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Apr 18, 2016, 12:36 PM
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rthebruce's Avatar
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Oly III redline?


Does anyone have an idea of what the max speed should be for an Oly III? I didn't think I was going that fast but lost my rudder mid-flight. I'm wondering if there may have been some weakness in the wood used for the rudder, as it made a clean break at the stabilizer. (And yes, it was assembled with care and straight.)

The good news is that I did manage to land it without further damage.
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Apr 18, 2016, 01:35 PM
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Oly's have been around since 70's. Never heard rudder coming off. Might want to add some more glue and tri-stock as bracing.
Apr 18, 2016, 02:23 PM
aku
aku
Jeff Cheechov
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Wondering...


You lost the vertical stab, correct?
* Does Ray's Oly III design use any triangle stock to support the v-stab?
* Did you trim away the covering on the glue area?

Glad you were able to land it intact
Apr 18, 2016, 03:21 PM
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well that's the thing... I _did_ have tri-stock supporting the vertical stab. Snapped off right above it.

Since I've added ailerons I'm going to design a somewhat smaller vert. stab / rudder, maybe removable, and correctly connect my airspeed indicator. I was just wondering what people would consider 'too fast' for this plane.
Apr 18, 2016, 05:24 PM
aku
aku
Jeff Cheechov
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I have no idea about airspeed, as I have no flying instruments onboard. I fly these balsa birds pretty slowly. If it snapped above the tri-stock I would say you were over-speeding, or the v-stab balsa was too soft for your application.
Apr 18, 2016, 07:03 PM
aku
aku
Jeff Cheechov
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Oly II


I'm also remembering the lower balsa sub-post on the stab that indexed between the fuse sides on the original Oly II. Maybe Lee had it right the first time
Apr 18, 2016, 10:16 PM
jjc
jjc
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Any chance your rudder fluttered momentarily and ripped the vertical fin off, do to flex in the control rod or slop somewhere in the rudder controls? John
Apr 18, 2016, 11:19 PM
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prodjx's Avatar
What % of rudder input did you have in relation to aileron input? That had to be some serious lateral movement to snap the fin/rudder off the way it did. Was the L/E of the fin balsa or spruce?
Apr 19, 2016, 06:40 AM
Kurt Zimmerman ≡LSF 4461≡
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From my experience loosing a tail surface is caused by flutter. Some designs are more prone to flutter than others. Same designs may vary depending if there is any slop in the control surface or how rigid the control surface is.

Several things to keep in mind. 1) make sure there is ZERO slop in moving surfaces. 2) during the building stage keep in mind how rigid the control surfaces are. Extra reinforcement may be needed by changing out spar or support structures with bass or spruce or carbon fiber.

Years ago I crashed a 30% scale Extra 230 due to a poor design removable tail design. I built the second plane mounting the tail without making it removable. I also laminated .007 carbon on the stab spar along with the fin post just to avoid any flexing. Those simple changes made for a much safer design. I flew the crap out of that plane with no worries of flutter or flexing.

YMMV
Kurt
Apr 19, 2016, 06:47 AM
Fly to live- Live to fly
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My two cents about that issue is ... before... Olys are not designed to go fast...rather all contrary... likes to go slow and if you continues trying to go speeding very probably will go dissapoint... you and the airplane... all airplanes and model airplanes have a red line... whatever theyīre and flight envelope must be respected... on the other hand a woodie built sailplane have itīs own limits by design and materials... modern composites have more room to withstand the add stress of speed, but this vintage... even newer version... must be flown on its paces...
Anyway... I would say that with the overspeed maybe you experience some rudder flutter and cause the tear of the full vertical stab... After a carefully glue the pushrods tubes and a no slop transmision, one little thing that have its own importance and maybe adds some km. more on the limits is to seal the separation between the flying surfaces and controls... a strip of monokote en both sides of the rudder and elevator helps keeps flutter a bit down and enhances security... I always add on all my models; sailplanes, classics aerobats or 3D from small electrics to big gassers, sport scale and so...itīs incredible how a little thing does so much for the model performance, handling and security...
Best regards buddies.
Manolo.
Apr 19, 2016, 07:27 AM
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whacker's Avatar

Picture, Pictures


Has anyone seen a picture of the break

One of the fin, the other at the fuselage.

Regardless of how the forces where created to cause the failure, it is conjecture to suggest excessive speed caused a failure.

The fin could well have been previously damaged, or not attached securely

rthebruce do you have a picture or two


Added, based on Picture

I wonder If the base of the fin was built like this?

If the LE post is soft balsa, then I can well see a clean break at the glue joint of the bottom two pieces of 1/4" square.
Also the fins TE post may have not been glued to the fuselage, something easily overlooked during a build



whacker






Does anyone have an idea of what the max speed should be for an Oly III? I didn't think I was going that fast but lost my rudder mid-flight. I'm wondering if there may have been some weakness in the wood used for the rudder, as it made a clean break at the stabilizer. (And yes, it was assembled with care and straight.)

The good news is that I did manage to land it without further damage.
Apr 19, 2016, 08:21 AM
Registered User
The built up version sure looks weak. I would have added gussets to vertical fin. Prehaps hader wood also. Sincw glider landed without any more damage make strong fin. Perhaps add a couple dowels also. solild wood.
Apr 19, 2016, 02:50 PM
Intermediate Multi
Trisquire's Avatar
I've seen Oly IIIs, both in kit form and completed. That things a tank. It would survive a hurricane.
Apr 19, 2016, 10:19 PM
Registered User
I never seen any glider lose a rudder in flight or heard of it. Maybe bumped before flight and not aware of damage? Hanger rash does happen.


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