February 2011 Archives

More Work on Baffles

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I drilled and riveted on a support brace to the right aft wall.  It was a mistake to rivet this on now as it makes installing the right aft wall very difficult.  Since this wall has to go on and off a bunch of times before it's on for good, I'm going to drill this brace out.



I drilled the vent attach flange.  This is not the cheesy one that comes in the kit.  Instead, I purchased a single piece flange from Aircraft Spruce.  The hole pattern for the included flange doesn't work, but this will cover the existing holes, so I just drilled four new ones.



Here's the crappy little flange that's included in the kit.  Everyone says these break eventually, so I'm just going to send it back.



I also fit the vent screen.  This will keep bugs and other shit from getting blown into the cabin.



Baffles and Ignition Coils

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I fit the remaining sidewall and riveted the stiffener on the sidewall above cylinder 3.



The center of the aft wall needs a stiffener to brace it.  This is the bracket that comes with the baffle kit.  You can see that it interferes with the installed position of the lightspeed ignition coils.  I'm going to try moving the coils forward so that I can install this bracket relatively unmodified.



I'm going to have to modify this bracket somewhat though since the holes don't line up with the case.



I cut off the aft flange of the bracket.



This allowed the bracket to slip aft enough for the holes to line up.  I'll end up riveting an angle to the aft edge to replace the flange I cut off, but I'm going to wait until I fit the cowl since this might have to get cut down a bit. 



I slipped some bolts into the bracket to see how things line up.  I reformed the fuel line to cylinder 4 to clear the bracket by about 1/4".  I also reformed the steel attach bracket on the right so that it raises up the mounting point for the adel clamp..



I set up a straight edge to get an idea where the top of the cowl will be located.  I'm going to move the ignition coils forward by by about an inch from their original location and raise them up a bit to clear the spider.



I sketched out a bracket on some 1/8" angle stock that will allow the ignition coils to be mounted to two case bolts instead of one.  The aft hole for this bracket was the mounting point for the original bracket.  It's nearly two in the morning, so I'll cut this out tomorrow.



The switch on my small belt sander stopped working, so I had to fix that today.  Fortunately, it was a double pole switch and only one side went out.  I hardwired the neutral through and I'm only switching the hot wire.



I spent about 30-45 minutes cutting out the bracket I drew up last night.  I still have to finish the edge of the lightening hole and drill the top for the coils, but it looks like it fits great.



Here's how the coils will mount to the bracket.  Plenty of clearance all around.



After drilling the holes, I temporarily mounted the coils and hooked up the ignition wires (which I'm sure are in the wrong spots).



Here's a shot from the front showing the vertical clearance.  The wires are at least 1/4" from the spider mounting bracket.  Once they're secured with adel clamps to the push rod tubes, these won't touch anything.  It also looks like I'll have at least 1" of clearance between these and the top cowl.  That should be plenty to prevent these from ever touching the cowl.  Once I'm happy with the fit of everything, I'll paint these brackets the same color as the baffles.



The desiccant pellets on the engine have turned pink a couple of times and I've microwaved them to turn them back to blue.  About half of them however have turned a light orange color and microwaving them didn't turn them back.  I don't know if microwaving them is the problem or not.  I'll try using the oven next time.



I stopped by the new Harbor Freight store near work and picked up a 1kg bag of desiccant pellets for $5.  This should be a lifetime supply of these things.



I refilled the drying plugs on the engine, so I should be good to go for a couple more months.



Anyway, I resumed working on the baffles by bolting the front baffle support to the engine case.



I then assembled and drilled the front right baffle assembly.  Since I have a constant speed prop, I drilled out a 1" diameter hole for the grommet that will fit around the prop oil line.



Here you can see how the assembly fits on the engine.  You can also see that I disconnected the oil line from the fitting in the case.  I put a plug in the line and a cap on the fitting to keep debris out of the line since this will be disconnected until the baffles are installed for good.



I used a set of large pliers to stretch one of grommets around the fitting on the oil line.  When the baffles are installed for good, I'll slide this up and fit it into the hole I drilled earlier.



I shot a little primer on the mating surfaces and riveted together the right front section.



I then installed it.  There's only one screw holding it in place now, so it fits a little loose.



I then drilled and riveted all of the pieces for the left front section (minus the air dam which I installed after this picture was taken).



Fitting this to the engine took quite a bit of reshaping along the inner edge the follows the curve of the case.  It fits really well now and follows the case snugly.



Installed Propeller

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In order to make progress on the baffles, I need to fit the cowl.  In order to fit the cowl, I need to install the prop.  This took much longer than I thought.  There are six bolts that hold the prop to the crankshaft flange, and they can each only make about one turn before they bind and you have to move on to the next bolt.  That ended up taking about a half hour.  What took even longer though was getting the spinner back plate installed.  There is very little room for fingers or tools between the back of the prop hub and the back plate.



Worked on Cowl Clearance

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I finished installing the spinner and then threw the top cowl up to see what kind of clearance I have on top of the engine.  I put a piece of 3/4" thick scrap wood on top of the flywheel to space the cowl up so that it lines up with the spinner.



With the lightspeed coils moved forward and installed on the taller bracket, I only had about 1/4" between the coils and the bottom of the cowl.  This certainly isn't enough clearance.  On top of that, I've decided to install a plenum instead of baffle seals, this means I need even more clearance that I would if I were installing baffle seals.



While I had the top cowl roughly in position, I wanted to see how high the oil cooler could be mounted.  It looks like I can go up to the point that the center hole in the flange is aligned with the upper engine mount tube.



It's hard to see here, but this still gives me about 1/2" clearance between the oil cooler and the cowl (even if I don't relieve the end of the mounting flange a little more).



I took a picture of the rear part of the top of the engine.  Because of the way the cowl slopes, there is a lot more height farther back.



I moved the ignition coils back to the original mounting bracket.



Since I'm going with the plenum, The rear baffle mount doesn't need to be this large bracket since the upper edge of the aft wall will be supported by the plenum itself.  I cut off the forward end of this bracket.



Here's the bracket installed on the engine.  I really need to see if I can find a shorter bolt.  These 1/4"-20 case bolts are a little hard to find though.



Now we have plenty of clearance.  There's at least an inch above the coils now.  I'll probably shoot for having the plenum sit about 1/2" below the bottom of the cowl, so that should provide plenty of clearance between the coils and the plenum.  It's less of an issue if the spacing between the coils and the plenum is tight though since the plenum will move with the engine.



I was getting tired of having to squeeze under the engine to get from one side of the plane to the other, so I took the tailwheel spring off and tucked the tail up tight against the wall.



This gives me almost two feet between the spinner and the garage door; perfect.



While I had the tail spring off, I took the opportunity to get a bunch of the parts ready for powder coating.  Since I'm using the JD Air Parts tailwheel link which only attaches on one side, I sliced off the other arm from the tailwheel linkage and ground the part smooth.



I also stripped the primer from the Bell tailwheel fork so that it can be powder coated.  Afterward, I wrapped silicone tape around all surfaces of the tailwheel parts that I don't want to be powder coated and set them aside.  The tailwheel spring is too big to fit in my little powder coating oven, so I'm going to see if I can drop by a friend's place who has a pretty big powder coating oven and do them there.



I needed to get the joint at the front of the spinner adjusted so that the opening is circular.  Instead of measuring, I just put the spinner on the front of the cowl and adjusted the fit until everything lined up nicely.



I'm using 1/8" spacers between the cowl and the spinner.  The gap is surprisingly good along the top.



The joint between the top and bottom however leaves a lot to be desired.



The left side is a little better, but there's still a noticeable step.  I spent a little time working on the fit, but there is still a lot to do before this will look good.  I'll probably end up making the gap between the cowl and spinner a little larger to start with and I can tighten it up with some fiberglass layups at the same time I'm fixing the fit between the top and bottom halves.


I spent the rest of the night digesting the instructions and plans for the cowl.  This is likely going to be one of the tricker parts of the build.
I stopped by my buddy Corbin's house to use his large powder coating oven.  We powder coated all of the tailwheel components as well as the fuel tank brackets that mount to the fuselage.



The powder coat looked perfect on every part except for the weldment that ties the tailwheel bracket to the spring.  Our guess is that they used some oil or other lubrication when press fitting the brass bushing into the steel weldment.  This oil ran out during baking and caused the finish to fail.  I'm going to clean this off and try again.



Drilled Top Cowl Hinge

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I've been laid up on the couch for the last day and a half with the flu, but I'm starting to feel better, so I'll push myself as usual :-).  I started by clecoing the forward top skin to the fuselage so that I could file the firewall flange back flush with the skin.  This is because the cowl flange butts up against this skin, but it's quite a bit thicker.



I also taped together some pieces of popsicle sticks to hold of the front of the cowl.  This will allow me to adjust the height if necessary.  This is roughly 3/4" thick.



I cut a 44" long piece of the 1/8" hinge material.  I sandwiched a strip of 0.020" aluminum between the hinge and the firewall flange and then drilled the hinge to the flange.  This was slow going since I couldn't use clecos to keep the holes in the skin and the holes in the flange aligned.



I biased the hinge forward slightly so that you wouldn't see the eyelets between the forward top skin and the cowl.



Worked on Cowl Joint

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I loosely installed the fuel tank support brackets, mostly to get the brackets off my bench and out of the way.  These will need to be tweaked to align with the fuel tank brackets once the wings are mounted, so there is no sense torquing these bolts down right now. 



Back to work on the upper cowl, I broke out the die grinder and cutoff wheel and cut out the opening for the oil door.  This needs to be removed now so that you have access to the inside of the cowl when fitting the upper hinge pin.



I cut out a 13" diameter disk of hardboard to use in place of the spinner.  I also cut a spacer that is the height of the firewall that is keeping the aft edges of the cowl the right distance apart.  Even with the joint pulled tight and the flange around the disk as narrow as possible (without looking out of round), there are still small gaps on the outside edges.  I'll end up having to use some flox to make these joints tight.  I also laid a straight edge across the center to see how straight all of the joints are.  They're ok right now, but I'll need to sand these with a long straight edge to get them perfectly even.



Started Fitting Lower Cowl

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I finished adjusting the flange on the front to be perfectly round and then drilled a hole on each side to lock in the position.



The plans specify that you mark a line 2" aft of the firewall flange as a reference point for trimming.  As I've seen several other builders do, I used some 2" wide painters tape.



I laid a straightedge across the top cowl to see how the four flanges lined up.  Three were nicely in line...



However, one of the flanges sits about 1/8" shy of the line.



After doing a bunch of research on cowl fitting, I decided to fit the bottom cowl first.  I started by making a paper template for the gear let cutouts.



I transferred this to the cowl and then cut it out with the angle grinder.



After loosely fitting the cowl halves, I just had to take a picture.  This is looking pretty damn sweet!



The flanges around the inlets needed a little trimming to get the joint tight.  This is pretty close.



After a little further trimming of the gear leg holes, the cowl halves fit together reasonably well.  There's still a small gap down the side, but that should disappear after making the trims along the aft edges.



This is a problem though.  Even if the gap pulls tight, the joint along the right side isn't remotely straight.  I can't cut a straight line here because that would just make the gap even wider.  The instructions (as well as other builder's websites) indicate that the sides should overlap during the trial fitting.  I'm starting to wonder if these pieces weren't trimmed incorrectly at the factory.



The joint on the left side is pretty close to straight though.  I'm going to email Van's tech support and see why these flanges aren't overlapping and what they suggest I do about it.



I re-powder coated the part that didn't come out right last week.  The problem turned out not to be lubricant leaking out between the steel and brass components.  In fact, I had simply not cleaned out all of the grease from the inside of the weldment.  When it heated up, it flowed out and ruined the finish.  I ground off all of the powder coat and cleaned it inside and out before redoing it tonight.  Afterward, I assembled all of the components.  This will stay on the shelf until the prop comes back off.



In order to make sure the cowl returns to the same position each time, I drilled a piece of scrap aluminum angle to the top cowl so that it aligned with the spinner.  The clecos didn't really hold in the fiberglass, so I ended up putting some scrap aluminum on the other side and using some wing-nut draw clecos to anchor this firmly.



I also made a series of marks around the spinner to serve as reference points.



With the cowl in its final location, I put a light inside the cowl and put some masking tape along the cut line.



I did the rough cut with the cutoff wheel to within about 1/16" of the line. After putting the cowl on and off a few more times, I was able to iteratively trim the line with a vixen file so that these edged align with the firewall flange.  I'll trim the exit once I'm happy with how everything is fitting.



While I had the cowl in its final position, I took the time to position all of the exhaust pipes so there was an even gap all around them.  Each pair of pipes will be clamped together and then everything is loosely anchored to the engine mount.  I also made some marks on the pipes that are even with the shortest pipe.  I'll cut all of these so that all of the ends are even.



Here's a shot showing how much clearance I have all around.  I have about an inch of clearance top and bottom and about two inches on each side.  The pipes look like they aren't vertically aligned here, but that's just because the lengths vary.



I drilled and installed the pipe clamps.  The bottom steel straps needed to be bent to conform to the pipes.



Worked on Exhaust Pipes

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After exchanging a couple of emails with Joe Blank at Van's, they determined that my lower cowl doesn't have a long enough side flange.  They're going to send me a new lower cowl, so I'm going to work on a few other things until then.

Since I marked the cut points on the exhaust pipes last night, I pulled the lower half of each pipe and cut the three longest pipes to match the shortest.  I then cleaned up the ends so that there were no burrs and reinstalled the pipes.



I then fabricated the exhaust hangers.  These are each comprised of two pieces of stainless steel tubing connected by a piece of rubber tubing.  I flared the ends of the stainless tubes so that they couldn't slip out of the rubber tube.



Now that the exhaust is installed for good, I installed the heat muff around the #1 and #3 pipes.  This was a bitch to get on since the fit is really tight.  I moved it almost as far forward as possible so that I can get maximum heat transfer as well as provide the most room for the aft SCAT tube.  I could have moved it forward another 1/4" or so, but I wanted to be able to inspect the weld on the #3 pipe during annuals.



Despite moving the heat muff forward, the right exhaust hanger is still going to interfere with the aft SCAT tube.  I'm going to have to shorten the exhaust hangers which will have the effect of moving the upper attach points farther out.  Hopefully that will give me enough clearance that the SCAT tube won't rub on the exhaust hanger.



I remade the exhaust hangers so that I clearance to install the aft SCAT tube on the heat muff.  I ended up shortening each stainless tube by about 2" or so and then re-flared the ends and reassembled each support.  Shortening these caused them to splay out more which is what provided the additional clearance for the SCAT tube.  Another advantage of this is that there is more lateral stability for the exhaust pipes.



Now that the exhaust pipes are in the final spot, I installed the adel clamp on the breather tube.



The lower end is positioned right over one of the exhaust pipes so that any oil blown overboard is burned off instead of coating the belly.



Since the cowl is on hold until I get a replacement lower half, I decided to finish off the canopy.  Next up is to fabricate the side skirts.  I installed a few screws on each side to hold the canopy against the canopy frame.  This had the unfortunate side effect of pushing out the frame so that the side skirts are no longer flush with fuselage sides.  I'll have to gently flatten out the curve in the frame to pull the sides in a bit.



Since I was alone, I needed to be able to reach the screw on the outside and the nut on the inside at the same time.  My arms were long enough to reach the aft and middle screws, but I needed to fabricate a little tool to hold the nut while I turned the screw from the outside.



Since I cut the forward skin back a bit so that the joint lines up with the bend in the longerons, the included skirts aren't long enough.  I used my air nibbler to cut some longer and narrower side skirts.  These are 2.75" wide and about an inch longer that the included skirts.  Once these are fit to the canopy frame, I'll trim the aft end to match the angle of the skin surrounding the rear window.



Drilled Canopy Side Skirts

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I laid out the holes for one of the side skirts, them clamped them together and drilled both at the same time.  The plans show a uniform spacing for each row, but because the rivets are angled back at the aft end to follow the angle of the canopy frame, the plans show a slightly wider spacing for the upper row of rivets.  Instead, I laid out all of the rivets on a 1.5" spacing except for the aft pair in the upper row which are about 1.7" apart.  I also spent a little time trying to plan how I would fabricate the lift handle.  I'm leaning towards cutting a slot in the side frame and skirt and installing the angle from the inside.



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