About this Plan
Tara. Radio control sport model.
Quote: "Getting started with DB! You've read his advice in our free supplement, now try David Boddington's simple primary trainer in two popular sizes.
Read the supplement presented with this issue and you will realise that the pull-out plan 'Tara' is slightly smaller than the ideal beginner's model. However, if you are prepared to wait for good weather conditions, this model, having a built-up structure and light wing loading, is certainly capable of getting you to the stage of solo. If you want to go to a larger design all you have to do is to take the plan into one of the many specialist printing establishments and get the drawing enlarged by 1/3rd (33%) and this will give you a model of 62 inch span.
You will notice dimensions in brackets on the drawing and these refer to the larger model. One of the few areas where you will have to make adjustments on the larger version (Tara-Two) is on the servo bearer spacing; fit them to suit the servos you are using. You don't need to fit mini-servos on the small Tara, it is quite possible to install standard size radio equipment and a 600mAh nicad battery.
Engine sizes on the little Tara are not critical; the prototype model was flown with an AE2.5cc diesel and a Magnum 10 R/C (1.5 cc). The diesel gave a sprightly performance but the small engine is more than adequate. Both engines were commendably quiet, making the model/ engine combination suitable for flying at any flying site. For the enlarged Tara-Two a 40 four-stroke, or the Irvine Quiet 40 two-stroke, would provide more than enough power.
Why the fuselage shapes? Aerodynamically it is sound, it keeps the tailplane well clear of the ground. The method of construction allows for standard sized balsa sheets to be used on both versions and it is unlikely that the models will turn out to be tail heavy - a failing of many so called training models. One other reason for the 'two-tier' fuselage is to allow it to be a load carrier in its sports model mode - you can use the rear of the lower fuselage area for carrying 'goodies'. Wing tip fins possibly help to prevent the high pressure air under the wing from spilling over to the top wing surface - they are also simple and look different. The equivalent tips on the tailplane help to prevent twisting of the sheet tailplane.
Before commencing construction note that you will need to cut away part of the plan and fit the nose area of the fuselage to the main fuselage drawing. Do not cut the plan until you have marked and cut out the tailplane, shown on the other side of the drawing. Note that, although the wing panels are similar at the root and tip, the root ribs have to be angled for dihedral, ie make one left hand and one right hand panel.
I use mostly PVA white glue for construction, it takes a little longer to dry but the strength and flexibility of the adhesive is excellent for these built-up models. Cut out all parts before you start assembly, select your wood carefully, i.e. fuselage sides are equally matched, tailsurfaces are light but firm and that spars are reasonably hard and straight grained. So, with a sharp knife and flat building board away you go — and remember that the model will only fly well if it is built true.
Fuselage: Check and mark the position of the engine, fuel tank and radio equipment. Join the upper and lower parts of the fuselage sides and glue the doublers and treblers to the internal surfaces of the sides (use formers F1, F2 and F3 as temporary spacers). Mark the position of the engine mount on Ft and drill pilot holes for the fixing screws and for the nosewheel saddle.
Glue the formers F2 and 3 and the engine bearers to the fuselage sides and check that they are square. Drill the holes for the undercarriage legs in the plywood plate and glue this to the treblers. Sheet the underside to the fuselage between F2 and F3 and you will then have a rigid central 'box'. Former F1 can now be glued in position, followed by the fuel tank floor and top and bottom sheeting - leaving a hole for the insertion of the fuel tank. Glue F4 and the sternposts in position, check for equal curvature on the sides and then add the top and bottom sheeting. Round off the front edges of the fuselage and sandpaper the whole smooth; cut a slot for the fin in the top rear sheeting.
Tailsurfaces: These are cut from sheet and strip, the leading edges are rounded and the elevator and rudder are tapered to the trailing edge, leaving a thickness of about 1/16 in at the rear. Cover the tailsurfaces separately but leave the areas to be glued to the fuselage uncovered. Moulded mylar, or mylar strip, hinges are probably the most suitable for the small Tara' and moulded pin hinges for the larger version. Use a slow setting (one hour is OK epoxy for fitting the hinges and check with a 'dry run' that they all fit before committing to the glue.
Wings: A flat bottom wing section is used so that the wings can be constructed directly over the plan. Pin down the front lower and rear spars and lower trailing edge over the protected plan. Add the ribs, angling the root rib, followed by the front top spar, leading edge and top trailing edge. The top leading edge sheeting and centre and tip sheeting is added last. When dry, remove from the board, shape the leading edge (check that the two panels marry accurately at the root) sand thoroughly and cut slots for the dihedral braces. Glue the braces to one wing panel, leave to set, attach the other panel and prop up to the required dihedral under each tip (or pin down one panel and prop up the opposite tip to twice the tip dihedral). Add the tip plates and round off the corners.
Covering: The structure of the model makes it suitable for any of the conventional materials, although I would recommend a 'tex or nylon covering for the Tara-Two. The prototype small Tara was covered in a fluorescent flame orange Polytex, the bright fluorescent colours are a distinct advantage for ease of visibility when flying. Restrict your decoration to a reasonable minimum, but don't skimp on the fuel proofing, especially around the fuel and engine bays.
Radio installation: Fit the servos and linkages after the tail surfaces have been glued to the fuselage (slow setting epoxy). I have suggested a closed loop linkage for the rudder because of the low inertia weight and positive movement. Closed loop is not convenient for the elevator and a pushrod (3/16 dia beech dowel with threaded rod cycle-spoke ends) is suggested for this linkage. Throttle linkage can be a solid wire in tube, or a plastic rod in tube; install with the engine positioned.
Although there is space under the fuel tank bay for a flat nicad battery pack you may find that, in order to obtain the correct balance point, it is preferable to situate the battery behind the servos. Leave the battery position optional until the model is complete and assembled so that it can be moved around to obtain the best balance point.
Preparation: With the model assembled and correctly balanced, check all the control movements. The elevator and rudder throws are quite adequate for training. If the engine has not been run it is best to run it in on a test bench or - under the guidance of an experienced modeller - in the model. Obviously we do not want to risk an engine stopping at an embarrassing moment during the flight, or damaging the engine through having a 'lean run'.
Flying This is your first model? If it is do everything possible to get it checked out - and test flown - by a responsible, proficient R/C modeller. We all make stupid mistakes from time to time (such as having the rudder moving in the wrong direction) and the best way of finding out these mistakes is to let another pair of eyes make an inspection. Once you are satisfied that all is as it should be it is off to the flying field!
Again, I cannot over emphasise the advantage of having an experienced modeller carrying out the test flights. Built accurately, Tara will fly well, is very stable and is not difficult to control - providing you do not 'freeze' on the controls, over correct or suffer from disorientation, all possibilities if it is your first flight. Nerves and confidence - or the lack of it - play a very large part in learning to fly; it is much easier if you take to flying gradually and in an organised manner. Once trimmed out and at a safe height is the time for you to be given the transmitter, or better still be handed over control on the buddy box - to have the responsibility from the moment of take-off can be paralysing!
With the smaller size of engine fitted you may have difficulties in taking off from grass, unless it is very well cut and rolled, and a hand launch is preferable. Straight into wind, level and at a moderate speed should give the operator little to do on the controls, just minor control inputs to keep the model in a shallow climb-out. From tarmac even the 10 size engine (Tara) or 30 (Tara Two) will provide enough speed for a safe take-off. Check first that the tricycle undercarriage is allowing the model to track straight, no more than a little right rudder should be required to keep the model straight during the take-off run and lift-off is achieved by a small application of up elevator.
One advantage of the lower power range and modest control movements is that the student is less likely to get into a dangerous position (a fast spiral dive towards the ground, for instance) and every chance that, in a panic situation, centralising the rudder and elevator - by letting go of the transmitter sticks - and throttling back the engine there is a good likelihood the model will recover itself from difficult situations, providing there is reasonable height.
Turns are positive and there need not be any height loss. To prove this point I have carried out left and right hand circles and figures of eight with the Tara' just a few feet above the ground - quite exhilarating, but not to be recommended for the beginner! There is enough drag with the model to allow it to be slowed up nicely for the landing. Keep the approach fairly shallow, with a steep approach you may find yourself running out of elevator authority. As always, plan your landing circuit to follow a rectangular pattern and get lined up for the landing in good time so that your final control movements are only small adjustments. Oh, don't forget, height is controlled by throttle (more engine speed to climb) and speed is controlled by elevator. If you find this difficult to grasp just think of a landing approach where you are too high and too slow. Putting in down elevator (not too much!) will speed up the model and prevent it stalling and you will still have sufficient height to reach the landing area. For further proof that the engine speed controls ascent and descent I would refer you to the days when we flew models with only rudder control and a rudimentary throttle control (no elevator); we were still able to go higher or lower with this 'primitive' control system."
Direct submission to Outerzone.
Quote: "Hi Mary, Glad to hear all is well with you :) Here is one more - a David Boddington design no less, this time for his TARA trainer from Nov '93 Radio Modeller. I once read in one of David's articles that he did his first really successful RC flying with the KK Super Sixty and was thus very fond of that design. In the noble spirit of "if it ain't broke don't fix it" he often seemed to base the aerodynamic layout and wing structure of his sports/trainer designs on that model (the Tyro series are excellent examples). I may be wrong but I think there is still a hint of the good old Super Sixty here. All the best,"
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