I have always admired the Dynaflite 'Bird of Time' since seeing a superb example built by Ken Spokes. During a conversation with Jim Ruffell on the way to Sandown it turned out that he had a new kit which he did not have time to build, so a deal was done whereby he gained a motor which I had no immediate use for and I gained a B.O.T kit, (see Chairman's Chatter, June 2003). I then searched the Internet and found a building and flying article on the 'Charles River Radio Controllers' site by Pete Young (You can find it, and plenty of pictures, at http://www.dynaflite.com/reviews/dyfa4502-rcr.html - Ed). The only criticism of the kit was oversize wing joiner tubes leading to slop in the location bar. Sure enough when I examined my kit parts the same problem was there. I'm thinking of asking Jim for a discount due to the defective kit he foisted on me. I solved the problem by substituting the defective parts with brass tubing of the correct size.
The rest of the kit consisted of dozens of die cut parts and various strip and plank sections all of an excellent quality. There was a very comprehensive manual and parts list, also a large two-sheet drawing. To give some idea of the kit size it took me all of one evening to check all the parts against the inventory. This really is a builder's kit and as far away from ARTF as it is possible to get.
I do not to intend to make this a blow-by-blow account of the build, only a precis of the relevant points. The first of these concerns the build sequence as laid down in the manual. The instructions require you to make the inner and outer panels of one wing together, also not to assemble the L/edges and T/edges at this time. I feel that this leaves a weak structure to remove from the building board; also it does not allow you to align the wing joiner tubes together before finally epoxying them in place. Having regard to this I built the two inner panels together with the trailing edges attached. This raised the first problem as, with the joiner tubes duly chamfered per the manual and touching the top and bottom spars, I could not achieve the specified dihedral (Perhaps the extra dihedral comes from the slop in the joiner tubes! - Ed). As I did not fancy reducing the cross section of the spars I was forced to accept the dihedral reduced to about 75% of the original. Only time will tell what effect this will have on the turning performance. Another problem concerned the material for the leading edges. This turned out to be too small in section to achieve the proper shape, so I had to raid the piggy bank and purchase some new ones. I must have a quiet word with that Jim? Other than this the wing build proceeded without any more problems. These wing assemblies alone took twenty-five hours to complete and they had not been covered yet. One addition that I did make was to fit airbrakes to the inner wing panels. If you have ever tried to land a three-metre floater without airbrakes you will know why I added these. I used proprietary Multiplex competition items to which I added spring returns, a method I successfully employed on my 'Algebra'.
The stabilisers, (tailplanes to you) are of unusual design. They are built by bending 1/4" x 1/16" balsa strips over and under a central spar and gluing them to the leading and trailing edges, thus forming a symmetrical section. This turned out to be fairly straightforward and both stabs were completed in about four hours. The fin and rudder posed no problems although they appeared to be on the heavy side as kit built. I think a useful weight saving could be made by the use of lighter materials and perhaps laminating the curved surfaces as on the Lazy Bee.
On perusing the fuz plan prior to starting the build, I noticed that the position of the tow hooks looked all wrong, being almost vertically under the C of G. The normal position is usually at an angle of thirty degrees in front of this. A quick call to Ken Spokes confirmed that when he used the planned tow hook position on his BOT the model was almost uncontrollable on a bungee, although he said that it would probably be okay on a winch launch where you can keep tension on the line all the way to the release. As this is an American design we concluded that the kit was indeed designed for winch operation. I therefore made up new extended reinforcing plates to enable the tow hook to be moved to a more normal position. Another problem arose when I attached the sides to the bottom blocks. The reinforcing on the sides only extend half way along the length of the fuz and no provision seems to have been made on the bottom blocks to accommodate these. The only way out was to make up some packers of the same thickness as the doublers. After this no other complications arose from the fuz build. I made up a servo mounting tray as nothing was included in the kit and replaced the very heavy control rods supplied with one lightweight one and a closed loop system for the rudder.
It took a long time to decide on a colour scheme for the BOT.
I really wanted something new, which I hadn't used before. I was
also keen not to cover up all that beautiful woodwork, so I settled
on transparent violet for the open sections and gold/yellow for
the sheeted sections. The fuz was primed and painted bright red.
At least I should be able to see her at a reasonable distance.
All the covering material was Profilm as it is remarkably easy
to use although it is not cheap. It cost me £35.00 for the
three rolls that I used. The covering took six hours to complete.
(to be continued)