Bumper yaw string

As a convert and owner - I don't understand why glider manufacturers haven't adopted the Mk IV as standard fit for new gliders.

On Tue, 01 Dec 2015 01:09:17 -0800, jpg797 wrote:

As a convert and owner - I don't understand why glider manufacturers
haven't adopted the Mk IV as standard fit for new gliders.

Agreed, and searching for and making improvements to anything is never a
'sickness', but a history of kludging stuff might well be one.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Monday, November 30, 2015 at 11:28:38 PM UTC-6, bumper wrote:
I received a private email asking why the MKIV is better than taped yarn and what improvements occurred between the various MK's. I'd like to share my response:


Were to start?!

Firstly I wanted to get rid of the tape. When tape residue hardens, it can be extremely difficult to remove. Clear tape is the absolute worst. UV degrades the plastic part and the underlying adhesive is like concrete. The plastic won't peel off but stays intact enough to "protect" the adhesive from any solvent one is brave enough to use on the acrylic. Denatured alcohol, applied briefly is about as brave as I can get. I've spent almost an hour removing one of those on one of *redacted - a famous supporter of soaring* ships. No thanks.

So there were two primary goals. Get rid of the tape and make sure that what replaced it would come off cleanly when that time arrived. Also the base should be completely clear. And shaped to help minimize static yarn static cling and keep it clear of the canopy in flight (no touching so no yarn "wipe mark" from fine scratches).

Initial change from MKI to MKII was shape only. The MKI was shaped like a baseball diamond, pointy end forward. The MKII is 3/4" long and pie shaped in a sense, it being cut from a 3/4 inch circle rather than a 1 1/2" circle (which would make it a real pie shape).

MKII to MKIII was an overlay plastic material change. But sill using semi-rigid plastics with a mechanically pressed yarn channel.

MKIII to MKIV changed to a softer plastic overlay (edit - less tendency to lift up off canopy at the edges), with a thermoformed yarn channel.

Subsequent improvements did not result in a MK number change, but included injecting a polymer into the base yarn after final assembly to help prevent yarn pull-outs. Not a common problem, but there were a few. There were a number of lesser improvements relating to assembly methods, mostly for quality, consistency, and for ease of assembly.

Included index dot (some use them to mark center line inside canopy) has changed from paper to plastic and finally to "white" reflective tape. Light color so it doesn't fool the peripheral vision into thinking it's another aircraft. Size has changed too, and is now 5 mm.

A recent change to a corner rounding punch to cut the rear radius was a complete flop. Could not make it do as nice a job trimming the clear double sided adhesive as doing it the old way by hand using scissors. It looked so good going in and I spent hours trying to get it to work. Can't win them all.

The shape, like one section of zig-zag tape, creates two tiny vortices to help keep the yarn "alive", while the .038" base thickness and yarn tunnel keeps the yarn from touching the canopy in flight.

There are some 30 steps in manufacturing each MKIV, along with a dozen primary jigs and fixtures and a number of custom made tools as well. All to make the job go a bit smoother and to insure perfect alignment of center yarn hole, yarn, base, adhesive, and a bubble free clear laminate. All resulting in a small thing that looks befitting of the ship it goes on.

all the best,

bumper

Whatever you did, Bumper, it works! Plus, the darned thing lasts forever (this would never happen at GM). Mine is a yellow synthetic string that's on the glider now for 4-5 seasons, 120 hours per year in the air. I had a spare that was aging in the envelope it was sent in, no need so far to use it so I gave it away. The attachment plastic is still clear after all this time!

A comment to Bumper's worries about tape residue:

I could only imagine that the tape on my 14-year old LAK-17a was
original to the ship and it was with great trepidation that I undertook
to replace it with a MKIV. As it turned out, the plastic part of the
tape simply popped off as easily as though it would have on its own on
the next flight leaving a huge mess of adhesive. With great care I
touched it with a finger nail and, to my delight, it simply flaked off.
It only took a minute or two of gentle scratching with my fingernail and
it was all gone! Then a bit of spit and a gentle rub with a microfiber
cloth and the canopy was pristine and ready for my new upgrade.
Couldn't be happier!

On 11/30/2015 10:28 PM, bumper wrote:
I received a private email asking why the MKIV is better than taped yarn and what improvements occurred between the various MK's. I'd like to share my response:


Were to start?!

Firstly I wanted to get rid of the tape. When tape residue hardens, it can be extremely difficult to remove. Clear tape is the absolute worst. UV degrades the plastic part and the underlying adhesive is like concrete. The plastic won't peel off but stays intact enough to "protect" the adhesive from any solvent one is brave enough to use on the acrylic. Denatured alcohol, applied briefly is about as brave as I can get. I've spent almost an hour removing one of those on one of *redacted - a famous supporter of soaring* ships. No thanks.

So there were two primary goals. Get rid of the tape and make sure that what replaced it would come off cleanly when that time arrived. Also the base should be completely clear. And shaped to help minimize static yarn static cling and keep it clear of the canopy in flight (no touching so no yarn "wipe mark" from fine scratches).

Initial change from MKI to MKII was shape only. The MKI was shaped like a baseball diamond, pointy end forward. The MKII is 3/4" long and pie shaped in a sense, it being cut from a 3/4 inch circle rather than a 1 1/2" circle (which would make it a real pie shape).

MKII to MKIII was an overlay plastic material change. But sill using semi-rigid plastics with a mechanically pressed yarn channel.

MKIII to MKIV changed to a softer plastic overlay (edit - less tendency to lift up off canopy at the edges), with a thermoformed yarn channel.

Subsequent improvements did not result in a MK number change, but included injecting a polymer into the base yarn after final assembly to help prevent yarn pull-outs. Not a common problem, but there were a few. There were a number of lesser improvements relating to assembly methods, mostly for quality, consistency, and for ease of assembly.

Included index dot (some use them to mark center line inside canopy) has changed from paper to plastic and finally to "white" reflective tape. Light color so it doesn't fool the peripheral vision into thinking it's another aircraft. Size has changed too, and is now 5 mm.

A recent change to a corner rounding punch to cut the rear radius was a complete flop. Could not make it do as nice a job trimming the clear double sided adhesive as doing it the old way by hand using scissors. It looked so good going in and I spent hours trying to get it to work. Can't win them all.

The shape, like one section of zig-zag tape, creates two tiny vortices to help keep the yarn "alive", while the .038" base thickness and yarn tunnel keeps the yarn from touching the canopy in flight.

There are some 30 steps in manufacturing each MKIV, along with a dozen primary jigs and fixtures and a number of custom made tools as well. All to make the job go a bit smoother and to insure perfect alignment of center yarn hole, yarn, base, adhesive, and a bubble free clear laminate. All resulting in a small thing that looks befitting of the ship it goes on.

all the best,

bumper


--
Dan, 5J

Having purchased many* "Quiet Vent Kits" and one "Kiddie Car Tailwheel Kit" from Bumper, I remained skeptical about the yaw string until buying a glider with one already installed.
Great stuff.
Jim

* excellent gifts

Thank you much and very interesting. Just kind of shows anything can be improved, even yarn taped to a canopy! Perhaps you could do the same with the Quiet vent, how does that work. Just for full disclosure I did buy a Mark IV and a quiet vent, but have yet to install them and have never seen either in practice.


On Monday, November 30, 2015 at 9:28:38 PM UTC-8, bumper wrote:
I received a private email asking why the MKIV is better than taped yarn and what improvements occurred between the various MK's. I'd like to share my response:


Were to start?!

Firstly I wanted to get rid of the tape. When tape residue hardens, it can be extremely difficult to remove. Clear tape is the absolute worst. UV degrades the plastic part and the underlying adhesive is like concrete. The plastic won't peel off but stays intact enough to "protect" the adhesive from any solvent one is brave enough to use on the acrylic. Denatured alcohol, applied briefly is about as brave as I can get. I've spent almost an hour removing one of those on one of *redacted - a famous supporter of soaring* ships. No thanks.

So there were two primary goals. Get rid of the tape and make sure that what replaced it would come off cleanly when that time arrived. Also the base should be completely clear. And shaped to help minimize static yarn static cling and keep it clear of the canopy in flight (no touching so no yarn "wipe mark" from fine scratches).

Initial change from MKI to MKII was shape only. The MKI was shaped like a baseball diamond, pointy end forward. The MKII is 3/4" long and pie shaped in a sense, it being cut from a 3/4 inch circle rather than a 1 1/2" circle (which would make it a real pie shape).

MKII to MKIII was an overlay plastic material change. But sill using semi-rigid plastics with a mechanically pressed yarn channel.

MKIII to MKIV changed to a softer plastic overlay (edit - less tendency to lift up off canopy at the edges), with a thermoformed yarn channel.

Subsequent improvements did not result in a MK number change, but included injecting a polymer into the base yarn after final assembly to help prevent yarn pull-outs. Not a common problem, but there were a few. There were a number of lesser improvements relating to assembly methods, mostly for quality, consistency, and for ease of assembly.

Included index dot (some use them to mark center line inside canopy) has changed from paper to plastic and finally to "white" reflective tape. Light color so it doesn't fool the peripheral vision into thinking it's another aircraft. Size has changed too, and is now 5 mm.

A recent change to a corner rounding punch to cut the rear radius was a complete flop. Could not make it do as nice a job trimming the clear double sided adhesive as doing it the old way by hand using scissors. It looked so good going in and I spent hours trying to get it to work. Can't win them all.

The shape, like one section of zig-zag tape, creates two tiny vortices to help keep the yarn "alive", while the .038" base thickness and yarn tunnel keeps the yarn from touching the canopy in flight.

There are some 30 steps in manufacturing each MKIV, along with a dozen primary jigs and fixtures and a number of custom made tools as well. All to make the job go a bit smoother and to insure perfect alignment of center yarn hole, yarn, base, adhesive, and a bubble free clear laminate. All resulting in a small thing that looks befitting of the ship it goes on.

all the best,

bumper

On Tuesday, December 1, 2015 at 8:23:41 AM UTC-8, Jonathan St. Cloud wrote:
Thank you much and very interesting. Just kind of shows anything can be improved, even yarn taped to a canopy! Perhaps you could do the same with the Quiet vent, how does that work. Just for full disclosure I did buy a Mark IV and a quiet vent, but have yet to install them and have never seen either in practice.


Okay, briefly:

Soaring, should be serene and peaceful, at least when not doing a low save. When flying in the high desert, the experienced pilot should remain cool under the collar. And that Mecaplex flip-out vent sure was noisy, making a particularly bothersome low frequency noise.

The problem is caused by the air hitting the flip out vent, the back edge of the opening, the hinge block and the inside handle when the vent is open. All of the creates turbulence which impedes airflow and makes noise - in a glider that's supposed to be quiet.

The fix is the QV kit. It's made of clear plastic and when installed you won't notice it visually unless you look closely. The QV attaches to the inside handle of the flip-out vent and seals against and near the vent's leading edge to give the incoming air a smooth, rounded transition all the way into the ship. The flow is smoothed, less turbulent, and more air can enter more quietly.

To test in my ASH26E, I installed a QV, then at 60 knots measured the sound level at my ear level. Then, maintaining same speed, wasted a perfectly good QV by ripping it off and repeating sound level measurement. The reduction in noise was 10 dba! Each 3 dba represents a halving of sound pressure level, so dba is a quite significant reduction AND that irksome low frequency component of the noise was all but gone.

The QV was a winner! But, there were initial problems. The material I used at first was too thin, and any alignment error would have the QV acting like the reed on an oboe. This turned out to be quite unpopular, with some pilot ripping the damn thing out. Some others would go high in wave where even a gentle bumping of the QV would have it detach due to the extreme cold - - they were unhappy with me too.

Both issues were fixed of course, and there must be a thousand QVs are out there making soaring more enjoyable, or at least quieter when slowed up, hot, and trying to do a low save.

Price is $9 USD, and as with all the stuff I foist upon the soaring community, satisfaction is guaranteed.

The QV fits Mecaplex flip out vent. A version is available for the Antares on request.


I truly appreciate all the previous positive comments. Thank you everyone!

Am Mittwoch, 2. Dezember 2015 17:29:48 UTC+1 schrieb Sean Fidler:

For what it's worth, I'm flying with 3 yaw strings now. Center left and right. When thermaling I'm never looking straight ahead and I also have a spare front string forward of the center primary. 4 total.

Whow.

On Wednesday, December 2, 2015 at 11:02:43 AM UTC-6, Tango Whisky wrote:
Am Mittwoch, 2. Dezember 2015 17:29:48 UTC+1 schrieb Sean Fidler:

For what it's worth, I'm flying with 3 yaw strings now. Center left and right. When thermaling I'm never looking straight ahead and I also have a spare front string forward of the center primary. 4 total.

Whow.

Triple Wow, he's one of a kind...
https://www.youtube.com/watch?v=fxt759HTp44

Shaun the sheep video notwithstanding, if one were tied to a chair and forced to put up with that over and over, how long do you suppose it would take before you'd go stark ass bleating crazy?

Once upon a long time ago, it was postulated as to how natural wool yarn was less abrasive to glider canopies. I have not data one way or the other, but one could order natural wool or synthetic yarn for their MK#. Most chose natural wool.

I've tested yarns and found synthetic yarn lasts longer. I've also done testing of the MK# yaw strings, holding a curved acrylic surface out the window of my truck, to mimic a glider canopy, so I could view the string from the side. Due to the design of the MK# base, the yarn streams back maintaining the lift and separation imparted by the base, and looks to maintain that separation all the way back not appreciably touching the canopy at all.

With a normally maintained canopy, no scratching. If left parked out, uncovered, and with blowing dust or sand, I'd expect any string or yarn material might cause fine scratches. Loose covers can cause deep scratching.