Prophet (oz3120)

 

Prophet (oz3120) by Dave Robelen from American Modeler 1967 - plan thumbnail

About this Plan

Prophet. Radio control aerobatic model. For Cox Tee Dee .020 power and aileron/elevator dual propo RC. Area 127 sq in. Weight 10 oz.

Quote: "This .02-sized craft that can be flown almost anywhere foreshadows the future of radio control. For multi aerobatics, it extracts all the performance available in the Simpro system. Prophet, by Dave Robelen.

The Prophet is a look into the not-too-distant future, when multi-acrobatic models can be flown almost anywhere. It is not a warmed-over single-channel, rudder-only design, not a scale copy of some larger model. it is an airplane designed to extract the most performance from the new Simpro control system. And it only uses an .020 for power! That it was a success is an illustration of what the future holds - hence the name Prophet.

The Prophet is capable of any AMA RC stunt maneuvers that does not require a pure yaw force. A few of it's specialties are: consecutive outside loops; 4-point rolls; lovely, slow, axial rolls; and, in general, all aerobatic maneuvers that are based on looping and rolling. It should be abundantly clear that it is no trainer.

If you have flown other high-performance miniature planes with proportional control, you are in good shape for the Prophet, otherwise build something tamer to practice on with your Simpro - such as the Schoolboy (oz1030) or Schoolgirl (oz816) by Top Flite, either of which make excellent trainers for miniature dual-propo. The Prophet trims out at about 40-45 mph. It is not highly affected by wind, so you do not have to hide it in the car if a breeze comes up. This makes it poor as a trainer.

The greatest factor in any small RC model is light weight! Every effort should be made to keep weight down. The Prophet should weigh approximately 10 ounces. If it is much heavier, performance will suffer greatly. Materials need not be as strong because light weight keeps impact damage low. A heavy model of the same size is more damage prone, and will not fly nearly as well.

Because I did not want a tricky linkage, as would be required for CAR (coupled aileron and rudder) I used only aileron and elevator control. This has worked well and probably is best for the low-wing layout. With a low-wing design the roll maneuvers seem better.

With ailerons as the only directional control, the airplane must have a very true-tracking landing gear. This, plus a large fin to insure weathervaning, will almost guarantee good ROG's every time. Do not omit the plywood panels shown on the plan in the wing center-section bottom, unless you enjoy re-pairing torn covering. This is not shown on the original model, and the wheels punched a few holes in the wing cover-ing during rough landings. The tail-wheel is also important as it keeps the model tracking until the tail comes up. The small spring loop shown allows a lot of flexing and bending without breaking the strut loose. The main wheels called for on the plan are important; they are true rolling and low drag. They are the correct weight to position the CG vertically.

The engine choice is limited and the TD .020 shown is tops for the job. The airplane is not designed to accept an .049. Brute power is not the only road to good performance.

There are a number of propellers that work well on this model and engine, but I think you should experiment for best results. A Top Flite 5-1/4 x 3 nylon gives good all-around pep with excellent fuel economy..."

Update 14/04/2016: Article pages, text & pics added, thanks to RFJ.

Supplementary file notes

Article pages, text & pics.

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Prophet (oz3120) by Dave Robelen from American Modeler 1967 - model pic

Datafile:

Prophet (oz3120) by Dave Robelen from American Modeler 1967 - pic 003.jpg
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Prophet (oz3120) by Dave Robelen from American Modeler 1967 - pic 004.jpg
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Prophet (oz3120) by Dave Robelen from American Modeler 1967 - pic 005.jpg
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User comments

Hey there! Thought I'd send you a pic of my latest build for the gallery... An electrified Dave Robelen Prophet [model pic, morepic 005]. Feel free to do with it what you will. Thanks so much for all the plans and work you go to... I don't know what we'd do without OZ!
MichaelJ - 29/08/2016
Just saw this plane come up on your random selection of planes. Interesting in that the designer says the plane is "not a scale copy of some larger model". Really? It certainly looks like a reduced scale version of Bill Winter's original Rookie (oz7611), not the updated version published years later in Model Builder. Also, the supplement file appears to be incomplete. At the end of the last page, the article cuts off, with a lead to page 54. There is no page 54. Everything ends at page 53.
MatthewStikeman - 13/06/2017
That's an interesting point about the Rookie, Matthew. Can anyone help with the missing article page?
Mary - 13/06/2017
Added missing page to plan article just now, thanks to RFJ.
Mary - 14/06/2017
While I have no issue with someone building to a different size to fit their needs, I do have concerns when a design is copied to a different scale, renamed, the original designer is not acknowledged, and the plan is published. Dave Robelen does acknowledge Bill Winter in the build article for his Prophet, but in another of his plans he does not. Take a look at Robelen's Pipsqueak (oz6211). Looks very much like a scaled-down Don Parson's Esquire (oz384), and the Lil Esquire (oz621). There is a reference to an Uncle Don in California but I believe that is to Don Dewey of RCM, not Don Parsons. Just my 2 cents. For what it's worth, the guy who got me started in R/C back in the 1960s flew an Esquire, I had a Lil Esquire and the Pipsqueak, both on pulse rudder and Cox engines. Regards, and keep up the good work.
BillH - 15/06/2017
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