Even with the addition of the motor, the AV36 still didn't seem to be getting much airtime. Meanwhile, I've found myself fairly regularly meeting up with a group of aertow enthusiasts and so, recalling that this model was originally designed for thermal soaring, thought it would be interesting to see how it performed from the towline.
Of course, this is a mod which would have been so much easier had I not already fitted a motor up the nose!
I bought a Multiplex release with a view to mounting it in the nose, either above the motor or below, as indicated on this picture.
The lower position turned out to be impractical, mainly because the area had been cut away to accomodate the wires from the front of the motor. The upper position looked feasible but concern was expressed about whether it might cause the glider to adopt a somewhat low position relative to the tug.
Mindful that the elevators on this model do lack authority at the best of times, I didn't really feel too happy about either of these options.
So, after much deliberation, the Multiplex release was ditched and instead a piece of plastic tube was fixed inside the left hand side of the fuselage - you can just see the yellow end of the tube directly to the left of the motor in this picture.
Even though I took the motor out to improve access, this proved to be a very awkward job and it took several attempts to get the tube securely fitted - followed by some equally awkward sanding and grinding operations to restore clearance with the rotating motor drum.
Next, after some careful measuring, a hole was made in the side of the fuselage as near to the nose as I dared go. A wire was then threaded down the tube and, with the aid of a torch, I peered hopefully through the hole. Happily, the wire was spotted and so the hole was opened out a little, centering it on the wire. I was a bit concerned that towline, under tension, might cut its way into the woodwork, so managed to distort an eyelet in the vice and glued it into the aperture. Of course it wasn't possible to get inside to flare out the tangs on the eyelet, so I just have to hope that the towline doesn't get hung up on them.
The last element of the job was mounting a servo to operate the release. Fortunately there was just enough space between the front bulkhead and the battery box to squeeze a wing servo in, although again much fiddling and adjustment was needed to get everything lined up.
So, does it work! Well, I only had to wait a few days to find out. Thanks to Chris Williams for the photographic evidence below (and, as always, to barry for the towing).
The above picture seems to show the glider adopting a position slightly to the right of the tug. This may well be the case but I can't say I was aware of it at the time. In any event, the model was very well behavied on tow. I found myself holding in a bit of up elevator to maintain line tension. Ordinarily I would prefer to use brakes for this but the braking arrangements on this model, though effective, are complex and a side effect is to reduce elevator authority even more.
The last picture above shows the landing approach. Determined not to drop short, I came in from a good height on quite a steep descent. The brakes themselves are not visible in the picture (as per full size, they take the form of spoilers on the underside of the outer wing panels). However, you can see the bit of up aileron mixed in and also the use of full 'out' rudder. This combination really works well but does require all of the physically available down elevator travel to be mixed in as compensation. The result seems to be that the elevator 'hides' in the downwash from the wing and becomes even less effective than usual. All of which is my elaborate excuse for the landing being a little on the firm side due to me not giving the model sufficient notice to flare out!
A second flight was undertaken, this time with the propeller fitted. This too went well and the motor was used to climb back up to height a couple of times, so prolonging the flight. The landing was a bit better this time too.
So this model has now undergone a number of modifications since it first flew:
i) Provision to add ballast for flying in stronger winds. ii) Addition of a motor to encourage flying in marginal slope conditions iii) A tow release for flying off the flat - with the option of using in conjunction with the motor.
Hopefully, it will henceforth get to fly a little more frequently!