Formers/bulkheads for Fiddlers Green models

[k5083]

On a couple of threads recently, some folks have expressed regret that the Fiddlers Green models don't come with formers and bulkheads to make them more rigid and accurate. I usually create a set of formers and ribs for my better FG builds, and it isn't that difficult. Here is a quick how-to. I'm illustrating it with a partial build of one of the early simple FG kits, the SBD Dauntless, but it will work with any FG or other model that has no formers, or not enough, or inaccurate.

You'll need two pieces of software, both of which you can get free. One is any program that will extract the image in the Acrobat PDF files supplied by FG to a graphic file. Or, you could just print and scan the model. I generally convert in Photoshop Elements but there are freeware options. The other is a program that allows you to trace a series of connected line segments over an image and measure their total length. I use ImageJ, a public domain program developed by the US government's National Institute of Health. ImageJ.

First you need to find yourself a set of drawings of the subject aircraft that include cross sections. A lot of reference books contain these, and a lot of web sites have compilations of them. Query the aircraft type in goodle or bing image search, especially with another word like "drawing" or "plans", and you're likely to find something. If you can't, a good 3-view drawing can give you the height and width, and you can often rough out the shape well enough. For pressurized types, from the B-29 to modern airlines, a simple circle will get you a long way.

Anyway the SBD is a popular type and I had no trouble finding several sources for 3-views. Here's the one I went with, from a book by Kagero.

[k5083]

Next study the model and decide how many formers you should use and where you want them. A good drawing like the one above will furnish a lot more than you need. I decided to go with formers C, E, J and N for my Dauntless fuselage. Cut each former out of the file and paste into a new graphic file. You will likely have to simplify some of the formers to project the basic curve of the cross section through protrusions like wings and fairings that are integral with the fuselage on the real thing, but are added on to the basic shape on the model. So for sections H and E below, I've clipped out the wings, canopy and wing-fuselage fillet as shown by the red lines.

[k5083]

You can do the same thing to make ribs for the wings. Some aircraft drawings include airfoil cross-sections and some don't. If they don't, you can often look up what type of airfoil the plane used from reference books or from a database like The Incomplete Guide to Airfoil Usage. That database indicates that the Dauntless used the NACA 2415 airfoil. Once you know that, a google image search for NACA 2415 quickly pulls up many images of this airfoil. Find a nice clean one and save it. This is something that I do even with many non-FG models, because I like my wings to have an accurate curvature.

[k5083]

Next you need to do some measuring with ImageJ or a similar program. First load the image you've extracted of the model itself. Trace a line around the fuselage parts where the edge of each former will be. In the example below, I'm doing the rear edge of the forward part of the fuselage, indicated by the yellow line with the points on it. Having drawn the line, I asked the program how long it is, and the box in the corner says 313.885 pixels. The physical length of this line will be that value divided by the dots per inch at which the model is printed (which the program will compute for you if you want), and if this line matches the perimeter of the former that goes there, it should fit.

So then you similarly measure the perimeters of the bulkhead images. Here I've done bulkhead J, which I'll be gluing to that position on the fuselage, and it comes to 391.341 pixels. This means that whatever dpi resolution I print the model at, I'll need to print this former at 391.341/313.885=124.7 times that resolution (i.e., reducing it to 80.2% scale) for it to fit.

You'll have to do this for each former individually because most paper models, and certainly FGs, are not accurate enough for you to get away with scaling each former to the same degree.

Do the same thing with the airfoils, pretending the wing is a tube and measuring across the chord, top and bottom, to get the necessary circumference for the airfoil. Scale the same airfoil to fit as many positions as you want across the wing.

You could simply print each rescaled former and rib individually, but I generally do a little extra work and combine the rescaled individual parts into one image. So the third pic below is the complete set of formers and ribs scaled for the FG Dauntless, which I can print at whatever resolution I need to match whatever size I print the model.

[k5083]

Now your parts are done, essentially you've got a model with formers and you can build it like any other. Here is the forward part of my SBD fuselage. It has formers C, E and J at the appropriate positions, plus I converted the engine faceplate into a fourth former and glued it inside the fuselage at the front.

[Alcides]

Great thread k5083!! A useful, very informative and well written thread about this subject. Thanks a lot.

[John Wagenseil]

Great write up.
Your method of creating formers for airplanes should carry over to creating bulkheads for ship models.