VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Model Specific > RV-12
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 03-19-2016, 12:06 PM
EastCoastFlyer EastCoastFlyer is offline
 
Join Date: Nov 2012
Location: MA
Posts: 8
Default Rear window plexi vs. Lexan

I'm just about to tackle the rear window. Does anybody know what the pros and cons are of the Plexiglass vs. the Lexan rear window? I have the old Lexan window from my fuselage kit, but now Van's ships the Plexiglass rear window with the finish kit. I'm about to order my finish kit, so I could get and install the Plexiglass window if it is worth it. Any thoughts?
Reply With Quote
  #2  
Old 03-19-2016, 12:16 PM
DonFromTX's Avatar
DonFromTX DonFromTX is offline
 
Join Date: Oct 2010
Location: La Feria Texas
Posts: 3,461
Default

I have one of each, the plexi is tinted. I have not yet decided which one to use, but probably will use the plexiglas one. Way back when this first came up, the fact that the plexi would not craze and could be tinted was a plus, but Vans claimed it was a structural part of the plane, and the plexi was not strong enough. With my wing tanks with the fillers on each wingtip, I would have to get pretty sloppy to get fuel on the window now. I am down in the lower Rio Grande Valley and I think the tinted will serve me better in the hot sun.
__________________
AF1 (was RV12) EAB Air Force One, SN 461, N461DG VIKING/HONDA ENGINE POWERED!
A&P, PP-SEL, Pathological Flier, EAA Technical Counselor
EAA Chapter 595 President,http://www.595.eaachapter.org/index.htm
Retired US Army Officer
http://www.mykitlog.com/users/index....X&project=1903
Reply With Quote
  #3  
Old 03-19-2016, 12:43 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 6,367
Default

Quote:
Originally Posted by DonFromTX View Post
but Vans claimed it was a structural part of the plane, and the plexi was not strong enough.
I am pretty sure all that was said was that the rear window was structural so you are correct on that part, but it was never said that acrylic wasn't strong enough (or it wouldn't be offered in the kit now).

I think what was said was that if you substitute some other material for the lexan, make sure it is at least as strong (the comment was made in a thread where someone was saying they would look into providing an alternative window).
__________________
Any opinions expressed in this message are my own and not necessarily those of my employer.

Scott McDaniels
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
Reply With Quote
  #4  
Old 03-19-2016, 01:20 PM
skydiverlv skydiverlv is offline
 
Join Date: Jul 2008
Location: kansas
Posts: 259
Default

From what I recently witnessed with my rear window that decision would be a no brainer. I installed the window about 6 months ago and only this week removed the protection paper from the window. I found a small crack near the edge, does not go to the edge, nor radiates from a mounting hole. It is just there! So for now, a small stress relieving hole,then in the future, a generation II window will be installed after window tint is applied.
__________________

Larry Vandegrift
ULPower 260is, dual ECUs, dual 30 amp alternators
Reply With Quote
  #5  
Old 03-19-2016, 01:38 PM
DonFromTX's Avatar
DonFromTX DonFromTX is offline
 
Join Date: Oct 2010
Location: La Feria Texas
Posts: 3,461
Default

You were correct Scott, I went back and checked. You urged caution in making a change to a structural part, and someone else chimed in that Plexi was far less in strength than Lexan.
I had worried about that ever since, but now that it is solved, I think my tinted plexi is going in, not quite Phoenix, but we get a lot of sun here in the lower Rio Grande Valley area..

Quote:
Originally Posted by rvbuilder2002 View Post
I am pretty sure all that was said was that the rear window was structural so you are correct on that part, but it was never said that acrylic wasn't strong enough (or it wouldn't be offered in the kit now).

I think what was said was that if you substitute some other material for the lexan, make sure it is at least as strong (the comment was made in a thread where someone was saying they would look into providing an alternative window).
__________________
AF1 (was RV12) EAB Air Force One, SN 461, N461DG VIKING/HONDA ENGINE POWERED!
A&P, PP-SEL, Pathological Flier, EAA Technical Counselor
EAA Chapter 595 President,http://www.595.eaachapter.org/index.htm
Retired US Army Officer
http://www.mykitlog.com/users/index....X&project=1903
Reply With Quote
  #6  
Old 04-10-2016, 03:29 PM
EastCoastFlyer EastCoastFlyer is offline
 
Join Date: Nov 2012
Location: MA
Posts: 8
Default

An Update: I looked at 12-15 RV-12's at Sun-N-Fun and almost all with Lexan rear window had cracks/crazing. Everyone I spoke to said to definitely wait and install the Plexiglas rear window.
Reply With Quote
  #7  
Old 04-10-2016, 04:06 PM
rgmwa rgmwa is offline
 
Join Date: Feb 2010
Location: Perth, Western Australia
Posts: 1,499
Default

Quote:
Originally Posted by EastCoastFlyer View Post
An Update: I looked at 12-15 RV-12's at Sun-N-Fun and almost all with Lexan rear window had cracks/crazing. Everyone I spoke to said to definitely wait and install the Plexiglas rear window.
Where were the cracks/crazing? I slopped some fuel about the second time I filled up, and ended up with some fine cracks starting from 2 or 3 screw holes near the fuel cap. No real surprise there. However, the plane now has 85 hours on it, and I've just returned from a 4 week trip, covering about 4,000 miles. To my surprise, there are now very fine cracks starting from a number of screw holes on both the front and rear edges for the Lexan on both sides of the fuselage. The window was installed as per the plans (ie. no oversize holes, bushings etc), so I'm wondering if these are expansion/contraction cracks. Has anyone else come across this?

Incidentally, the plane performed very well on the trip. Landed on some very rough outback strips with no problems. The autopilot was a very useful addition, well worth the money. To my mind, the only drawback of the RV-12 as a cross country flyer is the relatively small fuel tank. Travelling across the remote parts of Australia you often have very few options for alternates if you can't make it into your destination. I like to land with a decent amount of fuel left in the tank, and another 5-7 gal would make all the difference. Not a complaint, just an observation, as I know all aircraft designs are compromises, and I'm aware of solutions others have put forward.
__________________
rgmwa
120346
Reply With Quote
  #8  
Old 04-10-2016, 04:31 PM
AZLeeJay AZLeeJay is offline
 
Join Date: Dec 2013
Location: Phoenix
Posts: 97
Default

I had very bad crazing in my rear window in the center of the window on both sides so I know it wasn't fuel related. This was in an SLSA with less than 100hrs. I've replaced it once and am seeing a few early signs that its returning, Plexiglass next time for sure! I also agree with your assessment regarding the fuel limitations.
Reply With Quote
  #9  
Old 04-10-2016, 05:40 PM
C120driver C120driver is offline
 
Join Date: Oct 2011
Location: Dayton, OH
Posts: 13
Default

Quote:
Originally Posted by DonFromTX View Post
. . . but Vans claimed it was a structural part of the plane, and the plexi was not strong enough. . . .
I was going back and looking more carefully at what had been said in previous posts and this one quote from DonFromTX caught my attention. Windows in airplanes are not counted on for structural load paths. They are there to take wind loads and if pressurized the internal pressure loads. The structure for strength purposes is analyzed as an open hole and all airframe loads have to flow around that open hole. The structure around windows in jet aircraft are structurally sized with the window as a hole in the fuselage. If windows were assumed to be structural, light airplanes that have a bird impact on the windscreen should experience a catastrophic structural failure of the airplane, but that does not happen because the flight loads are flowing around the windscreen. You should be able to experience a structural failure of either one of the RV-12 rear windows and not experience an airframe failure.

I think there must have been a misunderstanding at one time as to what Vans Aircraft engineering said.
Reply With Quote
  #10  
Old 04-10-2016, 05:47 PM
flyboy1963's Avatar
flyboy1963 flyboy1963 is offline
 
Join Date: Oct 2008
Location: West Kelowna, B.C. Canada
Posts: 2,277
Default not 'the right stuff'?

Not to beat up on anyone, but polycarbonate is simply not a good fit for this application. I'm sure the manufacturer, and engineers at Van's, were ok with this cold formed wrap at such a large radius, and it was within 'spec' for the material.
The problem is; this imparts stress, and sooner than later, these cracks, risers, and crazing results. On a rear window, this is not critical, but I hardly see how it can be 'stronger' than plexi, when it eventually busts in half!
The F-22 has a huge lexan canopy, but you can be sure that it is surface hardened, tinted, and molded at something well above room temperature!!!

Lexan was first spec'd as a security glazing, and as such, needed to perform vertically, and relatively flat. Laying it down and bending it is starting to depart from its' best characteristics; such as impact resistance.
Yes, in the 1970's, we were lured by the appeal of Makrolon, Lexan etc. and made several windshields flat wrapped, siliconed, and drilled, 6" from a fuel filler cap, before coming to our senses.
I just hate to see others go thru the same trial and error process .......45 years later!!!!!
__________________
Perry Y.
C-FINT RV-9a - SOLD!....need a Glastar now!!!
West Kelowna, BC

....paid up Nov. 2016-17
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 06:33 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.