A return to model building and flying. Part 34

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Dec 2006

Dumas Crusader Kit

Dunas Crusader

This kit was one of those items that appeared in eBay, that I just had to have. No only was it a pretty rare kit, but of a model I have been interested in for quite some time because of it's semi scale jet appearance, and it's a carrier model as well.

Ming the MercilessI knew that the kit was missing the 12mm fuselage, and the two 6mm sheet stabilators (if you don't know what that is, all will be revealed later). But we laugh in the face of such adversity, Hah! I who have scaled up plans from postage stamp size images, and pasted lots of A4 sheets together to get a plan, find this task a piddling little one. Tomorrow we conquer the universe.

The kit plan is printed half scale, so it was off to the print shop to get it enlarged and printed out full size. For those interested that cost £4.00, and was well worth it.

Dumas made a good job of this kit, if the number on the plan is a date, it was produced in 1985. The die cutting is not spectacular, so usual standard there then. The rest of the timber is strait and of reasonable grades for the job. However the real interest for me is the design, which is in some ways very original, but not to the real full size naval F-8 Crusader, or construction methods used in other CL disciplines.

The first thing that hit me studying the plan was the use of a Detroit wing, This consists of a central 'I' spar and cap ribs which are between the LE and TE and over the spar, this produces a very strong light hollow wing structure, which was quit common in the F2B stunt circles in the 1980's, but as far as I can tell this type of structure is not so common in carrier models. Not only is the wing structure different to normal, it has anhedral like the real aircraft.

Crusader kit

And this is the point I came unstuck for the first time. Wishing to savour building this model at some future date, I replaced the missing parts. After the straitforward job of cutting out the stabilators (OK I give in: stabilator is a combination of stabiliser and elevator. On nearly all supersonic jets there is no fixed tailplane surface, and the whole tailplane moves; hence stabilator. So now you know.), I produced a fuselage; then habit took over. I proceeded to cut out the hole for the wing to slot through. After lazily perusing the plan, I noticed some odd plywood bits that didn't quite make sense, then the fact that the plywood fuselage doublers only had holes for the main I spar and the bellcrank hove into view. Oops! The penny finally dropped.

The wing is virtually built in-situ, the fuselage resting vertically on the building board with the main spar LE and TE passing through it. The strange bits of plywood I noticed, were actually wing tip jigs which hold the whole assembly in alignment while the cap ribs are glued in place. Feeling very foolish, I managed to find the bits I had cut out and glue them back into place. I know: I should have read the instructions; but how many of us do?

The other unusual feature I mentioned previously, the all moving tailplane, is unusual enough, but it also has dihedral. This is going to be one strange aircraft to fly

F8 Crusader

The other thing is the tricycle undercarriage, not exactly common on CL models, although I have seen them about. All in all, a very unusual and interesting carrier model, and one I am having to restrain myself from building. I have other models that I need more urgently at present. Unless the cold, wet, windy, miserable weather we are experiencing at present, drags on for the whole winter; then I might not be able to keep my fingers out of the box.


A Few More Engine Stories

Apart from giving me something to write about, I hope that these problems and solutions I am constantly wittering on about, may help some poor soul struggling with similar ones.

This time it was a mass engine running-in session, well two actually. Selecting an engine to put in a new model, then finding I have to piddle about running it in before I can fly it, is a pain in the rear. Running in engines is something I tend to do when the weather is too abysmal to do anything else. My living space does not allow me to do such things at home, and its an excuse to go to the flying field, instead of moping around at home trying to find excuses not to do essential housework and cursing the weather.

MDS25 Leo28The engines concerned were a Leo .28 ep, and an MDS .25. I have not just purchaed these angines, Just in case you get the wrong idea. The MDS.25 has been sitting on a shelf for over a year and the others swapped for other engines at various times. For the reasons stated in the previous paragraph I decided it's about time I got to grips with them.

After a lot of coaxing into life, both ran a tank of fuel through. The reluctance to start was a little puzzling, as the engines where poping and spitting with every flick, they obviuosly were ready to go but it was as it each charge into the cylinder was putting out the fire.

All the usual things were checked like plugs glowing and different batteries, but nothing was out of place. All I could put down to was the weather. The Leo was the only one to start and run without any trouble on the second tank full. The MDS was fitted with a Mk1 carb which has a 7mm choke, quite large for an engine of this size (the Leo has a 6mm choke). The MDS carbs are physically bigger which has the visual effect of making the choke look like a gaping maw. It's reluctance to start may be something to do with lack of suction. The engines were in a test stand that does not readily allow the throttle to closed so I tend to run things flat out controlled by the main needle, and worry about the tuning the carb once in a model. Both engines ran fine once started. so there is nothing wrong with them mechanically.

A peculiartiy of the MDS was the fact that to get it to start the needle had to screwed almost out of it's housing and could not be closed much more when it was running, but as it turned out to be a real screamer on an 8x4 prop I don't really mind, the problem could be looked at in the warm and dry.

Back home the carb was stripped and checked for obstuctions or blockages, I'm not too worried about air leaks as they will be constant, once the mixture is set it should stay the same. The end result was that the only thing I could find that was remotely not quite right, was blowing through a tube attached to the carb fuel inlet seemed to take slightly more pressure than doing the same thing with an MDS MkII carb. the only thing this may mean, is that the needle may be a little too far out of it's knurled housing, so even when screwed right out, it is still restricting the needle orifice. This was not an unusual problem years ago, and is easily remedied if that proves to be the problem, but I was still not convinced.

TT.15GPThe next week the weather was even colder and windier, so more running time was on the cards. This time with the addition of a Thundertiger.15 GP I had forgotten about, I hope it turns out to be as good as the one I am flying at present. This is when the fun started, or lack of it may be a truer statement. the Leo burst into life and sounded like it really wanted to go. The MDS just refused to start, all I got was a lot of poping and eventually a flooded engine. OK lets try the TT.15, and give my finger a rest; would it start, would it B*****y! exactly the same symptoms As the MDS.

I had not charged my starter batteries so I was immediately suspicious of those. A borrowed battery, with meter, made no difference. Now this is odd, these are brand new engines that feel perfectly sound, the only thing that was common to both was the use of the last two unbranded glowplugs that I had bought as a cheap job lot, eight of which I had used in other engines with no problems at all including the Leo. They glowed OK, and seemed to ignite the charge. The MDS the previous week had a marked drop in revs when the glow clip was removed, suggesting a plug that is too cold for the engine; but this week it would not start at all. I had no spare plugs and swapping the Leo plug into the MDS did not provide a cure, it still would not start. By this time the cold and damp had got the better of me, so I packed up for the day feeling very frustrated.

MDS test standAll I could do was purchase a couple of glow plugs, glow plugs are not exactly cheap these days, of known characteristics and hope that this was answer. On the Monday morning my downstairs neighbour was out, so I did something I have been very reluctant to do. I clamped the test stand to my bench and jury rigged a piece of plastic pipe from the exhaust and out of the window. I had to know if it was the weather causing the problem. The MDS (with original plug) burst into life after one choke and a flick, then promply started to shred every piece of paper and plastic bag I had left lying on the bench, turning the room into veritable hail storm of detritus. Deciding that I wanted to enter old age with body parts intact, I retreated to the door until the storm had abated enough to get near to the engine and stop it. OK panic over point made. The temperature and humidity are obviously affecting the starting, on the MDS at least. The plug is still too cold as the engine stopped when I removed the glowstart, but at least it started.

Next up the TT.15. After much flicking, dead as a doornail, put in a new warm plug, a 'Fire Power F7' to be precise, which should be slightly hotter than an Enya 3. or an OS 8, and, if a little reluctantly at first, it started and ran. I also have an F7 to try in the MDS, to see what effect it has on the drop in revs when the power source is removed from the plug. However, wanting to keep my workspace intact and not risk life and limb unnecessarily, weighed heavily on my decision to wait untill I can try it outside next time.

I can't definitively say that I have found the answer to the starting problems until I can get the engines into a cold wet field again. But the experience so far, seems to suggest that glow engines are a lot more sensitive to plug temperature and external temperature/humidity than I thought they where. This may have implications for all sorts of things.


A Strange Discovery

Some time ago I wrote about fitting an MDS.28 into my Hellcat to try and cut down the weight. The engine started and ran like any other MDS I have used, reliably and consistently, and throttling well with a MkI carb. The Only reason I removed it from the model was because I decided, after quite a few flights, that it didn't quite have the power I needed.

Recently I was messing around with another MDS.28 that I have for spares, the crankcase is in better condition than the one I have been running and I was contemplating swapping the internals to make a good engine (cosmetically), when I noticed something odd about the exhaust port in the engine I had been flying. There was a visible external chamfer on the right edge of the liner exhaust port and an internal chamfer on the left hand side. Now as far as I can tell this serves absolutely no purpose at all, but it would do on a transfer port, and my limited experience of Russian engineering tells me that they never do anything without a reason. The exhaust port also lined up with the bottom two thirds of the crankcase outlet, something I have seen on other engines but not MDS's. Looking through the exhaust, the rear transfer port did not seem to line up with the transfer port cast into the crankcase. Something was decidedly not right.

A gorilla must have tightened up the cap head screws in the head and back plate, it took a lot of heat to be able to move them. I am sure they don't leave the factory like this, and it only served to raise my suspicions.

When I could finally raise the liner and get a good view of all the ports, my suspicions where confirmed. Someone had rotated the liner through 90°. The inlet and exhaust port where facing the side transfer ports and the transfer ports where facing the back transfer port and the exhaust port. Now how this would affect the port timing is beyond me. There would be an odd sequence of one side port opening fist, then the rear tansfer port which would immediately shoot the fuel mix out of the exhaust port, then the other side transfer would open. In fact I wonder how it ran at all, let alone drag quite heavy large model round the sky.

I have no way of knowing how much wear has been produced by running in this condition, then putting things back to how they should be. But I can only take my hat off to MDS for producing an engine that will stand up to this sort of abuse, and still perform reasonably well. If MDS has actually stopped producing model engines, as rumour would have it, it will be a sad day.

And to the idiot that turned around the liner; may all your engines seize up, your goats stop giving milk, and your camel's humps dryup.


The Story Continues

The next week was a cold and damp one, so the engines where tried again. first up the MDS.28 with the corrected cylinder liner was tried. It started OK but it took arond 15 minutes running before it would hold high revs. Guess the high spots are worn off now. Whether it will have markedly more power now the ports are all facing their correct orifices, I won't know until I get it into a model and thrash it.

The MDS.25 with the hot plug fitted, started and ran with no drop in revs when the glow start was removed, but with only one problem. As I mentioned previously, this engine would only run with the needle almost hanging out of the carb, and it was still exhibiting the same behaviour. Taking a step backwards for a moment, I could not help thinking again that this was something too do with the very large choke on this engine.

Trying to prove a point, the pressure feed was connected to the silencer. I had not used pressure on any of the engines until now, the idea being to try and force the fuel through at a higher rate. The effect was dramatic, the needle now responded properly and had to be screwed in almost three full turns and the engine mixture could be controlled properly. There was a similar effect with the MDS.28

An incidental effect that is swell worth noting, was when I connected the pressure feed to the engine whilst it was running, and forgetting to blank off the overflow vent in the tank, apart from fuel blowing out of the tank vent the engine behaved as if it was under full pressure. Why mention this? because it proves that a small hole in either of the vent pipes would not make much difference to the running an engine. All you would get is a messy oily model.

A large choke means two things. The engine will deliver a lot more power than normal because it can suck in a large amount of fuel and air, but more flexibility and tolerance to settings could be achieved with a smaller choke, for instance, if it was used in a CL stunt model this would be a desirable thing.

The TT.15 also started and ran ok with the hotter plug. By the end ot the day it had over thirty minutes of running, and was only just becoming able to hold high revs evenly. The slight, just perceptible changes in revs had begun to dissapear and it was holding an even note.

The Leo.28, always a starter before, now decided to be awkward, poping, and if flooded, oscillating the prop back and forth. Thinking this was simlar to my other problems I fitted an Enya No.3 I had found in my field box. There was an immediate difference, starting and running normally.

So that just about wraps things up. Plugs do make a difference, and MDS engines need pressure feeding. It was a long journey but I got there in the end. I Now have full compliment of engines that I can drop into models and just fly. Trying to sort out the problems I had one at a time in a new model at the field, whilst itching to fly, would have become very frustrating.


No Apology Needed

In amongst the emails I receive for time to time I get, none too serious, apologies from the writers for flying RC models. Presumably this is because I seem too have a perceived downer on RC a lot of the time. So I am going to try and set the record strait.

Firstly, I have absolutely nothing against RC or the people that operate them, after all I flew them for enough years myself, albeit a fair few ago, and have done since. The recent ones have not been my own models or equipment. So as the title says, there really is no need to apologise at all

Secondly, although I have nothing against RC, my main interest is control line, so obviously my juices start to flow when the subject matter of any email is about some aspect of CL. RC I see and hear about every weekend at my club as there are a lot of RC fliers, but only a handfull of CL fliers and more than half of them fly RC as well. It is difficult to explain and probably even more difficult to comprehend by anyone that has grown up with RC and never flown anything else, why anyone should want to rotate round in a circle all day; and the same lack of comrehension probably applies to why anyone would readily launch a free flight model into the welkin and start walking after it, but I will leave that to a FF enthusiast to explain.The following will probably be like preaching to the converted, and it certainly won't convert hordes of RC fliers anymore than it would model boat sailers, but if I manages to inspire just one person to have a go or take an interest, it will have been worth writing. So here goes anyway.

If you have read any of pages available from the top thumbnail navigation bar you may have some idea of what attraction CL has for me. Circumstances and an expensive accident was the first trigger that made me reappraise what I was actually getting out of aeromodelling in general. From then on CL remained just part of model flying and building as I am interested in freeflight as well. Things changed again when I decided to compete in competitions, F2B Precision Aerobatics to be precise. Suddenly the the sport flying was a hindrance because of all the bad habits that get learned. I also had to learn discipline and preparation. This took my general attitude to CL flying and building to a new level and also had an effected on my attitude to all forms of flying, and has done ever since. This has never left me. I suspect it is one of the reasons why I still love flying round in a proverbial circle.




I am going to digress for a moment. You will notice I refered to competition and sport in the previous paragraph. The original meaning of 'sport' has changed, and this original quote from Websters I love, because it most sums up what I get from my hobby:

[1913 Webster]
Her sports were such as carried riches of knowledge upon the stream of delight.     --Sir P.Sidney.

A more accessibel meaning to the average punter is probably this one

Sport \Sport\ (sp[=o]rt), n. [Abbreviated from disport.] 1. That which diverts, and makes mirth; pastime; amusement.  [1913 Webster]

Now the last definition fits with the old definition of a 'sports model'. and is diametrically oposed to a competition model..

Now why am I blathering on about this? Because I take issue with the BritishModelFlyingAssociation's definition of the whole hobby. It's not even politicaly correct to call it a hobby anymore, we have to call it a 'Sport'. Not only that, I am actually discouraged from calling myself an aeromodeller! I am apparently a 'Model Flyer'. This gives the impression that I am supposed to feel ashamed that I can design and build a model, as well as fly it? When I was young, the people that could design, build, trim and fly, say, an FAI FF power model, for example, were Gods to me. Even today if not quite so God like, I still hold such people in extremely high regard.

But sport's what you have been calling it? I hear you cry.

No I have not. The BMFA are using the modern interpretation of Sport, defined thus:

sport
n 1: an active diversion requiring physical exertion and competition [syn: athletics]

Why? Because it can bring in money in the form of grants and other funding options. Now in all honesty do YOU! fit the last definition? I certainly don't.....! and I would guess 95% of the membership of the BMFA don't either. I have no objection to those that can, and do, compete, they deserve all the support that it is possible to give; I would be competing myself it was possible; but this is not what the vast majority of modellers/flyers do, so why do I have to be constantly told I indulge in a 'Sport'?

It might be just semantics, but it jars every time I hear the phrase. To me, I still indulge in the hobby of aeromodelling, and sport with all it's pleasant possibilities, with not an 'active diversion requiring physical exertion' in sight (unless absolutely necessary). I have been known to break into a run occasionally, but I don't want to make it a habit.

Enough! back to the story.




To the uninitiated it must look deceptively simple, and how can anyone possibly get hours of entertainment with such primitive unsophisticated equipment? It's like asking why a child will spend hours playing with a carboard box, or spinning round till they get dizzy and fall over; there is unfortunately no simple answer. The only way to comprehend it is to do it. By that I mean to a sufficient level of skill to compete in a competition of any sort at a minimum of club level, not just learn to fly round and round; that will certainly get boring very quickly, as can just flying in the same way every time with an RC model. Unless you are like one of our club members, who's main interest is engines, what they are in, or how they fly, is of little consequence.

Nearly all CL models owe some of their pedigree to competition of one form or another. You just can't build even a trainer, without the desire to do some mild aerobatic stunts as soon as you get used to flying it, or try to make it go faster. Also flying with more than one person in a circle is something you have to experience to appreciate. If you have the require gene you will get hooked at some point and the hook will stay there.

When the realisation dawns that most of my models cost no more that £30.00 to build and finish, sometimes more but that involves kits and the most I have paid for one of those is £37.00 for the Dumas Crusader mentioned above, which I realy, really, wanted. I rarely pay more than £30 for an engine, infact only once did I pay out over the odds for an OS.25AX, only to find it had no more performance than my cheap old ASP.25. A lot of the time I pay a lot less for either, only use around half a litre of fuel in a flying session, and a handle and lines cost only a few pounds and will last for an incredibly long time if cared for and handled properly. This brings home the grin per pound factor. I can't help but get a nagging suspicion in the back of my mind when stateing how little controline can cost, that with some RC fliers I talk to, there is a thought running through their mind, 'very cheap plus lots of fun: does not compute, does not compute????? not complicated enough????. It's the Umm! responce and the thousand yard stare that gives it away. It is possible to spend money in the thousands range if you get deeply involved in competition, or just want to show how much money you have to throw around, but it certainly is not necessary. Most of my enjoyment and satisfaction comes from seeing how much performance I can get for the least expense.

It's fun without complication. You don't even need a large space to fly, only a handful of commonsense rules to remember, none of the seemingly thousands and one rules and regulations that apply to RC flying, that seem to spring up like weeds every other week, no worries about radio interference/failure, being shot down, or flyaways, although the last two are possible if you fly combat or let go of the handle. But that's what safety straps are for; another piece of high tech CL gadgetry, that consists of a cord attaching the wrist to the handle

The main thrust of my concern about RC, and remember I have flown RC, which is more than can be said for the majority of RC fliers being proficient with a handle in their sweaty palm, is the way the hobby has developed; mainly into a buy everything off the shelf global industry, that has become so pervasive that other forms of model flying drop off the horizon and suppliers of kits and parts for the other less well known parts of the hobby become few and far between, thus compounding an already poor situation. And herein lies a paradox, RC hardware has become so prolific that the price of equipment like engines has fallen through the floor. This is great because engines can easily be adapted for CL use, but not so great for the thousand and one little things that make assembling and flying a CL model a little more pleasant, like for instance, metal fuel tanks and lines, and even kits. So we all have to import stuff from the USA, a basement workshop in Moscow, or a small enterprise in Lithuania or somewhere else. It must be said that without these people, CL would be a lot poored. And with this cuckoo like behaviour of pushing all the other chicks out of the nest, RC takes such a centre stage dominant position that no one can even see that other possibilities exist.

The main drive is obviously money, what RC manufacturer or supplier is interested in supplying people that only have to spend a relatively modest amount by modern standards to even fly at a reasonably high level of competition, when they can sell the next shrink wrapped thingummy to a lusting clientele that always seem to have very deep pockets and are prepared to empty them at regular intervals. Just rough guessing how much money is spent at the trade area of the nationals is enough to make me feel like I'm living in another world.

As I have also said before, this situation also dumbs down peoples ability or willingness to build models. This is a great shame on many levels, I certainly acknowledge the role that building models played in my overall knowledge of the use of tools, and how to work different materials, even at a basic simple level. That's not to say there is not a place for Almost-Ready-To-Fly models. Ready-To-Fly is another matter, we are getting into the semantics of, what constitutes a toy? (A wild fancy; an odd conceit; idle sport; folly; trifling opinion.[1913 Webster]); but to each his own.

The other less obvious thing is how I feel when flying an RC model or a CL model. I have always had a gold fish in a bowl feeling when flying an RC model. as if I not quite connected to it. But I have never had this feeling with a free flight model for some reason? Strangely I only started to notice this when proportional radio equipment came along, maybe wrestling with bang bang rubber driven escapements, in what where basically free flight models with ludicrously high wing loadings, underpowered engines and unreliable radio gear, gave an extra piquancy to the proceedings. This feeling of detachment is very similar to playing a video game, the only difference is, accidents when flying RC models tend to be physical and involve money. Video games, apart from the initial purchase, don't. I can quite see the attraction of sitting in a nice dry warm house and playing a favourite first person shooter, or a deeply engrossing adventure game, instead of flying an RC model. Maybe young people are not so dumb after all.

learningFlying a CL model is nothing like that, The first flight is usually blind panic and disorientation because everthing seems to happen so fast. Remember there are no buddy boxes for CL, and you can't climb to a safe altitude to let you brain get back into gear (although there are ways of getting round this), things will get even hairier if you try. Once the dizziness starts to wear off, providing the person in question has not given up already, the senses become more tuned to what is going on. Because the pilot is physically attached to the model everything can be felt through the control handle, if the engine is rough you will know about it in no uncertain terms, fly very fast and your arms will start to ache,fast try to make a stunter turn as tight as possible you will feel the forces involved. I always knew when I had put in a reasonable flight in F2B because it quite literally, felt right. You are also never far away from the model and can even see the most obscure things happening, have you ever actually seen a wing stall on a small model at high speed in level flight, I would guess not? Or seen how much elevator deflection it takes to keep a zero zero wing tailplane alignment in flight? If you are even mildly interested in aerodynamics, CL is close up and personal. Even disasters can be seen in sickening detail, I still have nightmares of watching a wing working loose on one of my F2B stunters in flight, and finally tearing itself off.

Again all that will mean nothing to anyone that has not flown a CL model for any length of time. For myself, I have enough CL projects, ideas, and things I would like to try to keep me going for the rest of my life, so I am hardly likely to get bored with it. Harking back to the Crusader kit I described above, I look forward to the day when gas turbines are small enough and cheap enough for me to afford. All the jet powered carrier aircraft it would be possible to build, would make things very exciting. I love things that make a noise and pour out smoke, flames and hot gasses would add a new level of fun.

I do hope people continue to fly CL, it has given me endless hours of pleasure, and a fair amount of frustation when things don't go the way I want them to, but what hobby doesn't? And as was pointed out to me, if it does die out, I shall probably be to old to care.



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