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Mark P

Pressed Foam Wings

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Gromit
1 hour ago, wookman said:

Still following, still impressed. 

X 2

  Stu

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Mark P

Starting my favourite part of the build - putting the radio gear in.

3mm play tray with 6mm square rails to increase the gluing area and beef up the nose.

Elevator servo is offset to allow pushrod to run down the centre of the fuselage. 

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Mark P

Elevator pushrod installed so the rudder post has been fitted. Proper hitech solution with the clothes pegs.

Pushrod is 4mm carbon tube from Hyperflight with a M2 threaded coupler roughed up and glued inside. I always heatshrink the  end of carbon rods as they can split.

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timboiow

Great job Mark , and nice to see a build and to see how people approach certain parts of the process. It gives ideas others can (shamelessly) nab and incorporate into their own creations. Well done, and keep up the good work, looking forward to the finished beast.

 

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Mark P

Glassing the tail feathers

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Mark P

Cutting out the ailerons. 

The front of the ailerons and the back of the wings are faced with 0.8mm birch ply to maintain  torsional rigidity.

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Mark P

So now I am on to installing the servos in the wings. I like to make a template for the cut out to make I do both wings the same (!).

If all goes well the servo wires should appear in the right place when the foam is required.

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Mark P

On to actually gluing the servos in. The foam cutouts are cut to be a snug fit for the servo mounts and the wells are cleaned out thoroughly.

A layer of glass cloth is put on the inside of the wing skin and the mount glued in with epoxy and micro balloons.

A smear of good old fashioned vaseline on the servos so that they can be removed if necessary but the horns are already fitted so that once the epoxy cures the job is done.

All done in one go so that the ply mounts, glass cloth and micro balloons help reinforce the top skins.

 

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stewartg

Probably teaching granny to suck eggs here but as an alternative  I would...

1) cut a smaller hole in the skin to weaken it less and round the corners to reduce stress points

2)use a tiny dremel router to cut out/remove foam from the hole, much neater

3) screw servos into frames, even though the frames are thin if you harden the hole threads with cyano  it works or use blind nuts.

       I hate breaking servos out of wings especially non moulded  ones

4)brace the servos in under the bottom skin for extra rigidity and security with a removable thin carbon strip

Not criticing just suggesting!

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Mark P
1 hour ago, stewartg said:

Probably teaching granny to suck eggs here but as an alternative  I would...

1) cut a smaller hole in the skin to weaken it less and round the corners to reduce stress points

2)use a tiny dremel router to cut out/remove foam from the hole, much neater

3) screw servos into frames, even though the frames are thin if you harden the hole threads with cyano  it works or use blind nuts.

       I hate breaking servos out of wings especially non moulded  ones

4)brace the servos in under the bottom skin for extra rigidity and security with a removable thin carbon strip

Not criticing just suggesting! 

Expert advice, excellent.

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Mark P

Picture courtesy of Graham Woods

sonic.jpg

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oipigface

But did it fly?...

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Graham Woods

Yes it did fly, and rather well as it happens. I arrived at the White Sheet's Open Slope's day at around 9:30 and saw this very nice plane doing some unusually good aerobatics on the slope as I unpacked the car. It didn't realise it was Mark with his Sonic Hedgehog until I saw the model after it landed. At 1.3 kg this is a lovely light wind model. Pity it's not still available, I should have one if it were. While the fuselage is typically French looking (to me) with a long canopy and short nose moment Mark's decision to use an HQ section with 1/32 balsa and double glass sandwich pressed wings made this a great aerobat.
gw


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