What canopy adhesive to use?

[LongJourney]

I've done a search in both RAS and on the web but I'm not finding the information I'm looking for. I'm restoring a 1963 S Austria and one of the previous owners used what I think is Sikaflex to bond the canopy glass to the metal canopy frame. It's now separating badly. What should I use to bond the plexiglass to the frame? And should I prime the metal frame and then scuff it where the glass will be bonded, or leave it bare until after the glass is glued on?

Thanks for your help,

Jeff

[AS]

Jeff,

do you know which Sikaflex product was used? The stuff we use in all sorts of applications on wind turbines is type 221 and it is a Urethane sealant/glue which is incredibly UV and weather resistant. Our preferred color is white but it comes in different colors, too.

Uli
'AS'

[AS]

Meant to add: as long as the surface is free of dust, dirt and grease, it sticks to just about anything without any special surface prep.

[LongJourney]

Uli, I'm not even sure it IS Sikaflex. I was told by someone that it was the same stuff they use on RV canopies. What's on my canopy is a black, rubbery adhesive.

Thanks,

Jeff

[christoph...@googlemail.com]

The repair manual of my LS8 lists the following material as canopy bonding agent: Macroplast UK8303 B60 (resin), Macroplast UK5400 (hardener). It's a PU based glue available from Loctite and other brands.

Christoph

[LongJourney]

On Tuesday, August 15, 2017 at 3:10:38 AM UTC-5, christoph...@googlemail.com wrote:
> The repair manual of my LS8 lists the following material as canopy bonding agent: Macroplast UK8303 B60 (resin), Macroplast UK5400 (hardener). It's a PU based glue available from Loctite and other brands.
>
> Christoph

Christoph, this looks like just what I need. Unfortunately, it doesn't seem to be readily available in the U.S.

[LongJourney]

After reading some RV builder sites, I'm thinking what was used on my canopy was Proseal, not Sika.

[Dave Nadler]

On Tuesday, August 15, 2017 at 3:10:38 AM UTC-5, christoph...@googlemail.com wrote:

> The repair manual of my LS8 lists...

Careful, that's for bonding plexi to IIRC fiberglass canopy frame.
1963 Austria probably uses different material for frame.
Better ask on some of the vintage forums!

[Steve Leonard]

On Tuesday, August 15, 2017 at 10:04:50 AM UTC-5, LongJourney wrote:
>
> After reading some RV builder sites, I'm thinking what was used on my canopy was Proseal, not Sika.

Pretty sure it is NOT Proseal. When that stuff cures, it is stuck. It doesn't seem to deteriorate with heat, moisture, UV exposure, or anything. Yes, it is a black (or very dark gray), sort of rubbery when cured adhesive. But from my experience, it will not fail. The plex will break, or the steel tube frame can rust away, but the Proseal will not separate.

I was once told that 3M 5200 is great stuff, but I have not used it, myself. I think you can find it referenced in another thread here on gluing stuff together.

Steve Leonard

[Eric Munk]

L285/L335 with microballoons was used by a large number of german and
polish manufacturers. Poles usually apply Aerodux and grind that down as a

primer to make the epoxy stick to the plexi. Alternatively, using a
polyesther
instead of an epoxy makes for a stronger joint but significantly shorter
potlife
(minutes not hours). I have seen various other modern kits used too. Some
with great succes.

At 15:28 15 August 2017, Steve Leonard wrote:
>On Tuesday, August 15, 2017 at 10:04:50 AM UTC-5, LongJourney wrote:

>>=20

>> After reading some RV builder sites, I'm thinking what was used on my

>can=

>opy was Proseal, not Sika.
>
>Pretty sure it is NOT Proseal. When that stuff cures, it is stuck. It

>doe=

>sn't seem to deteriorate with heat, moisture, UV exposure, or anything.

>Ye=

>s, it is a black (or very dark gray), sort of rubbery when cured
adhesive.

>=

> But from my experience, it will not fail. The plex will break, or the

>ste=

>el tube frame can rust away, but the Proseal will not separate.
>
>I was once told that 3M 5200 is great stuff, but I have not used it,

>myself=
>.. I think you can find it referenced in another thread here on gluing
>stuf=
>f together.
>
>Steve Leonard
>
>

[Scott Williams]

All the Austrias I've seen/owned/flown including an SHK, used screws to attach the canopy to the tubular steel frame.
Good Luck,
Scott
The tubular steel frame

[firsys]

On Monday, August 14, 2017 at 1:04:16 PM UTC-4, LongJourney wrote:

Do not use screws; they make for stress concentration and crack development.
I installed anew Kestrel 19 canopy using
RTV silcone preceeded by a primer; this gives a slightly flexible bond which alleviates stress concentration.


JMF

35 yrs later the Kestrel is still flying.

[Scott Williams]

With due respect to JMF,

Schempp-hirth blueprint drawing number L-258, dated April 4, 1965, which identifies fifty countersunk flathead screwdriver headed screws "DIN 7509" securing canopy transparency to the tubular steel frame.
these screws are further described as 2.9x9.5 mm in size.
This particular design print is for an SHK, but all the "Austria" iterations used the same securing plan. I have never see a kestrel in person, however, most Schweizers canopies are secured with threaded fasteners, of course, if someone is performing maintenance the original type certificated method should be used whether it is adhesive, screws, or whatever.
Considering the O.P. has a fastening problem now, perhaps the original fastening design could be useful. Canopy transparencies are incredibly expensive and not readily available, and so, demand reliable installations, not something that might or might not work.

I apologize in advance if anyone takes offence, I'm just trying to be part of the conversation and be helpful.
Cheers And Good Lift!
Scott w.

[Peter Whitehead]

I have replaced a few Slingsby Skylark and Dart canopies.They also used countersunk flat headed screws, but into wooden frames. The trick is to drill the holes slightly oversize and bed the canopy onto a sealant which doesn't have huge and permanent bond strength. You just might want to use the frame again, as I did. Not metal tubular frame, but of similar vintage. Pete

[Scott Williams]

On Sunday, August 20, 2017 at 4:18:33 AM UTC-5, Peter Whitehead wrote:
> I have replaced a few Slingsby Skylark and Dart canopies.They also used countersunk flat headed screws, but into wooden frames. The trick is to drill the holes slightly oversize and bed the canopy onto a sealant which doesn't have huge and permanent bond strength. You just might want to use the frame again, as I did. Not metal tubular frame, but of similar vintage. Pete

Pete,
You are right, the Austria canopy frame is a welded up complicated item including locating pins and a plunger latch mechanism which is a Huge pain in the butt to fabricate!, The loss of which might prove itself close to impossible to replace.

Scott.

[LongJourney]

On Sunday, August 20, 2017 at 4:18:33 AM UTC-5, Peter Whitehead wrote:

> I have replaced a few Slingsby Skylark and Dart canopies.They also used countersunk flat headed screws, but into wooden frames. The trick is to drill the holes slightly oversize and bed the canopy onto a sealant which doesn't have huge and permanent bond strength. You just might want to use the frame again, as I did. Not metal tubular frame, but of similar vintage. Pete

Thanks, Scott. I have located said drawing and see that it was originally fastened with countersunk screws. I also heard from another Austria owner who told me that his canopy was fastened with screws. In addition, I scraped away some of the rubber black stuff on the frame and there are holes about every 4 inches. I have ordered screws and an acrylic drill bit from AS. I plan to drill the holes in the plexi a bit oversized to reduce stress and allow for expansion and contraction.

Thanks for all the help.

[uncl...@ix.netcom.com]

I have installed about 20 canopies using screws. I NEVER drill holes. I create the holes using a rotary tool (Dremel) with a cone shaped diamond cutter about 1/8 inch in diameter. Gently pushing the spinning cutter does a combination of cut and melt that makes a good hole and does not create the issues that lead to cracking when a drill is used. After the primary is through, I walk in a circle to increase to final size. If flat head screws are used I make sure the primary hole is a little oversize so that when I countersink I don't get to a sharp edge on the far side. I countersink with a "normal" countersink that is sharp. I use low pressure and back up the plastic so I don't stress at the hole.
FWIW
Good Luck
UH

[Peter Whitehead]

I have been very careful and lucky with drilling holes, but yes, this way sounds good advice, I shall use my Dremel in future!Pete

[Charlie M. (UH & 002 owner/pilot)]

Key to drilling most plastic is to NOT use a new sharp bit. The cutting edge sharp corners leave grooves (stress risers) in the hole.
A "grinding bit", or burr "melts" its way through.
A dull twist drill may work.
A new bit where you drag a stone across the cutting edge (parallel with the bit long axis) to dull the edge (more of a round scraper than a bit that cuts) can help. Look at the "cutting edge" of a cheap masonary bit, same idea.
Back up your hole (small piece of soft wood works) to prevent "threading the bit through" when you get to the far side.
High speed and slow feed rate also help.

Practice on scrap plastic (you can buy small sheets of 1/8" acrylic at a hobby shop or Home Depot in the US). Cheaper than breaking an expensive canopy.

[Craig Funston]

Specialty bits for plexi are available.
http://www.eplastics.com/plexiglass_lexan_plastic_drill_bits

Craig
7Q

[Brad Alston]

firsys;954019 Wrote:
> On Monday, August 14, 2017 at 1:04:16 PM UTC-4, LongJourney wrote:-

> I've done a search in both RAS and on the web but I'm not finding the

> information I'm looking for...
>
> Jeff-

>
> Do not use screws; they make for stress concentration and crack

> development..

> I installed anew Kestrel 19 canopy using
> RTV silcone preceeded by a primer; this gives a slightly flexible bond
> which alleviates stress concentration.
>
>
> JMF
>
> 35 yrs later the Kestrel is still flying.

I've been pondering the information on this thread and came up with the
following questions:

1.) Does the adhesive approach work for non-molded canopies/windscreens
(e.g., flat wrapped)? ...given there would be a tendency for the
material to "snap" back to its original flat shape.

2.) Does the type of adhesive matter for different types of material?
..acrylic versus polycarbonate.

Thanks for the thoughts!

Brad.




--
Brad Alston