SAM-5 (oz4193)

About this Plan

SAM-5. A/2 Glider. Here is Ron Evans' SAM-5 from Model Builder magazine issue 07-72.

Update 10/04/2020: Added article, thanks to RFJ.

Quote: "This contest winning A/2 is the current peak result of a long line of development aircraft. The brief out-line of the experiments involved is worth the time to read even if you don't intend to build the model. SAM-5, by Ron Evans.

The SAM 5 as presented here is a development of the SAM series which started it's life in 1969. Since that time there have been 11 SAMs built by this writer, and 4 or 5 others by local flyers. The number of changes is hard to pin down, since components have been switched, separate wings built for the same fuselage, different rudder locations and sizes on the same boom, and so on. The greatest number of changes have been to the wing and stabilizer airfoils.

I was fortunate enough to have received a great deal of help in regard to new theories, airfoils, and trimming suggestions from several sources, notably Vic Nippert and Hugh Langevin. The primary aim throughout all the changes was to evolve a stable, strong, consistant airplane. 'Dead Air' time was not given too high a priority, although a lower limit of 2:30 was considered minimum. All the airfoils to date have reached or exceeded the minimum limit (some just barely) except the Ritz 6407D, at 2:25. The main considerations were; good tow stability and thermalling ability. Ease of construction has not been of any great concern. My feeling is that anyone who desires an easy-to-construct glider ought to fly Hand Launch Glider. Nordic Glider is one of the 3 World Champion-ship events, and as with anything of 'Olympic' caliber, you get what you pay for.

It probably would take up more space than it is worth to detail all the changes, trials, and tests here. I will simply explain briefly why I have presented this particular model to represent the best of the series. The rear fin was tested against both front fins (4 of them) and T-tails (2), and shows the best tow control, and no discernable advantage or disadvantage in the glide. A good towing model is hard to argue with. The GF 6 wing section has the best non-thermal duration of all the sections to date, excells in light lift (the B 6456 F is the only other section to consider for light thermals of the airfoils tested), and can be flown in very windy weather with good results. The Ritz 6407 D can handle bumpy or turbulent weather a bit better than the GF 6, but loses points in both light lift and no lift conditions. The CH 407 has not been tested well enough to recommend it, but early tests indicate it may give the GF 6 a run for the money, in any weather, provided it is matched with the proper stab section. It was not responsive with a flat bottom stab, but now is flying well with the 'Osprey' stab shown on the plans. The Osprey stab section, incidentally, was the best match for the GF 6, from a sampling of 5 different stab airfoils. The pylon/shoulder wing mounting question has not been answered to my satisfaction; they cer-tainly do not have a significent effect on either the tow or glide, so I have presented the nose that is more within the reach of the average modeler. The aluminum nose/pylon requires access to a machine shop to duplicate, and has no real drag reduction, all things considered.

Construction: The place to start is by obtaining all the balsa wood, hardwoods and miscellaneous small items like auto-rudder stops, towhook, tubing, etc. By doing this and also prefabricating the laminated parts (Wing LE & TE, planking, etc) you will save a great deal of time. Cut all wing ribs to shape, making only the normal spar notches - leave the doubler notches for later.

Tack cement 8 ply blanks together with a non-penetrating glue such as Testors, saw to shape (again, no doubler not-ches) and drill 5/32 inch holes for tubes. Split them apart with an X-acto blade. The tip ribs are formed by the stack method - that is by pinning together 13 pieces of 3/32 x 5 x 3/4 inch balsa, with the root template at one end and the tip template at the other. Carve to the shape indicated by laying a straight edge across both templates. Repeat for opposite wing..."

Supplementary file notes

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