Conference vmszoo::rc

    I have a 3/4 finished Black Magic, temporarily shelved due to the
    arrival of my son, plus we only went and moved and the house needs doing up.
    
    I've converted the ship to Electric. The things I've done (from memory
    here) are:
    
    1) Redesigned the nose to take a removable mounting plate. This plate
    will house the electric motor, but will allow me to either try out
    alternative motors or put in a gas motor.
    
    2) Lightened the forward structure by cutting out the forward
    bulkheads. This will also allow me to put in the motor battery. I
    figured I could get away with alot here, partly because the
    superstructure is so strong and partly because you don't get the
    vibrations and brutal starting knocks you get from gas engines.
    
    3) The motor battery will be mounted behind the motor, but canted at an
    angle. The thoery being that in a crash, the battery will slide out the
    top of the cowl.
    
    4) I've dispensed with the kit u/c and made my own composit one. I've
    got to redesign it (as the first one broke in hand tests), but I think
    I'll have a nice strong, but bounce u/c. The u/c is separate from the
    fuselage, i.e. its not built in as the plans. I will dispense with the
    heavy wheels and substitute light weight polystyrene wheels - I need to
    save weight.
    
    5) I think I also redesigned the tail feathers, so that they are now
    fixed to the fuselage. The kit design looked too fussy to bother with,
    plus I needed to save as much weight as possible.
    
    I am still undecided as to whether I will sheet in the bottom rear
    fuselage or cover it solarfilm. I was a little unhappy with the design
    of the bottom rear fuselage.
    
    Those wing tips are a devil, aren't they? Especially as the instrutions
    were non-too-clear to someone just coming back into RC after a 15 year
    layoff. I was very unhappy about the ribs; did you not find that they
    were both uneven and didn't actually fit the plan?
    
    Finally, I bought the plane as a sort of trainer. My reasoning for
    buying this ship is that it should be dead stable in flight with nice
    gentle flying characteristics. The final selling point was what the
    shop keeper told me "This ship normally flys better when the pilot
    STOPS fiddling about with the controls. Afterall, it was designed as a
    Free Flight ship."
    
    Angus
                      

    
    I might buy/make a folding prop and do a way with the u/c all together.
    I would the definitely sheet in the under fuselage.
    
    The I also adapted the cowl to accept gearing for the electric motor.
    
    Angus

Thanks for the comments Angus. Yep, forgot to mention the ribs. They were pretty 
strange.... However after a bit of "cut and fit" I got them all to at least 
touch! One point I found was that the TE is shown as being notched to accept the 
ribs. Due to the aforementioned iregularities in the ribs I needed to cut these 
notches individually to match each rib. This means that some of the joints 
aren't notched at all, but butt joined. The wing appears to be fairly strong (I 
dropped it!) so this appears to have worked out OK.

Electrickery. Hmmm. I'm gonna bung an OS .25 up it !

Anyway, the weekend's progress. The wing is finished, and sanded. I've bought 
the Solartex for covering, but I think I'll do that as the last job. I've gone 
for their "antique" colour, with some dark green painted trim. Gawd it's going 
to be beautiful !

I've made a start on the tail surfaces. They're not all that strange I suppose. 
The basic structure is 1/8th sq. balsa, which has the LE sandwiched between 
1/16th sheet. 

Angus's comment about strength is very true. This one's definitely using brick 
outhouse technology. Lovely, it should allow me to land it good and hard !

So, progress. Not as much as hoped due to the unforeseen intervention of several 
pints of Tetley's finest ale, and Nick Faldo making hard work of winning the 
golf, but progress nonetheless. In the next rivetting instalment: finishing the 
tail, and starting the fuselage !

Cheers

Nigel

Well, a week off, and progress to report. The tail stuff's all finished, and 
very nice too. So, we have a wing, and we have some tail. There's something 
missing here....

The fuselage proves to be erm... interesting. There's a line in the instruction 
leaflet about planning your engine installation carefully to save hours of work 
later. They are not kidding ! I thought I'd planned my installation carefully, 
but I goofed, and put the engine too far back. Very neat installation, but the 
prop would have bitten the nose off! Ah well, much hacking and glueing later it 
all seems to work. I realised fairly early on that I'd have to modify the nose 
area a bit in order to make the OS .25 removable. I consider this to be highly 
desirable. Since it's mounted inverted, and the nose is a bit cramped I've had 
to make the front cowling removable. This is accomplished with some ply, some 
4BA bolts, a lot of smoke, and a few mirrors. This will inevitably be heavier 
than a straightforward glued joint, but worth it, I think!

The rest of the fuselage proceeded smoothly, the undercart wanted soldering, I 
read the "soldering" topic. I soldered. It works. Simple ! 

Then..... A missing bit ! There's a support for stringers at the rear of the 
"cabin" area, and it ain't in the box. Blast ! Darn ! Dash it ! So I'm off to 
the shop tonight to accost the man and demand a bit of balsa. I would have 
quietly made one, but of course this particular part isn't shown clearly enough 
in any of the drawings to get it's shape right.

So, that's it to date. In the next thrilling instalment I'll have screwed up a 
few more times, and the airframe will have got even heavier. Can you wait ?

Cheers

Nigel

OOPS!

Grovelling apologies to Flair. The "missing bit" wasn't. It in fact is made up 
from 1/8th square balsa. This is in fact a 50/50 mistake in my opinion. 50 to me 
for not reading the plans properly, and 50 to them for not making 'em clear 
enough.

Any road, the stringers are in place, and it's beginning to look like an 
aeroplane.

By the way, is anyone reading this drivel ?

Cheers

Nigel

    
    What's "drivel" anyway, don't have my dictionary at hand ?
    
    
    	Bernd

    The plans/instructions are most definitely not the clearest in the
    world. I spent HOURS poring over them trying to figure out how I was
    supposed to construct bits of the beast; and I still hit the odd sticky
    patch here and there.
    
    Re the bit about engine placement. I literally spent 2 hours eyeing up
    how the engine and the nose would fit together, before I even touched
    this bit. For those of you who don't know the Black Magic, its a real  
    vintage type kit where the nose is simply a block of balse about 1"
    (25mm) thick, 4" (100mm) high and 3" (75mm) wide. You cut and shave the 
    block to the nice deep rounded chin (with a hole in it) of the Black
    Magic. You have to gouge out the back of the nose to accommodate your
    engine.
    
    Things were a little simpler for me as I had elected to go electric;
    though heaven knows where I packed the thing when I moved. I fashion a
    plate from ply on to which I bolted the gearing housing I was using
    with the motor; the motor then bolts on to the gears' housing. I then
    drilled four holes in the cowl main stringer and epoxied four nuts on
    the underside of the holes/stringer. Then bolt the ply plate on to the
    main cowl stringer.
    
    This arrangement should allow me to try out a number of motors.
    
    Have you got around to making the cowl cover yet? This bit was fun. I
    end up a) soaking the 1/4" (6mm) square balsa stringers in water to
    soften them up, b) cutting out little Vs where the nose really curves,
    c) then taping the balsa bits to the stringers of the bottom of the
    nose (which I had already built), before glueing the formers and front
    block to the stringers.
    
    I have no intention of using what look like (on the plan) 1" x No 8
    screws to hold the cowl cover in place. A couple of light nylon bolts
    or even some velcro ought to do it.
    
    Angus

    Drivel : 1. to let saliva dribble from the mouth or mucus run from the
                nose. (heck, this is what my baby son classes as growing)
    
             2. to talk stupidly and childishly or carelessly
                (i.e. me at 3 a.m. cleaning up my son's 1.)
          
    
    Drivel : foolish or childish nonsense
    
    So. Question. What does management do 99% of the time...?
    
    Angus

Angus, is your machine called "SUBURB", or "SUBVERSIVE" ?

Well, (with apologies to Bernd), I'll drivel on. With regards to Angus's 
comments, I'll agree. The plans are a little vague in areas, but I think I'm 
getting there. 

The nose cowling has been started. I decided not to even try to bend the 1/4 
inch square balsa, since I found that I could angle them in slightly, keeping 
them straight, then sand them to match the fuselage curvature. This does mean 
that they are a bit thin in places, but I don't think there'll be much (any?) 
stress here anyway.

One thing that does occur to me here, and I'd appreciate some advice, is that 
the plans show the (4oz) fuel tank quite a way forward of the C of G. This means 
that as fuel burns (hopefully in the engine!) the C of G will move back, yes ? 
Now I've always believed that a rearward C of G would make control a bit lively. 
Do I want lively controls at the landing stage ? Have I misunderstood something 
here ?

Cheers

Nigel
 

You do the initial balance with an empty tank and that sets your landing 
control sensitivity. Fueling moves the CG forward making it less sensitive 
for takeoff.

Thanks Jim,

I should have worked that one out for myself ! 

Anyhow, there is progress to report. I've got the thing to the stage where I can 
put it all together and stand back with a silly grin to admire the results. It 
really is a rather pretty aeroplane. Tough job of the weekend: Putting the 
%�$!!** hinges in the rudder and elevator. I'd used a nice hard bit of balsa for 
the TE of both fin and tail, and the upshot was that cutting a slot for the 
nylon hinges was HARD. My wife tells me that she gave up counting at 32 
swearwords. Anyway, I got them in in the end, and all I need to do now is peg 
them.

Easy job of the weekend: Covering ! I'm using a product called "Solartex", and 
it's great! Much easier to use than the films I've used before, and very much 
easier than tissue and dope. This is really amazing, usually I hate covering but 
this stuff's got me quite enthusiastic.

Still to do: Finish covering, and fuelproof. Fit servos. Pin hinges. Fit 
glazing. Decorate. 

Then I'm going to have to grit my teeth, and let somebody at the club teach me 
to fly it !

Cheers

Nigel

Well now....

Bit of a break, boss man wanted me to go away for a few days. Don't these guys 
realise what work does to disrupt your hobbies ? Maybe that's why they pay 
me.... 

So the covering's finished, and I want to decorate a bit. Nothing flash, just a 
tasteful green stripe down the side, and a green cowling. Make up a test piece, 
and use the covering maker's paint. Yeuch !, the paint creeps under the masking 
tape, and look 'orrible. Congratulate self on trying it out on a test piece and 
not the model, and return to drawing board. The man in the model shop suggested  
applying a coat or two of clear finish first, so I did, remembering the test 
piece! Lucky really, because the results were exactly the same. 

I called the manufacturer, who said "Oh dear me no, the solvent in the paint 
will attack the clear finish, and you'll get creeping". Thanks guys.

So, where did I leave that drawing board? I know, I'll give up! That "antique" 
finish looks OK anyway, right? Fortunately I'd already told my wife that I 
wanted a stripe, and she wasn't about to let me get away with wimping out. I 
tried to get some material called "Solartrim", which is a stick on film, but 
couldn't find any in stock anywhere.

It looked like the only option was going to be applying heat shrink film over 
the covering already there. I shrank from this task. Ha ha. Eventually it became 
clear that this was the only viable option, so I tried it on my trusty test 
piece, and it works! Iron temperature is critical here, but if you get it just 
so it sticks hard, and doesn't wrinkle.

It now looks beautiful. (to me anyway!). Of course all this finishing means it's 
getting heavier all the time, but we live and learn right? The fateful day 
approacheth, I'm running out of excuses. If the wind ever stops blowing on the 
moors it looks like the first flight is going to be soon.

Wish me luck?

Cheers

Nigel

It works.

Having run out of reasons not to, I took it to the field last Saturday. A very 
nice guy, name of John, volunteered to test fly for me, and after a bit of 
messing with the engine there we were, lined up on the strip, and both 
terrified!

Opening the throttle resulted in the Black Magic taking off like a scalded cat, 
and going vertical! It seems that we may be a tad overpowered here. Anyway, John 
stopped screaming, got it all sorted out, and commented that it required a lot 
of "up" on the elevator to keep it level. So we decided to bring it on in, and 
re-trim the surfaces. Except that when he closed the throttle nothing happened. 
Hmmm. 4 oz tank, .25 power, full fuel load. We could be here for a while. Then 
something starts fluttering earthward, having come away from the airframe. 

Now I'm really frightened! I went scampering off through the heather to find the 
missing bit, leaving John watching bemused as my creation becomes more and more 
uncontrollable. Anyway the inevitable happens, and it comes down. By a piece of 
inspired stick twiddling he got it down in one piece. The post mortem revealed 
that the missing bit had been the cowling, which contained most of the nose 
weight! The throttle not closing was due to a lousy installation job, no excuses 
here, just scruffy workmanship.

So, a thorough check, a bit of retrimming, and a better job of the throttle and 
cowling installations and we should be back in business. Then all I have to do 
is buy John a large scotch, and try to persuade him that adrenalin is good for 
you.

Notes for Angus! My plane came out (very) tail heavy, even with quite a big 
engine, think carefully about your CG when installing your gear. I used Solartex 
covering, and needed to get the servos as far forward as they'd go. Secondly, 
rethink your idea of using Velcro for the cowling fixing. The wind gets under 
here, and you've got a problem. Since I needed nose weight anyway, I'm going to 
beef up the fixing considerably.

Cheers 

Nigel.

    Well done! Nigel. Glad to see the bird flies. I sure hope you get some
    stick time next excursion.
    
    What with all your super efforts, I've been getting twitchy to complete
    my old Black Magic. I think I'll have to get number 1 son to bed
    earlier.
    
    Thanks for your advice about the Black Magic comming out tail heavy. I
    might not have too much of a problem as I have this dirty great big
    electric motor and an even bigger brute of a battery forward of the CG.
    
    As for the velcro, well I'd just about abandoned that idea and your
    comments have confirmed this as a wise move. I think some light nylon
    bolts are called for.
    
    The finish I have decided on is, errr, well, not as elegant or
    restrained as yours. As I want to actually see where my plane crashes,
    errr lands, I'm going for (blush) dayglo high visibility sun glasses
    are mandatory red, orange and yellow. I plan to use solarfilm (sp?) for the
    sheeted areas, and that superlight covering (that looks like tissue)
    for the open areas.
    
    Well done again,
    Angus

Angus,

Man, have you no taste?

Cheers!

Nigel

Dang!

Well, it crashes pretty well. My instructor was all lined up and ready to go, 
but we got a gust of cross wind during the take off. BANG. The really good news 
is that despite a fairly heavy contact with mother Earth the damage was limited 
to the nose area, and is now all repaired.

Actually, I find this quite reassuring, since the all built up structure looked 
like it could have been a pain to repair. It probably is too, but I think I'm 
going to have to do something really daft to test that theory!

Meantime, I've realised that I need something which can handle high winds a bit 
better, so I've started on a "Mascot" 4 channel job. I won't clutter up the 
disks with an account of the construction though!

Cheers

Nigel

I don't mind the "clutter". There is usually a useful trick or two in these 
construction topics that make it worthwhile for those of us reading along. 
You also have plenty of "free" advice about different techniques 8^)

Glad to hear the dings were minor. Now that you've gotten that first nick 
out of the way, you can get down to the serious business of flying the pants 
off it!

My father-in-law always used to say that as soon as you bought a new car, 
you went out with a hammer and put a small ding in it somewhere. Then you 
could relax and drive it.

Great Idea!

Lets see now, I'll just hit this wing with this hammer and......

Seriously though, I will provide an update on how my Black Magic flies, just as 
soon as I've worked it out!

Cheers

Nigel

Well, I've flown it some more, and reached some conclusions. 

Firstly, the beastie is well overpowered with the OS .25 in the front. Whilst it 
gives the advantage of a nice short take off run(!) it does make her very 
sensitive to throttle settings. The pitch changes quite markedly from half 
throttle to tickover.

Secondly, the inverted engine is a pain in the a***. I don't think there's a way 
round this, but if anyone's got any good ideas I'd love to know!

Thirdly, this is a light wind 'plane only. 

It's still a nice 'plane, and I still love it dearly, but I think I'm going to 
have to buy a smaller engine to get the best out of it.

Lastly, I've finished (and flown) my Mascot. I can thoroughly recommend this one 
as a first 'plane. The kit has to be the most complete I've ever seen (right 
down to the fuel filter!). It all goes together very easily, and seems to fly 
very nicely indeed. On the basis that the Mascot copes well with stronger winds, 
and this is Yorkshire in October, I think I'll put the Black Magic into storage, 
and fly the Mascot for a while!


Cheers.


Nigel

Angus where are you?

Did I upset you with my comment on your colour scheme? No, surely not. Come on 
man, get it finished!

Further excursions with the BM have confirmed my view that it's overpowered with 
the .25 (bodes well for electrics?). It's going to have to wait for something a 
bit more restrained in the power dept. A nice man's offering me a good deal on a 
S/H 4 stroke .25, so I might try that....

Meanwhile the Mascot's crashed as well. Big Tip everybody, make sure that your 
aileron extension lead isn't caught under the wing when you take off, otherwise 
it comes unplugged...... Took nearly a hour to find the wreck! Still, I'm 
getting plenty of repairing practise. I've also acquired a powered glider of 
doubtful parentage, featuring a small (.049 ish) diesel. 

I will now make the following observation, expecting to start a nice 
controversial conversation! :

"Diesel engines work by alchemy"

I am convinced that the fun here is all in getting the engine to run! It's so 
satisfying when it finally fires up and stays that way that I can hardly be 
bothered to fly. Luvvit.

Cheers and Merry Xmas everybody.


Nigel.

    Nigel,                         
    
    Absolutely not did you upset me with your comments on my colour scheme.
    I've simply invested in a set of dark glasses, trench coat and false
    moustache, so nobody can recognise me when I fly the dayglo wonder.
    
    No, more mundane things have got in the way of completing the Black
    Magic i.e. having to make my son's christmas present - a table, DIY,
    work, gardening, wine making, etc. However, once I complete my son's toy
    box, I have promised myself to make time to complete the Black Magic.
    
    Angus

Ah well, it's a bummer when real life intrudes!

Another small point that's perhaps worth noting. I had a (slightly) rough 
landing a while back, which broke the bulkhead to which the main U/C leg 
attaches. This resulted in the rear part of the U/C going for a wander up 
through the side sheeting. This is going to take a while to sort out! My feeling 
is that the damage is out of proportion to the impact, so you might consider 
"beefing up" the structure a bit here.

Cheers

Nigel

    I took one look at the design of the U/C and decided I didn't like it.
    Any landing load seemed concentrated into one small area on the
    bulkhead. The idea of sewing it to the ply via a series of little holes
    seemed daft as well. As I've modified the bulkhead by lightening it
    with cut outs I figured the kit arrangement wouldn't work for me.
    
    My solution is to have a separate U/C made out of a composite of
    aluminium sheeting and balsa. The whole unit is connected to the bottom
    of the fuselage either with rubber bands or a couple of screws. Any
    landing load is spread over a large surface area and more than one
    bulkhead/former. This method also simplifies the whole construction
    process.
    
    I made a test U/C out of the aluminium/balsa composite i.e. 3mm balsa
    epoxied between 0.5mm aluminium sheets. It was very light (1/2 oz or
    15gms) and immensely stiff. The only weak point was where I had to bend
    the structure i.e. I pre-formed the two aluminium sheets then glued the
    balsa between them.
    
                 View from front                     View from side
    
   Weak point-->  ---------------                      --------
                 /               \                    /       /
                /                 \                  /      /
               /                   \                /     /
              /                     \              /    /
             /                       \            /   /
             |                        |           |  |
             |                        |           |__|
    
    
    Another solution would be buy a sheet aluminium shaped U/C and drill
    holes in it to lighten it. I considered doing just this with the
    aluminium U/C from my Yamamoto trainer, only it wasa shade to large.
    I'm sticking with the composite as, being electric, I need to save all
    the weight I can.
    
    Angus

    If anybody is still reading this a couple of thoughts
    
    re -2.  this is a bit of a weak area.  After of few flights my
    undercarriage started to work its way through the fuselage.  I added
    some 1/4 balsa above the rear wire for it to push against and this has
    held up well ( even with my landings :-) )
    
    re -1.  sewing is a common method of fixing wire undercarriages in
    vintage models and normally works well.  I always add a bit of epoxy
    just to be safe.
    
    These models can be flown in high winds as you get more experienced
    with them.  When I built black magic I was concerned with the size of
    the rudder so I doubled it.  This makes it a lot more controlable when
    the wind gets up 
    
    Gavin