Douglas A-20 Havoc Project - Page 2
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Thread: Douglas A-20 Havoc Project

  1. #26

    Plain flaps on the way

    Hi Ivan,
    I just had a look at my Russian Airacobra - fortunately it´s OK with its split flaps. I´d forgotten about that, although I do remember deviations from the correct proportions that we managed to so successfully correct. That was a nice and interesting project, and yours came out very well too, in the several variants you provided!

    I had checked the numerous and detailed Havoc drawings Smilo had sent me, and was able to discard a few inconsistent drawings I had found at the time. Such inexactitude seems to be widespread on several sources, most probably inherited from sites 20 years ago, when information wasn´t abundant on the internet, and much was inexact.

    Anyway, as regards the complications of Havoc details: I think I´ll sacrifice the details of the 4 wing-root stubs on engine nacelle sides. At 3 parts per stub, I´d need 12, and I definitely won´t have those, although I doubt the model will suffer very much from their loss. One thing I´m happy enough about right now, is that after doing the wing cut-outs, it´s thankfully not bleeding any texture triangles over the inner corners.

    Update:

    Main Parts for plain flaps fit into parts count very well, without simplifying the fin or the intake scoops, but triangular edge fillers on the flaps create bleeds, so they must be left out. This will cause some gaps when seen from the side, but can´t be avoided. Now I´m on the glue sequences so flaps won´t bleed through wings or nacelles. It´s not going too bad.

    Cheers,
    Aleatorylamp.
    Last edited by aleatorylamp; December 3rd, 2020 at 10:58.
    "Why make it simple if you can also make it complicated?"

  2. #27
    Hello Aleatorylamp,

    The EJ Airacobra project was a serious learning experience in flight modelling. It is a great example of how things changed between FS98 and CFS AIR files. The center of lift offsets were meaningless because everything was done via moments.
    It took a lot of effort to get the instability where I wanted it to be.....

    Regarding the mistakes in A-20 drawings and specifications:
    The problem came about because of the design of the aircraft.....
    Everything is the same length from Station Zero on back, but the dimensions changed depending on the nose that was fitted and THOSE varied a lot in dimensions.
    The manual would often list a single overall length but the drawing that accompanied that specification did not match the length that was listed because the attack nose and glazed nose were not the same length.
    Of course as new versions were built, there got to be many more variations in length and shape.

    The kind of detail I was thinking about was 3D Cowls that I could not put on the Mitchell for lack of resources.

    - Ivan.

  3. #28

    Plain Flaps working!

    Hello Ivan,

    I see. Then it´s just as well you mentioned the different lengths depending the type of nose, so I´ll check the length for the solid nose before posting another WIP. I also noticed small differences in the placing of the 4 nose-tip machine-guns, and I´ll check how the RAAF Havocs had theirs.

    Anyway, I finally got the plain flaps in, and with no bleeds! I went scrounging for free components and got 4, and managed to separate outer wings into mid- and outer components, also getting outer flaps into components. As a result, the glue-sequence works very well, and the filler-triangles are back in. All rather satisfying!

    Now I only have to re-map the fuselage textures, as one of the components came from the fuselage, and this has upset the original mapping. Anyway, it´s working!

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  4. #29

    more free parts

    Hello Ivan,

    The workshop was working a night shift for the flaps corrections, and now they are busy spraying the Aussie camo scheme. This version also has shorter air intake scoops on top of the engine nacelles, which will be a help too, as it saves quite a few parts.

    Re. Havoc lengths, depending on the different noses, the blueprint dept. has seen following specs:

    45 ft 11 in (this one could be discarded)
    47 ft 4 in
    47 ft 11 in
    48 ft (currently on the model)
    48 ft 4 in

    All quite confusing. Early glazed nacelles seem to have been shorter than later glazed ones, and also shorter than the solid ones, so probably length can stay as it is.

    I´ve also seen early glazed nacelles painted over, with field adaptations of 3 and 4 nose-tip MG´s, apart from the two bigger cannons on the sides below them further aft.

    More later....
    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  5. #30
    Hello Aleatorylamp,

    I believe ALL of the lengths you listed are correct for SOME model of Havoc / Boston / DB-7. That is why it makes more sense to work from the station diagram than a "dimensional" drawing.

    The dimensions that I had the hardest time finding was the relationship of the Thrust Line to the Fuselage Reference Line or the Mean Aerodynamic Chord and the location of the top of the Fuselage in relation to the FRL.

    - Ivan.

  6. #31

    Lengths clarified!

    Hi Ivan,

    I went rummaging in Smilo´s Havoc docs, and found two separate folders with detailed
    drawings of the 2 Havocs with glazed and solid noses. It turns out the 48 ft correspond
    to the early glazed nose, which was the design I originally intended to produce. Then, the
    solid nosed version length is 47 ft 4 inches. No problem now, I can easily shorten the nose
    components.

    Further to your message just now about engine thrust-line difference to the fuselage line,
    I had already noticed the 2-degree positive inclination of engine thrust-lines marked on
    Smilo´s drawings, but I´m afraid that will be impossible to do because of the engine-nacelle
    structures.

    Parts count is at 148.8%, with 30 copmponents and 27 structures, and there´s unfortunately
    no possibility whatsoever of freeing any further components for two slanted nacelle-fronts,
    which would then get slanted propellers and slanted propeller blurs and discs, discarding the
    AA ones, but that will hardly be noticeable anyway.

    Cheers,
    Aleartorylamp
    "Why make it simple if you can also make it complicated?"

  7. #32
    Hello Aleatorylamp,

    I would strongly suggest that you DO NOT shorten the nose on your A-20.
    ....Or if you feel that you MUST, then do some more research to make absolutely sure that the length corresponds to the version you are trying to represent.

    Length differences between the early A-20 version and late A-20 versions are NOT the same.

    I also decided not to represent the inclined thrust line because it is almost not noticeable. The question was really the location of that thrust line in relationship to the fuselage. The slight inclination gave a slight bit of flexibility but I still needed to know the location of the thrust line / centerline of the nacelle before building it.

    - Ivan.

  8. #33
    Good morning, Ivan!

    Thanks for your words of caution. The diagrams with the 47.4ft length solid-nosed
    variant refer to the A-20G. The diagrams with the early glazed nose variant are from
    the 48ft A-20C.

    Well... and the drawings of the Aussie DU-G, DU-K and DU-H variants are all A-20A
    models, so I think I´ll follow your advice and leave the model as it is. The 6-inch
    variation will go unnoticed anyway.

    Here are 2 of the diagrams, which show thrust and the fuselage ref. lines. Hope it helps.

    Here´s also a screenshot showing the new flaps. Ignore the lettering - I´m still
    working on the textures.

    A fine St. Nicholas celebration to all.
    May you find some nice goodies in your slippers!

    OK, then!
    Cheers,
    Aleatorylamp
    Attached Thumbnails Attached Thumbnails A-20Gmanual - Page_1.jpg   A-20Gmanual - Page_2.jpg   A-20 new flaps.jpg  
    "Why make it simple if you can also make it complicated?"

  9. #34
    Hello Aleatorylamp,

    I have those drawings also. I believe they are from the A-20G Erection & Maintenance Manual and I have a copy of that.
    The problem is that I believe those dimensions are actually not correct. I actually have much better drawings in a couple large PDF books.
    Of course with so much conflicting data, one has to choose what to believe.
    I would suggest if you have not already done so, you should read the "Design Analysis for the A-20".


    From what I can tell, the Bomber noses were slightly shorter than the Attack noses and not the other way around.
    This seems to be supported by photographs as well at least by my eyeball. There are going to be exceptions because there were several variants of each kind of nose.
    The A-20C is listed as both 48 feet 0 inches and 47 feet 3 and some fraction inches. I choose to believe the shorter length is accurate.

    We do not have to agree in our conclusions. That is one of the things that makes flight simulators more interesting.

    - Ivan.

  10. #35

    Surprise inside the slippers for St. Nicholas

    Hi Ivan, hello Folks,

    Very interesting, Ivan, thank you very much. I´ll go with that research information then!
    My criteria is not as reliable as yours, so I haven´t changed the nose dimensions.

    Attached is the A-20 Havoc WIP-5 model. Smilo will be rather pleased, I wager, with the
    progress upto now:

    Plain flaps are on, a few cracks are gone, and the aircraft now has preliminary textures for
    the Aussie DU-K, which incidentally, seems to have had the longest list of successful sorties.
    I´m still working on the gear-door glue sequence which presents some short bleeds from
    shallow angles.

    Here are some pics and the aircraft with source files should anyone be interested.

    Cheers,
    Aleatorylamp
    Attached Thumbnails Attached Thumbnails Havoc WIP5-1.jpg   Havoc WIP5-2.jpg   Havoc WIP5-3.jpg   Havoc WIP5-4.jpg  
    Attached Files Attached Files
    "Why make it simple if you can also make it complicated?"

  11. #36
    Hello Aleatorylamp,

    Making a mistake because YOU goofed is one thing.
    Making a mistake because you depended on MY research being correct is much worse.....
    You should confirm numbers rather than just accept them. You don't know how sloppy I can get.

    - Ivan.

  12. #37
    Hello Ivan,

    At the end of the day we do what we can with what is available, and make
    the decisions we feel are correct despite contradictory or inexact information.
    Small differences go unnoticed anyway, so I´m not worried.

    The Havoc model is at present as good as I can get it. There is still some texture
    smearing under the tail in the last WIP-5 I sent, which needs correcting, and I
    intend to texture the area surrounding the nose guns. That, and the hairline cracks,
    and it will be done!

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  13. #38
    Your description of design choices seems like the best guide thus far.

    Good Luck!
    - Ivan.

  14. #39
    Hi Ivan,

    After your warning of not shortening the nose, and seeing that the drawings of the solid
    nosed unit (47.4 ft length) corresponded to the Havoc A-20G, I noticed the A-20A
    frame-strut pattern on all pictures of the Aussie Havocs with solid nose.

    This could mean that either the glass had been painte over, or perhaps more probably,
    the plexiglass windows had been substituted for metal plate, arguably to offer more
    protection than plexiglass for the machine-guns inside.

    Update: I just got the wheel-well bleed fixed. Strangely enough, altering the glue sequence
    and grouping only made it worse, and it was a matter of changing the glue angle to cover
    wheel and wheelwell from the geardoor, although the wheelwell is in another group.
    Then I put in the kind of skid fairing there is at the back, but only 2D as 3D "V" went
    beyond parts-count limit.

    Anyway, as soon as I get the textures how I want them, I´ll be uploading the model.

    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; December 7th, 2020 at 02:21.
    "Why make it simple if you can also make it complicated?"

  15. #40
    Hello Aleatorylamp,

    From what I have been able to find there actually was never a version of the A-20 that was 47.4 feet in length.

    I may of course be incorrect, but the A-20A would have been 47 feet 7 inches.
    The A-20C MIGHT have been 48 feet 0 inches but I believe it is more likely it was around 47 feet 3 5/8 or 47 feet 4 inch.
    There is enough conflicting information to argue for either dimension.

    My belief because of other conflicting evidence I have seen is that the 47 feet 4 inch length listed in the A-20G E&M manual is simply incorrect.

    You are thinking of reasons that might explain how the dimension might be correct. I believe you are wasting your time and it is simply a mistake carried over from prior versions of the manual.

    - Ivan.

  16. #41
    Hello Ivan,

    Interesting information you have managed to confirm.
    Perhaps I have not been able to explain my reasoning clearly.

    I was saying that from what I have seen, the A-20A was 48 ft in length, including
    Australian ones. As drawings of solid-nosed ones show the canopy frame contours
    on their solid nose, my belief is that they simply had their plexiglass painted over or
    substituted by metal plate, so the length of these A-20A´s was standard.

    This would mean that the 48 ft length of my model could be correct. With your new
    information of the A-20A having been 47 ft 7 inches long, then I´m 3 inches out, which
    isn´t terribly too much, although I could correct it, I suppose. Which would be more
    reliable? 48 ft or 47 ft 7 inches... that is the question.

    In my previous post I´d mistakenly quoted the A-20G length as 47.4 ft, but I´d meant
    to say 47 ft 4 inches. Anyway, it´s not so important as it isn´t the model I´m building.

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  17. #42
    Hello Aleatorylamp,

    I was under the impression you were building the early A-20G....
    Perhaps I am incorrect regarding the A-20A dimensions but if I am correct, 47 feet 7 inches is 5 inches shorter than 48 feet.
    Shouldn't the A-20A also have a pair of .30 cal cheek guns?

    I guess this is good because I had intended to build the early A-20G which is why I was a bit more concerned with getting the dimensions for the A-20G correct. The follow-ons would be the late A-20G and then the A-20J.

    - Ivan.

  18. #43

    5, not 3...

    Hi Ivan,

    Sorry, 48 ft would be 5, not 3 inches out from the alternative 46 ft 7 in.
    length, but it´s not too much considering we aren´t 100% sure which is correct.

    I´m still a bit confused as to the number of guns for the A-20, as some sources
    say 6 and others say 8. Then there is the issue that it was 6 or 4 guns, plus 2
    cannon, although those jammed and were then exchanged for MG´s.

    Anyway, if it´s 8 and not 6, it would be even more impressive!
    Great! I´ll have to check.

    So, good luck with your A-20G and J!

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  19. #44

    Example of Analysis - A-20C

    Hello Aleatorylamp,

    Attached is a station diagram for the A-20C. It isn't the aeroplane I am building but I had considered it and thought it would make a good example of why I believe some of what I do.

    From this drawing, it is clearly labeled that the overall length of the aircraft is 576 inches. That would be 48 feet 0 inches.

    The question is whether we can take this at face value.

    I have a pretty good drawing for the A-20G that I AM working on that shows that with a 75.4 inch Attack Nose, the overall length of the aircraft is 47 feet 11 inches. It also shows the "Formation Leader" nose as 80 inches long which is consistent with the length of the A-20J being 48 feet 4 inches long (actually 48 feet 3.6 inches which is consistent).

    The nose on this A-20C is shown as 66 inches long which means it is about 9.5 inches shorter than the A-20G. Either way, it certainly isn't 48 feet 0 inches.

    Now please look over the station diagram. Note that the Nose extends to Negative 66 inches from Station 0.
    Note also that the aftmost station labeled in at the formation / bombing light and it is at station 493.
    493 + 66 = 559 inches.

    So unless one is inclined to believe that last little bit of tail cone light accounts for 17 inches of remaining length, it is highly unlikely that the overall length is really 48 feet 0 inches.

    - Ivan.
    Attached Thumbnails Attached Thumbnails A-20C Stations.jpg  

  20. #45

    No free parts for cheek guns...

    Hello Ivan,

    This research is getting a bit complicated, isn´t it? Nevertheless, the possibilities
    that are taking shape are very interesting.

    I also have the station A-20C diagram with the -66 for the nose. Then there´s also
    the A-20G station diagram with a bulkhead just aft of the nose-tip at STA -63, for
    which I calculated the nose-tip at STA -70.5.

    My present intention of my A-20A being an Australian one is going to be impossible,
    as I haven´t got the parts for the two cheek guns/cannon. The cheek bulges could be
    put into the textures, but I have absolutely no free parts left for the gun barrels, so
    I am looking for another A-20A candidate without them.

    I have seen a few, with American stars on the fuselage, so I´ll be OK.
    As soon as I decide I´ll post a possibly viable pic.

    Update:
    It seems that for my solid nosed A-20 model, it is a bit difficult, although not impossible,
    to find a variant. There were some solid-nosed A-20B´s that could be fitting, with no
    cheek guns, flexible dorsal MG (no turret), and ram air-intake scoops on engine nacelles
    (I can change the non-ram scoops on my model).

    They also seem to have only four guns in the nose, two on the tip and two further down,
    slightly on the sides. I found photos of "Ball of Fire" No. 15, Dirty Gertie" No. 14, "Marty I"
    No. 62, and also "Miss Carriage" (no number), and Nos. 9 and 30. So that could be a solution.

    At the moment I´m looking for the colour scheme. The BW photos could either be plain
    khakhi brownish green or perhaps camo. I´ll see...

    Cheers,
    Aleatorylamp
    Last edited by aleatorylamp; December 8th, 2020 at 10:53.
    "Why make it simple if you can also make it complicated?"

  21. #46
    Hello Aleatorylamp,

    My own research was difficult only in the matter of finding some critical aircraft dimensions.
    Information about different versions wasn't that much of an issue though there was always some contradictory information.

    The versions with the cheek guns in pods was never attractive to me. Those pods just seem to spoil the nice sleek lines of the aircraft, but of course that is just my opinion.
    The early strafers were probably custom aircraft anyway. If you want to build one without the cheek guns, who can say you are wrong?

    I never try to build a specific aircraft. I only go for generic representative types.

    Check out the other "Pappy" Gunn specials. I believe most of them were actually B-25, but among the A-20, there were a few variations.

    - ivan.

  22. #47
    Hello Ivan,
    Thanks!
    I agree with you on the aesthetic aspect of the cheek guns. It seems that they were an option whereby the oval access lid to the lower nose guns could be altered to house an additional gun on each side.
    I found a suitable candidate for the variant with 6 nose-guns and a flexible dorsal double gun, namely the early A-20G1 that went on lend-lease to Russia, in plain khakhi green and with red stars, so now I can provide 2 real historical versions, the plain brown A-20B "Dirty Gertie" that served in Tunisia in 1943, and the Russian A-20G1 white 14.
    OK, then!
    Cheers, for now,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  23. #48
    Hello Aleatorylamp,

    I guess we both will be building variants of the early A-20G though mine won't be carrying nose cannon.

    - Ivan.

  24. #49
    Hello Ivan,

    My version is essentially a A-20-A and an A-20-B.
    Instead of a khakhi green Russian A-20-G1, I think I´ll just leave it at the camo-coloured
    Australian A-20-A, and simply ignore the two ugly cheek guns. Those were an option,
    often not depicted on pictures of the A-20-A anyway.

    Then perhaps you would like to incorporate the dorsal turret on your version instead of the
    flexible gun-mount, just to be different! ;-)

    Cheers,
    Aleatorylamp
    "Why make it simple if you can also make it complicated?"

  25. #50
    Hello Aleatorylamp,

    I personally don't think the dorsal turret on the A-20G made for very nice lines which is why I picked a version without the turret to work on. This choice of a subject was made many many years ago not long after I started my "Cry Havoc...." thread. With the later versions there is no choice, but there is a better than average chance the first version of the A-20G I build may very well be the ONLY version I build. We shall see.

    - Ivan.

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