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#11
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ASG-29/ASW-27 wing refinish
Here is my hypothesis.
The SH lays up there spar cap into the wing skin, versus the AS factory, which built there spar complete and separate from the wing structure. This requires a different joining technique and application of epoxy slurry. In the later case the spar is set into the lower wing skin in a controlled fashion, hence using less epoxy. Before the top skin is set into place, dams out of beaded foam are built, they are a bid higher then the insight of the skin when joint. The spar cap with the dams in place is now filled with an epoxy mixture. The shape of the mixture has a little inverted V shape like a roof but shallower. This allows for the epoxy to make contact in the centre first and pushes it out ward. At the same time the foam dam gets pushed out of the way to allow for a bead to be form. Due to the tolerances between the height of the spar cap and the inner wing skin, there is more epoxy used then at the bottom joint, hence more shrinking of the top skin occurs. That does not explain the fact I did not have shrinkage on my ASW24 wing in 16 years, unless, I venture to say, after 1999 a lot of experience workers retired. I must assume that the tolerance were also better before that time and better epoxies were used. There is always a drive to keep the cost down. I always like the idea of building the spar separate. They got it right once they should get it right again. Udo Stewart Kissel wrote: At 20:31 05 November 2006, Doug Haluza wrote: I was at the Schleicher factory last week, and asked about this. They did purchase new higher temperature curing ovens to try to solve this problem, but it has not helped much. It seems that it just has to run its course over time. They did say that the shrinkage seems to be a one-time thing, and it is complete after about 4 years. Hmmm, I take it they have examined the construction of this wing vs other wings that don't shrink and get spar bumps. Far be it for me to question Teutonic marketing rationale...but spending $100k+ on a glider that is going to have its performance suffer as the wing shrinks, then get to spend another $20k+ on reprofile and refinish....am I missing something here? |
#12
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ASG-29/ASW-27 wing refinish
Udo:
The DG website has a diagram of 4 different spar construction methods: http://www.dg-flugzeugbau.de/holm-aufbau-e.html Do I understand you to say that SH uses #3, and AS uses #1? DG says that they use #4, so that would mean that each of the major manufacturers uses a different method. Udo wrote: Here is my hypothesis. The SH lays up there spar cap into the wing skin, versus the AS factory, which built there spar complete and separate from the wing structure. This requires a different joining technique and application of epoxy slurry. In the later case the spar is set into the lower wing skin in a controlled fashion, hence using less epoxy. Before the top skin is set into place, dams out of beaded foam are built, they are a bid higher then the insight of the skin when joint. The spar cap with the dams in place is now filled with an epoxy mixture. The shape of the mixture has a little inverted V shape like a roof but shallower. This allows for the epoxy to make contact in the centre first and pushes it out ward. At the same time the foam dam gets pushed out of the way to allow for a bead to be form. Due to the tolerances between the height of the spar cap and the inner wing skin, there is more epoxy used then at the bottom joint, hence more shrinking of the top skin occurs. |
#13
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ASG-29/ASW-27 wing refinish
Greg ,
# 3 is a simplified version of the SH approach. The web has a pocket along the spar in which the web slides upon closure.The total amount of epoxy is reduced, and the shrinking acts in a different direction, hence less shrinking in the vertical. In any case that is my take on it. http://www.alexander-schleicher.de/englisch/e_main.htm Udo Greg Arnold wrote: Udo: The DG website has a diagram of 4 different spar construction methods: http://www.dg-flugzeugbau.de/holm-aufbau-e.html Do I understand you to say that SH uses #3, and AS uses #1? DG says that they use #4, so that would mean that each of the major manufacturers uses a different method. Udo wrote: Here is my hypothesis. The SH lays up there spar cap into the wing skin, versus the AS factory, which built there spar complete and separate from the wing structure. This requires a different joining technique and application of epoxy slurry. In the later case the spar is set into the lower wing skin in a controlled fashion, hence using less epoxy. Before the top skin is set into place, dams out of beaded foam are built, they are a bid higher then the insight of the skin when joint. The spar cap with the dams in place is now filled with an epoxy mixture. The shape of the mixture has a little inverted V shape like a roof but shallower. This allows for the epoxy to make contact in the centre first and pushes it out ward. At the same time the foam dam gets pushed out of the way to allow for a bead to be form. Due to the tolerances between the height of the spar cap and the inner wing skin, there is more epoxy used then at the bottom joint, hence more shrinking of the top skin occurs. |
#14
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ASG-29/ASW-27 wing refinish
I sure am impressed with DG as a company! Many safety products, GREAT web site, newsletters...etc. No, I do not own a DG glider, nor do I have one on order. However, as soon as they make a competive glider that I fit into (i.e., LS 10 with new cockpit I will buy it!). I just wish the other manufacturers would make NOAH's, something to keep spoilers from opening, and stall warning like DG does. On Nov 5, 6:43 pm, Greg Arnold wrote: Udo: The DG website has a diagram of 4 different spar construction methods: http://www.dg-flugzeugbau.de/holm-aufbau-e.html Do I understand you to say that SH uses #3, and AS uses #1? DG says that they use #4, so that would mean that each of the major manufacturers uses a different method. Udo wrote: Here is my hypothesis. The SH lays up there spar cap into the wing skin, versus the AS factory, which built there spar complete and separate from the wing structure. This requires a different joining technique and application of epoxy slurry. In the later case the spar is set into the lower wing skin in a controlled fashion, hence using less epoxy. Before the top skin is set into place, dams out of beaded foam are built, they are a bid higher then the insight of the skin when joint. The spar cap with the dams in place is now filled with an epoxy mixture. The shape of the mixture has a little inverted V shape like a roof but shallower. This allows for the epoxy to make contact in the centre first and pushes it out ward. At the same time the foam dam gets pushed out of the way to allow for a bead to be form. Due to the tolerances between the height of the spar cap and the inner wing skin, there is more epoxy used then at the bottom joint, hence more shrinking of the top skin occurs. |
#15
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ASG-29/ASW-27 wing refinish
Roger wrote:
I sure am impressed with DG as a company! Many safety products, GREAT web site, newsletters...etc. No, I do not own a DG glider, nor do I have one on order. However, as soon as they make a competive glider that I fit into (i.e., LS 10 with new cockpit I will buy it!). I just wish the other manufacturers would make NOAH's, something to keep spoilers from opening, and stall warning like DG does. Schleicher does some nice things, too: Starting with the ASW 27, the caps on unlocked spoilers tip up in back, preventing the airflow from sucking open the spoilers. They lead the way to safer cockpit construction, and still have a more crash resistant cockpit than the DG models. For me, that is more important than the better visibility the lower sidewalls of the DG provide, and the availability of the NOAH system. My belief is I will be more likely to crash into the ground than have a mid-air collision where G loads pin me inside the glider, or to avoid the collision because of the better visibility. Ever since the ASW 20, their flapped gliders have had a landing flap position that puts the flaps at 40 degrees positive, while raisig the ailerons to a slight negative angle. This gives a high drag, high lift configuration with no tendency to stall the tips, allowing a steeper, slower approach and landing than gliders where the landing flap is more like 20 degrees. I do like the idea of DG's stall warning, and hope owners with it will report on it's usefulness. Their web site is very good, and I visit it more often than Schleicher's. -- Eric Greenwell - Washington State, USA Change "netto" to "net" to email me directly "Transponders in Sailplanes" on the Soaring Safety Foundation website www.soaringsafety.org/prevention/articles.html "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
#16
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ASG-29/ASW-27 wing refinish
At 03:54 08 November 2006, Eric Greenwell wrote:
Roger wrote: I sure am impressed with DG as a company! Many safety products, GREAT web site, newsletters...etc. No, I do not own a DG glider, nor do I have one on order. However, as soon as they make a competive glider that I fit into (i.e., LS 10 with new cockpit I will buy it!). I just wish the other manufacturers would make NOAH's, something to keep spoilers from opening, and stall warning like DG does. Schleicher does some nice things, too: Starting with the ASW 27, the caps on unlocked spoilers tip up in back, preventing the airflow from sucking open the spoilers. They lead the way to safer cockpit construction, and still have a more crash resistant cockpit than the DG models. For me, that is more important than the better visibility the lower sidewalls of the DG provide, and the availability of the NOAH system. My belief is I will be more likely to crash into the ground than have a mid-air collision where G loads pin me inside the glider, or to avoid the collision because of the better visibility. Ever since the ASW 20, their flapped gliders have had a landing flap position that puts the flaps at 40 degrees positive, while raisig the ailerons to a slight negative angle. This gives a high drag, high lift configuration with no tendency to stall the tips, allowing a steeper, slower approach and landing than gliders where the landing flap is more like 20 degrees. I do like the idea of DG's stall warning, and hope owners with it will report on it's usefulness. Their web site is very good, and I visit it more often than Schleicher's. -- Eric Greenwell - Washington State, USA Change 'netto' to 'net' to email me directly 'Transponders in Sailplanes' on the Soaring Safety Foundation website www.soaringsafety.org/prevention/articles.html 'A Guide to Self-launching Sailplane Operation' at www.motorglider.org In your many trips to our DG web site you may have missed this section that deals with their extensive work on a better safety cockpit. http://www.dg-flugzeugbau.de/index-e.html While other manufactures have been content with building what looks strong enough DG has actually participated in crash testing. As a result of this testing they offer the consummate safety cockpit as an option on the 800 series and as standard on the 1000. If you counting on higher frame rails for protection you may also want to read this. http://www.dg-flugzeugbau.de/index-e.html |
#17
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ASG-29/ASW-27 wing refinish
At 13:42 08 November 2006, Gary Evans wrote:
At 03:54 08 November 2006, Eric Greenwell wrote: Roger wrote: I sure am impressed with DG as a company! Many safety products, GREAT web site, newsletters...etc. No, I do not own a DG glider, nor do I have one on order. However, as soon as they make a competive glider that I fit into (i.e., LS 10 with new cockpit I will buy it!). I just wish the other manufacturers would make NOAH's, something to keep spoilers from opening, and stall warning like DG does. Schleicher does some nice things, too: Starting with the ASW 27, the caps on unlocked spoilers tip up in back, preventing the airflow from sucking open the spoilers. They lead the way to safer cockpit construction, and still have a more crash resistant cockpit than the DG models. For me, that is more important than the better visibility the lower sidewalls of the DG provide, and the availability of the NOAH system. My belief is I will be more likely to crash into the ground than have a mid-air collision where G loads pin me inside the glider, or to avoid the collision because of the better visibility. Ever since the ASW 20, their flapped gliders have had a landing flap position that puts the flaps at 40 degrees positive, while raisig the ailerons to a slight negative angle. This gives a high drag, high lift configuration with no tendency to stall the tips, allowing a steeper, slower approach and landing than gliders where the landing flap is more like 20 degrees. I do like the idea of DG's stall warning, and hope owners with it will report on it's usefulness. Their web site is very good, and I visit it more often than Schleicher's. -- Eric Greenwell - Washington State, USA Change 'netto' to 'net' to email me directly 'Transponders in Sailplanes' on the Soaring Safety Foundation website www.soaringsafety.org/prevention/articles.html 'A Guide to Self-launching Sailplane Operation' at www.motorglider.org In your many trips to our DG web site you may have missed this section that deals with their extensive work on a better safety cockpit. http://www.dg-flugzeugbau.de/index-e.html While other manufactures have been content with building what looks strong enough DG has actually participated in crash testing. As a result of this testing they offer the consummate safety cockpit as an option on the 800 series and as standard on the 1000. If you counting on higher frame rails for protection you may also want to read this. http://www.dg-flugzeugbau.de/index-e.html Hmmm, sorry for some reason my original links only take you to the DG web site opening page. If I paste the link it works but it doesn't from clicking in the post. Anyone know what I'm doing wrong? From the opening page click on DG-808 and under DG-808 General find 'The Consummate Safety Cockpit'. |
#18
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ASG-29/ASW-27 wing refinish
Gary, Depending on your newsreader and computer, at, for instance, the DG808 page, hover your mouse over the "The Consummate Safety Cockpit" and right-click or option-click the link. Choose "Copy Link Location" or some such from the options. Then you can paste that link into the email. Larry "01" USA Hmmm, sorry for some reason my original links only take you to the DG web site opening page. If I paste the link it works but it doesn't from clicking in the post. Anyone know what I'm doing wrong? From the opening page click on DG-808 and under DG-808 General find 'The Consummate Safety Cockpit'. |
#19
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ASG-29/ASW-27 wing refinish
The Safety cockpit is now standard in the DG 808 as well. They where
amazed that not many new owners where taking the safety cockpit option. One reason given ( apart from the cost ) was the width of the seatpan was narrower when it was installed.They improved the design and also made it part of the base glider price. So same sized cockpit as before and stronger to boot. Paul |
#20
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ASG-29/ASW-27 wing refinish
Gary Evans wrote:
While other manufactures have been content with building what looks strong enough DG has actually participated in crash testing. This is not correct. Gerhard Waibel won an OSTIV prize for his work in cockpit safety about 20 years ago. Gerhard's ideas, and the ASW 24 cockpit (the first of the really crashworthy cockpits) was based on extensive testing by a group at MIT, and others. In the years since then, Schleicher continues to monitor the performance of their designs by examining their gliders that are involved in crashes, either when they are brought to their shop for repair, or using pictures sent to them by the mechanics repairing the glider elsewhere. An advantage of this approach is it shows what happens in an actual crash. As a result of this testing they offer the consummate safety cockpit as an option on the 800 series and as standard on the 1000. I have been impressed with DG's improvements in safety over the years, but their single seaters cockpits still do not match what Schleicher has done. This page on the DG website shows that this view is shared by others (go to the "Safety Cockpit" row): http://www.dgflugzeugbau.de/ash-dg-ventus-e.html These differences are not surprising. The low sides and open nose of the DG single seater cockpit pose a difficult engineering problem for the designer, compared to the greater enclosure of the Schleicher cockpits. I'm not suggesting that the DG cockpit is unsafe or inadequate, but only that it does not match what Schleicher has done. A prospective owner should consider the value of that protection along with the other features of the gliders he is considering; for example, the lower sides of the DG cockpit (particularly if the NOAH option is selected) should make baling out easier than from a Schleicher cockpit. If you counting on higher frame rails for protection you may also want to read this. http://www.dg-flugzeugbau.de/index-e.html I was unable to find this reference, but I would like to read it. -- Eric Greenwell - Washington State, USA Change "netto" to "net" to email me directly "Transponders in Sailplanes" on the Soaring Safety Foundation website www.soaringsafety.org/prevention/articles.html "A Guide to Self-launching Sailplane Operation" at www.motorglider.org |
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