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A Little Atom, A Medium Mossie and a Big Cub


Chris Barlow
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After messing about for what seemed like hours this evening programming the ESC's and TX (props removed for safety) I made up and connected the control linkages starting with the aileron pushrods. These were made from off cuts of pushrods cut to legnth and the first job was to re-thread the ends.

An M2 die is a worthwhile investment This one was kindly given to me by a guy at our club and is kept in it's pot bathed in cutting fluid ready for use. First a very slight bevel is filed on the end of the rod and the die started carefully to get it square...

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The die is then "screwed" down the rod. Because it's only 2mm it's easy enough to turn with fingers and a die holder isn't necessary.

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And if the die stays straight and unscrews neatly you should have a nice M2 thread...

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A clevis is then screwed onto the new thread and then offered up to the aileron horn and servo arm and maked for legnth. Z bend pliers are then used to form the servo end.

Before...

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After...

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The hole in the servo arm is opened up to a snug fit around the rod and the linkage can be installed.

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The elevator horn was fitted and the clevis screwed onto the end of the now installed snake.

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And the same for the rudder

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Those horns will be painted to match the colour where they're mounted!

With the props still removed the TX and RX are turned on and the linkages setup as close to neutral as possible.

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A short bit on the detailing and weathering. I've never really liked having clean and shiny models especially military planes and warbirds. I prefer them to look very used and if possible returning from a mission somewhere with leaks, oily exhaust residue and sometimes some battle damage.

I also like to see it on the plane when I'm flying it so weathering needs to be accentuated a little to make it stand out a bit in the air.

So first some detailing. external fuel tank filler caps were formed with brass tube dipped in acrylic laquer then transfered to the tank to form a ring. This was done again with a smaller tube to create the raised filler cap. Rivets were added in the most distinctive places with piano wire dipped in laquer. The panel lines on the leading edges of the wings, sides of the engines and armout on the nose were raised first by applying fine line masking tape then spraying extra primer over it. When the tape is removed it creates a raised edge. This and other non raised panel lines are enhanced with a very thinned mix of black paint sprayed against the edge of a strip of acetate so that the hard edge is on the panel line and the overspray lies downwind or below the line. Oil spots/leaks are sprayed with the thinned mix holding the airbrush stationary to get a small pool of paint then raising the brush and pulling the trigger a little more to get a dispersed trail behind the origin of the leak. Weathering and exhaust residue was sprayed randomly and built up in some areas to make it darker.

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Not as clean and shiny as Phils Spitfire but a few landings on our strip in the mud and sheep residue and it wouldn't be anyway. At least the sheep residue is green and won't stand out too much!

The gun detail has been finished and painted and to be honest I'm quite pleased with them!

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Thanks John. The guns were especially for you! wink

A couple more photos before rolling out the Super Cub plans

Final job (almost) is a coat of clear satin varnish. I've used Ronseal fast drying interior varnish, with Diamond hard technology, no less! This was thinned approximately 20% with IPA for spraying. I like how it goes on a milky blue colour before drying clear.

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Tonight straight in from work I deputised my little girl to model the plane in the sunlight for me. I think I'll also get her to model the Super Cub too. It'll dwarf her! laugh

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With the Mozzie still waiting for her maiden I've made a start on the Cub.

This is a DB 79" Super Cub but will have flaps, slats and Tundra wheels. I also have a couple of other alterations in mind to the plans but will have to see how they pan out.

First off the cockpit sides were cut & jointed and some balsa sheet stripped down for the framework. These bits were assembled on the plan to form the basic fuselage sides.

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The rear cockpit former (F8) was glued up and other formers cut from ply on the scroll saw.

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The plan features beech engine bearers with a paxolin plate but I intend to use a conventional nylon mount. Because of this I need to build the thrust angles into the engine bulkhead. The down thrust is already designed in and the side thrust is achieved by cutting the starboard fuselage side back by 3/16's at the front.

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The built up former F8, the 2 lower formers F4 and F6 and forward former F3 (not shown) were then glued in. The cockpit front former F5 was fitted but not glued at the moment as I was considering making operational doors.

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The engine bulkhead F1 was then glued in along with strengthening triangular stock. With the omission of the beech engine bearers it is now possible to mount the fuel tank centrally and to provide extra strength a 3mm ply tank shelf was cut to fit between F1 and F3

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When set the developing fuselage was then pinned down onto the plan elevation on the, erm, plan and cross bracings, rear former F13 and top formers added.

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So far all nice, straight and square.

Edited By Chris Barlow on 18/03/2015 02:00:03

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CHRIS ! A .VERY NICE JOB ALL ROUND. YOU HAVE A SCROLL SAW YOU LUCKY DOG .HOWEVER I FOUND A ROUTER WITH ROUTER TABLE IS AS GOOD OR ALMOST SO. WITH SOME INGENUITY AND BITS OF KIT IT IS VERY VERSATILE AND COULD EVEN SUPPLEMENT THE SAW. MY MOST OFTEN USED CUTTERS ARE THE THIN TRIMMING CUTTERS. PLY, PLASTICS, METALS ( BRASS, COPPER, ALI, ETC ) INSIDE AND OUTSIDE SHAPES A DODDLE. REPETETIVE HOLES ( LIGHTENING, PORTHOLES etc   WITH SIMPLE JIG (S ) EASY AS. L.E. ,/ T.E. MOULDINGS CHEAP AS CHIPS MAKING YOUR OWN. CUTTERS FOR EVERYTHING EVEN MODIFY SOME FOR SPECIALS. TRY ONE IF YOU GET THE CHANCE PLENTY OF GOOD 2nd HAND ONES ABOUT ON E-,BAY, CASH CONVERTERS . et aL. MODS ! SORRY TO GO OFF ON ONE BUT THOUGHT IT WORTH A MENTION/ IF NOT TO CHRIS TO SOME OTHERS PERHAPS.

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Cymaz/John I've been itching to start this one since December!

onetenor, the next tool for the factory will be a sander/linisher!

With a mind to adding a door in the side I realise this may affect the strength of the wing seat which will be beefed up a little to take plug in wing halves and top hatch. The side windows were cut from 3mm liteply instead of 1mm ply.

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With an opening window on the other side.

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The rear spine was added...

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and the undercarriage mount made up from 2 layers of 3mm lite ply arranged to form slots for the wire legs. In clamping the undercarriage mount the roof/wing seat was put under it's first strength test, which could have gone badly wrong!

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At the same time the chin and access panel sides were added.

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The holes were drilled for the fuel lines from the tank which will be cushioned with foam blocks

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Next up, mounting the engine.

Edited By Chris Barlow on 20/03/2015 02:07:55

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The plan uses hardwood engine bearers which I have omitted in favour of using a nylon mount and building the side thrust angle into the bulkhead. Because of the side thrust the engine mount can't be simply bolted to the centre line and has to be offset to ensure the prop shaft exits the cowl on the centre line. Measured from the drawing this side offset is just a smidge under 5mm.

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The engine is secured to the mount with M4 bolts screwed into a 1/8th hole drilled in the mount. The 2 forward bolts will be additionally secured belt and braces style with nyloc nuts with a smear of blue threadlock before final assembly, but not red threadlock, that would just be overkill!

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The throttle pushrod hole was also marked whilst the engine was in position.

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The engine mount is secured to the bulkhead with M4 bolts into captive nuts secured in place with a drop of thick cyano

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As the bolts are tightened they pull the prongs on the captive nuts into the plywood. The bolts are then removed one at a time and cut down to finish flush to prevent damage to the fuel tank.

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Realising it was after 1am the last jobs of the evening to add a ply support to the cockpit roof and a 1/8th balsa tailplane seat to join the end of the tail.

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Update on the TN Mosquito which flew this afternoon! It was balanced to the plan CG which made it a little tail heavy. After twitching around the sky for a couple of minutes we brought it back in for adjustments. The foam padding was removed from inside the nose and the battery slid nearly all the way in. Second flight was much nicer and was trimmed upp pretty much as well as I could get it in the wind. The yellow spinners stand out really well in the air and below the tree line, like two yellow dots flying straight at me!

Landings were surprisingly slow even without flaps but on the second landing the mass balancer on the elevator caught the grass and pulled the elevator out, spotted by Paul and determined after a short analysis! It did make a quiet "crack" on landing which I put down to the battery hatch moving on touchdown. So a minor repair to be done and flaps and single engine performance to be tested yet but so far alls well!

Tony Nujhuis 47 Mosquito

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It's been a week of head scratching, hours of thought and many drafts sketched on paper but I finally have a plan and some progress on the Super Cub!

The week started easy enough by making a start on the wings. I started by making a template of the ribs which has been modified slightly to increase the chord of the ailerons/flaps. The plan only has ailerons so adding flaps has reduced the aileron area.

I would usually cut the ribs rough then cut and sand them as a block bolted together but for the cub I decided to final cut each one from the template.

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I have planned to make the wings bolt on so a wing tube will replace the 2 ply braces on the plan. To get the correct dihedral the first few ribs have holes in a descending angle for the tube.

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And labeled before they get mixed up & glued in the wrong place!

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Then the hole is cut with a compass cutter

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A second rib template was cut and lightening hole cut in the ribs which saves 10g/wing. I know, I weighed the cutouts to see if it was worth the effort!

With all the ribs cut the wings are quick to assemble. Due to a shortage of 1/8 ply I left out the root ribs at this stage.

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Now the head scratching began!

I had decided whilst building the fuselage that I wanted a working door in the side of the cockpit but when it came to building it in it became apparent it wasn't as straight forward as it seemed. During the day at work I had resigned myself to not having a door but when started again in the shed that evening I mentally told myself off for shying away from a difficult modification to the plan and got it sorted out!

The same situation occured with the leading edge slats. My plan was to have working slats/slots but when I started thinking about how to go about it I started thinking how much easier it would be to have fixed slats! Working slats would give me a slightly greater speed range but other than that they wouldn't do much other than be a "toy" to play with on the transmitter! After another mental dressing down I set about sketching ideas to make working slats!

One plan was to have a 6 servo wing, another used springs set to pressure from the airspeed and another plan was to use electronic pressure sensors controlling automatic servos. I settled for an idea to have a torque tube running the length of the wing driven by a high torque servo and take off horns down the tube to drive the flaps and slats together. This meant lots of more accurate drawing to work out the tube position, horn lengths and linkage lengths/angles to make it all work!

This is the final drawing that didn't get screwed up and thrown over the dark side of the bench.

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Withe the drawing I now knew the shape of the leading edge of the wing behind the slats so could modify that part of the wing, cutting the affected ribs off yet another template, and start skinning the D box

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The slat was laminated up from 2 pieces of balsa, pinned temporarily in place and the 1/4 leading edge strip glued on.

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Note the clear polythene behind the slat to prevent it from being glued to the wing!

When dry the leading edge of the slat was cut through and the slat released.

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This had added a 3rd lamination to the slat.

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And a step in the leading edge of the wing.

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Whilst waiting for the glue to dry I had also added the wing tips.

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The slats will be operated via carbon pushrods running in carbon slides built into the wing. These need to be very accurately positioned to ensure they run parallel to each other and at the same downwards angle. Brass tube was flattened at one end to form the connection between pushrod clevis and carbon pushrod.

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After sanding the slat and leading edge the slat was repositioned and a drill bit used to carefully make the hole for the carbon rod.

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Before glueing anything up the angle and operation was tested.

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So on its own it all seems to work OK. Now to see how this torque tube idea works out!

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