built by Shaun Longhorn
Shaun had always liked the PML Bullpuppy kit. At first I put him off (I'm his Dad BTW), by buying him an Estes Bullpup kit, because I didn't think he was ready for HPR. Steadily though he proved his point by scratch building various rockets and flying them, under supervision, on up to F power. He would need a license to acquire before he could use composite motors himself. So at Brass Balls 2000, he, and a number of the other fliers, finally wore me down and I let him buy the kit, it was mostly his money anyway. It sat for a long time doing nothing, but eventually he got his act together and built it.
Constructions wasn't too different from a standard build. The only real difference being the addition of a retaining ring, and motor mount adaptor. The kit had phenolic body tube, so the spiral needed to be filled and sanded. I think this was the chore that delayed the start of construction for a while. He used two part Ronseal exterior wood filler, which is easier to sand than P38 car body filler.
He was particularly careful with the internal fillets on the main fins, applying epoxy to both where the fins emerged into the boat tail and where they joined the motor mount. Both '5 minutes' and 'two ton' Devcon epoxy were used during construction.
The Bullpuppy can easily be flown on 29mm motors, and could easilly be lost on many of the 38mm motors. To avoid having to decide which motor mount tube (MMT) to fit, he built an adaptor so the Bullpuppy could be on either. The adapter itself was just a length of 29mm motor mount with a 29 outside diameter (OD) to 38 inside diameter (ID) centering ring fitted approxumately 60mm from one end. The 38mm motor mount supplied was used as normal. One modification was the addition of a quick switch screw fiiting to the end of the mount. This is the piece that is normally fitted to the end of the 29 & 38 mm adaptors in the real kwik switch kit. Here it was fixed to the end of the 38mm mount where it protruded from the forward centering ring. It acts not only as a thrust ring for the 29mm adaptor, but also as the forward centering ring of the adaptor. This has the disadvantage of limiting the length of 38mm hardware that can be used, but with the advantage that we could use all our 29mm hardware.
The retaining ring comes in two parts. These retaining rings are expensive, but can't be beaten for functionality or looks. Motor retention options on the Bullpuppy are limited by the boattail in any case, and why build a scale kit if you're not bothered how it looks? So there really wasn't much choice. We got the retainer from Pete's Rockets when we bought he kit. They're similar to the retainers that you can get from Aeropac. These retainers are fitted over the end of the (MMT). Normally this would be accomplished by recessing the aft centering ring and fixing the retainer over the exposed MMT. With a boat tail this isn't an option, so he sanded off the last few millimetres of the boat tail. This has the effect of slightly shortening the boat tail, but it also increases the size of the opening. He sanded back until there was just enough gap between the MMT and the boat tail to take the fixed part of the retainer. To complete the motor retention for the 29mm adaptor he used an aluminium disc to asapt down the screw on part of the retainer down to the size of the 29mm motor. This was made from a 'pog keany', that happened to be the right shape, but it's just an aluminium disc and could be made from aluminium sheet.
During construction Shaun had decided that he wanted to fly the rocket himself and not have it flown for him, and whil he was at it to certify UKRA level 1. This would require a license to acquire and keep, so that he could handle the composite propellant, and that he built the rocket himself. That wasn't a problem as he had built it all himself. The license was applied for and received. In the UK you need to be over 16 to get a License to acquire and keep, but the re in no minimum age for a license to acquire only. We think it helped that I had a license to acquire and keep and a registered mode B explosives store. The problem was that he wanted to certify at IRW 2000, and he was running out of time. This was made worse by the fact that he was away on holiday for a fortnight before the event. So in the end I did most of the final finishing. But by then he had built a flyable rocket.
Shaun had left me with the rocket in a flyable state but not an atractive one. The body was smooth and the fillets were on, but looking a little rough. I smoothed out the fillets with a lightweight filler, because I didn't want to add much weight to the aft end of the rocket. Then I primed the whole rocket with Halfords white primer to find where the imperfections were. These were mainly around the fins and the cannards, so I used Halfords filler primer to even these out a bit. It took two applications on the cannards and three or four on the main fins. This was followed by a couple more coats of ordinary primer, sanding between them. The top coat was Halfords diamond white, and went on in just two coats.
The decals suppled by PML had been of the 'stick on' kind, and a little disappointing. Shaun really liked the look of the decals on his Estes Bullpup, so we had ordered upscale decals from Tango Papa. These were excellent, if a little hard to apply. They are very thin, which means they conform very well to the surface you apply them too, but will easily break if you are not careful. I for one think this is a good trade off. After I broke a couple from the first half dozen I applied, I got the knack and had no problems with rest.
For details of Shaun's flights and his UKRA L1 Certification, see the IRW 2000 and other launch reports.