Black Magic Plan Build

[Tim C]

The Postie delivered a package of goodies from HK, just 6 days after ordering, speedy service to the UK, I have had to wait up to 30 days before now.

Included in the goodies was a nice 11x7 wood light electric prop, the wheels, I went for the 2.75 inch, rather than the plan 2.5, as the flying field is less than bowling green smooth. The wheels are better and nicer looking than I had expected, and lighter at 23gm, far better than the lead efforts in the local LMS. I did spot a tail wheel (3/4 inch) in the LMS which will look better than the plastic sponge variety.

The Motor is an 850 KV, weighs in at 110gm, a slight larger version of the DT 750, which is good at swinging large props at up to 200w, hopefully the bigger motor will be more suited to the Black Magic, its rated up to 350 watts or more, so should be more than ample. Testing will see if my prop choice guestimate was right!!, ideally I am looking at 250watts or so. I will replace the long threaded shaft with a shorter blank one, more suited to the prop adapters I will be using, it an easy swap, std 4mm shaft.

Now the build can start!!!

 

Edited By 35mhz on 20/11/2011 21:50:31

[Pete B]

Looking forward to your start, 35 - I'm not in a position to get under way with mine (also leccy) for a couple of weeks, so I'll be paying attention!

Pete

[Biggles' Elder Brother - Moderator]

Nice bits 35 - they just need an airframe wrapped around them now!

 

BEB

[Tim C]

A cutting session , a couple of hours had all the wing ribs cut, together with main balsa fuse formers. I cut out the ply formers, 3mm birch ply for the main F3 which has the U/C attached, and 3mm light ply for the others, none of which are structural.

I left off the motor mount, as the plan drawing if for a speed 600 and GB mount, and I will have a firewall mount, once I have determined the exact position and can cut this to size, but no need to do that yet, easier to do once the main fuse Frame box is assembled. I also got out the balsa stripper, and cut the main 1/4 x1/4 longerons, 1/8 stringers and other sizes of strip needed, I am sure I will need more, but this will ease the way one the glue pot is opened. I was surprised by how little wood was actually needed.

[Tim C]

I bent up the main wire U/C, so I could pre drill the holes for the wire mounting. I used a bit of copper wire scavenged from a piece of scrap 2.5mm lighting circuit power cabling, more than strong enough, just twisted through, though I will dab a bit of solder on later as insurance.

[Former Member]

[This posting has been removed]

[Tim C]

Finished up the side frames , all very straight forward construction of 1/4 square strip, less than hour to make both sides. Just pin the top and bottom longerons to the plan, there is a slight bend in the bottom, but the wood has enough bend in it for this not to be a problem.

Cut my own strips, selecting wood with adequate strength particular for the longerons

Its worth checking that the longerongs will also bend on the other direction as well and that there is no weakness in the wood, as you will be pulling the two sides together at the rear, with a bend just behind the cabin, best test now than after the sides have been made to avoid that cracking wood sound.

[Tim C]

Tonight completed the fin & rudder and most of the tail area and elevators.

Hinging was a bit though provoking, but settled on little micro hinges, they are nominally 2mm, but find using a 1.8mm drill you can make a hole in 3mm (1/8) sheet used on the tail, but the 3/16 sheet on on the rudder is no bother and is easier to do. Just keep the drill nice and square to the wood and take your time.

I tapered the rudder section with about 1/16 thick TE, at least is sheds a gramme or two from the tail.

I think I boo-booed on the elevator, not reading the plans!! and the original plans not a lot of help as the had no elevator!!, just a fixed tail. The mid sheeting should go all the way back to the elevator TE, I guess trapping the elevator joining wires, ideas here welcomed!!!

Still a bit a shaping of the elevator tips and tail wing tips to give a more rounded line

[fly boy3]

Hi 35,Just a thought, can the elevator be a one piece type, hence no wire joiner. Cheers

[Tim C]

The design will not permit a one piece elevator, the original free flight design and later 1ch RC had a fixed tailplane. The missing fillet is actually above the fuse, not behind it.

 

I am going to use a u shaped wire joiner in a tube as a bearing and epoxy that on to the tailplane. A fillet of depron will be 'clamped' by 1/16 sheeting as per the plan. I will need to cutback existing top and bottom sheeting to give it enough surface to bond to.

[Danny Fenton]

Hi 35Mhz...... plastic hinges...... depron whats all this hi tech stuff

Looking really good, its a real trip down memory lane building these old timers Every modeller should do it every now and then

Cheers

Danny

[Tim C]

Made the joiner tonight, small piece of brass tube and wire bent to U shape, cut a fillet out of balsa, having been shamed out using modern depron, epoxied in place. All nice a free running and no slop.

[Danny Fenton]

Was only teasing 35, just trying to protect you from the rolled up Keil Kraft catalogue wielding brigade

 

I should have used a wire joineron my mamselle, would be easier to hide than the flaming bamboo stick I used

Cheers

Danny

[Biggles' Elder Brother - Moderator]

Good progress 35 - looking good

 

BEB

[Big Bandit]

35,

 

Looking good, a mate has just built one and struggled with the rudder link, be interesting to see how you get on. Keep up the good work.

 

Cheers,

 

Chris.

[Tim C]

Not much building progress this week, manic week at work! and last night at the club indoor 'Chuckie' night, where I managed all of a 6.25 second flight in the endurance, good enough for 2nd place!! with my 20 inch throw glider.

I managed to change the threaded 4mm shaft on the motor for a shorter non threaded one, I reckon it will still need 10 to 15mm cut off the shaft to get the motor mounted as far forward as possible and not have the prop protruding to far forward.

I also reamed out the prop and tested out the motor on the watt meter, My predictions were nearly spot on with the 11 x 7 prop, 250watts settling down to 225 watts full open. I did not measure the RPM

[Tim C]

Finished of the tailplane, sanded down and finished of the fillet.

 

Also managed to get the basic fuse frame boxed up and the F3 Ply U/C former 'expoxyied' in. No real dramas,it all went together well, and nice a straight!!

 

Now begining to look like a plane

 

[Tim C]

Some forward progress over the weekend.

 

Glued on the fuse formers and the stringers, all pretty straight forward, apart from the usual broken stringer from ham fisted handling!!

 

 

I measured up the front where the motor mount bulkhead was to go, drew up a former in Corel draw and printed it off as a template and cut it out of 3mm ply. I have used 3mm blind nuts for the motor back plate. I have not glued this in place yet, as will wait until construction has advance a bit further, I will build in some down and side thrust, any further fine tuning will have to be with packing on the motor mounting plate.

 

I have decided to go for a top hatch to give both motor and battery access, The holes in the formers give me a variety of possible battery positions depending how the CG works out. The hatch is just 1/16 soft sheet over a couple of false formers. I will probably add a false former behind f3 to fix the screen to.

 

 

I have also made a start on the 'Use balsa block and sand to shape' front of the cowl, still lots of shaping and sanding to get it presentable!!!

 

[Donald Marriott]

A few weeks ago I started building a Black Magic kit from a David Boddington Kit based on a Aeromodeller plan I have had the semi kit for about 20 years or so, the stage I have reached is about on week from covering , I shall use Solafilm as it will be powered by an electric motor. I would have liked to have it in a free flight format, however, due to the shortage of space for this type of flying it will be assisted with elevator and rudder and a speed controller for the motor..

Kind regards

Donald Marriott

 

 

[Tim C]

Welcome to the Black Magic club. Seems this model has a history. A club mate on hearing I was building a Black Magic, commented it was as a youngster to model he coveted but never had! 1 channel RC was financiall;y out of reach and had to be content with CL models.

 

Any way progress is slow at the moment, sheeting in the front sides, sanding the front and bottom cowl blocks to shape and finishing off the U/C before sheeting in the underside. I am dispensing with bottom hatch, I dislike having to turn model upside down to get at the battery, the top hatch cowl and access through the cockpit gives all the access need to the gubbins inside.

 

Doodled this as a period decal/logo for the Black Magic, thinking of producing it as a waterslide for the tail

[Tim C]

Some progress to report.

 

I made the rudder linkage from some 2mm wire and made and soldered a brass linkage to attach the pushrod (the tape holding it while the epoxy dries)

 

I used Starloc connectors for the wheels, much less intrusive than the screw on stops. The Axel's are brass tube, with a washer on the inside, and they just push fit on the piano wire UC

 

I haver covered the tail, and used cocktail sticks (useful 2mm dowel!!) to peg the fin to the Tail plane, still to be glued. I will also peg the tailplane to the fuse with 3mm downs to provide some reinforcement, as gluing surface is limited.

 

I angled the elevator end slightly to give more rudder throw, the considered wisdom of my fellows at the C&DMFC meeting last week when shown the part complete model was 'more', advise heeded, as the rudder surface is pretty small

 

 

I have fitted a servo tray in the fwd cockpit, low down, and will fit a suitable pilot figure on a removable tray, so all the gubbins will be hidden

 

I have trial fitted the motor, but as yet not epoxied the ply mounting plate, that can wait until later. The front Cowl is pegged and held with a couple of magnets, as will be the top hatch

The not so pretty underside , all sanded to shape

 

Edited By 35mhz on 10/01/2012 22:22:55

[Steve W-O]

Looks good, moving quite quickly too.

 

 

Interesting to see someone else uses Coreldraw for planes, I use it all the time, to draw parts for cutting, or to redraw whole plans. Use it for many other things to, best dtp programme I have ever used, beats anything on the fruit machine any day

[Pete B]

Still following your build, 35. I have to admit to a certain amount of head-scratching over the tail end in particular and it's interesting to see how, with the same model, different solutions to the construction still end up with a successful result, hopefully!

I've yet to find out whether mounting my battery further back than yours will need additional weight in the nose. What size pack are you thinking of using?

Pete

[Tim C]

Pete,

 

There still a bit if infill to do in the tail, mainly to get some smooth transition for the covering, some form of pegging is IMO required to prevent hanger damage to the tail, it is large and will bound to get knocked!!

 

Hmm!! Battery position, I have been avoiding that one!!. The original premise, was with a shortish nose lots of up front weight would be needed, particularly with a motor just a tad over 100gm. There are hopefully options on final battery location depending on what is needed. Plan A is use 2 x 3s 1800mah which will plumb in nicely behind the firewall, but I have got other battery should this prove wrong!!.

 

As it stands in the pictures with the tail attached, without battery, but with motor and servos, the CG is ahead of the recommended point!!, but wing and covering to go, which will shift it back

[Tim C]

Well finally back to finishing off Black Magic.

I need some advice on the best way to cover the fuselage, I have covered the forward sheeted areas but am unsure the best way to tackle the rear. Should I start top or bottom? how best should I divide up the sections?, do it in 1/4s or what? Help and advice please