VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #1  
Old 02-04-2022, 07:46 AM
BravoAlphaRomeo BravoAlphaRomeo is online now
 
Join Date: Jan 2020
Location: Edgewood, KY
Posts: 38
Default Lexan expansion

Working right now on installing my rear window into RV14. All going fine so far. My question is this - How does tapping the lexan and roll bar together allow the lexan to expand/contract at all ? Seems like untapped-slightly oversized hole in lexan would allow for this….

What am I missing ?
__________________
BravoAlphaRomeo
172N 180HP
RV14A - under construction
Dues paid
Reply With Quote
  #2  
Old 02-04-2022, 08:11 AM
DanH's Avatar
DanH DanH is offline
 
Join Date: Oct 2005
Location: 08A
Posts: 10,939
Default

Old subject. Glazing plastics have a coefficient of thermal expansion much higher than the steel frame, so some oversizing of the fastener holes, or flexible (i.e. adhesive) fastening is desirable.

Tip: Stress cracks begin at surface flaws and sharp edges. Drill a hole in plexiglass and then look close at the hole with a 10x magnifier. It's generally a textbook stress concentration mess.

Chuck a very small fine grit rotary stone in an air tool. Form the tip into a point, then deburr the hole with the stone and look again.

Another approach is dichloromethane (aka methylene chloride) on a Q-tip. Makes a beautiful smooth edge, but don't breathe it!
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Reply With Quote
  #3  
Old 02-04-2022, 08:52 AM
wawrzynskivp wawrzynskivp is offline
 
Join Date: Feb 2018
Location: Incline Village Nv
Posts: 338
Default A fine point and maybe superfluous

There are a few differences between acrylic and polycarbonate (Plexiglass and Lexan) Edge treatments, solvent exposure, and bonding need to be specific to each material.

I believe my -7 canopy is plexiglass, don't know if Lexan is used on other models.

I swapped out my hatch glass on a sailboat once from Plexi to Lexan. Definite advantages/disadvantages to each.
__________________
Vincent 'Duck' Wawrzynski
LtCol USMC (Ret)
F-18/F-5/F-16, AH-1/UH-1/CH-53/CH-46, C-130/AN-2
RV-7 complete with all the gadgets
Aviation Safety/Accident Inspector/Investigator
San Jose State University Av Faculty, CFI/GFI S/M (I)

Last edited by wawrzynskivp : 02-04-2022 at 01:12 PM.
Reply With Quote
  #4  
Old 02-04-2022, 09:21 AM
Mudfly Mudfly is offline
 
Join Date: Dec 2011
Location: Alpharetta, Ga
Posts: 223
Default

Look ahead in the plans. Later, those tapped threads in the plexi get drilled out. Think I may have even upsized those holes a bit more than called for to allow for expansion/contraction.
__________________
Shawn Edwards
RV-14A (140174)
www.myrv14build.blogspot.com
2021 VAF Donation
Reply With Quote
  #5  
Old 02-04-2022, 09:24 AM
BravoAlphaRomeo BravoAlphaRomeo is online now
 
Join Date: Jan 2020
Location: Edgewood, KY
Posts: 38
Default

Replying to both - I have read about everything the forum has to offer on drilling, cutting and general handling of the lexan and plexiglass. I am using a lot of the tips I picked up with good success.

“so some oversizing of the fastener holes is desirable”

Still back to my original question - why do the Vans plans not incorporate this philosophy ? It makes total sense but its not built that way…

Not trying to make a whopper deal out of it, just trying to learn a thing or two.
__________________
BravoAlphaRomeo
172N 180HP
RV14A - under construction
Dues paid
Reply With Quote
  #6  
Old 02-04-2022, 09:25 AM
BravoAlphaRomeo BravoAlphaRomeo is online now
 
Join Date: Jan 2020
Location: Edgewood, KY
Posts: 38
Default

Shawn - posted at same time. I’ll look ahead in the plans.

Thanks !
__________________
BravoAlphaRomeo
172N 180HP
RV14A - under construction
Dues paid
Reply With Quote
  #7  
Old 02-05-2022, 08:26 AM
BravoAlphaRomeo BravoAlphaRomeo is online now
 
Join Date: Jan 2020
Location: Edgewood, KY
Posts: 38
Default

Thanks for tip Shawn - Vans it’s basically using the window as a guide for tapping the roll bar so you don’t put the tap in crooked. Holes in the window upsized later and the threads are removed. I think I’m clear now
__________________
BravoAlphaRomeo
172N 180HP
RV14A - under construction
Dues paid

Last edited by BravoAlphaRomeo : 02-05-2022 at 09:06 AM.
Reply With Quote
  #8  
Old 02-05-2022, 10:17 AM
Mudfly Mudfly is offline
 
Join Date: Dec 2011
Location: Alpharetta, Ga
Posts: 223
Default

Sure you’ve heard of the dreaded broken tap in the roll bar scenario. To try and avoid that, I did some research and seems the use of a two flute tap may help avoid that situation. Pic attached of what I used.
Good luck!
Attached Thumbnails
Click image for larger version

Name:	C5039F9E-4B39-42B9-91E3-140BBC2EBD86.jpg
Views:	37
Size:	406.6 KB
ID:	21840  
__________________
Shawn Edwards
RV-14A (140174)
www.myrv14build.blogspot.com
2021 VAF Donation
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 07:47 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.