A return to model building and flying. Part 42
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After the obscenely dire weather of the last month. Suddenly we have a local heat wave for a few days. Determined to make up for lost time and, 'Make hay whilst the sun shines,' as the saying goes, literally what the local farmers where doing. I spent as much time at the flying field as my ME and the tiredness would permit. Seven days in succession was quite a feat for me, but it was beginning to take it's toll some days.
What did I achieve in seven days? Well a little and a lot really. The crowning achievement was finally setting up the Carrier Deck, making some necessary repairs, and trying it out. I must admit after half a day of lugging the whole thing across the field, up a hill, and heaving it all into place single handedly, left me unsure if I wanted to attempt to fly anything at all; but in the end I couldn't resist it.
As far as the Carrier deck was concerned, the main unknown was my idea of using water filled milk bottles as drag weights. In the event they performed much better than I expected. easily pulling the small light Wildcat to a halt, and having no problems with the heavier .40 powered Hellcat. The deceleration is very smooth, two lines will hold the Hellcat at full throttle. One would probably do it as well, but I was too tired to experiment further.
The above picture is the first model to perform an arrested landing on the deck since we acquired it. And as I performed the feat, I claim the right to Christen the deck 'Scuttle Bucket.'
It can be seen that although two lines are caught, only one has been moved, the bigger model provided a similar result. It will need further tests but it looks like the weights and drag are about right.
And I still get the big grin feeling, wanting to punch the air and jump up and down when I do make a successful landing, that I got the first time I managed it a couple of years ago in Holland.
If anyone reading this would like to fly/practice/have a go at controlline carrier, get in touch, I can always always sign you into my club as guest for the occasional visit. Only requirements are a silenced engine and BMFA insurance, I should even be able to provide a model if necessary by the time you read this.
What else did I achieve apart from staring at a wonderful countryside vista whilst drinking cups of tea? Not much. I was still struggling to sort a model out that is suitable for the Club Gala Day stunt competition. The Brodak Buster still continues to frustrate me. I have never had a model as contrary as this one. Hideously twitchy and sensitive, with strange feeling control responces. I have managed to tame some of the wild behaviour by adding copious amounts of lead to the nose until the CG is in a forward position that defies logic, and making a double length control horn, but still it refuses to groove in level flight.
One thing I think is not helping is the size of the bellcrank, it seems a bit on the small size for a stunt model. A bigger one would certainly help gear down the elevator movement a lot. Another is the thin pushrod which I think is bending in flight and causing some strange things to happen. That I could fix, but no way was anything going to be ready in time. Looks like I am about to make a fool of myself again.
And yes, on the day, forgetting what manoeuvre comes next in the schedule after a complete mental shut down, certainly had me feeling stupid; and caused certain amount of hilarity amongst the onlookers. The only saving grace was employing a caller on the last flight and actually improving my score. I am determined to sort this blasted Buster out one way or another. Knowing I can fly better than the model will let me is an big incentive. A hastily made pushrod support didn't really make a lot of difference on the day either.
The club gala day was a great success. The forecast rain in the afternoon consisted of one heavy downpour around the middle of the day, with everyone making a beeline for the club hut, the morning and afternoon were sunny and warm with not enough wind to frighten anyone. A bouncy castle was under a continuous pummelling from the small children present and the barbecue was constantly surrounded by adults looking like they where trying to put on weight for winter. The CL event was the usual jovial affair, a catapult FF glider comp was enjoyed, and the subject of even more laughter, lots of general RC flying, and the auction of a collection of vintage engines (entertaining in it's own right), meant there was not much time to be idle. And of course I had to have a last play on the carrier deck before putting it to bed the next day. Severe weather warnings have been issued, and I don't want it blowing away. This is one hell of a contrary country to live in weatherwise. There are some general pictures of the event on the club Website here
The continuing saga of my father's MDS.25 grinds on and on. During a telephone conversation it was clear that he was fed up with it. The last attempt to fly it, resulting in it starting and running perfectly well on the ground, but cutting out after takeoff no matter what he did, a performance that had been repeated countless times: followed by offering it to me to get rid of it.
I can always use engines, so a couple of days later I collected the somewhat gungy lump of metal; the state that most of my fathers engines end up in. It also seemed to be covered in some sort of coarse dark grey grit, possibly off the runway he flies on; which didn't bode well. The next day it was dismantled because of a suspicious rough feeling of the bearings at a particular point. After a thorough degrease and cleaning in an ultrasonic cleaner. When reassembled it felt as if the piston liner seal was for all practical purposes, non existant.
I had also been given the parts remaining after the demolition job he had performed on his first MDS.25, which included another piston liner/assembly. However no combination of either, or mixing and matching, would give me piston/liner fit that would seem to give any decent compression. It was finally reassembled with a combination where the piston did not jam half way up the bore or feel like it fall out of the liner if inverted.
After inserting a little Castor oil and a small squirt of strait fuel to see if it would make any difference; it did, with the engine making the right kind of plopping noises when flicked over
Bear in mind that this is the same engine I had off my father in February this year to try and sort out why it would not throttle properly. I managed to get it to perform faultlessly on a test stand then, so I have no idea what he is doing to it when it leaves my hands, apart from sitting on the front of a high wing RC model with a fuel tank position too low for comfort. The only thing I can do now is stick it in one of my carrier models and put it through it's paces; providing the compression stays put and doesn't leak away with the oil. I really would like to settle this once and for all.
For what it's worth, it's possible identify a worn piston liner with a bit of practice. If you take a worn engine and turn the engine over slowly (without the glow clip attached, obviously), this does not apply to ringed engines, they have their own rules. If the seal is bad there will be visible bubbles in the exhaust port, and/or with gentle pressure on a prob blade, the piston will make its way to top dead centre, then take almost the same pressure to get it down again.
Another good telltale is on an engine with no prop fitted. If it is possible to turn the engine over gripping the prop driver in your hand, without a 'lot' of effort, the compression is not good. Again this does not apply to ringed engines. Using this test you will probably see all the other telltale signs as well.
A good seal will feel totally different, with the up stroke taking quite some effort, and the down stroke pushing the prop round without any effort from yourself, I have had a few raps over the knuckles from engines if the comp is very good.
This is a good test when handling a second hand engine with the intention of buying. Make sure you squirt a little (don't flood it) fuel into the cylinder through any available orifice, enough to wet the cylinder walls, before you try the above. Engines that have been stored for a long time, or have copious amounts of after-run oil applied, will disguise a worn bore and feel like there is good compression; that is, until you run it for the first time......! Yes, I have been caught out by this one as well.
Whilst trying to give my carrier models an airing a couple of days before the Nat's, I ran into the humidity problem again with the SC.40. I have come tor recognise the missfire sound when running and not picking up after the throttle has been closed for any length of time. For two hours I changed plugs, props, fiddled with the settings, and dismantled the tank to check for anything amiss. Nothing worked. The only thing I could not try was a different fuel, as I had only brought my usually reliable 5% nitro mix. I runs fine on the ground and throttles OK but once in the air becomes very unpredictable, and as time went on began cutting out after 1/2 a lap from take off. This was making me very disconsolate, as I have no clues or time left to how to get round the problem before the Nat's.
To prove a point I flew the MDS.18 powered Wildcat. And sure enough the humidity had altered this engine as well. The difference was that opening up the main needle 1/2 a turn had it running correctly. So at least I have one model that I can use.
Resorting to plan B, I have replaced the .40 engine with an older version of the SC, because I have no time to sort the other out, and hoping that it is the original engine at fault.
How this all worked out at the Nat's you can read here
I wonder if an electric motor could affect this kind on interest or involvement? It doesn't seem to hold any appeal for me personally. Flicking a switch and having the thing start, with the only worry being, will my lipos explode if I charge them incorrectly or crash? doesn't seem to really cut the mustard for me, somehow it's as if something is missing. Even watching a 3kW RC pattern ship zooming around the sky making as much prop noise as an ic engine, can't hold my attention for long.
I do have this dream about having a gasturbine powered carrier model, but when someone suggested an electric impeller power unit, although I know it is probably practical, somehow it just left me cold. There must be something in my primitive psyche that is attracted to heat, flames, explosions and thrashing bits of metal; in the same way that I find a bonfire burning down in the dark or watching a steam beam engine operate, quite hypnotic and satisfying.
There are certainly parts of my life I like to have electric power in, everything from working this computer, electric lights, my washing machine, wrist watches or electric trains, but powering model aircraft does not seem to be one of them. This does not mean I don't get extremely frustrated with ic engines when they won't perform as they should, but that is the nature of the beast. And I certainly wouldn't deny anyone else the enjoyment of messing with something they enjoy: good luck to them. Who knows, one day I may be forced to use electric power in models by circumstance. And there is one other thing, the more people that take up electric power, the more ic engines there are floating around out there for me to pick up cheaply.