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RV-3B Dave's in Colorado

Sooner or later you just have to put the measure down and pick up the drill and make a hole, or a cut, or a bend!
I think I bent mine where you have, (4" up on drawing #21) then with taking and using the added measurements from the firewall back to the top of F305 (turtledeck) I find that it leans back just slightly from the fuselage line of F305. That's where I drilled it, looks fine to me... I am loving building this thing.

Russell
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Well, Sen. Everett Dirkson might have said, "A billion here, a billion there, pretty soon you're talking real money."

This wasn't money but just a lot of careful adjusting. For some reason the spar bulkhead needed that.

A little tweak here,
a little tweak there...
it adds up.

As you know, I'm not real good at this. Sure don't want to screw it up, especially that part of it.

Dave
 
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I think it helps to look at the -3 as something that grows organically or artistically, not necessarily with mathematical, repeatable precision. Not to say my measurements aren't spot-on, but I built my parts to fit the existing parts, not necessarily the plans. Should turn out ok. :D
 
I ordered another dozen #40 drill bits and half a dozen #30 bits a few days ago. When I bought this kit I ordered a bunch of these from an otherwise reliable vendor and those bits were not so good. A competitor sent me some samples and I've been buying bits from them since.

Made the F-315 outboard seat ribs. These have that 1 1/4" strip of .025 in the saddle. The plans and one of the builder's logs show that it should be under the rib flange. Most of the other builders seem to rivet it to the top of the flange. Don't know if it'll be a gotcha later, but I riveted them to the top, too.

These seat ribs fit reasonably well except for the rear flange, which I cut off and replaced by an angle.

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With these in place, the rear spar was mostly in position. Some more side to side tweaking and it is.

That let me trial-fit the F-314 intermediate seat ribs, shown on the next photos. These particular seat ribs come with a front flange that needs to be trimmed off completely - these ribs rivet to the .063 angles riveted to the spar bulkhead. The plans don't hint of it, but the webs above and below the angle that's riveted to the F-303 spar bulkhead need to be cut away so that the spar splice plates can be inserted later. If you don't do this now you'll be in a bind when you assemble the plane.

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The back of these ribs also needs some trimming to clear the rear spar carry-through. I haven't decided yet if I should replace these rear flanges too. In this photo, the near rib is the intermediate F-314 rib and the far one is the outer F-315 rib.

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I haven't fit the center F-313 rib yet but the short F-304 bulkhead is trial-fit in position.

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The F-304 bulkhead's fore/aft position isn't dimensioned in the plans, but it seems to fit best about where it's supposed to go, more or less. The heavy angle on the belly is merely a skin reference which I'll use for positioning the control mixer bearing mount, F-340. I made those parts but have some issues with them which I'll discuss later.

There are a few other missing parts, too, aren't there?

Those rear-spar positioning tools I made earlier show up in several of these pictures, clamped to the wood spar simulator.

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Yesterday was Oshkosh Monday and for a while I was listening to the Fisk feed while I worked. Reminded me of flying that, which I did a number of times before I quit going. That approach was fun, about as much fun as an approach to some of the back-country airstrips.

Another photo hosting site has these copies:
Here,
Here,
Here,
Here,
And here.

Dave
 
I'm building up the seat ribs.

In this photo, the important thing are those disks on the flange. These are magnets, strong rare-earth ones. They do a decent job of holding the rib flange to the web of the F-304 bulkhead. They are handy thing to have, don't use them often, but they're effective when I do. There are other magnets of the far side.

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I was going to drill the holes for attaching the bearings to the mixer and found that on mine, the mixer is mis-cut. The markings show where the hole is supposed to go. I moved it slightly, maintaining the same edge distance as the plans call for. Just a head's up here on this one.

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The mixer itself is 9 5/16 wide. The space for it is slightly more than 10 inches. Because the intermediate F-314 seat ribs have some beads on the lightening holes, which you can see in the next photo, the angle brackets don't rest against the webs outside of the space. They do fit reasonably well (which means that they kinda fit) inside, but then there's no room for those triangular flanges.

The brackets themselves are long enough to pick up both the fasteners to that short bulkhead, the F-304 one which is still in blue, and the .063 angles which are riveted to the F-303 spar bulkhead on the right. However, there's another bead for the next lightening hole to the left which takes up much of this space at that end of the bracket. This is still in progress.

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Those rectangular tubes above the spar simulator are nothing more than spacers. My simulator came out a little shallow in the center area, my fault, and these keep the flanges the right distance apart. Ugly, aren't they?

The photos are also hosted here, here and here.

Dave
 
Here is what I did Dave, cut and flattened the circular flange. I did put the splice plates in before riveting all this section together too. :)

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Russell, how did you flatten the flanges?

And please tell us about the filler inside the hole, too.

I don't think I'll do either of those here but I'd like to know how you did them.

Thanks,

Dave
 
Dave, The ribs came without the lightening holes in them so I just removed the bottom portion then tapped the flange down with a soft blow hammer. It went down smooth and had no adverse effects on the rib. At least I think thats how I did it, was a while ago now... My thinking was most likely to give the mixer bracket/bearing more support, probably doesn't make any difference.
Russell
 
Dave, The ribs came without the lightening holes in them....

Oh, yeah, that's right, I forgot. I'd cut them out so long ago that slipped my mind. A good example of the two rules of building RV-3s:

1. Do stuff in advance because you never know what will prevent doing them in the future.

2. Don't do anything until you can't proceed without it, because otherwise it'll interfere with something down the road.

I've decided that I'm getting a bit ahead of where I should be, and will go back to this after I get the bellcrank in. That way I can have the pushrod in and check clearances as I work.

Dave
 
I made two more of those tube affairs (reference post #240) for the tailpost support. Since my jig is an RV-4 Fry jig, the tailpost's jig position was essentially fixed. But these moved the aft bulkheads, the F-311 bulkheads, into the correct location.

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You can see that I'm using two of the bulkheads back to back. This probably looks normal to many of you. However, on the RV-3B, the plans call for only one of these. I'm taking David Howe's advice and adding the second.

Next, I placed the remaining bulkheads in position. These and the longerons which I cut and rough-fit will all need some tweaking. In most cases the bulkheads aren't planar. When I first placed them in position most of them were loose in the top longerons. That is, the longerons were spaced wider than the bulkheads. I moved the bulkheads to where they fit and moved the fixture's supports to suit.

In the middle of all this I noticed, one hot day, that one corner of the shop had a nice breeze. It was pleasant. Then I realized that there shouldn't be a breeze there, especially not a localized one, and about that time the compressor kicked on. I've got two regulators and run two flexible lines, 30 psi and 90 psi. The 90 psi line had a small split. I used it for a day or two and then went to HD and bought a replacement. The new line is 50' instead of 25' and while the additional length is nice, storing it is a bit of a pain.

One of the things that is not per plans is that the tailspring support that the factory supplied is the one for an RV-4. The plans show the RV-3 one but Van's doesn't make those. In fact, The List doesn't even show it. The RV-4 one is slightly larger than the RV-3 one and worse, it slightly larger than the space for it on the aft bulkheads. I trimmed it slightly and now it fits. As KatieB pointed out above, building an RV-3B includes a considerable amount of making things fit. In this case, besides having the end fittings being larger than they should be, the support is 1/16" longer than it should be. That's not so much but it affects the F-310 bulkhead position, and I doubled up those, too, again per David Howe's suggestion.

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There are still many pieces to fabricate and fit. I've nearly run out of those excellent Cleco side-clamps and bought another couple handfuls of c-clamps today.

In case the photos aren't showing, they are also hosted (in larger format) here and here.

Dave
 
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Looking good Dave - you're almost at the point where you can stop looking at the plans and just skin the thing using your experience!
 
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Dave , not sure if it would be possible but it would be good at this stage to try to setup F310 & 311 so as to get a better fit of the VS when you come to mount it to the forward HS spar. I think the length of the steel tailwheel spring mount locks in the spacing but it would be nice if that dimension was more accurate. As others have found I am looking at about 1/8 to 3/16 spacer to join the VS to HS.
The doubling up of those rear bulkheads is a good idea, especially F311.
 
I doubt that I can do that without tilting the F-310 bulkheads aft above the tailwheel support and then bending the 1 1/4" stabilizer posts forward slightly to compensate. I'm not going to do that.

Here's the area we're talking about. I am installing both bulkhead pairs so that their webs are facing each other, with the flanges on the aft one facing aft and the flanges on the forward one facing forward. That gap is where the forward spar of the VS joins the front spar of the HS (I forgot to label that area before posing the picture):

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Here they are as of a few minutes ago - and yes, this is VERY preliminary:

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I sorted through as many of the permutations of arranging those posts and the two bulkheads as I could but in the end, the geometry of the bulkheads themselves suggested where to put those stabilizer support bars. The bars will need to go on the forward face of the forward-most bulkhead of the pair. Having two bulkheads at both there and the F-311 location means that the additional bulkheads push the bars forward by a total of 1/16", and the tailwheel support itself is 1/16" longer than it should be. I know some people shorten that, and that would help here, but I don't want to do that either.

You did good to get that gap so small.

The photos are also hosted here and here.

Dave
 
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Agreed Dave it is really difficult to get an accurate measurement of how it will all fit when upside down on the jig anyway, (certainly bending the bars is out of the question). The plans allow for a spacer to be used when attaching the VS...
I am also using 1x1x1/8 angle for the the Fuselage to HS forward mount, the 3/4 x 3/4 looks too small for something that holds the tail on? Also allows for levelling the stab without having to shim.
 
I also used a 1x1 angle to attach the HS. Worked much better than the 3/4x3/4 in the plans. Also added a .032 shim under the angle in case I need to tweek the incidence later.
You will not know how big a shim you will need for the vertical until it is time to mount it. I needed 3/8 which I made out of a piece of 3/8 plate.
 
I've been working on the aft two bulkheads, and lately it's been mostly the F-310 pair that support the stabilizer mounting bars.

I decided to place the stabilizer mounting bars in between the two bulkheads of this pair for a slightly better fit between the horizontal and the vertical stabilizers. This pushed the forward bulkhead forward slightly and after evaluating whether to split the bulkhead to push the flanges closer to the skin and add a splice plate to reattach them, decided that shims would be preferrable.

I inserted the uncut bars in between the two F-310 bulkheads and clamped them in place against the tailspring support bracket. This let me determine where they'd intersect the upper longerons. I needed to know where to place the longeron slots for the bars.

In the photo, the bars poke out of the bottom of the bulkheads rather than the top simply for convenience; I hadn't made those slots yet.

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With the longerons marked and the bulkheads and bars removed, I had to figure out how to cut the slots. I didn't want to remove the longerons from the jig at this time and there wasn't room for a cut-off disk. If I'd reversed the orientation of a hacksaw blade in its saw frame, I could have used that. A friend suggested this Dremel cutter bit and it worked. I used some Boelube to lubricate the cut.

There were chips all over that end of the shop, just like narrowing down the longerons.

Here are the slots and some of the chips and the cutter. The slots still need some smoothing and shaping so I guess I know what's next in the shop.

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Another site also hosts the photos but in larger format. They are here and here.

Dave
 
Getting ready to install the tailwheel mount to the fuselage and encountered a bit of an issue. The tailwheel assembly, the part that bolts to the aft end of the tail spring, is loose on the tail spring. There's a couple degrees of free-play in the roll axis, even with the AN3 bolts all the way seated.

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Called Van's and was told that all the ones in stock were that way, and that these parts are common for the tailwheel models. There aren't RV-3B specific parts for these, in spite of the plans (which in any case show an obsolete version of the tail spring).

We discussed some options. I'd ordered some AN173 bolts, which are slightly fatter than AN3, even though I can get a bigger drill rod into these holes than the size of the AN173 bolts. That is, the AN173 isn't oversize enough to stop the free play.

My next idea was to epoxy the joint. My Cessna 180 has a similar joint and the last time I had to replace its broken tail spring, Cessna sent me some structural adhesive along with the new spring. Support said that might work but it was clear that he wasn't greatly in favor of it. My main concern is that if I did that, I'd probably never get it apart again, even if I wanted to.

Finally, Support said to tighten the bolts and go flying. I'm sure that there are a lot of RVs out there like that, but to me that's asking for some future problem. I didn't take that advice.

I called my mentor and he had what I think is going to be a better suggestion. Parts and tools on order and when I do it, I'll report about it. Glad I have a mentor, thanks, David.

Since several previous builders found that the fuselage skins, in particular the bottom aft one, fit poorly, I thought I'd bring mine home and have a look.

First I had to dig through a lot of white packing paper. At least I'd marked it.

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Resting in place.

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Not exactly a precision fit, is it?

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This end is a bit better.

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Doesn't appear as if Van's has fixed these yet, does it? On the other hand, my kit was shipped April 2012, and I don't know what they're shipping now.

These photos are hosted in larger format at a different site for redundancy:

First photo,
second photo,
third photo,
fourth photo,
and the final one.

It seems that every few years one photo hosting site or another loses the ability to forward the photo links in VAF's threads. It's the embedded links that bring up the photos that you see, and when they quit, it's frustrating.

I've been using TinyPic for the photos here but decided a while ago to provide an alternate hosting site just in case. I'm using Imagebam for these others. Since these are just links rather than code that says "display this," I realized that I could provide more pixels for people that might want them. And here we are.

Dave
 
Dave,

The best place to put most of the bulkhead flanges that fit poorly is in the trash. Much easier to just cut them off and make new ones.

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I assume you're going to give taper pins a try on the tailwheel spring?

Tony
 
When I bought the kit, I also bought some of these F-803CPP tabbed flange strips for just that reason.

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Yes, I'll be installing tapered pins, good thought. Details when I'm actually doing that.

The photo is also hosted here.

Dave
 
Lately I've been working on my replacements for the F-312 ribs. These run from the firewall center engine mount bolts to the main spar bulkhead, a lot like on the RV-4. The RV-3B plans calls for a rib that doesn't quite get to the spar bulkhead. It's slanted and terminates on the belly skin just forward of the wing spar splice fittings.

First I had to lay out the part and cut it to shape. You should be able to see the layout. I have a borrowed air nibbler that leaves a spiral kerf. In this case there was a narrow edge that was attached so I had a rare two-stage squiggly.

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Once the end fittings were made an a plan of construction developed, I made and clecoed in the pieces. Here's the left one from the bottom left. You can see the two spar bulkhead attach points. Right now they are lined up on 1/4" shims. These fittings get drilled to the ribs and installed after the splice plates are in place on the spars

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Here is the front flange of the right rib and its engine mount bolt attachment fitting. This section is much like the RV-3B plans.

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This shows the inside. The upper 3/4 angles are on the inside like on the RV-3B version. The spar bulkhead end is slightly narrower than the forward end to give me slightly more leg room. When I sat in an RV-3, I felt this was worth having -- and I'm neither tall nor excessively fat. I do have wide thighs, though, and that's where this extra room should help.

And yes, you can see that my roughly-bend flanges left the ribs curved; I'll flute those flanges later.

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When I was lining the rib up and figuring out its shape and dimensions, I used a skin simulator to locate the rib flange. The simulator was just a piece of 3/4 angle from the firewall area to the spar bulkhead splice F-303F.

These photos are also available on this other server in case Tinypic goes away. Here, they have more pixels.

Here,
here,
here,
here.

Dave
 
Bendy Times

On the RV-3B, the bottom forward lower longerons are riveted to the F-303 spar bulkhead. You can see this on drawing 21 pretty well, with the lower longeron riveted pair inboard of the F-303E side plate. For the plate and the spar bulkhead, see drawing 11.

The side plate means that the lower longerons attach inboard of the skin by .063. No concern, though, as SK-45 shows how to deal with that:

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That seemed a bit of a kluge, frankly. I thought perhaps that I might be able to joggle these longerons at that intersection. Yes, the lower one was 1" x 1" and they were both 1/8" thick, but even so.

If you'll go back, back to post #240 or so, you'll see a longeron bending tool. Look closely. Notice how this is not a hydraulic press? And how there aren't any tool steel forms standing by? I noticed that, too. Both of these, I might add, would have increased my confidence considerably.

This has been a week that's just been too full of non-RV stuff. Here and there, I've had some time to play, though. And my scrap bin had a number of 6061-T6 angle extrusion cut-offs that were the right size and the right material and which I didn't seem to actually need at this moment. So I played.

After I ruined most of my 1" angle scrap, I'd learned the techniques.

1. Start at the bend farthest from the end and clamp the end in a vice with soft jaws.

2. Allow 1" for any compressive bend on the upstanding flange, and 3/4" for any tension bend on that flange. Allow 2 3/4" between bends.

3. Bend it a bit. Reposition the tool and correct any out-of-plane errors.

4. Move to the bend closest to the end.

5. Remember which way to bend it. Bend it a bit. Reposition the tool and correct any out-of-plane errors.

6. Go to the fuselage and see how far off it is.

7. Take it back to the vice and items 3 through 6 as needed.

Here's my successful trial piece. I've clamped it to a piece of straight angle so I could see the joggle. The bend on the left is marked 3/4" and it's from this piece, correcting errors, that I learned to make it 1".

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Since I took that photo, I've joggled all four of the lower forward longerons and have yet to do the ones on the F-315 seat ribs. It's slow going but it is possible.

The pictures are also here and here.

One small thing worth mentioning. You might ask, well, structurally, which approach is better? And the answer is that I think Van's method shown in SK-45 is better. It's slightly lighter, slightly stronger, and doesn't need a tapered shim on the transition section like my joggles do. However, the strength is only better if you make a careful fillet radius at the change of section. If you leave it sharp-edged, then the joggle is probably less likely to have issues in the distant future.

Or maybe not. The bending, after all, does introduce its own cold-working changes to the material. Want to see an extreme example of that?

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In this bit of scrap, I was still using a negligible length to absorb the bend. And I positioned it at a #40 hole. You can clearly see the over-stress as the bend put the hole and the area at the edge in tension. And the hole has elongated, too. Scary, isn't it? That's why I changed the process to include 3/4" to absorb the bends. What did I do right? The mark to show which way to make the bend is a good thing. It's easy otherwise to bend it the wrong way.

This was scrap, remember.

Dave
 
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David, with a bend that long, it looks to me like you might end up with a wavy skin fit like what you are trying to avoid. On the bottom of the seat backs on the RV-7 the 3/4x3/4x1/8 6061 stiffener angles get notched identically to your illustration above to fit around the hinge. Not having a milling machine, and after a failed attempt free handing it with a scotchbrite wheel I hit upon a technique that, while very tedious, worked quite well:

Mark the area to be notched with dye-chem or sharpie and use the vixen file to just file off the ink. Use a scrap angle clamped crosswise to keep the notch square. Lather rinse and repeat a few dozen times until the notch gets to the desired depth. It took about a half hour per notch. See my build log here for photos of my setup and results.
 
Miles, I'll fill the gap with a tapered shim. Not real happy about that but it'll be necessary.

Dave
 
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It might for me, too... I've been thinking of how I'm going to do that and so far the best idea might just follow David Howe's concept of using an aluminum-filled epoxy shim that has gaps at the rivet locations for a local aluminum spacer.

I don't want anyone to think that the joggled lower longerons are optimum; they aren't. But it's how I did it. And I should say that the non-optimal aspects are relatively minor in this case. You know when you get an idea and want to follow it through? That's what happened.

The best way to do it, I think, would be to use a mill. If the angle is oriented correctly, that would leave a generous fillet radius at the change of contour. The axis of the cutter's rotation would be parallel to the width of the flange.

Dave
 
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Getting ready to install the tailwheel mount to the fuselage and encountered a bit of an issue. The tailwheel assembly, the part that bolts to the aft end of the tail spring, is loose on the tail spring. There's a couple degrees of free-play in the roll axis, even with the AN3 bolts all the way seated.

b4w5fa.jpg

Dave,

The original RV-3 tailwheel spring rods are a smaller diameter than the follow-on aircraft. So they fit loose in the standard tailwheel mounting socket. The RV4+ tailwheel springs fit tighter in the socket. I don't know which of the two diameter spring rods you have but it looks from the photo to be a later version.


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My RV3B has the original smaller diameter rod and a non-swiveling tailwheel assembly consisting of a 90 degree bend in the spring used as a pivot (common to early RVs). So I contacted flyboyaccessories (Vince/Blake Frazier) back in June and provided them measurements of the smaller diameter RV3 spring and implored them to provide a modified mounting socket for the smaller RV3 spring. Yesterday I talked with Blake on the phone and they not only complied with my request they have added it to their lineup as a stocked option. So while I had him on the phone I ordered an new full swivel Screaming Eagle tailwheel assembly and new lightweight wheel with the RV3-optioned mounting socket and steering arm with tiedown ring. I will remove my tail spring rod, cut off the original bent end and machine lathe it to the new 33/64" diameter mounting socket per the instructions included.

I would encourage you to call Blake or Vince and talk to them on the phone. They know as much as anybody about RV tailwheel installations.

I too had a Cessna 180 that had been previously converted to an Alaskan Bushwheel and looking at the original Scott casting showed that whoever did the swap used a sledge hammer to "gently" nudge the Scott off the spring. The old assembly was a total.

Jim
 
Mine is the current version.

The issue here is oversized bolt holes, not the fit of the assembly on the tail spring itself.

Dave
 
After some sweating and swearing, I made the forward ends of the F-315 seat ribs, including their 3/4" angles, fair to the spar bulkhead side plates.

Getting the 3/4" angles to joggle was a real pain. Even getting them to have a simple bend, as the SK-45 sketch shows, was a real pain. What happened was that these angles are 1/6" thick compared to the 1/8" thick angles for the lower longerons, and these would buckle. I tried various things to prevent that before it dawned on me that even SK-45 allows a flute there. A flute is another word for a pre-buckled section, so I accepted the buckle and continued.

This form block pair didn't work. It's oak. It has a slot so that the upstanding flange won't buckle. It would have taken more force than I could generate to form the 3/4" angle with these since the upstanding angle, which needed to be formed too, didn't. And when I removed it from the form blocks, that upstanding flange buckled.

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I ended up doing it pretty much the way I'd done the forward lower longerons, using shorter spacings, though. I think the spacings were 1/2" for the tension bend, 1" for the gap between bends (that might have been 1 1/4", I don't remember) and 3/4" for the compression bend. Once the tool is in place and the angle seated and clamped, I'd give the upstanding compression flange a decent whack with a round bucking bar right in the middle of the compression bend so that it would know which way to flute itself.

Sure wasted some extruded angle getting here, though.

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After that, it was time for the aft end of these angles, which need similar but milder treatment. Here I was faced with an interesting issue. When the unbent end of a 1/16" angle is considerably less than 1 7/8", if I tried to bend the angle, the part held by the vice actually shears through the thickness of the flange. It does that before there's any chance of actually bending. If I wanted to, it would have been possible to actually calculate how long the unbent part would need to be to allow for bending, but I didn't bother.

Instead, I slotted the angle and made the bend from the slot. The length of the slot was governed by the F-377 flap mounting blocks which get bolted to these angles later - always got to look ahead a bit on an RV-3B.

2lwg7o.jpg


After that, I turned towards my mis-drilled tailwheel mount base, and replaced the original AN3 bolts with AN173 bolts, which are slightly oversize. These were not fat enough to fill these holes, though, so I took some advice and tooled up to install taper pins. The appropriate pins are AN386-1-7 and these use an AN975-2 cup washer. The reamer is a Brown & Sharpe #1. Shop around because various companies sell the reamer. I found that Aircraft Spruce was a very good place to buy the hardware.

2mm6zpz.jpg


I successfully reamed the first hole and it wasn't too difficult. I'd been warned not to go too deep and the result was fine.

While reaming the second hole, though, the reamer didn't follow the original hole nicely at all, and I ruined the entire assembly.

14c5hkj.jpg


Parts on order....

Worth mentioning is that Van's Support checked the assemblies on hand and found that they are all loose there. Evidently they all got mis-drilled like mine in 2012. I ordered separate parts rather than the assembly, and will have to drill them to the tail spring myself.

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

Dave
 
Considerations for the Mixer Mount

1. The length is designed to pick up the spar bulkhead's angles that are riveted on to the aft face and extend aft to the F-304 bulkhead's side flanges.

2. The spar angles are short to allow for the insertion of the spar splice plates, above and below the angles. If the mounts extend into those openings, it'll be more difficult to get the splice plates installed.

3. The large lightening holes in the seat ribs are centered roughly 1/2" forward of the mixer bearing center.

4. If the mixer bearing is too low, the mixer's elevator pushrod fork will interfere with the floor.

5. The bearing in the mount bracket is closer to the free edge than the flange edge. If the mount bracket flange is on top, it might interfere with that splice plate opening. There's less likelihood of that if it's upside down, so that's the way I'm doing it.

6. The seat ribs spacing is such that the mount brackets are slightly too wide for the mixer itself. This will vary as the bearing is placed inboard or outboard of the bracket.

I bonded a 3/16" thick spacer between the bearing and the mixer, on each side, on the left side and 1/8" on the right side. This appears to fill the gaps. This shows one of the shims glued on. The glue with some microballoons added to control bond-line thickness provides galvanic separation between the steel and the aluminum.

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7. The beads on the seat ribs are on the outboard side of the rib. Clearing these adds to the width of the mounting bracket spacing if the brackets are attached outboard of the seat ribs. If they are on the inboard side, the bracket's flange will interfere with the mixer itself.

8. The lightening hole's bead is just slightly thinner than the thickness of the bearing flange. On my left one, I needed a .063" thick spacer between the spar bulkhead's angle and the mounting bracket, and at the aft end, I needed a .12" thick spacer between the web of the seat rib and the mounting bracket.

For the right one, I didn't use a spacer at the spar angle's flange, but used a .063" spacer at the aft end. I may need to adjust these slightly.

Here are the mixer brackets with the spacers getting glued on.

rhtq83.jpg


I looked towards the tail cone bulkheads and as expected, the slots for the lower longeron will need to be adjusted. I used a small laser on a tripod to establish a straight line.

9jj6rm.jpg


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

Dave
 
Field Trip

Recently, I got to see a remarkably well-built RV-3B under construction and was treated to what amounted to a one-day seminar in advanced techniques. The builder, David Howe, has previously built an RV-4 and then a Rocket. The Rocket is flat-out beautiful, and it looks as if the RV-3B will be at least as good. Its fuselage skins are so smooth and fair that you almost can't see the rivet lines.

I'm not going to go into specifics because those are, in many cases unique, and I think that it's up to him to show what he's developed. So this is an abbreviated report mostly describing my field trip. It amounted to a one-day seminar in advanced construction techniques.

He made a number of professional-looking tools. These include everything from custom wing supports to bucking bars to rivet sets to jigs for a single-use operation. Typically, I use wood or aluminum for my tooling, as you've seen in the photos. He'll weld up some steel and he's not afraid to go stout. Since stoutness means stiffness, and stiffness helps precision, this all adds to the quality.

One thing he's been doing is bonding his skins to the frame. The main reason he does that is to use the bond as a variable-thickness shim. He also uses shim segments of aluminum to reduce the bond-line thickness. The bond serves another purpose as well, in that it holds the skin in place while riveting. Extra work but the results are superb. We went into some detail on this and I might do something along these lines on my plane.

One thing that as an engineer, I really appreciate, is that he tests virtually every non-standard thing he does. He has his own pull-tester, for example. And he's cycle-tested the end attachment to a push-pull cable that he built.

Some of the changes he's made are strictly to enhance the utility of the airplane. One example is a built-in, easily removable toolbox that fits in one of the few unused areas in the RV-3B cabin area. Normally, you'll never know it's there, yet it's easily accessible when needed.

I've been putting in flutes to straighten the bulkheads and ribs in my plane. We all do that. He has a shrinker/stretcher pair on a stand and corrects them that way. I'll be getting a set of those this week. Incidentally, he pointed out that you don't need just a shrinker, but both, because otherwise you'll always be changing jaws from one to the other, after slightly over-doing it one way and needing to go the other way just a bit.

He's made some fittings that look a lot like those standard blue AN fittings, same blue anodizing, same general sizing, but which have custom configurations for a particular need. Looking at these on the plane, they're very easy to overlook, never guessing that they aren't standard AN fittings.

He'll have redundant fire sensors and a fire-suppression system in the plane. Race-car equipment, and readily available.

His plane abounds with cool little ideas for the RV-3B. I'm not going to steal his thunder on these here, but I might steal some of the ideas and incorporate them in my RV-3B. I do have to admit that here and there, some of them do add a bit of weight, but not all of them. Here's a view of the baggage floor rails with flanged lightening holes. He made the hole flanger tool, of course.

14bjjag.jpg


Dave
 
Joggle tooling

Dave, I'm just perusing your thread for the first time, and it's been a month since you were working on juggling your angles, so this might be too late, but I thought I'd share what I ended up with in case you found the idea useful.

http://www.our7a.com/20081118.html
 
Mike, that was roughly the idea with the oak blocks above. Not having a press, I used a decent vice, but no joy there.

One of the first things I did on the plane once I got back home was spend a couple hours with a machinist friend putting in the tapered pins in the new tailspring assembly. We did it on his Bridgeport mill. For those of you unsure of the relative precedence of this venerable tool, it's something like this:

Hand-held drills are good.

Drill presses are excellent.

Bridgeport mills are significantly superior.

I refrain from calling them "perfect" only because there are newer, more heavy-duty mills these days, with additional capability. But if you say the word "Bridgeport" to any machinist, he'll know what you're talking about.

Bridgeports are large tools and to be effective, will need a large investment in cutters and holding fixtures. You can get digital devices to assist you and probably even CNC add-ons, and I'd expect that you can rapidly drain your tool budget and outrun your own capability before you even cut a piece of metal. You can look them up if you're interested. They remain solid, reliable mills even today.

Anyway, we lined up the parts and went to work. And I got home that day with the tailspring ready to install -- until I realized that although the pins are fine, one of them is not in its proper place. New parts on order. And I might have to beef up the floor of the Attic of Shame, where all ruined parts go.

fwnh91.jpg


The next step was to glue the two F-311 aft-most bulkheads together. The plans only specify one of them but the RV-4 uses two and I was advised to follow that example. Mine are back to back. I did some tweaking to get a better fit and glued them together overnight. Now the masking tape is off and I've got a single-piece assembly to install.

I'd checked the fit of the flap weldment to the plastic F-377-1 flap mount blocks. They were very snug. I spent some quiet time with strips of crocus cloth, and now the flap blocks ride smoothly on the flap weldment.

One tool that I saw on my field trip was a shrinker/stretcher pair. It looked handy so I bought a set from Harbor Freight. It's now assembled in my shop.

dwfclh.jpg


Of course I had to grab a small piece of angle and give them a try. First thing I found was that .12 thick flanges simply wouldn't fit in. But .063 fits fine. The process leaves grooves, not all that deep but there they are. In a stressed part I'd certainly need to clean these up. I understand that more expensive stretcher/squeezer pairs have smoother jaws.

oaqi2t.jpg


And this was after I'd taken out a bit of one of the bends.

I haven't decided yet if I'll replace the seat rib angles. You'll remember that I put in a joggle in one end and a slot in the other. I think that I can use this tool to bend the angles if I choose without any joggle. Might be worth a try.... something to decide. It would let me make those angles out of 1 x 1 x 1/16 angle and narrow them down except at the flap blocks, might be worth it -- but probably not necessary.

Dave
 
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Floor Stiffener Joggles

One tool that I saw on my field trip was a shrinker/stretcher pair. It looked handy so I bought a set from Harbor Freight. It's now assembled in my shop.

dwfclh.jpg

I bought this same set, minus the stand. I likewise noted the grooves from the teeth which will need to be blended out. I bought these specifically to address the poor joggle in the forward fuselage floor stiffeners of the RV-7A. My only concern is the amount of material I may need to remove to adequately blend out the stress risers. I suppose I could always rivet a doubler on the vertical leg of the stiffener afterwards.

Let me know how they work out for you!
 
When I left off, the second tailspring assembly had been ruined. The third set of parts arrived and my friend Charley dove in. This was pretty amazing considering that he had a deadline in his company that he should have been working on. After a couple hours, I took the new tailspring assembly home. It's acceptable.

34pjbb8.jpg


Here are all three sets in order, with the most recent on the bottom. You'll probably notice that the mounting fitting on the top set has been trimmed; the stock tailspring mount doesn't fit the RV-3B aft bulkheads because the mount is from the RV-4. In the middle one, I had started cutting it down before I realized that it was mis-drilled. I have not yet touched the bottom and newest one but I should.

21etg5u.jpg


Charley also fit the brass bushing into the control stick for the mixer bolt and now that assembly feels like it's on jeweled bearings. There is zero perceptible free-play in those parts now.

One curious thing that I need to address is that my digital level has decided that the world is about 3 1/2 degrees out of kilter. Well, it's no doubt correct that the world is awry - this is an election year, after all, but none of the bubble levels agree with that assessment. I'm inclined to rely on both my own sense of things and the combined opinion of all my bubble levels. Let's just say that the judges have voted and the digital level is off the project.

Looks like I'll be using my iPhone for the near term.

While I was waiting for the tailspring to get finished, I went ahead and added a few holes to the welded rudder pedals. I think that this saved something like 1/2 or 3/4 of an ounce, definitely worth going after.

6hm9lh.jpg


I've been playing with using the shrinker/stretcher to put a joggle into those seat angles. There is no question now that it can be done. The only question is whether I am willing to sand off about .002 to about .0025 inches on each side of the flange (total .004 or .005 inches) that I shrink or stretch (or both) to clean up the marks from the tools.

The photos can also be seen here, here, and here.

Dave
 
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The new seat angles are fabricated. They went relatively smoothly. I had to work on the flanges to remove most of the roughness from the shrinker/stretcher, which does leave a mark in 6061-T6.

In both pictures, the top one is the new one and the bottom one is what I'm replacing.

11v47rc.jpg


1zqd1u0.jpg


It leaves less of an impression in 2024-T3. I used it on the flanges of the F-306 bulkhead to flatten it up while I was fitting the baggage floor rails.

2ry0px3.jpg


There were fewer marks in the 2024 bulkhead flanges but then of course I was using it more gently. I've decided: the shrinker/stretcher is a good tool and worth having.

By the way, when I started fitting the baggage rails to the F-306 bulkhead, the bulkhead was about an inch aft of it's proper location, clamped to the aft face of that aluminum rectangular tube on the jig (the one that it is now clamped to the front face of). It fit well there, except for the baggage floor rails, which weren't long enough. I moved the bulkhead forward so that the rails would fit, but then the bulkhead was inside the longerons. I hadn't glued this bulkhead yet since I had a feeling it might need tweaking. I unclecoed one side from the other side and spread them apart slightly and clamped them so that they fit to the longerons. Then I reclamped them where they joined in the middle.

I'll have to add splice pieces but it's not a big deal: about .10 inches at the bottom and about 1/2" at the top, more or less.

I'm glad I thought about doing that.

The tailspring mount is clecoed nicely in between my F-310 and F-311 bulkheads where it belongs. Both of these bulkheads are now glued together - you'll remember that I doubled up both of these.


fwlpft.jpg


The F-310 bulkhead is riveted, too, to the stabilizer mount bars.

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

Dave
 
The side-clamps holding the bulkheads to the longerons finally got themselves replaced by clecos. It was fun drilling holes for a change after all that measuring and tweaking and flange straightening.

2i7bomf.jpg


One of the things that was necessary to do was see if all four splice plates would go in after the fuselage was all riveted together. As received from Van's, they are bare steel, covered in oil. I cleaned them up and lightly primed them.

There are two different styles. Two of the splice plates have square edges and the other two have one rounded edge. It was pretty clear that the rounded edges fit against the lower flanges on the spar bulkhead, and that the square edges fit on the top of the spar bulkhead. The splice plates are marked "fwd" and "aft" and there were one of each style for both locations. I was glad to see that since it meant that I didn't have to worry about which went where.

The aft splice plates went in to their positions nicely, even with the mixer in place, although I removed it for the photograph.

ilk8yc.jpg


The forward top one went in easily. Unfortunately there's no way that the forward bottom one will fit after the fuselage is riveted. I'll have to have it in place during that operation. Since there are some serious rivets going in close to that splice plate, this might get tricky at that time.

ajx8k3.jpg


Please remember that I changed my F-312 firewall reinforcement pieces to be more like the RV-4 and pick up both top and bottom splice plates. The stock F-312 pieces provide ample room to fit that splice plate without much drama. I tried to allow for clearance for this but it's just not going to happen.

The photos are alternatively hosted here, here and here.

Dave
 
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Here is a photo of the brackets that attach my firewall to spar bulkhead replacements of Van's F-312 ribs. The brackets are attached with a couple of AN3 bolts so that if it's ever necessary, I can remove these to remove the spar splice plates.

213nmoj.jpg


There might be some photos earlier that showed these with holes for rivets; I decided to follow the sensible RV-4 scheme and make them removable.

The bolts are hardware-store bolts and will be replaced when the wings are permanently on.

A short editorial:
If you haven't already sent in your donation to support VAF, please do it now. I rely on VAF for a great deal of my support, and beyond that, to host this log of my construction. I wouldn't be building this airplane were it not for VAF. You can do it here. Thanks!

The photo can also be seen at an alternate hosting site at Imagebam.

Dave
 
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I made a pair of bottom firewall gussets, similar to the F-855PP gussets on the RV-8. These are made of .063 2024-T3. The photo shows the right one clecoed on.

qx5efd.jpg


Here's the shape I used. It fit both sides with just a little extra; it was a good place to start. I trimmed both slightly after drilling them. Note that they both needed a slight bend.

xlc7e9.jpg


There's also now a gusset for the top of the firewall frame, too. On the RV-8 that's the F-845PP. I made something that would fit. Here's my RV-3B version:

20gd3li.jpg


The numbers indicate the dimensions for the adjacent edge in inches. These also were .063 2024-T3 aluminum, and like the others, required a bit of final trimming and bending to fit.

29c849e.jpg


When I decided to make these, I was following the advice of Randy Lervold and in the footsteps of a number of subsequent builders. Interestingly, though, neither the RV-4 or the Rocket seem to have any similar gussets.

I redid the firewall to spar bulkhead ribs, that on my plane replace the F-312 ribs. I'd made a mistake in a rivet pattern and it was easier to replace them than fix them. This current version also has a mistake - the flange to the bottom skin (on top in the photo) should be pointed outboard rather than inboard. The rudder pedals mount on that flange. I'll add some angle for that purpose and that's why I left some of the rivet holes empty for now.

You can see the clecos in the firewall attachment holes.

r060w7.jpg


Here is what the forward fittings look like.

2v7xzxt.jpg


The photos are independently hosted here, here, here, here, and here. And the last one here.

Dave
 
The bottom forward longerons are 1 x 1 x 1/8, and the factory shipped two pieces for that. They were labeled F-450 and I didn't think anything about them. I managed to ruin them both, and replaced them from stock. It turns out that unlike the stock angles, the F-450 are special. They've been opened up to fit the bottom skin. On my plane that is only necessary at the aft end, and it should taper to the standard 90 degrees at the forward end. It didn't appear as if the F-450 did taper, it appears, looking at the scrap, as if it had been opened up full length.

I replaced the original ones that were 90 degrees with a pair of new F-450s. They fit just fine. Keep an eye out for them in your kit, if you're building one of these.

In the view of the lower gussets and that lower forward diagonal longeron in the previous posting, you can see that the forward end of that diagonal longeron is outside the firewall fitting. The plans specify that it be inside, but in order to fair to the skin, it either needs to be outside or I'd need a joggle or a shim. Since the lower longeron is the same thickness - and in fact the fitting was positioned for that - outside it is.

The spacing of the flap weldment and its bearing blocks, F-377, is such that the fuselage is about 0.58" wider than needed, so I added a pair of 1/4" plastic spacers:

30lmnp5.jpg


wi8sw0.jpg


These have the added benefit of slightly reducing the friction on the weldment, since they reduce the overlap.

With these in place I jiggled the position of the flap weldment assembly to minimize the interference with the longeron (some trimming still required):

24bus1j.jpg


Then I drilled the pilot holes for the bearing blocks to the seat rib angle and clecoed them:

34oq5b4.jpg


Using fairing strips of aluminum, I was able to locate the corner aft bottom pieces of the seat bulkhead. These are sketched in on Drawing 19 and Sketch 43 and have an RV-4 part number, F-407C, which doesn't show up on the RV-3 plans.

14v69hs.jpg


Then these got drilled and clecoed, taking care to avoid the rear spar carry-through.

10dihjc.jpg


Looking around, it appeared to be time to yank the spar bulkhead out for some of the small work that's been taking my time.

2dqndpz.jpg


The fuselage sure seems sparse without that, doesn't it?

wiubg7.jpg


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

Dave
 
More on Fitting the Flap Weldment

Just wanted to elaborate on fitting the flap weldment. If its too far aft, the forks will interfere with the lower longerons. If it's too far forward, the arms to the forks will rub on inside flanges of the seat bulkhead.

If it's lined up perfectly true in yaw, it's entirely likely that one fork will rub and the other will have satisfactory clearance.

Even when the clearance to the longeron looks ideal, probably the bolt heads for the rod-end bearing inside the forks will interfere with the longerons.

And you might need to trim the seat bulkhead's inside flanges to allow for the assembly's cross-bar.

With all that, the bearing block's mounting bolts still need to have the right positioning for reasonable edge distance on the seat rib's angle - that's why I added those 1/4" plastic shims. This would be a reasonable place to trim down a 1x1x1/16 angle like I did on the upper longerons, so that there's a wider pad for these bolts.

Dave
 
That is one nice fuselage jig. Is that one of the old "Frey" jigs? I built my RV-6 on the plans-specified wood jig and a Frey jig was but a pipe dream...
 
Yes, it is. My use of it on my RV-3B probably starts on post #235. I also put a thread on the jig itself here.

This is an RV-4 jig that I adapted for this purpose. You'll note a few non-red and non-yellow parts which are parts I added. And many of teh yellow cross-members needed to be relocated.

If I were going to ask Mr. Fry for a change, though, it would be to make the jig about 6" higher off the ground. I'm not a tall person and the jig still seems unnecessarily low. I can easily look over the bottom of the fuselage but it's awkward to work near the upper longeron. I suppose Van's jig instructions might have the same issue, since they are about the same height. But to put this in perspective, I don't recollect any of the other builders commenting about this, so you might find it perfectly positioned.

Dave
 
Systems....

I've been thinking about where things are going to go, and this is my current iteration. All this is tentative, of course; in most cases I don't even have the stuff yet. Please remember that this is for an RV-3, and it has a smaller cockpit than the other RVs.

Here's the instrument panel equipment:

Clock
MGL V6 Com
Airspeed
EFIS
iPad
LH Pmag switch (I'm reviewing the various wiring approaches from VAF)
RH Pmag switch
Master/alternator switch
USB port (or on side panel?)

The engine controls will be in the left side panel, and the right side panel will have some miscellaneous stuff. There won't be any switches on the stick:

Wingtip light switch
Landing light switch
Autopilot servo power switch (both servos on 1 switch)
Headset socket
Microphone socket
Starter button
Oxygen regulator
12 V outlet
Fuel pump switch
USB Port (or on panel?)
Push to talk button (throttle)
LH Pmag circuit breaker
RH Pmag circuit breaker
Autopilot engage/disengage button
Throttle
Prop
Mixture
Carb heat
Cabin heat
Cowl flap (possible)

The space between the rudder pedals and those ribs that go from the firewall to the spar bulkhead is the forward equipment bay, and will mostly have fuel system stuff.

Gascolator
Fuel pump
Valve
Fuel flow sensor

I expect to build a shelf forward of the instrument panel for electronics. It'll be called the forward equipment bay and have these things:

Battery in box with vent
EFIS backup battery
Battery solenoid
Starter solenoid
EMS
Voltage regulator
Oxygen tank with gauge, visible under panel
USB port for ping Buddy (Different one than for the panel or side panel)
Fuse box
Skyview network hub
Transponder
Sensor and system 5 V power bus

Other hardware will be scattered around the airframe, in the tailcone unless noted:

Com antenna
GPS (Behind roll bar)
ping Buddy (canopy frame or top of seat bulkhead)
Pitch servo
Roll servo (right wing)
Transponder antenna
Pitot tube (left wing)
Static ports
OAT sensor
ADAHRS
Stall warner switch (LH wing)
Wingtip strobes/nav lights
Landing light

I'm attempting to keep the firewall reasonably free of equipment, and so far I only plan to attach some engine sensors there. The engine on the RV-3 is very close to the firewall.

I have another list of the things that pass through the spar bulkhead. So far it's manageable but recently it's gotten busier.

You might wonder what this piece of aluminum is doing in the winter garden and who could blame you? This is the piece of tube that's going to become the forward elevator pushrod, and I'd just sprayed plenty of primer into it. Primer was dripping out the far end. Of course I could have fabricated a dedicated support tool with cushioned clamps to hold it while it drained, but instead I just stuck it here. Worked great, cost nothing and took no time, thus fully meeting my goals.

How often do you get all three: as one of my project managers liked to put it, "good, fast, cheap - pick any two." And here's all three.

2j1lj5e.jpg


The alternate link is
http://www.imagebam.com/image/f7dab9528155839

I've completed other work too, but this is all I've got a photo of.

Dave
 
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Carl, thanks for the comment. My other airplane won't have a Lemo socket, so I don't expect to be using that sort of headset or helmet. While a single socket does sound desirable instead of the two that I'm planning, one small goal is to attempt a certain amount of commonality with the other airplane, a non-RV.

I have no plans to allow for future growth or additional capability. This airplane is a single-seater, so I don't need to allow for passengers bringing their own headsets.

Dave
 
I'd thought of using a top-mounted rudder pedal system like this:

may2011.jpg


in this thread on my RV-3B. When I investigated it, it appeared to be slightly heavier. And I realized that my firewall recess, which John doesn't have, would be in the way.

n1axwh.jpg


I got to sit in Scott Walker's local RV-3 and made a point of trying out his stock rudder pedals. I thought they were fine.

There are some gaming rudder pedals which appealed, like these F-16 pedal set. Of course they'd be off their game base if I'd used them.

6zlt1e.jpg


As for housekeeping, On the RV-3B the forward turtledeck, ahead of the panel, removes relatively easily. That's one of the factors that went into the decision to have an upper equipment bay. I won't be building a center avionics console like some RV-3s have, like this one on Paul and Louise's Tsam

IMG_0419.JPG


Bottom line is that I decided to go stock.

Dave
 
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