Bede BD-5

Shaun Garrity updates a plan for a small pusher, jet style model that doubles up as a stiff-wind slope soarer

What has a Jaguar XJ6 (with the roof cut off), a steel pole and Octopussy got to do with this month’s free plan? Back in 1967 Jim Bede and his chief designer Paul Griffin sharpened their pencils and started creating a design for an aircraft that would become the BD-5, also referred to as the Micro.

At the time Jim was working on the BD-4, which was essentially the world’s first homebuilt aircraft offered in kit form and a traditional looking light aircraft. It is still one of the most popular home-built planes in the USA (and many other countries), with thousands of plans sold, and with many hundreds built and flying.

The BD-5 however was another kettle of fish with its single seat, fighter jet inspired design, large Plexiglas canopy and pusher propeller. The BD-5 project was revisited in 1970 with a view to build a prototype by the year end. The design brief was again to produce an easy to construct, home build aircraft that required no welding or specialised tools.

It was essentially an aluminium frame skinned with fibreglass panels and because the wings were easily removable the aircraft could be stored in a garage and transported on a small trailer. The low drag design could achieve almost 200mph on the 40hp engine, with a range of over 1000 miles; it was cheap to run as well being very frugal, achieving around 30mpg and available in two wingspans of 21 ft 6 in and 14 ft 3 in. The smaller wing was intended for aerobatic pilots.

During 1971 the company received over 4,000 orders making it one of the most popular kit-built aircraft ever.

JAG & CEPHALOPOD

Jim also developed a 17-foot wingspan, jet powered version of the BD-5. Called the BD-5J (aka the Acrostar Jet) and powered by a Sermel TRS-18-046 turbojet it could achieve 300mph. Unfortunately, this variant didn’t have a great safety record, with a number crashing, but pilot error was generally the cause not structural – wrong fuel, incorrectly assembled wing panels to name but a few. It did hold the honour of being the world’s smallest jet for 25 years, according to the Guinness book of Records, so what has a Jag and an eight-legged Cephalopod got to do with the Bede?

The answer is James Bond, 007, licensed to kill. Roger Moore is seen in the opening scene of Octopussy flying through a hangar in a Bede BD-5J. Obviously, this didn’t really happen; some of the flying scenes were done with the real thing, but the rocket attack was simulated using a third scale R/C model (with fireworks simulating the rockets) and entry and exit flying scenes from a third scale hangar door. The internal hangar shot involved some out of the box, special effects thinking…

Butcher a Jaguar XJ6 by chopping the roof off, weld a vertical steel pole to it with a tilting mechanism, bung a full-sized Bede atop the pole, then you can safely drive it through the hangar without fear of it crashing – simple, eh? Oh, and don’t forget to shoehorn Roger Moore in the cockpit for the cameras. The car and pole were cleverly disguised by placing props, objects and actors in the foreground – there was no CGI back then!

THE MODEL

In the 1980s John Rutter designed a number of great looking, quick build models that followed a common theme – they had solid balsa wings. John’s inspiration to model the Bede came from one he saw on static display at Farnborough in the late 1970s, but he didn’t (in his words) “get the bit between his teeth” until he bought a 1/72nd scale plastic kit early in 1986, when he “dusted off a Cox TD 051 and got busy.” I’ll let him describe his prototype:

“My models are invariably pretty simple to build so a week later it was ready to fly. I had one or two problems with it at first caused by that fat (for the size of model) fuselage and the high mounted engine. It was distinctly tricky to launch, the motor pushing the nose into the floor. So, rather than break it, I chucked it off the local cliffs! The problem became immediately apparent; the CG was too far aft. The other problem was tip-stalling but twisted-in washout soon cured that.

The model was now transformed into an exciting and acrobatic power/slope soarer depending on the strength or direction of the wind. The only deviations from scale that I know about are that the motor fairing is a little fatter than it should be to hide the fuel tank and the wing has 1/2″ more chord to give a little more area. The real aircraft has strip ailerons and used a tail plus elevator set-up experimentally, though it now has an all-moving tail.”

WING BUILD

I would start with the wing because it’s quick and easy to fashion. It’s basically a sheet of medium 1/4″ x 4” balsa with a couple of triangular off-cuts added to get the correct wing shape. The whole wing can be made from a single sheet. Make sure the sheet is straight grained and warp free. Before cutting out the ailerons you need to carve and sand the washout into the end 6” of each wing; this is important as it’s necessary to prevent your Bede wanting to spin when you don’t and it needs doing before you carve and sand the wing to an aerofoil section.

Once this is done cut the wing into two halves and liberate the ailerons. You will need to make the torque rods from 16g piano wire and brass tube. To connect the servo, I soldered the brass balls from a ball joint connector to the piano wire – have a look at the photo. Alternatively, you could solder on some brass tube, flattened and drilled to take a quick link.

On John’s model the ailerons were top hinged, so you’ll need to profile the edge to allow for the correct movement. Since I modified the original design for e-power and four functions (ailerons and elevator are the minimum required) and used 9g servos, I repositioned the servos to be mounted as shown. You will need to make a small hollowed out balsa blister under the wing to cover the bottom of the servo.

If you are going to cover the model in heat shrink film, then leave out the wing locating dowels until after this has been done. A small fibreglass (or ply) plate is fixed on as shown after covering to prevent the wing bolt from pulling through on any less than perfect arrivals.

TAIL GROUP

Use medium 1/8” balsa here and just run sandpaper over the edges to remove the sharp corners. I hinged the rudder and elevator with Mylar (roughened), glued in place with slower setting cyano. Old school stitching or film/tape hinges would also work fine. I added a rudder, but it flies perfectly well without it.

Again, if you are film covering the model then do it now but don’t forget to remove the film where the glue joints are.

FUSELAGE

Although this is a simple model there’s some old school aeromodelling involved in the build, as the fuselage top, including the canopy, are planked. If you’ve not tried this technique before there are options if you don’t fancy having a go but it’s not hard. You could alternatively shape it from hollowed out blue foam, covered in glued on copier paper or skinned in 1/16” balsa. Or add a few stringers and sheet in sections of soft 1/16” balsa – just don’t make the rear end heavy.

Another issue highlighted by John in his original article was that there isn’t a straight line on the fuselage so you could build it in two halves (top and bottom) then join, but as long as you draw a reference line down the building board and make some basic jig pieces it shouldn’t be problematic.

This Bede was built for me using John’s method by my good friend, Gary ‘the ex-Australian’ on his narrow boat. Start by marking the former positions on the inner fuselage sides, then glue F3 and F4 in place and when set draw the tail end together, checking everything is square and true, then the nose, fixing F1 in place. Now glue in F2, F4a and F5 and tack glue the canopy formers in place.

Time to plank, so strip some medium soft 1/8″ x 3/16″ from a sheet. Start at the top and work your way down, trimming the planking strips as required to produce a good fit with no gaps. I would suggest a combination of cyano to stick them to the formers and aliphatic for the edge joins because aliphatic sands well when dried. Don’t forget to fit the rudder and elevator pushrod outers in place before planking.

You can now add the lower fuselage 1/2” front, 1/4” rear balsa sheets (not forgetting the ply reinforcing plate for the wing mount) and nose block, then start attacking it with sandpaper etc. to get the desired shape. Please use a mask when sanding. You can then cut away the canopy, but if you forgot to mark out the position then it may be an interesting exercise…

RADIO INSTALL

It was luck that the C of G came out correct with the LiPo I intended to use but if you follow my install it should work out for you as well without resorting to any nose weight. The E-Max motor on my model is a little heavier that some similar examples but the rear mount was the perfect diameter for the model as designed.

9g analogue servos have plenty of power; just ensure none of the control links bind when operated and the aileron linkages don’t foul the motor or servo leads with the wing located. I used a wooden coffee stirrer glued on a spacer to keep the motor leads out of the way on the fuselage side.

POWER TRAIN

As mentioned, I chose an E-Max CF2812, primarily because the motor mount was the correct diameter for the model without any modification. This will give around 120 watts of go on a 3S set up and a 5″ x 4.5″ three bladed prop (well, it did on my watt meter) and is more than the TD 051 could produce, so you should have power to spare.

You could get more oomph by using a larger diameter propeller, but I didn’t want mine to clip at the rear when landing. These are great motors but check the grub screws that locate the motor to the mount are secure, but don’t over tighten them as they can distort the bearing if you go all Incredible Hulk on them. A spot of weak threadlock will keep them in place.

A 4-Max 22A ESC and 1500mAh 3S LiPo completed the set up.

COVER UP

You have a number of options with this all sheet model.
The simplest is to just to sanding seal everything, then use rattle can paint. A quick Google search will provide inspiration for colour schemes. Instantly recogniseable would be the Octopussy, Bede BD-5J jet and there’s no reason why you can’t choose this for the prop version featured here, or it would be perfect for the slope soarer.

To give it a little more ding resistance, doped on tissue would be preferable over a simple sanding sealer and paint finish, or just go with good old heat shrink film. Whatever you do, don’t pile the weight on as it flies fast enough as designed.

TIME TO FLY

Check all the usual stuff – C of G, surfaces move in the correct direction and don’t bind; 1/8” each way was recommended by the designer and although this doesn’t seem a lot it is adequate. I had a little more but did dial in some expo. Range the ESC (to ensure full power) and make sure the motor and the propeller combination you’ve used is spinning correctly, blowing not sucking the air forwards. For a new receiver a range test would also be sensible and don’t forget to set the failsafe.

John offered some pointers in his original article:

“The power model needs a healthy motor run and a firm push into wind to take off. The elevator doesn’t have a lot of effect until flying speed has built up. I hold the model just behind the trailing edge to launch. Once in the air the model is fast and aerobatic, and this is where the bright colour scheme comes in useful – it stops you losing sight of the thing! It will do all the aileron/elevator manoeuvres I can think of.

The slope soarer version is obviously lighter than the power job, so needs a 20mph wind to fly well, on our slope at least. I launch by holding the model just in front of the wing and usually just need to let go. (Our slope site is a 200 ft or so sheer cliff). The model performs well enough for a scale job, though it’s somewhat ‘draggy’ and loses speed a bit quickly compared to the ‘kippers’. Both versions were prone to tip stall in very hard turns. Should this happen to your model the cure is to warp in some extra washout or reduce elevator movement.

A wind of about 35-40 mph seems to be about the limit for the soarer, with the motor and balance weight as ballas – after that, penetration is zero!”

Is this the perfect quick build model for all wannabe secret agents? I don’t know, but it is certainly different from the more common scale models seen on the patch.

DATAFILE

Model type: Sport Scale Power or Slope Soarer
Wingspan: 35.5” (902mm)
Length: 22” (559mm)
Weight: 13ozs (369g) exc. LiPo
Functions: Elevator, Aileron, Throttle and Rudder
Power (Electric): Brushless 120 – 150 watts (E-Max CF2812)
ESC: 4-Max 20A
LiPo: 3S 1500mAh

PLANS DOWNLOAD

You can download the Bede plans here:

Fuselage

Wing & Tail