Radio Control Jet International - April-May 2018

to use laser 3D prints where the details are

too thin to be CNC machined and cut alumi-

num where strength matters. In practice, the

sleek machined struts are covered with SLA

50 micron 3D printed resin covers. The covers

contribute to reducing the gear weight and are

interchangeable in case of damage. This

gives very impressive lightweight and visually

intricated results. The non 3D printed parts

are in-house CNC cut on our Siemens machi-

ne centers from shock resistant Alcoa Al 2044

and Al 7075.

Some details like the main gear strut joiner

are quite intricate and require many machine

hours to achieve the perfect shape with the

proper angles.

The one part I was not sure about was how to

actuate the main struts. The real plane is

using a brace rear brace actuator that is

hydraulically operated. This at 1.7 scale was

way too thin to be efficient when powered by

a pneumatic system. So different options

the tailpipe. The protruding segment is not

that long, however, and I had to use a pair of

super stiff 12 mm wide needle bearings enca-

sed in a Al 7075 solid block. The control arm

is located between these two bearings for

maximum stiffness and is pressure clamped

as well as being keyed on the shaft for maxi-

mum safety. The pushrod is made of a pair of

stainless steel 3 mm precision ball links and

our aero certified 3 mm stainless threaded

rod. The assembly is exceptionally stiff, preci-

se and strong. This prove to be very welcome

in this plane and gives ultimate precision and

super high authority to the pitch axis.

As the plugs and moulds were in the process

of being finalized, I started working on the lan-

ding gear CAD. I started from the prototype

landing gear that the Texan group had made.

However I wanted my gear to be 100% scale.

So I worked from the pictures Woody made

for me and the hundreds of measurements he

took from the real plane. All the tiny details of

the struts, wheel rims, hubs and braces were

reproduced on the CAD. Some of the details

were too thin and intricate to be CNC machi-

ned, especially on the nose gear. So I opted

to work with the technique I had implemented

on our SR-71: a hybrid build from 3D printed

and CNC machined parts. The idea here was

A top view of the plane with the wing tips removed. It is easy to transport in a SUV in this configuration and

allows for a very fast setup at the field. Not that the wing tubes are now made from carbon fibre to save weight.

Once removed, the canopy/ cockpit assembly open up a large area. The batteries may

be placed into the removable nose. GPS/ pitot sensors can be added behind them.

A CAD rendering of the ultra scale 3D printed cockpit.

A view of the plug with its skin waves, rivets and added panels.

Note the slats moulded in the takeoff position.

F-8E CRUSADER

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