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Silpruf RV-10 window process

Carl Froehlich

Well Known Member
I’m closing in on how I want to do this RV-10 window install. Current approach is a hybrid:
- Silpruf to install
- A bid of carbon over the top between the glass and cabin top/doors.

Reason being I don’t like the look of the adhesive showing through the glass, and I want the “belt and suspender” approach of using both.

My question for those that have done the Silpruf process, how many wingnut clecos will I need and what size?

Thanks,
Carl
 
Know nothing about silpruf, however, I did use sikaflex on my 10 windows. You need to check into the elasticity of the silpruf. The Sika is over 300% stretch/compressioun and I get a good amount of movement of the window with resulting shape change from concave to flat to convex, based upon the ambient temps. If this also occurs with silpruf, your fiberglass covering will either crack or lift off if you cover that joint. This doesn't happen with the Lord, as it affords very little elasticity and instead the tension is being held in the acrylic.

Larry
 
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Carl,

I think there is a good chance this combination won’t work well.

- Silpruf is silicone based and even a *tiny* amount of silicone residue will prevent a good epoxy bond on the carbon layup. Silicone residue is also extremely difficult to completely remove.

- Silpruf is very flexible and can allow slight motion between the cabin and windows. This is a good thing overall. However carbon epoxy is very stiff and this mismatch has a good chance in resulting in cracks in the carbon/epoxy or disbonds with the underlying window.
 
I just did our RV-10 windows using Sika and estimate I used about a dozen of the 1”clecos to do two windows at a time. Don’t know if the shorter ones will work, but these are what I had. I made small aluminum blocks with an AN960 washer superglued to the block, which was used to clamp the window. All of my cleco holes are outside the perimeter of the window.

 
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I tend to agree with the issue about flexibility - and my just go back to using Hysol instead of Silpruf or Sika.

Either way I would appreciate recommendations on how many wingnut clecos and what size (1/2” or 1”) I will need.

Carl
 
I used a few more than Krea. I used 16 on each rear window and 19 on each of the door windows. I purchased longer clecos but ended up shortening them to work properly. I do agree with the others, expansion and contraction will cause issues if you also fiberglass the exterior.
 
I did not see where I would use wingnut cleco's again. I bought hardware store machine screws and made small wooden blocks to clamp the windows in. I used silpruf first made small spots around the parameter let them cure then with a razor trim them so the window is flush. Worked great.
 
I used 4 or 5 1/8" clecos to hold the window on. I needed a minimum adhesive depth, so CA glued some washers around the holes in the F/G. However, I drilled through the plexi for the clecos, as I covered the seam and window with a high flex filler.
 
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I tend to agree with the issue about flexibility - and my just go back to using Hysol instead of Silpruf or Sika.

Either way I would appreciate recommendations on how many wingnut clecos and what size (1/2” or 1”) I will need.

Carl

This is a challenging decision. With high flex materials, the joint moves around (stretches, squeezes, etc.) to absorb the excess expansion/contraction of the acrylic. With low flex materials, you must insure that the bond strength is VERY high, as the expanding / contracting acrylic will be trying to tear the adhesive free as it tries to move. This is why products like silpruf and sika are the go to products for acrylic window installations, they allow movement and avoid cracking/debonding. Just ask the guys that installed the windows on the CNA building in Chicago (numerous glass windows shattered due to expansion from UV based heat and injured pedestrians walking below). Choose wisely.

Seems the Lord is pretty well proven, as is the Weldon, if proper care is taken in prep. There have been some debonding reports with Weldon, but the limited number implies poor prep as the cause.
 
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I did the Silpruf method and feel it turned out well, haven’t flown yet so no reports on that subject. To the OP, 16 cleco’s worked for me, one window at a time.

Contemplating using proseal to fill the “joggle” instead of the Silpruf. Reason, the Silpruf can be rolled off fairly easily (very strong holding the window) and concerned about rain peeling it up. Sorry if this is a little off subject but wondering if anybody has any experience with this.

Spoke with Van’s and they have no input on Silpruf, with more and more people using it, I wish they would consider some testing on it. Adhesives have changed a lot since Weld-on was introduced…
 
Did it per the Sportsman 2+2 method. Used Silpruf. Did the windscreen the same way, but slightly modified because there is no bottom joggle support for the bottom edge. Turned out great. 3 plus years with no issues. Silpruf is 100 percent silicone and 100 percent UV. Silpruf has more flexibility then Sika. Silpruf is great if you do not plan to fiberglass over the lexan, but I would not use it if you plan to lay fiberglass over the edges. Too much movement for glass.
 
Did it per the Sportsman 2+2 method. Used Silpruf. Did the windscreen the same way, but slightly modified because there is no bottom joggle support for the bottom edge. Turned out great. 3 plus years with no issues. Silpruf is 100 percent silicone and 100 percent UV. Silpruf has more flexibility then Sika. Silpruf is great if you do not plan to fiberglass over the lexan, but I would not use it if you plan to lay fiberglass over the edges. Too much movement for glass.

I'm thinking of doing this; what did you do about the bottom of the windscreen? Did you build a fairing?
 
I pre fit the windscreen to the top and sides of the joggle. Then marked off the bottom run with a dry erase on the area where it edge fits on the airframe. I then ran blue tape about 1/4 inch forward and aft of the mark (add the thickness of the windscreen plus 1/4 inch aft of the mark). When setting the screen, I put down a thick bed of Silpruf between the tape lines, so when I set the windscreen, the bottom edge bedded down into the Silpruf. Once the Silpruf set up to the point where the tape is ready to be removed, you pull all the tape from around the screen to get the clean lines. For my plane I fabricated an aluminum fairing instead of glassing it. I set the aluminum failing with some Silpruf and used #4 SS countersunk hardware with lock nuts. This allows for removal if ever needed.
 
I did the Silpruf method and feel it turned out well, haven’t flown yet so no reports on that subject. To the OP, 16 cleco’s worked for me, one window at a time.

Contemplating using proseal to fill the “joggle” instead of the Silpruf. Reason, the Silpruf can be rolled off fairly easily (very strong holding the window) and concerned about rain peeling it up. Sorry if this is a little off subject but wondering if anybody has any experience with this.

Spoke with Van’s and they have no input on Silpruf, with more and more people using it, I wish they would consider some testing on it. Adhesives have changed a lot since Weld-on was introduced…

As a Glasair Sportsman builder/owner/flyer I will suggest your thoughts regarding Silpruf being rolled off are unfounded, IF you install the windows using the same methodology as is recommended for the Sportsman.

After four years I've had exactly zero issues with Silpruf. I've also had a LOT of positive feedback from those looking at the aircraft. Probably the one most reflective of the overall finish quality provided by this method was the multi-time builder who suggested our windows looked like they were installed in the Gulfstream factory.

It is of critical importance that Silpruf be installed in some consistent thickness in order to ensure bond strength. It is likewise of critical importance that one not use datecode expired product.

By all means follow the instructions laid out in Zach Chase's youtube series; he's Mr. Fibertech Composites and has installed more Glastar and Sportsman windows than anybody would ever consider to be within the limits of a sane human being. While his video series can be slow going, he installs windows at an insane pace because he's done it so many times that it has become second nature to him. He really knows what he is doing so just follow his instructions and you will be learning from the best in the business.
 
Silpruf and paint

For those of you who have used Silpruf, how are you keeping the silicone from contaminating the surfaces to be painted? Or are you painting before installing the windows?
 
When you do the Silpruf method before paint, you leave a ring around the outer edge of the window without Silpruf. After the paint has cured, you come back and fill in this area.

This is all detailed (extensively) in the video series referenced above. IMO Silpruf looks great and has an extensive track record in this application.

Edit - here is the link to the series of videos on using Silpruf to attach windows:
https://youtu.be/A336SG-fsiI
 
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When all is ready, fit the window then scribe the edge of the window around the joggle with a fine tip dry erase pen. Remove the window and blue tape around along the edge of that mark. Once you set the window and the Silpruf has set firmly enough, remove the tape. This will leave a clean edge. As mentioned after painting, then filet Silpruf in the joggles. The joggle fill is cosmetic. I flew for a year before the plane went to the paint shop. Also, when in doubt, tape and plastic all over. You do not want any of that stuff on an unpainted service if you plan to paint it.
 
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I pre fit the windscreen to the top and sides of the joggle. Then marked off the bottom run with a dry erase on the area where it edge fits on the airframe. I then ran blue tape about 1/4 inch forward and aft of the mark (add the thickness of the windscreen plus 1/4 inch aft of the mark). When setting the screen, I put down a thick bed of Silpruf between the tape lines, so when I set the windscreen, the bottom edge bedded down into the Silpruf. Once the Silpruf set up to the point where the tape is ready to be removed, you pull all the tape from around the screen to get the clean lines. For my plane I fabricated an aluminum fairing instead of glassing it. I set the aluminum failing with some Silpruf and used #4 SS countersunk hardware with lock nuts. This allows for removal if ever needed.

Thank you, this is very helpful. Do you by chance have a blog with how you fabricated the aluminum fairing? I was thinking about fabricating a removable fiberglass fairing (some people have done this) but would prefer aluminum (but that seems trickier to make). I want something removable so I can replace the windscreen if necessary without having to re-glass and repaint anything.
 
I pre fit the windscreen to the top and sides of the joggle. Then marked off the bottom run with a dry erase on the area where it edge fits on the airframe. I then ran blue tape about 1/4 inch forward and aft of the mark (add the thickness of the windscreen plus 1/4 inch aft of the mark). When setting the screen, I put down a thick bed of Silpruf between the tape lines, so when I set the windscreen, the bottom edge bedded down into the Silpruf. Once the Silpruf set up to the point where the tape is ready to be removed, you pull all the tape from around the screen to get the clean lines. For my plane I fabricated an aluminum fairing instead of glassing it. I set the aluminum failing with some Silpruf and used #4 SS countersunk hardware with lock nuts. This allows for removal if ever needed.

What are you guys referring to as the “joggle”?
 
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