A return to model building and flying. Part 33

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Nov 2006

A New Model Shop

Model shop

A few weeks ago an new model shop opened in Leicester. I can just imagine the collective sigh of relief from everyone contemplating having to travel long distances to buy stuff, or paying postal charges after the demise of the last model shop

Tony's Models and Hobbies
214 Saffron Lane
Leicester
LE2 7NF

Tel: 0116 244 222 3
Mob: 07725 585 777
Fax: 0116 244 222 3
email modelsandhobbies@hotmail.co.uk

Tony Haines, the proprietor, is prepared to order stuff he does not carry in stock, which makes a change; mind you, whether the wholesalers will have it in stock is another matter? He also used to fly CL models, which is a real plus for me as he actually knows what I am talking about. He even has a few basic CL bits and pieces in stock like handles, lines and line connectors. Even Diesel fuel, in 1/2 gallon cans, which also begs the question, if all liquids are suppose to be marked and sold in litres now, howcome all model engine fuel in quantities over one litre is still sold in gallons?

So if you live in Leicester or surrounding areas, use the shop and spread the word, we really do need a decent model shop here.


Leicester MAC
Carrier Deck

The Leicester Model Aero Club is now in possesion of a carrier deck, and a pile of plastic buckets have been purchased to mount it on. It needs a bit of attention and the acquisition of arrestor cords and drag weights, plus decisions about how and where to store it; but together with the new second circle, brings us one step closer to being able to organise some sort of carrier event. I am personally looking forward to trying it out at the first opportunity, and I hope it encourages others in the club to have a go at carrier. I'm sure people don't believe me, but it, IS, a lot of fun trying to fly a model as fast as possible and as slow as possible during the same flight.

Soon I will have, "Hook down, wheels down, flaps down," running through my head. If you don't know what that's all about, go to Zeno's Warbirds web site, and watch the video on 'Flight Deck Crew Landing & Respotting Aircraft Carrier,' it's been in the Matinee section for November, so if it's missing and and anyone wants to see it, I can temporarily put it on my website for a month. If this video does not get anyone in the mood for a bit of model carrier flying nothing will. Watch this space.


American Control Line Kits

Recently I have been acquiring some CL kits for future projects. The first was a Stirling Ringmaster. Now I had heard rumours about the bad die cutting in old Sterling kits, but quite how bad this was I didn't appreciate until I looked more closely at the parts. 'Die Crushing' is a very apt description, it reminded me of some of the old rubber powered KeilKraft flying scale series; only worse. Not only that, but the sheet for the leading edge looked like it had been driven over by a tracked vehicle. The, piece de resistance, is the 'half a plan'. The wing is there but no other detail except for pretty pictures and blocks of text. There is not even a mention of an initial centre of gravity position either, that is bordering on criminal in my book.


ringmaster
Box illustration looks pretty

rm fus A
Die cutting looks ok this side

rm fus B
Other side reveals the truth

rm LE
I'm supposed to sheet the leading edge with this?

rm plan
This plan is a triumph of artistic design over practicality and usefulness

I have nothing against good design, in fact we don't see enough of it. But this is an example of what happens when form precedes function.

I was going to have to modify it anyway because modern engines carry silencers, out of necessity in most instances, and are generally heavier than the engines used when this kit was conceived. This means a longer moment arm at the least, to try and compensate. Plus the fact that no 110cc clunk tank that I have seen will fit in the gap between the wing LE and the back of the engine, which means lengthening the nose or making a metal tank to fit. So all in all a lot of extra work.



The other two kits are by Brodak, won on an eBay auction. The usual story of going after one thing and putting a sill bid on another thinking someone is bound to outbid me, then winning both. Oops! because the shipping and customs duty can be high when things come from the USA. Long live the EU! Makes me want to stand up hand on heart and play Beethoven's "Ode to Joy" at high volume. Hands up now, how many of you knew that was the EU anthem EU flag ? You can't come here and go away without learning something.

As it turned out, the total cost was still way below what I would have had to pay for just the kits with no shipping from anywhere else, so I am not complaining. In fact the guy was selling a large number of CL kits and I could have bid on a lot more, the only thing that prevented me was my none too bright financial situation.

The kits in question were an F8F Bearcat carrier model, actually a reproduction of a J Roberts original design, this was my primary target, and a Buster (the one I thought I wouldn't win). Not quite sure how to categorise the Buster but it should stunt, and that's what I want it for.

What a difference from the old Sterling kit. Neat die cutting, reasonable wood selection, essential hardware, comprehensive instructions on building and flying, and a proper plan. I'm already lusting after some other Brodak kits: what the hell have I started....? I would really like the Corsair, but it looks like that may have been discontinued as it's not in either Brodak list of carrier kits.


Bearcat
This is a fine kit and more complex than it looks on the box

Buster

Buster parts
Compare this to the Sterling diecutting

Buster plan
And a real plan with comprehensive instructions


A Very Stupid Mistake With Nitro

This tale of errors still annoys my intensely. After a flying session I always top up the fuel bottles in my flight box so I am ready to go next time. I always carry glow fuel in 0.5 litre bottles, usually 2 of them in case of accidents, like knocking one over when it's open. These are the same containers that fuel is supplied in.

I still can't remember why I had a 0.5l bottle of pure nitro open on the bench that was half full, but I ended up with the half empty fuel bottle open on the bench as well. After bending over to pick up the 5l bottle of 5% fuel to top up, guess which one the fuel went into? My first incling was the nitro sitting at the bottom of the bottle not mixing. After the anger subsided over wasting 250ml of nitro. I resorted to a spread sheet I had made to work out what happens when you change ingredients in a known fuel mix; this is one of the reasons I will not buy fuel if I do not know the proportions of the mix. It takes an awful lot of 5% fuel added to the mix I had accidentally created to get it down to a 15% mix, which I can at least use, a higher percent nitro mix is just wasting money.

So now I have a large quantity of 15% mix and I am running out of 5%, at least the latter is cheaper to buy, or I can cut some of the 15% with some strait fuel to get 10 or 5%. All this trouble because I stupidly left a bottle open. Oh well, It happens to us all at some time. I am at least thankful that the years of mixing my own fuels left me with the knowledge of what to do to try and make the best of a stupid mistake.


Puzzling fuel feed problem

After this fuel debacle, I took the Hellcat out for an airing, not having flown it for a couple of months I was missing it. On a whim I decided to run it on 10% fuel instead of the normal 5%.

This is the point where everything went pear shaped. The SC .32, normally as reliable as clockwork, burst into life and screamed its head off; opening the main needle seemed to have little effect, and the best I could achieve was an intermittent drop in revs that sounded like a stutter.

Thinking it was something to do with bodged up fuel I had created, the tank was emptied and refilled with some original 5% mix. Didn't make a jot of difference.

I checked the plumbing for leaks, tried it with and without pressure, had the clunk tank out, blew fuel through system and the carb, but still no joy, to the extent that the needle was nearly hanging out of its housing without making the engine run richer.

I am using a remote needle for those that have not followed my previous exploits. so more in a desperate clutching at straws I tweaked each joint a little tighter, although none showed any signs of being loose. And finally took the feed pipe off the needle assembly and blew it through towards the carb.

Finally, that seemed to do the trick, and the engine could be controlled again. In retrospect I came to the conclusion that there must have been some sort of obstruction in the carb itself that was moving back when the fuel siphoned back to the tank, giving a false impression that the jet was clear, but moved forward when the engine sucked partially blocking the jet and causing the engine to run lean.

The SC 32 (I suppose it's a Mk III although the box just says 32A) has always impressed me performance wise, but with an extra 5% nitro and approaching being fully run in (with each passing day I am even more convinced the ABC engines take a lot longer to run in than users and manufacturers think they do), it is even more impressive, resembling a snarling beast that will pull a very draggy model round at an impressive rate of knots. If you are tempted to try one, look at the latest generation of ASP .32 or .36 series 3 with the squarish cylinder head, a Magnum XL series should also be the same. My own model of SC 32 I have never seen on sale, it came from eBay, only the earlier versions with the round cylinder head seem to be in retail outlets.




MVVS 12Another engine I got for a silly pocket money price on eBay was a brand new MVVS .12 complete with mini pipe. This seems to be a strange size, as it's not quite fish or fowl. It had sat on a shelf for months waiting for a suitable project, so I decided it was about time I ran it in; that's when I found out why I probably got it cheap. There was a distinct rough feel to the crankshaft bearings, I know enough about engines by now to know how they should feel. I have a nagging suspicion that this bearing problem also exists in my MVVS 2.5 diesel and may be the reason it has never lived up to it's potential, so that's another thing on the to-do list.

Having learned only fairly recently how to fit bearings properly. I removed the bearings and gave them a good clean. The rear one was the culprit, so it was off the the local bearing stockist for a replacement. This cost the princely sum of around £4.00. After fitting and resassembly, the engine felt quite different and a lot more like it should.

The proof of the pudding, as they say, is in the eating. So it was duly bolted in a test stand. When a new engine starts second flick it always feels like a good omen. The little beast revved away quit happily at 13,000 rpm, at a slightly rich setting, showing no signs of stress, but following my own guidelines it will be run for longer at lower revs for some time yet. The engine is quoted at a practical upper limit of 19,000 rpm; we shall see?




TT peripheral jetWhilst on the subject of engines, I run a Thundertiger .15 in a Hallam Swift to try and get some stunt practice in occasionally. It has always been a relatively powerful engine maybe because my home made venturi is of a slightly larger bore than normal. The needle valve sat in the centre of the choke in a conventional manner. I bought a load of mixed size and type venturies some time ago, thinking they would be easier to modify than turn up new ones, most where of the Rossi/SuperTigre peripheral jet type. I decided to try this arrangement in the TT .15, as the cotter pin hole would accept a spraybar; just to see if it made any difference. The short answer is yes it does. In fact such a difference that if the hot starting was OK, I would put it in a team race model. This type of induction obviously needs looking into more closely.

Having suffered from short runs with modified commercial metal tank, I made a bigger one. The first flights where not so good with the engine leaning out in flight producing a couple of deadstick inverted landings after a few manoeuvres. It was also pointed out to me that the tank had developed a leak. This is no great problem as every first flight after a modification is always a shakedown flight to show up anything wrong. What surprised me was the number of leaks the tank had sprung. I'm usually pretty good at making tanks, and pressure test them before mounting in an airframe. I must have been having an off day when I made this one.

The resoldered tank worked, giving an a fairly even run leaning out slightly after half a tank, but this is not a uniflow vent arrangement, so hardly surprising. However when it leans out it develops an unsettling turn of speed as the revs climb the power curve, and runs on, and on, and on, to the point where I begin to wonder if dusk will fall before it stops. So I may have gone a little too big on the tank size, another couple of flights should nail down the correct size.


Yellow Thing Metamorphosis.

If any one read my previous scribblings they would know I spent some time developing a flying wing team race model to cope with our uneven grass circle and be simple to build. This was the end result.

yellow thing

It performed reasonably well for most of the season, but showed it's Achilles Heel on a windy blustery day. The model has a larger than normal wing area to make the landings a little more gentle; breaking a model each time is not conducive to success. The only problem with this is the extra drag slows down the initial acceleration to the point that the model is barely controlable on takeoff, to the point where on this day it just corkscrewed itself into the ground.

A heavier wing loading and smaller wing area, a full span elevator, and moving the UC to the other side of the fuselage to help maintain line tension while the model ploughs through the grass trying to achieve flying speed, were the next things to try. Several saw cuts later, the model looks like this and actually seems to have worked, being a lot more controlable in the air but still retaining some of it's better landing qualities. Try doing this with an RTF model.....?

yellow thing 2

The touch up paint job will come later. This was the first model I experimented with, using water based polyurethane varnish to stick light weight tissue to the structure instead of dope. I can now say that this is produces an extremely tough finish, it was quite difficult to file and plane off.


Lessons Learned

I have known for some time that I need a replacement for my .40m class club racer. It has always been overweight, but ironically this has enabled it to fly in some really bad wind. The MDS .38 has finally settled into a very reliable motor that doesn't let me down when it comes to hot restarts. This is a combination I don't want to readily give up.

The next model had to be a jack of all trades. I need an airframe that will accept a wide range of engines with little or no modification, and be lighter than the model it will replace.

After measuring up a selection of my engines I found almost every one in the .21 to .38 range had almost identical bearer and hole spacing. This is a real bonus, as I want to also use it to run in some engines, which I would like to do most of in the air.

The weight came out all in, with a Super Tigre .34 and very brick like silencer, at 1000gm. The model/engine combination it is replacing, weighs in at 1300gm. So it looks like I have managed reduced the weight by the weight of an average .30 size engine and silencer. A two wheeled undercarriage was fitted so I can at least fly it with a remote release if no one is around. I also reverted to a full span elevator after some problems with half span ones on the smaller models, half span works, but only if done propery on a fast model. As all my models sometimes verge on the down right slow, I thought it better to err on the side of caution, even if it means a little more building time.

all in one

All that remains now is to see how it flies. Watch this space.



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