A narrow escape from hell.

[Jurgen]

Tuomo seduced me to launch with extremely high line tension. I managed to do so and the launches became hotter al the time. There was plenty headwind, the wings bent alot at the top and I got the feel something special with that amount of power was about to reveal itself soon. This was going to be an awesome high launch, my wet dreams ready to manifest in a super mega slingshot zoom to the stars. I do the dip, pull out and WHACK!! I see some part coming of, a piece of elevator swirl downwind never to be found again. Must be terroristic sabotage, why me, etc. The plane flies difficult but still it flies. Then terror strikes once again, nose perfectly down ready to mess up Satan’s gardens. Suddenly, in must have deserved this, some cosmic forces (god I love those) gave me back some sort of elevator authority and I manage to “fly” for another 3 minutes and land very gentle and soft on the runway. I check the elevator function, the servo gear was stripped!!!

First and second conclusion: I’m a dumbo doing a tailcatch, ripping off the elevator.

I look at the elevator debris and the Sherlock Holmes inside of me start poking my brains. Hmm, this is not a clear cut like the other tailcatch I had once before, this is a blow-up, a genuine disintegration, broken where the tube goes over in a balsa spar. Also the dip was small and the pullout not excessive. Maybe I’m not the foul doing a stupid tailcatch after all?

The inner Sherlock start to convince me when I realise the flight before had 2 times a very suspected split second elevator spasm never seen before, I thought about interference but that would have been intercepted by the special IPD receiver. The later control surface check was OK but that’s without load right? Jeez the gear was already sick before the start of the terror flight! The servo gear was sneakily waiting for the next dip-pullout to go bananas. Its quite understandable when the plane rockets at top speed for the tender elevator to explode by overload when its loose.

The brand new Futaba 9650 had only 20 flights at service and was chosen for its high speed, yet the nylon gear was not up to this task. Next will be metal again, probably a Volz. Other experiences with nylons on elevators doing hard winch launches?

Jurgen. (who is so lucky to go trough a miraculous save)

[LVsoaring]

Tuomo is from Finland, isn't he? Gotta watch those Finns! They will talk you into doing things you shouldn't, like drinking so much Koff beer you can hardly remember your name! (LOL, personal experience) I'm glad to see you got your plane down intact, and it will live to fly another day.

Rick

[Jurgen]

Thx Rick !

Yes there is something special with those Finns going on when it concernes drinking, they developed a language so you cannot hear when they get drunk :)

I have proof (see attachment) that these guys have something special when it comes to alcohol. I got these from a Fin when i was a junkielike-on-line-warbird-pilot flying Combat flight simulator, European Air War, Aces High, and others in a sort of previous life. If you wanna make it yourself you must try to get the particular Tyrkist sweets. I got them back then from the fellow teammate Fin, and the resulting oil-like black liquide is dangerous appetising and adicting :D . you get drunk before you know it.

Attachments: the recipe and apropriate label for the bottle.

[Jurgen]

The taste ingredient :)
I hope i did not reveal any official Finland state sercet here.

[David Smith]

I think you'll find this works just as well if you leave the sweets in the pack and just drink the Koskenkorva :)

An Englishman who has spent the last 10 years in Finland (most of them flying models!)

[Tuomo]

Jurgen, in your first mail you refer to Sherlok Holmes. How come? I Belgium you have Hercule Poirot and EU-bureacracy. Put together they should have enough genius to analyze how your incidence happened :D

But lets look at bright side: you have got tension in the line -- and your plane is (almost) in piece. Next time you avoid tail catch, after thet you get more speed etc. Buy a new elevator half and some thinner line (1.05mm and 1.15mm) to help you learn more. Personally, I try to concentrate on my landings...

BTW Tyrkisk Peber sounds like very very Swedish thing. A very good idea to take something Extra, but there is not a word of Finnish langugae on that packet...

[mlachow]

Looks like the stab failed. The load on the stab is downward when pulling into the zoom. Since it failed just beyond the joiner rod, it probably buckled just beyond the joiner rod on the bottom, then the rest of it blew off due to the speed of the zoom once the bottom skin failed.

Fortunatly most models fly just fine with only 1/2 the stab. You had a little extra.

[Tuomo]

Looks like the stab failed....

...but perhaps it all started when elevator servo gears let go. Jurgen, nothing against Volz, but the best of them are on the expensive side. I have had good experience with Grp DS 3728. It is very accurate and strong so you can use a long servo get little more speed. "Only" about 75e.

[Jurgen]

Buy a new elevator half and some thinner line (1.05mm and 1.15mm) to help you learn more...Tuomo, can you discribe how the thinner line would benefit? Is it hight and/or learning advantage? I'm afraid to beak thinner line.

My major concern is now, if i replace the elevator, will it be strong enuf in the future??? This one broke maybe not by tailcatch but by overload. Its all maybe and perhaps, not sure. I might ask manufacturer to add some carbon rooving.

THANKS for the graupner servo tip, i'll check on that one.

Jurgen.

[Sparky Paul]

That really does resemble an excessive down-load failure, with the lower skin buckling right at the end of the joiner, and the top skin just tearing off.
Extending that some distance out will beef up the next tail.

[Jurgen]

Just alitle carbon strip on top and bottom connecting the tube with the balsaspar was enuf to avoid this from happening i presume.

[Tuomo]

Tuomo, can you discribe how the thinner line would benefit? Is it hight and/or learning advantage? I'm afraid to beak thinner line.

Less aerodynamic drag. Thinner line also streches more easily -> you can get some sort of zoom even with moderte tension. Bigh help in calm weather, tailwind, when launching to sink etc.

Thinner line also adds less to the diameter of winch drum -> you have more pulling power in the critical moment just before release.

I am sure you will be ok with 1.15mm or 1.2mm in most conditions. Save the 1.25 to really windy weather.

My major concern is now, if i replace the elevator, will it be strong enuf in the future??? This one broke maybe not by tailcatch but by overload. Its all maybe and perhaps, not sure. I might ask manufacturer to add some carbon rooving.


Corado 2 is quite a proven design? Servo gear failure took the plane out of its normal flight envelope.

[mlachow]

It would take a close look at the parts to see which way it failed. If the bottom failed in compression, then it was probably a structural failure. If the top failed in compression, then it was the servo gears failing first.

Curious that it is one side only. If the servo failed and things pitched violently, usually both sides will fail the same way. Unless there was some sort of minor defect or some piece missing in construction.

[Robglover]

Sounds like you are getting the launch just right when stuff starts breaking. Now you just need some stronger stuff.

happy trails

[Jurgen]

mlachow, it does look like underside had compression and topside tearing, i think we have it nailed here. I keep hoping it was the broken gear creating the overload so the elevator is strong enuf in normal "hard" usage.

Robglover, i regret this way of sorting out things :D. On the other side i learned alot of RCgroups by painfull gained experiences from others. Lets keep them shared.

Tuomo, i am willing to use thinner line but then i start swimming in opposite direction of JoGrini who uses 1.35 and others even 1.45mm. Its confusing abit.

Jurgen.

[Tuomo]

Tuomo, i am willing to use thinner line but then i start swimming in opposite direction of JoGrini who uses 1.35 and others even 1.45mm. Its confusing abit.


I think that must have been with Pike Perfect. It is known to pull hard.

Anyway snapping a line is not that bad. You have seen much worse incidents ;)

PS1 Corado2/Zenith has been around for so many years, that I find it difficult to believe that the is anything fundamentaly wrong with its construction. My scenario: servo failure happened while you were pulling hard up, letting elevator slam freely to full up position.

PS2 How much does one elevator half weight? 25g?

[Jurgen]

Yep, how could you know that so sure :) , exactly 25 grams it is !

[Barnsey]

Anyway snapping a line is not that bad.Unless the opposition flies out the slot... :D

Jurgen, I had new 0.95mm conditioned Speedline snap twice at this years Nats when winch launching a 100" r/e ship into a modest breeze (6-7m/s). 1.15-1.25 used by others (100" class) wasn't breaking.

Thanks for the details of your elevator failure. Maybe nylon servo gears soaked in Chouffe would be tougher... :D

John

[Jurgen]

Thx John, maybe i better soak myself in the chouffe :)
For the uninitiated: What is Chouffe ? (http://www.achouffe.be/newen/produits.php)
Chouffe is a kind of sponsor for many of the Belgian soaring teams, after the flights Chouffe is on order of business :), sometimes in the form of an award to win. If i am not misinfomed, the founder of Chouffe is a glider pilot himself, hence the sympathy.

6-7 m/s, thats 4 beauford, that starts to be some wind with balls isn't it? Good reference to hear thats just over the limit for 100" birds on a 0.95mm.

When i bought my winch second hand it came (among other things) with a 0.85mm spool. I asked the F3B guy if one can realy take a F3B ship up with it. He said yes on low or no headwind conditions. I never deared to try it on the much bigger 138" Corado.

Jurgen.

[Barnsey]

Chouffe is a kind of sponsor for many of the Belgian soaring teams, after the flights Chouffe is on order of business :), sometimes in the form of an award to win. If i am not misinfomed, the founder of Chouffe is a glider pilot himself, hence the sympathy.You are not misinformed. Mr Chouffe, Christian Bauweraerts, has been very supportively involved in r/c soaring for a long time. Last year he sent me the attached picture and accompanying historical notes. Note the FAI stickers on the BOT tail feathers, which might mean that this was the model flown at Amay in '79 :cool:.

Hello,

this picture has nothing to see with the business, but with my hobby.

Thanks to "Glenn BURNETT" & his father Ed, I can present you a picture of the designer of my favourite glider, the "Bird of Time", Mr. Dave THORNBURG, with the Bird of Time in his hands.
The guy with the bottle of CHOUFFE is Mr. Steve WORK. I'm very proud of this picture !
Dave THORNBURG and Steve WORK (as young pilot, flying Bird of Time) where present at the World Championship 1979 in Amay in Belgium.
I was present there to operate the computersystem who compiled the results and the classing of each pilot ==> at that time there where no PC available!

Cheers, Chris B.

The 3x35 T shirts are promoting Chris's electric duration/precision landing fun-fly events where, I am told, Chouffe was sometimes available 'on tap' to help things run smoothly. Perhaps it still is :D.

Wind speed obviously a major factor in line sizing. At last years Nats I was launching a 134" span r/e/s Open ship (Eliminator 134) on conditioned 0.95 in flat calm conditions. My ships are built-up so I tend stay on the line longer than moulded ships (a hard habit to break :)), which puts more strain on the line when breezy than releasing earlier. The winner of our Nats Open event this year also flies F3J. I stood beside him to watch his fly-off winch launches. A gentle breeze. Like F3J, he used the winch to high-tension the line before his helper threw the model. 4-5s and off the line, no diving before release. The model setup retained/increased the line tension before release, the winch almost a bystander.

John

[rdwoebke]

This Chouffe sounds very good. I am neither a good sailplane launcher nor a person that lives in an area where people are likely to enjoy Chouffe, but some day I hope to do both (although perhaps not at the same time)!

Ryan

[Jurgen]

John, nice to see a picture of the legendary D.T.

Ryan, Belgium is famous for its beer but its not in particular a soaring paradise. Neither the weather, the regulations & available space is forthcoming. The belgian team is surprised when they can fly out as far as they like in each direction on international contests. We are handicaped, hence we drink beer. I dream of having a house with enuf backyard to winch and the weather is good most time of the year. I dream on...

For the next 14 days i'm on holiday, dunno if the hotel has PC's/internet. No plane along, my wife wil be sufficient (she says) :)

Jurgen.

[Robglover]

Jurgen -

We have a lot of places to fly here in Alabama, but the beer selection is not good. I like to fly and drink beer (not at the same time). Guess that I will have to visit Belgium and find some good beer. If you ever come to Alabama look me up and we'll go fly.

Enjoy your holiday and listen to your wife. Wives are always right.

happy trails - Rob

[bobby legue]

AMEN Rob, amen.
Bob

[POF]

BTW Tyrkisk Peber sounds like very very Swedish thing. A very good idea to take something Extra, but there is not a word of Finnish langugae on that packet...

"Tyrkisk peber" is actually Danish. A bit like chili but not as strong as a good chili.

[Jurgen]

To return to the subject:
surfing around the www I cropped this picture out of a Japanese Internet site ( a 2004 upload). Look at the google translation, this is hilarious :D
BTW, got a new set of elevators with a extra roving reinforcement at the expense of 1 gram each side, no big deal. But crashed the corado last week due to another cause (me!), might be repairable, we'll see.

[kakao]

Just alitle carbon strip on top and bottom connecting the tube with the balsaspar was enuf to avoid this from happening i presume.

Wow - i have a wing on my glider that is created by this technique and in cracks ( :censored: ) i can see the same structure - can you name the techinque it was produced?

Do you know how to repair it ??

[Jurgen]

I did not repair it but bought a new elevator set. This time the carbon strip was added to my suggestion at expense of 1 gram/elevator, but finally the strip went bigger from root till 3/4 of elevator width.

Repairing such a break would difficult and heavy, but if you want you might add an external layer of epoxyed fabric on top and bottom of the broken zone (possibly with carbon reinforcement). Note that usually there should be a connection bound between top and bottom recondition.
Jurgen.