Tuesday, February 25, 2020

Forward top skin access panels

This is another of those informational posts.  Tonight I finished installing one of two forward top skin access panels.  I've found during my short 5 years of maintaining my 9A that easy maintenance is the key to successful maintenance.  For example I used quarter turn fasteners all the way around on my cowling including the horizontal split line.  I'm very glad I did that simply because those quarter turn fasteners are much easier to remove than the hings pins.  They don't look quite as clean but I really do like the looks of them. 

Along those lines Van's recently released a kit to install access panels in the forward top skin so that you can gain access to the most forward bay of the instrument panel.  While I don't have much for electronics in those bays I do have two voltage regulators, the GEA 24 engine monitor, and a bunch of wires that pass through to the engine compartment.  All of those items will require some sort of maintenance at some point.  So, I decided to purchase the new kit from Van's and rather than install it in the center bays of top skin, I installed it in the side bay.  This is where the majority of the access will be required and its much easier to reach into this area from a side access even if I have to reach over to the middle bay.

Below are a few pictures of the install process...

Using the tabs provided I clecoed the backing ring to the top of the skin and drew out the two openings to make sure everything would fit nicely. 

Here is the skin with the cutout completed and the backing ring cleco'd in place.

Now I'm getting ready to match drill the screw holes up to the proper size.

After a couple of hours of filing, dimpling, and riveting the backing ring is finally installed.  If you look through the hole you can see where my backup voltage regulator is installed.  Its now much easier to get access to that location.

Same hole but looking forward to where my firewall penetration for the wiring bundle will be.

And finally I screwed the cover in place.  I still need to trim the lower edge of the cover down a bit before paint but overall the kit fits well and I've spent about 4 hours working on an access panel that will provide me many hours of maintenance simplicity.

Monday, February 24, 2020

Window installation procedure -Silpruf method

I've been working through the side and door windows using the Silpruf method I mentioned in my last post.  I really like how its turning out so I thought I would document the process in a little more detail in case I want to use this in the future.  If somebody else is reading this I highly recommend you watch the video's at least once and then feel free to use the checklist I created below.

First, you need a few items.

  • SCS2000 Silpruf in the color you prefer.  I used black and will probably use 2 tubes for all 5 windows.
  • Popsicle sticks.  I cut these into thirds to act as "slats" to help hold the window flush with the cabin top.
  • rubber gloves...lots of rubber gloves.
  • plastic squeegee.  Cut into about a 1" edge size.
  • dry erase markers.  Thin edge and best get a few.  I bought a 4 pack on Amazon.
  • Permatex Ultra black RTV (black because I was using black Silpruf)
  • 1/4" masking tape.  (couldn't find the link to what I purchased)


To Do Trim window with a 3/16" gap between edge of glass and recess wall
To Do Sand top edge of glass to form 1/16" rounded edge. 
To Do Sand edge of glass with 300 grit to make a defect free edge
To Do Drill cleco holes in recess to support window in opening.  Approximately every 4-5"
To Do Install window and mark inside edge surface of window where the recess wall ends (with erasable marker.)
To Do Remove window and place outside face down on a white towel.
To Do Apply 1 layer of tape about 1/8"-3/16" from inside edge of line just created.  This is done with 1" tape or larger.
To Do Apply first layer of 1/4" masking  tape such that it leaves the line  fully visible.
To Do Write a small number 2 on the top end of the tape.
To Do Wipe dry erase line off of window with damp cloth. 
To Do Apply second layer of 1/4" masking  tape such that it covers the outside edge of the first layer of 1/4" masking tape by about 1/16".  Mark the end of this tape with a number 1.
To Do Sand inside surface of the window where it will be glued to the frame.  This helps the Silpruf adhere.
To Do Tape the outside surface of the window and back cut to form nice edges.  2" tape is good for this step.
To Do Glue small Silpruf standoffs at each cleco hole (using ultra black RTV)
To Do Apply a layer of Silpruf to the exposed inside edge of the window.
To Do Remove 1/4" masking tape marked with a #1.
To Do Let sit for 24 hours.
To Do Fit window to recess by trimming the Silpruf standoffs until window is flush with exterior surface.  Trimming the Silpruf standoffs with an angle cut seems to work well here.
To Do Tape the outside edge of the window recess such that the exterior surface and the wall of the recess are covered.
To Do Tape the inside edge of the window recess and back cut the tape to provide a smooth edge 
To Do Ensure all exposed areas that might get Silpruf on them are protected with tape or paper.
To Do Drill out cleco holes if inside tape covered any of them.
To Do Apply a thin layer of Silpruf to edge of window that was revealed when tape #1 was removed.
To Do Apply generous bead of Silpruf to the window recess.
To Do Install and cleco window with clean wood straps.
To Do Using small squeegee clean the excess Silpruf from both sides of the window.  Leave the 3/16" gap empty for now.
To Do Remove tape marked #2.
To Do Remove cleco's one at a time pulling up the tape that protects the Cabin top.  Clean out under the wood slat, install clean slat and then reinstall the cleco.  Do this for all cleco's.
To Do Let sit for at least 48 hours before removing cleco's.

Here are a few pictures of the process.  Some of these have already been posted on this blog.

Trimming window to fit recess opening.  Note the 3/16" gap around the edge of the window.

Fitting window with Popsicle stick pieces to keep it flush with the surface of the cabin top.

Small Silpruf standoffs glued to the cabin top at each cleco hole using Permatex Ultra black RTV.

Outside edge of window taped off and back cut flush with the window edge.  Its actually not flush because I held the razor at an angle so that the 1/16" rounded top edge would not be covered.

Inside surface of window with all three layers of tape as well as the gluing surface sanded with 120 grit for adhesion purposes.

Last layer of tape with the #1 annotated on the end that I will use to pull the tape up.

Outside surface taped and fiberglass protection.  As noted in my blog post I need to add more protection to the top edge as I found my hand touching the fiberglass during the clean up.  

Window installed after applying a generous bead of Silpruf and then cleaning out the excess squeeze out.  In this picture I have also completed the step where the cabin protection tape layer has been removed and the Popsicle sticks replaced.

Inside edge after cleanup/smoothing and tape #2 removal.  I could have removed the green tape as well here but I left it in place so that the Silpruf would dry and it would be less messy to remove.
Final look of window after 2 days of cure time.  Note the nice clean lines on the inside edge of the window.  The outside edge with the 3/16" gap looks messy now but after paint is applied I will come back and fill this gap in with a fresh batch of Silpruf.

Wednesday, February 19, 2020


With the majority of the door work done I've moved on to installing windows.  I'm using the Silpruf method that is documented in great detail on YouTube by Zach Chase.  In this series of video's he demonstrates installing a top window in a Glastar Sportsman.  It runs a bit long but Zach does a great job of going through the entire process.

One item of note about the doors...  I finally got everything back together and found that the pilot door was slightly proud of the cabin top.  Odd, I was quite certain that it was level when I took the doors off for painting.  After a few minutes of scratching my head I realized that I had done all the leveling work without the struts installed.  Those struts put a lot of pressure on the inside of the door which is causing it to flex a little bit.  That means more work leveling this area again but fortunately its not a large area.

Window opening is sanded and small standoff's made of cured Silpruf are glued to the flange with black RTV.  These standoffs were then trimmed by hand with a razor blade to the exact height needed to hold the window off of the flange but remain flush with the cabin exterior surface.

Outside of window is taped and then back cut so that it covers only the top side of the window.

Inside of window is taped with three layers of tape.  First the inner blue tape to act as a nice buffer, the second 1/4" tape that comes up close to the line that marks the flange edge as marked from the inside of the airplane with the window in place.  Then a final layer of 1/4" tape that covers the first layer of 1/4" tape but stands about 1/16" closer to the enge.

You can see all three layers of tape in this close up picture.  You can also see where I lightly sanded the surface of the window that will have the Silpruf layer.

Outer edge with tape and paper protecting the fiberglass around the window.  Paint will not stick to anything that Silpruf touches.  I will admit that I needed more tape on the top side. I thought that would be enough but I found that during the install and clean up phase my gloved hand touched the unprotected fiberglass a time or two.  Fortunately my gloves were clean.

First layer of Silpruf applied.  This is just a thin layer to give a consistent look when viewed from the outside.  It also helps hide the standoffs which can show up in the final product if this layer is not applied.

Window installed, edges cleaned out of excess squeeze out, outer tape layer removed, and inner layer of 1/4" tape removed.  it has to sit like this for at least two days...maybe more because its a little cool in the garage.

Inside view of the window.  You can see where I peeled the last layer of 1/4" tape off.  This leaves a nice clean line of adhesive around the perimeter of the window.