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RV-3B Dave's in Colorado

Lately all I've been doing was deburring and dimpling. Nothing much changes appearance and so I haven't bothered with photos. These include the flaps and the flap and aileron rear spar to skin braces or fairings.

I'm not including the bottom skins yet because they'll need to be stored for a while longer and it's easier to store them undimpled.

One thing worth mentioning on the W-724 aileron braces (see post 199) is that the prepunched holes (how nice that is!) are a bit larger than #40, so I had to drill them to #30 for -4 rivets. No problem but slightly disconcerting. Edit - they measure .125.

Dave
 
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The RV-3B flap inboard rib is considerably different from many of the other RVs. Here's the RV-7 inboard rib assembly, for example, using aluminum parts:

11bojg3.jpg


Here's a photo of the RV-3B version. It's a formed welded part that Van's supplies. I needed to tweak it a bit to make it fit and this is the way it'll fit into the inboard rib:

2earlsl.jpg


The angle shown in the next couple of photos was used to hold the aft edge of the top skin flat while I riveted the aileron fairing to it. I placed the rivets in, taped them in place, and then clamped the angle on. The angle itself was against the factory heads of the rivets and when I squeezed them, I squeezed right through the angle.

This worked quite well. Thanks to David Howe for the idea.

nosorm.jpg


2d0npt5.jpg


Dave
 
Peter, that rib includes the nose rib and since it's the center rib of the five outboard leading edge ribs, it's a bit difficult to get to. I asked Sterling about that at Van's and he suggested LP4s for these and that's what I wound up using on the web to rib flange joints.

For me, it was simply a question of convenience and a certainty of getting a good set on them. Building this airplane has been an exercise in production risk reduction, not that I'm very good at it yet.

Dave
 
No new photos, sorry, I've been doing small things -


  • Riveted the flap brace to the rear spar, both wings.

  • Inserted the plastic bushings to the ribs for wires and stuff. I'm not planning on using conduit to same some weight.

  • Deburred and dimpled the flap skins and related parts (still need to countersink some parts).

  • Made some labels for the bins for some hardware that just came in,

  • Measured the aileron pushrod length for the right wing,

  • Added the bolts between the spar web and the Z-brackets.
All necessary stuff and none of it particular photogenic.

I glanced through my cost spreadsheet and thought that you might be interested in the categories that I use to track my costs.

My major categories are:

  • Airframe,
  • Firewall forward,
  • Systems,
  • Hardware (I seem to use some after-market hardware from time to time like the light-weight MS21042 nuts),
  • Jigs and tooling (but not tools, that is, not things like drills - just specialized RV-3B stuff like the blue frame that holds the wings),
  • Tools (here's where the extra drills go),
  • Infrastructure, things like tape or lights,
  • Replacement parts, which is pretty embarrassing that I have to have a category just for that.
This is cool - I've learned how to use lists.

Dave
 
Countersinking Flap Spars and Flap Braces

Both the flap spars and the flap braces are countersunk for the skin's dimples where the piano hinges go. Since the single-flute countersinks aren't currently available, I needed to learn how to use the standard three-flute type. First I determined that no combination of speed or pressure would reliably provide smooth countersinks using this piece of scrap.

x3989z.jpg


Since the holes all appeared slightly larger than I'd drilled, I made a back-up piece. I used a length of scrap 3/16" aluminum, probably from the stabilizer's spar cut-off.

23lmuzq.jpg


That worked. I made several successful countersinks in another bit of scrap. Once I was satisfied, I went to the airplane. This shows the back-up bar in place.

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I used my slow-turning cordless drill for this.

dxk0oz.jpg


Finally, I sprayed s dash of zinc chromate primer into the cap of the rattle can and used a Q-tip to apply it.

1xz81x.jpg


Wasn't hard at all once I knew how.

Dave
 
Milestone - Control Surfaces Done

Finished riveting the flaps today. This marks the completion of the control surfaces. Like most of the RVs, there's eight of them, counting the trim tab. The shop attic will contain another five, more or less.

Here are the flaps, all riveted up.

2zxxahl.jpg


When I said that the control surfaces were done, I meant that somewhat loosely. It's a homebuilt airplane, after all, and you know what that means. I'll probably tweak the trailing edges a bit, trim the inboard ends of the flaps (after I have a fuselage) and do a few similar things like fiberglassing the tips on the tail surfaces.

In the picture, you can see that one flap is held in the vee-jig. That jig has proved enormously useful and I believe I'm done with it, at least for now. At last I can have my work bench back.

Dave
 
With the flaps and ailerons done, I wrapped them in bubblepack and put them in the shop rafters. I think I should have adjusted the aileron pushrods before I did that, and I might pull the ailerons down and do just that. In the photo, we're looking almost straight up. The tan stuff is the sprayed-in foam and you can see one of the four electric radiant heaters, too.

1zy7hk.jpg


You can see the tip of a scrap horizontal stabilizer and a few other scrap parts poking out from the Shelf of Shame in the rafters.

I'm still taking care of a bunch of small things before closing the wings. Here I'm measuring out some wire for the nav/strobe lights. This is for one wing.

qrdzjp.jpg


I'm using plastic bushings in the ribs rather than conduit. I've learned that it's not a bad idea to be generous with the size of the bushings. With cable lacing (and probably with tie wrap too) it gets difficult to move a bundle past bushings if they aren't reasonably large. Guess how I learned that.

Dave
 
Tooling and Wires

After stringing wires through the wing, with the roll autopilot servo and the nav/strobe wires shown below,

30molk1.jpg


it seemed like a good time to make a fixture to locate the rear spar carrythrough in the fuselage. But before that, see those nut plates on the ribs on either side of the servo? They were for Adel clamps for the servo wires. The way I finally located them are simpler. Also, I'm not using the strobe sync wire. While that gives a prettier flash, I'm unconvinced that it materially aids in visibility, and omitting it means that I don't have to run it across the fuselage. This is simpler. As you know, simpler is gooder.

Back to the rear spar carrythrough fixture, if course, I had to figure out where the fuselage carrythrough fit inside the spar fitting. The carrythrough is 3/16 thick. The fork for the RV-3B is in the wing root, and the assembly includes a 3/16 spacer and the .040 rear spar. This means that there's .040 clearance when the carrythrough fits. I built this shim assembly out of some .063, some .125 and some .020, giving me about .020 clearance or a little less. I double-flush riveted the pieces together and clamped them in the rear spar so that it was clamped to the aft face of the spar fork.

Here's the shim in the fork and the fixture in place. The top piece of the shim is just there to match the fork's thickness; I clamped an angle to the fork and the shim to the angle. The angle was removed for the photo.

29c2nwh.jpg


Then when I located the aft angle on the fixture, it was a simple thing to clamp it to the shim and drill and cleco it to the fixture.

When I'm building the fuselage and I need to mount the carrythrough, I'll clamp its forward face to the fixture and it'll be pretty much centered in where the spar fork will be when I hang the wings.

6tp9qg.jpg


Still have to make the one for the other side.

Thanks to David Howe, who sent me a couple photos of his similar fixture.

Dave
 
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Should have mentioned in the last post that I'm using hardware store aluminum angle for these fixtures. The main reason, besides availability, is that I've found that aircraft angles are sometimes not 90 degrees. The ones I have around the shop seem to be slightly more acute than that. It's pretty annoying.

The hardware store stuff is 90 degrees.

For these fixtures, strength and weight are not issues.

Dave
 
Nice work Dave
I'm curious why you wrap parts in bubblepack before putting them up for storage. Are you not concerned about trapped moisture?
 
No, this part of Colorado is relatively dry. I've got untreated steel parts (not aircraft parts) that must be 40 years old in my basement that haven't rusted.

The wrapping isn't entirely sealed - there's lots of gaps in it. It's mostly for protection from me being clumsy. I left the blue plastic on for the same reason.

I learned to fly as a teenager in Santa Monica, CA, and the aircraft there were definitely subject to corrosion. I'm well aware of that since I paid for my lessons by washing and polishing airplanes and saw them every day. But in this part of the country that's not really a factor. My 1955 Cessna 180 is nearly corrosion-free, in spite of not being primed, because it spent all but about six months in the dry middle of the United States. It's only corrosion came from that six months near the Delaware River, where it was tied down outside.

Dave
 
One of the jobs before riveting the bottom skins on the wing is cutting out the hole for the pitot tube. My pitot tube is non-standard. You can see it here.

And since the RV-3B is not prepunched, there wasn't any sort of hole in which to install it. Fortunately, I'd previously marked the correct location using a short section of the plain strut and the mounting.

w7h15l.jpg


All I had to do was cut it out.

A couple of starter holes and an 1/8" bit in a Dremel (try it - it works, not perfectly but it works) gave me this.

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A little more and then it was entirely up to hand tools. Here's the hole and the tools. The short section of plain strut was handy, of course, as a gauge.

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And with the inspection hole cut-out ring in place,

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Another of the jobs is to taper the corners where they overlap. The RV-3B kit comes with full-length top skins so I didn't need to do it there. Wirejock suggested taping off a 3" triangle and that worked okay. I used both a Vixen file and a belt sander. Got to say the Vixen file was gentler. Slower, too. One thing that was hard was getting the corner to taper evenly, and I'm not entirely sure that I really did. Here's my first corner.

bfritj.jpg


Dave
 
Back when I was laying out the bottom skins, I'd forgotten that Van's had included pre-punched inspection hatches for the bottom of the wing. Oops.

I went ahead and made my own, and of course the holes in the backing ring were incompatible with the pre-punched ones. Mine were slightly different sizes, too. Imagine that - Maybe 20 pre-punched parts in the entire airframe and I didn't use four of them.....

I left the cut-outs in the bottom skins until the deburring/dimpling stage. The cut-outs are now complete and I had to match the holes in the hatches to the holes in the spar. Yeah, I'd gone ahead and made holes in the spar for the hatch without including the hatches, another sequence error.

This next part I figured out before riveting the skins on. What I did was cleco the skins on the wing, cleco the hatch back-up rings in place, and screw the hatches on. Of course then the wing was covered up and I couldn't back-drill through the spar. A bit of tape held the hatches in place and the leading edge, attached, gave me a solid fore-aft reference, and with the skins removed, I could easily back-drill through the spar to the hatches.

Here they are drilled and clecoed.

10zofv5.jpg


After this photo, I hung the skins back on and double-checked everything. Yep, it all works, at least for the left wing.

I'd joined the VAF group purchase of the PCU5000 prop governor, which arrived today. It weighs 2.1 pounds with the shaft cap still on.

261jm8y.jpg


Dave
 
Set the Hamburger for 15 Minutes.....

One of the shop tools I use is a timer. Now I know that we all have our own kinds of timers. This one's mine, a gift from a friend.

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Here're the bottom skins clecoed in place. I've trimmed the holes for the inspection plates. The skins are in place so that I can locate the holes in the plates at the spar flange, which I somehow didn't do earlier. Now it's the left wing's turn.

34eervb.jpg


Dave
 
I'd joined the VAF group purchase of the PCU5000 prop governor, which arrived today. It weighs 2.1 pounds with the shaft cap still on.

261jm8y.jpg


Dave

Hey David.....thanks for joining in.....got my PCU 5000 in this week also!
(No pic posted bcuz it looks just like yours):)
 
Dsub Connectors

You might remember that I'd installed a pretty red and black GRT roll servo for the autopilot in the right wing. Although I definitely like the GRT system, I switched to my second choice, the Dynon Skyview and am installing their servo instead. The Dynon roll servo came with bare wires and no connector, unlike the GRT servo which had a connector right on the servo. I ordered the Dynon Skyview servo harness and it came with three connectors, pins and a bundle of wire.

Since I'd never used Dsub connectors before, I had to buy the crimping tool and the installation/removal tool. I'd like to thank Steinair.com for providing some excellent videos showing me how to use these. There was only one bit of information lacking: how far to strip the insulation for the pins. Turns out that 3/16 inch is the magic distance. I found that by using a bit of paperclip and measuring the depth of the wire sockets.

Since I didn't want to risk screwing up any of the actual harness hardware, I ordered a bit of wire and some pins and sockets and a pair of Dsub connectors. I got some 20 gauge and 22 gauge wire. After cutting a bit of wire from each, I made this short practice harness.

2dtajjk.jpg


Once this was done I found that the wire with the pins or sockets on it seems to go into the connector 1/4 inch. The completed cable, from the cable end of one connector to the end of the other connector, was 1/2 inch shorter than the wire I'd started with. Good to know for when I do the panel later on.

The Dynon connector shells are interesting. Remember that this is all new to me and these parts don't come with assembly instructions. But I played with the pieces and it looks as if they go together like this.

nwbnv5.jpg


Finally there was nothing else to do except wire up the servo's connector. I haven't checked it for the correct wire to connector location yet, figuring that I'll do that tomorrow.

2py5j55.jpg


I also tapered the overlapping corners and dimpled the bottom skins for the right wing today, so I did get to do actual airframe work too. And drilled out the inspection plate to spar holes for those inspection plates (which still need dimpling at the spar holes). Busy day.

Dave
 
I also have enjoyed the D-Sub connections. I have a good stripper, but it nicks the wire a bit more than I like where it grabs it to pull off the insulation. Have fun Dave!
 
The Dynon SV32 autopilot servo has an awkward electrical termination. The servo is supplied with a stub cable, mine was 10" long, to which the connector comes when you buy the servo harness, rather the servo itself. That's mystifying but largely irrelevant. I decided not to shorten the wires from the servo, which left the connectors hanging out in free space.

I made this support from a scrap piece of flap stiffener and added some lightness to it. It's simple enough, only weighs about 10 grams, and is attached with a pair of LP-4-3 rivets. Those holes all in a row along the bottom of the support? They saved one entire gram, yes, the whole gram. Maybe a little over.

I made them by punching out a row of pilot holes with my Whitney punch, a handy but awkward tool.

2ish6qo.jpg


The bottom skins of the wings need to be primed. Here's my paint bench, or rather here's the snow atop the paint bench. This is Colorado and it's winter here.

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There's a crude work-around that I'll have to use.

In other exciting news, I've drilled and countersunk the holes for the inspection plates in the spar flange, including the nutplates.

Dave
 
Engine to the Shop

I took the engine, a Lycoming O-320-D2A, to a local engine shop to have the oil filter adapter and governor adapter added and the engine changed from fixed-pitch to constant speed, and a few other things. The engine hasn't been run since Lycoming pickled it on 2002. That's Joe Folchert of Aircraft Engines & Cylinders in Greeley, CO. (If the Tinypic.com image doesn't show up, please click here.)

24fmm0w.jpg


The RV-3B plans don't show a firewall recess and I know one will be needed, but until I have the built-up engine, I don't know where to locate it.

You might be asking, hey, what happened to the wings? Are they done? Well, no. But the bottom skins should get riveted on soon and I've been working on other things, waiting for that.

One of them is that to locate that firewall recess, the engine mount needs to be on the engine. The engine mount came unpainted. I cleaned the gray off it and was getting ready to shoot the rattle-can high-temp paint (the snow on the paint bench melted and it's operable again - in fact, I used it today) when I realized that the paint needs a three-step cure up to 600 degrees. I didn't have an oven big enough and was reluctant to take it that high anyway since I'm not a metallurgist. I did spray a couple of samples and cure them to 400 F, to see how that affected the paint and found that this cure slightly increased the susceptibility to abrasion and greatly increased its resistance to chipping. The abrasion test was to drag a 100 grit piece of sandpaper over the paint, weighted down with a bucking bar, one pass each sample (also here):

2lxyy47.jpg


The cured sample is on the right in one photo above and on the bottom in the lower photo.

The chip test was to drop a metal chisel on it from 12.0" above, 3 drops per sample. (also here):

24lijjn.jpg


The paint was Rustoleum's 2000 degree spray paint. I sprayed a primer coat, a white coat and a clear coat and waited a few days before curing and again before testing.

I went out and bought a paint that doesn't have the high temperature resistance of Rustoleum's but doesn't need a baking cure, either. Haven't painted it yet.

Dave
 
The bottom wing skins have all the solid rivets installed that they'll be getting. David Dalton, a local RV-7A builder, came over and helped on the right inboard skin. Then I did the other three skins myself.

The procedure that worked best, working by myself, was to go from inboard to outboard, one rib bay at a time. I riveted the main spar holes to the next unriveted rib and then worked from the main spar towards the rear spar. Since the leading edge was up in the jig, that meant that I was standing, working downward. I couldn't do the final five rivets close to the aft spar because my arms weren't long enough and although I could reach them, they were too awkward to do reliably. So I left the rear spar rivets and the aft-most five rib holes to be filled with blind rivets.

befrqe.jpg


After I'd completed these, I realized that I could have riveted the rear spar as I did the main spar, doing a couple rivets in each spar and then moving back to the other spar. And I probably could have gotten those five rivets the same way, by sitting on the floor and reaching into the wing. But I didn't think that through until the skins were riveted. Now there's not enough access for that.

Blind rivets it'll be.

While waiting for the blind rivets to arrive, I riveted the -4 rivets that go into the main spar web at the inboard stub end. These five rivets and the adjacent F-303H block are left to the builder. Big hint: do these BEFORE you assemble the spar to the wing frame and it'll be a bit easier. And it won't affect a thing. It'll just be easier.

35jdyd5.jpg


(If the two photos are gone, try here and here.)

Dave
 
Two Rules

1. Don't cut or rivet or drill anything until you absolutely have to, because you never know what else might need to be part of that assembly or go there.

2. Cut, drill and rivet the small things early on, because it might be impossible to do them later.

Yeah, these sort of conflict with each other. In fact they make a classic Catch 22. That's the charm of building an RV-3B kit.

Can you spot what's missing in the top photo of the previous post that led me to post this? Hint, it's an RV-3-specific part, the pre-punched kits don't need it.

Dave
 
The answer to the question I posed above is that I'm keeping out the doublers for the inspection plates for just a little more access until later.

I finally got to see and sit in a flying RV-3. I hadn't seen one since I got interested in them a few years ago. Scott Taylor let me sit in his. He's a lot bigger than I am so I'm deep into the seat. In mine, I'll be higher.

a149ao.jpg


Or if that photo is unavailable try here.

I made a wood tool to go between the F-303 front and back bulkheads. Unfortunately I picked a windy day and more unfortunately, left the garage door open. I ran the table saw and planer in the driveway and a lot of wood shavings went into the shop. I spent the rest of the afternoon vacuuming the shop.

The F-303H shear blocks get bolted and riveted to the spar web. The bolts go in after the wings are on the fuselage but are needed to locate the rivet holes, which for some reason aren't pre-drilled at the factory. These bolts go through the F-303 bulkhead, the spar web and the F-303H blocks. They fit nicely in the blocks but not at all in the spar web. The holes are slightly too small.

I checked the same holes in the F-303 side pieces and some of the holes let the bolts in but most of them didn't. The manual emphasizes that we shouldn't drill out any of the spar mounting bolts and these clearly don't fit. I looked at them with a 10 power glass and these holes, in the side pieces, are punched, not drilled like the main spar bolt holes - and yet these too need good alignment.

Back to the plans. On drawing 6, the plans just describe the hardware. But on page 11, there's a note to match drill the side pieces to the spar. Imagine that.

Our local hardware store is a good one. They had 1/4" reamers.

I used AN-6 and AN-4 bolts to locate the aft F-303 bulkhead on the left spar, and match-drilled the shear block's holes. The shear block, incidentally, is that cross-wise block of aluminum near the right side of the photo that says "LH" on it. The holes are the two 1/4" holes in it.

2mxiujr.jpg


And then did the same for the right spar.

nvr5uo.jpg


Then I clecoed and used some AN-6 bolts for location and match-drilled the front bulkhead to the rear one.

xb07ia.jpg


Alternate links to these last three photos are here, here and here.

Dave
 
No Clecos!

A milestone of sorts, wings with no clecos visible. I've still got to rivet the flap hinge on but that gets done when the wing's in its cradle, which is already out at the hangar. The hangar, you may remember, is where I've been storing all the kit parts and Van's boxes.

2yney45.jpg


Next job was to wrap one wing in moving blankets. Well, moving blankets aren't what they used to be. Here's the left wing with two blankets on, overlapping.

2ibnjbm.jpg


An alternate place to find the photos, if they disappear, is here and here.

There are a number of places in the plans where Van's specifies certain brass bushings. A friend's homebuilt has these and they work reasonably well. Unfortunately Van's didn't bother to include them in the kit. Some time ago, I had a composite trimaran sailboat and I used plastic bushings from IGUS.com on some of the moving parts, and was pleased with both the smooth operation of them and the minimal wear. So I ordered a set of appropriate plastic bushings for my RV-3B from them.

I'll try them out and see how it goes.

Dave
 
Wings Away!

Wirejock came down from his mountain to help me more the wings to the hangar. It went smoothly enough. After taping moving blankets to the wings beforehand, I put one thin piece of plywood in the pickup truck, then the right wing, blanket side down, then another thin (and therefore light) piece of plywood, and and finally the left wing. Tied them down and off we went, driving carefully.

Of course something had to cause some concern. In this case it was a pine tree in the backyard that had grown up into some power lines. While we were tying the wings in, a neighbor dropped by to tell us that the tree was sparking with the wire. After a brief visit from a fire truck and a call to the power company, we were on the road.

Unloading went smoothly enough. Larry took a photo of me holding a wing in the hangar.

2hzk74y.jpg


or here.

After we got that done, we went for a flight in my Cessna 180. Very pretty day and he had the controls for most of the flight, mentioning that he hadn't flown locally before and hadn't flown in a couple years. I did my usual bouncy landing and we put the plane away.

Later, I took down the wing jig and put it in the truck for its trip to the airport. I will need it at least once more.

Dave

P.S. I checked and the wings took three years to the week. Yikes.
 
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Thank you

Thaks so much for the treat. It was fun moving the wings but the real treat was flying Big Hammer!
 
Engine Mount Beef-Up

KatieB sent me a photo of a cracked weld in an RV-3B engine mount at a lower corner where the landing gear socket is welded adjacent to a mount bolt. The crack was visible with dye penetrant. Yes, this was a six-bolt mount.

10cq1e1.jpg


I thought about what was going on and why that crack should exist, and then added this gusset, the one the arrow points to. It's .090 4130.

sfdtp3.jpg


I haven't done any stress analysis on it. The gusset is simply a WAG. The welded length of the inboard end of the gusset is about as long as the welded side of one of the adjacent factory gussets.

What I think's happening is that the drag load on the wheel is causing this. It doesn't appear as if there's a great deal of stiffness to the engine mount in a direction that would resist twisting of the socket, and that's one of the load components that a drag load at the wheel would produce. This gusset adds a minor amount of stiffness and some additional strength, particularly across that cracked weld.

Now don't misunderstand me here - I'm not trying to imply that the engine mount is not strong enough as it comes from the box from Van's. All I wanted to do was add some strength in a certain area (yes, I did it on both sides of the plane). So this is what I did for my plane. I'm not making any recommendations.

Future inspections will need to check all the welds in the mount.

Note that the welds are on the top of the gusset, so that any oil in service won't fall into the edge of the gusset that's unwelded (all the gussets are welded only on one side).

If there aren't any photos visible, try here and here.

Dave
 
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Gusset

Dave,
I had the same cracks in my RV 3 when I brought it. Noticed this on the pre buy inspection.
Locally I have been involved in 3 RV's a 6 a 4 and my 3 with engine mount cracks.
I know common denominator is my flying. Had to get that one in before someone else did.
We have came to the same conclusion that it is the torsional load, and have strengthened the mount accordingly.

You will enjoy the 3.

Rob
G-BVDC
RV 8 extremely slow build.
 
This is a busy time of year for me so I haven't gotten much done lately.

The engine mount got painted. Here it is in the primer. You can see my added gussets near the top of the photo, welded across the landing gear socket.

xbmkwj.jpg


Or if that doesn't show up, try here.

Since then it's been painted white. I used Dupli-Color Engine Enamel rattle-can. It seems to be a decent paint but I've already scraped it in a couple places so we'll see.

I reamed the mounting holes to 3/8".

I had a bad F-303A part, one of the four upright side pieces that go into the assembly of the spar bulkhead. I called Van's on that, sent them a photo and offered to buy a good one from them since it's been four years since I ordered the kit. Van's graciously sent me a replacement part for free.

Darn good service - thanks, Van's!

While I was placing the order, I ordered a firewall recess kit. I figured I'd get a sheet of stainless steel and a poorly-copied page of instructions. Instead, to my delight, I received a fully-formed and punched recess, complete but for some rivets, and of good quality.

I'm changing the design of the F-312 parts that extend aft from the center engine mount bolts. As designed, these do not attach to the spar bulkhead. In the RV-4 plans, the equivalent parts do attach, and I felt that was a better design. I'm not doing it exactly like the RV-4 so I spent the work time I had today coming up with the details and making a couple of the angles which will rivet to the F-303 web for this. I had to work up the geometry and figure out the assembly sequence.

Bruce, when you called, I didn't get your contact information. Would you please call back when it's convenient? Thanks.

Dave
 
Rob wrote in and sent me this photo along with this comment:

"In the photograph which was taken during my pre buy inspection you can see the crack.

The red dotted line is the gusset that was welded onto the mount. This gusset necessitated running the brake lines up the front of the gear leg which was no problem. Now that I have seen your mod I wish I had added that also. We did a similar mod to mine on the RV 4, but on the RV 6 we ran another tube from the front of the leg tube to the attachment points in the middle of the firewall to reduce the torque loading as well as gussets similar to the ones dotted in red below."

141m4id.jpg
 
I've been deburring the various bulkheads and have found a few small issues. I've got a query in to Van's for these but thought that you might be interested in seeing them.

The seat rib bulkheads have narrow flanges on the seat pan side. Here's the narrowest, on an F-314. The others aren't as narrow.

dep4rt.jpg


Here's more of an overview:

14b5302.jpg


It looks as if there are supposed to be three places where I need to drill some holes. Forward is to the left. The left-most hole location is for the aileron pushrod and is in the plans. The middle hole is shown in an isometric sketch in the plans, and the right-most hole isn't shown at all. I'm happy to have the opportunity to save a few grams but wonder about the deformation of these ribs in a crash with the holes in place.

2drhb9.jpg


The firewall, which incidentally came with pre-punched or drilled pilot holes for the engine mount bolts, has curiously crude side flanges, even for an RV-3B. Anyone encountered this before? How about the shallow return lip?

mhrq81.jpg


and

19w5yr.jpg


I decided to make a pass-through hole through the spar bulkhead webs for electrical and pitot-static lines, so that I could leave those in place if I pulled the wings off. I haven't made the equivalent holes at the ends of the spar webs yet. The hole is 1 3/8" diameter, mostly because I had a hole saw that size. The flanges are .040, thicker than the .032 web, mostly because I didn't want to do a structural analysis. I later added six rivet holes per doubler.

2q32ihd.jpg


Finally, as I was deburring parts, I came across the elevator bellcrank, F-339. Except that it wasn't F-339, in my kit, it was F-635, a nicely pre-punched part that Van's kindly included in the kit. Since I couldn't deburr it without separating it into its three pieces, I decided to enjoy the luxury, fleeting as it was, of building a pre-punched assembly.

2qsyo3r.jpg


If those photos aren't visible, try here, here, here, here, here, and here.

Dave
 
Van's basically said:

For the narrow flanges, adjust the rivet spacing to fit.

Drill the lightening holes. (Done.)

The firewall flanges are supposed to be flat, not with the return lip. (Done.)

The front flanges of the seat ribs, F-314 and F-315, need to be cut off. Haven't done that yet.

Van's tosses in RV-4 parts here and there without bothering to update the plans. The tailwheel spring mounting bracket, F-309, is actually F-409 and while it can be trimmed slightly it looks as if it'll fit as-is, although the spacing of the aft two bulkheads will need to be adjusted slightly to suit.

The seat bulkhead top, F-305B became F-407B. I know there are others and will try to point them out as I come to them.

The various pieces are deburred and mostly ready to attempt to assemble them into a fuselage. The F-303 spar bulkhead front and back parts are assembled to the spar simulator:

25jw1tl.jpg


Time to set up the Fry Jig. This will be especially fun because the jig is for an RV-4 and this is an RV-3. Plus I already know that much of the hardware is missing. On the plus side, I've got a set of instructions for this particular model of jig so I know how it's supposed to go together.

I brought the jig home from the hangar and it's been in the shop, folded. It's much easier to work around folded, and much less useful as a jig that way.

67jont.jpg


The instructions suggest placing the jig on its side and unfolding it. I rolled it outside and and unfolded it there and brought it back into the shop. It was totally manageable. Here it is unfolded. Yikes, that thing dominates the shop! This is going to be a skosh awkward.

jq6hb5.jpg


Here are the bits and pieces that came with it. I already know that most of the hardware is missing and will try to buy replacements as I learn what I need.

25ajin8.jpg


If those photos aren't visible, try
here,
here,
and here.

Dave
 
Lining up the jig and figuring out how to line up the firewall is interesting. One of the things that make it interesting is that the jig is an RV-4 jig and thus wasn't intended for an RV-3. Another is that the firewall itself is not the most precise part of the kit.

The firewall came pre-punched for the corner engine mount holes but not the more recent 5th and 6th mount bolts. Since this is an RV-3, I'm suspicious of shape and alignment of factory parts and checked and:

a) The 4 holes weren't square and true to a rectangular pattern,

b) They didn't - any of them - match the plans locations,

c) They didn't - any of them - match the engine mount bushings,

d) The firewall itself didn't match the plans layout dimensions. It wasn't too bad near the bottom but was narrow at the top.

I drew a full-size firewall pattern on a large piece of paper and moved the firewall around on that to obtain a "best fit" location. Then I transferred the vertical centerline from the drawing to the firewall.

Putting the engine mount on the firewall, I adjusted it so that the bottom tube lined up with the bottom flange of the firewall. The bottom flange is about 0.2 degrees off from perpendicular to the centerline, though. I marked this mount/firewall location to identify where the holes should go.

The firewall holes are 3/16 diameter and can all be moved to suit.

Dave
 
The Engine Runs!

Went out to the engine shop today to watch the first run. The first run in Colorado and the first in over a dozen years. My new but long-stored engine had previously only had a short factory run-in.

For the history, please see posts #31 and #220. The engine was built in 2002 or 2003, factory preserved, and sat until now. As you might guess, I was quite interested to find out what it was like inside, and swapping the factory 8.1:1 pistons with 9:1 gave us that opportunity to look and see. Joe, the engine guy, said it was "very good" inside.

This shop installed a pair of P-Mags with auto plugs, 9:1 pistons, a tiny lightweight Sky-Tech XLT starter, a fuel pump, the carburetor, B&C alternator and some of the adaptation for the constant speed prop. Not all, though, since the test club for this run was a fixed-pitch.

241p7jr.jpg


or here.

The run only lasted a few minutes and never got above 1,600 rpm. The engine started on the first or second compression stroke and was running before I expected it to be.

Everything was fine.

It was worth the trip to Greeley, CO.

Dave
 
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I'm slowly working on getting the fuselage jig ready. Like the jig outlined on SK-39, the Fry jig intends for the firewall to be mounted 3/4 inch from the support members. David Howe advised me that this doesn't leave enough room to easily get in for riveting, and to increase it to something like 4 inches.

Here's my first pass at stand-offs. Riveted aluminum, they suffered from a distinct lack of precision between the two ends, for both position and parallelism. One issue is that the angles weren't 90 degrees, hence the bend in the post. Their chief advantage is that they only needed short bolts at the ends.

You can see that due to the gusset on the frame, that I needed either the 3/4 inch stand-offs or ones around 6 inches. With any length in between, the firewall won't fit.

dv1cl.jpg


The second version was surprisingly easy to build. I trimmed some tubing to just under 6 inches, and cut some 1 inch holes in some plywood using a hole saw. That gave me the centers, which in this case had nicely centered 1/4" holes from the pilot drill. Using some of that excellent G-flex epoxy (I like the thickened kind, p/n 655), I glued them in to the tubes. They are slightly under-flush so that there's no possibility of them affecting the trueness of the ends.

biromo.jpg


Then I ran some threaded rod through the stand-offs and put a fender washer on the end just to have something to screw the nut down to. This will work.

I don't have a lathe or mill, but my disk sander has a bed that's true. It was a simple thing to sand these with true ends. The lengths are within less than .025 from the longest to the shortest - good enough, I think.

8x54cl.jpg


Next up was re-inventorying the aluminum angle. There's a lot of that. It'll be easy to identify the raw material for the different parts.

SK-39 shows some dimensions that don't seem to correspond well to what drawing 21 shows. I'm going to tweak the jig (it needs adjusting in any event, being designed for an RV-4) to match drawing 21. In the sketch, it's the red dimensions,

5fm1pz.jpg


and on the drawing, the green ones. Note that the jig holds the fuselage upside down, and that the front is to the right in the sketch above, and upright and to the left in the drawing below.

1h46ts.jpg


I think this is just another RV-3 thing but if there's something I'm missing, someone please let me know, okay? -- Thanks!

If that photo link fails, try here, here, here, here, and here.

Dave
 
The Big Picture

Just so that it doesn't come as a surprise some day....

My overall plan is to finish this airplane, fly the restrictions off it and do a reasonable job of flight-testing it, play a bit, and then sell it.

Depending on it's performance, I might see if I can tweak the speed up, but this is unlikely, given the low RV-3B redline speed. If it were up around 250 or 275 mph, sure, but it's only 210.

I expect to fly some cross-country flights in it since I like that more than acro. In fact, I plan not to do any more acro than I have to for the flight test program, and might hire that out.

So that's the overall plan.

That's been the plan from Day 1, I just haven't mentioned it before.

Dave
 
I measured the positions of the oil filter and the prop governor and for those of you who might be tempted to use these, here are their locations. They both stick aft of the firewall by about 1 3/8 inches, but the oil filter needs an additional 0.54 inches of clearance aft to remove it.

The oil filter adapter is Lycoming's.

The prop governor is the PCU 5000X. I didn't show the arm on the governor, but it sticks out past the rim of the governor about 3/16 inch, more or less. It can be positioned around the circumference to your wishes.

i6yzcg.jpg

28qyrep.jpg


I included dimensions from two locations for each datum to help reduce errors. And I used the engine mount's firewall attachment points since they were easily accessible.

As far as I can tell, the standard Van's F-601K-1 firewall recess won't fit these particular components together.

Dave
 
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I've been working on the firewall. The outer stiffeners are fit and drilled. The firewall recess needed to be larger, though, and I decided to make it of grade 2 Titanium because it's lighter than stainless steel.

In case you're wondering about the dissimilar-metals issue and corrosion, Titanium is quite close to stainless steel so those ought to be just fine. Aluminum and stainless or aluminum and Titanium are considerably farther apart, with the latter combination being slightly worse for corrosion than the former. Given that the aluminum stiffeners are riveted to the stainless steel firewall by aluminum rivets, per the design of our RVs, and have proven acceptable, I expect that this will be okay too.

Here's an excerpt from FAR Part 23.1191:

"(h) The following materials may be used in firewalls or shrouds without being tested as required by this section:
(1) Stainless steel sheet, 0.015 inch thick.
(2) Mild steel sheet (coated with aluminum or otherwise protected against corrosion) 0.018 inch thick.
(3) Terne plate, 0.018 inch thick.
(4) Monel metal, 0.018 inch thick.
(5) Steel or copper base alloy firewall fittings.
(6) Titanium sheet, 0.016 inch thick."

The firewall is .016 stainless steel. I chose .020 for my Titanium simply because it was readily available through McMaster, and I chose grade 2 for price and workability (grade 5 would have been much more expensive and considerably stronger as well as being more difficult to work). The piece that I received came with a material certification that showed that it was as strong as 2024-T3, which I figure is probably good enough.

I trimmed off the slanted part of the stainless steel firewall recess that I got from Van's as part number F-601K-1. Sure hated to do that, that part is a very nicely-made, prepunched and pre-bent item. If I had the B&C oil filter adapter that Randy installed on his airplane, that would work as-is, and I came close to switching to that one. However, my engine now has the Lycoming oil filter adapter which points the filter straight aft and it needs more room. So I cut that thing off and made an aft pan of Titanium, followed by two side panels, followed by a bottom panel, which wasn't built when I took this photo.

The Titanium is the flat gray part below the more shiny stainless steel part. It's the part with the letters stamped on it.

34xkztg.jpg


Once the box was located and in place, it was obvious that the firewall stiffeners shown on drawing 19, below, were inappropriate.

2qnuxyp.jpg


Van's support was helpful and provided guidance. I haven't built that part yet so I'll end here.

Every-so-slightly off-topic:
From time to time people suggest that aluminum fittings can be used for firewall pass-through fittings. Note that for certified aircraft, those fittings must be steel or copper-base alloys. Interesting, eh?

Dave
 
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Firewall Recess

The firewall recess is fabricated and the cut-out made in the firewall.

Sure prefer working with the grade 2 titanium compared to the stainless steel.

wqqy5k.jpg


The firewall cut-out was made with a 3" disk in an air die grinder, and the rough cut-out went quickly. It took more time to clean up the edge than make the cut. I used a hand Adel nibbler to get to the final shape, finishing off with a Vixen file and then a mill file.

72vtc1.jpg


The blue-covered tabs on the firewall are shims that go between the perimeter angles. Just haven't removed the blue vinyl yet. I thought about it and decided that these would be a good place for a bit of structural bonding. They are glued on in this photo.

If those photos don't show up please try these redundant links. Here and here.

Dave
 
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Engine, Meet the Firewall

Now that the engine is back and built up, and the firewall is finished, I figured that I'd better see just how poorly they fit together. It's a lot easier to fix it now than after the fuselage is finished.

Turns out that they fit together well. Best of all, the oil filter and the prop governor fit into the firewall recess that I built.

Gotta thank Andy Hill and David Howe for technical support through this. Thanks, gentlemen!

Here's the engine hanging on the hook with the firewall in place. The bottom portion of the firewall recess is grade 2 titanium, an approved firewall material that's lighter and more fun to work with than stainless steel. The top is stainless steel.

It's not obvious, but the upper horizontal angle is cut down from 1" x 1" x 1/8" angle to 3/4". I left the full width under the steel fittings, and you can just see that at the right side. This let me locate the recess 1/4" higher than otherwise.

n1axwh.jpg


Since my engine has the Lycoming oil filter adapter which puts the filter straight aft, plus having the governor, the recess position was important. This photo shows that it's okay.

2a7bjnq.jpg


And here's a look at the right side.

11snpyc.jpg


The recess's finished inside dimensions are 7 7/8" wide, 10" high and 2 1/4" deep.

If those photos ever disappear, you can find them redundantly hosted at
Here,
here,
and here.

At the end of the day, the engine was back on its pallet and the firewall home to the shop.

Dave
 
Earlier, I'd decided to use 1" x 1" x 1/8" upper longerons instead of 3/4" x 3/4" x 1/8" just to get a bit more edge distance in a couple places. But since I didn't want to carry close to a pound of extra weight around, I needed to remove the excess width in the rest of the longerons. Here's the overall plan for the shape that I wanted to end up with.

Cut plan
24zkncl.jpg


I asked around and one friend had successfully done this job on his non-RV with his bandsaw, and offered to help me. I tried to do it on my bandsaw with some scrap and that didn't go so well; his blade guides are superior to mine. A couple guys suggested using a router but I didn't know how to set that sort of affair up. Plus, after I'd built my kitchen cabinets and turned the shop into an RV factory, I'd gotten rid of my handy general-purpose router table. The final suggestion was to have it machined by a machinist for big bucks. I tried to get a quote from a local water-jet company but they didn't bid on it. Their informal estimate was comparable to the machinist's.

So I started thinking.

After gathering some things that were laying around the shop or in my basement, I constructed this router table. Previously, I'd bemoaned that I no longer had the router table with which I built my kitchen but this turned out to be a good thing; that was a general-purpose tool and I made this one specifically for this, and it's better.

Longeron Routing Tool
e6f4h1.jpg


The plastic guides use UHMW which gave the right feel; I push the angles through by hand. The aluminum bar is a 1" x 2" tube and it would have been better to use 2" x 2" but no complaints - this worked pretty darn well. The bar is adjustable by changing the clamping position at the right end, and the leverage gives slightly more than a 3:1 mechanical advantage; it's not a vernier but it's close enough.

The design both closely guides the angles and supports them on the non-cut flange, while allowing some movement up and down. But not much, since one of the legs of the plastic blocks prevent most movement there. The fixture also lets the cutter get readjusted axially without changing any cutting position if that's needed due to wear. And while it was still cutting well, I thought I saw some wear after three of the four sides was cut and moved the bit to a fresh position.

The router table now has a few pieces of UHMW chafe tape which served two purposes - it let the angles slide smoothly and it kept them slightly above the table so that the chips didn't cause binding.

My bit is a 1/2" or 3/8" steel (that is, not carbide) spiral bit. It's
this bit. The spiral deflects some of the chips into the router instead of away from the router. The router is mounted underneath with the bit upward and the chips don't fly up, which is good. The bit, by the way, is holding up better than I thought it would. It cost less than $30. The router is an adjustable-speed Dewalt, running about 18,000 rpm.

I needed something that would let me adjust the depth of the cut before hitting the aluminum and those divots did the trick. Yes, they completely used up one 2" very coarse sanding drum - it was worth it. I did both longerons at the same time, clamped together. First I used an electric drill. It got very hot. Then I used a Sioux air drill. It got very cold. Physics in action. Then I brought out my industrial Ingersol-Rand air drill and it just chugged through the job. A friend of mine used to say "Don't force it, Dave, get a bigger hammer." And for this job, this was it. Of course the air compressor got a real workout.

Longeron Divot
16bhkef.jpg


The router chips fly all over the shop. I'll spend next week cleaning up. I'm using a couple of small pieces of 4x4 near the router as simple chip deflectors and that keeps hot chips off my wrists and avoids some of the mess. When I first started, I found immediately that I needed to wear a long-sleeve shirt.

I tried two lubricants. One of our local RV group recommended WD-40 and that was the first one I tried. It turned out to be hard to apply without a lot of overspray, even using the tube, and made a considerable mess. With this lubricant I could cut a width of about .070 inches. Then I tried Boelube liquid, which is easy to apply, leaving little mess, and permits cuts up to at least .125 inches. It does smoke, though, which the WD-40 didn't. I regard Boelube as far superior to the WD-40. I am not a WD-40 fan.

The longerons are long enough that I needed to keep the garage door open to rip these. Something to consider.

I had a couple of those adjustable rollers that you can use to support long pieces being ripped. They worked. Handy things.

The finish isn't all that great.I'd say it's something around a 125 micro inch finish but it's been so long since I've worked with a comparator my eyes just aren't calibrated any more. I'll have to smooth the edges. The edges also picked up a burr, and a few swipes with a file took care of those. I was aiming at .750 or more and with the rough finish, I stopped at about .010 or .020 extra. It'll give me some allowance for smoothing.

Router Cut
2z7rkb5.jpg


Now that the routing's finished, I've still got to smooth the edges, but at least I know how to do that.

It's good to be back to work on the RV-3B. The last quarter was difficult to get to work on it. One of the things that I did was make this glove box, from scratch, for a friend who's re-doing the panel on his non-RV. Seeing that has convinced me not to put a new panel in my Cessna 180. On the plus side, he gave me his excess aluminum, so I got some .025 and .040 sheet, plus some 3/4 x 3/4 x 1/16 angle and a stick of Van's .025 bent angle. These things are always handy.

Glove Box
zv52js.jpg


Alternate photo hosting is here,
here,
here,
here,
and here.
Dave
 
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With the longerons trimmed down and smoothed and deburred, it was time to bend them. I was looking forward to this, because David Howe had loaned me a tool he'd made for the job.

2125vra.jpg


I cut the front edge of the longerons to their proper location before starting, so that I'd have a reference to measure from. Since my longerons weren't simply plain angles, the position mattered. Once that was complete, I marked the bends and put a longeron in the vise. Here's where a heavy stiff vise came in handy.

1zhwdj.jpg


Since the angles have a lot of spring-back, it took several tries to get the bends right. And then there was invariably a cross-bend that somehow settled in, which I had to remove, and that affected the first bend.... Not really a big deal, but of course it took a lot of checking and tweaking. With each iteration, I had to remove the tool so that I could clamp a straight-edge in place, then remove that and replace the tool.

On the other hand, it only took one session in the shop to complete both longerons and there was very little of that feeling that something bad is gonna happen. It helped that I had a spare longeron blank on hand just in case, not yet cut down but available.

I haven't tried bending them with the mallet so I can't compare that technique.

Here are the longerons laying on the RV-4 Fry Jig, which I've mostly tweaked to become an RV-3B jig, its immediate duty. The longerons are still too long and the F-311 bulkhead support hasn't been built yet.

125i4g4.jpg


The next step was to trim the longerons closer to final size (I left them 1/2" long for now) and adjust the height of the F-303 spar bulkhead by trimming its upper edges to match the call out in the plans. Of course then I wanted to see it in place on the longerons. I had placed an F-311 bulkhead, the aft-most one, in place merely to keep the longerons stable. This spar bulkhead, though, it pretty close to being in the correct position.

190d8p.jpg


Thanks, David Howe, for the tool loan!

The photos are also hosted on Imagebam.com
here,
here,
here,
and here.

Dave
 
It Only Took the Whole Weekend

After 42 checks (I'm not kidding) of the straightness of the spar bulkhead, I finally drilled a few holes and clecoed on the F-358 or F-450 bottom front longeron pieces. At one point I was about to drill them when I thought that perhaps I should check the 1 degree incidence angle. Good thing I did, too, because it was wrongly set to 2 degrees. Some errors had crept in. At that point I'd only made about 25 or 30 checks of the straightness.

There aren't all that many things to tweak to get the spar bulkhead straight, you know. First, I checked the firewall itself and that was fine. Good to know but not really a serious reference for this bulkhead, except for fore-aft position. Then I checked the fit at the upper longerons which are resting directly up on the jig and aren't attached yet. That needed adjustment. You can tell they're the upper ones since they're on the bottom.

After that, it was only a matter of moving the bottom position a bit one way or the other and checking things. I knew it was the bottom since it was on top.

At this stage, as far as I can tell, the spar is straight in yaw to the limits of my measurements, which I figure is 1/32 inch over its width of roughly 2 feet. It's straight in roll to my ability to measure it, but I can't quantify that. The incidence angle isn't perfect, though - right now it's about 0.15 degrees less than the 1 degree that the plans calls for and I can still adjust that, since the upper flanges aren't yet clecoed to the longerons. Those are the clamped connections at the bottom of the structure, which of course means that they are at the upper longeron.

20f963k.jpg


I added several labels to the Fry Jig, identifying the right and left sides of the airplane, just in case. Up and down is just something I'm trying to get used to. The fuselage is upside down at the moment. It's all perfectly clear, right?

One of the things I was interested in was to see how critical it was to measure the yaw error from the center of the jig or the same sideward position on each side. I was measuring from the bottom side corners of the bulkhead, aftward to a jig fixture which itself was aft of the tail bulkhead. I could (and did, several times during the proceedings) use a plumb bob to verify that this reference position was directly above the centerline. Fortunately that reference position was far enough aft that 3/16 inch cumulative sideways error only would cause a 1/64 inch error in the length of the measurement, and I'm pretty sure I kept things closer than that.

Here's a tip for the diligent reader: I'm using a Starrett 87B mercury-filled plumb bob that's the same as what the USAF experts used in the special weight and balance hangar at Edwards AFB many years ago. I'd expect that any mercury-filled plumb bob would be substantially as good. The mercury filling helps dampen out any motion of the plumb bob, as well as adding some useful heft. It's a sweet tool, too bad it's out of production now.

If the photo has disappeared, try this alternate host site.

Dave
 
The plans, on Drawing 22, are just a bit vague as to where to bend the F-305 seat bulkhead. Here's one side of the bulkhead after I bent it.

8wxq83.jpg


You can see where I made the bend; some other builders placed the bend where I did. The red dashed line shows where yet other builders have made that bend.

The plans show that the bend is to be 4 inches above the bottom of the bulkhead. In the picture, there are two clear points that the distance can be measured from, shown by the black line and the blue one on the right. I believe that the black one is what is intended but I'm not certain. 4 inches from either places the bend in between where I bent it and the dashed red line. If I used the black line as the measuring point, the bend would be immediately below the recess for the longeron. If I placed it 4 inches from the blue line, it would be in that recess.

Here is an excerpt of the drawing. If the position of the bulkhead at the upper longer is held fixed, then top of the turtledeck would be slightly forward of the design position unless it, too, were bent. I've shown the bulkhead position using my bend, with the green line.

f0wa3d.jpg


If the bulkhead were bent in the higher position shown by the dashed line in the first photo, the bulkhead would lie on the red line shown below.

35kilqc.jpg


These are small potatoes, all in all, and perhaps they're mere quibbles. I'll check the differences and see if I need to adjust the position of the bulkhead on the upper longeron - that's where I am today:

2zhr0qd.jpg


The longeron-bending tool I borrowed is shown to the right of the bulkhead where I"m using it to adjust the shim at its clamp (you can barely see it - it's the aluminum part with the #40 pilot hole in it at the jig) so that the longeron sets at the correct angle. The bending tool makes this trivial.

Note one of the "Left" labels on the jig; I really don't want to get confused.

Incidentally, the F-305 seat bulkhead bottom halves get riveted together. Haven't done that yet, and the clecos were in my way, so I connected them together with a structural bond.

The photos are also hosted
here,
here,
here,
and here.

Dave
 
I understand the OCD of measuring something 42 times, but only an engineer would count the number of times he measured! :D I'm sure you will have the straightest RV3 fuselage ever built!
 
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