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Black Magic by Pete B


Pete B
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Agreed, Danny, A123's would be very nice but I'm a poor pensioner precariously perched on a pitiful pittance of a pension...........and shopping at P-P-P-Puffin's is out of my league...
 
As you'll see, I've resolved the Li-Po access quite easily, as it turns out, and of course, Li-Po packs can be used across my hangar, not just for one aircraft.
 
Anyway, some more progress has been made on the BM. Heeding Djay's advice, I've beefed-up the sub-fin by infilling the frame with soft 3/16" balsa and skinning it with soft 1/16" sheet:
 
 

1/8" dowels have been inserted through the sub-fin body to firmly peg into the fuselage:


The underside of the centre spine has been strengthened with a block to support the dowel peg (the rear peg into the joined fuselage framing):

 
 
This looks altogether more substantial than the plan version:
 

The tail-end of the fuselage has been lightly sanded to leave as much material as possible:


I'm reasonably happy with this now. The tailplane will be dowelled and glued into the sub-fin, with the fin also pegged with toothpick dowels into the tailplane. I shall leave out the diamond-shaped ply plate and try and avoid landing it tail-first!
 
 
Moving forward. the stringers were butted against some 1/8" sheet glued to the rear of F7
and 1/8" square used to infill between the stringers. Is this what you meant, Djay or would you suggest further reinforcement? I've just noticed that I have only 6 stringers and the instructions mention 8, so I hope it isn't going to look too skinny.........
 
Since taking this photo, I've also glued some corner fillets within the wing bay:

 

 
Servos have been installed, a little further back than I would have liked but mounting them further forward, over the battery bay floor, would have raised them enough to preclude a nice straight run to the rear. I'm using Turnigy S3317B's which at 19g and 2.5kg torque are plenty for this model - I've used them in a number of models and found them reliable, too:
 

That's enough for one post - more in a minute or two..........

Pete

 
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Battery access - often a head-scratcher when converting models originally designed for I/C - or even no motor at all! I'd seen what a few others have considered with the BM but my preferred option was to have a floor hatch.
 
Forward positioning of the pack is limited by the main u/c wire but it will be on or forward of the CG position and with a heavyish motor (C3542 1000Kv @ 145g) I am anticipating adding little or no unwanted noseweight, despite the additional weight with the tail strengthening.

I sandwiched some 1/8" and 3/16" sheet cross-grain, with ply formers at each end, to make a hatch. Having recently bought some diamond-tipped hole saws (at Terry Lynock's recommendation), I'm pleased to report they make very neat holes in all sorts of materials - including balsa! A ply lip one end, magnets the other:

 
Looks neat enough and covering will hide a multitude of sins. The plan shows the rear u/c wire passing inside the fuselage longerons. I preferred to mount them on the outside, stapled and epoxied to a cross-brace and then covered over with soft sheet, sanded to the fuselage profile. Th u/c wires were cleaned and bound with copper wire, then soldered, with a heatshrink sleeve to hide my soldering skills.....
 

The fuselage side sheeting having been fitted, the front floor block was glued and roughly sanded. I'm beginning to think I've been a bit too enthusiastic with cutting out the ventilation opening in the nose, as there is more sanding to profile to be done and I'm not sure there is enough material there. Leaving it as it is, it may end up looking more 'Brucie' than 'Black Magic' () so I may glue a bit of block either side of the chin to give me something to sand away.........:
 

This is just about how she looks now - more to come soon!
 

Pete
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Looking very nice Pete. All neat too - you give me something to aspire particularly as I type this with CA covered finger tips! Can't wait to see this one covered and ready to go! What a great hobby (or should I say 'way of life' this is!).
 
(Just back from 'aperos' at the neighbours - gonna catch up on my blog now!)
 
Nice towel!
 
Terry
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That's much appreciated from you, Chris, ta, but I've got to say it falls well short of some of the real quality builds going on, such as here!
 
I've been quietly watching the thread and there's a huge amount of very skilled aeromodelling going on - a great resource for any tyro builder such as me looking in - should be required viewing for newbies!

Terry, not another 'apero' evening! Stick to the blog then, no sharps tonight..........

Pete
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  • 2 weeks later...
Time for an update on the Black Magic, I think.
 
Next step was to make a removable motor cowling to provide access to the motor and ESC. Using the supplied bulkhead former, a second interim former and 1/4" and 3/16" strip glued to the nose block provided the basic frame. Clingfilm applied to avoid embarrasssment....
 
 
Nice, soft 1/16" sheet to cover the framework:
 
 
A dowel peg at the rear with magnets and washers to hold the front end securely. With hindsight, I've left the gap between the middle former and the motor mount former a bit tight but it should be fine if I bolt from the rear into the motor mount:
 

 
Lots of sanding later....and the cowling is complete:


Tailwheel wire bent and mounted:
 
 
Wing seating fashioned:
 
 
Here she is today. Tail surfaces have been covered but I'm awaiting film supplies and snakes before I can make any further progress. I did consider using pushrods as an alternative but the lateral distance from the fuselage to the tail horns has made this rather too dificult:

Having covered the tail surfaces in black Solarfilm, I couldn't imagine making it black all over - for one thing, I'm sure it would do an 'Icarus' in the sunshine we get out here
 
I have a colour scheme in mind - for revealing at a later date!
 
Pete
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  • 4 weeks later...

Back again for an update on the BM.

Yes, Barrie, I think the airframe often turns out to be the easy bit, personally - I find covering and finishing the most fraught part of the build! Nobody sees the work that's gone on inside when it is completed and, with my covering skills, I can't see me ever producing a concours finish! teeth 2

Having epoxied the sub-fin to the fuselage, the assembly has proved to be quite sturdy thanks to taking the advice received, so it was simply a matter of epoxying the tailplane to the sub-fin. I didn't feel it necessary to use the supplied diamond-shaped ply base.

The joint was reinforced with two 1/8" dowels through the centre line which were subsequently covered by the fin, which was also reinforced with two toothpick spigots. It's the last time I use black film - just like a car it shows every mark and speck of dust!:

Fin spigots

I haven't taken any photos of the covering process - I didn't see any point - but as a result of my chosen scheme having a colour-change the length of the fuselage, I used 1/2" wide strips of 1/16" balsa glued between the verticals along the break-line to give the Solarfilm some support. The lower half of the fuselage was covered to this break-line, then the upper covering was tacked along the line, using pieces of masking tape to keep it nice and straight whilst I ironed it on. Solarfilming the nose curves was a real pain.....

With the geometry of the tailplane, snakes were the simple solution and they were fitted before covering, being wrapped in masking tape and tacked to the fuselage formers to keep them as straight as possible. I've used the very cheap ones from GC and they seem fine.

Once the fuselage was covered, the side screens were fitted and, after a bit of cut-and-shut with a card template, the windscreen was installed. The curvature was such that I could not use canopy glue to fix it but I found that thin cyano worked perfectly, with no clouding of the acetate sheet. I finished off the screen joints with black Solartrim and it all looks fairly tidy:

Awaiting take-off

Propulsion-wise, it was a bit irritating when the first C3542/1000Kv I fitted screamed like a banshee when I connected it all up, so it was replaced with another, quieter example of the same motor.

Coupled with a Hobbywing 30A ESC and a 2200mAh Li-Po, with an 11 x 5 APC E prop, the powertrain produced 236W at 23A on a well-used pack, so it is in the region of 80-90W/lb, plenty for this type of model.

Balance-wise, I needed to put 49g of lead into the nose beneath the motor to set the C of G at 70mm from the leading edge, for an AUW of 1364g or 3lb, including battery pack.

Now, the model isn't yet finished (decoration and undercarriage in-fill to be done) but I was getting a bit keen on seeing how she flew, so today, once the screen was fitted, I couldn't resist the temptation to have just a little fly............angel 2

Range checks done, in calm air but rather gloomily overcast, I opened the throttle and off she went:

Take-off!

Whoops, that post was too big, so I've had to cut it.....back soon!

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In case anyone is thinking that the colour scheme looks familiar, I've based it on the Shuttleworth Dessouter:

In the air 2

I have to say it was one of the least exciting maidens I have experienced - a touch of down trim to set her nicely flat in the air, but on half-throttle, she was climbing out and describing a gentle turn to the left under torque - as a vintage model should! smile


Climbing to height (and at full throttle it is, err, almost vertical.....embarrassed), switching off the motor produced a steady glide, a little steeper and faster than I expected, but with reasonably good rudder authority. Loops need a fair amount of power as she runs out of steam very rapidly.

Looks very smart, doesn't she? smile p

In the air

Landing was very straighforward but I shall have to work on a suitable approach speed as I ran out of up-elevator to flare her and she drops quite rapidly once airspeed is lost.

I have to say that rudder/elevator control is a rather a lazy way of flying - all I had to do was steer her around the circuit - the rest she did for herself. Perfect for those warm summer afternoons!

Now, I've just got to explain to Terry Walters why he's found out about the maiden on the forum - he's expecting to witness it Friday when he comes up for the afternoon.........smile owink 2

Pete

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Well done Pete another one takes to the skies - sometimes you can't resist it and it has to happen! Looks the true vintage aeroplane doesn't it. Will it be present at the Mass Vitage Build Fly In?

You'll have to do your explaining to SWMBO!wink 2

See you later - mind you we have light rain here at the moment! The forecast doesn't look too bad but not as good as it was.

Terry

Edited By Terry Walters on 24/02/2012 07:40:14

Edited By Terry Walters on 24/02/2012 08:05:40

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Hi Pete,

Looks fantasic and something for me to aspire to!. My build has slowed, busy at work and very busy Decal making following the mention in Switch On of the launch of http://www.modelmarkings.com in the lastest of RCM&E.

The fuse is ready for covering, just need a trp to the LHS for a elevator snake, the bits box failed to find one long enough, and like you struggling with the front windscreen, the template I have now looks ok on the nth attempt, but will wait to fix until its all covered.

I have made a start on the wings, at least that is a simple build, and a few evening should see them completed.

Balance point will be interesting, my motor is lighter, but using a heaver battery than you , so hopefully no need for any fishing weights!! 3600mah. Where did you place your battery?

 

Tim

 

Edited By 35mhz on 24/02/2012 07:51:07

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Thanks, gents - I'd dearly like to get it to Greenacres this year but it's by no means certain.....

Tim, the battery is fitted with its front end against the back of the main u/c ply former(F2):

Underside

I've just looked at the box lid and I see the designed AUW was 4lb which means mine is 33% lighter than spec. If anything, I've beefed-up certain parts over the original plan, so how Flair arrived at that figure is beyond me. At that weight, I reckon it would fly like a brick! As the pack is very close to the C of G, I don't think a larger one will affect anything more than the airspeed.

An 1800mAh pack would, I think, just fit in the bay in front of F2 (a bit tight for the 2200) and that may mean less lead up front.

Pete

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Pete,

Thanks for that info, my battery is planned to go behind the motor firewall, but I have a feeling it might be a tad nose heavy!! its a dual 1800mah, I guess I can go with only 1 if need be.

 

As for weights my target is for sub 3lbs, I have a copy of the original 1947 article, and I note that the magazine build freefligher was a mere 36 ozs

Edited By 35mhz on 24/02/2012 10:09:53

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  • 3 months later...

A friend has a damaged Black Magic - I reseum it has been repaired a few times until it is not correct! can you advise if there is a plan copy on the net as I would like to repair it for him but want to check wing seat and the front end. A plan wwould be most helpful!

It orgionally had an OS30 four stroke which I have since obtained!

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Hi Dereck,

 

If you PM me your email, I have a pdf copy of the 47 plan and also the later electric redrawn version, the one I am building!! I can send you.

 

Still building mine!!

 

Tim

Edited By 35mhz on 25/06/2012 11:23:43

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  • 2 weeks later...

yesI have been reading this thread with interest ,It's rather got me motervated to start another build ,I still have the plans for a Lanso Record breaker i built some year or two back ,I still have my old merco 61 ,never had any problems with it .The last lonso i had i sold becouse i was'nt happy with the finished item regarding the finish .afte i had to chop it about to acomadate some leade up front plus some other finish issues i did'nt like.so i think i will build another but much better ,sorry i knw this is a bit off topic Pete you'r doing a grand job all i can say is BLUE SKIES to you m8. Bernie

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  • 12 years later...

Hi All

I'm a disabled flyer, not really a builder but have been searching for a used Black Magic for ages, so anyone know of one not being flown or unwanted and preferably electric i would be pleased to hear about it

Cheers John Bell

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