More Cowl Stuff

I can't put it off forever, so more cowl work today. Putting the top back on, of course it doesn't fit the same way it did before.  Part of that is my mistake - I should have left it on while trimming and fitting the lower cowl.  I thought my jig would be good enough to hold everything in position, but now with both on, the top cowl doesn't set at quite the same angle as before (because of how it fits the bottom cowl at the nose).  The right side at the fuselage line is fine, but the left side will probably need some additional fiberglass work to extend the edge a little.

I continued to slowly shape the nose, although a rough fit is about all I can hope for right now.  Once I get the whole setup in place on the fuselage, then I will do all of the finish work.

You can see just how off all the basic shape is.  The front of the cowls at the spinner aren't vertical.  I guess I'll have to sand and fill the nose bowl area to make it parallel to the spinner.

Here's the left side of the top cowl.  This fit perfectly without the bottom cowl on, but now since the front doesn't set down on the bottom cowl very well, the rear is pulled away.  I will chip away at the front to let the top set lower and pivot the aft edge back, but I don't know that I can do it enough to close the gap completely.  I'll likely need to add on some fiberglass to extend the edge a bit.  I didn't get a picture of it, but I also cut the top edge of the bottom cowl so it would mate up with the horizontal edge of the top cowl.

All of that doesn't seem like much, but took most of the day.  On the fuselage side of the cowls, the last thing I need to do is create the attachment for the bottom.  Van's calls out screws and nutplates for this area, but I chose to go with Skybolt quarter turn fasteners instead.  Much more expensive, but also much more convenient.  Half of the Skybolt is riveted to the fuselage ledge (on the bottom of the firewall), and then a quarter turn screw goes through the fiberglass.  I laid out all of the locations and drilled the holes for the Skybolts.  I started riveting them in place, but after messing up about 50% of the rivets, I decided to call it for the day.  The rivet holes in the Skybolts are super close to the barrel, making it very difficult to get a squeezer or bucking bar on them.

Rocker Gaskets & Bottom Cowl

I prematurely put the baffles on the other day, so I pulled them off again so I could finish up the cowls.  While I had the #3 cylinder baffle off, I decided to proseal around the outlet for the scat tubing that goes to the heat muff.  It doesn't actually need proseal, but the screen that I have riveted in between the pieces has jagged edges that stick out.  I just figured I'd cover them up with proseal so I don't stab my finger one of these days and draw (more) blood.

I've read that it's not if, but when, cork rocker cover gaskets leak.  I decided to just go ahead and swap out the cork for silicone while everything is nice and clean vs waiting for an oil leak.  Other than spending an hour searching for a screw I had misplaced, this was straight forward.

I tried pretending the cowl didn't exist anymore, but back to the nightmare of the Van's fiberglass.  Next up is getting the lower cowl fit to the fuselage.

The biggest problem I had with the lower cowl was just the difficulty in supporting the aft edge while taking it on and off, which I did 100 times.  A couple of blocks of wood on a floor jack helped a lot.  I had previously trimmed off a bunch of the bottom to match the fuselage edge, but still had to chip away a little at a time to get it closer so the whole cowl could set in the right place so I could do the side hinges.

Once the bottom edge nested up against the fuselage, I measured out the sides and cut them off (just like with the top cowl, I drew a line on the fuselage 2" from the skin, then translated that line onto the cowl).

Not a huge surprise that the quality of the part means that it doesn't lay flat on the bottom.  It'll improve a bit once I put in the quarter turn fasteners on the bottom, but I have a feeling I'm either going to have to be okay with a less than perfect bottom side or spend quite a bit of time messing with adding/removing fiberglass to flatten it out.

I laid out and drilled the holes for the side hinges.

The left side went well, but the right side bit me a little. I pulled the cowl tight to the fuselage using tape (leaving a small gap), then drilled the hinge.  Once I pulled the tape off, the cowl sprung forward though.  There is just enough give in the hinges that it can slide forward 1/16", which is enough to make a pretty unsightly gap.  I'll have to see how it all works out once I connect it to the top cowl. If the relaxed state means a bigger than ideal gap, I'll have to add some fiberglass.  I'm going to have to do that on the bottom anyway.  My fit to the fuselage on the bottom is pretty uneven and needs some added fiberglass on the edge.  Thankfully, there's really no mistake in fiberglass work!  Pretty much everything can be fixed.

Baffles

I'm back at the point where I need to get the baffles fit to the cowl.  I'm really not quite sure what order to do things in yet though.  I thought I was ready to put the baffles back on so I can trim them to fit the top cowl.  After putting them back on, I realized that may have been premature though.  I can't really set the top cowl in place and get a good reference trim line on the baffles.  I think what I might have to do is go back to fitting the bottom cowl, so then I can put it in place and prop up the top cowl 4" or so above it using blocks.  That way I would be able to reach inside and scribe a line on the baffles referencing the top cowl.  Essentially, what I'm trying to do is get a scribe line a known distance below the top cowl so I can then trim the baffles to be about 1/2" below the cowl (the flexible baffle material will take up that gap).  So I think the baffles may have to come off again so I can revisit the lower cowl fit.  Two steps forward, one back.

One thing I did get accomplished though - I've been waffling on whether I should paint the baffles.  While they would look nice initially, I think they would probably get beat up pretty fast and look kind of ratty after a few years.  The parts were already kind of scratched up just from test fittings, so I scuffed them using scotchbrite to see how they'd look if I left them bare.  I think the scuffed aluminum looks fine.  I'm just going to leave them as-is.  If I were building a show plane that I planned on removing the cowling of all the time to show people finely polished engine screws, then maybe I'd feel different.  But for a functional plane, the scuffed aluminum looks good.

Control Cables & Alternator

Work has kept me away, so I haven't had much time to spend on the plane.  A while back, I realized that the Van's spinner setup won't work with the Sensenich prop, so I had to order a spinner that Sensenich makes.  What a difference in quality compared to Van's fiberglass parts!  These parts are beautifully made from carbon fiber, and at least on the surface appear to be plug and play.  That's a stark difference from the Van's stuff.

I continued to wrestle with the passthroughs for the control cables and finally got them both finished up.  It LOOKS like there's a lot more room to work in there than there really is.  The eyeballs clamp down pretty good on the cables, but I smeared some fire barrier over them anyway just to make sure there's no path for fumes around the cables.

I still have some work to do to protect the cables and clamp them down in a few places, but it's getting closer to being done at least.

With the cables now finalized on the firewall, I decided to get the backup alternator put in.  All of the back and forth to get the extension and different studs paid off.  It finally fits!  That being said, getting the nuts on the bottom side was a nightmare.  I have so far been able to get 3 of the 4 torqued down, but the bottom inboard nut is still a work in progress. The only way I've found to be able to get to it is with a wrench that is ground down and cut in half.  Even with that, I can only get a fraction of a turn at a time.  My fingers were getting sore after an hour of dealing with the alternator, so I called it for today.  I'll finish up tomorrow.

Engine Control Cable Mounts

Next step to getting the control cables sorted is to get them mounted to the panel.  I discovered my "well duh" moment of the day as I started this - I had spent a lot of time the other day getting the cables loosely captured at the firewall using the eyeball passthroughs.  Since these cables are the vernier assist type, the knob end can't really be unscrewed to slide the end through the panel though.  That means they have to be run through the holes in the panel first, then routed forward.  So I undid all of firewall eyeballs and pulled the cables out.  I'm sure it'll be easier to get the eyeballs back on the second time.

The controls don't mount to the panel itself, but use a bracket that drops down from the lip of the panel.  I had painted this bracket back when I painted the panel, but hadn't cut the holes yet since I wasn't sure where the cables would end up.  I figured out the locations I wanted and drilled the holes, including a hole for the oil shutter cable that I'll route once I get back to working on the baffles and oil cooler.

I sprayed the same matte clear coat on the bracket as is on the rest of the panel.  I decided to put the 3M paint protection film over it as well.  I don't love the look of it since it makes it glossy, so I may end up taking it off at some point (it's nested under the panel though, so you don't really see it all that well anyway).  I just figured the paint could get a little beat up since the controls get used a lot during a flight, and the film does a good job of protecting it.

The cables also need to be captured at the subpanel to keep them from moving around.  There's a similar bracket that attaches to the subpanel, with adel clamps for the cables.

It's a little tough to see, but the bracket is riveted to the face of the subpanel and extends below it.  Since I put off attaching this for so long (not knowing where the cables would set), I couldn't use solid rivets and opted for pulled rivets instead.

Here you can see how the cables route from the panel up to the firewall.  The throttle and mixture have to cross over each other, since the throttle needs to be in the standard position on the panel but the throttle body on the engine has it on the opposite side.  I will see if I need other supports for the cables after I've attached them at the engine and gotten the eyeball passthroughs back in place.  These cables are a bit longer than is necessary, so there will be some curves in the routing that wouldn't otherwise really have to be there.  That's a small price to pay, given the huge price I didn't have to pay to knock off an inch or two for custom length cables!

I need to go to the store to grab a couple of 10-32 jam nuts for the bearings on the cable ends before I can finish up.  I'm sure I probably have some somewhere, but I sure can't find any.  In the meantime, I pulled the 3M fire barrier back out and ran a bead around most of the firewall edges.  The only reason for this is to seal the stainless foil at the edges so the fiberfrax doesn't get compromised if there's an oil leak or something.  That fire barrier is nasty stuff! Sticky!  It is really tough to make it look clean and nice given how much stuff is in the way at this point.  If I were to do it all over again, I'd probably skip the extra fire barrier layer, just because of how much of a pain it's been.  It's added a ton of time and complication.  I suppose the messy look of it and the annoyance of adding it won't seem like much should I ever get into a situation where I need it though.