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#51
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Taurus glider for sale
My thoughts are.......UV degradation of the fibers is the prime reason for the white coating (to reduce UV getting to fibers).
Ever see synthetic ropes out in UV? Most are white, but the UV destroyes them, thus strength goes to poop. Same for a lot of plastic woven tarps. Not saying I am correct, just some observations..... |
#52
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Taurus glider for sale
At 18:15 21 May 2019, ripacheco1967 wrote:
Don't scare me now.=20 50=C2=BAC (122=C2=BAF) is VERY EASY to reach in Florida. You mean to tell me all those trailers sitting out in Florida are slowly ba= king their gliders into oblivion? The Scheuffler L285 resin widely used in German and Polish gliders requires to be heat treated at not less than 54C (129F) before the aircraft is flown. The same resin is heat treated at 80C when used for power aircraft which have to operate at higher ambient temperatures. |
#53
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Taurus glider for sale
Aside from gliders, the only other composite aircraft I've flown have been the Diamond DA20 and DA40, both of which have temp activated disks on the seat bulkhead. the color changes when the inside temperature exceeds 131 degrees F. There are also placards stating the temperature limitations warning of possible structural failure if flown when the temp has been exceeded, granted they mean flying it if the aircraft is that hot. But still, if the manufacturer states there is a danger, there must be one. I know my POH in the gliders I've flown state temperature limitations, though I've not seen any fancy temp sensitive color turn tapes glued in the cockpit of any glider..
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#54
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Taurus glider for sale
There is a bunch of data on MGS epoxy here. www.cstsales.com/mgs_epoxy.html
I wouldn’t worry about any gliders stores in Florida or the Mojave desert. |
#55
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Taurus glider for sale
On Tuesday, May 21, 2019 at 11:15:21 AM UTC-7, ripacheco1967 wrote:
Don't scare me now. 50ºC (122ºF) is VERY EASY to reach in Florida. You mean to tell me all those trailers sitting out in Florida are slowly baking their gliders into oblivion? Keep in mind that I was using SC-14 resin as an example, and although likely similar to the SC-14, I don't know exactly which resin glider manufacturers use. Realistically, short exposure to 50 C while in the trailer (not under load) won't do major damage the glider. However, at significantly higher temperatures or under load, some damage might occur. UV light causes widespread electron jumps due to its short wavelength (without high enough quantum energies that they have the same effect as XRays/Gamma radiation) and hence does not readily penetrate anything. So, although composites may be damaged if directly subjected to UV light, any thin layer of anything between the structural composite and UV light will be sufficient, it doesn't need to be white. Thomas |
#56
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Taurus glider for sale
On Tuesday, May 21, 2019 at 11:16:45 AM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote:
My thoughts are.......UV degradation of the fibers is the prime reason for the white coating (to reduce UV getting to fibers). Ever see synthetic ropes out in UV? Most are white, but the UV destroyes them, thus strength goes to poop. Same for a lot of plastic woven tarps. Not saying I am correct, just some observations..... It's not the fibers, well not with fiberglass and carbon per-se, it's the epoxy resin that is the issue, including how failing epoxy causes the reinforcing fibers to break/degrade. Epoxy is highly prone to UV dammage, it sucks. And yes the white is also needed to keep the temperature down. Hard to say there is a "prime reason" when addressing both UV exposure of the epoxy and high reflectivity to keep temperature low are both necessary. |
#57
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Taurus glider for sale
My Libelle POH includes a section that discusses various temperature considerations for the fiberglass construction of the glider. Some interesting temperature recommendations include:
Storage in enclosed or open trailer - 100 C Working on a wing suspended end to end on sawhorses - 85 C max Assembled glider on the ground - 82 C max In normal flight - 70 C max Aerotow - 61 C max Winch launch - 60 C max The POH also points out that storage at any temp between 54 C and 80 C "is like a tempering action that will increase the full load limit of the structure. No further profit" will be obtained at temperatures above 80 C. Robert On Tuesday, May 21, 2019 at 2:47:45 PM UTC-5, wrote: Aside from gliders, the only other composite aircraft I've flown have been the Diamond DA20 and DA40, both of which have temp activated disks on the seat bulkhead. the color changes when the inside temperature exceeds 131 degrees F. There are also placards stating the temperature limitations warning of possible structural failure if flown when the temp has been exceeded, granted they mean flying it if the aircraft is that hot. But still, if the manufacturer states there is a danger, there must be one. I know my POH in the gliders I've flown state temperature limitations, though I've not seen any fancy temp sensitive color turn tapes glued in the cockpit of any glider. |
#58
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Taurus glider for sale
On Tuesday, May 21, 2019 at 2:18:43 PM UTC-7, Darryl Ramm wrote:
On Tuesday, May 21, 2019 at 11:16:45 AM UTC-7, Charlie M. (UH & 002 owner/pilot) wrote: My thoughts are.......UV degradation of the fibers is the prime reason for the white coating (to reduce UV getting to fibers). Ever see synthetic ropes out in UV? Most are white, but the UV destroyes them, thus strength goes to poop. Same for a lot of plastic woven tarps. Not saying I am correct, just some observations..... It's not the fibers, well not with fiberglass and carbon per-se, it's the epoxy resin that is the issue, including how failing epoxy causes the reinforcing fibers to break/degrade. Epoxy is highly prone to UV dammage, it sucks. And yes the white is also needed to keep the temperature down. Hard to say there is a "prime reason" when addressing both UV exposure of the epoxy and high reflectivity to keep temperature low are both necessary.. Yes, Darryl is right that the epoxy is what's prone to UV radiation, not the fibers. But at the end of the day the fibers don't do anything unless properly bonded. Refer to another interesting paper on the effect of UV (and humidity) on composites: http://me.eng.sunysb.edu/~compmech/downloads/N29.pdf 29% decrease in transverse strength over 1000hrs of repeated UV and condensation. Luckily, only a small decrease in longitudinal strength was observed (most of the load bearing is longitudinal). Obviously the gel coat (or polyurethane) will reduce this effect, but dang! Thomas |
#59
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Taurus glider for sale
On Tuesday, May 21, 2019 at 12:15:21 PM UTC-6, ripacheco1967 wrote:
Don't scare me now. 50ºC (122ºF) is VERY EASY to reach in Florida. You mean to tell me all those trailers sitting out in Florida are slowly baking their gliders into oblivion? No. Tg of MGS epoxy, which most sailplane manufacturers use when post cured, is around 200 deg F. Mike |
#60
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Taurus glider for sale
Thomas Greenhill wrote on 5/21/2019 10:04 AM:
This is also why wise owners tend to prefer fiberglass-top trailers over metal ones in places that get very hot. As you can imagine, the inside of a metal trailer might easily exceed 50 degrees C (122 deg f) on a hot summer day. Why won't that happen to a fiberglass top trailer? The ones I had got plenty hot inside. -- 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 - "Transponders in Sailplanes - Dec 2014a" also ADS-B, PCAS, Flarm http://soaringsafety.org/prevention/...anes-2014A.pdf |
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