VansAirForceForums  
Home > VansAirForceForums

-POSTING RULES
-Advertise in here!
- Today's Posts | Insert Pics

Keep VAF Going
Donate methods

Point your
camera app here
to donate fast.

  #241  
Old 05-01-2016, 06:12 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default 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
Reply With Quote
  #242  
Old 05-09-2016, 09:30 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default

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.




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

Last edited by David Paule : 05-11-2016 at 09:56 AM. Reason: Reduced pixel size on lower photo & added recess p/n.
Reply With Quote
  #243  
Old 05-29-2016, 08:33 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default

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.



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



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

Last edited by David Paule : 05-29-2016 at 09:14 PM.
Reply With Quote
  #244  
Old 06-10-2016, 05:33 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default 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.



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.



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

Last edited by David Paule : 06-22-2016 at 09:16 AM.
Reply With Quote
  #245  
Old 06-26-2016, 09:14 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default 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.



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.



And here's a look at the right side.



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
Reply With Quote
  #246  
Old 07-03-2016, 09:24 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default

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


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


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


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


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


Alternate photo hosting is here,
here,
here,
here,
and here.
Dave

Last edited by David Paule : 07-04-2016 at 10:20 AM. Reason: Misspelled word
Reply With Quote
  #247  
Old 07-07-2016, 09:31 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default

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.



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.



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.



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.



Thanks, David Howe, for the tool loan!

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

Dave
Reply With Quote
  #248  
Old 07-10-2016, 08:59 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default 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.



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
Reply With Quote
  #249  
Old 07-17-2016, 01:03 PM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,070
Default

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.



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.



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.



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:



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
Reply With Quote
  #250  
Old 07-17-2016, 06:02 PM
KatieB's Avatar
KatieB KatieB is offline
 
Join Date: Jun 2010
Location: Belton, MO
Posts: 1,144
Default

I understand the OCD of measuring something 42 times, but only an engineer would count the number of times he measured! I'm sure you will have the straightest RV3 fuselage ever built!
__________________
Katie Bosman
EAA Homebuilt Aircraft Council
Rebuilt most of SNF tornado victim RV-3B Tony Boy II (had to sell him, but he's flying!)
VAF Dues Paid 2021!
Thoughts & opinions expressed here are my own, and not those of my employer.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 07:17 AM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.