This model is a semi scale rendering of the Percival Mew Gull and appeared as a free plan in the February 2002 edition of RCM&E.
As presented, the plan is for a .40 - .61 sized engine (although the review model used a .90!) and has a quoted all up weight of 7.75lb. For a 61.5inch span model, this seemed to me somewhat heavy and I was surprised to read that it apparently flew well at this weight. Looking at the plan, it is hard to see how it could weigh so much (a lot of noseweight, perhaps?) and I convinced myself that, even with 16 - 20 cells on board, an electric version should still be well within that weight limit.
I contemplated various power options and the longer I thought about it, the more expensive the preferred option became! Eventually I came back down to earth and the recently repaired Aveox 1406/4Y sitting on the bench doing nothing, was chosen. Decision made, I ordered an MAT belt drive gearbox, bought a load of balsa wood and cleared a space on the workbench.
Fuselage (part 1)
Using the published dimensions of the gearbox, I was able to establish that the firewall could be relocated further forward (which gave a bit more flexibility over battery location) so I cut out a pair of fuselage sides and built just enough of the fuselage to be able to attach the wing as an alignment reference. The tail end was then pulled together and work started from that end.
The solid sheet tailplane and elevator were of course replaced with built up components, the fin and rudder being built more or less as per plan. Because the rudder is attached both to the fin and the lower fuselage, it has to be removed before the tail and fin can be lifted off. Pinned hinges were therefore used. Fin/tailplane fairings are 1/16 sheet rather than shaped block.
Fuselage (part 2)
From this point, the construction order was a little unusual. With the gearbox still delayed, the flying surfaces were covered and, yes, the wing fairings and canopy had to be tackled. I even made a start on the spats. However, I couldn't find any suitably slim wheels, so I opted to make my own by the Mike Payne method.
Then I was offered the loan of a demo model of the gearbox so that I could get on with building the front end of the Gull. A trial balance indicated that the battery may indeed have to be located well forward into the nose area (although the cg position marked on the plan does seem a long way forward). I therefore made a big hole in the firewall before fitting it.
The MAT belt drive gearbox is made for beam mounting and also has holes for bulkhead mounting. After much thought, I went for a combination of both. The gearbox is mounted onto a bulkhead and this is firmly linked to the original firewall by two beams which fit snugly against the gearbox, but are not actually attached to it. This arrangement enables the top of the fuselage, forward of the access hatch, to be fixed, a small detachable lower cowling giving access to the motor and gearbox. For the moment, the beams are not glued in position - just in case a change in powerplant is needed at some point.
The picture shows the general arrangement. The top of the nose section was planked in with 2.5mm balsa to blend in with the aluminium spinner, and the lower fuselage sheeted in up to the mounting bulkhead. A 'chin cowl' was then made out of 6mm balsa.
As I was cutting a neat cooling hole in the front of the cowling, I realised that there was nowhere for the air to get out. Cutting exit holes at the rear of the cowling would let the air out before it even reached the motor, so that was no good. In the end, I cut a hole in the bottom of the fus behind the wing, so the battery and ESC should hopefully see a bit of draught too.
With the fuselage complete and covered, with just the cockpit to fit out, the gearbox eventually arrived. This gave me the impetus to find and fit a pilot, finish off the instrument panel and do a power test.
At this point, the model was complete apart from the spats and trousers. As a way of putting off this job a little longer I opted to fly the model first, on the grounds that I could at least check out whether any adjustment to the forward rake of the undercarriage was needed.
Landing was uneventful and, all in all, first impressions were of a well-mannered aeroplane. A second flight was pretty much a repeat of the first, so it was back home to sort out the powerplant, the aileron trim - and the spats and trousers.
At this point, the English Summer took a break and we were lashed by a week of rain and gales, so eliminating my very last excuse for putting off the dreaded spat building. Like so many things, once I forced myself to face up to the job, it wasn't as bad as I feared. However it did seem to take forever. The result though is well worth it, as I hope the pictures show.
So, with the 14 cell 2400mah pack on board, the model weighed in at a shade under 6lb, complete with spats. The performance with this setup is pretty sprightly, large loops being possible from level flight. The need for aileron trim seems to have gone away, so my wing warping session clearly achieved something. At present I am still progressively increasing the flight duration, and it is clear that 8 minutes of gentle aerobatic flight is easily possible, so maybe the motor isn't working too hard after all. Time will tell.
I am well pleased with this project so far and will fly the model for a while in this configuration. If I do eventually feel the need for more power, it is nice to know that the model is curently 28oz below the weight of the i.c. prototype!
Seven Years On!
Ten years on, and the Chorus Gull has been granted a new lease of life as a floatplane! Read all about it in this article.