VansAirForceForums  
Home > VansAirForceForums

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

- Today's Posts | Insert Pics

  #11  
Old 01-12-2018, 08:48 AM
Rupester Rupester is offline
 
Join Date: Dec 2005
Location: Mahomet, Illinois
Posts: 2,196
Default

Great post, Scott. A practical and innovative solution to a relatively common problem that doesn't offer a lot of fix options. If I were faced with the same problem, I'd go the same way. No way do I want to look at all those hours for building a second canopy in its entirety.
Thanks!!!!!
__________________
Terry Ruprecht
RV-9A Tip-up; IO-320 D2A
S. James cowl/plenum
(Dues paid thru Nov '18)
Reply With Quote
  #12  
Old 01-12-2018, 11:57 AM
RV7ForMe RV7ForMe is offline
 
Join Date: Jul 2015
Location: Europe
Posts: 375
Default Thank you!

Hope I never need this but I have downloaded it with pictures and put into my folder for future reference if the pictures were to disappear!

Thank you for writing it up.
__________________
VAF dues paid until 10/2019
RV7 - Empennage 95% done
RV7 - Wings Started...
Cessna Rocket 210HP - Best dang 172 Ever made! (sold)
Reply With Quote
  #13  
Old 01-12-2018, 12:07 PM
mfleming's Avatar
mfleming mfleming is offline
 
Join Date: Sep 2016
Location: Joseph, Oregon
Posts: 280
Thumbs up

What a great write up. I've saved this post as a webarchive for the future.

This should be a sticky!
__________________
Michael Fleming
Joseph, OR
sagriver at icloud dot com

RV-7 Slider #74572
Started 11/2016
Empennage completed 11/2016 (sans fiberglass)
Ailerons and flaps completed 3/2017.
Wings completed 12/2017 (sans fiberglass)
Started on QB fuselage 01/2018
Reply With Quote
  #14  
Old 01-12-2018, 02:20 PM
goatflieg's Avatar
goatflieg goatflieg is offline
 
Join Date: Jul 2013
Location: Clarkston, MI
Posts: 401
Default

As I come closer to building up my own RV-8 canopy, this thread answered one important question I had: would bonding with only Sikaflex (no rivets) eliminate the chance of developing a crack later? The answer here is, no. Although you flew for many hours, it eventually happened... and since I live in Michigan and face some daunting temperature extremes, I can't help wondering if a canopy crack is likely (or perhaps unavoidable) in my future, however distant. I will build with the mind of making sure there is no built-in stress during fabrication, and the question of whether or not to use the suspenders-and-belt method of blind rivets and Sikaflex remains unresolved. I'm very glad you shared the details of your experience... I also agree that this post should be saved as a sticky in the RV-8 archives. It certainly is helpful information.
__________________
Martin J Filiatrault
Clarkston, MI
RV-8 #83507 - empennage complete (except fiberglass)
QB wings & fuselage work continues
N657AR reserved
Builder websites:
http://goatflieg.blogspot.com/
http://www.mykitlog.com/goatflieg/
YouTube Channel:
https://www.youtube.com/user/goatflieg
Dues paid for 2018... extra payment included for psychological therapeutic services rendered.

_______________________

Have you ever gotten the feeling you were smarter than you could ever prove?

Last edited by goatflieg : 01-12-2018 at 02:23 PM.
Reply With Quote
  #15  
Old 01-12-2018, 03:56 PM
scsmith scsmith is offline
 
Join Date: Jan 2008
Location: Ashland, OR
Posts: 1,884
Default

Thanks Scott, great informative write-up.

As I read along, I kept hoping for the big surprise that the filler material would in fact become transparent. I wonder if there is a product that would be more clear?

One question I have on your Sikaflex installation. One variable in various people's use is how thick a layer of Sikaflex they create between the frame and the canopy acrylic. I used garden-hose spacers that created a gap of almost 3/16" that got filled with Sikaflex. The hope was/is that this would provide enough expansion flexibility to allow the canopy to grow or shrink without (or with less) stress.

So-how thick is your Sikaflex layer between the frame and canopy?
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet"
Hobbs 515 in 9 years (would have flown more this year if not for fire smoke)
also LS-6-15/18 sailplane
VAF donation Dec 2017
Reply With Quote
  #16  
Old 01-12-2018, 05:38 PM
Captain Avgas Captain Avgas is offline
 
Join Date: Oct 2005
Location: Melbourne, Australia
Posts: 1,659
Default

Quote:
Originally Posted by scsmith View Post

One question I have on your Sikaflex installation. One variable in various people's use is how thick a layer of Sikaflex they create between the frame and the canopy acrylic.
The thickness of the sealant will indeed be crucial. But there will be other important factors as well. In a post on VansAirforce dated 5/8/2008 I stated the following:

In actual fact polymethyl methacrylate (PMMA) or "acrylic" as it is commonly known is notoriously difficult to obtain a good bond to. Sikaflex itself will not bond to PMMA. An interlayer (or adhesion promoter) needs to be used. In the case of Sikaflex its 209 primer contains 25% MEK and 20% Ethyl Acetate. Both of these are solvents known to break down the cross links of the long chain molecules in PMMA. In the longer term that might very well lead to edge cracking (one case already reported).... the very thing builders were anxious to avoid.

My opinion is that the ongoing reports of cracks in Sikaflex canopies result from the following factors:

a) Vans canopies are either vacuum or pressure formed and will contain locked-in internal stresses.
b) Builders do not properly treat cut edges to fully remove microscopic imperfections/discontinuities.
c) The aggressive solvents in Sikaflex 209 primer will attack the acrylic, particularly at edges where there are discontinuities.
d) Builders are not using the recommended thickness of Sikaflex sealant.

Once small cracks form at the edges of the canopy they will continue to run due to an engineering phenomenon known as "work of fracture".

However despite all of the above, the main reason I would be very cautious about using the Sikaflex approach is because it may be bonded to Vans powder coating which itself has no known quality control and therefore provides no guarantee of adhesion.
__________________
Regards
Bob Barrow
RV7A
Reply With Quote
  #17  
Old 01-13-2018, 08:18 AM
Captain Avgas Captain Avgas is offline
 
Join Date: Oct 2005
Location: Melbourne, Australia
Posts: 1,659
Default

Quote:
Originally Posted by Scott Chastain View Post
From the PGG DX-Series Data Sheet: "PPG DX Cleaners are specifically designed to remove waxes, grease, silicones, road tar, engine oil, overspray, adhesives and other contaminants. They can be used on bare metal, primers, automotive finishes or to clean plastic parts <emphasis mine>.
Hi Scott, PPG DX330 cleaner is a general purpose auto refinish wax and grease remover. It may be safe to use on some auto plastics such as thermoplastic olefins etc as used in bumper bars and other trims but I wouldn't use it on an acrylic aircraft canopy. I suspect that the fact that your gas inclusions are occurring mainly along the interface of the acrylic and the Plasti-Fix adhesive points to a problem with the cleaner.

But I'm also amazed that the Plasti-Fix instructions called for the use of denatured alcohol as a cleaner. To me, denatured alcohol is methylated spirits which generally contains products that are certain to cause stress cracking.
__________________
Regards
Bob Barrow
RV7A

Last edited by Captain Avgas : 01-13-2018 at 08:25 AM.
Reply With Quote
  #18  
Old 01-13-2018, 02:57 PM
snopercod's Avatar
snopercod snopercod is offline
 
Join Date: Aug 2016
Location: Asheville, NC
Posts: 1,367
Default

Awesome job, Scott, and a very helpful writeup. It gave me chills looking at you gouging out the crack with a Dremel tool. I could just see the tool skittering across the canopy I don't know if this information will be of any benefit to the RV Community but on my Lancair, I used Hysol structural adhesive to bond the acrylic canopy to the fiberglass frame. IIRC, I cleaned both pieces with automotive wax and silicone remover, and lightly sanded the canopy in the joint area. On the inside, I reinforced the joint with BID tapes. No cracks in 220 hrs. (knock on acrylic). I have nightmares about cracks in my canopy...
__________________
(2018 dues paid)
Reply With Quote
  #19  
Old 01-16-2018, 05:45 AM
Tooch Tooch is offline
 
Join Date: Nov 2011
Location: Amelia, Va
Posts: 195
Default Heat Pad?

Hey Scott,
In the third picture down, what is that orange pad with the 2 wires going to it?
Looks like some kind of heat pad
Reply With Quote
  #20  
Old 01-16-2018, 08:09 AM
RV8 Tom RV8 Tom is offline
 
Join Date: Nov 2005
Location: New lenox , Illinois
Posts: 58
Default

I'm guessing light strip for the panel.
__________________
Tom Ellis
New Lenox, IL
USMC
Tech Councilor
Flight Adviser
RV 8, N812TE- flying
RV-12- building
R-22, R-44 flying
Titan T-51- building
Rotorway 162F flying
AVID MK IV- kids project
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 03:09 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.