers I think you'd end up with a very strong & rigid fuselage.

Pol.

Or failing that .... how about a cross section Depron "Girder" all the way down the lenght of the fuz? ... There shouldn't be much side to side flex in a 5 inch wide strip of Depron, & this is something you can check before any major construction.

Pol.

Pol
Thanks for the suggestions.
I am not sure a Depron girder would be any more rigid as the fuselage will already be a tubular girder. Such structure provided it has suitable skin support has the highest strength to weight ratio of any shape.

My 7' 6" long Depron Concorde fuselage is actually slightly narrower but of course sits on a long delta which adds stiffness. In addition a delta is not particularly susceptible to flex.
On the other hand the fuselage of the Q400 will be centre loaded by a narrow chord wing and a tailplane nearly 3 ft away.
I may be worrying unnecessarily as the unreinforced Depron tail booms on my Cessna Skymaster have an even higher aspect ratio than the Q400 rear fuselage and it seems to manage ok.

Whilst not a patch on Tony's "Depron overcast " it still comes out quite big.

65.5" span and 76" long.
I shall have to think rather carefully about how to build that very spindly wing!

No building yet just redrawing the 3 view.
Blowing it up to the correct size means all the lines get very 'fuzzy' so each line is redrawn suitably thin with all the unwanted fuzz erased. It is not a particularly quick job.
This is a small file version suitable for posting. The original is huge - over 9000 pixels wide.



One major advantage of doing this is where the left and right are symmetrical 'cut, flip and paste' can be used to ensure both sides are a true mirror image.

The next task is to work out how best to actually make the fuselage.
For the parallel section I would like to 'roll' the skin in one piece with the joint along the top as the wing fairing and the dorsal spine will hide most of it.

Something like this?

If you look at Flight Radar there are a few Q400s in the air at any one time.

How do you plan to transport that ? Obviously not in one piece so making it in say fus/tail in one piece then wing/engines in one or two sections means assembling with sufficient rigidity whilst keeping the weight down may be a worry.

make the front half of the fuselage split at a convenient point and use ali tubes for location and support.

seems to work for me.

It will be in two pieces. The complete fuselage along with the tail and a one piece wing.
The wing sit entirely above the fuselage so its mount does not compromise the 'tube' strength.
A wing in one piece gives the maximum strength for minimum weight and with the flight batteries in each engine nacelle there will only be the rudder and elevator servo electrical connections required when the wing is bolted on.
As the fuselage will not be carrying any significant weight the wing attachment will not need to be particularly massive.

At this stage my best guess is about 30oz (850g)
The wing area will be 2.25 sqft giving a wing loading of 13.3 oz/sqft. Apparently the best measure is the Wing Cube Loading which takes size into account. For my Q400 it comes to 8.8 which puts it between 'trainer' and 'sports aerobatic', nether of which I expect it to be!