Analysing and modifying the AFX file with QBasic.

[aleatorylamp]

Hello Ivan,
The -Q model appears to have been the final production model, which would well justify your choice, and also offers an ample choice of variants. I have also seen that this model has the largest amount of detailed technical information available, and I believe it was the best of all at altitude performance.

Anyway, I think a reasonably nice, transparent and inhabited cockpit is always a great enhancement for a model upgrade. A few years ago, I would never have said this. When I was re-working FS98 models to upgrade or modify them, I would always go for 1) accurate, rounder shapes, and 2) moving control surfaces. I put much less emphasis on a transparent cockpit (most were open cockpit anyway), which I´d happily leave opaque and shaded. The Battle of the Bleeds in FS98 at that time was always worse for me in transparent cockpits than moviing control surfaces.

I remember I tremendously enjoyed two DC-3 turboprop modifications (Eeeek, a jet!!!). One became a South African Turbo-Dak, and the other, the three-engined PolAir Tri-Turbo.
Both kept the opaque cockpits, and here the main work was the engine nacelle shapes (and the skis on the PolAir). Another interesting factor here were the 2x1424 shp PT6A-65AR or 3x1173 shp PT6A-45A turboprops in the respective .air files, to see how this power gave them their STOL capabilities. The Tri-Turbo, had spectacular performance and was successfully used on logistics missions to Station Nord in Greenland, and Rothera in Antarctica.

With the more complicated CFS1 Bleed Battles, that has now changed, and the emphasis now being on building cleanliness, and of course, as before, shape accuracy, and the topping on the cake is now the transparent cockpit,rather than moving control surfaces.

Textures have always been a bit iffy for me, but in this case the mistake is quite apparent and not yet addressed: I understand that the inaccuracy you are referring to on my present Krasnaya Zvezda is that the blue circle-background is smaller than the Zvezda-spikes, and/or that the blue circle (Siniy Krug)

, can be absent.

The results of your CoG research will be very interesting. In my case I´m using my only resort, the "reasonable approximation" concept. The calculation of how the weights of all the different tanks, armament and munition is distributed, is of course crucial.

I have done away with the wing-guns, so I´m calculating the resulting weights. I wonder if you could correct me if I´m wrong:

As far as I can see, the weight of the four 0.30 cal. machine guns would have to be deducted from the 5626.8 lb Aircraft empty weight, and the corresponding ammo reduction would come out upon deletion of the wing guns in the Dp files.

OK, then! Further Good Luck with your CoG calculations.
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

My actual reason for thinking about doing a P-39Q is that it along with the P-39N was the most used by the Russians.
Without the Wing Guns, either of these would have been a pretty fair fighter, especially at low altitude.
In any case, the basic model is nearly identical except for a few textures, so doing yet one more is easy.

I don't actually see how CFS bleeds are any worse than FS98 bleeds would be. After all, the tools we are using for our CFS models are really intended for FS98. You already know I was never a fan of moving control surfaces unless the resources are available without compromising something else.

As we have discussed many times, our reasons for working on the Airacobra are different. I want to understand how this aeroplane behaved and can't just make "reasonable" guesses unless I have no choice. Those reasonable approximations may end up masking the character of the aeroplane.
After checking out a few more numbers in the spreadsheets, I will probably make yet another change in CoG which would result in more edits to the AIR file and DP file....

Regarding your Empty Weight Specification at 5626.8 pounds:
I actually have a different number for the Empty Weight of a P-39D-2 but it isn't far off.
The problem is that "Empty Weight" doesn't include Guns or Armour or Radios or anything.
The number you are really looking for is "Basic Weight" in US Terminology or "Empty Equipped".

On top of that, the weight of the Pilot needs to be added and I typically also add the weight of 1/2 to 2/3 of the weight of a full tank of Engine Oil as well. The oil capacity is a number that I wasn't sure of for the V-1710-35 engines so that is why I was looking in the Russian manual for a description of the Oil Tank. It turns out that their manual for the P-39D was in pretty good agreement with the data that I already had for the P-39C. so I am pretty sure the number I am using is correct.
The Airacobra is a real pain for calculating weights because their "Normal Loaded" weight includes only partial loads for Engine Oil, Fuel, and Ammunition.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
The problem is not really the tools we use - they are as you say all for both sims.
It appears to be the sim .exe file itself, which is a little different in that it handles 3D images a bit differently. The same .mdl file shows up with more bleeds in CFS1 than in FS98.

I can´t say it happens to all aircraft, but I´ve seen differences between the 2 sims it on quite a few of mine, and I get the feeling that moving control surfaces are a bit more bleed-free in FS98 than in CFS1, so they were easier to make. I didn´t have much technique as regards transparent canopies, and made only a few.

Regarding Russian liveries, most of the ones I´ve seen are in effect for the -N and the -Q models.
Of the -D1 coming from England there are also quite a few. Then, I´ve only seen one or two for the -D2 that seem to be authentic looking, and include the name of the ace or pilot who flew them. That was the reason for my present choice.

I have to go through my texts to see about the basic weight and subtract the wing-guns. Either that, or I´ll use the empty weight and add the weight of the cannon, the two 0.50 cal. guns, and armour plating if I can find it, (after the "C" model, it was put in and could vary, of course), so I´ll have to check that, and the liquids too, of course.

For the moment, I have (fully tanked):
Gear oil: 2 USG____ 12 lb
Engine Oil:12 USG__ 72 lB
Fuel: 170 USG___ 1020 lb

I also saw that there´s the term "Normal Loaded" and "Overload", which is really max. load, so it will have to be decided what kind of a flight plan is to be given to this model!

OK then,
Good Night! (on the opposite side of the Atlantic...)
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

There is a substantial difference in MDL format between the two simulators. That is why the AI animation doesn't work.
I believe the FS98 MDL is version 6.10 while it is version 7.00 for CFS.

It seems to me that if I give you a number "In the Ballpark", you will have something that is more accurate than the method you are planning to use. I didn't want to do that because I haven't done the calculations for the P-39D-2 specifically and some of my data is for a 20 mm armed P-39D-2 which it seems may not have existed.

Try adding 1250 pounds to the Empty Weight of your P-39D-2 and you should be pretty close.
I KNOW it won't be exact but it will be closer than I believe your calculations will be.
I believe it would actually be a few pounds heavier because the later engine had a larger Oil Supply, but I don't remember what the exact number is. I haven't started working up a spreadsheet for the P-39K yet.

First of all, one thing you should remember is that while Aviation Gasoline weighs almost exactly 6 pounds per Gallon, Lubricating Oil is not the same. Its weight per Gallon varies with Grade and temperature (because of expansion) but I believe 7.5 pounds per Gallon is a much better number to use.
Also, while Engine Oil gets consumed with engine operation, I do not believe that the Reduction Gear Oil gets consumed.
I believe it is closer to Hydraulic Fluid in a closed system.

Your Fuel Load is actually 120 Gallons and not 170 Gallon. The Fuel Tanks were revised between the C and D models from a single tank to 6 connected self sealing bags per side. There is a section of the Left Tank that serves as a Standpipe Reserve. I forget the exact amount, but it is more than the 20 Gallon Reserve found on later Airacobras. It is mentioned in the Russian manual.

Normal Loaded is only Partial Fuel and Ammunition and Engine Oil.
For example, Overload Fuel is 120 Gallons, but Normal is only 104 Gallons.
This makes calculating weights to be a pain because although the term "Normal Loaded" is used a lot, the details are not included most of the time.

There really isn't a substitute for doing proper research. I was actually planning on putting this part of the discussion into the Airacobra thread. I may still do that but it seems like you needed some data to work with.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Thank you very much for your numbers!

Sorry about the mistake on the 170 USG fuel - I honestly don´t know where that came from, and it must be the result of a typo or a wrong conversion. I even had it in the .air file, so thankfully it´s out of the way.
It´s annoying, and only contributes to make things more confusing. I´m so sorry!

OK then, so it´s back to the 37mm cannon for the -D2, as I had before.
This would be correct as per the second batch of 158 machines on the 1941 Lend-Lease Order, P-39D-2-BE (Model 14A-1), after the 336 first batch of units of the P-39D-1-BE (Bell Model 14A)) were built. Only some, not all of these 158 -D2´s were sent to Russia, as also happened with some some -D1´s.

Thus, I´ll discard my idea of a having a P39D-2 with a field-mounted 20mm cannon as per the three illustrations of Russian -D2´s with their pilots´names, depicting the 20 mm Hispano cannon.
I´ll put in the fatter, shorter 37 mm muzzle into the spinner, and use one of the two other liveries I had originally thought of.

Regarding your suggestion of adding 1250 lb to the empty aircraft weight, I was calculating what weights this includes, to distribute them between the .air file, fuel tanks and Dp files.

I am led to believe the 1250 lb include 104 USG "normal" fuel = 624 lb.

Oil: 12 USG engine-oil and 2 USG gear-oil would be 90+15 = 105 lb. Thus, fuel + oil = 729 lb.

Adding the (light-weight?) 160 lb Pilot + parachute, this would add up to 889 lb.

Subtracting from your suggested 1250 lb, this would leave 361 lb for nose armament.

My calculation of the 20 mm Hispano Cannon and its 60 rounds, plus two 0.50 nose machine guns with their 200 rounds each, gives exactly 341 Lb, so there are still 20 lb free. Maybe one should include a heavier pilot?

Alternatively, the Oldsmobile 37 mm cannon, would add another 62 lb to your suggested 1250 lb, accounting for the weight difference of the cannon itself, as the weight of the 30 rounds for it is apparently almost identical to that of the 60 rounds of the other.

Update:
"Normal load" for this aircraft is apparently 7650 lb. Even with the heavier 37 mm cannon, with this calculation, we would have a nimble gross weight of 7038 lb instead.
The 4 wing-guns and ammo would add another to 364 lb, but as they are removed on this model, the lighter weight would be noticeable.
However, I wonder if it is now too light, with only 7038 lb?

I have a detailed breakdown of weights of the different types of armament and ammo involved, but I won´t bother you with all the numbers.

Thanks very much again!
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

Your 170 Gallon Fuel Load is NOT a typo.
It happen to be the Fuel Load of the P-39C.
Substituting Self-Sealing Fuel Bags (6 per side) in place of the single plain Tank per side reduced the capacity to 120 Gallons for the P-39D and later models until they were reduced even further to save weight.

A field modification to a 20 mm Hispano is actually a pretty good possibility if you should choose that option.

The 1250 pounds I suggested is actually the difference between Empty Weight and Zero Fuel Weight in the AIR file.
It does not include Ammunition or Fuel but includes some amount of Engine Oil. I don't know if this is a reasonable percentage of the Oil Capacity because I haven't compiled notes for the later series E6 Allison yet.
This is also making a few assumptions because equipment and armour varied between models.
I believe to be consistent, it should be a bit more than the 1250 pounds.

I would strongly suggest you list some of your itemized weights that you stated earlier that you were reluctant to list.
I can tell with the numbers that you have posted that there are some errors in those numbers but I can't tell where the errors are....
I can tell you very simply that the Empty Weight of my P-39D/F is several hundred pounds lighter than your P-39D-2 but the loaded weight even without Bombs is heavier than what you came up with, so there is either bad math or incorrect numbers somewhere.

Hey, perhaps my own numbers are incorrect?

- Ivan.

 

[aleatorylamp]

Flight Plan

Hello Ivan,

Thanks for your offer in helping to discover my possibly incorrect numbers and/or maths errors.
It will definitely save going in circles...

I was going to post the list of weights for the flight plan for my model, but given the varying numbers to be found everywhere, I don´t know how precise they can be.
I know it´s difficult to define anything without any concrete numbers, so I was in the process of preparing a couple of possibilities for the Airacobra P-39D-2.

This one would be for a -D2 model with:
1 x 37 mm cannon,
2 x 0.50 cal. nose guns,
No wing guns.

Spec. Empty weight: 5646 lb (although the hand-written spec. sheet states 5626.8 lb)
Spec. Normal load : 7650 lb
Spec. MTOW: 8300 lb

Empty:.....................5646 lb
Gear oil: 2 USG..............15 lb
Pilot + parachute..........160 lb (although I´d prefer this to be 300 lb)
37 mm Cannon:............213 lb
2 x 65 lb Nose guns:.....130 lb (0.050 cal.)
...............................-------
Dry weight:...............6164 lb

Fuel: 104 USG:............624 lb
Engine Oil: 12 USG.........90 lb (Use 15 USG fuel in air file as this is consumed)
..............................-------
Loaded Weight...........6878 lb (without ammo)
Ammo:.......................160 lb (30 rounds for cannon and 2x200 rounds for MG)
..............................-------
Operational Weight.....7038 lb

This is what I thought was a bit on the light side, although it would certainly make a nimble fighter! With the alternative, perhaps better 20mm Hispano Cannon possiblity I´m also pondering, this would be 62 lb lighter - even more nimble!

I´d expect armour to be included in the empty weight, so that wouldn´t warrant any extra weight. If it´s too light, perhaps one should increase fuel, pilot weight or something...

Cheers,
Aleatorylamp

P.S. ...and here´s the armament data I was afraid would be a bit boring:

Guns, cannon and their weights:
-------------------------------
37 mm. M4 Browning Autocannon:
213 lb., 2000 fps, 150 RPM.
Ammo: 30 rounds x 1.99 lb (1.34 lb projectiles + 0.16 lb gunpowder + 0.49 lb shell)

20 mm. HS.404 Hispano Motor Cannon:
151 lb, 2800-2900 fps, 600-700 RPM.
Ammo: 60-round cartridge: 22 lb in total.
HE round: 0.57 lb including shell. Projectile: 0.29 lb. Explosive filler: 0.21 lb.

0.50 cal. AN/M2 Browning nose MG:
65 lb., 2910 fps, 750-850 RPM:
Ammo: 200 rounds. Cartridge: 0.25 lb. Projectile: 0.1 lb

0.30 Cal. AN/M2 Browning wing MG:
31 lb, 2800 fps, 1200-1400 RPM:
Ammo: 1000 rounds. Cartridge: 0.06 lb, Projectile 0.024 lb

Combinations without wing guns:
-------------------------------
A) One 20 mm. cannon and two 0.50 cal. guns:
would weigh 151 + 130 lb = 281 lb
Ammo.... 60 lb and 100 lb = 160 lb.
.....................................-------
......................................441 lb >>>>>> here I had a maths error: It´s not 341 lb!

B) One 37 mm. cannon and two 0.50 cal. guns:
would weigh 213 + 130 lb = 343 lb
Ammo.... 60 lb and 100 lb = 160 lb.
....................................--------
......................................503 lb

Saved weight taking away wing guns:
4 x 0.30 cal. Browing Wing MG 4 x 31 = 124 lb.
Ammo:..................... 4000 x 0.06 lb = 240 lb
..................................................-------
.................................................. ...364 lb

Cheers, and thank you very much again!
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

I just posted a page from the P-39Q-1 Operating Manual which should give some better numbers.

I can tell you offhand that the weight of your 37 mm Cannon is quite a bit low.
The number I have been seeing is 238.4 pounds for just about every listing for the gun.
Where did your number come from?
The same applies to the .50 Caliber cowl guns.
Your weight might be correct for the bare gun, but there is some other equipment required for actually using the gun.

If you do the calculations for cowl guns and 47 mm cannon ammunition, I believe you will come up with a number about 30 pounds heavier than the number you have been stating.

There is also a table of armour weights if you want to try to do some calculations yourself.
Armour is NOT included in the Empty Weight of an aircraft.

By the way, the firing rate you have for the .50 Caliber M2 is for a free firing gun.
The synchronized gun will be firing a LOT slower.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Thank you for your comments.

There are several different pieces of data for just about all the specs concerning the four types of guns. It would be easy if I knew something about fire arms other than the pellet air-pistol I have.

There are several different sources giving sometimes consistent and sometimes indifferent information on a given caliber, there being several pieces of information regarding weight, rpm, fps, cartridge weight, projectile weight, explosive weight, links, containers, etc., etc., no doubt depending on details like when it was manufactured, what type of weapon it is, and where it is mounted - perhaps on an anti-aircraft land battery, a ship, a gunboat, a plane, an armoured car, a tank, a tripod, a jeep, or hand held.

What I will do is to calculate it from the other end: The 7650 lb operating weight.
Subtracting fuel, engine oil and ammo will give the .air file dry weight. Fuel and oil go into the tank and ammo goes into the Dp files.

Here´s the new Flight Plan:

Operating Weight:....7650 lb:
Fuel and oil:.. minus - 714 lb. 624 lb fuel, 90 lb (12 USG) Oil, (15 USG equivalent in fuel)
............................ -----
............................ 6936 lb. (dry weight with ammo).
Ammo:
Minus 60lb + 100lb.....- 160 lb (30 or 60 cannon rounds, + 2x200 rounds for 0.50 MG)
.............................------
.............................6776 lb
+ 100 lb for
good measure:...........100 lb
.............................-------
Dry weight
in .air file.................6876 lb

This would also tally with your recommendation of adding 1250 lb to the empty weight that I had in my .air file before.

Then, the 30 or 60 cannon rounds´ weight would be defined in the Dp files depending on the cannon chosen.

So, that would be it! End of problem.
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

The number you arrived at is fairly reasonable, but the way you arrived at it is not entirely correct.
Here is why:

First of all:
60 pounds is correct for 30 rounds of 37 mm but
100 pounds for 400 rounds of .50 Cal is somewhat light.
The P-39Q manual lists 124 pounds for 400 rounds.
The P-39D itemized weights list 129 pounds for 400 rounds.
Yes, ammunition weight changed a bit over the years.
I generally use the value that is reasonable for the period but realistically a couple pounds doesn't make much of a difference.

Now keep in mind that your "Operating Weight" is an arbitrary measurement.
You are assuming Normal Loaded Weight includes full Oil capacity but it does not.

What we are really looking for in this case (at least in CFS) is the "Zero Fuel Weight".
I figure the user can determine the Fuel and Ammunition load but doesn't really have much control over Engine Oil and other fluids.
Because of this, I normally assume 1/2 to 2/3 Engine Oil is included in the Zero Fuel Weight in the AIR file.
Coolant, Hydraulics, and in this case Reduction Gear Oil would be at full capacity at all times and not be expended during the flight.

At Take-Off with full internal Fuel and Ammunition, the weight will be slightly low (about 1/2 Engine Oil capacity weight low).
When completing a mission and returning with no Ammunition and minimal Fuel, the weight will be slightly high by a few pounds because folks don't tend to use up all the Engine Oil. (That would be bad!)

Even with this method, we probably won't get exact numbers but we will get pretty close to where they should be in my opinion.

I hope this makes sense.

- Ivan.

 

[aleatorylamp]

Weights OK then.

Hello Ivan,
Thanks for your fast answer, and for the info on the correct 124 lb for the 0.50 cal. rounds.
That now increases the 0.50 cal. ammo weight in the Dp file from 4 to 4.96 oz per round.

So, technically this means a reduction of 24 lb to the 6876 lb Dry weight in the .air file, but judging by your comment that the Dry Weight is now fairly reasonable, and that the way I had arrived at it was not entirely correct, I would expect that this should now NOT be changed.

Regarding the non-consumption of your proposed partial engine oil tankage in "Zero Fuel Weight", the weight discrepancies at takeoff and on return after a mission could be avoided by including the oil in the tanks as equivalent in fuel.

This would come at the price of a different inaccuracy, of course, namely a falsely extended range, which would probably be worse than what you are proposing. But wait! One could always define a 15 USG equivalent of 12 USG of oil as non-usable fuel in the fuel tanks.
How about that? Or better: Using 2/3 of the oil weight here, it would be 10 USG equivalent in fuel.

So left and right tanks would have 65 instead of 60 USG of fuel each, and there would be 5 USG defined as unused fuel in each tank. Now, the only inaccuracy would be that the engine oil tank would always be 2/3 full.

Anyway, using your proposal for engine oil:
"Overload" oil capacity is 12 USG i.e. 90 lb, and "normal" is 8 USG, i.e. 60 lb, so technically, 30 or 40 lb of the oil would be added to the Zero Fuel Weight, but I won´t alter that, for the reasons expressed above - as you said the Zero Fuel Weight I had was fairly correct.

Thank you very much for your help and attention - now the weight calculation for my model is far more realistic.
Cheers,

 

[aleatorylamp]

Operating Weight without the 4 wing guns.

Hello Ivan,
I was missing one point, namely the weight reduction due to the elimination of wing guns.

To benefit from this loss in weight, the 7650 lb Operating Weight would have to be reduced
by 364 lb, to account for the absence of the 4 wing guns and their 4000 rounds of ammo.

364 lb would be have to be subtracted from the Zero Fuel Weight, so we would be left with an Operating Weight of 7296 lb instead of 7650, and a Zero Fuel Weight of 6512 lb instead of 6876.

I wonder if this sounds reasonably correct...
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

I don't think your 7650 pounds "Operating Weight" includes a full 1000 rounds per wing gun.
Let's put it this way yet again: My much lighter P-39F weighs more than that with full fuel and ammunition.

I have been trying to tell you that the "Operating Weight", Normal Loaded Weight and such for the Airacobra are not necessarily meaningful numbers. That is why it too a lot of poking around to find out what WERE meaningful numbers.

If I were you, I would take the Empty Weight, add 1250 pounds and then subtract the weight of 4 x .30 Caliber MGs and enter that into your AIR file. If you get your DP file correct and Fuel capacities correct, the rest should fall into place
(....but for the errors in my estimate of 1250 pounds)

THIS IS WHY I SUGGESTED EARLIER THAT YOU NEEDED TO PIN DOWN A LOT OF NUMBER FIRST.
It is pretty late in the game to be doing what you are doing now because you are bound to be back to performance tuning after this.
http://www.sim-outhouse.com/sohforu...-with-QBasic?p=1144505&viewfull=1#post1144505

- Ivan.

 

[aleatorylamp]

Hello Ivan,
OK, of course... Thank you.

Pinning down meaningful numbers for all sorts of different pieces of data for many different aspects of an airplane is far easier said than done for me, for the reasons I have been mentioning again and again for a number of weeks now, and which I will not repeat yet again.

And no, I don´t need another argument, thank you very much. The link you just posted does not help in this sense, even if it illustrates your point, but it also illustrates mine. Also, your comment preceding the link is totally superfluous.

I know you endlessly repeat the need for research and data collection, so you don´t need to insist so often. All I can say is that I do what I can, as far as I can understand, and I am grateful for the information you let me have.

It repeatedly comes to a point that makes me question the benefit of this occupation. It is supposed to be fun, and not a pain. I think I´ll take a holiday from this activity after I finish my corrected version of the Airacobra, unless I stop before, and forget about it.

So, back to the point: 1000 x 4 rounds would then classify as "Overload" as well, and "Normal" would more likely be 800 or 750 rounds per gun. The weight to be discounted for the removal of guns and ammo would then be between 48 and 60 lb less than the 364 lb I had before. I guess about 300 lb should be fine.

Curiously enough, I had done my performance tuning with too much ammo (the wing guns were still on), too much fuel (170 USG), and too little Dry Weight in the .air file, as you know. In fact, I originally had it at 5441 lb, even lower than the 5626 lb I mentioned yesterday.

Anyway, the resulting total weight of that combination was very nearly the same as it is now, after the new weight adjustments. I did some quick performance tests one or two hours ago, I have established that performance needn´t be corrected. That is quite lucky.

So tomorrow I can continue with the Battle of the Bleeds.
Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

My apologies.
I suppose I am pushing too hard.
We really have quite different goals for this project.

Last night I was working on edits to the drawings I plan on using.
It turns out that the ones I selected are actually not significantly better than the ones by Paul Matt, so perhaps I will be using both sets of drawings. I started looking at a Transparent Canopy and what I would need to construct it.
I believe this version will be built by Eyeball estimates rather than actual measurements.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
OK then, not to worry.

I´m glad that the drawings are usable after all.

I measured the basic reference points for the canopy at the ends, top, and bottom, and then the top and bottom width of the thick central metal frame part, and finally the door height and width.
All else is eyeballed, and worked out OK.

So, good night!
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

Quite a few drawings are useable.
It is just a matter of which ones are better. I believe the Polish Monografie drawings are better but for a print copy to mark up, the Paul Matt drawings look nicer.

- Ivan.

 

[aleatorylamp]

Hello Ivan,
Ultimately, it will be more a matter of how well AF99 allows a shape to come through.

I´ve been negotiating the exhaust bleed business for quite a long time this afternoon, and it is very difficult because everything is in Bory Main in this area. The mid-fuselage section is glued to the left and right wingroots, and there´s nowhere decent to glue the exhausts to. For the moment, they are in Inner Wing Mid Left/Right, with the obvious problem that wingroots portrude below and are in Body Main.

Do you remember the Japanese tin toy-airplanes? They had their exhaust manifold drawn onto the nose sides. It wouldn´t be the first time I´d do it this way in AFD99 either. Properly shaded and drawn onto the fuselage-side texture-bitmap, it even looks quite 3D.

Cheers,
Aleatorylamp

 

[Ivan]

Hello Aleatorylamp,

I don't think the Airacobra has such a difficult shape. (Famous last words!)
Except for the Nose Gear, everything looks pretty straightforward.

As for the Exhausts, I haven't gotten there and I don't know that I will at the end.
For me, messing around with Eric Johnson's AFX is mostly a matter of procrastination and playing around without really doing anything.
It is a chance to experiment with a few ideas and test a couple assembly sequences to see how they look before working on the project that really matters to me.

I was looking at my version of the EJ AFX and don't see the Wing Root / Fillet bleeds that you were chasing.

Last night and this morning, I started working on a Transparent Canopy.
Actually what I was doing was really the Canopy Frame rather than the Canopy, so nothing is really transparent yet.
I ended up having to do minor modifications to the Mid Fuselage Component and will likely do a lot more to prevent bleeds.
At the moment, I am having some difficulty convincing one of the Pilots that he should fly the P-39D.

Here is a screenshot of the first test to see how the pieces fit.
The problem here is that my Eyeball did not really line up well with the existing textures, so I will probably do some minor changes.
Yes, there is no Glass at the moment, but it is very simple to do; It is just a matter of connecting the dots in most places.
I will certainly need to create a new texture file for the Canopy Frame, but I will probably need new textures for the Flaps as well, so it isn't such a big deal.

- Ivan.

 

[aleatorylamp]

Exhaust bleed fixed!

Hello Ivan,
No, I agree, the Airacobra is not a difficult shape, and the cockpit, as you say, is not difficult either, of course.

What I meant was more with reference to the small differences on different source drawings, which one can decide to follow or not, depending on one´s own criteria, but which ultimately also depend on how well or how practically a given shape can be depicted in AF99, or how visible these small differences come through, or if they are worthwhile. I didn´t mean that they were complicated shapes.

From your screenshot, it looks like your canopy is making good headway.

I also notice the 2D pitot-tube spur shows up correctly on your display. Mine filled in the front-upper part. I think it´s the modern Open GL graphics that can´t do some old things that the old 3Dfx graphics were better at. The new ones obviously have better capacity for other things, although these would be unused in CFS...

Regarding the mid-fuselage/exhaust subject:
For the moment, have you kept the original wing-fairing / wheel-well distribution?
I remember you said that there didn´t seem to be much point in having the wings as upper and lower component halves, but that apparently didn´t include the fairings.

It didn´t seem to be working very well before, so I put the fairings as single components into Body Main, glued to the mid fuselage, and then put in a Wing/Fuselage template on the wing joint. The result is that everything works, except for the exhaust bleeds through the wing seen from underneath. Exhausts, as I said, are still in Inner-Wing Mid L/R.

Now I got the idea of dividing the mid-fuselage into top and bottom sections. This way the fairings can continue glued to the bottom one, and the exhausts can be glued to the top one.

If this doesn´t work well, I´ll revert to the original build-distribution of the belly parts in Gear Centre and see what other maneuevers are possible.

Update: It worked! ...which I was more or less expecting. Now there are some remaining interactions between the pilot and the fore- and aft upper-cabin metal, but this should be curable with correct glue-sequencing.
Here are some shots. ...I still have to fix the "Siniy Krug" to fit the "Krasnaya Zvezda" more correctly... and the three "fives" in the registration number, which I noticeably made out of upside-down "twos".

Udate 2:
I noticed that the oblong shaped exhaust component could perhaps be improved by slanting the fore and aft ends, rounding off the cross-section on the outside, adding 2 extra panels, and enhancing the texture bitmap shading. This may well improve to the aspect of the 6 exhaust ports on each side of the mid-fuselage. At the moment it´s not finished yet, so I´ll post a picture when it´s done.

Cheers,
Aleatorylamp