What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Looking for advice - Someone who used Sikaflex on RV10

steve murray

Well Known Member
Looking for someone who has installed RV10 windows using Sikaflex (probably UV 295) Read many posts but not finding the specific info experience I am looking for as it relates to flush mount windows on RV10 front & rear windows. I used Sika on my 8 canopy but this is not comparable to the 10

Thanks

Steve
 
I used Sika 295 on all my 10. I have cracks around the rear windows inspite of using 9 oz. glass around windows. They began after the first 100 degree day. While sika is a great adhesive and used extensively in the marine industry, as it?s name implies it flexes with temp. So much so that one layer of glass could not contain the flex. As for the adhesion properties, I tested several coupons and was unable to separate the plexi from the fiberglass without delaminating the fiberglass or shattering the plexi.
I would not use it again in this application
 
Hey Bill

Would you be open for a phone call? Wanted to get some ideas on the thickness of Sika used and thoughts on using SIKA without fiberglass overlay PM with my phone # sent

Thx

Steve
 
Hi Bill and Steve, if you guys do talk please let us know the result of the thickness question. I am thinking of using Sika on my 10 windows (used it on my 9A canopy with great results so far). I think the flex part of the sika is a good thing since its the difference in the expansion characteristics of plexi vs fiberglass that caused the cracks. Without that flex the stress of different expansion rates gets transmitted to the plexi. If I don't plan on having a covering glass layer affixed to the plexi this should not be an issue (as long as the thickness of Sika is not an issue.)
 
I'm interested as well..

I haven't made a choice yet, but was considering Sil-Pruf, Lord Adhesive and Sika. It would be good to share the research together.
 
I installed all my windows using Sikaflex. I liked it a lot and would use same again. Details of how to do all the steps too long to document, you're welcome to call. Just PM me if interested. DONT glass the window-canopy transition. Run your finger over it while Sikaflex still soft and create a little groove all around.
PS. I used the method described by Jan Hanekom form South Africa, not my own idea.
Best.
Johan
 
I installed all my windows using Sikaflex. I liked it a lot and would use same again. Details of how to do all the steps too long to document, you're welcome to call. Just PM me if interested. DONT glass the window-canopy transition. Run your finger over it while Sikaflex still soft and create a little groove all around.
PS. I used the method described by Jan Hanekom form South Africa, not my own idea.
Best.
Johan

PM Sent. So would the Sika installation you used be similar to the Sil-Pruf method used on the Glasair Sportsman install that I've seen on YouTube? (Essentially, the glass "floats" on the adhesive, with additional adhesive "caulked" around the edges to bring the surface to flush.. No glass overlay.)
 
I used Sikaflex on my -10, The material was very easy to use and had a long enough life to avoid a frantic rush. But there has been an issue with the outside edges.

I installed the windows per their instructions. There is a gap (the joggle)between the outside edge of the windows and the fiberglass. The gap varies and was up to about 1/4" if I recall correctly. I struck the Sikaflex off level with the top of the windows and fiberglass filling the gap with Sikaflex. I then put two or more layers of fiberglass over the gap onto the windows. The results were very good when I was done, however:

Sikaflex cures to a medium hard rubbery texture. The work was done in a temperature controlled hanger in winter so the temperature never went over about 70. Then when flying and with outside temperatures were over 100 a few times on trips, problems started showing up on the outside edge of the windows. It started out with some bulging along the edge that was more apparent because of the metallic silver paint. At first it seemed to come and go, but as time went on it became permanent and the fiberglass started cracking in a couple of areas. It appears to have stabilized out at this time, but it is definitely still there.


Now for my theory of why. The bulging is caused by the thermal expansion of the windows compressing the Sikaflex. It is clearly related to the size and shape of the window and location on the window. For example, the rear window is bulging on the rear curved end and the forward corners. These are the areas where the most thermal expansion of the plexiglass shows. The same is true of the front, the fiberglass has cracked on the lower corner.

So what would I recommend if using Sikaflex? First when installing the windows, remove the Sikaflex from the gap between the edge of the window and the joggle in the fiberglass when it is still "wet". Fill it with a hard filler, sand and then put a couple of layers of glass over the joint. The windows are not large enough for thermal expansion to be a problem. Be very careful in sanding to avoid going thru the fiberglass. Perhaps even using carbon fiber might be better because it is thinner and you are aware if you sand into the fabric.

Would I use Sikaflex again? Perhaps, I don't know what the other materials are like in this regard. I know it is easy to use and definitely will hold the windows in.
 
Dan, you are absolutely right. Wish I knew what I know now four years ago when I used the Sikaflex! If you remove it from the joggle and fill with a filler and then glass to avoid a hairline crack, or tool a grove and then paint over it, it could work.

I have been stareing at my mistake for a long time while building the Rans. Eventually I will just have to fix it, Oregon winters are a great incentive to take on jobs like this. After catching up on the six years on the honey do list I will need a job.
 
I did the installation based on the Sportsman Glasair installation method. There is a well done five part UTube video series that goes over the method of installation. Except for the windscreen, the Sportman has the same flange design as the -10s. The windscreen was easy to adapt to this installation method. There is no fiberglassing on this type of install. Sika flex and Sil Pruf have many simularities, the products allows expansion and contraction, not so good when you are adhering different materials together then fiberglassing over the top. I used Sil Pruf, which is a silicon product and 100 percent UV. The Sikiflex 295 UV is not silicon, can be painted over, it is not 100 percent UV protected. After some research, I discovered this. The SikiFlex 295 UV is used extensively in the marine industry for adhering plexiglass on boats. There had been a number of failures where it was used without a UV protectant barrier. Take a look at any newer boat. You will see a barrier film adhered to the outside of the plexiglass, protecting the Skiflex adhesive. If you were to fliberglass over the edges, the UV will not be an issue. Fiberglassing over the window edges, or doing the Sportsman method, is about personal preference and how you want your airplane to look. Just decide on the look you want and then go for it. It’s the same amount of work either way. But these products may not be the best ones if you glass over the edges.
 
Last edited:
Thanks Rich!

So, how did you do the front windshield, using the Sil-pruf? Vans has you add a great deal of fiberglass overlay for the windshield, to act structurally, but also as a laid up fairing too. If one chooses to use a fiberglass overlay (both on the windshield and the door/rear windows) what product allows for differential expansion between the plexi and the fiberglass, without either cracking the fiberglass or the plexi?
 
The top and sides are the same since you have the joggle/flange. The only difference is the Sportsman has a bottom flange where our 10?s have nothing. I did the same taping procedure demonstrated to use with the Sil Pruf, and taped the outside and inside of the entire window. Then I laid a narrow bed of Sil Pruf down where the bottom of the windscreen would rest on the fuselage, when I set the windscreen in. Since the 10s have no bottom flange it does need something to lay over the top, to mat the windscreen to the upper deck of the fuselage. I opted for the Skunkworks aluminum flange. I did some minor adjustment with a Harbor Frieight metal stretch/shrink tool set. Mounted the flange to the fuselage with hardware, along with a thin layer of Sil Pruf layer between the flange and windscreen. (The other option would be to glass in a bottom flange per the plans). I am very pleased with the looks and results. As far as durability, the plane has been flying since February. Just broke 100 hours. It has been exposed to both the Florida Keys summer and the North Georgia cold. It is holding up exceptionally well. Once the plane is painted, all the channels will be filled in with Sil Pruf. This will give it a finished look. The other nice thing I like is that if a window ever needs replacement, (hopefully never but) it will be a much simpler process then having to grind out and relay fiberglass. I can e mail photos of the installed windows if you PM me your info.
 
The top and sides are the same since you have the joggle/flange. The only difference is the Sportsman has a bottom flange where our 10’s have nothing. I did the same taping procedure demonstrated to use with the Sil Pruf, and taped the outside and inside of the entire window. Then I laid a narrow bed of Sil Pruf down where the bottom of the windscreen would rest on the fuselage, when I set the windscreen in. Since the 10s have no bottom flange it does need something to lay over the top, to mat the windscreen to the upper deck of the fuselage. I opted for the Skunkworks aluminum flange. I did some minor adjustment with a Harbor Frieight metal stretch/shrink tool set. Mounted the flange to the fuselage with hardware, along with a thin layer of Sil Pruf layer between the flange and windscreen. (The other option would be to glass in a bottom flange per the plans). I am very pleased with the looks and results. As far as durability, the plane has been flying since February. Just broke 100 hours. It has been exposed to both the Florida Keys summer and the North Georgia cold. It is holding up exceptionally well. Once the plane is painted, all the channels will be filled in with Sil Pruf. This will give it a finished look. The other nice thing I like is that if a window ever needs replacement, (hopefully never but) it will be a much simpler process then having to grind out and relay fiberglass. I can e mail photos of the installed windows if you PM me your info.

I have been planning a Sika installation with no f/g transition, but noticed your comments about UV protection. I am curious if the silpruf gave you a thick and opaque enough color to look good around the outer 3/4" of the window. I liked Jay's look, but the sika uses a black primer that insures a uniform black color through the acrylic and doesn't seem to rely on the adhesive for a uniform color.

Larry
 
I have been planning a Sika installation with no f/g transition, but noticed your comments about UV protection. I am curious if the silpruf gave you a thick and opaque enough color to look good around the outer 3/4" of the window. I liked Jay's look, but the sika uses a black primer that insures a uniform black color through the acrylic and doesn't seem to rely on the adhesive for a uniform color.

Larry

If your paint scheme goes for the painted black door pillar style then the paint would be the UV protection -

RV-10.jpg


Is the Sika paintable?
 
If your paint scheme goes for the painted black door pillar style then the paint would be the UV protection -

RV-10.jpg


Is the Sika paintable?

My paint scheme is similar. Yes, Sika is paintable, but fear the paint may crack, just like the F/G, due to the Sika's 50% expansion ability. The paint has a decent amount of flex, but not sure it is enough. I am thinking the UV is probably not a big deal for a plane that lives in a hanger most of it's life. The issue with the marine windows is that they sit in the elements 24/7,, year long.

Larry
 
Last edited:
Dorfie refered to me in his post. I have built two 10's using Sika 295 and also helped him do his windows. The trick is not to paint over the Sika and plexi. Then there is no risk of cracking. This is with refence to the four windows. The windscreen is different as you have the bottom section to build up with glass. I do the rest of the windscreen the same as the windows.

By the way - I have had a close look at the Cirrus windows and to me it seems to be more or less the same. They also do not paint over the plexi.

Here is the latest 10 I have done.

XOX_01.JPG
 
Dorfie refered to me in his post. I have built two 10's using Sika 295 and also helped him do his windows. The trick is not to paint over the Sika and plexi. Then there is no risk of cracking. This is with refence to the four windows. The windscreen is different as you have the bottom section to build up with glass. I do the rest of the windscreen the same as the windows.

By the way - I have had a close look at the Cirrus windows and to me it seems to be more or less the same. They also do not paint over the plexi.

Here is the latest 10 I have done.

XOX_01.JPG

Thanks for posting. I found your old posts about your method and that got me hooked :) I like the approach.

A follow up question: How did you hold the window in while the adhesive set up?

Larry
 
Last edited:
Dorfie refered to me in his post. I have built two 10's using Sika 295 and also helped him do his windows. The trick is not to paint over the Sika and plexi. Then there is no risk of cracking. This is with refence to the four windows. ...

So you use the black paint on the door posts and stop at the black sika line?
 
Jan, nice airplane you have... I wish the 10's were like the Cirrus windows. The difference is that on the Cirrus windows, the flanges are opposite from the 10's. All the side windows mount from the inside. The flange sits outboard so the Sika is not exposed. Definitely would be an easier install all the way around. How much UV impacts an airplane that will be kept in a hanger and/or the cockpit covered while outside, who knows. I agree that I would not paint the Sika. Sil Pruf is silicon so you must be very careful not to get it on anything you plan to paint. Sil Pruf comes in Black, Grey, etc. Both can give you a clean look if done right. Larry, do a Google for the install videos for the Sportsman. I watch it a few times, took notes, and it worked out well. It goes over the install and there are only minor differences when doing a 10.
 
At Larry - with a few clecoes. Just fill the clecoe holes with Sika afterwards.

At Fil - you do not have to paint the posts black. Below is a copy of one of my posts in 2014.

Close up from the outside.
JVR_1356B.jpg


Inside showing the close out ring and the black finishing with Sika.
JVR_1358B.jpg


Whole door inside.
JVR_1360B.jpg


whole door outside.
JVR_1361B.jpg
 
At Larry - with a few clecoes. Just fill the clecoe holes with Sika afterwards.

One more question, if you're willing. Did you use any spacers or washers to keep a thick layer of sika between the f/g and window? Not sure it is necessary, as the side gap is probably enough to hold the window in.

Larry
 
No Larry - with a steady hand and the Sika applied with even thickness it works well. I find that applying the Sika onto the windows works well for me. After positioning the windows you squeeze out the Sika untill you see that it has pushed out all the air, just by light hand pressure and a bit of wiggling it. Then insert your four clecoes on the rear window (6 on the front window) and let it cure.
Preparation like masking with two different colours of electrical tape ( not black ) takes a lot of time but is a must to get the right end result.
 
What was demonstrated on the video, you make spacers out of a bead of Silpruf. Best advice is watch the videos on the Sportsman window install. Nothing is left out. You probably can use Sika using the same method. If you want to fiferglass over the seam and window, consider using something like Lords that allows less expansion movement. To fill in the trough, the airplane is painted first then you fill in the trough with Sil Pruf (cannot be painted over at all) and smooth it out flush with the cabin and window edges for the finish.
 
Hi Mike,
With this RV10 the paint shop painted over the Sika. My instructions at the time to them was to paint up to the Sika. As the Sika is paintable it came out ok. But my preference and what I believe comes out nicer is when you paint up to the Sika. Hope it is clear now.
 
Hi Mike,
With this RV10 the paint shop painted over the Sika. My instructions at the time to them was to paint up to the Sika. As the Sika is paintable it came out ok. But my preference and what I believe comes out nicer is when you paint up to the Sika. Hope it is clear now.

Jan,

So, if the paint shop had followed your instructions, the front windshield would have had a "black ring" around it too, except for the bottom edge, which is covered with the large fiberglass structural fairing. Correct?

So....since those pics were from 2014, have there been any cracks (hairline or otherwise) that developed around the windshield, where the painter crossed the demarcation line between fiberglass and sika?
 
Last edited:
I have built two 10's using Sika 295 and also helped him do his windows. The trick is not to paint over the Sika and plexi. Then there is no risk of cracking. This is with reference to the four windows. The windscreen is different as you have the bottom section to build up with glass. I do the rest of the windscreen the same as the windows.

Is the bottom edge of the windshield set in Sika under the fiberglass fairing overlay?
 
Let me try and explain in more detail. I have built three RV10s.

Secondly let me split the tow issues at hand. Windscreen and windows.

The first one (RVI) has been flying since 2010 and I have sold it three months ago. I have that horrible Weld-On on the windows. Applied filler, sanded it smooth and painted over it all. After 8 years of service, there are a few small cracks. Note that I did not do a glass layup over the windows.
On the windscreen I have used Sika, done a glass layup all around, applied filler and smoothed it. Then painted over the Sika line and onto the windscreen all around. To this day no cracks at around the windscreen.

The second one was JVR - the green one above. I have finished it in July 2014 but unfortunately it was destroyed in December 2016. Sad. Here I went for glass layup all around the windscreen and the paint was obviously applied as seen in the pictures all around.

On this one I have opted for the Cirrus look with the windows with the plexi totally exposed. It is here where the miss understanding was. I have asked them to paint up to the Sika and they went over. Up to shortly before the accident, there were no cracks.

The latest and third one was XOX finished recently. Also posted somewhere above. Here we wanted the black posts and obviously this called for a different approach. The windscreen - only glass layups around the bottom and this then painted. The rest of the windscreen painted up to the Sika. On the four windows I have kept the plexi exposed and it was painted up to the Sika line.

Yes Dan the windscreen has been set in a good bed of Sika under the glass in all three builds.
 
The latest and third one was XOX finished recently. Also posted somewhere above. Here we wanted the black posts and obviously this called for a different approach. The windscreen - only glass layups around the bottom and this then painted. The rest of the windscreen painted up to the Sika. On the four windows I have kept the plexi exposed and it was painted up to the Sika line.

Yes Dan the windscreen has been set in a good bed of Sika under the glass in all three builds.

Jan,

Can you post or PM me pictures of the windows on your latest build. I too am interested in black posts and a seamless "one large window" look. Thanks.
 
Hi Mike,
I have sent you a PM a few days ago asking for your email address.
Have not received a reply yet.
 
Hi Mike,
I have sent you a PM a few days ago asking for your email address.
Have not received a reply yet.

Sorry, but I didn't get that PM, or at least I couldn't find it. My email is below. I need to get in touch anyway about your fairings. Shoot me an email at the address below.
ppilotmike at gmail dot com
 
I’m seriously considering using the Sika. I watched the Glastar videos and researched here. He used Silpruf and no primer was required. Is the cleaner and primer a must with Sika?
 
I’m seriously considering using the Sika. I watched the Glastar videos and researched here. He used Silpruf and no primer was required. Is the cleaner and primer a must with Sika?

Yes. I am doing Sika and asked this question of them directly. I don't expect to use half of the primer and cleaner. Would be great if you buy the remaining half from me at 1/2 price. I expect to receive it this week and install windows next week, so should have a good 5 months of shelf life after I am done.

Larry
 
Last edited:
Having looked at a few replies, here is my 2 cents.

I have used Sika on a 7 and an 8 and it has been superb.

It provides a firm yet flexible bond for the plexi onto the sub structure, whether it be aluminium or composite.

Vans offer a very uniform and conservative solution to windscreen bonding using their recommended product, however if you are abroad it causes shipping problems etc etc.

If you look at the Sika product literature, it shows clearly that Sika can be used for bonding organic glass (Plexi) to just about anything short of grass !!!

Sika is a great product to work with and as I have just started a 10, I will be using Sika to bond all our windows in.
 
Back
Top