Hasse Posted October 18, 2015 Posted October 18, 2015 Hi, This is a mystery but I have got severe cracks in the Lexan window and one door of my Savannah S. As far as I know, for no reason. These are no small scratches and some of them are almost 5 inches long and runs through the whole sheet as if after a bird crash. It's one year now since I build the aircraft and and I have been flying approximately once every week and there has been no problems with the Lexan before until today when I noticed the disaster. Has anyone come across anything similar or should I expect that this is a sabotage.
SDQDI Posted October 18, 2015 Posted October 18, 2015 There hasn't been any fuel spilt on or near them Hasse?
Kyle Communications Posted October 19, 2015 Posted October 19, 2015 My doors got small cracks in them I gather it from some extra stress on the lexan when I built the doors. I replaced the pilot side door but left the pax door still the same the cracks have not gone any further. My main screen developed a crack at the bottom and I stopped it with a 1mm drill hole at the end of the crack. The screen is also under a lot of tension as well. I think it has to do with the rivets and how they fit into the lexan. The hole size maybe too tight so when the rivet is pulled it puts stress on the inside of the hole. The holes in the lexan may need to be slightly larger than supplied. Mark 3
Centreline Posted October 19, 2015 Posted October 19, 2015 Hi,This is a mystery but I have got severe cracks in the Lexan window and one door of my Savannah S. As far as I know, for no reason. These are no small scratches and some of them are almost 5 inches long and runs through the whole sheet as if after a bird crash. It's one year now since I build the aircraft and and I have been flying approximately once every week and there has been no problems with the Lexan before until today when I noticed the disaster. Has anyone come across anything similar or should I expect that this is a sabotage.[/
rick morawski Posted October 19, 2015 Posted October 19, 2015 If it's not fuel I'd guess you've cleaned them with something that affects the polycarbonate. The cracks that radiate from the rivet holes are usually only 10-15 mm long , but can grow longer though flexing, the cracks from fuel or other hydrocarbons or usually longer, typically 100mm or so, and can join up an make a big hole if not fixed. These are just my observations from replacing more than a few Windows. If you are replacing with factory cut ones or make your own from sheet poly using old window as template make sure you oversize the rivet holes (agree with Marks post above) to avoid the stress cracks rising from the expanding rivets. Also I have heard windex has ammonia in it and should not be used on plastic. Cheers Rick 1
Downunder Posted October 19, 2015 Posted October 19, 2015 Being in Sweden, could ambient/OAT temps be a factor? 1
Hasse Posted October 19, 2015 Author Posted October 19, 2015 My doors got small cracks in them I gather it from some extra stress on the lexan when I built the doors. I replaced the pilot side door but left the pax door still the same the cracks have not gone any further. My main screen developed a crack at the bottom and I stopped it with a 1mm drill hole at the end of the crack. The screen is also under a lot of tension as well. I think it has to do with the rivets and how they fit into the lexan. The hole size maybe too tight so when the rivet is pulled it puts stress on the inside of the hole. The holes in the lexan may need to be slightly larger than supplied.Mark Yes, it may have to do about tension. Most of the cracks starts from a rivet hole. A few of these cracks run as a single paths and end after a couple of cm or so. However, there are cracks that start as single for 5 cm and then spread like a feather. There are a couple of those at the sharp bend where the windscreen meets the left wing root (nothing on the right hand side). Same type of cracks can also be found on the left door (there are no cracks on the passenger door). Perhaps it's all about tension and too tightly drilled holes as you say Mark. The tension around the holes in the left door may arise when the door is closed and secured i.e. squeezed against the door frame. By the way, my passenger door hasn't been used much as I am still doing the 50 hours of flight testing. So the remedy should include oversized Lexan holes (perhaps smoothly sanded) and carefully made doors that fit the frame without tension when closed and secured. Right? 2
Hasse Posted October 19, 2015 Author Posted October 19, 2015 over tight nuts and bolts... No, no nuts and bolts overtightened but perhaps too small rivet holes in the Lexan sheets.
Hasse Posted October 19, 2015 Author Posted October 19, 2015 If it's not fuel I'd guess you've cleaned them with something that affects the polycarbonate. The cracks that radiate from the rivet holes are usually only 10-15 mm long , but can grow longer though flexing, the cracks from fuel or other hydrocarbons or usually longer, typically 100mm or so, and can join up an make a big hole if not fixed.These are just my observations from replacing more than a few Windows. If you are replacing with factory cut ones or make your own from sheet poly using old window as template make sure you oversize the rivet holes (agree with Marks post above) to avoid the stress cracks rising from the expanding rivets. Also I have heard windex has ammonia in it and should not be used on plastic. Cheers Rick Well Rick, The cracks I've got now are beyond salvation. I will try to post some Pictures when I know how. Most likely I have to replace the window and the doors (at least the left door) pretty soon. Was it difficult to install a new window? Did you also replace the roof even if it was ok?
SDQDI Posted October 19, 2015 Posted October 19, 2015 That's an interesting looking snack. What is the topping? Those eggs look nice:thumb up:
SDQDI Posted October 19, 2015 Posted October 19, 2015 Also be very careful if you are painting your frames after you have installed the window, even a close wiff of fumes is enough to send those cracks out.
Hasse Posted October 19, 2015 Author Posted October 19, 2015 Being in Sweden, could ambient/OAT temps be a factor? I don't think that the ambient temperature as such is any key factor. The Lexan sheets has been sitting on my aircraft for over a full year now during a Swedish winter (not very cold though) and a very warm summer without any obvious cracks untill yesterday. Nevertheless, who knows, small cracks may have risen early on without me seeing them and then suddenly matured when circumstances were optimal. Perhaps at big differences in temperature. It is fall in Sweden with some temperature variation between morning and day time. Still, it seems that this is too small temperature variation to hurt the lexan.
rick morawski Posted October 19, 2015 Posted October 19, 2015 That's an interesting looking snack.What is the topping? Those eggs look nice:thumb up: That's not a snack it's his thongs! 2
Hasse Posted October 19, 2015 Author Posted October 19, 2015 Also be very careful if you are painting your frames after you have installed the window, even a close wiff of fumes is enough to send those cracks out. Interesting SDQDI! Tell me more about paint fumes and cracks. I'm a bit sensitive to this as I did all the painting myself, as an amateur. 1
SDQDI Posted October 19, 2015 Posted October 19, 2015 Interesting SDQDI! Tell me more about paint fumes and cracks. I'm a bit sensitive to this as I did all the painting myself, as an amateur. It's basically the same as putting fuel on the screen Hasse. The thinners in the paint if applied directly will cause almost instant cracks but even painting close they seem to be able to get past masking tape and can do damage. As far as my limited experience goes it is best to put the screens in after painting (a few days after so it has completely dried) but that isn't always an option. If you havnt seen it before and you have a spare scrap of screen, splash just a drop of fuel (or paint thinners) on it and have a look at the results. Most of the cracks in your pics are coming from rivet holes or bends in the screen but I wouldn't be surprised if the painting is a big factor. 1
Hasse Posted October 19, 2015 Author Posted October 19, 2015 [ATTACH=full]38785[/ATTACH] [ATTACH=full]38786[/ATTACH] [ATTACH=full]38787[/ATTACH] [ATTACH=full]38788[/ATTACH] [ATTACH=full]38789[/ATTACH] Hi Dennis, and thanks for the help posting the Pictures of the cracks.
rick morawski Posted October 19, 2015 Posted October 19, 2015 Well Rick,The cracks I've got now are beyond salvation. I will try to post some Pictures when I know how. Most likely I have to replace the window and the doors (at least the left door) pretty soon. Was it difficult to install a new window? Did you also replace the roof even if it was ok? Hi Hasse, No, not to difficult to replace windows/windscreen if you are handy with derivetting, just be careful not to destroy the part if you are going to use it for a template, and no I did not replace anything that wasn't damaged. Cheers Rick
rick morawski Posted October 19, 2015 Posted October 19, 2015 [ATTACH=full]38785[/ATTACH] [ATTACH=full]38786[/ATTACH] [ATTACH=full]38787[/ATTACH] [ATTACH=full]38788[/ATTACH] [ATTACH=full]38789[/ATTACH] Wow, that's a lot of cracking, looks just like fuel induced cracks to me, did he have a fuel tank leak or maybe a spill while refuelling? Always have doors closed when refuelling for that reason. 1
Hasse Posted October 19, 2015 Author Posted October 19, 2015 It's basically the same as putting fuel on the screen Hasse.The thinners in the paint if applied directly will cause almost instant cracks but even painting close they seem to be able to get past masking tape and can do damage. As far as my limited experience goes it is best to put the screens in after painting (a few days after so it has completely dried) but that isn't always an option. If you havnt seen it before and you have a spare scrap of screen, splash just a drop of fuel (or paint thinners) on it and have a look at the results. Most of the cracks in your pics are coming from rivet holes or bends in the screen but I wouldn't be surprised if the painting is a big factor. Thanks SDQDI! Good information. I'll have plenty of material for testing when I replace the lexan and yes, I may have painted too close.
Hasse Posted October 19, 2015 Author Posted October 19, 2015 Hi Hasse,No, not to difficult to replace windows/windscreen if you are handy with derivetting, just be careful not to destroy the part if you are going to use it for a template, and no I did not replace anything that wasn't damaged. Cheers Rick Thanks Rick, That's hopeful. It's just so disappointing having to replace the door and window after only one year.
rick morawski Posted October 19, 2015 Posted October 19, 2015 It's basically the same as putting fuel on the screen Hasse.The thinners in the paint if applied directly will cause almost instant cracks but even painting close they seem to be able to get past masking tape and can do damage. As far as my limited experience goes it is best to put the screens in after painting (a few days after so it has completely dried) but that isn't always an option. If you havnt seen it before and you have a spare scrap of screen, splash just a drop of fuel (or paint thinners) on it and have a look at the results. Most of the cracks in your pics are coming from rivet holes or bends in the screen but I wouldn't be surprised if the painting is a big factor. This is very true too, I leave the thin plastic protection on while painting plus masking over the top to try and avoid this. Also do not have your windscreen in place while gluing in the carpets- the fumes from that glue will crack the plastic or permanently fog it.
Kyle Communications Posted October 19, 2015 Posted October 19, 2015 Holy guacamole batman..thats a lot of cracks mine are nothing like that The pics attached the smaller cracks are on the pax door and they are still the same and have not grown...the other 2 pics with the bad cracks is after a fuel leak which you can see on the underside of the wing
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