Sunday, 16 March 2014

Synapse wing motorised

The original Experimental Airlines design for the Synapse flying wing included motor and battery housed in a pod. So far I had only used the wing as an unpowered light weight slope soarer.

Ed uses Dollar Tree Foamboard which is very cheap and light but not available in Aus. Here we can use tape covered depron in the same way for scratch built foamies.

My pure slope soaring Synapse (featured in the banner above) was quite light and very easy to lose in the turns. It often ended up at the back of the dunes. I really should have ballasted it up more, but it did introduce me to the thrill of sloping.

I thought it was time to try adding a motor and see how it flew under power.

I made up a simple square tubular fuselage and added an EPP nose cone with an attached tongue to hold the battery.

First I tried a tiny 24g Hextronic 1500kV motor with 8 x 4 prop and it worked perfectly. With a flying weight of 550g using a 500mAh 3S battery I could fly quite slow and smooth.

That was fine until one of the three motor
wires broke right in close to the windings, no hope of repair. Both of my 24g motors have died that way, the wires are not well enough supported as supplied.

Next smallest motor in my box of gear was a Turnigy 2826/6 2200kV with a 6 x 4 prop. I didn't like the combo to begin with, very loud and buzzy, but after a simple prop balance it worked like a dream.

This design is great fun to fly and virtually indestructible.

I can still fly slow and smooth with low throttle and also crank up the revs for more speed.
Flying weight is up to around 650g with the heavier motor and bigger 1300mAh battery.

One unexpected consequence of the extra weight is that the slope soaring performance is much better. It turns with momentum and soars very smoothly along the dune.

Launching a pusher prop plane looks dangerous but in this photo sequence you can see my hand is well clear of the prop as it passes. Just have to remember to follow through in the throw.

Wednesday, 12 March 2014

Ultralight 450g Le Fish

While learning to fly my 660g (23oz) Le Fish I crashed often and hard. This prompted me to look for a spare fuselage and wing. Although EPP is very tough and repairable I felt that eventually a new fuselage would be needed. Actually the green Le Fish is still flying perfectly and probably will for years to come.

Flying Foam sells a short kit (just the wings and fuselage) for US$65 plus US$50 freight to Australia. 2 kits will fit into the box for the same postage, so I bought two.

I decided to use one of the kits to build an ultralight as light as possible. It came out at 450g (16oz) with a 500mAh 2S battery and CG balanced, which is fantastic.

The flying experience is remarkable, quite different to the heavier version. It recovers from loops or stalls so easily, seems like it's on an elastic band hooked to the sky. My slope is not very steep so I still have to stay out in front but I can perform more tricks with this sloper and in a wider wind range.

The build was mostly the same as the green Le Fish but with less spars, lighter hardware and servos, lighter rudder and elevator servo forward in the hatch. The wing tips and tail boom feel quite flexy, they're fine in the air but a bit delicate for handling on the ground.

Will they be tough enough? Time will tell. As this Le Fish is much lighter and mainly flown in light winds the landings and crashes are gentler.

First off I gorilla glued the wings together using a 1m long 1mm x 6mm CF ribbon spar. That leaves the outer 25cm of the wings unsparred and quite flexy. There is no trailing edge spar at all.

The wing is covered all over with 1.7mil laminate and another 3mil layer on the D-Box. I decided to try oversized 60mm ailerons hinged with 3mil laminate and they seem to be working really well. I made lightweight control horns from plastic ID card and gorilla glued them in place with another rectangle of ID card for reinforcement.

The Flying Foam fuselage is thinner than the Leading Edge Glider kit and I sanded it down quite a bit further. Interestingly there is a thick half and a thin half. This means you can site all the gear in the thick half.

The rudder and elevator servos are accessible through the hatch and use Gold-n-rod #503 push rods. Aileron servos are just forward of the wing as usual. I used Turnigy 9018MG micros all round and they're working well.

Fuse is covered with 3mil forward of the wing and 1.7mil aft and there is no longeron.

Horizontal stabiliser is conventional, not full flying or mad, and the rudder is as light as possible made from raw uncovered depron. I wasn't tempted to cut swiss holes anywhere, they look good but reduce strength for not much weight saving.

Here's the maiden flight of this amazing ultralight aerobatic slope soarer.