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1/48 Scale Sabre Wings
What's the Angle?

by Jennings Heilig

 


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Introduction

 

When Hasegawa issued their beautiful series of 1/48 Sabres starting in the mid-1990s, modellers (including me) were overjoyed.

The old Monogram kit was good in its day, and the ESCI kits were fair, but we really needed a new technology Sabre family. At the time the kit first came out there was some banter on rec.models.scale about whether or not the wings had the correct sweep. I honestly don't recall what the outcome of those discussions was, but more was in store.

The recent appearance of the gorgeous Revell-Monogram 1/48 F-86D with its narrow chord slatted wing reignited the debate right here on HyperScale and some of the other modelling sites. Again, I don't recall the exact course of this debate, but I do recall that at least one review pronounced that the Dog Sabre's wings were correct in sweep and that Hasegawa's (and it's near clone Academy's) were not. As I recall it, the Hasegawa and Academy kits were alleged to have too little sweep, against the RM Dog's correct sweep.

Well, the Sabre being one of my favorite subjects, I finally decided the other day to sit down and straighten it out once and for all.

 

 

Sabre Wing Sweep

 

The Sabre's wing featured a 35 degree sweepback.

If you're not familiar with basic aerodynamic terminology, you could easily believe that neither kit is correct. Many people assume the sweep angle is measured along the leading edge of the wing. Actually, the sweep angle is (usually) measured along a theoretical line at 25% of the chord of the wing. So now you need to know what the chord is, right? Quite simply, a wing's chord is the distance from the leading edge to the trailing edge. If a wing is perfectly rectangular, then the chord is constant from root to tip. Most wings, like that of the Sabre, are tapered to some degree, thus the chord at the tip is narrower than the chord at the root. So we need to find the line which represents the average distance 25% of the way from the leading to the trailing edge to figure our Sabre's wing sweep angles.

In order to do that as accurately as possible, I got out some kit parts, some paper, and a sharp pencil, and set to work with my scanner, my trusty Power Mac G4, and Adobe Illustrator 8.0. My methodology may not be "scientific", but my experience with this sort of thing makes me believe that I'm certainly within a very close tolerance on measurements.

I used the panel line where the wingtip joins the wing as a vertical reference, since on the Sabre this panel line is parallel to the longitudinal axis (and thus the line of flight) of the airplane. It is this axis against which the wing sweep is measured. Both kit wings were drawn using the same method, the same piece of paper, the same scan, and were drawn at the same time to eliminate any errors introduced from differing scanning parameters, etc.

I aligned both kit left hand upper wing halves on a vertical reference line, carefully aligning the common panel line on both to my reference. I taped the wing parts down and using a sharp drafting pencil, precisely traced the leading and trailing edges onto the paper. I was careful to keep my pencil very sharp and to make the line as precisely even with the edges of the plastic as possible.

Then I scanned this piece of paper in at 720dpi in 'line art' mode at 100% of actual size. This provided me with a black & white TIFF image in very high resolution and at exactly the same size as the original tracing.

This TIFF was then imported into Adobe Illustrator. I laid down lines along the leading and trailing edges of the tracing, being sure to have my vertical reference line exactly vertical on my Illustrator document. I then used Illustrator's "blend" option, set to blend the leading and trailing edge lines in three equal steps. This gave me precisely evenly spaced lines at 25%, 50%, and 75% of the chord along the entire span. Since the 50% and 75% lines were not needed, I discarded them.

Using Illustrator's measurement tool, I then measured the precise angle of each of my 25% chord lines. The results are as you see. The tool caculates angles out to .001 degree, but since my eye can't discern a thousandth of a degree, I rounded to the nearest tenth.

 

 

 

Now, that should pretty well wrap it up, right? Well, not so fast.

The Hasegawa and Academy wings represent the hard edged, extended chord '6-3' wing of the F-86F. If you understand that the '6-3' refers to the amount added to the leading edge; 6 inches at the root, and 3 inches at the tip, then you can see that this modification will affect the sweepback of the wing if we measure our 25% chord based on this unevenly extended leading edge. Remember that the 35 degree sweep of the wing was calculated on the original F-86 wing, long before the '6-3' leading edge extension had been dreamed up.

So back to Illustrator.

I took the tracing of the Hasegawa wing and measured (down to 3 decimal places of accuracy) 6 scale inches back from the leading edge at the root, and 3 scale inches back at the tip (along the vertical reference line). When I then went back and had Illustrator calculate the 25% chord line from these new lines, bango! It measured out at exactly 34.95 degrees, which is close enough to 35 in my book, and I'm pretty anal-retentive!

 

 

 

Conclusion

 

So, who's right and who's wrong?

It appears, even factoring in a small amount of error in the abovementioned methodology, that Hasegawa and Academy got it bang on the money, and that Revell Monogram... well, they didn't. The Dog Sabre, gorgeous kit that it is, has a wing that's swept more than 3 degrees beyond what it should have.

All of the above aside, all of the kits certainly look like Sabres. Unless you had a Hasegawa and a Revell-Monogram sitting side by side and could view them from directly above, against a gridded surface, and were really anal about it, I doubt that you'd spot the difference.

I'm completely open to being shown to be all wet on this, but I, for one, am now satisfied that the Hasegawa and Academy F-86 kits are the most accurate F-86F kits, and that the Revell-Monogram F-86D is the most accurate Dog Sabre out there, despite its slightly too-swept wings.

Let us go forth and build!

 

 


Text and Images Copyright 2003 by Jennings Heilig
Page Created 25 March, 2003
Last updated 25 March, 2003

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