HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jul 22, 2004, 10:21 AM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
Strange end to a flight

Last night two of us made the 140 mile round trip to Church Fenton for a freeflight evening which was to include a Bowden type event. The weather was dry, overcast with a light wind and some obvious lift around.

As usual there were many f/f flyers and a good sprinkling of vintage models.

I took my 1938 vintage French design, the Kid, powered by an original Frog 100 diesel. During a trimming flight, at about 250ft and climbing steeply, the d/t line snapped and the tailplane came off.

Disaster, you might think, but the engine ran for a few more seconds then stopped. The model stopped looping and settled into a lazy, shallow glide - inverted - and as it started to roll upright it reversed and maintained the inverted flight. By this time everyone was pointing at this strange apparition in the sky - a steep 'V' dihedral pylon model gliding well and stable until it landed in the grass. No damage, and the tailplane did 1min 45 secs..

The CG was on the mainspar without the tailplane. It has a thick undercambered section - an Eiffel of some sort, I think.

Lucky!

here's a pic of the model and a general view.
Tony Oliver is offline Find More Posts by Tony Oliver
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 22, 2004, 02:18 PM
Guest
Santo, Tx.
Joined Aug 2003
134 Posts
Tonyo- I watched a polyhedral model do the exact same thing. Looped like mad 3 or 4 times, engine timed out at the same time the horiz. stab came off. Then it went inverted and setteled into a pretty nice glide, upside down. No damage, but it was considered an offical flight. Jim
BTW- Is that a Joost Bakker 'Bugaboo' in pic #1? If so, how does it fly? Jim
Blazer is offline Find More Posts by Blazer
Reply With Quote
Old Jul 22, 2004, 03:09 PM
Registered User
Ian Easton's Avatar
United Kingdom, Scotland, Fife
Joined May 1999
2,849 Posts
I don't knowwhat it is but that second photo with all the flyers attending their models does something for me - I think it's brilliant!

I really envy those kinds of flying fields, they're perfect for vintage FF.
Ian Easton is offline Find More Posts by Ian Easton
Reply With Quote
Old Jul 22, 2004, 03:22 PM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
Jim - yes, it's Ken Croft's Bugaboo with his home built Weaver 1cc diesel. Much smaller engine than the design used to have, but powers it up well.

Good model for the Bowden type competition as it's reliabe and consistent.

Ian, it's an RAF airfield used for training during the day. We get it for freeflight from around 5.30pm on Wednesday evenings throughout the summer and on quite a few weekends too. Much freeflight competition work and a lot of sport flying with much of that vintage. Some of the models are vintage too!
Tony Oliver is offline Find More Posts by Tony Oliver
Reply With Quote
Old Jul 29, 2004, 12:54 AM
Simplicate and add Fun!
graham_mca's Avatar
Sheboygan, WI
Joined Feb 2002
1,030 Posts
Hi Tonyo,... lovely pictures, I have been to Church Fenton just once to watch various FF rubber and power events many years ago... stood in the damp grass watching J.O'D wind.

The event you described is also known in thermal soaring circles (spot the pun) and I remember reading some years ago an explanation which went something like this....

Upon loosing the tailplane and it's required downward moment, the wing whose centre of lift is aft of it's centre of gravity (or centre of rotation?) will rotate forwards. A half bunt will be performed....

now if you are lucky the undercambered wing will now act as a reflexed wing (as in a flying wing model) and the CG will have moved forward with the lack of tailplane weight.... and a balanced system is restored.

As to how this stays inverted with that much anhedral.... maybe the weight of the fin and low slung area has some effect... just guessing here though.

Graham
graham_mca is offline Find More Posts by graham_mca
Reply With Quote
Old Jul 29, 2004, 04:57 AM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
Strange..

We discussed it last night and it revolved (pun?) around the same thoughts. However an alternative idea I had is it works on the same principle as Delphinium as below. High anhedral, low cg and a lot of side area.

Tony
Tony Oliver is offline Find More Posts by Tony Oliver
Last edited by tonyo; Jul 29, 2004 at 07:20 AM. Reason: get the spelling right
Reply With Quote
Old Jul 29, 2004, 05:51 AM
Registered User
vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,705 Posts
Blast from teh past. I vaguely remember seeing p;ane that lost tailplanes exhibit this behviour years ago when I did a little FF.

Flying uspide down is just a way of achieving some kind of pitch stability. With notmnally downforce on teh tail it will dive until it either neds up vertical, or, with assymmetric or undercambered, ends up more or less upside down. Planes with lots of dihedral are stable upside down in yaw if they have enough fin area. As far as roll goes, its an interesting one. I suspect that what happens is that any bank translates to sideslipping and then the fin turns the model until the bank becomes dive angle, and then the pitch stability takes over and settles teh model into a fairly crass glide with wngs level again.

ISTR that the ones I saw generally ended up in steep inverted glides.

The more rearward the CG is to start with the better I think.
vintage1 is offline Find More Posts by vintage1
Reply With Quote
Old Jul 29, 2004, 07:24 AM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
Hi v1! Unfortunately for that theory, the fins(twin fin model) are attached to the tailplane and came off with it. That left a stabilising(?) tailboom with hardly any area - side or top, a pylon with the wing below it (inverted V) and the engine well above the line you would expect the cg to stabilise using dihedral only.

Very strange but also very amusing.
Tony Oliver is offline Find More Posts by Tony Oliver
Reply With Quote
Old Jul 29, 2004, 08:13 AM
Registered User
vintage1's Avatar
East Anglia, UK
Joined Sep 2002
29,705 Posts
Hmm.

I'll put the thinking cap on then...

So basically, a polyhedral wing with the CG in the right place juts glides upside down?
vintage1 is offline Find More Posts by vintage1
Reply With Quote
Old Jul 29, 2004, 09:19 AM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
I doubt it.

There's a whole new line of research for someone to start - but it could be a bit expensive on models.

I suppose that when you try and glide a polyhedral wing over long grass it will rotate as Graham says. If that is so, then there must be a point where it changes from rotating one way to rotating the other (pitch up changes to pitch down or vice-versa). Find the point of pitch up starting and you've a flying wing. Pick a section which is moderate in its reaction and there's a stable wing. Who needs a tailplane?

Tony
Co-Moderator, Flying Wings (not a lot of people know that )
Tony Oliver is offline Find More Posts by Tony Oliver
Last edited by tonyo; Jul 29, 2004 at 09:22 AM. Reason: still trying to type too fast
Reply With Quote
Old Jul 29, 2004, 11:23 AM
Old Timer
California Condor's Avatar
CARMICHAEL, CALIFORNIA USA
Joined Apr 2001
3,916 Posts
Quote:
Originally Posted by tonyo
I doubt it.

There's a whole new line of research for someone to start - but it could be a bit expensive on models.

I suppose that when you try and glide a polyhedral wing over long grass it will rotate as Graham says. If that is so, then there must be a point where it changes from rotating one way to rotating the other (pitch up changes to pitch down or vice-versa). Find the point of pitch up starting and you've a flying wing. Pick a section which is moderate in its reaction and there's a stable wing. Who needs a tailplane?

Tony
Co-Moderator, Flying Wings (not a lot of people know that )

These models (free flight 1950) flew inverted when the stabilizer came off during dethermalizing. Glide was good enough that no damage resulted. I even launched the 1/2A without the stablizer as a stunt and it made a siccessful flight. In more recent times I have lost the stab on an Ohlsson 60 powered Megow Comander and landed it with little damage as it went inverted. The wing sections on these models are stable (reflexed) inverted.
Eut
California Condor is offline Find More Posts by California Condor
Reply With Quote
Old Aug 01, 2004, 03:38 PM
Registered User
Tony Oliver's Avatar
North-East England
Joined Mar 2002
3,402 Posts
Strange end...

It's just done it again!

I was flying at the Geordie Nats today and this time the engine over-ran and the d/t popped. The tailplane came off on the third loop and the model settled down - under power this time and landed in some rubble so there's some damage.

Only difference in the flight was that being under power it did turn (left) but was still stable.

Tony
Tony Oliver is offline Find More Posts by Tony Oliver
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question Strange End Bell on an Astro Motor. RobZ Power Systems 17 Jan 09, 2007 11:01 PM
Alert losing tail control near end of flight. aftica Micro Helis 3 Nov 03, 2005 11:12 AM
Batteries at end of flight picasso Batteries and Chargers 11 Mar 05, 2004 12:37 PM
What a way to end a flight ....... Alfred Electric Sailplanes 18 Nov 11, 2003 05:07 AM
1.4 mah still left after end of flight ThomasJoehnk Batteries and Chargers 2 Jun 29, 2003 02:28 PM