Robotbirds Hyperion Su31 10e

[Martin Harris - Moderator]

A clubmate, John, bought one of these models from Robotbirds at Wings and Wheels and it looked nicely finished and of decent quality.

 

He assembled it with the power train supplied by Robotbirds and brought it up to the club for its maiden which he asked me to do. After a quick once over of the assembled model to check the linkages, hinges, control movements etc. I took off and flew a few trimming circuits and checked out the low speed handling which was fine.

 

As it was advertised as an aerobatic model the next move was to try a loop - whereupon a loud crack was followed by the starboard wing falling off - unfortunately I was unable to attempt to emulate the famous knife edge save which was widely circulated as the port wing was dangling by the rubber band retainer...even if it had occurred to me in time!

 

Unfortunately, although both wings were undamaged, the fuselage, cowling and canopy were terminally re-arranged, the motor was damaged and the brand new LiPo was a crumpled mess.

 

On examination, the failure was quickly traced to the wing joiner - a piece of 1/8 liteply which had broken cleanly in a straight line at the fuselage to wing join. Having experienced more than reasonable customer service from Horizon Hobbies, Ripmax and Hobby Lobby when manufacturing or design failures had occurred, I suggested that John call them to advise the failure and request some replacement parts.

 

I was very surprised to hear that the reply was that as 150 odd of these models had been sold with no complaints they wouldn't entertain any claim. It seems to me that this would indicate a faulty joiner - although I would have selected birch ply myself - unless (and this brings me to the point of this posting) others have experienced the same failure?

 

The incident was witnessed by our Area Chief Examiner and some fairly experience builders/flyers and we all felt that the manoeuvre was well within the assumed capabilities of what was advertised as an aerobatic model, using the recommended power train and control movements.

 

I followed up John's call with 3 emails on his behalf - as even though general agreement was that the joiner shouldn't have failed due to my flying I still felt some responsibility as the pilot - all of which have remained unanswered.

 

Has anyone had any experience with this (or similar) Hyperion model or of Robotbirds' after sales service?

Edited By Martin Harris on 12/08/2011 19:40:46

[Wingman]

I own a Hyperion YAK55 10e, fitted with the Hyperion power train, which I've tossed about the sky with gay abandon (read panic!) quite a few times and have even managed to throw off the canopy due to high G gyrations all without damaging the wing joiner (same as). However I don't use the lacky band, I use a plastic tywrap between the two 'cup hooks' so there's no possibility of the wings moving. I guess your friend didn't have the lacky band tight enough and the wing got pushed out of the socket far enough for the incidence peg to disconnect allowing the wing to move rearwards and snap the joiner.

It is very lightly built so any movement of the wings is liable to cause trouble.

Edited By Wingman on 12/08/2011 20:05:05

[Martin Harris - Moderator]

It's certainly a thought Wingman but the joiner failure didn't appear to be typical of a bending failure - backed up by a quick experiment a couple of minutes ago with some liteply where a bend failure against an edge created a jagged fracture but a swift blow with a hammer in the direction of the wing loading to a piece in my vice produced a clean and straight failure very similar to my clubmate's.

 

We certainly wondered about the use of bands but reasoned that the flight loads shouldn't have put much tension on them - although John's immediate reaction as the wing came off was to shout that the (word not allowed on this forum) band has broken - flick rolling might be different of course!

Edited By Martin Harris on 12/08/2011 21:28:28

[Martin Harris - Moderator]

Looking around some other forums it seems that joiner failure on the 10e models is mentioned extensively and I've found references to Hyperion supplying a "glassed spar" on "later" versions. Has anyone come across one of these and if so, does this mean John was supplied with a very old version?

 

I've also seen references to sanding the joiner to bond some CF sheet so far from being a one off problem as inferred by Robotbirds, it does appear to be a perceived design weakness.

 

If Robotbirds knew that there was a possible problem and were perhaps selling off old stock at the show, I would have hoped they would have advised strengthening the joiner - a relatively simple exercise which would have avoided this grief...

Edited By Martin Harris on 13/08/2011 11:21:30