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.


  1. Hi Andrew, just want to chime in here and say you've done a great job on both your Le Fish builds. I hope each of them bring you years of aerobatic enjoyment!

    That dune flying site in your latest vid looks really cool - check out "Drawings in the Sand" on Youtube if you haven't already, it's a classic Le-Fish-in-the-dunes video.

    Best regards from Santa Barbara,
    Steve Lange

  2. Thanks Steve, your approval means a lot. Black Hills Reprise video on YouTube planted the seed about 3 months ago. I'm way down the learning curve for aerobatics but loving the challenge.

    Hanging out for NW winds so I can fly on some steeper sites. Gotta pull off one of those French M moves.

    Thanks for this brilliant design and the inspiration.