Project Dornier Do-17z2

[aleatorylamp]

Hello folks!
Well, after an inactive Christmas spell of overeating and generally doing as little as possible, I´ve decided to make a nice Dornier Do-17, which will hopefully be nicer than the stock AI version! Smilo also wants a nicer one, so all the more reason to do it!
Early Do-17 versions had 1000 Hp Bramo Fafnir 323 engines with single-speed superchargers, which gave only 900 Hp at S.L., but the Do-17z2 had the superior Bramo Fafnir 323P, with a 2-speed supercharger, making the full 1000 Hp were available at S.L.

Performance specifications of the real Dornier Do-17z2: (Note: Speed and power together are only given for S.L.)
> Sea level: 1000 Hp and 217 mph.
> 10200 ft: 1000 Hp.
> 13200 ft: 940 Hp.
> 16400 ft: 255 mph.

Work on the stock AI Do-17z2 Air file, which had far too much power and speed all round, so a lot of adjusting had to be done:
a) corrected cylinder displacement and RPM values
b) tweaked torque and friction graphs
c) considerably reduced Boost Gain value
d) adjusted drag values

Model Performance: (Maybe Ivan can give his always very much valued opinion here!)
> Sea level: 1003 Hp and 221 mph. (slightly fast)
> 10200 ft: 1071 Hp and 250 mph.
> 13200 ft: 940 Hp and 246 mph.
> 16400 ft: 813 Hp abd 244 mph. (a bit slow)

Generally seen, this performance looks quite acceptable, but I wonder what Ivan´s opinion would be! Only if you have time, Ivan, and are not too busy to answer or stressed out, of course!

Cheers and a Happy 2017 to all!
Aleatorylamp

[aleatorylamp]

Hello again!
Looking further into the engine parameters on the AI Do-17 .air file, I noticed Max. Manifold Pressure very high at 60.445, and also Critical altitude at 22400 ft. This would more likely fit a late WW2 supercharger!

Looking into other early WW2 models , it would be more realistic around perhaps 42 for Max MP and 17000 ft for critical altitude, and as I can´t find the values for the Bramo Fafnir Superchargers anywhere, this educated guess is for the moment the only solution. Of course, changing Max MP and CA requires changing some other parameters, but that will be no problem.

The first trials in this sense seem to provide similar engine and aircraft performance results as the first tests, but we shall see!

Cheers,
Aleatorylamp

[aleatorylamp]

Hello folks!
Further research from a German page on the Bramo Fafnir engine has revealed a few more exact details:
The improved 940 Hp at altitude of the 323P engine were achieved at 15000 ft, and not at 13200 as I´d mentioned before. Also, Critical Altitude is confirmed at 10200 ft, upto where full 1000 horsepower could be maintained.

Trials with Maximum MP at 44 Hg and Boost Gain at 2.286, gave the following performance:
>Sea level:228.0 mph, 1003 Hp, 44.0 Hg (virtually correct power, but 14 mph fast, needed to maintain altitude performance)
>10200 ft: 259.3 mph, 1095 Hp, 44.0 Hg (inevitable Critical Altitude peak here: +95 Hp power and at least +4.3 mph)
>15000 ft: 247.0 mph, 940 Hp, 37.6 Hg (exactly as per specified power)
>16400 ft: 255.7 mph, 887 Hp, 35.6 Hg (exactly as per specified speed)

Ceiling is stated at 27000 ft. Here power goes way down to 513 Hp, and the aircraft just about maintains RoC at 100 fpm.

So, I´d say these more realistic Max. Manifold Pressure, Critical Altitude and Boost Gain settings now give somewhat better results. Any ideas and suggestions would of course, as always, be very welcome!

Now the building starts. As soon as I have a nice Kindergarten colourful cardboard model ready, done in 2D templates, I´ll post it together with the .air file, so that anyone who´s interested can try it out.

Cheers,
Aleatorylamp

[aleatorylamp]

Hello again!
As usual in these cases, interesting additional details crop up on more-difficult-to-find sites . I´ve just found three that state Vmax for the Do-17z2 with the 323P as being 163 and/or 165 mph because of the superior supercharger, which is 8-10 mph faster than the previous sites, but without an altitude reference.

Now, what has to be decided, is what information is more reliable ! Perhaps this piece of information fits in nicely to account for the Critical Altitude peak, which at the moment is around 160 mph, so only slight re-adjustment will be needed .

Update: Closer inspection of the power curve reveals that the current FD peak is in reality a little higher than I thought, at 10800 ft, with 1104 Hp giving 263.5 mph.
A slight increase in Boost Gain from 2.286 to 2.33 only moves the peak upwards to 11600 ft with 1104 Hp giving 265.2 mph, but leaves performance at 10200 ft the same as before, so I shall leave Boost Gain as it was, at 2.286 .

Ivan, I know you were working on a Do-17z2 experiment as well, and I´m curious as regards the performance specifications you were striving for, if you have time and were to be willing to share the info!

Cheers,
Aleatorylamp ....................... P.S.: Merry 3 Kings´Day!! Even more presents!!

[aleatorylamp]

Hello Smilo,
There´s certainly a chice as to colour schemes!
I´ve been busy with the nacelles, flaps and ther retractable rear nacelle parts, and it hasn´t been too easy. The flaps still cause bleeds, but it seems to work. Here are some shots.
For the moment, I´ll finish the tailplane now.
Cheers,
Aleatorylamp

[smilo]

yes, you have been busy.
she looks very good, Stephan.

four days from my comment
on the speed which you build.
to be honest,
i was beginning to worry.
i thought, maybe, the nacelles
had sent you running away,
screaming off a cliff.
or, you had taken a much deserved vacation.

anyway, it's nice to see the progress.
how is the resource count?

[aleatorylamp]

Hello NoDice,
I´m afraid it has nothing to do with my settings.
Logged in, my text is black on white, and unlogged-in, it´s white on dark-grey.
Cheers,
Aleatorylamp

[smilo]

hello Stephan and Dave.
i just went back to earlier posts
and looked at them both in
CombatFs/CFC and SOH page styles.
for some reason, Stephan, in CombatFS/CFC,
your earlier posts are dark gray on gray
and are very hard to read,
but, now they are white on gray.
oddly, one of mine and a few of yours are a combination.
i have no idea why this is happening.
i always use SOH Default,
so, i didn't even notice.

maybe, one of the senior admins upstairs
has an answer and solution.

hmmm, i just noticed
the Reply With Quote button
isn't working either.
oh well, so it goes

[aleatorylamp]

Hello All!
I´ve started with the basic layout of the model, and haven´t really done a 2D cardboard model by any means - the only 2d things are the wings and tail, and, I´m running into complications with the fuselage: It´s not at all the usual rounded square or circular cross-sections job with wing-root skirtings! The only straight forward things are forward engine nacelles, wing, and tail empenage!

The main body of the plane looks like a much more modern design, quite ahead of its time. Cross sections are very unorthodox, especially at the wing root, all a smooth flow of gentle curves and slanted sides with very rounded edges. I now remember Ivan had mentioned this rather complicated aspect, which will take some thought as regards the best way to approach the matter.

At first I was thinking "Piece of cake! Structures for the fuselage except for glass areas: Keystone bulkhead for lower fuselage and dome bulkhead for the upper part!" But no way! It´s mostly going to have to be special components, except perhaps for the rear fuselage, which may be able to handle these structures.
Anyway, we shall see!
Cheers!
Aleatorylamp

[Rami]

Stephan,

Do these screenshots help as far as the shape is concerned?

[Ivan]

Hello Aleatorylamp, Rami,

Sorry I haven't had a chance to respond to many threads lately.
I / we have ad lots of things going on for the last few weeks and it is likely to continue for about another month or so.... Hopefully with good outcomes for all involved.

Regarding the AIR file for the Dornier 17Z-2, I never actually built one for my model.
I knew the model was going to be the difficult area and just used a converted Mitchell C AIR file for testing / viewing purposes.

As for the model, Aleatorylamp, you are finally starting to understand why this is a difficult subject to do well. EVERYTHING on this bird is a complex curve except for the Tail, Engine Cowls and Wing Tips.

The part that got me stuck was the rear of the Nacelles / Flap interaction.
I CAN handle it via SCASM, but it is still pretty complicated.

Another very difficult area is where the Canopy Glass and Framing interact with the Wing Root extensions. It IS possible to do without bleeds but is very resource expensive and takes this project (for me) way past what I can do without SCASM.

You will certainly find out more as the project progresses.

Rami,
Your model looks quite nice but does have some simplifications over the real aeroplane. There are plenty of videos of this bird still available which give a better idea of its shape. It is a very hard one to capture correctly and 2D drawings only give the basic outline.

Take Care.
- Ivan.

P.S. I will post some screenshots to show where I reached if I have the time to get into my development machine and it stays running long enough.

[aleatorylamp]

Hello Smilo,
Thanks for your support!
Ha ha! You are actually quite right about my problems with nacelles. I always find matching their upper and lower parts to the inner and outer wing sections extremely difficult.
Also, the tailplane being a shoulder wing, is not as straight forward as I´d thought - it has to match a small fuselage bulge there, but it´s coming along OK!
Parts count at 108% (864 out of 1200) is no problem, so I think I´ll have enough left for at least 3 or 4 crew and guns, although some of these planes had 6 guns (but only 4 crew).
Cheers,
Aleatorylamp

[Ivan]

Hello Aleatorylamp, Smilo,

Smilo is right, your speed in building is amazing.
With your project going and the recent revelation about the Dornier 215, I have been looking at LOTS of photographs of the Do 215B-4 and the Do 17Z-2.
Even though I am not working on my model, I can say that I would not even be done browsing pictures and you already have most of your aeroplane built.
....and that is after having done the photographic and drawing review once before!

I actually have been trying to work out a sequence for the rear of the Nacelle and the Flap interaction that can be done all within AF99, but it is very resource expensive. It would not be a problem with my model because the final assembly has to be done in SCASM, but it probably would not work on your version.

Regarding the Tail Cone et al., it seems like one of the more straightforward areas of the entire aeroplane, especially if you are not trying to animate the control surfaces. I haven't figured out a nice way of animating the Elevators without some bleeds, but the Rudders look pretty simple.

Regarding the armament: Although the gun count is pretty high at 6-7 in all, the arrangement is not terribly effective. I am not entirely sure yet now to best model that effect in a CFS DP file.

I have been doing some poking around at yet another potential project. (It is pretty easy to browse almost anywhere with a decent cell phone and lots of data available.) Would anyone be interested in yet another "Design Study" thread?

Take Care Guys.
- Ivan.

P.S. I do notice a minor issue with your model: The Dornier 17 had Split Flaps, not Plain Flaps.

[aleatorylamp]

Hello Ivan,
I got the fin notches back in at a minor 4 parts per fin cost, and parts count is now at 149.4%.
Here are some pics, and it looks more correct. I can´t make the notches more exact for lack of parts.
It´s good you pointed it out as I´d completely forgotten that I´d simplified that quite at the beginning.
Cheers,
Aleatorylamp

[aleatorylamp]

Hello Smilo,
OK, thanks, but not to worry! At least you have the latest version again - no harm done!

I now have an idea for the canopy glue sequence - at the moment the forward crew members seem to be more or less OK under the canopy. I studied Ivan´s sequence for the AT-9 Jeep and it´s a little different: It has 2 pilots and 2 seat-backs, but I think I can deduce the principle. It seems to follow a path, so that at the end all the parts involved end up under the canopy, so I´m trying to get there now! At the moment the rear cabin floor, gunner and gun are glue-sequenced, but do not end up under the canopy...

I´ll also inspect some vertices to see if I can get rid of some more strings of pearls.
I appreciate your efforts helping me out! It just proves that four eyes see more than two!
Cheers,
Aleatorylamp

[smilo]

i'm pleased to be able to help.
as is well known, this is an aircraft
i've wanted to see for many years.
i'd all but given up hope of ever seeing it.
as a matter of fact, i had given up.

i'm flying it right now on another machine
and noticed something rather funny.
in spot view, zoomed in on the canopy and crew,
from the forward left view,
i pressed the key for head on view.
as the view slowly panned,
the pilot and bombardier facial expressions
change as it approaches and passes center.
i don't know if it's intentional or not,
but, it's hilarious....please, don't change it.

[aleatorylamp]

Hello Smilo,
Well, the Iron Cross was on the tails of German WW1 aircraft and is the Luftwaffe symbol now, so there are lots around!
The problem with the black X is that it doesn´t exist, so it´s a reason not to put it on.
Anyway, I´ll see what I decide. Perhaps if anything, the best option is nothing, as you suggested before!!

Don´t worry about the testing while flying.
At any rate, your opinions have given fruitful results. Thanks!
Cheers,
Aleatorylamp

[aleatorylamp]

Hello Rami,
Thanks for the screenshots! The shapes shown look reasonable. I found some diagrams containing a sequence of 7 very difficult looking fuselage cross section details. The screenshots certainly show possibile shape solutions.

Hello Ivan,
Thanks for your post, and I hope you are getting good results from all that you have to do!
Your comments on the difficulties involved with the shapes are quite to the point!
I was just thinking about the rear upper cabin area with the shoulderwing. It´s completely flat there!

The extreme rear of the engine nacelles you mention had a small section that tucked in to make room for the flap deflection! Complicated indeed! ... and I´m not progressing. Also dire, are the wing-root leading and trailing edges, as well as the upwards and downwards bulging cabin!

Difficult, isn´t it! Not a piece of cake by any means. Now I know why there isn´t a better Do-17 other than the AI one!! Ha ha.
So far, the only sense of achievement that I got is from the performance adjustments in the .air file. I wonder...

Well, I´ll continue experimenting a bit and see if there´s a possible, plausible and elegant looking way around all this shape complication! I´ll try my hand at shaping the wing root into the aft-cabin fuselage component. A kind of mono-coque section is out of the question because of the under-wing concavity, so it will need at least 3 components there. Let´s see how it goes...

Cheers,
Aleatorylamp

[aleatorylamp]

Hello Ivan,
The tail empenage went OK despite my misgivings about the fuselage bulge there - I had to eliminate it anyway for parts-count reasons. Otherwise the crew and the weapons would fall short.

At the moment after some simple landing-gear struts, I´ve also put in a pilot and 3 machineguns. Now parts-count obviously rocketed up to 143.3%. In order to get in 6 or 7 machineguns, and have enough for some more crew members, I´ll have to take out a bulkhead from the machine-guns to simplify them - although then they will look like rifles...

Thanks about the split flaps - I had trouble trying to figure out what type they were. OK then. That has just saves some parts: Without the cut-out wing and the extra upper-flap surfaces it amounts to 10% parts!

Cheers,
Aleatorylamp

[aleatorylamp]

Hello!
I used a shoulder component for the fuselage around the rear cabin, hollowing out for the wing-root, and it seems to work.
(As yet, inner wings are 2D, and the fuselage belly is still trapezoid - will be more rounded though).

Here are some screenshots. Of course, a different matter will be once the cabinglass parts are placed, but that is for another day.

Cheers,
Aleatorylamp

[smilo]

it looks to be coming along nicely.
am looking forward to seeing more.

[aleatorylamp]

Hello Ivan,
I was going to answer before: You were asking > Would anyone be interested in yet another "Design Study" thread? <
I´d say "Yes indeed!", if you were up to it!

...and here are another 2 shots of the Do17-z2.

Smilo:
I think I´ll have to ask you to start deleting attached images from my few first models from 2 years ago, as I think my attachment-quota is slowly filling up. Unless of course there is a way I can do it myself without bothering you!

Cheers,
Aleatorylamp

[smilo]

there's an attachment-quota?
that's news to me.
i'll look into it.

[aleatorylamp]

Hello Ivan,
I hope your computer adventure takes you to a happy ending, and that the chain of coincidences that caused the problem will be followed by another with more positive results!

You will see that it is actually quite simple to set up VMWare. After deciding on the size of the virtual hard disk and the RAM allocated - I did 10 Gb HDD and 1 Gb RAM - you format the virtual HDD and install Windows XP from its CD. The CD was why I got a laptop with a DVD reader/writer (there was a faster one with 2.0-3.3 Ghz speed for 75 Euros more, but no DVD reader/writer). I understand there´s also a way of setting up from a USB stick with Windows XP CD image, but I didn´t bother.

Anyway, the Dornier:
I´ll go with your proposal for the 4 guns in the Dp files. The chin gun would probably be the fixed forward one with longer range?

On the real aeroplane, with 6 or 7 guns like on a gunship, they should have had at least 3 more gunners, but they just had them jumping around. Not effective at all, as you say!

Then, you are completely right about the limited choices of bulkheads for structures - a lot of them are useless anyway, and stupidly, a couple of more obviously useful ones like a) a keystone with a rounded top, or b) a trapeze or c) a flat-based pentagon have stupidly been omited, but anyway...

About the crew: Without one, you wouldn´t really need transparent windows, so those could be just grey-graded shading, saving lots of trouble and resources... Or possibly you mean leave just the pilot, and imagine the rest of the crew are bent down or something... The resources I used up with the extra crew members could perhaps come in quite handy for a couple of other things... Although these will not free any components - they are all structures.

For the moment, the result is quite satisfactory, but I am open to any additional ideas you may have.
I know your version of the aeroplane is going to rely on SCASM, but you know that will not be so in my case.

Great fun anyway!
Cheers, and thanks for your input.
Aleatorylamp

[aleatorylamp]

Hello folks,
The split flaps now work almost fine - when lowered completely the glue gluing them to the rear nacelle fails.
Then, there are now 3 crew and then also 2 nose guns, the upper of which is for the bomb aimer who sits next to the pilot, a dorsal one whose gunner is just a head, and a ventral gun in the belly canopy, and you can´t see the gunner.
Landing-gear struts don´t bleed, and with a parts count of now 148%, I think I just about have enough parts for the 3 wheel doors and wells, (the rear wheel was also retractable) and the thick antenna on the cabin.
Let´s see...

Update:
Now I´ve got everything in that I want, antenna included, and parts count is at a squeezed 149.9%!!
I had to duplicate the outer wheel-doors because of bleeds, and although it´s not perfect, it´s better.
Ivan: I wonder if it´s time to post the model incl. AFX (there are no main textures as yet) for you perusal, (of course, if you would be so good)?

Cheers,
Aleatorylamp