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Old Oct 26, 2008, 11:28 AM
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Quote:
Originally Posted by ssassen
I'm going to respectfully have to disagree with you here. How is one to know the structural limits of a model airplane? Due to the scale factor they can take far more 'abuse' that a full scale airplane, hence other than trail-and-error it is hard to guesstimate how well the wing (or any other part of the airplane) is going to hold up under stress.

I routinely put my planes through a level of stress that would rip a full scale airplane to bits and pieces and up until now I haven't lost any due to structural failure. So to my opinion and experience Jim wasn't doing anything wrong here, frankly he probably saved the plane from a crash at a later date that might not have ended this well as the pilot would've been his buddy, who most likely has not practized this scenario in the simulator, hence kudos to Jim for saving his buddy's airplane.

Cheers,

Sander.
Exactly what I meant.

Quote:
Originally Posted by AIVIA
Sorry Jim, but I find it unbelievable that NO ONE has called you to the carpet for conducting a snap roll at full throttle and, presumably, at a high rate of speed such that it exceeded the structural limit of the wings.

Given your extensive model aviation experience, as well as your experience with full scale aviation, you should have known better! Especially considering the recent repairs done to the wing!!

Don't take this personally, but everyone here is putting you on a pedestal for a good save, when in fact you broke a buddy's perfectly good airplane through bad judgment and poor technique.

I know some folks will suggest Iím being a first-class jerk, but everyone should spend some time reading this forum:

http://www.airtalk.org/1-vt16256.html?start=0

Here is the disclaimer Ö this forum is discussing full scale aircraft and we all know that most models are built to withstand higher G loads. However, the basic principle is still the same Ö snap rolls should not be conducted at speeds greater than 2 times the stall speed. Since most of us donít have live telemetry showing the airspeed of the model, a general rule of Ĺ throttle in level flight would be safe. On down lines, itís safe to say that the throttle should not be greater than Ĺ as well.

If you conduct snaps above these speeds, you are flying at risk and will likely break the airplane. This video is a perfect case-in-point! It might not break the first time you do a high speed snap, but over time you will certainly fatigue the airplane to the point of structural failure.

So, good save Jim, but shame on you for creating this situation in the first place.

I will now put on my flame retardant suit ... flame on everybody ...

How do we know the limits??
Are we supposed to buy some machine that will keep pulling on the plane until it snaps? Then we will know??
Many modelers probably don't worry about the limits, if the plane was high quality [Maybe Jim skipped some steps(I don't know)] and he did that maneuver (Sorry if I spelled it wrong, No one is perfect) this would have never happened.
I see people at the field do WAY more stressful things to their planes, without EVEN CONSIDERING the plane might fall apart.
But from your post it seemed as if everyone should monitor their planes (Which they all do) But to a point where a person has to obsess over their plane and fix every last tiny crack. [Which in reality will do NO HARM]
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