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 Post subject: Irven H. Culver
PostPosted: Mon Mar 07, 2016 12:20 pm 
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Irven H. Culver
aka: Irv Culver
HG: Culver Twist
He was profoundly involved in early 1970s hang gliding, especially in first meetings and consultant on Volmer Jensen's hang gliders.
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Wiki: https://en.wikipedia.org/wiki/Irv_Culver
Some patents: http://tinyurl.com/SomePatentsIrvenHCulver

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 Post subject: Re: Irven H. Culver
PostPosted: Thu Mar 10, 2016 11:34 pm 
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It was my understanding that he designed the high camber airfoil used on the the Jensen VJ23.

He also designed a safe Rogollo type flex wing for which he made detailed plans and prints and handed them out freely at one of the SCHGA meetings. It had positive dive recovery from any attitude.

I had a set of the plans, which were Ozalid type blue line copy, and they had faded badly. I gave them to Ken DeRussy at the Oregon 40th anniversary meet, in May 2012, because he said he thought he knew a printer who could bring out the contrast and print new copies. At this time (2016) this has not been done. :(

Frank

BTW - I often had to correct other HG pilots who addressed me as "Irv". However, if one goes back far enough in time the Colvers and the Culvers have the same origins in England. He and I talked about that. It was good to know that we shared genes from an ancient ancestor.


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 Post subject: Re: Irven H. Culver
PostPosted: Thu Jan 25, 2018 5:11 pm 
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I now have Irv's plans in digital form and will post them here, in "HG History" and in "General Hang Gliding".

Frank


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 Post subject: Re: Irven H. Culver
PostPosted: Thu Jan 25, 2018 9:58 pm 
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Don Mitchell told me that he had finally understood progressive twist in flying wings from a conversation with Irv Culver in the early 1980s.


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 Post subject: Re: Irven H. Culver
PostPosted: Fri Feb 02, 2018 9:32 am 
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THE STORY:

In December of 1973 Irv Culver, of Lockheed Skunk Works fame, attended our SCHGA meeting in LA and handed out, to anyone who wanted one, blue line prints of a flexwing design that he said would be much safer than the Rogollo type design because it would recover from any dive.

Unfortunately, the old blue line copy had badly faded in my cabinet and was barely readable, when I took it out in May 2012 to take with me to Oregon to give to Ken DeRussy for his hang gliding museum. He said he could get it copied by a printer who could improve the visibility of the text and drawing. Five years later I received the improved copy, 22" x 32" on heavy art paper. But it was still too low contrast to get a good photo copy so I spent hours carefully inking over everything, except Culver's signature and date. I didn't add anything that wasn't there already.

THE DESIGN:

This design had reflexed wing tips that provided the pitch stability, a common practice for swept all wing designs. The sail was also tight approaching the tips which would aid in the downward force there (I used inverted tip ribs on the Skysail).

The sail is also reflexed at the keel and he mentions that if a sail pocket is used it needs to be tapered (to preserve the reflex). Such a sail pocket would allow some shifting right or left of the sail like today's gliders to help with weight shift roll control.

Another innovative aid to dive recovery was a reflexed batten midway on each wing half. The batten was not only reflexed but it could pivot upward aft of the cross spar if the sail in front was starting to collapse (no cambered battens running to the LE in those days). This would provide an opposing force to the collapse of the forward sail.

Another feature ahead of it's time is the hinged cross spar which he said could be used to tension the sail. This is similar to the draw back cabled cross spars we use today.

Then for "safe splat"; skids on the nose and control bar.

The LE's are 3.5" dia., tubing with the sail coming straight back from the top (no pocket) to provide some airfoil camber to increase stall angle of attack.

All in all, this is an amazing design for its time in HG history. Of course I guess that's not surprising for a guy who headed up the Skunk Works at one time.

I never heard of (or saw) anyone building or flying one of these and it would be good to know if someone did. It seems like I remember one of the glider shops saying they were going to build one (possibly Eipper) but I never heard anything more about that.

MY COMMENTS:

This design would not be as good flying wise as today's flexwing hang gliders with their cambered full battens and with the tight sail at the wingtips, while helping the effectiveness of the reflex, would make weight shift roll control more difficult. It's possible that a moveable rudder or drag rudders at the tips would be needed to effectively turn the glider. He does mention a vertical stabilizer but doesn't show one. However, this could be the reason he put dihedral in the design.

Here is a reduced copy of the plan. You will still need to scroll around a bit to see the whole drawing.

Frank Colver

Attachment:
Irv Culver's safe flying flexwing drawing-1973 R.jpg
Irv Culver's safe flying flexwing drawing-1973 R.jpg [ 317.53 KiB | Viewed 5680 times ]


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 Post subject: Re: Irven H. Culver
PostPosted: Sat Feb 03, 2018 12:17 pm 
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I was just looking more carefully at Irv's design. It looks to me that the glider would have two billows on each side since the battens are attached to the cross bar where they pivot through that rectangular restraint. That would cause those battens to be similar to additional mid-span keels ... except they can pivot. But pivoting or not, they constrain the sail to meet the crossbar at that bracket.

It would be interesting to build a model of that design.

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 Post subject: Re: Irven H. Culver
PostPosted: Sun Feb 04, 2018 11:42 pm 
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Yes and as i mentioned, those pivoting battens would help to prevent the sail from collapsing ahead of the crossbar because the lower the angle of attack goes the more force on the rear of the batten to push the front of the sail up. The batten is also reflexed.

It is interesting to think about the two billow sections created.

I wonder if John Heiny would build one and how much he would charge?

Frank


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 Post subject: Re: Irven H. Culver
PostPosted: Sat Oct 31, 2020 12:24 pm 
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Some updates over Irven H. Culver

Died in a Bakersfield, California, hospital. He passed on August 13, 1999, at age 88. That date was not on his Wikipedia page; I just added the date and his full name Irven Harold Culver. Some bot or editor keeps erasing my edits for some reason. I just added three references; maybe that will help stick the data in the article.

When someone obtains his birthdate, let's get such posted into Wikipedia and herein. b: 1911 in Saugus, California
Added: (b. 1911, Saugus, California; d: August 13, 1999, age 88, in Bakersfield, California, hospital; he had been living in Tehachapi, California)

He had been living along in Tehachapi, California
His wife had died earlier. Close couple.
His grandchild reported that Irv had been hurting upon her death. http://fantasylove.tripod.com/culver.html
I have a photo memory of his presence at an early hang gliding meeting.
And with me in a ravine accompanying Volmer Jensen in a flight in the ravine.

Soaring Society's obituary: https://www.ssa.org/FinalGlide?show=blog&id=695

Many of us fly on a "twist distribution" from Irv's calculations! http://www.glide.net.au/on-the-wing4/165-HCP5.pdf

https://oac.cdlib.org/findaid/ark:/1303 ... tire_text/ has physically some papers and photographs regarding Irven Culver. A scholar would visit the physical site and request permission to review the documents.

And Irv, some have noted, might have saved the world as we know it because of his solution on the P-38 for WW II. "Many experts claim the P-38 won WWII." ~ Hall
Some twist comparison talk: HERE

I have been aching to add Irv to a contemporary expert group solving form for energy kite systems, but, alas, he will be invited from a distance to participate. :) :salute:

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