Replacing the MKIV yaw string - tips

On Dec 1, 5:24*pm, Martin Gregorie
wrote:
On Sat, 01 Dec 2012 14:29:59 -0800, Mike Mike Ground wrote:
The MKIV is clearly the pinnacle of yaw string technology.
Meticulously crafted, it looks great on my glider. * *However, it
suffers from the same problem I have noticed on all yaw strings I have
flown. * *In flight, it constantly swings off the centerline 10, 20,
sometimes even 30 degrees, particularly while thermalling. * What’s up
with that?

How careful were you to place it on the center-line?

The tighter the curvature of your canopy near the centre line the more
critical yaw string placement is. For instance I think that, on a
Libelle, you need to place it within 5mm (1/4") or better of the exact
centre line, but probably canopies that aren't so sharply curved near the
centre line would make the string placement less critical. I stretched a
thread from the exact top of the fin down to the nose and took a lot of
care that both ends were correctly placed and that it wasn't deflected by
the top of the canopy before marking that line and fitting the yaw
string.

By contrast, I suspect that aligning the axis of symmetry of the
transparent sticky bit with the glider's centre line is more important
for aesthetics than for the yaw string's operation. In any case, by using
pencil marks on masking tape placed before and behind the sticky bit and
taking care, you should be able to align it well enough that errors can't
be seen once the masking tap and thread are removed.

You say the string is often deflected to one side: of course, it should
be tail out in a properly flown thermal turn and dead straight when you
cruise straight between thermals.

If it doesn't do that, it might be that:

1) its mounted off to one side. Check with a thin line as I did to see
* *if its not accurately on the centre line.

2) you've picked up the habit of flying sideways.

Either could make it hang consistently to one side. Either way you need
to work out what's causing it and correct the problem.

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

I carefully leveled Uniform Fox, then used a laser level to 'draw' a
line perfectly centered line on the fuselage from the nose to the TE
probe on the tail. I'm quite certain I netted a 10% performance gain
with the MkIV.

On Friday, 30 November 2012 15:36:29 UTC-5, bumper wrote:

These instructions are for use if you're happy with the current position of the MK## yaw string. If not, please refer to the new installation instructions available at http://www.cumulus-soaring.com/bumper.htm or http://www..williamssoaring.com/cata...ane-parts.html or from me via email.

How can I calibrate it to warn about air pockets? There're everywhere!

On Thursday, December 6, 2012 8:46:53 AM UTC-8, AGL wrote:


How can I calibrate it to warn about air pockets? There're everywhere!

Dear AGL,

The MKIV comes factory calibrated for air pockets and no further adjustment should be necessary.* The MKIV will indicate the presence of a significant air pocket (at least the ones we have around here) by pointing straight up.

Assuming your head has not punched a hole in the canopy, air pocket recovery will be reliably indicated by the MKIV yarn coiling neatly around the base in a counter-clockwise direction - - watch for it as this moment will be fleeting.

*Unfortunately there is a little bit of hysteresis error that we have not been able to correct for.

bumper

On Thursday, December 6, 2012 10:33:40 AM UTC-5, Grider Pirate wrote:
I carefully leveled Uniform Fox, then used a laser level to 'draw' a
line perfectly centered line on the fuselage from the nose to the TE
probe on the tail. I'm quite certain I netted a 10% performance gain
with the MkIV.

But, its hard to tell, on account of semi-blindess after staring
into the laser...

On Thursday, December 6, 2012 1:14:42 PM UTC-8, Dave Nadler wrote:
On Thursday, December 6, 2012 10:33:40 AM UTC-5, Grider Pirate wrote:

I carefully leveled Uniform Fox, then used a laser level to 'draw' a

line perfectly centered line on the fuselage from the nose to the TE

probe on the tail. I'm quite certain I netted a 10% performance gain

with the MkIV.



But, its hard to tell, on account of semi-blindess after staring

into the laser...

What?! You don't have your own set of laser protective goggles?

Several of our customers have written asking, "What's up with all this blue flame stuff? I thought I was experiencing the rapture.".

At no extra charge, all MKIV "high tech" yaw strings are designed to cleverly "self-illuminate" using luminous plasma (St. Elmo's Fire) for better visibility during exceedingly adverse soaring conditions while flying in and near thunderstorms - - when you need it most.

MKIV's are in use on all continents save Anartica. To remedy this troubling lapse in our world coverage, the first three Antartican glider owners who contact me will get a free MKIV. (Optional propylene glycol treatment available, just pay shipping and handling).

bumper
zz
Minden, NV

I can't believe that the topic of MKIV winter maintenance has gotten no
coverage.

We all know that you have to run an aircraft engine once in a while if
the aircraft is not flown to get rid of acids forming in the crank case
- or whatever. Surely something must be done to the MKIV during the long
winter months in order to keep it performing in top condition.

Every couple of weeks, I pull the fuselage out of the trailer and blow
air from a hair drier (at the *cool* setting) over the MKIV, but wonder
if this is sufficient to maintain optimal performance. Your expert
advice on this subject is requested.

Tony "6N"
P.S. I do *not* simulate tail slides with the hair drier

I'm glad this discussion came back up, I love the MKIV (though club mates enjoy making fun of BUYING a yaw string, ha) Anyway.... I love it so much I have to ask: Is there any advantage to installing one inside the canopy as well? (I though I heard of a near 10% performance gain from such) Also, would my internal turbulators cause any interference?

JP

Hi gang,

I brought one of the Mk. IV's back from SoaringNV this spring, and has used
it on my DG600 in Europe since then, with substantial performance gains, I
might add.
It has gathered crowds everywhere I went, both in my native Denmark and in
the French Alps. The interest seems to be there, so the question is: Bumper,
does any of your R&D divisions have plans for a metric version? I'm sure it
would be an instant hit.

Happy New Year to all,
Lars Peder


"Tony V" wrote in message
...

I can't believe that the topic of MKIV winter maintenance has gotten no
coverage.

We all know that you have to run an aircraft engine once in a while if the
aircraft is not flown to get rid of acids forming in the crank case - or
whatever. Surely something must be done to the MKIV during the long winter
months in order to keep it performing in top condition.

Every couple of weeks, I pull the fuselage out of the trailer and blow air
from a hair drier (at the *cool* setting) over the MKIV, but wonder if
this is sufficient to maintain optimal performance. Your expert advice on
this subject is requested.

Tony "6N"
P.S. I do *not* simulate tail slides with the hair drier

On Monday, December 31, 2012 6:58:37 AM UTC-8, Tony V wrote:
I can't believe that the topic of MKIV winter maintenance has gotten no

coverage.


Every couple of weeks, I pull the fuselage out of the trailer and blow

air from a hair drier (at the *cool* setting) over the MKIV, but wonder

if this is sufficient to maintain optimal performance. Your expert

advice on this subject is requested.


Tony "6N"

Tony, great idea, but suggest the hair dryer on warm setting to better emulate tropic climes. MKIV's are resilient but susceptable to the winter blues if not flown often enough.

Jp, with sugarplums dancing, we headed for the lab to see if an "inside-the-cockpit" MKIV would be advantageous (and increase sales!). Unfortunately, MKIV's are sensitive little guys and easily confused. With two in close proximity, but in widely diverse environments, both got more confused than the pilot. I'm sure the turbultors would only make matters worse - - definitely not recommended.

Lars, thanks for the kind words, but your "metric model" idea stinks. It's hard enough grabbing the right wrench with two draws full of SAE and Metric stuff. If I came out with a Metric MKIV, next thing you know there'd be clamoring for a Whitworth version and who knows what else.

Having said that, I'll attempt to be reasonable and still keep things simple. I'm ceasing production of the English SAE version of the MKIV. Starting New Year's day, I will only make the metric version - - this should dramatically raise the bar for soaring performance in Europe and 3rd world countries. The SAE version will doubtless become a collector's item and much sought in the USA - - get'um while you still can.

bumper
zz