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The kit arrived safely in its quite large box all parts being packed well with screen and side screens wrapped in their protective film. Cowl and wheel spats are wrapped in plastic bags and clevises, screws, tail wheel and wheels etc are also bagged. There is a good selection of nuts, bolts and screws to use in the construction. Also in the depths of this box there was to be found the Dural landing gear and Dural tubes used for the wing joining spars. Together with the engine mount there is to be found a spinner and wheels and in the very bottom of the box the push rods with their inner tubes, more about these later. The larger components are also packed nicely and had travelled through the post well with no damage, from the Czech Republic. This is where the Hacker Model Production come from.
One of the first points that was noted is that the flexible cables, which are listed in the instructions for use as bowden cables to activate both the elevator and rudder, to my mind arenít really up to the job in hand. They would possibly be ok if you could drill small holes in all of the fuselage formers all the way back to the exit. In which case I may have used them but as this is impossible to do and that there are no holes provided I decided to take a different route, to cure the problem. Firstly I was going to fit a bigger engine. In fact I was going to take full advantage of the quoted maximum engine size of 20 cc four stroke (120) size. This enabled me to quite happily cut out a hole in the back of the fuselage to take the elevator servo and to then run the servo leads back up the fuselage. This will help balance out the model later and into the bargain it gives a much better and direct push to the elevator. The rudder is moved in the same way as the elevator if you follow the instruction to the letter but again I have my own way of getting good solid movement and that is to use a pull pull system. To install this all I needed to do was to drill a 3 mm hole at an angle on both sides and install two tubes which carry the cables to the servo. This system of putting in tubes for the cables has in the past paid dividends as it allows me to replace or change cables at will.
As mentioned earlier I decided to install the largest of the engine sizes quoted and to this end I am using my Yamarda 120 The installation soon became clear that it would be quite a nice fit. After carefully measuring the plywood block which is glued on to the bulkhead former to give the correct down and side thrust, the engine mount supplied was drilled to take the engine. Also to my delight the engine is totally enclosed without the exhaust manifold on, so it looks quite neat and tidy. The only thing that is going to protrude out of the cowl it seems is the exhaust manifold and exhausts outlet pipe itself.
Next I decided to fit the two wing panels which attach via two wing tubes through the top of the cabin and the wings locate either side. These are then held in place with two hooks on which an elastic band pulls and holds them up to the fuselage sides.
I had to make two minor adjustments to this part of the build and the first was to check the alignment of the wing panels on the fuselage. This I did using my trusty incidence metre. Firstly I found that both incidents were spot on but the dihedral angle was out on the starboard wing as it didnít fit all that well to the fuselage and to this end I made some small adjustments to the wing tubes and the locating holes. The incidents and dihedral was now spot on. Next alteration was to the wing fixing and to do this I used the screw in hooks supplied in the kit but I also cut myself two pieces of dowel and after shaping them to a point. I pushed these through the hooks when the wings are in place and this hold the wings firm against the fuselage sides.
Next to fit is the tail plane and fin. There is a triangular balsa insert and this is glued and making sure that it is both square and level in the rear of the fuselage as it is to this that the tail plane is fitted and glued. A nice square set up here pays dividends later when it comes to flying so pay attention to getting this part right. We should also check that it is square with the wings. Taking time over this and using a slow setting glue helps. Getting back to the fuselage we can now install three servos at the back of the cabin area. This will help with the centre of gravity position so that we do not end up with lead in the tail. By assembling the plane it is noted that to get the centre of gravity somewhere ok I will also have to install the battery pack near or behind the three servos. I used some bracing wood to hold things together so that the battery is safe.
I now move on to the side windows which need to be trimmed and cut to fit. These should be removable as I feel at a later stage access may be needed. The front screen is firstly cut to the lines, which are faintly marked on the moulding, these were found to be accurate and the screen fitted well. Before taping into place I marked out the area and painted this matt black to represent the cockpit combing or top of the dashboard.
We next must fix the wing struts. I am afraid to say that I have altered mine and installed them differently than the instructions recommend At the wing end where the struts meet the wing I have used two split pins and this end is permanently attached to the wing. This makes for a better fit. At the fuselage end I have used the brackets as supplied but instead of using self-tapping screws I have used blind nuts on the strut ends and an Allen bolt. This way seems to work very well and makes for a more durable fit which should last longer than the self tapping screws.
The spats were rubbed down on a flat surface so that when the two halves meet and are glued together the fit is sound. For glue I used super glue and filled the edge with P40 Plastic Padding. When I was happy with this I rubbed them down and sprayed them the correct colour. After this the cowl is fitted after cutting out the appropriate holes for exhaust etc and this was sprayed with undercoat and the appropriate colours used for a match of the fuselage colours. The wing tips are also sprayed and I fixed these to the wings using silicone and after it had dried they seem to be fixed very well.
We are now about ready to have a final fit of servos and running gear. The battery is used to get the centre of gravity in the correct place and the position is kept flexible. Engine runs are next on the list and these went well.
The weather wasnít quite as good as I had wanted. We had quite across wind blowing at 45 degrees to the runway and after doing the usual checks of range and a last good look around the model the fuel tank was filled. After starting the engine the controls were checked once more. We then lined up on the runway taking note of the wind came from the left. On opening the throttle carefully rudder was used to keep things going straight until speed at which the model felt like leaving the ground was reached.
We left the ground using about half throttle and this was more than enough to cruise around to get some trimming done. After the first circuit and a few clicks of trim the controls were found that the ailerons were lacking in power and the Decathalon was yawing the opposite direction to the roll. I made a mental note to adjust the throws so that we had some more up than down aileron. Rudder was found to be the more powerful of the three controls and at times felt quite sharp so we needed to slightly calm this down around the centre using exponential. It was also noted that I had introduced too much right and down thrust on the engine, this I had foolishly done as I thought that I would need slightly more when using a bigger engine. We also found that the centre of gravity when moved slightly forward had a benefit to the overall flying quality and after these adjustments and flying in less windy conditions I am finding it a very pleasant model.
The Decathalon is quite aerobatic when pushed. Loops and any pitching manoeuvres being its best quality. Stall turns are another favourite as it has a powerful rudder with which to yaw it around. Rolling has got better with the adjustments I have made to the controls so that I have now got twice the amount of up going aileron to the down going aileron. This had also helped with adverse yaw that we were experiencing when turning. The aeroplane now turns ok using ailerons and elevator only but it really likes to be turned using both rudder, ailerons and elevator which produces a much more balanced turn.This looks nice but do remember that the rudder is very effective and it can be used along with the elevator to turn this aeroplane very quickly.
Now that I have flown the Decathalon quite a few times I am beginning to fly quite a nice aerobatic routine. It may not have the aerobatic capabilities of a CAP or Extra but it is certainly ok with most standard manoeuvres.
She spins nicely from a stall and the stall itself is very slow in coming. This plane will fly fairly slowly and when the stall is reached it does nothing more that nod and only spins when the rudder is used to provoke the spin. Stopping the spin is easy with neutral rudder and down elevator and the plane stops rotating. This can be made quicker if down elevator and some throttle is introduced so that there is a blast of air over the controls. Flat spins are also capable but do need more height in which to stop but these look good when using throttle and a little out going aileron and then slowly easing off the up elevator. Please remember that you may have four to six turns in which to stop the rotation and exit the spin and regain level flight. Flick rolls are great to perform using just elevator and rudder but using opposite rudder and aileron and some down elevator to get things stopped and the plane back flying level again.
I feel that this model looks nicest in the pitching manoeuvres and it is happiest looping or stall turning. She can roll ok but not quite as tidy as I would like but you cant have everything in one plane can you.
In conclusion this aeroplane doesnít fly quite as stable as the Cub but is also not as aerobatic as most sport planes. It is certainly not a trainer but a plane for the slightly more experienced flier.