SANCER
Senior Master Sergeant
Wow
... Ya no debería sorprenderme.
Congratulations
... Ya no debería sorprenderme. Congratulations
SBD Dauntless, from scratch
- Thread starter Witold Jaworski
- Start date
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Lovely work so far!
CommanderBounds
Airman 1st Class
Never thought the dauntless would still look so great even with it's cowling off. Impressive!
I'm actually starting a drawing project of my own. It's not going to be a 3D model but a line drawing -- that said somebody probably could make it into a 3D image if it's detailed enough
- Thread starter
- #385
Witold Jaworski
Airman 1st Class
A small off-topic note:
this winter I was busy with my daily business and took a break from the SBD model. However, in February and March I spent few Sundays helping in another project: recreating the Fokker D.V biplane, used in 1917 as an "advanced trainer" by German Air Corps.
My part was recreating the geometry of this aircraft, especially its fuselage frame made of steel tubes. All what we had was a dozen of various archival photos, a poor general drawing, and the landing gear dimensions. In this case I had to turn the available photos into the precise reference, as I did for the SBD, then use them to determine the required geometry details. Doing it, I also made a "discovery" about wing geometry of this Fokker. See details in this post.
In May I will be back, working with the details of this SBD!
this winter I was busy with my daily business and took a break from the SBD model. However, in February and March I spent few Sundays helping in another project: recreating the Fokker D.V biplane, used in 1917 as an "advanced trainer" by German Air Corps.
My part was recreating the geometry of this aircraft, especially its fuselage frame made of steel tubes. All what we had was a dozen of various archival photos, a poor general drawing, and the landing gear dimensions. In this case I had to turn the available photos into the precise reference, as I did for the SBD, then use them to determine the required geometry details. Doing it, I also made a "discovery" about wing geometry of this Fokker. See details in this post.
In May I will be back, working with the details of this SBD!
Great stuff! Be cool to see pictures of the Fokker!
- Thread starter
- #388
Witold Jaworski
Airman 1st Class
Important update about this SBD project: thanks to C West help, I identified a microfilm roll set of the original Douglas documentation for the SBD/A-24. In June I ordered its copy from NASM and now I am waiting for these materials. When I got them, they will be scanned by a local service company which scans various museum archives. This is not cheap, because the only possibility is to scan all microfilm frames (and pay for each frame, of course - I estimate that this set of seven microfilm rolls contain about 5500-6000 frames). Then I will organize these scans for quick use as the reference materials.
In the meantime, I am going to update my P-40 model, also using original blueprints. I already bought their scans. See this thread about my experiences on this subject.
In the meantime, I am going to update my P-40 model, also using original blueprints. I already bought their scans. See this thread about my experiences on this subject.
- Thread starter
- #389
Witold Jaworski
Airman 1st Class
Finally (after 5 months) I received the Douglas SBD microfilms from NSAM (7 rolls).
I have already contacted a local service provider, who scans microfilms for museums. They promised me to scan them in the beginning of December.
(I have no any microfilm viewer, and do not want to spoil these films in a slide projector. At this moment I just checked that the title page of these microfilms says that this is the Douglas SBD/ A-24, and that it contains blueprint pictures).
I will keep you informed on the progress.
I have already contacted a local service provider, who scans microfilms for museums. They promised me to scan them in the beginning of December.
(I have no any microfilm viewer, and do not want to spoil these films in a slide projector. At this moment I just checked that the title page of these microfilms says that this is the Douglas SBD/ A-24, and that it contains blueprint pictures).
I will keep you informed on the progress.
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Lucky13
Forum Mascot
vikingBerserker
Lieutenant General
That's awesome! I was fortunate enough that the local library had newspapers archived on rolls of microfilm and thus had the readers. You could print out one frame at a time but even better it would allow you to create a pdf file. I have like 12 rolls and never thought about hiring a company to do that, thanks!
- Thread starter
- #393
Witold Jaworski
Airman 1st Class
In June 2019 I followed C. West suggestion and ordered a set of Douglas SBD original technical documentation from U.S. National Air and Space Museum. Technically these blueprints are stored on several microfilm rolls. In that time all what I knew about this package (NASM id: "Mcfilm-000000408") was the information printed on the order form:
As you can see, this set has no index, which I could order earlier to examine its contents. When I finally received these microfilms in November 2019, I also discovered the meaning of enigmatic "(roll C" in the item description: it was truncated phrase "(roll C missing)"!
Well, this set was incomplete, but anyway I ordered its high-resolution scans from a local company that provides professional microfilm scanning services to museums. In January I received these data (4700 high-res, grayscale images in LZW-packed TIFF format – in total, about 300 GB). Finally I was able to scroll these blueprints. Frankly speaking, I was afraid that the most important drawings were lost with the missing roll C. Fortunately, during the initial review I noticed many detailed assembly blueprints among the scanned images. I even found a complete inboard profile of the SBD-5:
Here you can download the high-resolution version of this inboard profile (about 70MB).
The scanning company (Digital-Center, located near Poznan) did its job well, adapting the scanner resolution to the size of the depicted drawings. Scans of frames that contain large assemblies are usually 11 296 px wide and 7 874px high, which ensures that even the smallest references are readable. For example – see these four subsequent frames of the fuselage assembly drawing: 1, 2, 3, 4 (beware: size of each of these linked images is about 70MB).
There are even larger images in this result set: the biggest one is about 20 000px wide. The smaller drawings of various details are scanned at 7 672x5 682px.
Conclusions from the first review of this microfilm set are as follows:
These blueprints describe SBD-4 and SBD-5 (which is OK – the SBD-4 is similar to SBD-3, and SBD-2, while SBD-5 is nearly identical to SBD-6). It seems that rolls A-F were made from September to October 1943, while their updates – rolls XA, XB – in January 1944. Because of the missing roll C, this documentation is not complete. In general I could not find the fuselage ordinates (I only found the wing ordinates). My first impression is that the missing roll C contains most drawings of wing ribs and at least half of the fuselage bulkheads. Fortunately, there are drawings of the tail bulkheads and the firewall on the other rolls.
For my project I need to organize these blueprints into a tree-like structure, with the largest assemblies in the root (as described in this post). However, after this initial review I could not determine the rules of the drawing numbering system used by Douglas. (I wanted to use them for quick grouping all parts belonging to the same subassembly). It could happen that in this Douglas factory the drawing numbers were assigned sequentially, just as the subsequent blueprints were ordered! It also seems that some of these drawings use original Northrop numbers, dating from the SBD predecessor: the BT-1 dive bomber.
To organize this documentation I have to start from the general assembly drawing and then step down to its subassemblies. For this purpose I need an index of these blueprints. Recreating such a thing is a monotonous task that will take some time, but I cannot see better option to fully explore contents of these microfilms. What's more, I think that once such a list is created, it can be also useful for the others. While NASM forbids publishing technical drawings from their microfilms by any means (except so-called "fair use", which I am stretching a little in this article), I still can publish such an index. Of course, I will also donate its copy to NASM. I hope that in this way the eventual future buyers of these SBD/A-24 microfilms will benefit from my work.
First obstacle in creating such a drawing list is quite unusual: while most manufactures traced the digits of drawing numbers in ink, as the all remaining drawing lines, Douglas stamped them in the title block. The ink often spilled over the edges of the stamped digits, and now it is hard to read them from the microfilms photos. For example – look at the title block of this sample drawing:
When I altered the gray shades of this drawing, I was able to identify the first four digits (5063):
Fortunately, after this adjustment I discovered that they also stamped (most probably) the same number on the right margin. So here it is: 5063493. (You can also find a mirror image of this number on the right below: most probably it was stamped on the other side of this drawing). Of course, sometimes even these additional stamps on the margins are hardly readable: I frequently wondered whether a particular "splash" in place of a digit represents "4" or "1". In other cases it was difficult to tell if there is a "3" or "8", or "5", or even "0". Some help came from the observation that the numbers of these microfilm drawings are always in ascending sequence. Thus, if the unreadable digit in the drawing number "519456x" can be "3", "5", or "8", but the previous drawing is "5194560", and the next drawing is "5194565", then this last digit must be "3" (giving drawing no: "5194563").
Still there are cases in which I was unable to decipher the drawing number even after adjusting the grayscale, and there was a wide gap between the previous and the next drawing number:
The standard parts, like the one depicted in figure above, often occur in several variants (you could cut the depicted standard angle in a variety of lengths). In such a cases Douglas placed in the drawing an example of the full part number:
The prefix of this part number is the drawing number!
In case of unreadable dedicated part/assembly drawing numbers, Ester A. from AirCorps Library suggested the "last resort", indirect method. Usually the blueprint of a non-standard part contains a table named "NEXT ASSEMBLY" on the side of the main title block. It provides drawing numbers of the assemblies that use this part:
In the case from figure above this is a single assembly drawing: 3063922, which was used in the SBD-1, -2, and -3 models. Using this drawing number I found the corresponding blueprint:
Examining this assembly drawing, I found the sought detail and read its number. Of course, this method requires searchable list of the available drawing numbers, from which I would read that drawing 3063922 is in roll B, frame 1014. That's why in the first step I needed to create the drawing index.
It took me about 100 hours of work, but here it is:
Click here to download the index (*.xlsx file, 303kB).
Frankly speaking, for my purposes I do not need the details from roll A, which took about 25% of the total work time. But I decided to index all the rolls, just to provide a complete list for eventual other users.
Below you can see how this list looks like:
For each microfilm frame I note in this table not only the drawing number, but also the name copied interim from the drawing title block. (I preserved in these texts original caps and the grammar errors – for example: "PILOTS CHAIR"). Eventual unreadable digits in drawing numbers are marked as "?", and unreadable text fragments as "<…>".
It seems that in Douglas numbering system drawing numbers of standard parts should have "S-" prefixes. However, I found that these prefixes were often missing, or even manually written in drawings of certain parts that do not seem to be standard. Thus I decided to skip "S-" prefixes in the numbers placed in this index, because they could be misleading and make the eventual searches more difficult. Instead I marked each drawing of a standard part in the Comments column, basing on the presence of the "STANDARD PART" statement in its title block.
When a single drawing spans over two or more subsequent microfilm frames, I described it in the index table in following way:
Each line in the table represents single microfilm frame, thus drawing 5196835 is described by two subsequent lines, which differ by the drawing frame number in the Partial frame column (1, 2). In the first of these lines I placed the roll id of this drawing ("E128"). I did this just in case, because I do not think that I will use these ids. I placed drawing description (title) in the line that corresponds to the frame containing its title block. In this way the table contents is more readable. (You can instantly recognize for each drawing where it starts and ends).
In this list you can use Excel filtering feature, searching for drawings that contain certain phrase. When you click the auto-filter button in the right corner of Description column, and search for "BONDING" phrase, you will get following result:
If you did this search because you wanted to find the drawing of the fuselage bonding, in the result set you will see the last line of drawing 5196835 (the one that contains the description from its title block). You can read the roll symbol and the frame number from Roll and Frame # columns (roll: E, frame: 193). From the Dwg frm column you will learn that this is frame 2/2, thus you will also know that previous frame (192) from roll E contains the first part of this drawing.
Finally, figure below shows one of the most complex examples of a multi-part assembly drawing:
A very long drawing 5094762 (E138) was originally traced in two parts (1/2, 2/2). Each of these parts spans over 3 frames and has its own title block, thus I placed their labels in the corresponding index lines. What's more, this assembly is accompanied by additional BOM tables, depicted in the subsequent microfilm frames (6, 7, 8).
As you can see, this set has no index, which I could order earlier to examine its contents. When I finally received these microfilms in November 2019, I also discovered the meaning of enigmatic "(roll C" in the item description: it was truncated phrase "(roll C missing)"!
Well, this set was incomplete, but anyway I ordered its high-resolution scans from a local company that provides professional microfilm scanning services to museums. In January I received these data (4700 high-res, grayscale images in LZW-packed TIFF format – in total, about 300 GB). Finally I was able to scroll these blueprints. Frankly speaking, I was afraid that the most important drawings were lost with the missing roll C. Fortunately, during the initial review I noticed many detailed assembly blueprints among the scanned images. I even found a complete inboard profile of the SBD-5:
Here you can download the high-resolution version of this inboard profile (about 70MB).
The scanning company (Digital-Center, located near Poznan) did its job well, adapting the scanner resolution to the size of the depicted drawings. Scans of frames that contain large assemblies are usually 11 296 px wide and 7 874px high, which ensures that even the smallest references are readable. For example – see these four subsequent frames of the fuselage assembly drawing: 1, 2, 3, 4 (beware: size of each of these linked images is about 70MB).
There are even larger images in this result set: the biggest one is about 20 000px wide. The smaller drawings of various details are scanned at 7 672x5 682px.
Conclusions from the first review of this microfilm set are as follows:
- Roll A: blueprints of various small elements. Many of them (various angles, straps, bolts, pins, etc.) are standard Douglas parts, shared between many aircraft types. (As the angle from Figure 107‑5 – it was traced in 1936, before the SBD appeared on the designer desks);
- Roll B: blueprints of various SBD details - special bolts, pins, screws, various brackets, supports, forged parts, some minor assemblies (for example – arresting hook);
- Roll C: missing
- Roll D: assembly drawings
- Roll E: more detailed assemblies, some larger details
- Roll F: emaining elements (this is the shortest roll)
- Roll XA, XB: updated drawings, published a few months later. Most of the drawings are duplicates of those depicted in rolls A-F, but can differ in minor details. However, some of these drawings are new – most probably they are updates of the drawings from the missing roll C;
These blueprints describe SBD-4 and SBD-5 (which is OK – the SBD-4 is similar to SBD-3, and SBD-2, while SBD-5 is nearly identical to SBD-6). It seems that rolls A-F were made from September to October 1943, while their updates – rolls XA, XB – in January 1944. Because of the missing roll C, this documentation is not complete. In general I could not find the fuselage ordinates (I only found the wing ordinates). My first impression is that the missing roll C contains most drawings of wing ribs and at least half of the fuselage bulkheads. Fortunately, there are drawings of the tail bulkheads and the firewall on the other rolls.
For my project I need to organize these blueprints into a tree-like structure, with the largest assemblies in the root (as described in this post). However, after this initial review I could not determine the rules of the drawing numbering system used by Douglas. (I wanted to use them for quick grouping all parts belonging to the same subassembly). It could happen that in this Douglas factory the drawing numbers were assigned sequentially, just as the subsequent blueprints were ordered! It also seems that some of these drawings use original Northrop numbers, dating from the SBD predecessor: the BT-1 dive bomber.
To organize this documentation I have to start from the general assembly drawing and then step down to its subassemblies. For this purpose I need an index of these blueprints. Recreating such a thing is a monotonous task that will take some time, but I cannot see better option to fully explore contents of these microfilms. What's more, I think that once such a list is created, it can be also useful for the others. While NASM forbids publishing technical drawings from their microfilms by any means (except so-called "fair use", which I am stretching a little in this article), I still can publish such an index. Of course, I will also donate its copy to NASM. I hope that in this way the eventual future buyers of these SBD/A-24 microfilms will benefit from my work.
First obstacle in creating such a drawing list is quite unusual: while most manufactures traced the digits of drawing numbers in ink, as the all remaining drawing lines, Douglas stamped them in the title block. The ink often spilled over the edges of the stamped digits, and now it is hard to read them from the microfilms photos. For example – look at the title block of this sample drawing:
When I altered the gray shades of this drawing, I was able to identify the first four digits (5063):
Fortunately, after this adjustment I discovered that they also stamped (most probably) the same number on the right margin. So here it is: 5063493. (You can also find a mirror image of this number on the right below: most probably it was stamped on the other side of this drawing). Of course, sometimes even these additional stamps on the margins are hardly readable: I frequently wondered whether a particular "splash" in place of a digit represents "4" or "1". In other cases it was difficult to tell if there is a "3" or "8", or "5", or even "0". Some help came from the observation that the numbers of these microfilm drawings are always in ascending sequence. Thus, if the unreadable digit in the drawing number "519456x" can be "3", "5", or "8", but the previous drawing is "5194560", and the next drawing is "5194565", then this last digit must be "3" (giving drawing no: "5194563").
Still there are cases in which I was unable to decipher the drawing number even after adjusting the grayscale, and there was a wide gap between the previous and the next drawing number:
The standard parts, like the one depicted in figure above, often occur in several variants (you could cut the depicted standard angle in a variety of lengths). In such a cases Douglas placed in the drawing an example of the full part number:
The prefix of this part number is the drawing number!
In case of unreadable dedicated part/assembly drawing numbers, Ester A. from AirCorps Library suggested the "last resort", indirect method. Usually the blueprint of a non-standard part contains a table named "NEXT ASSEMBLY" on the side of the main title block. It provides drawing numbers of the assemblies that use this part:
In the case from figure above this is a single assembly drawing: 3063922, which was used in the SBD-1, -2, and -3 models. Using this drawing number I found the corresponding blueprint:
Examining this assembly drawing, I found the sought detail and read its number. Of course, this method requires searchable list of the available drawing numbers, from which I would read that drawing 3063922 is in roll B, frame 1014. That's why in the first step I needed to create the drawing index.
It took me about 100 hours of work, but here it is:
Click here to download the index (*.xlsx file, 303kB).
Frankly speaking, for my purposes I do not need the details from roll A, which took about 25% of the total work time. But I decided to index all the rolls, just to provide a complete list for eventual other users.
Below you can see how this list looks like:
For each microfilm frame I note in this table not only the drawing number, but also the name copied interim from the drawing title block. (I preserved in these texts original caps and the grammar errors – for example: "PILOTS CHAIR"). Eventual unreadable digits in drawing numbers are marked as "?", and unreadable text fragments as "<…>".
It seems that in Douglas numbering system drawing numbers of standard parts should have "S-" prefixes. However, I found that these prefixes were often missing, or even manually written in drawings of certain parts that do not seem to be standard. Thus I decided to skip "S-" prefixes in the numbers placed in this index, because they could be misleading and make the eventual searches more difficult. Instead I marked each drawing of a standard part in the Comments column, basing on the presence of the "STANDARD PART" statement in its title block.
When a single drawing spans over two or more subsequent microfilm frames, I described it in the index table in following way:
Each line in the table represents single microfilm frame, thus drawing 5196835 is described by two subsequent lines, which differ by the drawing frame number in the Partial frame column (1, 2). In the first of these lines I placed the roll id of this drawing ("E128"). I did this just in case, because I do not think that I will use these ids. I placed drawing description (title) in the line that corresponds to the frame containing its title block. In this way the table contents is more readable. (You can instantly recognize for each drawing where it starts and ends).
In this list you can use Excel filtering feature, searching for drawings that contain certain phrase. When you click the auto-filter button in the right corner of Description column, and search for "BONDING" phrase, you will get following result:
If you did this search because you wanted to find the drawing of the fuselage bonding, in the result set you will see the last line of drawing 5196835 (the one that contains the description from its title block). You can read the roll symbol and the frame number from Roll and Frame # columns (roll: E, frame: 193). From the Dwg frm column you will learn that this is frame 2/2, thus you will also know that previous frame (192) from roll E contains the first part of this drawing.
Finally, figure below shows one of the most complex examples of a multi-part assembly drawing:
A very long drawing 5094762 (E138) was originally traced in two parts (1/2, 2/2). Each of these parts spans over 3 frames and has its own title block, thus I placed their labels in the corresponding index lines. What's more, this assembly is accompanied by additional BOM tables, depicted in the subsequent microfilm frames (6, 7, 8).
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VALENGO
Senior Airman
Hi, Witold, just one question, how will be used all this stuff?. I mean, your 3D model is almost (completely?) finished and the attention you putted on details is insane. And is known that reviewing something is usually harder than creating. In an absolutely smaller scale, when I start any humble 3D project, once I set the plain views I don't change anything cause I know that there will be some sort of butterfly effect on the mesh. Are you intended to review the whole model using Gb's of drawings?
Congrats, incredible job.
Congrats, incredible job.
- Thread starter
- #396
Witold Jaworski
Airman 1st Class
Thank you for this question!
Indeed, most of the 3D modelers use the classic "waterfall" workflow you have described.
However, I am making these models just for myself, thus I have time to improve them after a new material emerges (this is one of the advantages of the 3D modelling). That's why I am building my models with the "always be ready to update" memento in mind. (A "spiral" workflow). For this purpose I use relatively simple meshes and plenty of dynamic modifiers, and recreate all skin details (including holes!) using easy to modify textures based on the vector (SVG) drawings. Many year ago I studied the mathematical rules of subdivision surfaces which are used in Blender for smoothing meshes. Now I feel at ease with their modifications (I can control them, and I know their "behavior" and limitations) and I use Subdivision modifiers in most places. For me, retaining the full control over my model is critical, and I test it from occasion to occasion - for example, on upgrading this project file to the new major Blender version (from 2.7 to 2.8). (In fact, I am a professional programmer, so I treat each my model like a large chunk of code: it has to be manageable and updatable
). I think that this is one of the factors that makes my modelling so slow, comparing to the other authors.
In the middle of 2019 I stopped this project waiting for these original blueprints. (I was not sure if I would get them at all).
Now I will finish upgrading this model to Blender 2.8 (its collections are much better for organizing model structure). In parallel I will organize the key (assembly) NASM blueprints into hierarchical structure. Then I will update this model part after part, using this original documentation. In spite of these 300GB, the NASM package still lacks many drawings: for example - today I know for sure that half of the fuselage bulkheads is missing, I am afraid that worse situation with the wing ribs, but fortunately they are less important. I think that I will start with updating the wing, then the tail plane, and finally the fuselage.
On the other hand - it will be quite interesting to discover in this way, how wide is the error range of my photo-matching methods, presented earlier in this thread...
Indeed, most of the 3D modelers use the classic "waterfall" workflow you have described.
However, I am making these models just for myself, thus I have time to improve them after a new material emerges (this is one of the advantages of the 3D modelling). That's why I am building my models with the "always be ready to update" memento in mind. (A "spiral" workflow). For this purpose I use relatively simple meshes and plenty of dynamic modifiers, and recreate all skin details (including holes!) using easy to modify textures based on the vector (SVG) drawings. Many year ago I studied the mathematical rules of subdivision surfaces which are used in Blender for smoothing meshes. Now I feel at ease with their modifications (I can control them, and I know their "behavior" and limitations) and I use Subdivision modifiers in most places. For me, retaining the full control over my model is critical, and I test it from occasion to occasion - for example, on upgrading this project file to the new major Blender version (from 2.7 to 2.8). (In fact, I am a professional programmer, so I treat each my model like a large chunk of code: it has to be manageable and updatable
). I think that this is one of the factors that makes my modelling so slow, comparing to the other authors.In the middle of 2019 I stopped this project waiting for these original blueprints. (I was not sure if I would get them at all).
Now I will finish upgrading this model to Blender 2.8 (its collections are much better for organizing model structure). In parallel I will organize the key (assembly) NASM blueprints into hierarchical structure. Then I will update this model part after part, using this original documentation. In spite of these 300GB, the NASM package still lacks many drawings: for example - today I know for sure that half of the fuselage bulkheads is missing, I am afraid that worse situation with the wing ribs, but fortunately they are less important. I think that I will start with updating the wing, then the tail plane, and finally the fuselage.
On the other hand - it will be quite interesting to discover in this way, how wide is the error range of my photo-matching methods, presented earlier in this thread...
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VALENGO
Senior Airman
Very clear and interesting. I am a very basic modeller, that's why I tend to freeze the mesh smoothing when I consider it ready. Thanks for your reply and keep it coming!!
Great work so far!
- Thread starter
- #399
Witold Jaworski
Airman 1st Class
In general, the set of 7 SBD/A-24 reels from NASM contains 3308 unique microfilm frames, belonging to 3022 drawings. On reels "XA" and "XB" you can usually find updated copies of the previous reels ("A", "B",.. "F"). However, 350 frames from "XA" and "XB" are unique – most probably this is a part of the missing roll "C". Duplicates from these "X*" reels are also useful, when a drawing from one of the previous reels is unreadable.
I chose about 1000 frames (mostly assembly drawings) from this microfilm set, and organized them into a tree-like structure as in figure below:
To preserve disk space, I placed in these folders shortcuts to files located in the original directories (These original directories correspond to microfilm reels: "A", "B", …, "XB"). I practiced that when I click such a link, it opens the image in Photo Viewer, as if it was the original file.
I think that Douglas did not use any sophistical drawing numeration (at least in this project). The SBD/A-24 drawing numbers seem to be assigned as they were ordered: for example, drawing numbers of subsequent wing bulkheads belong to number series that begins with: 206*, 209*, 212*, 406*, 409*, without any visible order. Maybe this is due the fact that part of these drawings came directly from the Northrop Co, without any renumbering? (You can still find "Northrop Aviation Division" name in the title blocks of some standard parts from this microfilm set).
The documentation from NASM microfilm is missing many important details – I suppose that they were on the lost reel "C". For example, figure below shows the identified and missing wing bulkheads:
Fortunately, reel "E" contains also wing geometry master diagram (ordinals), so I can use it for recreating shapes of these missing elements.
Fuselage structure also misses many bulkheads:
However, there is no master diagram for the fuselage. I will have to recreate its shape basing on the few reference dimensions placed in the identified assembly drawings. I have also found some contours of these missing bulkheads, drawn as additional information in various installation drawings. However, these blueprints are not as precise as you think – due to barrel distortions of the photo lens and draughtsman mistakes, I estimate their tolerance to 2-3% of the overall size. Unfortunately, there are no data about the wing fillet shape, especially its outer edge.
Several years ago I analyzed the SBD photos and concluded that SBD-5 (and -6) engines were mounted a few inches forward than in the previous Dauntless versions (SBD-1..-4). In this post I estimated this difference in length as 4 inches. Now I found the proof of this observation in the SBD-4 and SBD-5 engine mount dimensions (drawings 5055954 and 5159336):
The explicit dimension of SBD-4 engine mount (dwg no 5055954) specifies its length (distance from the firewall to the back faces of the engine mounting lugs) as 34.1875 (I switched original fractional dimensions to decimals). Similar dimension of the SBD-5 engine mount (dwg no 5159336) declares its length as 38.1875. Thus we have the 4" difference!
However, to determine the ultimate difference in the fuselage length (marked in the figure above with the question mark) I also have to determine the overall lengths of the elements in the front of the engine mount. Both versions (SBD-4 and SBD-5) used the same propeller (length: 21.75"). From the drawing of the SBD-5 NACA ring I can read the overall length of the entire engine cowling: 60.8125" (see figure above). Unfortunately, there is no such information in the SBD-4 drawings. I have to determine this dimension in an indirect way. Let's try it. The blueprints show that the length of the NACA cowling was identical in all versions (31.5"), as well as the distance from the R-1820 cylinders plane to the front of the NACA ring (14.3125"). (The NACA ring was attached to the mounting points on the R-1820 cylinder heads. These points were placed on the engine cylinders plane). Thus the potential source of the eventual further fuselage length differences is the distance from the back faces of the engine mounting lugs to the cylinders plane. From the SBD-5 blueprint I can calculate that it was 8.3125". This result is close to the dimension specified in the R-1820 installation drawing (8.24"):
However, this installation drawing describes the R-1820 G200 (also known as C9GC), which was used in the SBD-5 under military designation R-1820-60. (For more information on the Wright "Cyclone" engine variants see this post). The R-1820-52, used in the SBD-4 and earlier Dauntless versions, belonged to the earlier R-1820 G100 series (also known as C9GB). Crankcase of the G100 family significantly differs from the crankcase used in G200. This could also mean differences in the coaxial location of the engine mounting lugs.
The B dimension marked in this drawing is the piston bore. This is well-known parameter of this engine, specified in the manufacturer documentation as 6.125". I can estimate the sought distance A by comparing it to known B. The A/B ratio that I measured in a high-resolution copy of this drawing is 1.286 (+/- 0.8%). This means that A = 7.875" (+/- 0.063") – i.e. the same distance as in the R-1820 F. I assume this value for the R-1820-52as as the most probable distance from the mounting lugs to the cylinders plane.
Thus the overall difference in the SBD-5 and SBD-4 horizontal lengths comes from the difference in their engine mount lengths (4") and the difference in the distance from the mounting lugs to the cylinders plane between the R-1820-60 and -52 engines (8.3125– 7.875) = 0.4375". This result can be rounded to 4.44" (or expressed precisely as 4 and 7/16"). According Douglas general arrangement drawing, the overall length of the SBD-5 was 33' 1/4" (396.25"). Thus the overall length of the SBD-4 could be 32' 7 13/16" (391.81").
What about the earlier Dauntless variants: SBD-1, -2 and -3s? The eventual difference in their lengths and the SBD-4 length comes from the different propellers. (They used "Hamilton Standard Constant Speed", while the SBD-4 used newer "Hamilton Standard Hydromatic" propeller). In the NASM documentation I found a powerplant diagram (dwg no 5094793), which shows this older propeller variant and the contour of its spinner. Although the spinner shape a little bit different than in the archival photos, all other drawing elements seem quite precise. Using this picture I could make a more precise estimation of the few key dimensions:
In this blueprint (above) I identified vertical lines that mark the firewall and the engine mounting lugs planes, as well as the cylinders plane. I scaled the distance between firewall and engine mounting plane to the corresponding dimension (34.19"), then I read the B, C distances, and – just as additional check – the A distance. I received: B = 37.66", C = 42.38", A = 7.88" (which confirms the previous estimation: 7.875"). Thus the overall length of the SBD-1,-2, and -3 can be estimated as:
Similar (single) BuAer sheet from 6th August 1942 examined the SBD-3 and SBD-4. The horizontal length specified in this document (32' 8") agrees quite well with the length of the SBD-4. We can assume that in the sheet which examined both: the SBD-3 and SBD-4, BuAer engineers simply put the length of the latter (evidently they treated these two aircraft as a single variant).
I chose about 1000 frames (mostly assembly drawings) from this microfilm set, and organized them into a tree-like structure as in figure below:
To preserve disk space, I placed in these folders shortcuts to files located in the original directories (These original directories correspond to microfilm reels: "A", "B", …, "XB"). I practiced that when I click such a link, it opens the image in Photo Viewer, as if it was the original file.
I think that Douglas did not use any sophistical drawing numeration (at least in this project). The SBD/A-24 drawing numbers seem to be assigned as they were ordered: for example, drawing numbers of subsequent wing bulkheads belong to number series that begins with: 206*, 209*, 212*, 406*, 409*, without any visible order. Maybe this is due the fact that part of these drawings came directly from the Northrop Co, without any renumbering? (You can still find "Northrop Aviation Division" name in the title blocks of some standard parts from this microfilm set).
The documentation from NASM microfilm is missing many important details – I suppose that they were on the lost reel "C". For example, figure below shows the identified and missing wing bulkheads:
Fortunately, reel "E" contains also wing geometry master diagram (ordinals), so I can use it for recreating shapes of these missing elements.
Fuselage structure also misses many bulkheads:
However, there is no master diagram for the fuselage. I will have to recreate its shape basing on the few reference dimensions placed in the identified assembly drawings. I have also found some contours of these missing bulkheads, drawn as additional information in various installation drawings. However, these blueprints are not as precise as you think – due to barrel distortions of the photo lens and draughtsman mistakes, I estimate their tolerance to 2-3% of the overall size. Unfortunately, there are no data about the wing fillet shape, especially its outer edge.
Several years ago I analyzed the SBD photos and concluded that SBD-5 (and -6) engines were mounted a few inches forward than in the previous Dauntless versions (SBD-1..-4). In this post I estimated this difference in length as 4 inches. Now I found the proof of this observation in the SBD-4 and SBD-5 engine mount dimensions (drawings 5055954 and 5159336):
The explicit dimension of SBD-4 engine mount (dwg no 5055954) specifies its length (distance from the firewall to the back faces of the engine mounting lugs) as 34.1875 (I switched original fractional dimensions to decimals). Similar dimension of the SBD-5 engine mount (dwg no 5159336) declares its length as 38.1875. Thus we have the 4" difference!
However, to determine the ultimate difference in the fuselage length (marked in the figure above with the question mark) I also have to determine the overall lengths of the elements in the front of the engine mount. Both versions (SBD-4 and SBD-5) used the same propeller (length: 21.75"). From the drawing of the SBD-5 NACA ring I can read the overall length of the entire engine cowling: 60.8125" (see figure above). Unfortunately, there is no such information in the SBD-4 drawings. I have to determine this dimension in an indirect way. Let's try it. The blueprints show that the length of the NACA cowling was identical in all versions (31.5"), as well as the distance from the R-1820 cylinders plane to the front of the NACA ring (14.3125"). (The NACA ring was attached to the mounting points on the R-1820 cylinder heads. These points were placed on the engine cylinders plane). Thus the potential source of the eventual further fuselage length differences is the distance from the back faces of the engine mounting lugs to the cylinders plane. From the SBD-5 blueprint I can calculate that it was 8.3125". This result is close to the dimension specified in the R-1820 installation drawing (8.24"):
However, this installation drawing describes the R-1820 G200 (also known as C9GC), which was used in the SBD-5 under military designation R-1820-60. (For more information on the Wright "Cyclone" engine variants see this post). The R-1820-52, used in the SBD-4 and earlier Dauntless versions, belonged to the earlier R-1820 G100 series (also known as C9GB). Crankcase of the G100 family significantly differs from the crankcase used in G200. This could also mean differences in the coaxial location of the engine mounting lugs.
The B dimension marked in this drawing is the piston bore. This is well-known parameter of this engine, specified in the manufacturer documentation as 6.125". I can estimate the sought distance A by comparing it to known B. The A/B ratio that I measured in a high-resolution copy of this drawing is 1.286 (+/- 0.8%). This means that A = 7.875" (+/- 0.063") – i.e. the same distance as in the R-1820 F. I assume this value for the R-1820-52as as the most probable distance from the mounting lugs to the cylinders plane.
Thus the overall difference in the SBD-5 and SBD-4 horizontal lengths comes from the difference in their engine mount lengths (4") and the difference in the distance from the mounting lugs to the cylinders plane between the R-1820-60 and -52 engines (8.3125– 7.875) = 0.4375". This result can be rounded to 4.44" (or expressed precisely as 4 and 7/16"). According Douglas general arrangement drawing, the overall length of the SBD-5 was 33' 1/4" (396.25"). Thus the overall length of the SBD-4 could be 32' 7 13/16" (391.81").
What about the earlier Dauntless variants: SBD-1, -2 and -3s? The eventual difference in their lengths and the SBD-4 length comes from the different propellers. (They used "Hamilton Standard Constant Speed", while the SBD-4 used newer "Hamilton Standard Hydromatic" propeller). In the NASM documentation I found a powerplant diagram (dwg no 5094793), which shows this older propeller variant and the contour of its spinner. Although the spinner shape a little bit different than in the archival photos, all other drawing elements seem quite precise. Using this picture I could make a more precise estimation of the few key dimensions:
In this blueprint (above) I identified vertical lines that mark the firewall and the engine mounting lugs planes, as well as the cylinders plane. I scaled the distance between firewall and engine mounting plane to the corresponding dimension (34.19"), then I read the B, C distances, and – just as additional check – the A distance. I received: B = 37.66", C = 42.38", A = 7.88" (which confirms the previous estimation: 7.875"). Thus the overall length of the SBD-1,-2, and -3 can be estimated as:
- when the spinner was mounted: 32' 6.3" (+/- 0.3");
- without the spinner (the case often observed in the archival photos): 32' 1.5" (+/- 0.3");
The aircraft dimensions listed in these BuAer data sheets are rounded (up?) to full inches. For example: the wing span is listed as 41' 7", while the exact value in Douglas arrangement drawing is 41' 6.125" (41' 6 1/8").
Similar (single) BuAer sheet from 6th August 1942 examined the SBD-3 and SBD-4. The horizontal length specified in this document (32' 8") agrees quite well with the length of the SBD-4. We can assume that in the sheet which examined both: the SBD-3 and SBD-4, BuAer engineers simply put the length of the latter (evidently they treated these two aircraft as a single variant).
Many publications cite SBD-3 length as 32' 8". This is wrong value, coming from overinterpretation of the BuAer data sheet from August 1942.
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