Analysing and modifying the AFX file with QBasic.

[Ivan]

Hello Aleatorylamp,

Regarding Cats and modern medicine, there are more nuances than we are going to properly cover here. Let's leave it at that.

Somehow, the more or less fine-working propeller and nose-gear animations don´t get on with each other. There is a nasty case of Glue-Cure Immunity between Gear-Nose and Nose groupings, and there isn´t a Nose/Gear-Nose Glue Template.

If you look at the SCASM code, you will see how things really work. I believe you will be shocked and disappointed.

The solution may require everything to exist within the Nose Group. The body cringes at the thought. For a start, I´ll have to get the forward "slice" out of the Nose component again, to free the glued dashboard from the nose area. Let´s see what I can manage with this idea.

This is where I was heading but it is so much work that I am choosing not to do it on the EJ model first. The separations aren't really designed well for the purpose, so with this in mind, perhaps I can make better decisions. This is one of the benefits from working on the "throwaway" model: You get to see the potential problems early.

After that, I may even leave the Instrument Console and the Tool-Box behind the pilot for the imagination!

I believe that is supposed to be a Radio behind the Pilot.

....Now, Back to Flight Model edits!
;-)

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Oh Dear! The radio. Ha ha... A tool box would be too dangerous there. What would happen during an emergency stop for an old lady crossing on the zebra stripes, even if it didn´t open in the process?
Well... probably nothing - there was armoured glass behind the pilot´s head.

I just had a look at the SCASM code, but I need a more time to identify different the parts involved to see what you mean. I´m curious to discover what you said.

Update: I was too optimistic, I´m afraid. Even my cats would be better at this than me.
After identifying SCASM nose-gear and propeller animations, I´m no cleverer than before about what´s going on in the under-nose area. Obviously the gear-doors/well and upper gearstrut interfere with one (lower) propeller blade (and possibly with the entire nose, for an instant), and not so much with the whole propeller animation, but I don´t think I can pin-point why, other than the short distance between the conflicting elements.

Different solutions that occur to me are by no means clear. I´ve never put a nose-gear with doors and well into the nose group, and I don´t know what could happen. You have more experience and insight here, and can identify things much sooner, so evidently this is not going to be an easy fix.

Anyway, it´s only one propeller-blade with the stopped engine, so it´s not too annoying if it stays.

Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

I don't know if the Radio was actually there and shaped like that in the particular version of the Airacobra that I was building but I do recall that it was a pretty common fixture there. Size and shape varied a bit.

The Propeller to Nose Gear bleed is actually worse than you might think.
Try bringing the aeroplane in with Landing Gear down as you would for landing.

Last night I was not feeling particularly ambitious, so I decided to work on the Cannon and Propeller Spinner.
The new colour is so that the changes are visible. While I was repainting the Spinner, I decided to make another little minor change in the paint job. I don't think anyone really knows for sure what "Nanette" really looked like, but for now, she is masquerading as a P-39Q-1. Soon she might change to a P-39D.
There is a LOT of wasted space in these texture files, but I am not planning on correcting that part.... yet.
With the Spinner and Cannon changes, the Overall Length is about where it should be though I can't say much about the proportions.
The CoG of the model is still located incorrectly but I don't want to change it because I would lose all of the animation that I have already done.

The Pilot also needs to be finished because I want to use it elsewhere.

The Flight Model did not get any changes last night, but the DP file did.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Nanette is a very pretty girl! A very clean and nice-looking cockpit interior too!
This sort of thing adds a lot to the model! The 37 mm cannon up front is also very business-like!

Regarding approach for landing and looking at the front, there´s a moment where the wheel-well makes the gear doors disappear, but it´s very momentary. Then, what´s more visible, or rather invisibvle, is the disappearance of the inboard wing-root cooler intake. Apart from this, I haven´t noticed anything else.

I think I´ll take advantage of your experience and save myself the trouble of trying to fight the propeller-blade Bleed.

Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

Try timing the screenshot so that the Propeller Blur is in line with the Nose Gear.
This problem will show up all the time because of the way that AF99 handles Groups.
The issue with visual priorities of Groups is what I wanted you to find in the SCASM code.
You don't need to really look for the individual pieces such as Propeller Blades and Nose Gear; just look for the Group that they are in.
The code is in one massive block at the beginning just after "Main Start".

Many years ago, I thought I would rewrite that section of the code to make the VectorJump's more reasonable.
The idea SORT of worked, but was so tedious that I decided not to pursue it.
Creative use of Glue and Templates gave such similar results with so much less effort that this is what I use now.
There IS a difference, but you have to look very hard to find it.

I believe the issue with Intakes is because of reliance on "Automatic Glue".
Sometimes it is necessary but avoid it if you can.
I am not going there yet because there are bigger bleed problems with the same Parts from the side.

The Cockpit on my version needs a lot more work. Not much is textured at this point
If you really wanted to, you could go crazy with detailing things like the Radio and Instrument Panel.
I still have a couple bleeds from the underside that have not yet been addressed.

Have you revised the Flaps on your version? They look pretty good. I still need to work on mine.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Hmmm... I still can´t see anything in the SCASM code - it´s too abstract for me, I´m afraid.

I timed the prop blur screenshot though - it can easily be stopped with the right mouse button. Howeverm, seen from the front I didn´t notice anything except some bleed-overs in the wheel-fork component because it´s so strangely built - I still haven´t changed that.

Then, my flaps are OK seen from the front, from the side and squared from the rear only! - not so much from other rear angles, when there´s a very messy moment also involving wheel-wells and front wheel-doors.

Not very motivating... but at least it´s only momentary... Here´s some pics.

I finished the new cabin component and put the two halves into the glue sequence just before the C-Frame halves, although it´s not perfect bleedwise either, but it seems acceptable.

Then, the inner cooler intake at the wing root: You´re right - it´s in with Automatic Glue - i.e. it´s the only thing in Inner Wing Mid L/R. But, glued to the wingroot inside the already cluttered Body-Main Glue sequence may be problematic. ...Or not... maybe it COULD work...

Ups and downs, merry-go-rounds,
Cheers,
Aleatorylamp

 

[aleatorylamp]

Serious improvement under the nose!

Hello Ivan,
Thinking a bit further about the Lower-Nose Propblade/Gearwell and Geardoor interaction,
the problem is the Gear-Nose Group, which is also the cause for the messy view of the
forward geardoors seen throught the fuselage from behind.

Gear-Nose should really only contain the nosewheel and nosegear-strut, and if possible,
only the lower part of the latter.

The glue-strategy is similar to the mid-fuselage components, where horizontal splitting
of the component allowed A) wing fairings to be glued to the lower component,
and B) exhausts to be glued to the upper component.

So: Still in Body-Main:
The nose component, preferably including the slice cut off from the mid-fuselage because
of the long nose-gear doors, is split horizontally into top and bottom components.

The top component continues to have the dashboard (and maybe the instrument console?)
glued to it, and the bottom component has A) the insignia-down wheel-well glued to it first,
followed by B) the lL/R glue-sequence for the L/R wheel-doors.

Now the propeller blade only interacts with the gear strut, not with wheelwell and wheeldoors.

This actually works!

Next step:
Cut the Wheel strut into upper and lower sections, keep the lower section in Gear-Nose and
try to include the top part in the aforementioned new sequence.
Now I´ll see if this can be.

Cheers,
Aleatorylamp

 

[aleatorylamp]

A bit better still

Hello Ivan,
It seems to have got a bit better still!

Moving the long nosegear-strut into Body Main as well, glued just under the wheel-well and putting the strut into the L/R Glue Sequence for the L/R wheel-doors provided a further improvement.

Only the wheel and its yoke is left in Gear Nose, and now only the tip of the propeller blade interferes there. Let´s see if I can get the top of the wheelyoke out of there as well!

This way all that will be left of the nose-gear strut in Gear Nose are the wheel-yoke sides, and they will expectedly display better as well, without filling in the triangles as happens now.
Cheers,
Aleatorylamp

 

[aleatorylamp]

Nothing is perfect

Hello once more!
Instead of editing a post, I´m adding... but probably adding is better.

I reduced the height of the lower nose-component by one row of parts, as I was getting nosedoor bleeds through the nose-component side seen from above-rear-sideways. Now the lower component is only the two lowest panel rows. All the others are in the upper or main nose component.

I also fixed the yoke on the nose gear a bit better, but the Nosegear Strut placing into the Glue-Sequence could probably be improved - now there´s interaction between the inside of the wheel-door and the outside of the Nose Component bottom.

Additionally, there´s interaction between the main wheel-wells and the Nosegear Strut and door.

Uffff... If it´s not one thing in one place, it´s another in another.

Update: Now I did update - but it seems pointless to add another post just for this.
I can´t get it any better, at least for the moment, be it by ordering parts differently, or by moving around nosegear-glue. There´s just too many elements, and some angles simply don´t give a clean display, although many others do. Nevertheless, all in all, it seems a bit better than yesterday.

Cheers,
Aleatorylamp

 

[Ivan]

Nanette

Hello Aleatorylamp,

Nanette had a lot more attention last night and this morning.

I never did like the nose contours, so I revised them a bit.
I still don't think the shape is ideal, but it is a lot better than when I started.
I got tired of trying to figure out the naming convention for the Parts, so I used the originals as templates to create my own set of Parts with new names that help me find things more easily.
The rebuilt Nose is shown in the first screenshot.

There is going to be a lot more work done in this area for the Nose Gear.
I believe I have a solution, but I need to try it out first.

Regarding the Exhaust bleeds:
I believe I was able to address that in a reasonable manner.
The first couple tries did not work but this was around 2 AM and I was making stupid mistakes.
By the time I went to sleep, it still was pretty broken even though I was pretty sure there was nothing wrong with my idea.
As it turned out, there really WASN'T anything wrong with my idea.
The big problem that I found this morning is that the Exhausts are each shifted by a slight amount.
Once I removed that shift, everything worked as I thought it should.
The idea is to duplicate each Exhaust in the Inner Wing and also in Body Main.
Attached is a screenshot showing the results.

I figure if it shows up without problems in this area, it should not have problems elsewhere but I haven't checked out all the angles yet.
I also found that the current pieces really don't fit together well without Wing Root bleeds from some angle unless the Fuselage and Wing Fillets are "integrated" better than they are here.

This project has gotten way past where I had intended when I started but perhaps there are another couple experiments to try.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
There is always more than just one road that leads to Rome.
Looks like we are getting somewhere! Very good. It´s interesting that you are going further than you had originally intended.

Your model is certainly looking very interesting, especially the cockpit.

Once your idea yields the expected results, of course I´d be interested to to see how you solved the two main problems on this model: A) The Wingroot and Exhaust, and B), the Nose-Gear / Propeller.

I also noticed the irritating shift on the exhaust, as well as the inconsistent left-to-right switching on some of the other elements like geardoors and geardoorglue.

But for a few short moments of different inteactions between elements from different angles, these are not too bad, and the improvements I´ve arrived at are all-round very acceptable.

The model looks good and behaves well in the air. I´ve adjusted the mid-fuselage texture a bit more, but the markings still need a bit of attention.

Cheers
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

Getting somewhere or avoiding getting somewhere?
Keep in mind that time spent on this project is time NOT spent on my new version of the Airacobra.
The techniques are transferable to some extent which is why I keep working on it.
The flight model is near 100% transferable.
Refining the model in other ways is really a waste of time though it is hard to resist because the broken stuff is so obvious and the fixes are so easy in general. They problem is that EVERYTHING is bent or broken to one extent or another.

Regarding the issues you pointed out:

A) I believe the Wing Root to Exhaust issue has been addressed. I just have not checked all the angles yet and if it turns out that there is a problem (which I do not expect), I do have a more elaborate solution.

B) The Nose Gear to Propeller issue does not look to be terribly difficult. It just looks to be a bit tedious to rebuild all the pieces that need to be changed. I am doing my best to NOT change the shapes even if I don't think they are optimal.
This is also why I had to adjust the Nose first. It would not have made sense to adjust the pieces around the Nose and then adjust the Nose and have to do it all over again.

C) The Trailing Edge of the Wing Fillet to Outer Wing isn't quite right. It wasn't matched up when I started but since I was there to work on Flaps, I probably should fix that area as well.

D) The Pilot needs more work for shape and textures.

E) The Instrument Panel and Console are shaped incorrectly and also need to be textured.

F) The Flaps need a bit of testing to see if an idea that I have will work. I don't need it on this model but it might look good on another model.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
OK, I wasn´t quite clear about the exhausts, and thought there was something additional to duplicating them in Inner Wing and also in Body Main. Interesting!

I also had trouble with the wing-fillet trailing edge matching points. It was difficult to see the reason for the mismatch, and it didn´t make much sense. After rounding off the fuselage, it became clear what had to be done with this part, so that was OK.

At the moment I´m filling in cracks and adjusting textures a bit better, and basically, as far as I´m concerned, I´d be just about done with this model, similarly to your case, but for different reasons.

It will be very interesting to see how your new build starts developing once the preliminary phases are complied with.

P.S. It will of course also be interesting to see the results of your current tests on the different areas of the model you have mentioned as far as shapes and building techniques are concerned, but don´t let this hamper the progress required for your own version.

Cheers,
Aleatorylamp

 

[Ivan]

Pull on One String....

Hello Aleatorylamp,

I was trying to address a bleed last night and managed to cause this situation as shown in the screenshot.
It looks to me like I may have to do some extensive rebuilding in the aft Wing Fillet area.
It is like seeing a loose string and when you pull on it, the whole mess falls apart.
Every time I fix one area, something else breaks.

The Pilot textures were improved a bit but still need work. The shape of the Pilot's Head was improved as well.
I didn't get quite as far as I wanted on the Nose Gear / Propeller issue.

Yesterday, I decided that it might be a good idea to have a real 3D reference for a P-39 Airacobra, so I found a model that I had bought many years ago. It is a Monogram 1:48 Airacobra and looks to be a P-39D-1. It isn't assembled, but the single piece that is the underside of the Wing shows what the Fillet and Trailing Edge should look like.
It is a very old kit, so it was made back when the moulds were newer and is probably better detailed than the modern pressings.
I bought it at one of the IPMS events for $4 or maybe less. The price tag shows $4 but it may have come as a part of a deal with other kits or sold at the end of the show when prices tend to get lower.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Do you remember a scene in an old futuristic film, when someone gets their hands on
some REAL steak to grill, as opposed to the soy-substitute distributed by the state?

Your plastic P-39D model is like that - something to drool over and say "Wow! Lemme see!".
Now THAT is an empiric reference to go by! If you were going to build it, I could only say:
Send a photo when you finish, even if unpainted! (I never painted my plastic models).

... but I´m sure you won´t have the time. And, there´s a ton of photos of plastic models on
the Internet anyway... I just got carried away!

Anyway, it looks like you are making good headway with the problems I´ve been dealing with
lately. If I were to give myself exam marks for it, I´d say about 7/10 for my efforts and results,
and 0/10 for the Instument Console and Radio though! I´m still mustering up courage for that.

Another thing:
I remember that a while ago, we discussed that my CoG positioning was within feasible limits,
and I saw you addressed the subject on your Airacobra thread a couple of days ago.

Your reference to the Datum Line is presumably the one on the diagram in your post:
3 inches (0.25 ft) forward from the Tip of the Spinner - the point your 11.48 ft measurement to the CoG starts from. This would then be 11.23 ft from the tip of the Spinner.

In my case, I have the CoG at 11.47 ft from the Spinner tip - just under 3 inches further back, which is acceptable for my purposes.

Vertically, I have 0.9 ft (10.8 inches) below the engine thrust line. Compared to your estimate of 0.75 ft (9 inches), I´m only 1.8 inches lower than that - so that´s fine too!

Today I´ve been looking at all the photos of Russian Ace´s P39D-2´s, trying to pinpoint one without the wing-guns. I like Unit Nr. 138555, Fuselage Nr. 27, belonging to Pilot 1st.Lt.Iskrin Nikolay Mikhailovich, Spring 1943, as it seems to have survived the war, but it´s difficult to tell if he flew it without the wing-guns.

I may just use one of the registration numbers in the Russian article, paint that in yellow on the tail, and use a plausible green colour scheme with a red star.

There´s controversy about the red spinner and red strip on the top of the fin/rudder, so I have to decide what to do there, as it would make it look rather boring...

Additionally, the blue-circle backgound is also controversial, as this seems only to apply to the English units crated over by the north route - not the D-2´s shipped via Iran, as these only had white roundels ex-factory, so I may take the blue out and draw a white outline around the red star.

We shall see....
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

Was that "Futuristic Movie" Soylent Green?
If so, it wasn't "soy substitute".....

The Monogram P-39 is not a rare kit or expensive or even out of production.
I believe you can still find it mail order or in stores for about $15 or so.
They more modern pressings are in a Medium Gray plastic while mine is a very Dark Green.
In fact, I believe I actually have at least two of these kits along with other Airacobra kits in 1:72 scale.
The only Airacobra kit I have ever completed was a Revell 1:72 when I was very young. It was in a Medium Green plastic which is much lower quality than the Monogram material. I believe the two companies are now merged as Revell-Monogram though some kits are obviously of one or the other company's legacy. Revell Germany is a different game but I don't have a large sample of their kits.

I picked the Monogram 1:48 P-39 to look at because by reputation, it is supposed to be one of the more accurately scaled kits.
I did detail painting on my kits but not camouflage because I didn't like the idea of hiding the shape because that was what I was most interested in. I do need to find the large set of model paints I have accumulated over the years.

Regarding the Console and Radio:
My Console is wrong and the Radio may not have actually been there. It isn't shown in the box art for the Monogram kit nor is it shown in the reference drawings I am using.

We just got some unexpected and unannounced visitors, so I will continue this later.

- Ivan.

 

[Ivan]

Another thing:
I remember that a while ago, we discussed that my CoG positioning was within feasible limits,
and I saw you addressed the subject on your Airacobra thread a couple of days ago.

Your reference to the Datum Line is presumably the one on the diagram in your post:
3 inches (0.25 ft) forward from the Tip of the Spinner - the point your 11.48 ft measurement to the CoG starts from. This would then be 11.23 ft from the tip of the Spinner.

In my case, I have the CoG at 11.47 ft from the Spinner tip - just under 3 inches further back, which is acceptable for my purposes.

Vertically, I have 0.9 ft (10.8 inches) below the engine thrust line. Compared to your estimate of 0.75 ft (9 inches), I´m only 1.8 inches lower than that - so that´s fine too!

Hello Aleatorylamp,
Perhaps I should be responding to this in the Airacobra thread, but there would not be a context for a response.
Something is very strange here. I don't think I have ever used 11.48 feet from the Datum or from the Spinner Tip as a CoG estimate.
The mistake I had made earlier was in reading a diagram as indicating the Length of 30 feet 2 inches was from Spinner Tip to Rudder.
Other diagrams indicate that the 30 feet 2 inches is actually from the Datum to Rudder.
Since the Datum appears to be 3 inches Ahead of the Spinner, that really makes the Length from Spinner to Rudder 29 feet 11 inches.

My original estimate for CoG was 11.25 feet behind the Datum which I assumed to be the Spinner Tip.
It was first revised to 11.40 feet and then to 11.35 feet from the Datum which is the number I will use for my own project.
As for Vertical CoG, my original estimate was 9 inches (0.75 feet) below the Thrust Line.
That has not changed.

The Vertical CoG and even the Horizontal will vary a bit depending on if the Landing Gear is Up or Down, but we can't really simulate that very well in CFS. You can of course use whatever numbers you like. I can only tell you my best guess at the moment.

By the way, I did notice the little spur that appears on the Pitot Tube in your more recent screenshots.

Time to go do some more editing on the Eric Johnson model. This time the edit looks to be pretty extensive.
It is a difficult repair to do without either fixing the Gull Wing shape that isn't supposed to be there or leaving the weird shape in place and just connecting the dots in a better fashion.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Thanks for your answer! My brain is doing quirky things.
I should have answered on the other thread, and also, you are quite right,
you never mentioned 11.48 ft, but 11.35. I should have quoted:

"Longitudinal CoG for the model will be
Fuselage Station 136.2 or 11.35 feet from the Datum line."

...then I wouldn´t have made yet another mistake. Actually, at the end it´s
better that the mistake-mess is kept here on this thread!

With this new calculation, the CoG should be 11.1 ft from the spinner tip.
With my 11.47 ft, it would make the difference in my case a bit greater:

I´d be 0.37 ft or 4.44 inches out, so I will most probably be letting my
Qbasic Modifier Program have another go at this!
That should get a little adrenalin flowing again!

About the scene in the film - now I remember! It WAS Soylent Green, and
of course, it WASN´T soy substitute! Uffff...

So the Gull-wing aspect of the trailing edge would be erroneous. Interesting.
Perhaps the upward slope to the fuselage from the trailing edge should be flatter.
I´ll also have a look there.

Update: It seems the fuselage component parts in the aft wing-fillet area, condition
the way the fillet is built. The contour of the fuselage-joint with the wing-fillet on the
model is too horizontal in the rear, and should curve downwards somewhat.
That way the trailing edge at the joint would be lower and also a bit tucked in.
The lower aft-fuselage on the model is too straight, and should be a little rounded.
Adjusting the lower parts of the different fuselage-slices, would pull down the vertices
to which the aft wing-fillet vertices are connected, and might well do the trick!

Cheers,
Aleatorylamp

 

[aleatorylamp]

Hello Ivan,

The CoG shift of 4.44 inches forward and 0.15 inches upwards went well.
Nothing broke, although the tachycardia still lasts!

Now I´ll shift the textures into place and redo the animations, but that will be quite fine.
Then I´ll see how it goes with the lower aft fuselage to see how the wing-fillet shape improves.
Thanks for the tip!

Update: The AF99 texture-mapping went quite quickly (quicker than writing a
Texture-shifting QBasic routine!), and the animation was no big deal.
Now the CoG as located as per your calculations, thank you very much!
Let´s see what happens with the wing-fillet now.

Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

Be careful about taking the numbers that I am using as factual. They are ESTIMATES.
I just realised that although I told you about the Vertical CoG, I didn't really mention the Longitudinal CoG except to say that what was there was pretty close.
I continuously revise my numbers as I work.
The Vertical CoG estimate of 0.75 feet below the Thrust Line has not changed since I started but that is not because I really did a lot more than very quick observations with diagrams that I have already posted in the Airacobra thread.

Be CAREFUL with those drawings and diagrams because I can tell you that they are contradictory.
I just had to pick one that I believed more than the others or combine pieces of data from multiple sources.

So far, my original Longitudinal CoG has gone from
11.25 feet to
11.40 feet to
11.35 feet.

The Datum point has changed though!
To be honest, these numbers don't really matter all that much as long as the other locations of weights are in agreement.
I believe there are other factors that are much more important and they are mostly in the AIR file.....

- Ivan.