A return to model building and flying. Part 54

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Oct 2008

Lazy Days

In case people are wondering why I am not writing much, first let me say, I am fine,  just very busy with other things which are very time consuming. As you will have read, my other hobby is computers, building, administering them, and becoming deeply involved with Second Life is occupying enormous amounts of time; couple that with bad weather, and and just plain running about, means I have not been doing much at all on the aero modelling scene.

Also the interest in CL at my club seems to have taken nose dive recently for various reasons, and it's not much fun flying on your own (the prospect of assembling and disassembling a carrier deck on my own does not fill me with joy for a start), it also renders any form of competition is almost impossible, and as I am not much interested in RC. there is not much incentive. I also have a growing frustration with not being able to run small engines without silencers at my club, this makes a lot of things I would like to do very difficult if not impossible. Manufacturing mufflers for older small diesels is not possible for me with limited resources, and fitting them can kill the performance.

Strangely since my fathers death in January and the aftermath, this has been the most uneventful year for a decade for me. So I am enjoying doing absolutely nothing, and letting the world slide by for a change. I seem to have turned into a Female OAP, Slob, Geek, which I find highly amusing.

I have not gone away though, and also have to find time to build and appraise a prototype C/L kit which is under development. Not allowed to say much about that yet, so you will have something to read about in the future. And hopefully you lot out there will still send me stuff for publication. I have no intention of abandoning the website, it is just another aspect of my computer interests and can be pulled in with everything else.

Hanging About

One thought that did occur to me the other day whilst watching the antics of the RC fliers at the club. It may be possible to use a cheap 2.4GHz park flier outfit to work the throttle on a carrier model. It should work happily alongside the normal RC outfits, and do away with the need for an insulated second line. Food for thought?

In an unusual fit of good weather, I managed to do a little flying recently with the Hellcat, I decided to spend the day have a serious attempt at prop hanging it. I can do that with ease with the smaller Wildcat but I have never attempted it with the .40 powered Hellcat because it is such a pig to handle at anything like a high angle of attack, Dutch Rolling all over the place like whale tripping on some psychedelic drug, and feeling quite unpleasantly nasty on the other end of the lines. The SC.40 Mk1 which I always used, not for it's power but for it's reliability, surprised me by starting first flick after not being used for some time; and kept doing that all day.

Of course tying to do this in nearly flat calm conditions is not a good idea. A breeze is good for slowing a model down to make the transition to vertical. In flat calm, the model just trundles round at a fixed angle, sometimes just on the up-line with the other two flapping in the wind, and is difficult to shift beyond that. Well it is for the way I trim them anyway.

A point I have heard mentioned more than once to justify the use of RC servos and signalling down the lines, is that if the lines go slack on a three line system  the engines dies. Owwh Noooo it doesn't!  it will only do that if it the bellcrank assembly is set up incorrectly. It will remain the at the same speed with a Roberts system, one reason among a few, why I don't like them. With the simple system I use set up correctly, the throttle will open up as the lines go slack, and that has kept me out of trouble more than once. Set it up wrong and you can be in a world of pain if you don't recognise the symptoms.

I did manage to hover it for short periods, which is a major moral and confidence booster. When you can get the thing hanging motionless in the air even for a short time, it makes normal slow flight seem a lot easier. I also changed from 10x4 nylon Kavan to an APC 10x5 as the Kavan was causing a bit of vibration and not quite giving me quite enough airspeed. A fine pitch is essential for prop hanging, too much pitch and the hang is almost uncontrollable and so is the transition. Big powerful engines are also, not, a good idea for hovering; A) they are heavy, B) controlling the power is difficult. This size of prop had a quite surprising effect, in that the Dutch Roll seemed to actually be reduced (far from gone, but reduced), and it was possible to hold a high angle of a attack for quiet long periods. Another 5% Nitro, taking it up to 10% also gave me a just enough grunt to be able to lift vertically if the model started to slide downward on the tail in the vertical position.

I also noticed for the first time that Dutch Roll occurs around the the 30 degree basic carrier rule limit, beyond that it starts to dampen down. At over 60 degrees, the class 1 limit, it becomes even more settled. so it looks like the flat bottomed lifting wing section has to go into a super stalled state before it becomes stable. In other words, not lifting anything! Even more reason to not use one in the future.

All this was in near flat calm conditions, and I have no doubt that it will all go to hell in a wind, but this is the first time I have seen noticeable changes that have actually improved something with this model. So fingers crossed for the future.

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