Fakir I (oz10942)
About this Plan
Fakir I. Radio control. Wingspan 65 in, wing area 650 sq in.
Quote: "A pattern machine with very little trickery, but capable of producing extraordinary, almost magical, results. Fakir I, by Howard C Mottin.
The February 1973 issue of AAM contained the announcement of a Super Design Contest, based on the drawings of Bob Lopshire. The bottom view of the Fakir was on the cover of the Doylestown World Championship program (also on the October '71 AAM) and the top view appeared on the cover of the February '73 AAM. Using the rules for the contest as a guide, I created the idea of the Fakir-l. The contest called for the plane to be designed on paper first and then constructed according to those drawings. Finally, the rules required that the flight characteristics be demonstrated by appearing at the '73 NATS in Oshkosh.
The primary objective of my particular design approach was to create a plane that would have good flight characteristics. Many pattern aircraft are developed through a build-and-crash procedure, often encompassing several years. In this way, the bugs and design deficiencies are eliminated one by one, until an optimum craft is achieved. Because of the time restrictions imposed by the contest, this was impossible; so the next best thing was to model the plane according to existing designs of known flight quality.
The first step in the design procedure was a dimensional analysis in order to arrive at the overall configuration. Current design trends in pattern planes decree that their weight is between seven and eight lb., with wing areas of around 650 sq in. The overall configuration of the plane was dictated by Bob Lopshire's drawing in AAM. This, then, was the basis for the design, with each component defined by experience and the state of the art analysis.
DESIGN THEORY. Wing: The wing is the most important single feature of a pattern design. A goal of seven lb total weight and a 650 sq in wing area gives a wing loading of 25 oz/sq ft. This is on the heavy side, but about standard for the top pattern design of today. The wing planform with a straight trailing edge and swept-back leading edge, is dictated by the AAM drawing. Aspect ratios have traditionally been between 5:1 and 6:1, with the higher ratio being more stable about the roll axis, and having better turn and spin recovery characteristics. A wing design l have evolved through the years has a 5.7:1 aspect ratio.
This design must incorporate inset ailerons. Using a figure of 11 percent of wing area, I arrived at an aileron area of 70 sq in. The current trend of using torque tubes eliminates the bellcranks and pushrods in the wing, and also satis-fies the contest requirement of no exposed linkages. The original design called for a 1/8 dia torque rod, but this had too much flex, and was re-placed with a Rom-Air torque rod unit.
The next important selection is that of airfoil.Through the years, hundreds of different airfoils have been tried, and many have been claimed as the optimum for RC. Currently, the symmetrical sections are the most popular, with 15 percent thickness just about the standard. Because this was to be a highly tapered wing, some method had to be employed to prevent tip stall. Dismissing wash-out, there are three common methods to prevent tip stall:
(a) increase the thickness percentage at the tips;
(b) maintain a constant large lead-ing edge radius;
(c) gradually change the tip to a slight lifting section.
Point (b) was used in the design of this wing.
Incidence and dihedral complete the wing analysis. The 0-0 setup is the standard of today. I like to design my wing to be 1/32 lower at the trailing edge, just to insure that the wing does not end up negative. For all practical purposes, this is still a zero incidence design. The current trend is also toward zero dihedral. I prefer one in under each tip, just for appearance's sake. With the swept-back leading edge (the sweeping giving effective dihedral), this probably figures out to be about 20. In summary, the wing was designed to the following dimensions..."
Fakir, American Aircraft Modeler, May 1974.
Direct submission to Outerzone.
Supplementary file notes
Article pages, thanks to RFJ.
Did we get something wrong with these details about this plan (especially the datafile)?
That happens sometimes. You can help us fix it.
Add a correction
Do you have a photo you'd like to submit for this page? Then email firstname.lastname@example.org
User commentsNo comments yet for this plan. Got something to say about this one?
Add a comment
* 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.
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.
© Outerzone, 2011-2019.
All content is free to download for personal use.
For non-personal use and/or publication: plans, photos, excerpts, links etc may be used, provided that full and clear credit is given to Outerzone with appropriate and specific direction to the original content i.e. a direct hyperlink back to the Outerzone source page.
Unauthorized use and/or duplication of this material without express and written permission from this site's owner is strictly prohibited. If we discover that content is being stolen, we will consider filing a formal DMCA notice.