A return to model building and flying. Part 74

September 2011

Sharma Diesel - Update

sharma19Having a spare moment to try the Sharma again, I decided to try a smaller prop to see what happens at higher revs, and also see what effect the muffler has on this setup.

The first thing I noticed was an increase in difficulty in starting. With less flywheel effect and not hearing what was going on so clearly because of muffler, it took a while to find the right settings. Once found starting was reasonable and no worse than any other diesel. The revs were obviously being held down by the muffler and  settings a little more difficult to find as the exhaust not is more subdued.

This was not helped by picking up the wrong fuel can as I left home and using Southern Modelcraft, Hi Performance mix which has 20% oil not the Sport 30%. This should not make that much difference to a recent engine, but not something I would use on an old or vintage one. I had not realised up until this point that the fuel seems to contain kerosene not paraffin, which may explain the black smelly residue that the engine throws out. I have had similar in the past, when I used to mix up my own fuel and blended ordinary multi-grade mineral oil with castor to keep the price down, but it didn't smell anything like as bad as this did.

I was flinging the model around the sky in, not quiet, wild abandon, noting that the smaller prop had released a little more power but was obviously being held back by the muffler, when the engine told me it was nearing the end of it's fuel supply. So I settled in for a few laps of level flight, when something happened that had never happened to me before; the engine shed both blades of a nylon prop in flight!

This caught me by surprise and took a few moment to gather my wits, I don't have engines doing shaft runs in flight every day. I have no idea what revs it was doing, but by sound alone I would guess around 20000rpm. Of course it was still gliding and landed normally, whether this was good or bad thing I don't know, but giving full down to stuff the nose into the  ground as it rolled along did sweet F.A., with the prop nut just trying to drill a hole into the ground, leaving me with a 16metre dash to the model. Then engine stopped itself when I was halfway there.

Expecting the worst, I was frankly amazed that it still seemed to be OK. Compression was still the same, no slop or binding in the crank or anywhere else, and no discernible play in the conrod? Trotting off down the club's workshop and employing the use of a vice and pipe grips to remove what was left of the prop ( there is not much to hold with a prop hub alone )  the model was refilled and flown twice again. The performance was same except the model was vibrating badly, so I called it a day.

Back home, I found the self tapping screws that hold the engine mounting plates in place  (this had been a rush job initially) were not tight, so the vibration may have been cause by this. However as it's not my engine  I returned it to Motorvation Model Engines for J.W. to inspect internally, and also hopefully come up with a slight larger muffler design to release a bit more power. In the event it turned out that the engine started after a couple of flicks and ran as smoothly as ever. Now all we need is to try it with a modified muffler. This also proves that the black residue I was seeing was not burning lubricant or metal, or I don't think the engine would have survived in the state it's in now.

The fact that it survived this abuse stands testament to the right materials and machining being used in it's construction. Now I am even more impressed than before, and I really! really! want a set of these engines.

It's an undefinable thing to describe, but some engines are fun to use and fly, others are not. I think this is what generates such an affection for certain makes or versions amongst modellers in general.

UK Nationals. Huuurrmmph!

I had been in two minds all year whether to enter the Nationals again. This particular national holiday weekend always follows the same pattern. the weather is reasonable the week before, then cold, wet or windy, or a combination of all that for the Saturday, Sunday, and Monday, followed by a fine following week. The rare Nationals are the ones that are not like this. The fact that weather had consisted of an almost a constant high wind since the early part of the year hasn't made me exactly enthusiastic either. Although I have to say it seems to have given me a few good flying days recently.

This year followed the same dreary routine, although the Saturday was tolerable, it was not the sort of  day you would choose to fly if you had an option. The Hellcat was dragged out yet again and managed one good flight. From then on it went downhill.

Sunday presented a stronger wind; but what the hell, I have flown in worse. I decided to fly the Bearcat..... Oh what a mistake! it took off for the fast run OK., then just stopped on the slow run. Too lean I thought. Duly adjusted. another attempt ensued. This time it kept going but with a very strange slow running engine, with lots of strange noises coming from the exhaust which sounded like a misfire or detonation, then another engine failure. With only one flight left the Hellcat was dragged out yet again, and I managed a very untidy flight being blown all over the place, followed by a, not deliberate I might say, kamikaze attack on the deck. At least it stayed on it.

It dawned on me when I was packing things away that I had been using 10% Nirto fuel and alarm bells started ringing about 'early' SC/ASP/Magnum engines being setup for strait fuel. As the SC in the Bearcat had performed flawlessly the week before on 5%, this seems a likely cause and may have been causing pre-ignition hence detonation sounds. This also opens up a whole can of worms with the HP40 I was playing with previously, and may explain why I had such strange problems when trying to throttle it. The paperwork for the HP suggests  a maximum 5% nitro. Yet more work ahead then......?

That was enough; This was not enjoyment. Apart from buying a few things at the trade tents and chatting to people that was my Nationals. Even as a spectator I would not have had much to see. I notice that only Malcolm Ross writing his Teamrace News in the BMFA News magazine seems to have an honest apraisal of the weather conditions we have been experiencing this year. I'm sure some commentators don't live in real world; reading them you  would think the whole event was held on some pleasant sunny weekend with a gentle breeze stirring the long grass with the occasional hum of insects or tweets of birds,as we all sat around sipping at glasses of Pims listening to the impromtu sound of leather on willow from improvised cricket matches. Not sure what event they were at, but it certainly wasn't mine!

A couple of weeks later I discovered that I had come 3rd in Basic Carrier at the Nat's, but I don't really have a sense of achievenment because of it. It was down to who was skilled enough, unwise enough, or silly enough to fly in the conditions, what time of day you ended up flying, and a lottery as to who got the occasional lulls in the wind.

I have always had a strange attitude to competition. I love the competition itself and the work that goes into getting myself and models into a competitive state, but the final result always seems less important for some strange reason; maybe I consider the journey more interesting than the arrival. Flying CL aerobatics, I always knew when I had made a good or bad flight without ever having to look at the score, and it's the same with Carrier. I even suspect if by some chance I happend to win a carier event at the Nat's I would be thinking I could have done that better. I once saw a documentary on Skûtsje racing in Friesland, a traditional shallow daught sailing boat with side boards, the guy that always won had a box where he just threw all the trophies in a jumbled pile; he draged it out and  just said, "They don't mean anything." That just about sums up me too.

A couple of weeks after that I flew the Bearcat/SC40 again. with 5% Nitro fuel this time , and it never missed a beat. That's that theory proved then.

I'm in desperate need of new better design of Carrier model, allied to a tractable engine capable of delivering some horses, but it's no mean feat to start from scratch, I have many ideas, but can't get them to gell into one design as yet. I also hate having half finished models lying around, two at present, one being the Tigercat, I blow hot and cold over this as I am very unhappy about the wing design,  but it is ostensibly finished; so can I be bothered to start again? What I need is a standardised way of making wings. I am half way there, but need a jigging method. Yet more thinking time needed. With my thinking time also committed to virtual worlds in cyber space occupying yet more of my time, this is getting even more difficult. Can I have two simultaneous lives and 48 hours in a day please? I might get something done then. Who wants to live forever? I damned well do!

   Control Line Navy Carrier Information Pack  (2nd  edition 2011)

Republished and featuring moi prominently on the front cover, this is a very useful insight into what CL Navy Carrier is all about and it's origins. My only small critiscism is that most of the information and plans are now dated, with a lot of modern techniques and methods not being covered at all. Notwithstanding, very worthwhile having for ideas and insights, and also an included free plan of the Hellcat (same basic model as the example I am flying on the cover), which includes details of adaping it to look like a Zero. One tip, if you ever build thhis model, if you can? change the flat bottomed wing section to a symetrical one. The flat bottomed one can exhibit some unpleasant charcteristics at slow speed which take a bit of sorting out. I am told that the the Zero version built as per plan is less prone to this, which suggests a problem to do with wing tip tubulence in the Hellcat.

carrier pack

The Pack is availabe from, Andy Houseden, 8 Denmark Road, Kingston upon Thames, Surrey, KT1 2RU, UK. Tel:(+0044) (0)20 8541 0186

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