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#91
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My September 2017 visit to GP Gliders
2G wrote on 8/18/2020 10:10 PM:
On Tuesday, August 18, 2020 at 7:26:51 PM UTC-7, Eric Greenwell wrote: 2G wrote on 8/18/2020 3:07 PM: On Tuesday, August 18, 2020 at 1:49:35 PM UTC-7, andy l wrote: GP doesn't just claim "lower weight," but "far lower weight" than other gliders, but w/o any evidence to support this claim. The only real evidence I have seen is that Sebastian Kawa was very unhappy with the glider GP delivered to him and switched gliders at the last minute. Kawa also had a propulsion failure while flying a GP-14 in Italy, yet GP gliders makes this bizarre claim on their website: "The motor can be deployed and running at full power within five seconds providing confidence in the event of when a ‘low save’ is on the cards." I guess Sebastian didn't get the memo on how reliable GP propulsion systems are. You are certainly welcome to accept all of GP's claims w/o any evidence, but I won't. And I certainly wouldn't send them six figures in cash for it. The motor can indeed be deployed and running in 5 seconds, and with considerable confidence. The original mechanical mast switch, external to the mast, was deemed too vulnerable to damage after Kawa's accident with the prototype glider. It was replaced with two redundant, buried solid state switches to prevent a repeat of the problem. You've had a similar switch failure on your Schleicher glider, but were lucky that it eventually worked after repeated attempts. Other Schleicher owners have also experienced mast switch failures, but Schleicher still uses the external mechanical switches. Maybe they didn't get the memo? -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 I DIDN'T have a similar failure - in fact, I had no failure at all. The switch was in perfect working order, the only explanation was flying a little too fast for the mast to deploy fully. In any event, this has NOTHING to do with the outrageous claims being made by GP Gliders. No one should depend upon propulsion to start in an emergency. My main point was we shouldn't judge a product on a failure in a prototype a couple years ago, as there have been many changes made since then. My apologies - I did not realize you'd concluded it was pilot error that caused your problem; even so, other pilots have had failed switches, including myself. For the particular failure I had, Schleicher did respond by switching to more water resistant switches. This is off topic, but since I fly a Schleicher glider with the same engine system, how fast were you flying when the problem occurred? -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
#92
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My September 2017 visit to GP Gliders
jld wrote on 8/19/2020 3:01 AM:
Certification requirements have forced manufacturers to significantly increase the weight of their gliders (e.g. cockpit protection). Because more recent airfoils are tolerant to higher WL, this has not been a significant issue, except for the fact MTM goes up and self launchers need more power! By using experimental in US and UL in EU, GP has more design freedom. For example, not proposing a heavy 16G cockpit but a rescue parachute instead! Do you know how much the "16G cockpit" adds in weight, compared to the cockpit requirement of a glider with a rescue parachute? Or asking another way: is a glider designed to the "16G cockpit" standard heavier than one designed with a rescue parachute (and including the parachute weight)? -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 |
#93
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My September 2017 visit to GP Gliders
On Wednesday, 19 August 2020 at 11:02:00 UTC+1, jld wrote:
""GP doesn't just claim "lower weight," but "far lower weight" than other gliders, but w/o any evidence to support this claim"" The evidences are in the design and certification choices. GP15 is about same empty weight as the H301 which was a fiberglass ship, so there is nothing new. Carbon now allows to use lower relative thickness airfoil and higher aspect ratio wings to get to higher performance. Certification requirements have forced manufacturers to significantly increase the weight of their gliders (e.g. cockpit protection). Because more recent airfoils are tolerant to higher WL, this has not been a significant issue, except for the fact MTM goes up and self launchers need more power! By using experimental in US and UL in EU, GP has more design freedom. For example, not proposing a heavy 16G cockpit but a rescue parachute instead! You suggested this company has better materials and design techniques than its rivals. It's somewhat fatuous to then introduce a 55+ year old design into the discussion. If you were giving us this somewhat patronising explanation in 1980, you might have a point. Schempp-Hirth were able to use knowledge gained from prototype wind turbine blades to build an all carbon wing for the Mini Nimbus. I said to the agent in our country why don't they produce a new design with thinner and higher aspect ratio wings. I'm sure they had the idea themselves without any help from me Certification standards aren't just random paperwork for the fun of it You laud the idea of reducing cockpit strength. Oh great. I've seen the floppy cockpit sides on another recent lightweight glider. A friend held both side rails and moved them an inch or two in and out; he might have been able to snap or peel something apart with a bit more effort. Another glider type a few years ago achieved the distinction of being banned from operating at one club, and I can't say I'm surprised, given what a different friend found Another place to try to save weight is on control surfaces. There's geared extra payback from reducing mass balances. For the rudder this can get extra gearing again for the minimum cockpit weight. Is mass balancing going to be an area where this glider will save weight? How fast will it go? Another post above mentions wings drooping fore and aft of the spar due to insufficient curing. I hadn't heard that before, but sorry, if true this just sounds amateurish. The rivals post cure in the moulds overnight, carefully controlled and logged temperature and time. Some parts of the process don't have shortcuts. .. |
#94
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My September 2017 visit to GP Gliders
On Wednesday, 19 August 2020 at 16:29:13 UTC+3, Eric Greenwell wrote:
jld wrote on 8/19/2020 3:01 AM: Do you know how much the "16G cockpit" adds in weight, compared to the cockpit requirement of a glider with a rescue parachute? Or asking another way: is a glider designed to the "16G cockpit" standard heavier than one designed with a rescue parachute (and including the parachute weight)? -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "A Guide to Self-Launching Sailplane Operation" https://sites.google.com/site/motorg...ad-the-guide-1 I asked few years ago german glider producer CEO (you quess) about future of std. class. He said that they could design and build better std. class ship than previous generation (they all are from late 90s), but performance gain would be offset by requirement to build stronger fuselage than previous gen. glider that would weigh a lot more. |
#95
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My September 2017 visit to GP Gliders
"No they don't. You have a 470kg glider in UL class that has MTOM of 472,5 kg (if national regs allow). Now EASA says that you can design and build an UL aircraft that has MTOM of 600kg (if national regs allow). The 470 kg GP fits into that weight limit perfectly"
Maybe I was not clear enough and we fail to communicate. With new EASA limit (i.e. 600kg) the national limitS are being updated. If you check updated UL national regulations you will discover that there is more than MTOM being updated and influencing your design (Empty weight, minimum Payload, Vso, etc.). Controlling the empty weight is certainly on the critical path to meet a lot of the requirements. |
#96
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My September 2017 visit to GP Gliders
"is a glider designed to the "16G cockpit" standard heavier than one designed with a rescue parachute (and including the parachute weight)?"
A designer would give you a precise answer but if you consider that you trade your back parachute against a rescue system, the delta is probably no more than 3kg (11kg - 8kg). This is likely much less than the additional weight required by latest EASA regs on cockpit integrity. The problem is that if you certify under EASA, you don't have the choice to go one way or the other. Therefore if you want the rescue system, weight goes up. |
#97
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My September 2017 visit to GP Gliders
"You suggested this company has better materials and design techniques than its rivals"
You should rad post more carefully, I don't recall having suggested GP has better materials. My only point was that the weight they are claiming aren't so incredible. I will not challenge your other statements since you seem be astute in aircraft design, certification and manufacturing. |
#98
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My September 2017 visit to GP Gliders
On Wednesday, 19 August 2020 at 17:47:52 UTC+3, jld wrote:
"No they don't. You have a 470kg glider in UL class that has MTOM of 472,5 kg (if national regs allow). Now EASA says that you can design and build an UL aircraft that has MTOM of 600kg (if national regs allow). The 470 kg GP fits into that weight limit perfectly" Maybe I was not clear enough and we fail to communicate. With new EASA limit (i.e. 600kg) the national limitS are being updated. If you check updated UL national regulations you will discover that there is more than MTOM being updated and influencing your design (Empty weight, minimum Payload, Vso, etc.). I checked and can confirm that you are wrong. There are no such regulations, other than allowed MTOM being higher (for sailplanes). For airplanes, only new rule is 45 kts stall speed instead of old 35 kts. I suspect your motivation for telling lies post after post is that you are GP dealer? I find it quite amazing that GP has been selling (though obviously not producing) GP15s for years and now they state that they "freeze the design" by Q1 2021. I mean what the actual f*ck? They are still designing it!? I saw prototype flying in 2018. Well good luck for those who have paid in advance. |
#100
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My September 2017 visit to GP Gliders
On Wednesday, 19 August 2020 at 16:27:43 UTC+1, jld wrote:
"You suggested this company has better materials and design techniques than its rivals" You should rad post more carefully, I don't recall having suggested GP has better materials. My only point was that the weight they are claiming aren't so incredible. I will not challenge your other statements since you seem be astute in aircraft design, certification and manufacturing. No need for the sarcasm. I'm not any better informed than average, and I'm not pretending to be You however have been smearing companies who have been making thousands of gliders for decades, airworthiness authorities in several countries, and more besides, and your expertise, whatever it is, propounds the low weight benefits of weaker cockpits (a claim not made by the manufacturer) and the cleverness or convenience of bypassing other standards Yes, certification does cost money, so finding another category with less of it can be an advantage, but you may cause concern if it sounds like you suggest glossing over design work too. |
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