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-   -   Bombardier Q400 (http://www.Wattflyer.com/forums/showthread.php?t=74353)

quorneng 08-23-2014 11:14 PM

Bombardier Q400
 
2 Attachment(s)
A scratch build twin.;)
Attachment 177039
I have seen these flying out of Liverpool Airport and at any altitude the wings look like pencils!
Attachment 177040
It seems like a good subject for a really lightweight design and with that tiny wing area it would have to be as a park flyer. :D

Apart from the challenge of building the long fuselage it has some features that would help the build.
The wing is mounted completely above the fuselage 'tube' so structurally easier to do.
The engine nacelles are huge so no problem fitting the ESC and flight battery in each side.
Although a 6 blade prop is really too difficult however even a 3 blade would be huge.

So a hand launch, belly land all Depron twin.
That's about as far as I have got. The real question is could I possibly finish it by 15th Sept?
We shall see

CHELLIE 08-24-2014 12:39 AM

Quote:

Originally Posted by quorneng (Post 955767)
A scratch build twin.;)
Attachment 177039
I have seen these flying out of Liverpool Airport and at any altitude the wings look like pencils!
Attachment 177040
It seems like a good subject for a really lightweight design and with that tiny wing area it would have to be as a park flyer. :D

Apart from the challenge of building the long fuselage it has some features that would help the build.
The wing is mounted completely above the fuselage 'tube' so structurally easier to do.
The engine nacelles are huge so no problem fitting the ESC and flight battery in each side.
Although a 6 blade prop is really too difficult however even a 3 blade would be huge.

So a hand launch, belly land all Depron twin.
That's about as far as I have got. The real question is could I possibly finish it by 15th Sept?
We shall see

With your building Skills, you should be able to have that plane built in less than 2 weeks :ws:

xmech2k 08-24-2014 01:21 AM

Should be awesome. Good luck! Can't wait to see it.(Amazing those little wings carry all that! )

quorneng 08-25-2014 11:58 AM

4 Attachment(s)
A little bit further.
On of the problem starting from a small 3 view is the lines get very blurred when printed out at the intended size.
Like this.
Attachment 177046
So after a few hours redrawing the small 3 view line by line on my computer but at a much larger scale the lines remain sharp even when printed out big.
This is a small size version of the file that can be downloaded.
Attachment 177047
The big file is 9600 pixels wide. The same bit now looks like this. :D
Attachment 177049
I have also done the side and front views.
Now I have to work out how on earth to actually make something this big in sheet Depron.
Attachment 177050
It is just over 6' 6" (2000mm) long. :eek:
Yes, my Concorde is a bit longer but that had a wing built along most of its fuselage length. This fuselage will be supported just in the middle. :concern:
Why this particular size?
It is set by the only 'handed' pair of 3 bladed props I could find. 9x5x3.

Find the props and build the plane to match! ;)

quorneng 08-27-2014 03:03 PM

3 Attachment(s)
At this stage any amount of thinking things out can save a lot of time in the long run.
For a really lightweight build the real problem is the fuselage (its by far the biggest bit!) rather than the wings. The lightest construction method is a stressed skin over closely spaced 'ring' formers much as is done in full size.
A 3mm Depron skin needs to be supported at least every 2" (50mm) which means there would be 23 identical formers in just the parallel portion of the fuselage. :concern:
I did consider making these 5.75" (150mm) diam formers complete in one piece but it would use up a huge amount of Depron.
I eventually chose to build the fuselage as a 'half shell' over the plan from top and bottom keels and to save Depron each former ring would be made up of quarters.
Attachment 177065
Two quarters joined to make the half circle formers being added to the keels. The keels are joined by thin 'jury' struts that will be removed once the other side is added
Attachment 177066
When all the formers are in place a start can be made with the planking.
Attachment 177067
I had not intended to use grey Depron but this portion of the fuselage is over 43" (1100mm) long so the planks have to be cut from the big 1250mm sheets that are only available in grey.

Having proposed this for the $100 twin contest there must be a real possibility that such a complex build will not be completed in time but I will keep plugging away just in case.

mclarkson 08-27-2014 10:33 PM

This should be a pretty amazing build. Best of luck with it!

quorneng 08-29-2014 11:35 AM

3 Attachment(s)
With the half shell almost fully planked it can be lifted from the plan.
Attachment 177088
A start on the other half of the formers.
Attachment 177089
It occurred to me that the fuselage would need local reinforcing under the wing mount to resist the weight of the wing in a belly landing so extra formers with full internal sheeting.
Attachment 177090
It is also where the plane will be held for launching.

At this stage the fuselage has little torsional rigidity so the planks will have to added alternate sides to avoid building in a twist or a banana!:concern:

quorneng 08-30-2014 04:02 PM

2 Attachment(s)
Completing the fuselage formers is a slow process.
This shows the sequence.
Attachment 177102
First the remaining half of the former ring is glued on and the jury strut removed.
Then the one piece inner flange is added to turn the former into an "I" beam. A tricky operation as it has to be cut to exactly the right length to ensure it makes contact all the way round the inside of the ring.
A flange is added to the lower keel to also turn that into an "I" beam.
Finally another jury strut is added to keep the former square.
Access limitations mean that each former has to be completed before work can start on the rest one and there are 23 to do!
Eventually it looks like this.
Attachment 177103
Now there just 17 more planks to add! ;)

And it definitely wont be complete by the 15th so it is no longer an competition entry.
I suppose I could submit my Hamilcar X. It was first built nearly 5 years ago but has only recently had its true maiden flight! (All the previous attempts were only seconds long and ended in a crash!)

quorneng 08-31-2014 07:06 PM

3 Attachment(s)
The last plank, or rather the space where it is has to fit!
Attachment 177122
always the most difficult as it has to fit both sides all along it length.
The engine nacelles are huge (16" long!) and would not look out of place as the fuselage of a small park flyer. :eek:
Attachment 177123
There should be masses of room to fit the motor, ESC and battery in each.
Attachment 177124
With the radio in the wing and the rudder & elevator servos in the T tail (their cables will run in the dorsal spine) it means the fuselage will have absolutely nothing in it! :D

riverrat 08-31-2014 11:21 PM

Nice!

quorneng 09-01-2014 11:32 AM

5 Attachment(s)
The nacelle has a substantial air intake and exhaust so the intention is to use it to cool the ESC.
Attachment 177143
The drum mount is fixed on to the bulkhead using self tapping screws. The particle board is locally 'hardened' with cyano.
Attachment 177144
The 1200kV Emax test mounted in the nacelle.
Attachment 177145
It looks rather 'lost' behind the huge spinner.
The nacelle and intake complete.
Attachment 177146
Technically the spinner is the wrong shape (too pointed) but it fairs in well with the nacelle. Quite a bit of fine sanding still to do.
The exhaust duct at the rear.
Attachment 177147
All the formers have large holes in them.
This is about as far as the nacelle can go until the wing is built.
Now I have just got to make another exactly the same!

quorneng 09-18-2014 10:58 AM

4 Attachment(s)
Thigs move on slowly.
The nose section under construction built the same way as a half shell over the plan.
Attachment 177417
Obviously the planking is very much more complicated that the constant section of the fuselage.
The half shell off the plan
Attachment 177418
The nose complete.
Attachment 177419
And added to the main part of the fuselage.
Attachment 177420
The engine nacelles are in about the correct position to give an idea of the overall size.
I had a small trick to get a smooth joint. The cockpit was actually built very slightly under the fuselage diameter. The cockpit skin was then slit several times for about 5cm. This allowed the skin to 'petal out' to exactly match the diameter of the fuselage. The slits were only 0.1mm wide so could easily be filled once the nose was glued on.

mclarkson 09-18-2014 09:34 PM

Impressive work, sir.

quorneng 09-21-2014 01:03 PM

1 Attachment(s)
As this is not in the twin build contest any more things have slowed down a bit coupled with a long period of very good flying weather!
With the rear part built the fuselage is now at its full length.
Attachment 177451
Near enough 6'6". Quite a bit of sanding and filling to do.
The planking has been left off the top at the rear to allow its enormous fin to be 'built in' to the fuselage.

quorneng 10-05-2014 06:59 PM

5 Attachment(s)
Having finished the cascade ducted Harrier work can start again on this.
Being a T tail the fin needs to be fairly stiff but on such a long fuselage it is also a long way back. Weight is critical so I decided to use a substantial 'full with the surface' balsa/Depron/balsa spar like this.
Attachment 177724
The fin spar will extend right through the fuselage.
Attachment 177725
Lifted from the plan the 3mm Depron skin can be added.
Attachment 177726
The missing section of skin is to allow the rudder servo to be added.
The fin installed on the fuselage.
Attachment 177727
The fin spar as actually inserted into the fuselage lower skin as shown by the red circle.
Attachment 177728
The tailplane is next.


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