July 2013 Archives

Work has been absolutely killing me lately.  I've been working 7 days a week with almost no days off since February.  I haven't touched the project in over 6 weeks, but I took a little break today to work more on the lower cowl bottom hinges.  The pins have been really hard to install for a couple of reasons.  First, as I mentioned before, it's just really awkward.  There's very little room to get your fingers in around the exhaust pipes to manipulate the hinge pin.  The goal was to make it possible to remove the cowl without any tools, but I was having to use a scrap piece of hinge pin to push or pull on the pins.  Second, there was a lot of friction making it really hard to install or remove the pins.  I figured that if I could reduce the friction, maybe I wouldn't need the scrap hinge pin.  I tried lubrication, but that didn't solve the problem.  I spent some time adjusting the hinge eyelets which helped a bit, but it didn't fully solve the problem.  I decided to try drilling out the eyelets by about 0.010".  I got one side done, then broke the bit off in the hinge.  I tried for awhile to remove the broken bit before giving up.

Given how much of a pain in the ass installing and removing these pins has been, I've been questioning my decision to use hinges here.  Although the goal was to be able to install and remove the cowl without any tools, I still needed a philips screwdriver to remove the side hinge cover plates.  The broken bit pushed me over the edge and I decided to remove the hinges and use Skybolt 1/4 turn fasteners on the bottom of the cowl.  I drilled out the hinges on the firewall along with the retaining clips.



I also drilled out the rivets holding the hinges to the cowl and then popped it off.  The hinge was installed with epoxy/flox, so I was worried that I wouldn't be able to separate it from the cowl.  This was fortunately (or unfortunately) a lot easier than I thought.  Once I got one end separated, I could work a screwdriver under the edge and progressively pop it loose.  I now just need to figure out which Skybolt parts to order.



The Skybolt VLoc fasteners come with preformed and drilled flanges.  I drilled these to the firewall and countersunk them.



Here they are installed on the firewall.  I still need to drill the holes in the cowl and then I can install the receptacles and studs/grommets.



I riveted on the flanges and then riveted the receptacles in place.  You can see a small black tab at the top of each one, that's the anti-lock pin that allows the receptacle's adjustment mechanism to turn freely.



Here's a closer look at one of the receptacles and the anti-lock pin.  You can see that the pin is holding the spring out which allows the inside portion to turn.  It's threaded into the outer housing so that you can adjust the receptacle for different panel thicknesses.



With the grommets and studs installed in the cowl (and held in place with thin o-rings for now), the studs can be locked into the receptacles and then tightened until they're flush with the grommets.  This compresses the spring on the stud which provides sufficient clamping force to prevent the stud from unlocking from the receptacle.  After I adjusted the studs so that they were flush with the grommets, I removed the cowl and then removed the locking pins so that the receptacles can't move.



You can see that this results in a nice flush fit for the stud.  You can also see in this picture that the cowl is now a little bit recessed below the plane of the lower fuselage skin.  I still need to add some filler to this area to smooth out all of the filled rivet holes.  If that doesn't bring these into perfect alignment, I can always add a shim to the flange to space the cowl down a bit.  Overall, I'm really happy with how these turned out and I think I will like this approach far better than the hinge pins I originally went with.



More Cowl Fitting

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Work is still keeping me pretty busy, but I put in an hour or so tonight.  I first reassembled the cowl to see where I need to do some further sanding.



I spent a little time on the side joints to get them as flush as I can.



I also opened up the gap between the cowl and firewall all the way around to 1/32".  I don't know for sure if this is a sufficiently large gap for paint, but I can always open it up further before taking it to the paint shop.



I opened up the gap between the upper and lower cowl to 1/32" for now.  I ended up using a scrap of 0.032" aluminum as a scraper which worked great.



I also applied a couple of coats of epoxy on the outside of the lower cowl to seal it and fill the pinholes.



I decided to install an oil separator to keep oil off the belly, and the unit from Anti Splat Aero seems to be the best unit on the market.  I ordered their install kit which comes with everything needed except a couple of bolts.  I first removed the plug in the side of the engine just in front of the propeller governor pad.  I installed a reducer then an AN823 elbow.  The kit comes with an AN822 elbow, but there isn't enough clearance from the engine mount to install that.



I ordered the polished aluminum oil separator, but the aluminum mounting bracket looks pretty rough next to it.



I purchased an aluminum polishing kit from Harbor Freight awhile back, so I broke that out and polished up the visible parts of the bracket.  The picture is pretty crappy, but this looks really nice.



I drilled the bracket to the firewall and Jenn helped me bolt it in place.  I then fit a short section of the included silicone hose from the breather fitting up to the intake on the oil separator.



I mounted the separator as high and as far to the right as I could so that it clears the oil filter and it won't interfere with installing and removing the top hinge pin.  Unfortunately, that plus the wrong elbow means the included oil return line is too short.  I'll call them tomorrow and see if they can send me a longer hose.



I pulled off the #2 exhaust pipe and drilled a 3/4" hole in the top.



The vacuum valve mounts on the exhaust pipe like this.  The slight angle pressurizes the line so that only higher pressure from the crankcase will push gases into the exhaust pipe.  This has a reed valve inside that only allows flow from the crankcase into the exhaust pipe and not the other way.

Update: This is backward; the opening should face towards the tail end of the exhaust pipe.  This was fixed long before first flight.  As always, please read the directions and don't assume I know what the hell I'm doing :-), yada yada yada...



The output of the oil separator goes straight down the firewall.  You can see that it just clears the oil filter.



The drain line goes through a clamp on the firewall and then into the vacuum valve.



This location for the vacuum valve easily clears the engine mount, exhaust support straps, brake line and starter cable.



I've felt like crap most of the weekend, but I wanted to wrap up the oil separator mount.  I used some contact cement to glue some pieces of baffle material on the mount.



I then used a piece of heat shrink tubing to cover the band on the clamp to keep it from scratching the soft aluminum on the separator.  After this, I used some safety wire on all of the worm clamps.  I should have the longer oil return line from Anti Splat Aero this week and then this will be wrapped up.



Anti Splat Aero sent me a longer oil return line that worked out perfectly.  I replaced the adel clamp that was holding the the two ignition lines with a larger one that could also hold the oil return line.  I shaped it slightly to better hold the lines.  The oil return line goes under the oil filter mount...



...and comes out near the mag and then goes up to the oil separator.



I also finished sanding the bulk of the lower cowl.



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This page is an archive of entries from July 2013 listed from newest to oldest.

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