Trio (oz10940)

 

Trio - plan thumbnail image

About this Plan

Trio. Radio control slope soarer. A three in one Slope soarer for 2-3 function RC.

Note this plan shows three alternate wings, at woingspans of: 61-1/2 in (trainer), 61 in (pylon), and 57-3/4 in (aerobatic).

Quote: "A three-in-one glider- intermediate, three-function trainer or aerobatic. Trio, by Graham Freeston.

THIS MODEL was developed for the simple reason that I don't like changing my radio gear from one model to another. I don't think it agrees with the wiring harness or the plugs to do this too often. (Also I'm jealous of people who have two sets of equipment.) Seriously though, I considered that it should be possible to progress from a first model - ie a rudder-and-elevator trainer, through to a fully-fledged model with a symmetrical aerofoil and ailerons. This, without building three models. It has been possible to do this and yet retain a neat looking and interesting model - I think so, anyway.

I had built the original, and got it all nicely sorted out, when a new club member asked if he could build one. Very flattered, I agreed - in fact, the photographs are of his model, not mine. I hate to say it but his is better finished - though he hasn't caught me up on the flying side (yet!). As the name suggests, there are three wings, for the one fuselage and tail unit, each with different characteristics, as follows:

Trio I, a two-function rudder-and-elevator trainer, with a dihedral wing using a thickish, flat-bottomed aerofoil section; mildly aerobatic.

Trio II, a three-function aileron trainer, with a flat wing (no dihedral), using a thin, flat-bottomed section, and having tapered strip ailerons. Good for pylon racing; mildly acrobatic.

Trio III, a three-function aero-batic model, having a flat wing of constant chord, using a fully symmetrical aerofoil section and strip ailerons.

CONSTRUCTION: Fuselage. Of simple construction but having reasonably pleasing lines, this appears to suit the wings, anyway. I have tried to get away from the boxy looking trainer type of configuration, without recourse to adding 1/2 in sheet and planing it nearly all away again! I think the plan is pretty self-explanatory, and should not really need much elaboration. Just a few musts, however.

1. Do include the vertical trian-gular pieces in the fuselage - they really hold the model together in the right places.
2. Don't use anything less than 1/16 ply for the fuselage doublers.
3. Don't stick the fin on top of the fuselage; take the trouble to put it through the top and firmly cement it to the bottom, as per plan.
4. Don't sheet the top rear fuselage until the control rods or cables are in position. Otherwise, it can be very fiddly getting these through satisfactorily.
5. Don't be tempted to use 'the eye' when putting in the bulkheads; use the centre line on the plan, and pull the sides in together accurately, too.
6. Accuracy is also essential when drilling the dowel holes in the fuselage, as the holes also go through the vertical pieces. Drill the holes in the fuselage sides first so that they will act as guide holes after you have added the vertical pieces - if you see what I mean.

Tailplane: Quite simple, but do not forget the keys and the hardwood leading edge centre-piece. Choose fairly light wood for the tail itself. I used mylar hinges on the original, but this is a matter of personal preference.

Wing, Trio I: Usual type of structure and construction. Leading edge, lower main-spar and matched trailing edge are pinned to the board before assembly. The first three root ribs are faced with ply; don't omit this, as I feel it contributes greatly to the root strength. Stick to the dihedral as it is - I know it looks a lot, but it's there for a reason, Also remember the sanded-in washout at each tip, which helps stability and, incidentally, tapers the outer wings a little.

Wing,Trio II: I enjoyed building this one, and it's my favourite of the three. Construction is easy. Starting by gluing together, edgewise, two sheets of 36 x 3 x in medium grade balsa. You need 8 sheets for this wing and, if you are not 'genned up' on wood selection, it is best to rope in someone knowledgeable to assist. This is important, as the whole wing is sheeted.

Pin the bottom sheet down and add the leading edge (rear one), centre spar and trailing edge on top. Don't add the front leading edge until the top sheet has been added. I used white glue for everything except the top sheeting, where a contact adhesive was used. Finally, and most important - don't remove the wing from the building board for 24 hours after completion; it really has to stay put because the lower sheet may tend to produce a slight midercamber if the structure is lifted early... "

Trio, Radio Modeller, September 1975.

Direct submission to Outerzone.

Supplementary file notes

Article, thanks to RFJ.

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Trio - completed model photo

Datafile:

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