Wing Tips (2)

I picked up where I left off yesterday and finished drilling both wing tips to the wings.  They both matched up pretty well with the ailerons in neutral.

A rib is riveted into the wing tip to stiffen up the portion that is open next to the aileron.  The rest of the wing tip will be screwed onto the wing using nutplates. There's no callout for where the rib gets placed - I just slid it into the tip until it was snug and fit the shape of the fiberglass.

I laid out the rivets and match drilled the rib to the wing tip.  

Wing Tips

It's hard to show pictures that look any different than the 100 others of the cowl.  I'm still working on the fit of it all.  I'm at the point where I don't think I can get the gaps to their final state without having the hinges riveted on.  Before I do that I want to spray epoxy primer and paint on the interior though - protection from oil and other nasty engine fluids.  There's gobs of work left to do on the fit and finish, but I need a mental break.  I'm going to move on to some other fiberglass.  I now see why it's common for builders to say the cowl was a morale killer for them.  It's a lot like the canopy - every change you make causes the whole thing to shift and need rework.

I'm going to jump over to the wing tips just for a change of pace.  The first step is to mount the  aileron and find its neutral position so the trailing edge of the wing tip can be matched to it.  I loosely bolted the aileron in place and used a jig to set it at neutral (the jig is just a piece of wood attached to a couple of holes in the outboard wing rib that helps indicate the neutral position of the aileron).

The wing tip has a number of areas that have to be trimmed to fit around the aileron hinge brackets, as well as to give the appropriate 1/4" gap between the fiberglass and the aileron skins.

After a number of iterations, I got a pretty decent fit and started drilling the holes into the fiberglass.  The wingtip will be attached to the wing skin with nutplates and screws.  The wingtip extends aft about 1/8" beyond the aileron.  I haven't decided if I care enough to cut it down so it's even - if I do that, it'll be more than just sanding it down.  It'll crack open and have to be closed back up by laying fiberglass on the inside (not easy to reach into that tight angle).

Misc. Odd Jobs

Even though the oil cooler is pretty solid with the added aluminum angle I put on the corner of the baffle, people tend to recommend still adding additional stiffness to the whole setup to keep the baffle from cracking.  One common approach is to add some sort of a brace from the inside edge of the cooler over to a rocker cover screw to essentially create a rigid triangle.  I had some leftover steel tubing from when I made my exhaust pipe hangers, so I decided to use that to create the brace.  I tried and failed 3 times - that tubing was just too thick to get bent at the exact angles needed (not only bent to go from the cooler out to the rocker cover screw, but also bent at a second angle to drop down vertically as well).  I finally gave up and ordered some steel tubing of the same size but half the wall thickness.  Still plenty strong, and bending was much easier.  With that in place, I think the cooler is rock solid to the shaking baffle, and the baffle is solid to the shaking cylinder.  Hopefully that means no baffle cracks.

With Dad here, we started to tackle all of the random work that is a little easier with a second set of hands.  The first up were the leading edge lights on the wings.  We reorganized the shop and pulled each wing out of the stand to lay them down so we could do the crazy part - cutting holes in perfectly good wings!  I didn't get pictures of the process, but after scratching our heads over the instructions (not Van's) to make sure we 100% knew where to cut the hole, we used a template and went to work.  Other than being a bit nerve wracking, it was relatively easy and uneventful.  Then we chopped down the install bracket to fit between the ribs of the last wing bay, drilled holes and installed nutplates for the mounting screws.  The brackets were painted black to help them disappear in the cavity a little better.  Then, using the wing cutout as a guide, we trimmed the lenses that get inserted and are held in place with nutplates and screws.  The lights themselves just drop into the bracket and are attached with screws.  Once the wings are on the plane, I'll have to aim the lights - the bracket has oversized mounting holes, so can be tilted up and down just by loosening the screws.  I'm leaving the lenses off until after I paint.

Next up was the part I'd been dreading - getting the forward top skin riveted on.  This is the last major item to rivet on the entire plane, and probably also the most awkward.  We pulled the canopy off, and after double checking all of the wiring to make sure there wasn't anything else I needed to do before my access to behind the subpanel was covered up, we got to work riveting.  Well, that was after we fought with the top skin just to get it in place.  We ended up having to use ratchet straps to pull in it down tight to get the longeron clecos in.

I laid underneath the panel (bent backwards over the spar carry through - super comfortable!) and bucked rivets while Dad used the rivet gun.  It took a good chunk of the day, but we got it done!  There were a few rivets that were just impossible for me to reach due to where I had mounted some of the electronics boxes, so I ended up using a couple of pop rivets in those locations.

I reinstalled the canopy pin mechanism (I had to take it out earlier in order to buck the rivets along the center subpanel), and we reinstalled the canopy.  I can't say that I look forward to taking the canopy off and on very often!  That might have been the most stressful part of the entire build so far.  It's very difficult to get the hinges to line up with the pins, all the while trying to hold the canopy in position so you don't snag the leading edge skin on the fuselage.  I've read horror stories of people creasing that canopy frame skin and essentially having to rebuild the canopy frame to fix it.  We did manage to get it back on without any damage.

I will still have to crawl back under the panel at some point to put proseal in the gaps of the subpanel to waterproof the seam.  I need to wait for my back to return to a normal shape before I try contorting under the panel again though.  I didn't get a picture, but we also fit some weather stripping to the underside of the canopy frame where it sets on the fuselage canopy rail.

Switching gears, we moved back up to the firewall forward stuff.  We spent a while just staring at things trying to sort out the last bit of fuel hose routing I need to do.  The area is getting so full of stuff that there really isn't a perfect routing to take, but I think we landed on the best option.  We took measurements and I shot them off to the guy who I use to make hoses.  I ordered the fuel hose that goes from the firewall to the mechanical pump, then one from the outlet of the pump to the fuel totalizer, and from the totalizer over to the fuel servo.  I'll get those hoses next week sometime.  Fingers crossed they're the right length.

The hose that Titan installs for the fuel servo up to the distribution spider took some thinking too.  It's the perfect length for their setup of course, but I'm using crossover exhaust, which while it's fairly standard in the RV world, isn't the normal straight pipes option that is on most engines.  What that means is that Titan's planned routing for the fuel line takes it right between the sump and one of the crossover pipes.  There's clearance, but we're talking like 1/4".  I don't know that I could insulate that well enough to not have some heat issues with the fuel.  What we landed on instead was routing the fuel line over the front air intake pipe and down in front of the rear one.  I'll need to come up with a way to adel clamp it to the rear intake pipe.

Next up is the air intake box that hangs below the fuel servo.  The FAB, as it's called, is a fiberglass scoop with a couple of aluminum plates.  As simple as it looks, it took the better part of a day to get it "finished" (not finished).  The top plate is put in place to be able to apply just enough squish of the air filter to keep it in place.  One of the issues I've seen over the years is that the K&N filter tends to shrink over time.  When it does that, it no longer stays squished between the top plate and the fiberglass bottom of the FAB.  Then it starts to vibrate with the engine and eats its way through the fiberglass.  From what I've gathered, as long as you watch out for that and replace the filter before it shrinks too far, everything is fine.

Part of the fiddly nature of getting the FAB set up was getting it lined up with the cowl scoop.  Since the engine is angled and not pointing directly ahead (offset thrust for a host of aerodynamic reasons), the FAB has to be angled back to center to meet up with the cowl center line.  We first bent the top plate of the FAB up to match up to the top edge of the scoop, then did a lot of back and forth to get it centered laterally.  It's still not perfect because of the poorly shaped fiberglass, but it's close enough that I'll be able to match it up when I do the finish fiberglass work.  I have to mold a fiberglass extension to the scoop to bring it aft a few inches and mate up with the baffle material that will be attached to the front of the FAB intake.

Moving on from the engine, we went back to the wings.  The wing tips also get lights in them, although these are position/nav lights, not the landing lights that are in the wing leading edges.  I built these lights from a kit a long time ago.  They are LEDs attached to circuit boards that will set in the wing tips and get covered by a lens.  The circuit boards have resistors and other bits on the back side, so the wing tips need to have cutouts.  We used the provided template and made the cuts.  The circuit boards can be installed using screws, but the company says double stick tape works just as well. So that's what I'm going to go with - got some heavy duty automotive body trim tape.

The "lens" that goes over the area comes as one big piece for both wing tips.  It has to be cut down to size.  That was an iterative process, not wanting to take too much off by accident.  The fiberglass is pretty sorry, making the fit a little harder.  I'll have to do some clean up when I work on the wing tips.  One nutplate and screw on the top and bottom corners will be all that is needed to hold the lens in place.

We needed something fun, so decided to go ahead and get the interior fit and mounted too!  While a lot of the interior just uses velcro strips stuck to the skins, there are a few screws necessary, so I figured we might as well do it now and ensure it fits before I start doing all of the final finish work.  We started with the glare shield trim.  I had already drilled the holes for the screws a while back using the template the company provided. Lo and behold, all holes matched up with the trim except the outermost ones on each side.  It looks like they may have sent the wrong template or something.  I'm going to have to remove the trim and locate where the holes are supposed to be.  It's a little irritating to have extra holes sitting in my new glare shield, but I can probably just 3D print a tiny black plug to cover them up.

The rest of the interior install went very well (minus me managing to break my pop riveter while installing a rivnut).The fit is pretty amazing and the quality is great.  The only thing not shown in the pictures is the front and baggage area carpet and seats.  Once we verified it all fits, we pulled it back and out so I don't accidentally get paint on it when I'm spraying the fuselage.

Initial Wing Fitting

The day for the wing fitting finally arrived!  Dad and I reorganized the garage and maneuvered the fuselage around to the middle to give enough room to put both wings on at the same time.  We strategically placed a few storage bins and blankets underneath each wing and tail to help take some of the weight while we were trying to insert them into the fuselage.

Before we worked on inserting the wing spars to the spar carry through we did our best to level the fuselage.  I was a little nervous about how the wing spar would fit into the fuselage.  There have been a lot of stories online of people who didn't quite get the space correct for the spar carry through area and had to do a lot of unriveting in order to get the spars in.  I was extremely happy to find that the spars slid right in with very little coaxing!  Dad lifted and wiggled the ends of the wings while I guided the spars into position and inserted the temporary bolts.  The rear spar attach gave us a little trouble at first, but we found that we just had to get the fore/aft angle of the wing right to get the rear spar to slide into place.

With the wings in place, the next step was to take a number of measurements to ensure that the positions were equal and within spec.  We measured from the wingtip to the center of the tail - the initial measurement was about 3/16" different from side to side.  A few small taps of the wingtip moved the left wing back enough that the measurements between both sides were almost dead on.  If I remember right, the final difference was less than 1/16".

I don't have a picture of it, but the next job was to check the forward sweep of the wings.  We dropped a plumb bob down from the leading edge at each wingtip and pull a string line between them.  Then we moved each plumb bob to the inside leading edge to see where they landed on the string line.  There was a difference of about 1/4" on the left and a little less than that on the right.  A little tweaking and we got the line to be right on.  With that done, we checked the wingtip to center tail measurement again to be sure it was still good, which it was.

I have to admit, it was pretty cool to finally see the plane with wings!

Surprise surprise, one more measurement!  Following the instructions, we created a block out of a piece of aluminum angle and added some wood and tape to it until we hit the exact size called for.  Then we placed that block on the rear spar line and put a level between it and the front spar.  It needs to be level, and it was right on the money.

With all of the measurements accounted for, it was time to drill the rear spar attach point to lock everything in place.  The edge distance on this part is very tight - to allow for the correct edge distance there is really only one center point that will work.  I used a block of wood as a drill guide to ensure I got the hole perpendicular.

Next up was the front fuel tank attach brackets.  We bent the brackets a couple of degrees (easier said than done) so they would match the angle of the fuselage and still set against the fuel tank bracket.  Similar to the rear spar, these brackets have a pretty small window for edge distance. I drew a little box that gave me the 1/2" edge distance and drilled the bolt hole.

I completely neglected to get pictures of the next couple of tasks, mostly because I was laying on my back under the wings to fit and drill the wing root fairings.  After that, with Perry's help we started fitting the flaps.  We put the flaps on and eyeballed where the pushrod would go through the fuselage to the flap control arm.  I can't say that I loved drilling a big hole in a perfectly good fuselage!  I got the final oblong hole where it seemed correct, even though we didn't set the final length of the pushrods.  I'm waiting on some replacement pushrod bearings before I do that.  I don't love Van's design that doesn't allow for a way to trap the bearing if it were to ever fail.  I ordered some normal pushrod bearings and bolts, and I'll set the flap movement down the road when I final install the wings and control surfaces.

Pitot Install

I got the pitot installed, so now the left wing is done and buttoned up.

Attaching the wiring and tubing was easier said than done since getting through the access hole and then through the rib hole is pretty much a one hand endeavor. 

Left Wing Bottom Skin (5)

The left wing is all closed up, and I have the bruises on my arms to show for it!  The one thing I have remaining to do is put the pitot into the mast.  I'm not sure if that will be easy or not.  I have the aluminum tubes flared and all ready to plug the plastic tubes into, so it just depends if my measurements were right.

Besides the fiberglass tips, the one remaining big ticket item for the wings is to cut the leading edges for the landing lights.  I'll wait to do that until I get the wings out of the cradles - probably when I mount them to the fuselage for the initial fitting.

Left Wing Bottom Skin (4)

More of the same - I spent a few hours continuing my way down the left bottom skin today.  It's all the same as the right wing except for the addition of the pitot.

The pitot mast fits behind the spar flange and in between the skin and the supporting angle on the rib.  Because of the tight fit of the mast through the skin, it was a bit awkward getting it into place.  I couldn't just slide the mast into place because then it would be behind the support angle, and if I put it in the skin first and then lowered the skin into place, it sets on the wrong side of the flange.  I ended up partially sliding it into the skin, then bowing the skin out just enough so I could angle the bottom of the mast so it slid behind the flange.  It was enough of a bow that I got a little nervous about accidentally making it crease!  It worked out fine though.

Left Wing Bottom Skin (3)

Not much exciting to show for today's work.  I got about 3/4 of the top 5 rows of rivets done on the outboard bottom skin.  It went smoothly, minus the same frustration with the rivets around the aileron brackets.  There's just no riveting those without causing skin dings - at least with the tools I have.  It's annoying for me to have to see the dings, even though I know with some filler they will all disappear when I paint.  If I ever build again, I'm going to have to search for a long shank mushroom set to get into these tight spots.

Left Wing Bottom Skin (2)

I braved the 20 degree garage and finished up the inside bottom skin on the left wing.  I hung the other bottom skin, but the warm house beckoned.

Left Wing Bottom Skin

I finally got up the energy to reorganize the shop again so I could get back to riveting the wings.  I strapped up the inside skin of the left wing and started with the rear spar rivets.  It hasn't been that long since I did the right wing, but I was all thumbs with the riveting.  It took a while to get into the groove again.

Once I got down three or four rows, the riveting got a lot easier.  Just like on the right wing, I decided to put in plenty of dings by the flap outside bracket in order to give me more practice with filling before paint.  The inside rivets are just super close to the bracket, and the gun with the normal rivet set won't fit.  I tried multiple different approaches, but nothing really worked.  I had the same issue on the right wing.  I'm sure there is some specialty set I could buy.  Maybe next time.

I was able to get all of the riveting done down to the spar flange.

Center Section Wiring Cleanup

I've been dragging my feet on starting the riveting of the bottom skins of the left wing.  The reason?  The wing was facing the wrong way, making the light bad and access difficult with vehicles in the garage.  Maybe not the best excuse, but that's the excuse I had.  I didn't actually start any riveting today, but I did take the time to move benches and everything else so I could swing the wing cradle around.  I spun it so the left wing is now facing my benches and tools.  Now I have something to do when I need a break from other tasks.

I'm slowly working my way forward with wiring cleanup.  While I think I have all of the wiring pulled that I need, it also won't surprise me if I find out later that I'm missing something.  That will just allow me to continue my ritual of cutting off at least two zip ties for every one I put on.

I glued a cable mount inside the flap motor housing and ran the flap motor power and position sensor wires down the housing and into the center tunnel.

There are a number of wiring offshoots in the center tunnel between the seats (to get to the seat heater jacks and roll trim servo), but it still cleaned up fairly well.

After I got most of the center tunnel wiring done, I reinstalled the roll trim servo.  I also slid the elevator pushrod back into the tunnel.  It's just laying on the floor for now, so it won't be as close to all of the wiring as it looks in the picture.  I need to measure the pushrod again, which is going to take some doing.  The manual shows the length it should be, but you can't actually install it with the end bearings in place.  So I had to unscrew the bearings to get it in place.  It's not possible to get a tape measure on it, so I'll have to go with a string or something.

I've decided to take certain wires out of the terminal blocks and instead just use butt splices when I'm ready to connect the wings.  Most power circuit wires are fine in the terminal blocks, but low voltage data wires are apparently more sensitive to loss, and the terminal blocks can sometimes cause enough noise in the signals to be problematic.  On the left wing, there is only one questionable wire - the pitot heat status, so I pulled that out of the terminal block.  I also took the screws out of the block and added star lock washers to them.

The right wing has more data wires because of the autopilot servo.  In hindsight, it would have been easier to just use a connector of some sort vs the terminal block, but next time I guess.

I originally thought I would just run the antenna coax through the large lightening hole in the seat rib (like the above photo), but I couldn't figure out a great way to secure it.  I could put some edging on the hole to protect the wire from rubbing, but the coax would still be unsecured and vibrate.  I decided to punch through the rib with another hole.  I did this on both left and right sides.  Not shown in the pics, I also glued down a number of additional cable mounts to secure the corrugated tubing.

Pitot Regulator Wiring

I needed a break from trimming the canopy, so I went back to working on the pitot heat regulator mount.  I went back and forth on where to mount it, from just attaching it to the nearby access cover, to building a bracket for it that would run between two ribs.  I want it to be out of the way enough that I can get my hand through the large hole in the rib for pitot access without having to remove the regulator.  The easiest solution is to simply bolt it to a rib web, but in the future when the skin is on and the only opening is the access cutout, getting two hands in to hold bolts and nuts would be almost impossible.  I ended up drilling 4 mounting holes in the rib web just outboard of the aileron bellcrank (the rib between the bellcrank and the pitot mount itself), then went back to the scrap pile and made some nutplate mounts for the back side of the rib.  Nutplates are at least a bit easier than nuts to deal with in tight spaces since once you get them started, you only need one hand.  To simplify things down the road, I riveted the two nutplates together so as soon as one is on, the other is in the right position.  I obviously could have just made it out of a single piece of aluminum, but didn't have anything quite big enough in the thickness I wanted to use.

Since the ribs have the raised edges around the lightening holes, the controller can't just set flat on the rib web.  I had a few inches of leftover aluminum tubing from who knows what, so I cut down 4 pieces to make some standoffs.  

The routing of the wiring to the pitot itself and the pitot and AOA tubing through this rib is still to be determined.

In the meantime, I went ahead and cut wires to length, pulled them through the conduit and spliced them together with the existing regulator wiring.  I put heat shrink on the exposed wiring and ran some RTV around the hole in the conduit to keep the wiggle factor down.  I didn't keep much of a "service loop" on this end of the wiring.  The other end will have some extra length should I ever need to pull things apart.

Canopy Frame Skin Riveting & Pitot Mast

My wing skin was still on the bench from the other day, and since I need the bench space, I figured I should just finish the pitot mast mount. The mast is from Dynon and was designed for the RV7 wing, which apparently has different wing spar rivet spacing. That throws the "just follow the template" approach out the window.  The template assumes you can grab 4 rivets from the spar flange, which sets the base of the mast up against the rib (they provide a small piece of angle to attach it to the rib).  On the RV9, the spar rivets are spaced further apart, so I can only catch 3 of them.  In order to get 3, the mast has to be moved away from the rib, which means I have to fabricate a different way of connecting it.  Anyway, first things first - the template is correct otherwise, so I centered it over the spar rivet holes and laid out the other rivet hole locations as well as the centers of the circles that make up the fore and aft curves.  With that done, it was just a matter of cutting out the big hole for the mast to slide through.  I took the meat of it out with the Dremel cutoff wheel and cutting bit, then hand filed until I had a nice fit.

The base of the mast sets too far away from the rib for a piece of aluminum angle to tie them together.  I needed to extend the angle another inch, so I riveted a piece of thick aluminum to it from the scrap pile. I put the wing skin in place to pull the rib into position, then very awkwardly reached inside and held the angle in place while I marked the location.

I riveted the angle to the rib web.  I won't drill the face of it that gets riveted to the mast base until the skin is in place and riveted.  There's too much movement in the parts without the skin, so drilling holes now would for sure end up being off (the hole that's already in the part is just a hole that was in the scrap piece - I consider it weight savings).

The instructions say to move on to fitting the canopy bubble now, but I don't like the idea of the frame just being clecoed to the skin when I do that.  Not only can things move around, but the clecos sticking up would make scratching the canopy way too easy.  I looked through the plans and couldn't find a reason not to just rivet the skin on first, so that's what I'm going to do.  I started with the forward rivets.  Most of them went in fairly easily, but there are a couple where the rivets butt up against the hinge brackets.  I'm not sure I'll be able to get a bucking bar on those, so I may have to go with a few blind rivets there.  I didn't finish the outer edges of the front.  I have to think about what I might have for a bucking bar that will let me get into some of the tight spaces around the flanges of the side pieces.  I was a little worried about how the counter sunk pop rivets would work on the aft portion where the skin goes over the small tube, but it ended up working out fine.  You can see where instead of continuing the pop rivets to the outside, I just filled the holes in the skin.  These are the holes were the space in between the skin and the tube means there's nothing for the rivets to grab onto anyway.

I think I'm going to fight with the fit of the front skin gap for a while.  It still needs to be opened up a bit in the center - it catches the top fuselage skin and keeps the canopy from being able to open.  The skin doesn't lie even with the fuselage skin in all areas either.  This is a huge complaint of nearly every builder I've ever talked to.  It's mostly a problem on the curved portions, and really just on the left side.  I think with some gentle bending of the edge of the skin and maybe some scarfing of the edge I can get it close enough to be mostly  unnoticeable. I'm not going to mess with the final gap fit until the canopy is finished though.  Things just move around too much still.

Yesterday when I primed, I went ahead and shot some primer over the general area where the glare shield will be painted black.  I may have to redo it, but I had the primer in the gun, so why not.

Here's a shot of underneath.  You can see the filler I put on top of the outer portion of the tube to take up the space between it and the skin (it goes all of the way to the outside, but you can't see that).  You can also see the filler that I used to smooth out the long strip of aluminum epoxy I had done earlier.  After being primed and painted, I think it all ended up pretty decent. You can't see it in normal light, but with the camera flash you can see the small strip of cardboard that stuck to the top of the tube in the center after I had painted it and laid it out to dry.  I thought it was drier than it was.  I could have tried to sand it off (the carboard was stiff, not something I could soak in water and rub off) but I didn't want to destroy paint.