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#21
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Primary Glider Drawings
On Oct 4, 11:35*am, Tech Support wrote:
Veeduber What would it take to convert a primary into a basic soaring machine (35+ to 1)? ----------------------------------------------------------------------- Dear John, I don't know. But I DO know you're comparing apples to orangutans :-) The subject is Primary Gliders. Their poor glide ratio -- typically about 8:1 -- is by DESIGN. That is what's needed to fulfill their mission, which is to expose a fledgling pilot to 3- axis controls and introduce them to the mechanics of landing. You would probably find the syllabus used by early flight-training programs to be of considerable interest. -R.S.Hoover |
#22
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Primary Glider Drawings
On Mon, 06 Oct 2008 13:34:46 +1000, Michael Henry
wrote: Tech Support wrote: Sure nice to have so many comments that are mostly relevant to thread and beginners glider. Hear hear!!! I was thinking about a wing that would support a decently high L/D and a simple enclosure around pilot to reduce his flat plate drag, built on a primary glider fuselage frame. Build time 500 hours or less and transportable home. I'm in my high 80's and don't have 'time' left to build a 10 year project. What you're describing is the Compact 110 (defunct): http://home.ptd.net/~jlbaker/compact110.htm ...or the ULF-1: http://www.eel.de/english/ulf-1_description.htm ************************************************** *********************** Michael In the ball park of what I was talking about. Will take to bed with me and look and think on data of those who have gone before me. Tnx Big John |
#23
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Primary Glider Drawings
Which also linked to . . .
the Sandlin Bug (Basic Ultralight Glider) http://home.att.net/~m--sandlin/bug.htm |
#24
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Primary Glider Drawings
Perhaps nothing except the basic fundamental understanding of WHAT SNIP
MEANS. Veeduber What would it take to convert a primary into a basic soaring machine (35+ to 1)?. |
#25
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Primary Glider Drawings
Perhaps nothing except the basic fundamental understanding of WHAT SNIP
MEANS. -- "It is the mark of an educated mind to be able to entertain a thought without accepting it." --Aristotle |
#26
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Primary Glider Drawings
Perhaps nothing except the basic fundamental understanding of WHAT SNIP
MEANS. 35 to 1 and open cockpit don't coexist. Light weigh does not improve glider ratio. In order to get anything near 35 to 1 in a homebuilt you must build something like my Schreder HP-14. (http://www.soaridaho.com/Schreder/HP-14/N990/N990.html) Wayne http://www.soaridaho.com/Schreder |
#27
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Primary Glider Drawings
"Bill Daniels" bildan@comcast-dot-net wrote in message . .. "Peter Dohm" wrote in message news "Bill Daniels" bildan@comcast-dot-net wrote in message ... Weight in a glider is a double edged sword and never simple. In fact, it can add to L/D. For example, my Nimbus 2C has an L/D max of 47:1 at 1000 pounds and 49:1 at 1433 pounds. The difference in L/D max is due to a higher Reynolds number at the higher best L/D airspeed with the higher weight. That extra weight is ballast water in wing tanks. In any but the weakest weather, that ballast dramatically increases performance. This is shown most clearly at 100 Kts where the 1000lb GW L/D is 22.3:1 and the 1433lb GW L/D is 31:1. But, of course, structural weight is not jetisonable as is water ballast. But that wasn't really my point. It was that good engineering directed at crashworthiness is an investment in design excellence which is also likely, but not assuredly, to increase performance. At least the two aren't mutually exclusive. That's particularly true when the cockpit structure is molded carbon/Kevlar which can be of any shape and might as well be the best aerodynamic one. As near as I can determine, the latest crashworthy cockpits don't weight any more than the old ones and they are actually lighter than steel tubes. Bill D I believe that you are correct in this, and that a kevlar capsule is a good investment. I have not researched the matter and could be wrong; but I strongly suspect that a many, if not most, of the dissabling leg injuries in the old primary gliders involved easily deflected collisions rather than "hitting a wall". Peter Most likely. I know of one accident in a Schweizer 1-26A (tube and fabric) where an off field landing resulted in a stick coming through the nose fabric severing a leg artery. The pilot bled to death before he could get out of the cockpit. I guess you can tell that I have no love of tube and fabric gliders. Bill D This is an extreme case of the same problem that concerns me: Intrusion of "brush" in the course of an off field landing. Obviously, in this particular case, the shrubbery involved must have appeared to be soft enough to be deflected by the tube and fabric structure; but the general problem must have been nearly epidemic with the completely open seating areas of the primary gliders. Nothing can ever eliminate the occasional encounter with a stronger and/or sharper than expected solid object; but a slightly flexible kevlar based composite capsule could be a great improvement. The March racing cars used a kevlar based capsule system about 30 years ago with considerable success--although their earliest attempts were heavy and less than competitive, and some developement was required. AFAIK, kevlar has a high tensile strenght, but does not bond to the resins in which it might be encapslated. Therefore, it will extrude under load. That makes it a good to excellent material for safety structures and a generally poor material for heavy load bearing structures. Peter |
#28
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Primary Glider Drawings
"Bill Daniels" bildan@comcast-dot-net wrote in message . .. snippage Let me throw in a slightly controversial idea. Low L/D, taken in isolation, offers no benefit whatsoever in a trainer. In fact, higher L/D is a safety feature that gets an inexperienced pilot back to the runway after a bad judgement call. In spite of this, there is an instinctive reaction among most glider pilots to inversely relate L/D and safe handling qualities. In a soaring environment, I think you're right. But that is not the environment veeduber is proposing. He's proposing a cheap "hook" to capture the attention of teenagers. Teenagers who might not have two grand or so to shell out for glider lessons, but might well have some sweat equity to invest in building something that actually flies. For this target group, it has to be something that goes together pretty quickly. If it takes a thousand hours of construction, it isn't likely to get started, let alone completed. For veeduber's purposes, I think he will have achieved part of his goal if it gets even half built. Kids will be using their heads and their hands to solve problems. For this environment, it's not performance that counts, but energy. With a fairly draggy airframe, you can limit the amount of energy available to damage the pilot. Somewhere on Mike Sandlin's site, he remarks on this, limiting the energy by how far up the training hill you drag the glider. snippage "Primary gliders" were an expedient developed in an environment that lacked adequate two-seat trainers. They were abandoned with great relief as soon as usable 2-seater trainers became available. Today, there are a great number of excellent 2-seat trainers and qualified instructors. Only a fool would try to learn flying in a "Primary". I can't entirely disagree, but people learn to fly hang gliders, with similar performance limitations, every day. There is some tandem instruction available, and that's good. But in general, it's not the instruction process that kills people. A two-place primary under 155 lbs might sneak in under USHGPA's tandem exemption, here in the U.S. Maybe. Tim Ward |
#29
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Primary Glider Drawings
On Sun, 5 Oct 2008 21:43:49 -0700 (PDT), "
wrote: On Oct 4, 11:35*am, Tech Support wrote: Veeduber What would it take to convert a primary into a basic soaring machine (35+ to 1)? ----------------------------------------------------------------------- Dear John, I don't know. But I DO know you're comparing apples to orangutans :-) The subject is Primary Gliders. Their poor glide ratio -- typically about 8:1 -- is by DESIGN. That is what's needed to fulfill their mission, which is to expose a fledgling pilot to 3- axis controls and introduce them to the mechanics of landing. You would probably find the syllabus used by early flight-training programs to be of considerable interest. -R.S.Hoover ************************************************** *************************** Understand ur comments but intent of my original post was to get some ideas on size and airfoil of a wing attached to a Primary Glider fuselage with a minimual enclosure around pilot that would permit some basic soaring. All on the cheap and rapid build. Lots of ideas have been expessed that shot down some of my original ideas and others that have given me clues on how to meet my original objectives. Tnx to all. Y'all have a nice day and hope you get good news on ur health. Big John |
#30
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Primary Glider Drawings
"Tim Ward" wrote in message ... "Bill Daniels" bildan@comcast-dot-net wrote in message . .. snippage Let me throw in a slightly controversial idea. Low L/D, taken in isolation, offers no benefit whatsoever in a trainer. In fact, higher L/D is a safety feature that gets an inexperienced pilot back to the runway after a bad judgement call. In spite of this, there is an instinctive reaction among most glider pilots to inversely relate L/D and safe handling qualities. In a soaring environment, I think you're right. But that is not the environment veeduber is proposing. He's proposing a cheap "hook" to capture the attention of teenagers. Teenagers who might not have two grand or so to shell out for glider lessons, but might well have some sweat equity to invest in building something that actually flies. For this target group, it has to be something that goes together pretty quickly. If it takes a thousand hours of construction, it isn't likely to get started, let alone completed. For veeduber's purposes, I think he will have achieved part of his goal if it gets even half built. Kids will be using their heads and their hands to solve problems. For this environment, it's not performance that counts, but energy. With a fairly draggy airframe, you can limit the amount of energy available to damage the pilot. Somewhere on Mike Sandlin's site, he remarks on this, limiting the energy by how far up the training hill you drag the glider. snippage "Primary gliders" were an expedient developed in an environment that lacked adequate two-seat trainers. They were abandoned with great relief as soon as usable 2-seater trainers became available. Today, there are a great number of excellent 2-seat trainers and qualified instructors. Only a fool would try to learn flying in a "Primary". I can't entirely disagree, but people learn to fly hang gliders, with similar performance limitations, every day. There is some tandem instruction available, and that's good. But in general, it's not the instruction process that kills people. A two-place primary under 155 lbs might sneak in under USHGPA's tandem exemption, here in the U.S. Maybe. Tim Ward OK, but don't build one, buy one. There are a few around. Take it out to a hill or dry lake and try flying it. This is also done on occasion. What you won't do is fly it two days in a row. One day will convince just about anybody that primaries are a really bad idea. Primary gliders are a huge amount of work to fly - expecially if you use the traditional bungee launch method which is really the only safe way to fly one. Aero tow or winch launch is terrfying in a primary - although this is also done on occasion. (But rarely twice in a lifetime by the same pilot.) To fly one as it was intended, you need a huge grassy slope that is slightly shallower than the glide ratio of the primary. The bungee launch will get the glider to just above stall speed a couple of feet above the ground. If the pilot can hold the exact best L/D airspeed and keep it perfectly coordinated, he will be rewarded with a glide of a couple of hundred yards - maybe 30 seconds of airtime. If he deviates in any way from perfection, the glider will quickly settle into the grass. If you have 15 - 20 knots of wind up the slope, the instructor can run along side shouting instructions. Then everybody gets to haul it back up the slope. All this exercise will achieve about ten flights a day but it WILL get you in shape. See: http://www.youtube.com/watch?v=B6-EeuEi-KY See: http://www.youtube.com/watch?v=BgBJ52L-Rao I have a better idea that fits well with the homebuilder ethic. Build a winch. See: http://groups.yahoo.com/group/winchengineer/files/ The really big cost in learning to fly gliders is aero tow. It averages about $50 for a 15 minute flight. Add instructor and glider rental and it's not unusual to see $250 and hour. Multi-engine training is cheaper. Winches can reduce launch costs to $5 and glider training rates to ~$50/hr. Certified glider trainers aren't expensive if you can keep the utilization high. And I GUARANTEE it attracts young people. You can't buy a ride like that at Disneyland. See: http://www.youtube.com/watch?v=UOp_EsplxDM Bill Daniels |
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