Foreward Fuselage Reinforcement Stuff

I peeled back the forward side skins a few inches on both sides so I could get the right angle drill in place to match drill the F-684 gusset to the existing holes in the auxiliary longeron (the angled one).  Then I match drilled the firewall angle to the pre-drilled holes in the gusset.  

The 902 bulkheads went in next (the vertical piece in the pic below).  Well, they went in and out and back in about 10 times.  I had to flute the flanges that go against the skin, which was easy.  What took a lot of back and forth was getting the web of each bulkhead parallel with the web on the other side.  I think there is some sort of a bracket that attaches the subpanel parts to the bulkheads, so it needs to be in the same plane from side to side.  Out of the box, the webs were pointed about 3 inches behind the other side.

Once I had the bulkheads done, I moved on to the 9101 gear attach webs.  It's hard to see in the picture below, but it's the shiny piece of sheet (thick sheet - maybe a little over 1/16" or so).  These webs sit on the gold 904 bulkhead and nest in the angle of the auxiliary longeron.  They also have a flange at the fore end that gets drilled to the bulkheads I just put in.  I had to sand a bit of material off of the bottom (top really, bottom in the picture) of both left and right webs so they would fit into the longerons, then I drilled all of the holes based on the existing holes in the skin and longerons.  The holes in the middle of the sheet will get enlarged once I pull it back out.  They are for fuel and vent line passthroughs/attachments.

I clamped the forward flange of the web to the 902 bulkhead and drilled them together.  There is also a tab on the 902 bulkhead (both on the top and bottom) that sits on the longeron and has to be drilled.  That was awkward to say the least.  The tabs are oddball shapes and only sit partially onto the longeron, so it took a number of marking attempts before I had a drill location that I thought would be okay for both the tab and longeron.  As I was drilling the tabs I realized I had never match drilled the big lower longerons to the side skins, so I did that next.

Now on to some random parts that will be used to stiffen up a few locations around the side skins and bulkheads.  I made two 996B spacers out of very thick stock.

I cut the angle for the left and right 996C reinforcement angles and got the layout figured out.  From what I've read online, the locations of the holes shown in the plans are very wrong for this part, so most people suggest making the parts as blanks and match drilling using the skin vs drilling holes where the plans say to.  That'll be where I start tomorrow.

F-684 (2)

Springtime chores took precedence over the plane since the weather was so nice.  I did sneak into the garage and did a little more work on the gussets for the firewall brackets though.  These ended up being pretty fiddly.  The top and front side have to be bent a little to nest on top of the steel bracket and behind the firewall angle (bent two different directions).  That took a lot of running back and forth between the vice and the plane.  The real issue is that Van's cuts the gusset too short in my opinion, making it tough to get good edge distance on the holes on the top as well as the top hole that will be drilled in the firewall bracket.  I'm not alone in that opinion apparently.  I did some research online, and pretty much everyone gripes about it.  If they would just make the gusset 1/16" taller, it would be fine.  I did a lot of measuring and sliding things this way and that, and finally ended up with a compromise I'm happy with.  I clamped the gusset in place and it's ready to drill the next time I can run out to the shop.

F-684 Gusset

The mini-task for today was making the F-684 gusset that connects a few of the longerons and lower engine mount bracket all together.

Forward Lower Longerons

I finished up the left lower longeron tonight by drilling the bolt holes into the engine mount bracket.  If the holes don't look evenly spaced, it's because they aren't.  For whatever reason, the plans call out oddball spacings (1", 3/4",7/8", 7/8").

The right side lower longeron was next and went relatively quickly.  The only issue I found was that on this side, the longeron butted up against the angled longeron and wouldn't seat down against the bracket completely.  I just sanded down the corner of the lower longeron about 1/16" to get rid of the interference.  I usually try to keep everything pretty tidy while I'm building, but with all of the steel parts I've been drilling lately I've had to use a ton of lubricant on drill bits.  That stuff gets everywhere and makes a mess!  I'll have to really wipe things down well when I'm ready to prime.

The lesson for tonight: when you're sanding parts and the belt sander starts to shimmy away, don't absent mindedly grab it and pull it back over.  You may just be grabbing the disc sander side of the machine.  Needless to say, finger printing won't be an issue for a while.

Forward Lower Longeron (Left)

Now that I'm starting to get into the groove of my new job, I'm going to try to get back into the garage at least a few times during the week vs just on the weekends.  Even if it's just for a few minutes, the baby steps will add up.  Tonight I worked on making the F-917 lower longerons.  It's pretty simple, but of course that never equals quick.  The longeron is made up of a 1x1 1/4" angle with one leg chopped off at the aft end.

The longeron lays on the lower engine mount bracket, which has a twist that the longeron has to match.  It took quite a bit of back and forth between the vice and test fitting it, but I'm happy with the end result.

The bottom edge of the longeron sits proud of the skin edge by about 1/8", which threw me for a bit until I realized that the bottom skin that wraps around and slides in between the side skin and the longeron doesn't actually get riveted to the bottom side of the longeron.  The longeron has a gap underneath to make room for the bolts that will attach it to the engine mount bracket.

Forward Skin Stiffeners

The forward skin stiffener (F-719) is a piece of angle that has a jog on one end that fits over the 904 bulkhead flange, and the front end sits close to a piece of firewall angle.  It needs a piece of angle fabricated and riveted to the fore end to attach it to the firewall angle.  I made the 719B angle clips for this.

Getting the skin stiffeners in place was a little awkward since they are in the middle of the skin and there is no way to clamp them in place.  I drew a line down the middle of the angle, lined it up with the holes in the skin, and used some tape to keep everything in place - at least enough to get the first hole drilled so I could start clecoing it together.  You can see below how the angle clip connects the stiffener to the firewall angle.  This would have been nearly impossible to do without my new right angle drill!

I repeated the process on the left side.

Gear Towers & Forward Fuselage Longerons

 A few odds and ends were on the menu for today.  While I'd match drilled almost everything to the center section side skins, I still needed to drill the baggage corner ribs to the side skin. These are the ribs that essentially connect the bottom skin to the side skin in the baggage area (not even sure if they're considered ribs since they lay flat on the bottom skin).  The ribs are already match drilled to the bottom skin, but the outside flanges of the ribs need to be drilled to the side skins.

I crawled under the fuselage and clecoed the pieces in place.  It was then I realized that I still needed to dimple the ribs.  Since the bottom skin was already dimpled, without the ribs dimpled they wouldn't set flat to the skin, meaning the drilling to the side skin would be slightly off.  I pulled the ribs out, dimpled them, and put them back in place.  Duh moment number two - everything is dimpled now except the curved portion of the side skin!  That means there is a flat piece of sheet in between the bottom skin dimples and the rib dimples.  Again, that means the vertical alignment to match drill the flange to the side skin would be slightly off.  I didn't want to pull the side skin off yet to deburr and dimple the curved portion, so I'm just going to wait until later to finish up this match drilled portion.  This picture is a little hard to orient to - it's looking up at the rib from underneath the fuselage (the side skin is the light grey portion with the big step hole in it).

I moved on to the next single line of instructions that took 2 hours (this is the rule now - no more hand holding).  The front fuselage bottom skin gets holes cut into the outside portions to accommodate the gear leg towers.  I made a copy of the full size template and aligned it with the skin edge and rivet holes and marked where the cutout needed to be made.  Now for the time consuming part - trying to figure out how to make an oval cut in thick aluminum sheet. I tried a number of different methods, but in the end my right angle cutoff wheel worked the best.  I slowly nibbled away at the hole with the cutoff wheel then used a file to finish it up.

I test fit the gear towers, and the fits are close, but the holes are going to need some tweaking when it comes time to mount things for good.  The main tubes of the gear towers fit well, but the welds on the tubes hit the edges of the holes.  By design the large hole is super close to one of the rivet holes, which I don't love.  I'll have to do some research to see what people tend to do there.  I also drilled the brake line hole.

This is how the gear tower fits up against the 904 bulkhead and exits out the bottom skin:

Now for the horrifying part - the tube hits the flange of the 904 bulkhead, meaning the bulkhead flange has to be carved out to fit the gear tower.  This is one of those tasks where screwing up is not an option given that this bulkhead is pretty well baked into everything built so far!

Now back to the forward fuselage.  The 713 auxiliary longerons attach on an angle as one of the side skin stiffeners.  Because the skin transitions from flat at the center fuselage to slightly curved at the firewall, these longerons have to be twisted slightly to fit.  I started with the left side and put it in the vice and twisted it just a few degrees.

I clamped the longeron in place, trimmed the aft end so the angle matched the bulkhead angle and match drilled it to the skin and the firewall bracket.  Unlike most skin rivets which are 3's, this longeron gets bigger rivets (4's).  

Firewall & Side Skins

The first thing I needed to do today was get the firewall clamped to the side skins.  That seems like an easy task on the surface, but it ended up taking me a couple of hours.  The plans say that the face of the firewall should be 5/8" from the edge of the side skin.  That's pretty straight forward, right?  The issue I ran into was the fact that the firewall is anything but flat, and the flanges have the typical warp to them that most parts that get a curved bend have.  The problem is that the flanges on the firewall can't be fluted to straighten everything out.  The surface has to stay flat so you can install the cowl attachment hardware (whether I'll do hinges or camlocks is still up for debate), meaning fluting isn't possible.  I cheated this way, that way, a little back over here, a little forward over there...In the end I got pretty close to the 5/8" mark on both sides, but it was a struggle to get there!

Once the firewall was clamped, I also clamped the steel brackets to the longerons.  The rivets were just temporary to keep the skin and longeron holes lined up while I worked.  I ended up grinding down the sides of my clamps so they could fit in between the rivets.

Next up was drilling the side skins to the firewall flange.  The stainless steel didn't give me too much trouble, although I'll have to do a lot of cleanup of the holes after everything is taken apart.  The exit side of the hole always has a nasty, sharp spur when drilling stainless.

After both sides of the firewall were drilled and clecoed, I moved on to match drilling the steel brackets to the existing longeron/skin holes.

Then on to the bottom (top in the picture) skin to firewall section - one row of holes drilled into the aluminum angle on the aft face of the firewall and one row of holes into the firewall flange itself.

Once the bottom skin was drilled a thin spacer and a thick aluminum sheet get added to the outside portions of the firewall.  This is to aid in supporting the cowling (although I'm not quite sure how yet).

Instead of diving into putting more of the side skin stiffeners in place, I decided to spend some time on one of those tasks that has very little motivational value because you see no progress - match drilling and final size drilling the side skins to the center section and tailcone.  I finished up both sides.  There is a lot that has to be pre-assembled all at once before it can all be taken back apart and prepared for riveting!  That's going to make riveting prep interesting, especially given that it seems like every part has very specific callouts for holes - countersink these 2 holes, dimple those 4, but put a flat shim in between....it's going to take a while to figure out the correct prep for each part.

 

Left Longeron & Forward Fuselage

The left side longeron still needed to be drilled to the skins, so that was step one today.  I started at the tail and worked my way forward until I got to the downward bend of the longeron (well, upward with the fuselage upside down).

Forward of the bend in the longeron, it also twists so that the skin starts to curve near the top of the fuselage and will create a nice transition to the top skins.  It's a pretty significant twist, so I clamped the skin to the longeron, also making sure that the edges lined up.  Then it was the same story with drilling and clecoing.  I did this to both sides.

The instructions mention that the longerons need to have 3/4" clearance to the front of the skins so that the firewall will be able to nest there.  I trimmed them to a little beyond 3/4" (the instructions say going short is fine - I've read about too many builders having to take everything apart to re-trim them, so figured I'd give myself some wiggle room).  I wasn't sure if I should square off the longeron or trim it to match the angle of the skin.  I matched the angle of the skin - I'll find out if that was a good or bad idea at some point I'm sure.  I clamped a thick plate of metal behind the longeron to protect the skin and used my cutoff wheel.

Now things are getting serious!  The firewall is ready to go on.  The instructions are pretty weak on this topic, so I spent quite a bit of time looking over the plans and digging up information I could find online.  The firewall has steel brackets at all corners - I nested the upper brackets (bottom side right now) in the longerons and temporarily clamped the fuselage in place while I started to work through measurements and alignment.

The bottom skin has to go on to lock the fuselage distance from the 904 bulkhead into place.  I drew a line down the center of the firewall aluminum angle.  I'll line the holes of the bottom skin up with this.

The bottom skin is thick!  I suppose that's comforting since I'll be stepping on it.  I lined up the aft end and clecoed the two rows of holes through to the 904 bulkhead (that's the big gold bulkhead that the wing spars mate with).  After I took the picture I actually went ahead and put clecoes along the sides as well to do my best to keep it all fairly square.  The front edge has two rows of holes - one for the aluminum angle on the firewall and one for the stainless flange itself.

I lined the holes up with the center line of the aluminum angle and drilled one hole on each side.  For now that's all I need to keep the firewall in place.  The nerve wracking step of drilling the longerons to the steel brackets is next.  No screwing up there!  The weight of the firewall makes the longerons sag a bit, so in order to keep it all aligned I put rivets into the skin/longeron holes (bottom of the picture below).  You can't use clecos at this stage because the steel firewall bracket is pressed up against the inside of the longeron.  The rivets can at least keep the skin and longeron in place while I drill the bracket.

Drilling Fuselage Longeron - Right (2)

The last of my backordered items finally arrived!  These are the parts for the electric flaps. 

I just had a few minutes to work tonight, so I finished drilling the right side longeron up to the 904 bulkhead.  I stopped at the point where the longer bends to match the skin angle.  This is also where the twist begins.  I will switch over to the left side next and get it to the same point so everything is held solid before I move forward and clamp the skin to the bent and twisted portion of the longerons.