Peter, PJ, Ray, et all:
I know that crash #1 involved the lines going slack, and thinking about yesterday (gusty wind) I think that could be the cause of crash #3 as well. The contributing cause of crash #2 was a severely nose-heavy plane: hanging on the up- or down-line, the thing would do a loop whose diameter projected out to about a 30 degree height, and at the time of the crash I was purposely giving it tons of input to verify that yes, I really did need to make a balance change and not a handle change.
Larry:
It's a 34 ounce plane and those clips have been pull tested. The line is 015, which is one step larger than the required 012 from the rule book. I can't remember the exact pull strengths, but the clips don't severely distort until I'm over the 21 pound pull for the whole plane, on one clip, and they don't distort permanently until I'm up around 50 pounds or so -- and even then, the permanently distorted clip carries the weight OK, it just looks Really Bad. I haven't had a flight -- even with some go-slack-and-bang events -- that has permanently distorted a clip, so I feel quite safe using them.
And, as I've mentioned elsewhere in this thread, I've had this trouble happen on lines with much nicer terminations. It is not the terminations that are catching -- it is the line itself that is getting caught up in the clip. So while I'm not going to build another set of lines with terminations that ugly, I don't think that's the problem in this case.
Peter:
If anything, the plane in its current trim is a bit tail-heavy (crash #3) -- but crash #2 certainly seemed to be brought on by a combination of nose-heavy and my ham-fisted diagnostic procedures.
I think that -- being a beginner -- I must be jerking on the lines when things get "interesting". I suspect that will go away with time, but in the near-term I think that some sort of anti-snag protection on the line clips itself is what I need to do: once I get better I can maybe toss them, but until that day I just need training wheels.