Back to Part 2

Each Way Bet - The Full Story
Part 3 - Parturition
by Trevor Hewson

Now, my drawing ability is close to zero so for me, the sketch shown at the end of part 2 of this story constitutes a working drawing. It was therefore simply scaled up on the photocopier, then I got out a sheet of Depron and started work. Before long, I was able to report some progress:

 

Hello Mike,

 

Herewith promised photo update. Not for publication at the moment, please.

 

Motor mount and V-tail/canard more or less sorted, u/c progressing.

 

However, I just did the sums and it seems that I need an 80mm servo horn to achieve the required wing shift! The horn was always going to be a custom job, since it needs three pushrod attachments to drive the wings, nose/tail wheel and motor reversing switch, but I hadn't realised it would have to be quite this big. I suppose I could make a ply bellcrank instead, but then I have to fit in four pushrods without them fouling each other - and sort out yet another mounting and pivoting arrangement.

 

I am trying to avoid fixing the u/c permanently until after the first flight trials (hopefully over long grass!). Likewise, the wing sliding mechanism will wait until I know where the wings have to be for each flight mode. I still have to work out how to build the wings so that they can be attached temporarily (but securely) for flight trials, then re-worked to attach to a sliding mechanism.

In the (unlikely) event that this all works, I shall of course be looking to you to produce the mechanically and aesthetically improved Mk II - and a full set of drawings...

 

After this promising beginning though, the problems started. It was a full month before my next e-mail update to Mike:

 

Project X progress has been fitful to say the least and each time I have managed to get back to it, I seemed to hit another snag. However, as you can see, I have at last managed to fit it all together after a fashion, albeit somewhat temporarily.

 

The wings have to move an alarming amount in order to get a reasonable cg for the two flight modes. At the moment there is provision to peg them in two positions about 100mm apart, but the long servo arm is only capable of moving them about 90mm. I am hoping that test flights will enable me to move the cg back a bit in one mode or the other, but we shall see. The wing rigging angles also need to be fine tuned for the two modes.

 

I had lots of problems getting the maingear positioned with respect to the cg to give a reasonable prospect of take off in canard mode. As a result the noseleg now looks a little short. Also it is by no means clear to me that the canard mode will be controllable in flight at all so, until this is put to the test, I am reluctant to refine things any further.

 

I still have to fix the v-tails onto their pivot rods, secure the u/c properly and do some transmitter programming, but could be ready for a foray from Thursday evening, if the weather calms off a bit. The mounting of the two props also needs sorting out but, for test flight purposes, I would be prepared to reverse the prop when changing modes - if I remember, of course!

 

(These two pictures will enlarge)

 

The plan was to do initial test flights outdoors before sorting out the wing moving mechanism. However, at this point the "Summer" of 2007 set in and ruled out any prospects of flying in the near future. So I carried on and completed the mode changing mechanics. After much tinkering, I was able to do a successful indoor ground test. (Click on Video Clips below to see it).

 

So, sixteen years on, I had at last built my reversible aircraft!

Of course, one key question remains..... Part Four