Tuesday 14 October 2014

2m Parkzone Radian EP mods

Everyone has heard about the 2m Radian. It's a very simple no-aileron motor glider with graceful curved up wings and has fantastic thermalling abilities.

For A$200 the "Plug and Play" version comes with a good quality motor and servos fitted and not a lot of assembly required. Add your own receiver, battery and transmitter.

I bought mine from RCWorld in Geelong. They have all the spares too.

Like all planes there are a few issues to be sorted out before flying. It is very light and flexy, especially in the tail area, and some of the fittings are inadequate. Most owners carry out strengthening mods and Paul Naton, well known glider tutorial DVD producer, has published a mod video which is essential viewing.
Paul Naton's Radian mod video

Essential mods needed before the first flight

Pathetic plastic clevis connectors
The pin on mine broke just trying to clip on to the control horn the very first time! What were Parkzone thinking? These ridiculously weak plastic clevis connectors are just wrong. May be OK for a tiny indoor foamie but not a 2m thermal glider.

I couldn't find another connector to fit the pushrod thread so decided to beef up the existing one with a piano wire pin. Just needed to carefully drill holes in the cheeks using a piece of the wire as a drill bit. Tight fitting shrink wrap (not shrunk) keeps the pin in place and connector cheeks pulled in.

Staples into foam?
What is the purpose of these staples? They were straddling the pushrods where some sort of fixing structure should have been. I pulled them out, they were already floating loose, and threw them away because they offended me!

My solution was to use tough clear gaffer tape to fix the pushrods securely to the fuselage leading into the rudder and elevator.

Missing canopy magnet
The canopy is held in place by magnets front and rear. Unfortunately one of the fuselage magnets was missing. Luckily I had a replacement in my spares box and I glued it in with gorilla glue.

Changed ESC connector
The Parkzone ESC comes with an unfamiliar (to me) blue connector, to match Parkzone batteries I guess. All my LiPos have XT60 connectors so a little soldering was required to swap the ESC to XT60.

Receiver bay surgery
The receiver bay is made for a small Spektrum Rx but all I had was a bulky 8ch Turnigy Rx. All I had to do was cut out a little mound of foam to make it fit. 

After those easy repairs/mods it was airworthy and ready for the maiden flight. The day was windier than ideal but the Radian performed superbly. No thermalling on the first day but on subsequent days I climbed to frightening heights, lots to learn. 

I had previously checked the range of my Turnigy 9X transmitter with a 6ch Hobby King receiver. I got more than 800m at low altitude flying along coastal dunes. The highest I have had the Radian is 300m, and I wouldn't want to go too much higher at this stage, so it would have no problems with signal strength. At 800m the glider would not be visible anyway.

Optional performance mods - (inspired by Paul Naton)

Elevator control horn placement
The control horn was relocated inwards about 12mm to give the pushrod a straighter run. The control horn base was shaved off where it now overhangs the elevator. Elevator was stiffened along it's span using 12k carbon tow and epoxy.

Elevator hinge was taped both sides with clear packing tape for durability. Moulded foam hinges will fail eventually, they are not designed to last. Fixed the horizontal stab in its slot with clear gaffer tape both sides, above and below.

Fuselage stiffening
Added 3 strands of 12k carbon tow along the bottom of the fuselage boom to reduce tail flex. I covered that with clear packing tape for smoothness.

Wing slot top strengthening
I added 3 strands of 12k carbon tow over the top of the wing slot because this area is quite thin and prone to failure.

Wing leading edge tape
After a few flights I noticed that the leading edge was becoming dented and scratched so I added clear packing tape back to 50mm from the LE top and bottom

Wing retaining velcro / magnets
There are many horror stories on the forums about wings falling out in flight. They are very weakly held in with friction and slightly keyed foam blocks that do nothing at all.
Initially I used sticky back velcro on all the meeting surfaces of the two wing halves but that pushed the wings apart by almost 1cm. My current solution is magnets glued to 40mm dowel inserts. These are quite securely glued into the wing roots with epoxy also strengthening that area nicely.

Rudder root strengthening
To stiffen the area at the base of the rudder I cut a slot and glued in a 6x1mm carbon strip pushing it right down into the foam of the fuselage.

Decalage mod
All of these stiffening mods add a little tail weight moving the CG rearward. This is actually a good thing according to the experts. The stock CG of 70mm is too far forward requiring up elevator to fly level. The Radian is designed with lots of horizontal stabiliser decalage angle as seen below and performance can be improved by moving the CG back and reducing the decalage angle. Well that's the much-debated theory anyway.


I tried the decalage mod by slicing out the foam wedge (marked below) and repositioning the horizontal stab. At this early stage of my thermal gliding journey it felt like too much and I couldn't get it to fly smoothly. So I have gone halfway back. Seems like a good compromise now with my CG at 78mm or 3".

Painted bottom surface of the wing
For visibility and orientation. This glider starts to be difficult to see higher than 300m. Solid black seems to be the most visible colour at that distance.

Radian videos

Trying different camera mounting spots

Thermal flight in Google Earth, recorded with a GPS watch

Slope Soaring

and finally Stormy loves the box so all is good.

UPDATE: I left customer feedback on the Horizon Hobby site about the broken clevis connector and missing magnet and they sent me replacement pushrods and canopy, posted in two separate parcels from US to Australia. Now that is awesome customer service.  

Monday 13 October 2014

Red Sloper with added dihedral

Here's a demo video covering how I add dihedral to a depron Armin wing.
I show how to bend a 200mm length of ali tube to set the dihedral angle and hold the spars.

This video also shows my swappable motor mount for the Red Sloper and other construction tips.

Here's a slope soaring video showing how the dihedral makes the Red Sloper into a smooth and relaxing glider while slightly reducing the aerobatic capability.