Fiberglass the Cowl

The fuel hose from the fuel flow sensor outlet still needed to be clamped to the engine mount.  I did that and also connected the wires for the sensor.

I made the rough cutouts for the louvers yesterday, but they still needed to be finished up.  I sanded all of the cutouts smooth and countersunk the rivet holes.  I'll probably wait to rivet in the aluminum pieces until I'm done with everything else on the cowl and it gets a coat of epoxy primer and paint to seal the inside.

I can't drag my feet any longer - it's time to tackle the awful fit of the cowl.  I wrote a bunch of notes on the cowl in an attempt to remember what needs to be done.  Here are all of the reference pictures for me.  Nothing interesting to see other than how ugly the cowl fits out of the box.

I mixed up a full cup of epoxy with flox and a little cabosil.  The flox is for structural strength, and the cabosil is simply a super light filler whose purpose is to help keep the epoxy from slumping with gravity.  Flox doesn't spreads very smoothly, so I know I'm going to have a lot of sanding in my future.  I tackled the right side vertical edge by sanding a scarf and adding flox so I can ultimately extend the edge about 1/16" to fit the firewall.  The lower edges that skybolt to the fuselage pucker out (have to be sucked up against the fuselage) and need to have more material to allow me to sand them even with the fuselage, so I added 1/8" of flox to the inside.  That will allow the inside to set against the ledge of the fuselage and give me enough meat so I can essentially taper off the original material on the outside.  I also added meat to the inside of the bottom corners (the round corners of the fuselage) so I have more material available to sand the outside to match the fuselage curves.  The front portion of the cowl is going to take the most work.  Matching the top and bottom cowl will be a lot of iteration I think.  I built up a lot of the areas that currently have gaps, then I'm just going to have to slowly chip away at sanding them to fit.  I don't expect to get perfect with the flox.  Once I'm close, I'll be able to fill in the small gaps and smooth it all out using micro.  Flox is very hard to sand and shape, but it's strong.  Micro (small glass balloons) is not nearly as strong, but much easier to sand and is what is usually used for the vast majority of fiberglass finishing.  Once the main shape is better, I'm also going to have to use glass cloth to fix the nosebowl flanges.

The cowl is going to take a day to dry, so in the meantime I started working on the rear window.  It's still too big and needs to be cut down to size.  The first thing I did was prop the front canopy up a little and scribe a line so I can make the first cut to get it parallel to the front.  I think Van's usually recommends something like 1/16" gap, but I'll probably do about 3/32 or 1/8".  I've heard of guys getting stuck canopies if they make the gap too small and the plexi swells because of heat.  1/8" sounds like a lot, but I'm 99% sure I'm going to do a fiberglass targa strip over the back edge of the canopy, which will cover the gap.  The targa strip is just a fiberglass/carbon fiber strip that goes from the side canopy rails, over the top to the the other side rail.  It's not commonly done, but from what I've read it provides a tremendous amount of stiffness to the canopy.  As is, the canopy flexes/twists pretty bad when lifted open and closed, making it super easy to catch the right side plexi corner on the roll bar when lowering it closed.  Do that too quickly or accidentally drop it and you've got a broken canopy corner.  The targa strip will also help me smooth out the uneven gaps on my side rails.