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A Little Atom, A Medium Mossie and a Big Cub

3 builds in 1 blog.

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Chris Barlow30/01/2015 00:24:22
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1791 forum posts
1211 photos

By adding flaps I have removed the option of controlling the ailerons with a torque rod as detailed on the plan so they will have to be operated directly from servos in the wing. Unfortunately the wing is too thin to build in servos although thin wing servos could be used if left projecting 3 or 4mm.

I could have mounted them in the engine nacelles but the outer flap would mean a crazy angle for the pushrods so the remaining option was external wing fuel tanks. These were blocked together from scraps of 3/8ths balsa from the wing off cuts. 2 templates were drawn for plan and elevation profiles, drawn onto the hollow blocks and cut/sanded to shape. A cutout was also formed to suit the servos with a Costa coffee stirrer cut and glued to the inside to screw into.

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The servo lead extension has to somehow get to these servos and my initial plan was to push them into a 2mm slot in the thicker part of the wing. I had some concerns about the wing splitting because of this slot so opted to rout out a shallow 6mm wide groove and set the lead in flat. This was tacked down with cyano then the entire groove filled with thinned slow setting epoxy which will bond the glass cloth back together and form a 3mm thick spar along the underside of the wing.

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The servo is positioned on the inside of the tank so that it will be hidden by the engine nacelles.

The radiators were formed but cutting 8 formers from 1/8 balsa and slotted onto the wing. These were covered with 1/16 balsa sheet top and bottom and will form a route for the power and servo leads to the esc's in the nacelles.

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The gap where the sheeting meets the top of the wing was bevelled with a little light weight filler which will reduce drag through the radiators and allow the air to escape under the wing.

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Chris Barlow30/01/2015 00:27:20
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1791 forum posts
1211 photos

Thanks John. I try to be neat and precise but you should see the state of my shed when I get engrossed in a build or three! blush

Chris Barlow30/01/2015 00:41:36
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1791 forum posts
1211 photos

Access to the motors and ecs's is through a hatch in the top of the nacelles. I saved cutting these until the airframe was glassed and had a 2nd coat of finishing resin so I wouldn't have to cover the hatches seperately.

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With the radiators added it's looking more like a Mosquito!

The entire airframe was next sanded with 120G to flatted the 2nd coat of resin and provide a key for the filler primer. All dust was removed by blowing it off in the doorway with compressed air then the airframe was wiped down with a tack cloth.

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A coat of filler primer was applied by brush to get a thick coat od left to dry and harder for a couple of days.

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Chris Barlow30/01/2015 00:53:18
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1791 forum posts
1211 photos

After allowing the primer to harden about 95% of it was sanded off, leaving the paint in any low spots, dimples or weave in the cloth missed by the 2nd coat of resin.

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A closer look shows how the primer is used to fill imperfections, even deep scratches left when sanding.

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Tonight it was time to add the flame suppressors to the engine nacelles and start to address the cooling issues for the motors/esc's. The suppressors were cut from 1/4 balsa and hollowed out with a round file. The hollowed out channels don't pass straight through and are chamfered to scoop air into the nacelles.

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The positions were then marked on the sides of the nacelles and holes formed with a Dremel, one at the front for cold air in and one at the back for warm air (hopefully not hot) out.

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The suppressors were then glued into position and the ducts opened up a little.

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Rear view. If the ecs's or motors ever burn out in flight it will look like a very realistic engine failure! surprise

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Edited By Chris Barlow on 30/01/2015 00:54:00

Edited By Chris Barlow on 30/01/2015 00:54:36

Martyn K30/01/2015 08:48:59
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4811 forum posts
3498 photos

Great blog Chris, it's coming on well

M

Chris Barlow30/01/2015 17:33:22
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1791 forum posts
1211 photos

Thanks Martyn. Hoping to get some paint on it this weekend and make a bit of a start on the Cub during drying time!

Chris Barlow08/02/2015 15:52:31
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1791 forum posts
1211 photos

A couple of minor bits finished last night on the Atom before attempting a maiden this afternoon.

UC wires and mast painted in Humbrol silver.

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And a simple centering device for the castering tail wheel, just an elastic band looped around the uc leg and secured to the central fin with a bent wire pin.

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Then on with the maiden.........

Chris Barlow08/02/2015 15:56:55
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1791 forum posts
1211 photos

Oh and a final photo of the finished article. At this point it's either an autogyro, a doorstop or matchwood. (or spares for the second attempt!  

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Chris Barlow08/02/2015 16:43:28
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1791 forum posts
1211 photos

So onto the first maiden of my 2015 mass build models. I really like maidens. Some models you really don't know how they're going to behave and if they're home built with some care you really don't want them to fail either! My theory on the Atom was that having experience of helis and planes it should be somewhere inbetween both and I should be able to fly it to a reasonable standard. Hmmmm.

So after a simple message to Paul Marsh " Do you want to see a tangled crash this afternoon? " we went up to the field.

To say it was a bit foggy in Cheshire would be an understatement. We took up a couple of foam wings which disappeared into the mist at between 50-100ft, variable! Even LED lights weren't helping much up there!

Still, I wasn't expecting the Atom to go that high so after a few checks and rates adjustments Paul spun up the blades and I rolled off for takeoff. It lifted off too soon as I have seen in many videos and started a brief roll to the left which was countered with right aileron, rudder and a touch of down elev. That was enough to stop the stalled, clattering crash and a second after it was lifted up into the air, nose rising, and rising, and rising! Put in more and more down elevator and right aileron to counter the now slowing and stalling rotor disk! Levelish flight was resumed but the rotor had slowed to much and it was coming down from about 10ft. It hit nose down and the crack was so loud I suspected at least the mast had snapped, if not the tail boom as well.

Recovery revealed it was just the prop, everything else was fine so a new prop was fitted and trims adjusted ready for a second attempt. Again Paul spun up the blades and I gradually increased the throttle. This time it was easier to hold on the ground until the disk was up to speed then with no elevator input it lifted up on it's own. A little right aileron and up elev and it was away, slightly nose up. One circuit later and a few clicks more of down elev and proper flight was established. Left and right turns were very similar to flying a helicopter with a bit of rudder coordination required. A couple of fig 8 circuits and time for a landing.

When the Atom slows down from forward flight significantly more movement of the sticks is required to maintain control but it's not excessive or frantic, just small quick corrections very similar to transitioning to the hover with a heli. The Atom floated in at a slight glide angle just above walking pace with just enough throttle not to loose rudder control. At about 4ft off the ground I reduced throttle a bit more and flared back to arrest the forward motion, right aileron to balance the slowing disk and it floated down to a gentle vertical landing.

Second flight was even more fun than the first with several slow flybys' and another vertical spot landing. Even better, Paul videoed it with my Hudl which I'll put up as soon as it's uploaded.

Many thanks to Richard for a design even an autogyro novice can get to fly and for doing the development and crashing for us (I have seen the early videos!   and thanks to Paul for braving the cold and rediculous fog to help me. Finally good luck to those yet to maiden. The Atom flies like a dream, just don't let it lift early on the take off run and keep the rotors spinning!

Video soon. laugh

Chris Barlow08/02/2015 18:03:41
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1791 forum posts
1211 photos

Video of the second flight.

john stones 108/02/2015 19:48:42
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10275 forum posts
1475 photos

Nice work Chris and Paul with the camera yes

John

Richard Harris08/02/2015 20:13:51
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2011 forum posts
1846 photos

Chris,

Fantastic build and text book maiden, you have got to pleased?

I would be interested to know from someone who flies both Helis and fixed wing, is it a cross between both like you first thought?

Chuffed Rich

Chris Barlow08/02/2015 21:26:53
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1791 forum posts
1211 photos

Richard, you should be chuffed to bits. For someone who's never built an autogyro this design is easy to build and mechanicaly sound. It works and works well!

For some reason I was expecting a nose down attitude to maintain forward flight and head speed but realised afterwards it doesn't because the rotor isn't producing the thrust. Other than that it was pretty much as expected, but much easier to fly than a heli.

Throttle still controls height, just not as instant as a heli and shallow bank turns are initiated with aileron closely followed by rudder to keep the tail following the nose. Needs less rudder as the bank angle increases.

I would say that if you can fly circuits and fig 8's with heli and fixed wing you're not going to have any problems at all. If you only fly fixed wing but do use rudder in coordinated turns you'll be OK just be quick on the sticks in the hover. If you fly fixed wing & never use rudder i.e yank 'n bank, then learn to use rudder!

Martyn K09/02/2015 13:31:20
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4811 forum posts
3498 photos

Brilliant. Cant really fault that flight can you

M

Chris Barlow09/02/2015 19:56:46
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1791 forum posts
1211 photos

Thanks John, missed your post above Richards!

Martyn, for my second flight the roll to the left still caught me out a bit. Must remember to hold in some right aileron and down elev near the end of the take off run to keep it on the ground a little longer! Other than that I really enjoyed it and am looking forward to exploring it's flight envelope and some odd looking sloooooow passes!

Chris Barlow14/02/2015 18:22:38
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1791 forum posts
1211 photos

Took the Atom out for a "spin" in the wind this afternoon. No problems in a 10mph (approx) breeze with some really slow fly bys. Very similar to flying without the wind except the take off run is easier.

Looking forward to the other Atom builds maidens now! You're gonna love it.yes

Chris Barlow15/02/2015 19:25:29
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1791 forum posts
1211 photos

Only a few hours spent on the Mossie last week and from what's been done you wouldn't think it was a few hours work either!

With the exhaust baffles fitted I went all over the airframe filling any dents and imperfections I could see with cellulose putty or filler primer. Although it's only a fun fighter there are a couple of details I wanted to add.

Wing panels and joint lines were created by masking off the panel and spraying 2 coats of primer. When the tape is removed it forms a raised line for the edge of the panel. Subsequent coats of paint dull the edge to a slightly raised "lip"

I also added raised frames for the access door and top hatch. This was done by marking and cutting 2 masks in 2 layers of tape and applying to the airframe. The gap forming the frame was then filled with a thin layer of filler, in this case chemical metal, and when set the mask removed. The frames were then lightly sanded down to soften the edges.

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Finally after what felt like hours of filling and sanding the whole airframe was cleaned, blown off and wiped down with a tack cloth before receiving a final primer coat with my trusty old Badger single action airbrush.

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Now it's ready to start "colouring in" laugh

Paul Marsh15/02/2015 19:32:13
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3582 forum posts
997 photos

looking good, Chris. Popping down now - need to get some milk from Co-op and see those colors.

john stones 115/02/2015 19:34:57
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10275 forum posts
1475 photos

Looks good from here Chris I like your curtainyes

John

Martyn K16/02/2015 16:58:34
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4811 forum posts
3498 photos

That's great = a DIY spray booth. Must try something similar

What primer do you use? It doesn't look grey in the airbrush

M

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