SR-71 Blackbird (oz6111)

 

SR-71 Blackbird (oz6111) by Parker Leung from RCMplans 2002 - plan thumbnail

About this Plan

SR-71 Blackbird. Sport scale design for .40 to .46 power. This is a modern CAD-redrawn plan.

Quote: "After my previous article on the F-117A (oz7403) stealth fighter was published in the February '97 issue, I received quite a lot of feedback from readers expressing their interest in the SR-71, the once highly secret airplane with several world records. Unfortunately, there is no commercial kit of this aircraft available for sport fliers.

I had this project on the drawing board for several years, but it was a difficult job to simplify the construction and to ensure the performance. I saw the ducted fan version; it flew great, but obviously was not suitable for most sport fliers. I was also told that it was unstable at high angles of attack because the main wing is blanked by the wake from the fuselage.

In order to study the behavior of this unique aircraft, I built several hand launched models; the test flights were carried out in my 10' x 10' x 15' wind tunnel. (Just kidding, it's my room that allows me to fly during the cold Canadian winter.) I discovered an even worse problem. It rocked side to side at high AOA (angle of attack), then sank like a fallen leaf. I believe it is the conflict between the fuselage (lifting body) and the wing. At a high AOA, the wing stalls first while the fuselage continues to lift. Thus, the nose keeps going up and reaches an even higher A0A. This is opposite to a canard design in which the foreplane stalls first and lets the nose drop to recover by itself.

These problems may not affect the full-scale aircraft. but it is really a challenge for a scale model. Furthermore, I haven't come across any suggestions nor solutions from the books. Well, one of the advantages to designing a sport model is the flexibility to do whatever I want. Therefore, I shortened the nose and the width of the fuselage as well, and the nose cone was slightly dropped, the cross section is pretty true to scale.

All these modifications improve the model's performance. Another bonus is that the model is small enough to store in my trunk. Since 1 am not interested in high speed, the wing is relatively thick so as to enhance better handling during take-off and landing. It is not practical to locate the engine at the nose or the tail because it might cause severe balance problems. Instead, the engine has been installed at the mid-wing position, and the fuel tank is close to CG point. By the way, I would like to give the credit to a famous designer, Mr. Laddie Mikulasko. He has designed a lot of unique models with a mid-engine configuration; most of them were featured in magazines.

Construction. Due to the unique appearance and flight performance, the model is not recommended for beginners. Experienced builders are suggested to study the plans and this article thoroughly before they begin..."

Quote: "Here's the Jul 2002 SR-71 plans. I traced the original file in CAD so that I could use my CNC router to make a short kit. I build one and it flies very well, except hard to see!"

Supplementary file notes

Article pages, text and pics.

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SR-71 Blackbird (oz6111) by Parker Leung from RCMplans 2002 - model pic

Datafile:

SR-71 Blackbird (oz6111) by Parker Leung from RCMplans 2002 - pic 003.jpg
003.jpg

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User comments

Page 1 of the drawing is not to scale. The 6 inch ruler in the lower right hand corner only measures roughly 5-1/2 inches.
JR - 18/07/2019
I think you're right. But this is a vector PDF file and those are outside my abilities. I'll only mess it up if I try and re-scale it. Anyone got a fix for this, or a bitmap version of the same plan?
SteveWMD - 18/07/2019
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* Credit field

The Credit field in the Outerzone database is designed to recognise and credit the hard work done in scanning and digitally cleaning these vintage and old timer model aircraft plans to get them into a usable format. Currently, it is also used to credit people simply for uploading the plan to a forum on the internet. Which is not quite the same thing. This will change soon. Probably.

Scaling

This model plan (like all plans on Outerzone) is supposedly scaled correctly and supposedly will print out nicely at the right size. But that doesn't always happen. If you are about to start building a model plane using this free plan, you are strongly advised to check the scaling very, very carefully before cutting any balsa wood.

 

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