In the late 1940s, I was a member of the Epsom and District Model Aircraft Club; and around twelve years old.  At about that time a new type of engine appeared, a solid fuel rocket motor named 'Jetex'.

The motor comprised a tubular shell with a sprung loaded end cap with venturi.  The fuel was a solid cartridge lit by a length of fuse which ignited the end of the cartridge; this then burned at a controlled rate giving off enough gas to give a few ounces of thrust, with a burn time of between 30 secs and 1½ mins.  Some 'whiz' soon found that by taking the fuse along a groove made in the cartridge it was possible to ignite both ends of the cartridge at the same time, which although halving burn time, doubled the thrust !

Record Attempt

A rash of aircraft designs appeared for the new engines, and the Club decided to attempt to break the Indoor Tethered Flight World speed record.  A room in our headquarters (the local Scout Club) was set aside and a tripod pole and wire tethers were set up.  A rocket powered tail-less design was chosen, with a wingspan of about 5".  All members (about 25) crouched around the walls of the room, and trial flights began.

Very soon there was a thick fog of burnt fuel in the smoke filled room.  Flight after flight with small changes in trim were made, and soon the model was just a blur in flight.

An official timing session was set up and the speed record achieved !

Next was an attempt at the Indoor Tethered 'Floatplane' record.  Someone in the club made a tinplate radial water tank about 12" wide by 6 ft long.  One evening during trimming flights with all members in the room, the wire tether (control line wire) failed, and the model crashed into one of the walls removing a large chunk of plaster - fortunately managing to miss all members surrounding the flightpath - white faces all round !

All subsequent flights and record attempts were made with only the model operator and timing marshal present, and they had the protection of an upturned heavy topped folding table !

During the war, having seen Vl flying bombs passing overhead, making a sort of burp-burp-burp-ing sound, (if the engine stopped find somewhere to hide quick !); my brother and I tried to make a pulse jet engine.  The engine had a rose petal valve at the end of the combustion chamber, made from steel shim.  Sadly, the best we ever achieved from this was a few coughs and bangs, and a sheet of flame from the rear pipe!.  We didn't have a good enough grasp of the principles involved to make further progress.

A couple of Canadian friends, (twin brothers) decided to build a rocket powered model of Campbell's record breaking speed boat.  It was very quick riding on its sponsons but was prone to capsizing on encountering the least wave formation.

Hmmm !