Painting the inside of the canopy skirt

Bretheren,

I am about to attach the canopy skirt to my canopy and canopy frame with Sikaflex. I have already prepared the inside of the fiberglass skirt with epoxy/microbaloon filler and sanding. I would like to paint the inside of the skirt with the rattle can Ace Hardware (medium gray) I have used for the rest of the interior. Do I need a primer first? Also, when I use the Sika primer before gluing the skirt on, can I apply it over the Ace Hardware paint, or should I apply the Sika primer directly to the fiberglass?
Thanks in advance for your advice and direction.

My thinking is that the Sika primer is really amazing stuff and is the foundation that holds the Sika in place. If you install the Sika primer over paint, then the bond is only as good as the paint is bonded to the surface. I think the bond of the Sika primer is stronger than the bond of the Ace hardware paint.

My .02 worth.

My Vote - No Paint

I plan to do the same but I will not paint the area that the Sika will attach, so that the bond will be the best. I did a test piece of skirt material and it bonds great.

PS, one thing I wrestled with is what paint to use on the inside, the outside paint will meet this interior paint at the edge, I was told that if they were not compatible then you could have an issue. I decided on the expense of PPG paint for the inside of the skirt to be compatible with the outside color (not same color, just same chemistry)

Cheers

I'm wondering if you want to bond the skirt to the canopy or frame at all. The canopy may get bonded to the frame, but skirt to canopy? Seems overkill and down the road should the canopy need replacement it's going to make everything even more difficult. Am I missing something?

Bonding the skirt to the canopy

The fiberglass skirt is attached to the frame and overlaps the bottom inch or two of the plexi canopy. With the "standard" installation, the skirt is blind riveted onto the frame and the rivets go through the skirt and the canopy into the frame where they overlap. I am going to Sika the skirt onto the canopy where they overlap, or else there would be a gap and rain would run into the cockpit.

There has been some great information in these responses. The question remains, however, do I need to prime the fiberglass before spraying on my Ace Hardware medium gray paint?

Thanks!

Priming

I used Sika for my canopy skirt. I also painted it. I agonized over this because Sika expands and contracts, but I wanted a nice finish on the inside. What I did was brush the black primer on the outside of the Sika after it dried (like I did everything that I wanted the Sika to stick to prior to applying). The reason I did this was because I assumed the regular paint primer would stick to the black Sika primer better. I think the results turned out well, but I am holding my breath hoping I don't get any paint cracks where the Sika is. So my unproven answer would be yes, I would prime it (with the black primer and reg. primer -- I don't think it can hurt, though it does add a little weight).

Below is before I put the black Sika primer over the dried Sika at the skirt attach point. I did NOT put anything on the Sika where the top long canopy frame meets the plexi (that is very visible). I sanded that.

This is a pic of the black Sika holding the skirt.
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You can see from the first picture in this writeup how it turned out. I don't have any better pics.

Recommend Priming

I'd recommend shooting at least a light "guide coat" of primer just to reveal pinholes and other imperfections prior to paint.

I would mask off the area you plan to bond (as others have recommended).
I bonded the top edge, and used pop rivets for the remainder of the skirt attachment.

Paige

I bonded the skirt with SIKA. I fit the skirt halves on the plane, and used tape to hold it at the canopy. I used about five holes with clecos to hold each skirt to the lower frame, and some shims between the frame and skirt to fill out the fit and get it to lay just right.
I used plastic and masking tape to protect the canopy, and layers of electric tape right up to the join for the skirt-to-canopy.
I removed the skirts & wiped on the cleaner with blue shop towel, then hand brushed the primer to the bare sanded fiberglass. I wiped the cleaner on the frame. I waited teh required number of minutes for the primer.
I laid in a bead of SIKA along the canopy, and clecoed the skirts on with the shims etc.
Then I pushed gently along the join, until the skirt was very close to the canopy and the SIKA line was uniform and thin. Quickly, the SIKA begins to skin over. Now is the time to pull the electric tape to attain a beutiful join line.
Climb inside the plane and SIKA the frame-to-skirt as much as practical, then get out and close the canopy.
A few days later I removed the shims, and set the canopy with frame upside down on the lawn and injected the rest of the SIKA filling any voids. That way I could shift the work piece around without damage.
What I didn't know about: I didn't know you could soap up your finger tip and sculpt the SIKA surface. Mine looks like a cauking job.
After that, I fiberglassed the tails of the 2 skirt halves together while on the fuselage.
I'll paint the inside after I do some flying....

Caulk job

Scott. You can reapply the Sika right onto the Sika that you don't like the way it turned out. I had to do that several times to get it the way I wanted.

Sika sands great, though you have to be patient. On the areas I had to redue, I would rough it up with 150 grit sand paper. Then I would use a tounge supressor stick again (cut and shaved to the angle I needed) to respread (no black repriming needed again if going Sika to Sika).

I would sand the final in some areas with up to 1000 grit sand paper to get it nice and smooth. Just remember that for painting or sanding or whatever you need to tape off -- do not leave the masking tape touching the cured Sika for long than you have two (a few hours) -- it will make a chemical reaction that makes the Sika sticky and difficult to get the messed up layer off. Dave

Thanks Dave;
Some of the SIKA beads I would like to sand and refinish are in difficult places. Right now I've taken the plane to the airport and put the wings on.
I'm going to put your advice on hold and press on with the primary flight controls and flaps.
As I work thru the challenges I'm dealing with now, I'll develop a plan for sanding the inner bead of the windshield with out scratching the plexiglass....
I'm encouraged that you've worked out a way to refinnish SIKA, and shared it with 'the class'.

Nail on the head

Scott. What you are saying about ensuring the sand paper does not scratch the plexi is very, very critical.

What helped for me was I used about 1/2 of a 5" diameter circle piece of 3/4 inch plywood. I got the sticky back sand paper that comes in rolls (or sheets) from an autobody paint shop and cut it to the 3/4" size so it would be on the edge of the half circle (or half moon). That way I could a) hold it easy b) have less likelyhood of the sandpaper rubbing against the plexi c) use the whole half circle for fresh sandpaper by just rotating it slightly d) not waste any sand paper.

One can make several of these half circles (or pieces of wood of any shape), put them on the sander, and make whatever shape you need for whatever area/angle you need. In some tight spots, I used 1/2" and 1/4" thick pieces of wood. Some of them basically looked similar to the shape of the inside rear of the horizontal stabilizer top fiberglass cap (only about a 2" half circle with a longer built-in handle -- if that makes any sense).

Start out with a rough grit (up to 80 if need be to knock it down if it's real bad) and work your way up. I used mostly 150, then 400, then 800/1000. If something messes up a little (like a whole from where an air bubble was underneath or something), don't stress like I initially did. Just reapply Sika directly on it.

Like I said, the process is slow and it needs adequate time to dry between coats. When you are not using the primer or caulk, put it in the fridge and it will last way longer.

Hope the more detail helps. You can get Sika to look very nice if you take your time with it. Dave