Tarman (oz8056)

About this Plan

Tarman. Radio control sport model.

Quote: "The Tarman, like most present day aircraft, is a composite of the attractive and desirable features of other models. It has evolved, during the past year and a half, to its present configuration which, to the author, seems to be the ideal blend for a sport and competition model. Not being a competition flier, the Tarman has never been entered in a contest, so I cannot present an impressive list of accumulated hardware to accompany this article. Due to the amount of traveling required by my job, I'm usually in the wrong place at the wrong time for a contest!

This is not to say that the Tarman would not give a good accounting of itself in competition circles - it flies the pattern quite well, and has excellent slow speed characteristics due to the modified NACA 2419 airfoil. Quite simply stated, it goes where you aim it, and does everything you ask of it. It will do all of the AMA and FAI maneuvers, including easy knife edge flight and inverted spins. The latter is quite easy to accomplish since the plane will come right out of the spin upon relaxing your death grip on the sticks! I might mention that it will do these maneuvers in the high Texas winds that have grounded many of the popular pattern aircraft.

The Tarman is very easy to build, and has the appearance of a late model cropduster.

Wing. The choice of foam core wings offer many advantages, and have been used on all of the planes that I have built since Ed Izzo's first articles appeared on this method of construction. In my 24 years of modeling I find them to be real time savers. I have also found that my wife is very proficient on the other end of the bow! I will not go into the details of the actual cutting of foam cores since this has been covered in infinite detail in the RCM Annual (1966) and the summer 1968 edition of RC Limited.

After the wing cores have been cut, and before sheeting or covering, I draw the outline of the ailerons. I prefer the conventional barn door ailerons since they require very little extra effort, add to the appearance of the plane, and improve the overall efficiency of the aircraft. It is recommended that the aileron horn be epoxied in position right in the foam itself. Then, align the bellcrank position, cut out the well for the bellcrank clearance as well as for the pushrod. Instead of attempting to cut a channel for the pushrod from the servo to the bellcrank, try using a gun cleaning rod heated with a propane torch. This makes a clean, simple tunnel and is quite simple to accomplish. Mark the foam for the proper location, and use blocks of wood to hold the heated rod to the right height, then push it to the bellcrank area. This "tunneling" process eliminates the tendency of foam cores to warp, as they are prone to do when channels are cut into either the top or bottom surfaces. And, after all, one of the main reasons for foam cores is to produce a true, warp-free wing.

The bellcrank and pushrods are mounted before the sheeting is applied to the wing. Also, install a 1 dowel landing gear support located above the main gear trunion. This gives additional support to the landing gear for those occasional less-than-perfect landings! The wing is then sheeted, making sure to provide the necessary holes for the aileron horn and for the pushrod as the sheeting progresses to that area of each panel. Block up each wing panel 1 in, and sand the root section to provide the proper dihedral bevel. Join the wing halves with HobbyPoxy No. 2 glue..."

Supplementary file notes

Article, thanks to Cavitation.

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