|
|
Jul
8
Written by:
Jeff O'Brien
7/8/2010 5:50 AM
Why are we risking safety for 1/64th of an inch ???
In the past month, there have been two high profile failures of 2mm a.k.a. (5/64th inch, skinny, racing) bottom sidewires.
The first was Bill Soderquist's catastrophic sidewire failure pulling up into a loop and DRAMATIC deployment which left him bruised and with broken ribs. It could have easily been much worse.
Bill Soderquist keeping his cool during the deployment chaos in June.
Then just a few days ago, UK National Champion Dave Shields apparently broke a 2mm sidewire doing aerobatics over the LZ in Ager, Spain. Details are sparse, but this photo below was gleaned from Facebook.
Dave Shields working over his wreckage.
Manufacturers have stressed the need to regularly replace 2mm sidewires and to not accept any kink or permanent set in the wire. They have also warned to not do aerobatics on 2mm sidewires.
In my opinion, this is too hard to personally police. Replacing is easy, abstaining from aerobatics is not. During competitions on a free flying or called day, it's a natural tendency to express yourself. (some competitors like to express themselves while waiting for the start clock) Most of us enjoy aerobatics to one degree or another.
Additionally, I've probably experienced higher G loading on a turbulent final glide for example. Going slack and being subsequently slammed down on a 70mph final glide makes you slow down and take stock to make sure things are still intact. There's no control over air anomalies.
Mike Meier ran a calculation recently taking into account the drag differences between 3/32 (thicker) and 5/64 (thinner) wires over a 2.5 hour flight and found a negligible difference in performance. (Like less than 100ft. of altitude over the duration)
Even without the calculation, I'm convinced to run the more robust 3/32 wires at all times now. My US teammates are considering the same.
Tags:
9 comment(s) so far...
Re: "Thicker" is better...
The "racing" T2C that I borrow/rent from Wills Wing came with the thick wires on the sides and the racing wires in the front and back. Tom Lanning's came that way also.
Glad to see that you are going to join us.
By Davis Straub on
7/8/2010 6:24 AM
|
Re: "Thicker" is better...
how much thinner are the stock wires if you strip the plastic off of them?
By Pat Halfhill on
7/8/2010 6:30 AM
|
Re: "Thicker" is better...
I've wondered that for a while now - how much less drag is there by using slightly thinner wires? Thanks for the post Jeff.
By David Aldrich on
7/8/2010 6:52 AM
|
Re: "Thicker" is better...
When they break, where do they break? Mid-span? At the nico-press junction or in the loop itself?
By Alan on
7/8/2010 7:18 AM
|
Re: "Thicker" is better...
Steve Pearson recommended using the thin wires only during competitions. However, I decided that unless I'm competing in a speed gliding contest, I'm using the thicker wires. The thicker wires offer more peace-of-mind and don't hurt performance much most of the time and can greatly improve glider performance in some circumstances. (I don't think Dave's glider glided very well the next day).
By Tom Lanning on
7/8/2010 7:54 AM
|
Re: "Thicker" is better...
Double side wires could be a mandatory requirement to participate in aerobatic competitions. And eventually all competitions.
Could become the industry standard for all gliders!
If everybody has the extra drag, then everybody is still even but SAFER!
Sidewire failure and failure to hook in, still haunt all HG pilots every day, in every single flight. Double flying wires and harnesses permanently attached to all gliders are two good improvements (the harness could have a piece of the Xbar haul back wire permanently attached, so you couldn´t pick up the glider without it).
Long overdue, if you asked me.
Perhaps the USHGA, DHV, USHGPGA should get together and just start making all gliders this way.
Boy, what a peace of mind that little extra drag would bring us!!!!!!!
By Juan Carlos Costa on
7/9/2010 4:29 PM
|
Re: "Thicker" is better...
My sidewire failure was just out of the nicopressing on a wire with just around 100 hours airtime very little of which included aerobatics (maybe 2 days at Stanwell park in January). At the time the wire failed I was pulling 122kph (taken from vario) to build speed and was flying with straight arms but was not pushing out! The glider was rounding out at the bottom of the dive. Eye witnesses reported a dusty or thermal in the field moments after my incident. Maybe this caused a shock loading? Who can say!
What i do know is that the wires on my replacement glider will be slightly thicker.. maybe the 7x7 type for greater flexibility too!
I can send pics of the failed wire if it helps...
By Dave Shields on
7/10/2010 7:57 AM
|
Re: "Thicker" is better...
My sidewire also failed at the nico but it was obvious the tang was kinked at the time of failure. This greatly reduces the performance of the wire. There is no doubt the sidewire kinked during the tumbles as it had definitely been checked during preflight, and by the launch marshal only seconds before towing out of the airfield. A thicker sidewire in my case most likely would have failed also. Point being, a stronger sidewire also needs the correct 'never-kink' size, it requires the same amount of care, checking and maintenance. No redundancy here. What we launch with is what we rely on. Glad Dave is OK.
By adam parer on
7/10/2010 7:50 PM
|
you're winning
turn your head sideways for 5 seconds and you've lost all the performance gained from skinny wires for the entire flight.
Or any number of blunders that results in an aerodynamic disruption, at what cost? breaking your glider in flight, that's what.
The glider breaks positive at max lift, around 20-25º AoA to the relative airflow. Skinny wires tested to failure around 450-575 #, stock wires 890-1250# in my experience, your results may vary.
How much performance do you think you're getting from a reduction in the diameter of the side wires?
you're winning.....
By Mitchell McAleer on
7/12/2010 7:19 AM
|
|
|