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Author Topic: Causes of tension - d/t lines, triggers, etc.  (Read 539 times)
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RobinB
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« on: October 13, 2011, 12:43:38 PM »

Trimming out a new SLOP model recently I was reminded that things that look reliable on the bench
can be less so when one actually gets to the field. The d/t line on that model passes from a hook on the stab,
around a radiused block under the TE and straight to the timer. I use a thin flexible steel line with a small tension spring
on the end that hooks on the timer arm.
I noticed that the tension in the system was causing the timer arms to bend, and I had to bend a more hook-like shape into them
to retain the line safely.
This was a Polish SLOP timer from FFS; I've since changed it for a Texas timer, which has thicker release arms.

I know that it's a bit more fiddly, but I think I'll fit a trigger setup in future models. It should reduce the tension in the timer line.

Anyone else had this problem, and come up with reliable solutions?

I'm a bit fussy about these things nowadays as I once had a model d/t halfway into the climb. It's not an experience I want to repeat!

Robin
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gossie
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« Reply #1 on: October 13, 2011, 10:53:12 PM »

You sure need tension to hold things down and in place, but perhaps a little too much tension?Huh??   Just a thought. Smiley
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glidermaster
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« Reply #2 on: October 14, 2011, 11:32:54 AM »

Hi Robin,
My most recent SLOP type models had the system as you describe, and I too don't like the tension it puts into the timer arm. My most recent build which is somewhere in these pages has a VIT type trigger to hold the tail trailing edge, and I much prefer it. One of the benefits (to my mind at least) is that the line can be pseudo-permanently hooked to the timer, so there are no accidental hook up errors.

(I say pseudo-permanently - I make a loop on the timer arm, and use a little sprung hook on the line, so I can take the timer out if need be, without cutting the lines!).

All my old FAI models have permanently attached lines and I had to replace all the arms on my Seelig timers in order to do that.

I am concerned with the systems on my latest Russian model - hooking all the lines up every flight - there's a lot of them. Angry
John
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RobinB
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« Reply #3 on: June 08, 2012, 08:05:23 AM »

I was sorting out the d/t on a Dixielander (another model that I seem to have had on the go for an embarrassingly long time),
and was pleased to find that it didn't need as much tension in the line as the SLOP mentioned above.

It had the same stab chord, same rubber bands, same type of tail platform and same retaining line set-up.
Then the penny dropped - the peg on the Dixie is further back up the stab (nearer max. thickness point), so a larger component of the band's tension is forward, against the stop, than if the peg / hook was nearer the LE.

Obvious when you think about it. Duh!

Robin
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