Bede BD8 (oz15876)

About this Plan

Bede BD8. Radio control scale model. Wingspan 29 in, for OS 10 FSR engine. Scale is 1/8.

Quote: "Bede BD8. Dr Mike Hawkins intrduces his small model of a small prototype designed by a large Texan.

This model came about as a result of a search for a suitable prototype to take to Costa Rica for last year's Fun Fly. I wanted something that would go in a suitcase with my other baggage so it had to have easily detachable wings and undercarriage. At 1/8th scale the wingspan is only 29 in, but the deciding factor was the all-moving tail which could unplug, thus removing the weak spot at the tail if the suitcase got thrown around in transit. I already had an OS 10 FSR, remarkably powerful, which fitted nicely. The model was built and has flown in Costa Rica, Florida and again at its home in Bangkok. It is not really a beginner's project as it requires accurate detail work in assembly and is decidedly lively to fly, requiring a gentle and understanding thumb on the stick.

The original aircraft: Jim Bede is a large Texan who became known with his BD 4 high wing lightp!ane. Then came the BD 5 miniplane in jet or piston engined variants. Several are on the airshow circuit in the US but supply of components could not keep up with deposits coming in and the company went bankrupt. At the resulting sale a partially complete BD 8 went for 5260 and was completed and flown at Oshkosh in 1980. The original design included differential stabilator movement to assist roll but the sole aircraft completed, N 88 DH, perhaps wisely, did not include this feature.

The irrepressible Mr Bede is now developing and marketing the BD 10, the world's first private supersonic jet. It has yet to exceed Mach 1, but I have seen it flying at an airshow. Photographs and first rate drawings of the BD8 are in Famous Racing and Aerobatic Planes by Argus Press. The model is designed with no deliberate scale variations.

Construction My usual style of construction is suitable for a scale working model of the Forth Bridge. A real effort in this case to choose light wood and keep the weight down, particularly at the rear end, will be repaid in flight performance.

Wing The wing structure is straightforward with 3 degrees of dihedral and no washout. The aileron torque rods are commercial items, split, and extended by brass tubes, assembled in the wing and then soldered. Only one mylar aileron hinge is fitted as the torque rod makes a perfectly good inner bearing. The front underwing fairing is made from 1/8in. Liteply and contains two captive nuts for the undercarriage attachment. All the Liteply in this model came from leftovers from a Goldberg Extra 300 kit!

Fuselage: Use contact adhesive, e.g. Evostik, to laminate the ply doublers and fuselage sides. The box on Fl should be built up and the motor mount installed before assembly. Fuel tubes will come through the centre of the motor mount. The bend of the fuselage sides at F3 is quite sharp so use water on the outside to help them curve. The stabilator horn and bearing blocks should be installed as the sides are bent in to the tail post. The rear and front decking can then be planked. The cockpit floor, together with the cover over the instrument panel, is essential to the strength of the fuselage. Since there is not much room underneath, the servos are mounted flat with double-sided servo tape. This causes no problem, but seal the wood first.

Tail: I found some 1 mm balsa sheet in the local model shop (1/24 in). This proved ideal for covering the stabilators, fin and rudder as it is essential to keep weight low at the rear end (UK modellers could try SAMS, Tel: 0763 88384 for supplies) Two identical stabilators are made, packing up the LE and TE on the bench. The brass tubes are epoxied into 51 and S2 and must be an exact fit on the horn rods. The rear rod is then bent forward 1/8 in. to hold the stabilator on by spring tension. If it slips, bend the rod forward a little more! The tailwheel moves with the rudder.

Engine cowling: This is a low-tech fibreglass moulding, similar to the process that I described in R/C Scale Aircraft for Winter '85. Once the female mould is prepared from plaster of Paris surgical bandage, I suggest four layers of 6 oz glass cloth laminated up for the cowl. You do not need to save weight here, Elastic Plastic Padding can be used for surfacing and takes paint well. The cowl is attached to hard wood blocks on F1 with small self-tapping screws.

Cockpit canopy: Even though the model is small, the canopy is rather large. The front windscreen is folded and the rear, double curved part cut from a commercial canopy. If you cannot find one large enough you can get near the shape with a 2 litre Coca Cola bottle.

Radio: A Micron mini-receiver is fitted to the cockpit floor with Velcro, well over to the left in order to clear the aileron servo. Although not cheap, the HiTec HS 80 mini servos are quick and powerful. Although they are small and light, don't scale down the control surface horns or you will get far too much movement. A 270 mAh battery is wrapped in silver duct tape and held under the motor box with a nylon tie-wrap. The weight is needed forward and capacity is adequate for at least four tank-fulls, maybe much more. Control throws These are quoted on the plan. Do not exceed the stabilator movement of 1/4 in. at the trailing edge.

Motor: The OS 10 FSR is no longer available, however, the 10 FP should be similar. The silencer duct was shortened and slightly angled to get the silencer fully inside the cowl. An enlarged vent had to be cut in the bottom of the cowl to assist cooling. An APC 7 x 4 prop proved fine as these small motors like to run at high revs. Aerobatic performance was noticeably better on 10% nitro fuel rather than my usual straight mix. An SC 12 would fit and should give good performance.

Centre of gravity: Most of my models with a symmetrical wing section fly perfectly well with the CG at 30% chord. Not this one! Perhaps Martin Simons can explain why it is necessary to have it at 23% on the BD 8, but screw lead to the engine mount if it comes out anywhere behind the point shown on the plan. You have been warned.

Finish: The model was covered with Monokote and the cowl painted with Hobbypoxy.

Colour scheme: If you want to paint it in colour lozenge scheme, go ahead, but there was only one BD 8 and that was white with green, yellow and dark red trim! These colours have narrow black edging, which makes a lot of difference to the appearance. I drew out the trim shapes on the plan and traced them in reverse onto the back of vinyl coloured sheet. This was then cut out and stuck onto black Solartrim sheet. The Solartrim was then cut out and carefully placed on the model. If the results were not perfect, that was my fault, but it looked good enough from a distance..."

Bede BD8 from R/C Scale Aircraft December 1996.

Direct submission to Outerzoone.

Supplementary file notes

Article pages, thanks to RFJ.

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