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Saturday, January 13, 2018

Iconic 1950's British Modeller P. E. Norman's Fokker DR 1


Stories abound of PE at Epsom Downs in the 1950's, generally shirtless, with models performing wild aerobatics as he trimmed and tamed them. He took great joy in having several of his scale free-flight models all in the air at once!

To call P.E. Norman multi-talented doesn't do him justice. Aside from being recognized, at least circa 1962, as Britain's most accomplished aeromodeller, he made and played professional violins (aka luthier), wa a wood carver, a silver smith, a sculptor, and even an artist who painted the image used on the cover of this February 1962 American Modeler. P.E. is credited with designing, building, and flying the first pendulum-operated-elevator free flight model and has designed and built many ducted fan scale jet models (long before commercial ducted fan units were available).


My DR-1 was scratch built in the mid 1960's from Aero-Modeler  plans designed for free flight by the famous British Aero Modeler P.E. Norman;  it was controlled by using a unique pendulum arrangement to stabilize the model in the pitch mode. The design featured a flyaway wing components to limit damage in a rough landing; of which I am sure there were many. This particular model retained many of these damage tolerant features as well as adding 3 channel radio control.
Much later it was upgraded by adding ailerons, miniature servos, 2.4GH radio and an OS Type 1 Wankel engine. Future modifications include the addition of an autopilot unit, to improve stability.



Plans for this design are available to this day.
We modified these plans considerably when we built our model in the early 1960's, adding just a hint of dihedral to the wing panels but we retained the originals sturdy break-away features.

Tuesday, November 14, 2017

120 Size Zero Rises Again Like a Phoenix After a Devastating Crash


71" WS, 13.2 lbs, Enya 120






This decision proved to be a very big mistake. Just before the landing on the downwind leg something caused the big model to enter a nose down spin dive into the ground. 

The crash smasher all the plywood frames into many pieces leaving the fiberglass fuselage resembling a limp and gutted form. There were several buckles and creases and numerous cases where the gel-coat was cracked or missing. I was of a mind to scrap this war-bird, but one of my internet buddies urged me to repair to flying condition, arguing that the zero was one of his favorite flying models. After a reasonable cooling off period I had another look at the wreckage and began considering repair options. The wing was still in one piece and except for a 3/4 inch gap at the trailing edge where the center-line joint partially separated. Additionally there was some leading edge crushing at the fuselage intersection area. The trailing edge separation issue was dealt with when epoxy glue was squeezed into the crack and a cargo strap, hooked into the aileron cutouts was used to pull the wing halves together. A cuff of fiberglass at the center-line joint added another level of safety over the stock ARF condition. The leading edge crushing was fixed by filling the low areas with expanding foam, bringing the area back to profile by carving and sanding away the excess material. The areas were finished by over laying the surface with a single layer of epoxy filled fiberglass. Since the paint and surface finish was already in bad condition from hard use before the crash now after it was so bad that it was clear that the whole model would need to be refinished. With that decision we began the search for an alternative color scheme. The dark green color was always a problem with disability at low altitude when the model was back-grounded against the trees and other vegetation it was very hard to see. With that in mind we settled on a light grey Navy color scheme with as much bright trim as we could find.
     








  1.  Wing weight is 2.17 Kg.

The decision was made to experiment with using latex house paint to cover up the existing finish which had not been found to be hot glow fuel proof and was softened or missing in several areas that were exposed to engine exhaust.        

The grey color was achieved by mixing white with black, ever mindful of the fact that there would be no going back; very small amounts of black were added and tested until we were happy with the result.  
 The yellow and red trim was added by apply strips of Mono-Coat covering material to the fiberglass structure
During the repair process we took the time to examine the rudder linkage which is rather unconventional with several locations of backlash and questionable geometry. The axis of movement if the torque rod did not coincide exactly with the rudder's hinge line. The results were a rather vague and weak rudder incapable of reacting the aerodynamic forces upon it at large pilot inputs. 

At this point we concluded that the model was flown in the past effectively as a elevator and aileron system with little or no rudder influence; meaning that there was no chance of recovering from a spin if one were to happen.

  



To correct the weak rudder problem control horns and pull-pull cables were installed to connect the rudder to the rudder servo.

 First the torque rod was cut off with a dremel tool and removed then the fin was filled with expanding foam to anchor the new rudder hinges and stiffen the vertical fin
Right and left controls installed at the base of the rudder.
Pull-pull cables threaded through the fuselage connecting the rudder control horns to the rudder servo.
The cables are attached to inner Ny-Rod tubes at the forward ends, this is done to simplify the adjustment of length of the Pull-pull members. 




Dry weight of the repaired plane is 7.00 Kg or 15.43 pounds.
71"WS 15 lbs, Enya 120



We have a bad feeling that we may have just stumbled across the real cause of the mystery crash.  While setting up the controls we accidentally plugged the left hand wing servo into the receiver's aileron channel and the right one into the auxiliary channel and low and behold we had spoilerons instead of the flaperons that we were expecting. Could I have made the same mistake on the day of the crash?


This video clip demonstrates that when the aileron servo leads are switched and the right hand aileron servo lead is plugged into the auxiliary receiver port and the left one is plugged into the flap port you get very different  effects; spoilers instead of flaps and spoilers are something one doesn't want when setting up for a landing.


After working on this video I have a couple of more probable causes to add to the list:
Weather may have been a contribution factor as there were rail squalls in the area and the video shows her vanishing into a dark cloud at the moment of the tuck nose-down;
we may have sent her into the air with SPOIL-ERONS activated, we have learned that a simple mix-up with the servo wires causes this condition when employing the FLAP-ERONS configuration with the DX6 radio..

Wednesday, September 6, 2017

Huge Lancaster Dambuster Bomber by Chris Malcomnson







Published on 6 Sep 2017 134 inch wing span, Lancaster Bomber. Each engine nacelle is fitted with its own radio receiver, battery, electronic speed controller and brush-less motor.