RM EXCELLENCE

Shaun Garrity returns to the 1980s with the low-wing classic design from David Boddington

The high wing Whisper and low wing Excellence were designed by Dave Boddington in the mid 1980s for the new breed of small four-stroke engines that were starting to appear, specifically the latest O.S. FS-20.

Dave noted that choosing names for his latest creations could be quite time consuming, but this wasn’t a problem for this model; Excellence was the name O.S. had given to their new range of engines, so it seemed appropriate and fitting to call it just that.

Whisper was conceived as a 3-channel (rudder, elevator, throttle) trainer, with the potential to add ailerons later. However, the 4-channel Excellence was designed to be capable of advanced aerobatics with no modifications.

Early four-strokes were less powerful than their equivalent two-stroke engines so lightweight construction was important and a quick look at the plan will confirm this. The power gap was such that Boddo suggested using a good .15 size two-stroke as an alternative.

He also stressed there were no problem areas in the construction and any modeller with a couple of projects under their belt will breeze it.

A BODDO SNIPPET

In the late 1960s Boddo designed and built a full-size BE2c replica for a Biggles movie. However, for financial reasons the movie was never finished, but the aircraft was. The BE2c was eventually sold to an enthusiast in America who regularly flew and displayed it. Where am I going with this?

Well, in 1977 Boddo was contacted by the BBC about a twelve-episode TV series to be called Wings. The conversation basically went as follows: “Would you be interested in building some 1/6th scale models? We would like a couple of BE2s, a couple of Albatros 1s and a couple of Avro 504s. Oh, and we need them in six weeks please.”

It was a good job Boddo had a team of modellers willing to help with the building. A little further down the line, after much negotiation, the BBC mentioned they would like the BE2s to look like a full-size replica they had filmed in the States and Boddo realised this was the aircraft he had designed and built years ago.

There was a small problem though as the full-size aircraft wasn’t an exact scale replica. This meant he needed to modify the scale models he had just built by tweaking the nose and building a new tailplane.

Now we come full circle; years later it was Matthew Boddington who was involved with the restoration of the full-size replica BE2c (it had crashed and been abandoned, and I believe Matthew brought it back to the UK).

It was Matthew, too, who built and flew the prototype Excellence featured in the original article. If you have access to the April and May 1977 issues of RCM&E then there’s an interesting two-part feature about Wings detailing the full story.

MORE WINGS & THINGS

Different in design to Whisper, there is no leading-edge sheeting so, to maintain profile, sub-ribs are used instead to prevent the covering from sagging. Being parallel chord the ribs can easily be made using the sandwich method.

The wing is built in two panels and the only modification I would suggest is using a servo per aileron rather than the old way of just one in the middle as shown on the plan.

Start by pinning the lower spar in place, gluing the main ribs using PVA or aliphatic; you will need to pack up the rear of the ribs to the correct height. Add the top spar, and leading and trailing edge pieces. The sub-ribs can be slipped in diagonally, then glued in place; don’t forget to position the root ribs to achieve the correct dihedral angle, then add the ply dihedral brace.

Wing tips are shaped from soft 1” triangular balsa block. Add the shear webbing as this imparts significant strength and resistance to twisting. Use medium hard balsa for the ailerons.

The tail group is built up to save weight but note the use of 3/16” spruce to stiffen up the centre section of the tailplane. So don’t omit this.

FUSELAGE

Nothing too complicated here. It’s a little more involved than your basic boxy trainer but shouldn’t cause any problems. Whisper had a cowl moulded from ABS, Excellence uses good ol’ balsa to make things simpler.

You will need to decide how you want to power it before starting to cut wood. If going electric check F2 is positioned to get the prop driver in the correct place. You can obviously omit the engine bearers.

Cut the sides from medium 1/8” balsa then accurately glue formers F2, F3 and F5 in position. When dry, jig up or use a simple line on the building board to accurately form the rear fuselage. I would bind the tail skid to F8 now as it will prove difficult later if you forget. Glue in the 1/8” x 3/8” stern post and when dry sheet the rear lower and top fuselage with 1/16” cross grain balsa. Then glue on F6, F7 and the 1/8” x 3/8” top stringers.

Use 1/8” marine ply for the undercarriage leg retainers, noting that the angles for the slots differ on each side. Not far to go now just the front lower 1/8” ply and 3/8” block and the top decking from 3/32” sides and 1/8” as detailed. Form the tank hatch. If going electric you could modify this area, adding a battery tray allowing easy access for changing the LiPo.

Once you’ve fixed F4 and the canopy fillets in position you can get on with the glazing. The canopy doesn’t require a moulded item as it’s made from acetate sheet. Boddo suggested mocking up the shape required first from card to get it spot on.

I would suggest fitting the canopy after painting and decorating. Add any remaining balsa and ply parts detailed on the plan, round off the nose to suit a 2” spinner and the job’s done.

RADIO

No problems will be encountered here as modern gear is so much smaller than that available in the 1980s. Although the elevator is shown having an internal connection on the plan, if you don’t like that method then go external. Pushrods, snakes or pull-pull on the rudder will all work well, just ensure the hinges are free and nothing binds.

Standard sized servos can be used for rudder, elevator and throttle (for IC) but modern micro-size types (around 15g) will make life easier, especially when going electric and finding a home for them in the fuselage alongside the flight LiPo. As mentioned, I would use a micro servo per aileron as this will also allow you to program flaperons if required.

FINISHING

The prototype was covered in a Solartex (possibly Polytex, like the Whisper) but modern heat-shrink films will work well as the wing is pretty rigid in its uncovered state.

Due to the demise of Solarfilm I’ve recently used the Hobbyking range of films with great success. They have great shrink, mould round curves well and appear not to slacken off on hot days.

Whatever covering system you use keep it as light as possible and pick a colour scheme that aids orientation.

TIME TO FLY

Check all the usual things such as C of G, the control surfaces move as expected, nothing binds, servo and surface horns have been tightened up and the wheels don’t bind. Boddo noted that Excellence

“…had good positive control response but was in no way twitchy. She can be pulled around the sky in tightly banked turns without fear of high-speed stalling and it’s possible to fly a display routine in a very small box of air. Inverted performance is fine, and Excellence will execute flick manoeuvres.”

One point he made was not to over-power the model and even suggested that if using a hot .20 two-stroke then nylon covering was highly recommended.

The black and white images were kindly provided by Andrew Boddington and my thanks go to him.

If you want to buy a copy of the original Radio Modeller plan then it is still available from Sarik Hobbies:

RM299 Excellence


www.sarikhobbies.com

DATAFILE

Model: Excellence

Model Type: Aerobatic sportster

Designed By: David Boddington

Wingspan: 47 ins.

Wing Area: 412 sq. ins.

All-up Weight: 37 ozs.

Wing Loading: 13 ozs./sq. ft. (approx)

Rec’d Engine: 2.5 – 3.5cc, 2 or 4 stroke

Functions: Rudder, Elevator, Aileron, Throttle