Home     Updates     Hydros     Cars     Engines     Contacts     Links         Contact On The Wire

Historic Hydros 

OTW. Any detailed investigation into the world of tethered cars and hydroplanes soon reveals that many of the participants were heavily involved in more than one of the activities. Several well known names appear in the records having turned their hands to boats, cars, planes, and even live steam, and not necessarily in model form either. In another of his nostalgic looks back to ‘The Good Old Days’ R.T. Pole gives a detailed insight into the model boating activities of the well-known author and pioneering aero modeller, Captain Bowden.

Jildi Junior
 by R.T. Pole

 

In 1933 Captain C.E. Bowden turned his attention from model aircraft to model speedboats, with the intention of seeing if the application of model aircraft principles, in both design and construction, would help to forward the performance of the then smallest class of hydroplane, that is those under 7lb total weight.

In advance of these experiments a metre boat Jildi fitted with a 30cc Atom III two-stroke petrol engine was built to gain operating experience. A reasonable performance was obtained and in 1934 plans were drawn up for a smaller version to be called Jildi Junior. This was of very light balsa construction, 30in. long and 6in beam; the planning angles were rather coarse with the V shape of the forward hull carrying through to the step. The whole design proved unstable and was scrapped.

A return to the drawing board resulted in the design shown in the plan, (below) Jildi Junior II. With finer planning angles and greater beam. Not being an engine builder himself, the choice of a power unit was limited to a commercial model aircraft engines of which the Westbury designed Atom Minor, manufactured by A.E. Jones Ltd, was deemed, with modifications, to be the most suitable.

Modifications included opening out the ports and fitting of a simple carburettor as designed by Mr Andrew Rankine (builder of the highly successful Oigh Alba). To compensate for the increase in revs a stronger contact breaker spring was also fitted. The Atom Minor was a two-stroke air-cooled petrol engine of 1in. bore and 1.125in. stroke, giving approximately 15cc and was of side port configuration. Final tuning of the engine was carried out by Mr Rankine.

The hull was to be as light and strong as possible and the illustration shows the general detail of the materials used, cross section and method of construction. Durofix glue was used throughout the construction and the complete timber framework waterproofed with cellulose varnish, before being covered with thin model aeroplane jap silk. After drying, the excess silk was trimmed off with sharp scissors, a coat of full strength model aircraft dope was then applied to shrink the silk, followed by two coats of paint and one of clear varnish.

Hull lines from FJ Camm 'Model Boat Building' Part built hull by S.A.C.Smith of Electra Engines

The engine mounting consisted of two alloy angles bolted to the crankcase with through bolts, then screwed with coarse wood screws to longitudinal ash bearers. A small knuckle joint took the drive from the end of the engine crankshaft to a 3/16in. dia. Silver steel shaft, which connected directly to the propeller, no universal being regarded as necessary. The prop was 3in. dia. two-bladed and of 9in. pitch, constructed of sheet steel brazed to a phosphor bronze hub. Forward thrust was taken by a small ball-race, which ran against the rear of another phosphor bronze bearing, fitted to a 1/16in thick brazed steel skeg. The propellor was held in place with a grub screw and a streamlined dural tail piece. No propshaft tube was fitted as the shaft ran directly in plastic wood filler, which plugged the slot in the rear hull floor, a dural plate locating the shaft as it entered the engine compartment.

To the rear of the main cockpit a smaller compartment housed a 4½ volt dry battery, this was housed in oiled silk during running operations. Fuel was supplied from a 2½in. long x 1½in. dia. brass tank, which was pressurised with a football bladder during starting up operations. The mandatory single line attachment was made to an 18swg, multi position clip, adjacent to the engine cockpit.

The total weight, less fuel, of 6lb. 4oz. was well within the Class C weight limit for the Model Engineer Speedboat Competition. The result of this work was an average speed for the 300yd. run of 24.78mph. This was confirmed as a new World Record for this class of boat as the 17.05mph. of the second placed model had been regarded up to then as a good speed for so small a model.

Having proved his ideas with Jildi Junior II Captain Bowden appears to have reverted to model aircraft although not before constructing and testing two more models in 1937. One was a 40in. long all balsa boat with a multi stepped hull powered by a 25cc water cooled two-stroke, the other a tiny boat fitted with a 2.3cc petrol engine which was run free and stopped with an aero type time switch.

In conclusion it is worth re-telling the story of when the good Captain was asked by Edgar Westbury the origination of the name Jildi. He explained that it was an Indian Army term in Hindustani for ‘put a jerk in it’ or ‘go quickly’, which no one can possibly deny that it did.

Right: Col. Bowden at Victoria Park with another version of Jildi Junior

OTW Update. Jildi Junior was passed into the care of Lieut. Cmdr. Alwyn Greenhalgh to join his amazing and well documented collection of vintage model aircraft. He was a prodigious model engineer and author, and responsible for saving a huge number of early models that may well have been lost forever. His writings can be found in all the contemporary modelling publications along with examples of his restoration skills. Jildi Junior underwent a total restoration in his hands to what is now described as 'concours condition'. The later 'sponsons' were removed leaving the hull in its original single step configuration with the engine and fittings as described by the 'Captain'.

Alwyn Greenhalgh sadly died a few years ago but unlike many recent cases, his collection was not broken up and along with Jildi Junior, has now been passed on for safe keeping.

Thanks to Tim Westcott for relating the later history of Jildi and providing the photographs of the boat in its current state. Additional photos courtesy of the Westbury family. Photo of part built hull by courtesy of Ken Smith

©copyrightRTPole&OTW 2006