Trent's RV14 Build: 38-19 -> 22: Initial Placing / Trimming of the Canopy

Setting up the Canopy Frame

In order to get the canopy glass onto the aircraft for the first time, the canopy frame needs to be installed into the aircraft and shimmed to be in the correct location. The first step is to make up some wooden blocks to space the canopy away from the roll bar by the correct amount - would you believe that Van's actually sends you a wooden block in the kit? Part number C-10441 - these are made of a natural composite!

I love working with composite materials.

The canopy frame is then placed onto the aircraft and the canopy is latched. The aft frame of the canopy is clamped to the roll bar, and the side rails are shimmed and clamped to the side frame of the fuselage. The aim here is to make the side rails parrallel with the side skins of the aircraft.

The plans come with a template for locating the forward edge of the canopy against the forward canopy skin. This was checked that it was the correct scale, then taped onto the canopy skin.

Gulp! Finally getting out the Canopy from the box!

It was finally time! I cleaned up the shed and opened the garage door, and Dad and I lifted the canopy glass onto the workbench for the first time. I used a vixen file and a canopy scraper to smooth and bevel the forward edge of the canopy, then it was placed onto the aircraft for the first time.

After initial filing wih the vixen file...

The card scraper works great!

After scraping with the card scraper..

After sanding...

The forward edge was aligned with the paper template, then i used the playing card trick to make sure it was even from side to side, and was aligned nicely with the cutout slots on either side of the canopy skin.

Initial Canopy Trimming

I applied some tape aligned with the forward edge of the window shim, to allow me to better see where the canopy aft edge was located. At the rear of the canopy, there was one area which was slightly forward of the tape. I was worried that if the canopy was placed too far forward, i would end up with too mich of a gap from the window. So i made up a 1/32" thick shim and placed this between the canopy and the window shim forward edge in this area. In other areas, the canopy was sitting on top of the window shims, and would need to be trimmed.

Van's accuracy means that in most places, the canopy was only marginally overhanging the window shims.

This spacer was used in the area where the canopy was forward of the window shim, to make sure i didn't position it so far forward that i would not have anything to trim at the back later.

In most places, it was overhanging the window shims (covered by blue tape here), and would need to be trimmed.

This resulted in the canopy sitting perfectly in position at the front.

The card trick was used to make sure the canopy was even from side to side.

And i made sure the canopy was forward enough that it covered the slots - once the canopy sides were trimmed, this gap closed right up.

I then marked the canopy centrelines at the front and the back, as well as marked where the sides of the canopy met the canopy skins - this way i can easily make sure the canopy goes back into the same position.

I was then able to place a piece of tape on the canopy, which aligned with the tape on the rear window shims - this would be my initial cut line.

This is my initial cut line - aligned with the window shims.

In some areas, i already had a 1/32" clearance. These areas were marked and were not trimmed, but rather just smoothed out.

The canopy was then sanded, filed and scraped up to the marked tape line. This initial trim got the canopy to sit down on the roll bar, below the level of the window shims, while being only within the ballpark at the front edge. Once it sat down, it moved forward on the canopy template and would need more trimming.

Refinement of the Aft Canopy Edge

It was hard to accurately trim the canopy in one go - it was an interative process. To refine the edge, i first made up a spacer which was 1/32" thick, and installed the aft window. I then placed a piece of tape on the roll bar that was 1/32" away from the window edge, and then removed the aft window. This tape is where the final position of the aft canopy edge will need to be.

The tape was placed 1/32" forward of the aft window - the place where the canopy needs to eventually end up.

I then placed the canopy back on the airframe, and aligned the centrelines and the marks on the sides, so the canopy was in the same position as before. This gave me a new amount which needed to be trimmed off the aft edge. I once again used some tape to mark this line. The canopy was then sanded, filed and scraped the aft edge to within 1/64 of this line (to leave some fat just in case!).

The canopy was hanging over the tape by varying amounts.

A piece of tape applied to the outside of the canopy, aligned with the tape on the roll bar, showed me how much needed to be trimmed off.

In some places there was almost nothing to trim off...

... and in others, quite a bit.

The canopy was trimmed to within 1/64 of the tape line.

Nicely aligned with the tape line on the roll bar.

Even more trimming required!

The aft window was then installed, and the canopy was then placed back on the frame. I pushed it backward so it was in contact with the aft window, then drew a line along the front edge with a sharp pencil, onto the paper template. It seems the forward edge of the canopy was still 2/32 (1/16) forward of the canopy template, meaning i could still remove some material off the back, To measure this, i made up a little t-square using 2 x 1/32 thick sheets, taped to a longer 1/32" piece. This was used to mark a new tape line at the back, 2/32" in from the aft edge - effectively moving the whole canopy backward.

The forward edge was still 2/32" too far forward.

Used this tool to make a tape line 2/32" in from the aft edge of the canopy.

The aft edge was then sanded to within 1/32" of this new tape line (to give a tiny bit of fat).

The canopy was then re-installed and was pushed backwards against the aft window. I used a 1/64" thick shim between the aft window and the aft edge of the canopy and this put the forward edge right on the correct line of the paper template. The canopy centrelines, and side lines were then removed and re-marked - this will be the final position of the canopy. This will be a little too close to the aft window and the canopy will need a little more trimming - but i will do this once all the screws are installed and the fibreglass is finished.

Right in the correct fore / aft position.

The 1/64" shim was used to position the canopy perfectly, and still gives about 1/64" needing to be trimmed off once the canopy is screwed and fibreglassed on.

Trimming the Canopy Sides

The sides of the canopy extended too far down - past the bend radius of the side rails. So i made up a tool to mark a line on the side rails, which would be transferred to the canopy for trimming later.

Works like a t-square.

I then installed the canopy, lining up all the lines, and used some tape to mark where the sides needed to be trimmed.

I marked "Point Oscar" and a point 3" forward, and chamfered the inside of the canopy as per the plans. I used 3 thicknesses of 1/32" sheet to mark a line on the edge of the canopy to make sure i didn't make it too thin. This was then chamfered using a file.

This was used to make sure i didn't file any thinner than 3/32"

The canopy sides were trimmed using a plastic cut off disc on the dremel, then filed, scraped and sanded to a good finish.

The thicknesses of the canopy were measured at various points along the sides, and it was determined that i will need to use the canopy shims on both sides.