Friday, October 18, 2013

Rigid Construction for a Simple Rubber Airplane

NEWS FLASH Kit Available Again New Link

http://blueridgemodels.net/



For me learning something new when taking on a new project is always a thrill.  I have been reading about a simple rubber powered free flight model known as the Blue Ridge Special that uses a more advanced construction technique that creates a very rigid structure.  One person had referred to this as “Union Jack” construction, my search for this brought up mainly information on the official flag of the UK which is known by the same term. The angled lines in the flag do have the look of a pattern of diagonal and crossing horizontal lines like you see in the wing structure.  Diagonal ribs connected to a spar through the wing make for a wing that is very rigid. Tail surfaces also have diagonal bracing.






The price for the kit of the Blue Ridge Special is reasonable but it appears that it is not available right now as a note on the Pal Model Products website indicates they are busy working on products.  I was able to find plans that were similar to the kit and used hobby shop balsa so my plane might be slightly heavier than the kit, weight was 11.32 grams without rubber.


Wing Structure

If you have built other simple rubber models of this size you might be wondering if more advanced construction technique is really necessary. This type of construction is normally seen in higher-powered glow or electric free flight models that scream skyward which can cause wings to flutter.  What I have noticed is that my plane as well as the Blue Ridge Special planes other people have built flew perfect from the start with no trim adjustments needed.  I have to believe that with this method of construction it is easier to build an airframe with no warps.




The airplane has only been out for one flying session so far but it flew very well. Most of the flights were with 3/32” rubber using a 6” diameter propeller.  It was rather windy and I sure did not want lose the new plane so I did not use anywhere near maximum winds in the rubber.  The airplane climbed but not steep, I tried 1/8” rubber with even fewer turns and the climb was steeper.  I am really anxious to try more winds on a calm day and see what this airplane can do.




Bill Kuhl

http://ideas-inspire.com

Additional Resources

Blue Ridge Models Website 

Thread on Hip Pocket Forum About Blue Ridge Special



5 comments:

  1. It is a great idea to have a prototype of the original plane to understand the mechanism of aerodynamics completely.

    Thanks
    Sanola Jerry

    Plos Constructions

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  2. I notice that the kit is still not available from Pal Model Products.
    What alternative set of plans did you find to build this and where might they be found?

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  3. Jeff email me at scienceguy33@gmail.com

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  4. I have a Blue Ridge Special, bought and built many years ago, back when Blue Ridge Models was located in Ashiville, NC. It weighs 11.0 grams without rubber motor, and this after I added a wing saddle to keep the wing from rocking on the fuselage. Does the "Union Jack" construction add to or detract from the aerodynamics (?) - do not know, but I can say for sure that it makes the wing rigid and warp resistant.

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    Replies
    1. Richard I was wondering the same thing. One has to wonder if it would cause more drag over the wing. But when the wing is slightly twisting in flight maybe that causes more drag. It does stay in trim much better than less rigid models.

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