Disaster! My own stupid fault.

[Nigel R]

 

4 minutes ago, Engine Doctor said:

Think what could happen if that lovely big engine came loose while prop hanging a few feet in front of the pilot .

 

or, if the other wing had failed, and he hadn't caught it quite as quick.

 

 

[extra slim]

1 hour ago, Engine Doctor said:

These models are very expensive now and imo the build quality is rubbish . Ive repaired quite a few for various flyers now and all have one thing in common , lack of or inappropriate glue , and rubbish quality plywood in high stress areas! The video clearly shows how the ribs just slip out of the spar . This is a common finding during repairs and the models rigidity relies mainly on the interlocking very cleverly designed parts. But , as soon as one part fails all the rest collapse like domios.

 

The last repair was for the uc mountings on a turbine powered model. The mounting plates had virtually no glue securing them to the ribs that they slotted through and the ribs were made of carbon fiber coated ply ( sounds very strong and sophisticated )that was absolute rubbish  infact more like laminated balsa that compressed very easily allowing the plate to twist eventually tearing out. The glue used in manufacture was like a brittle heat gun glue that had obviously been applied after assembly with no chance of penetrating the joints and could just be flicked off with scalpel ! Nowhere did i find any glue that actually adhered to any of the carbon .

The next repair Ive been asked to do is to the engine mount and fuselage front and cowling caused by a wheel finding a bump or small hole in the ground while taxying and the model nosing over . The  whole engine mount collapsed with a lot of collateral damage to surrounding fuz.

Its a bit like buying a car thats all shiny and smart only to find out that its a few cars  badly welded together! 

 

So check rigidity and aiframe structure regularly . Apply a dtop of adhesive into joints that will penetrate and lock the joints while assembling the model. Covered wings obviously cant be checked . Think what could happen if that lovely big engine came loose while prop hanging a few feet in front of the pilot .

 

Cant agree more. I love all the chat in the pitts with the hotshots and models of this size, going on about, high torque this, powerbox that, S-Bus the other... when you take a look at the quality and design of construction and materials, quality of horns, hinges etc.. masked by a fancy colour scheme to make us all drool, it doesnt matter a jot, what gear you stick in it. IMO, more diligence needs to be applied to the airframe, strength, construction etc to eliminate an expensive mishap. (and no, that doesnt mean extra weight!). Sadly most people seem to be more interested in the quality of the paint job on the pilot!!.. barmy

[Engine Doctor]

Yes all about the " latest must have fashion" . Provided its covered in a fany "Profilm"  design it must be good quality ? Or is it ?

[Jon H]

I cant disagree, but my only defence of the model manufacturer is that the loads imposed during that sort of pull up are extreme and I wouldnt be flying the model like that. I would also be interested to know if the model was over powered and thus over speed, was it well maintained, what previous adventures had it had?

 

Many moons ago my dad had a rather rough landing with his flair pup and upon inspection all seemed well beyond a broken wing strut. Fast forward a few months of flying and the wings on the left side of the model folded up. Clearly the damage went undetected and caused the failure later on. 

 

AS pointed out though, the consequences could been severed were the deck stacked a little different;y. 

 

 

[Nigel R]

3d models lead a hard life in the hands of some pilots.

 

I think the model probably would have been fine if, as ED points out, the things were actually glued to the other things. Instead of all coming apart once one thing had come unlocked from another thing. 

[Engine Doctor]

7 hours ago, Jon - Laser Engines said:

I cant disagree, but my only defence of the model manufacturer is that the loads imposed during that sort of pull up are extreme and I wouldnt be flying the model like that. I would also be interested to know if the model was over powered and thus over speed, was it well maintained, what previous adventures had it 

 

 

Hi Jon. I dont fly like that either because i cant 🙃. I do prefer the scale type flying manouvers .The hotdogging flyers are very tallented and quick on the sticks but prop hanging leaves me cold; however the full size Extra can do the manouvre that broke the model . I have witnessed it as did thousands of others at the Paddock Wood show organised by Croydon MFC some years ago. So  the model should easily cope if built correctly . Air frame failure must lie solely with builder and and in this instance the lack of adhesive and appropriate adhesive for the carbon spars.

[john stones 1 - Moderator]

That type of model gets that type of stick day in and day out, failures such as that are seldom seen, bit of overkill on this thread. 😉

[Jon H]

4 minutes ago, john stones 1 - Moderator said:

That type of model gets that type of stick day in and day out, failures such as that are seldom seen, bit of overkill on this thread. 😉

 

I dont think that is totally true. Most true 3d is flown at fairly low speed, always has been. In those cases a sharp pull up will not impose large loads on the airframe. In this case the model was at high speed and the resultant failure was hardly a surprise. 

 

And to take a leaf from the full size aviation book, it is far better to avoid a failure than handle one well. As models get bigger and bigger structural failure becomes more and more likely. Take a look on youtube at model crash videos. Many large models go down to flutter or other structural problems. Admittedly many of these may be down to suboptimal design and construction of ready built models, but if that is so then they need to be reported and not just shrugged off as just another crash. 

[john stones 1 - Moderator]

More whataboutery, thousands upon thousands of flights done, of course there's some failures on you tube, the walls been flown for umpteen years, many times with a lick on. True 3D ?

[Philip Lewis 3]

I'm with Jon on this one, that model was flown in from height and distance at full throttle and then violently pulled up up at 45 degrees instantly, like he had inadvertently left the rates at the 3D setting by mistake, I can't see any traditionally built airframe taking that much abuse, it's snapped where the structure becomes a pure wooden construction so maybe the full size has reinforcement along the whole wingspan.

 

OK it's a 3D model but that doesn't mean it can take that much aggression.   

[john stones 1 - Moderator]

A muppet like myself has done many, Irvine Wild Card, Mini Hype, never a breakage yet, a model failed there's the story.

[Nigel R]

Yup , wall is a regular 3d maneuver, no point getting cross about it being flown.

Flying it where the bits might exit toward the flight line, maybe less clever.

 

Model should take it though.