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David Cronk

Postby JoeF » Wed May 08, 2013 1:39 pm

David Cronk, a.k.a., Dave Cronk

Living legend Dave Cronk is the subject of this history thread. Maybe he will join the party herein.

How did he start into hang gliding? And then what? Anyone? All?

Tease image of Dave:
Image
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Re: David Cronk

Postby JoeF » Wed May 08, 2013 1:41 pm

And some further inviting candy from Frank Colver's photo collection on Dave Cronk:
Image
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Re: David Cronk

Postby JoeF » Wed May 08, 2013 1:43 pm

And Quicksilver over Torrance Beach, California, flown by Dave Cronk:
Image
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Re: David Cronk

Postby JoeF » Wed May 08, 2013 1:45 pm

I think Neil Larson holds the following photo of Dave Cronk:
Image

From unknown source:
Image
Last edited by JoeF on Wed May 08, 2013 2:16 pm, edited 1 time in total.
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Re: David Cronk

Postby JoeF » Wed May 08, 2013 1:48 pm

And Neil Larson may be holding this photo also for Eric Larson of Dave Cronk flying a version of the "CronKite"
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Re: David Cronk

Postby JoeF » Wed May 08, 2013 2:12 pm

Be ready for historical errors in Bowers' classic note regarding Lovejoy's Quicksilver where we find Dave Cronk in the story flow, as Dave and Bob were in company with each other. More careful timeline on Quicksilver may be posted someplace, but a book may one day be written just on Quicksilver. Whateever version, Cronk is in the mix.



Here a letter found on the Net which is an incredible source of information recalling the history of Quicksilvers since their beginning... Bonne reading!!! Francois presenting what he found Al Bowers wrote:"The origin of the Quicksilver can be found in Bob Lovejoy's High-Tailer (sp?) design. The High-Tailer and early Quicksilvers all had a 4 foot chord and 30 ft span. IIRC, the High-Tailer had swept twin vertical fins that started at the control bar, passed the trailing edge of the wing (mostly the same as the original Quicksilver) and ended somewhat above the wing. A horizontal tail capped the two verticals off. Again, IIRC, the design had some directional control problems (it would almost always fly straight ahead, very stable), and the control bar/vertical/horizontal arrangement was somewhat flexible. It was a four sides parallelogram structure, so had little inherent stiffness.

The original Quicksilver (later called the "A" model) was built from the High-Tailer. The twin verticals and high mounted horizontal were replaced with an "A" frame off the trailing edge of the wing, back to a fixed horizontal and a "C" frame rudder (no fixed fin). As the trailing edge of the "C" frame was unsupported, the rudder distorted a
lot, but it was very effective at directional control, and the glider responded through dihedral effect (Cl-beta). The "C" frame rudder got replaced with a different "D" frame rudder which solved the distortion problem.

I can't recall if it was Dave Cronk or Bob Lovejoy (or one of the other Eipper guys) that first thought to load test the Quicksilver. in any case, the failure occured at very low G (again, fuzzy memory, IIRC it was about 3.5 Gs), between the trailing edge flying wire and the center section. Also, the single upper wire to the tail didn't
provide much lateral support to the rudder loads. These led to the to the first improved model of the Quicksilver, called the "B." A wire was added from the control bar to the trailing edge of the wing (increasing the G limit to about 5.5), the "A" frame of the tail group gained a straight section between the horizontal and the rudder
(making a square "U" section) and a second upper wire was added from the kingpost to the tail (one wire to each end of the squared-off "U"). The result was the best of the early model Quicksilvers, as a flying machine and structurally.

The next Quicksilver improvement was increasing the span (from 30 ft to 32 ft), increasing the chord (from 4 ft to 5 ft), and enlarging the tail (the rudder lost it's characteristic "swept" leading edge). The wing also gained square tips (cf the "tapered" tip of the HT/QsA/QsB) to make the Quicksilver C model. This model also had a much reduced camber of the airfoil (the High-Tailer through Quicksilver B model had a "670-15" airfoil, which was made by bending a thin aluminum tube for one-half of it's length over a 670-15 car tire; it was about 12% camber; the C and later models had about an 8% camber, again, IIRC). This was the same model that Jack Schroeder and
Dave Cronk flew in the (much delayed) 1974 Nationals (I believe that Bill Liscomb was still flying an older B model at that meet). The C model seemed to be the most prolific of the hang glider models.

There after, there were some experimental models meant to improve performance. And here the letter designations get very fuzzy. All HT and Qs models to this point had a tube for a trailing edge. I don't know if it was Cronk, or Lovejoy, or one of the other Eipper guys, but an experiment was made of moving the trailing edge spar forward, and
making a thin trailing edge of fabric only. The leading edge pocket was also made VERY large (maybe about 50% of the chord). When I talked to Dave Cronk about this, he said it ruined the stall characteristics (very sharp and abrupt), but penetration went WAY up. this may have been called a "D" model. But I do know that later still
the leading edge pocket was made even larger to enclose the leading AND trailing edge spars (about 80%) making a double surface airfoil. This model (the "E"?) was a rocket in Cronk's hands, though I don't think any were sold to customers. This would have been about the time of the first Fledge IIBs appearing in California with a similar pocket enclosing the spars (I don't know who did it first, or who copied who, or even if both came up with it independently of each other; I would guess the last option being the most probable).

There were some competitors out there as well. Conquest was one (very high level of fit and finsh on these). Another (much less successful) was the Condor. The Qs was certainly the "performance" machine of the
day until surpassed by Fledges. And the Rogallos started improving in this same time frame, Mike Riggs' Seagull V, Rich Finley's Windlord, Tom Peghiny's Peregrine, and Roy Haggard's (unbelievably radical) Dragonfly. Once you compute the transport and set-up hassles against the performance gain, the flexwings were more than competitive to most buyers.

It's funny how things have come full circle. Now with Exxtasy, Ixbo, ATOS, and Millenium rigid wings easy to set-up and almost as easy to transport as flexwings, we're nearly back to parity again (complexity and weight still favor the modern flexwing). And I still get out my plans for the Quicksilver A/B once in a while and look at them. I
have many fond memories watching Pat Conniry and Dave Cronk flying their Quicksilvers at Torrance Beach. And helping my friend, Sandy Klevans, set-up, launch and fly his Quicksilver...

Al Bowers "
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Re: David Cronk

Postby JoeF » Wed May 08, 2013 2:20 pm

Neil Larson covers well some items of old that hold part of the Dave Cronk story:
http://ushawks.org/forum/viewtopic.php?f=18&t=629

Dave Cronk and another hang gliding pioneer Roy Haggard went on to do neat engineering at Vertigo, Inc. that sold to HDT Global company.
As of April 1, 2009, Vertigo, Inc. was acquired by Hunter Defense Technologies, Inc. ~ SOURCE has interesting description.


http://www.hdtglobal.com/products/parac ... -hi-glide/
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Re: David Cronk

Postby JoeF » Thu Feb 25, 2016 1:12 pm

Some study of the above photo:

CLICK PHOTO TO GET FULL IMAGE.

CronkSeat001.png
CronkSeat001.png (127.61 KiB) Viewed 2228 times


CronkHGclipstudy.JPG
CronkHGclipstudy.JPG (81.49 KiB) Viewed 2228 times
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Re: David Cronk

Postby Frank Colver » Tue Mar 01, 2016 9:24 am

Dave has told me that he is coming to the 45th Otto meet anniversary celebration at Dockweiler Beach on May 22nd. :thumbup:

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Re: David Cronk

Postby Bob Kuczewski » Sat Mar 05, 2016 3:36 pm

fcolver wrote:Dave has told me that he is coming to the 45th Otto meet anniversary celebration at Dockweiler Beach on May 22nd. :thumbup:

Frank Colver


Wow!!!

That's super Frank!!!!!

:thumbup: :thumbup: :thumbup: :thumbup: :thumbup: :thumbup: :thumbup: :thumbup: :thumbup: :thumbup:
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