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(Another) P51-D swappable design/build log

With the weather getting colder where I live I'm starting to stack my design and build projects. I have an idea for a way to finish and detail a dollar store foam warbird. However it doesn't lend itself to David's awesome spitfire. So I'm taking on designing a P51-D swappable airframe. There are several great P51 designs on here but I've always wanted an accurate laminar wing profile that is very noticeable in the 'D' Mustangs. One of the other drivers for me to design a Mustang airframe is the very distinctive war paint that the Mustangs really demonstrate. Everything from their tail colors, nose colors/patterns, and invasion stripes really tell a complex story for each mustang and I hope to share some of that history over the course of this design/build log.

To start with, here's some inspirational Mustang images via Google:




And "Willit Run?" from my visit to the Smithsonian Air and Space Museum this year
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Some great photo galleries of Mustangs.

So to start with I'm taking inspiration from both David's spitfire design as well as his FT Racer (Ripslinger) design. In the first round I pulled in reference to SketchUp like I usually do and started blocking in the major forms. It's interesting that the horizontal stabilizer is set clear forward from the vertical stabilizer. This is in major contrast to aircraft like the Vought Corsair who's Horiz. Stab. is set far behind the Vert. Stab.
I'm using the undercamber wingtip design and I'd like to keep the bottom smooth and enclosed. I may design the lower panel under the nose to be able to fold down to allow the insertion and connection of the power pod with some latching system to secure it for flight.

The ridge you see running along the top is not going to be in the final design, I'm using it as a reference pattern to try and get the correct profile. I'll update as I make progress.


Posted a thousand or more times
Man, I love your work. My hope is to eventually be half as good as you are with Sketchup. Thanks for sharing this process. Great design choice.
Thanks Jaxx! :D
I made some progress over lunch today. Worked out the turtle deck and formers for the fore and aft sections.












Next I need to design in the wing spar and figure out servo/control horn placement and if I want to put ailerons on or not.


Dedicated foam bender
We're not worthy! We're not worthy!
That is pretty cool, Jason. I really need to play around some with Sketch-up.
Thats nuts!
The plane looks awesome!
I always wondered, how do you go from a design like this to a flat layout ready to cut into foam board?
Thanks guys! :D
I always wondered, how do you go from a design like this to a flat layout ready to cut into foam board?
The first part is to unwrap it to a flat form. I started showing the first part of that process in Tutorial #7. I'll also be documenting the process on this specific model in this thread as I go along. I've got some time off so I'll likely be updating alot. If the prototype handles well I'll pull everything into a tidy article with a set of build plans and video at the end. If it doesn't... there will be flames and much stomping in anger.
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Junior Member
Hey Jason! Thanks and great job on the Sketchup Tutorials. Used it to design and build a scratch 3D plane. Thinking about an Avro Lancaster bomber next.
More refinements. Caught a design flaw in my wing root. I'm trying to document the process for anyone into using SketchUp so pardon the mass of screen shots and type-o's in my annotations, I'm documenting as I design.















If you pull this one off, I"m in. I put the challenge to Jay at frcfomies since he did the Mozzie. I don't know if he will accept the challenge or not, but if you can come up with a workable design, I"m all over it. WJ.


I'm a care bear...Really?
I really wish I could do that. I must say playing with sketch up yesterday I have an all new appreciation for josh and them when they design planes
I feel like I'm forgetting some part of this but I guess I'll find that out what that is as I'm now starting to actually cut templates and foam.

I used the flattery .SVG export to create the vector file that I then loaded into Inkscape to be cleaned up and prepped for printing

I made sure to set the units of the document to be inches rather than pixels.

Some of the shapes are grouped and have odd fills so I made sure to ungroup everything so I could clean up the plans.

Some areas needed to be tessellated to triangles in order for sketchup to be able to create a surface (see the post on the turtle deck) and those extra lines carry over in the export. I went in and deleted any lines that I wouldn't need for cutting, folding or scoring.

Here is the plan cleaned up

In Inkscape I set the document size to be 20inx30in, that of the DTFB and then went about arranging the parts to get a sense of how much foam would be needed for all the pieces. I also drew in a 6 inch test scale so that I could verify the printed plans will be the correct size.

From here I exported a high resolution .PNG file at 20"x30". In the past I've used some commercial PDF tools to tile my plans but for this project I'm only using free/open source tools that everyone would be able to download and use. In this case I'm using PosterRazor to slice up the large image of the plans into a PDF that will tile across normal 8.5x11 printer paper.

Here I've played around with the "Size in pages" settings decimal points to get the scale to be as close to 100% as I can. From there PosterRazor creates a multipage PDF file.

I then open the PDF and print only the page that has some of the 6" scale and measure it to see if it's printed 'inches' are actually inches.
That is just about dead on. So now I'm going to print out the rest of the pages, cut them out, and start cutting foam!
There are all kinds of little tweaks I'm discovering and documenting but overall it seems to be coming together.

  • Spar doesn't seem to fit right but that may be due to a cutting error
  • Going to change the tail assembly to allow the horiz stab to slide into the virt stab from the side
  • The V in the Horiz stab needs to be larger as well as the clearance arch in the virt stab
  • I'll need to adjust the wing root holes in the fuse to fit, to sharp of a leading point
  • I'm going to redo how the belly coverage works and add notches
  • The cockpit formers will need to have an angle support added to hold them in place

Sure wish I had a laser cutter.

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