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David Paule 02-10-2014 07:45 PM

More Tank Stiffeners
I made a second set, this time for the right tank. I've also deburred the right-hand tank ribs and baffle and made those little flapper valves that are shown on drawing 12A for the inverted system.

While my carbureted airplane won't have an inverted system, some RV owners have reported that the flapper valve helps when low on fuel in turbulence, so I added them. Also, it should be useful during slips. I'm putting them into both tanks.

Both tank skins are now drilled for the caps and the drains, too.


David Paule 02-12-2014 11:32 AM

Flapper Valve
Thought that perhaps someone might like to see the flapper valve. This in the one for the right tank.

The plans says to install it for the inverted fuel system, which I won't be installing. But this should be helpful in slips and turbulence.

Here's what the plans shows:


But the plans didn't include the tooling hole or the stiffening features embedded into the rib. That led me to making the hinge shape as I did. If I'd made the flap taller and moved the hinge higher, things would have been a lot easier, but I didn't think of that when I was doing it.

I also wanted to keep a bit clear of the bottom edge, and to avoid Pro-Sealing the valve, I'll tape it open when I seal the ribs to the skin. The valve is rounded simply because square corners contributed nothing except an attraction to the planer Earth. This is ever-so slightly lighter.

The final detail was how on earth could I prevent the pin from coming out? Turns out to be a no-brainer: with the bend end aft, the baffle will retain it. Of course the forward end needed to be long enough so it doesn't fall out then.

Worth mentioning is a tiny bit of philosophy.... One reason I'm making small weight-savings changes like this is just to keep in the habit of doing it. Perhaps if I do it often enough I'll have a light RV-3B.


David Paule 03-02-2014 07:25 PM

Oops And Go
Good news and some bad this time. The bad news first.

I scrapped the tanks just before sealing them. I made a mistake, the Mother Ship said it would be a relatively easy fix, I didn't care for the way the result turned out and decided to make new ones. Parts on order.


Moving on.

Figured that this would be a good time to rivet up the outboard leading edge, but before I did that, I needed to work out the installation of the landing light and the stall warning vane in the left wing. You're probably thinking, "What do you mean, work it out? Get the Duckworks landing light mount like the rest of us, and install the Van's stall warning vane."

Well, this is an RV-3B and it's not entirely that simple. The Duckworks lens is a nice fit - thanks, Duckworks! - but the mounting plate is not. I figured out an alternative mounting approach. And the stall warning vane assembly is pretty nice. It even includes some pre-punched parts! But it's intended for the RV-7, -8 or -9 so some of the parts won't fit. And it needs an inspection hatch.

I saw a very nice RV-8A at the 2013 LOE fly-in that had the vane just inboard of the landing light lens. The pilot said it worked well and access was through the lens. It looked as if I could adapt that to this installation. I had to make a couple other tweaks, though, for ease of future access.

Here's the stall warning assembly and mount combined with the landing light mount support. Please note that this assembly was made without the fasteners getting tightened. I just assembled it to check the fitting up of the thing. I didn't tighten the fasteners because the tools were outside and it was cold today. I promise I will before it's permanent.

And another view,

The landing light mount itself is partly supported by this piece, but it's another assembly, this one composite. I was glad for that since I LIKE working with composites. Here's a bit of fiberglass I made for the mount.

Pretty easy.

Back to the outboard leading edge, I'm gluing the carpet strips to the cradle pieces now.


David Paule 04-11-2014 09:13 AM

Stall Warner Installation
After needing to be out of town for a few weeks and then another short trip, I'm slowly getting back to it.

Right now I'm trying to find the place to cut the slot for the stall warning vane. This isn't part of the RV-3B kit, but I bought one from Van's. It's going into the outboard-most bay on the left leading edge, and with the leading edge now riveted but not attached to the spar, this is time to cut the slot.

I made a short straight strip of .032 aluminum to simulate a vane, so that I could move it in and out until it touches the leading edge. I still need to see if the bend in the vane (not shown) is inside the wing, right at the leading edge or ahead of the leading edge.

The keen observer might recognize that I made this one a mirror image of the way the stall warning kit is designed. This will permit access from the tip or from the as-yet-uncut landing light lens hole.

RV-3B: Not like the other kits.


ppilotmike 04-11-2014 03:47 PM

Nice Work!
I still want to see your landing light install. I haven't done mine yet. Still in head-scratchin' mode. ;)

David Paule 04-15-2014 07:56 PM

Landing Light Mount
Here's the landing light mount. It's made of some unidirectional carbon fiber kite spars that I bought from, which has a local store. I had to make the fiberglass tabs myself.

The blue tape is to identify the outboard end as the mount isn't symmetric.

The mount with the light installed is easily removable through one of the lightening holes in the nose rib at the tip. Or the light itself could be removed through the lens in the leading edge if I didn't feel like removing the wingtip.

The mount itself weighs 33 grams. It replaces a Duckworks landing light mount which weighs 142 grams as-is, or 137 grams with the mounting cut-out cut.

The Duckworks mount didn't actually fit all that well and replacing it saved me 104 grams or 3 2/3 ounces. Plus it was cheaper. Of course now I've got a couple Duckworks mounts for sale.


ppilotmike 04-16-2014 09:16 AM

Kite Spars

So how will you mount the kite spar ends to the rib webs inside?

David Paule 04-16-2014 09:39 AM

The ends of the carbon rods will fit in bushings in the large holes in the outboard rib and in this rib.

I've got to do some cutting in there for the landing light lens and the stall warner vane before I mount the light.

Since carbon and aluminum can corrode, the bushings isolate the two.


ppilotmike 04-16-2014 12:30 PM

Will the rods free-float in these bushings then? What keeps them from sliding around?

David Paule 04-16-2014 04:22 PM

There will be retainers that I haven't added yet.


David Paule 05-14-2014 06:50 PM

The stall warning vane got its slot made and is now mounted, and the landing light hole has been made. The top lens mounting strip is riveted and although it's not shown in the photo, the bottom one is too.

That's not much to show for a month but this is my busy season.

I'm now fitting the lens.


David Paule 05-18-2014 08:00 PM

First Wires!
Small thing, all in all, but the first wires are installed.


wirejock 05-18-2014 08:43 PM

Looks like you're running a dedicated ground to the stall switch.

David-aviator 05-19-2014 06:14 AM

Great work David.

David Paule 05-23-2014 06:56 PM

Landing Light, Lens and Stall Warning, Installed
First I had to change the mounting assembly around so that the Microsun landing light mounts from the back rather than the front - the big rib lightening hole on the left, after removing the wingtip, makes better access than the landing light lens.

I used a plastic hose clamp, visible at the upper left, for lateral restraint on the mount. There's one on the exterior, too.

I tested the hardware: the stall warning switch works and so does the Microsun. That light is bright! And it's got a nice wide angle, perfect for my daytime VFR collision avoidance.

Be seen.


David Paule 05-27-2014 12:25 PM

Tie Down Fitting and Hole
One thing that had kind of bothered me was that according to the plans, there was a bit of a gap between the bottom skin and the tie down fitting. I decided to fix that.

Since I had a set of Cleaveland tie down fittings on hand, already threaded, this was a simple matter of matching the holes and doing a bit of trimming.

The drill press quickly match-drilled the new part.

I used the band saw and cut the shape. I laid out the taper and cut that too. The 6 1/2 tpi wood blade cuts thick aluminum well, and the Vixen file smoothed it. Quick and easy, just a few minutes of work.

The new one is half an ounce lighter, even though it's bigger. Worth doing.

What I didn't do is use these new tie down fittings to move the tiedown points outboard. I thought of that because the RV-3B is so small and close to the ground that it's hard to get a decent angle on the tie-down ropes -- they will typically be splayed out at a considerable angle. Thought about it, ran some numbers (my old profession, aerospace stress analyst) and it looked okay but marginal. Finally decided not do do it. One reason was that adding new fittings wouldn't eliminate the existing ones. The new ones would be added weight and the utility of them would be relatively minor. All in all, not a positive change, assuming that I don't get caught out in a 70 mph wind while tied down to widely-spaced anchors on a trip some day.

On the RV-3B, the skins aren't pre-punched, so I needed to locate the hole for the tie-down. I used a scrap of .032 and a 12" long #40 drill bit to back drill it to the spar flange.

Then I shortened a transfer punch which had a nice snug fit in the threads. It only fit in the threads, not the long hole.

The small part fit the threaded hole.

And pushed farther in, ready to go.

I used a thinner transfer punch to push it. This was the only rod I had handy which fit. It didn't need to be a transfer punch and actually would have been better if it wasn't.

The combination of the pieces and the tit on the longer transfer punch and the fact that I wasn't backing up the match hole jig meant that the center punch in the jig was relatively small. I used a marker to outline the tie down fitting on the jig so I'd know where to look.

After drilling a pilot hole at the location, I clecoed the match hole jig to the lower side of the leading edge and double checked a couple dimensions to be sure.

I pilot-drilled the skin, removed the match hole jig and drilled it out to 3/8". The final hole isn't perfectly centered but it's within about 1/32" and that's good enough, especially since I can't move it anyway.


David Paule 05-28-2014 08:12 AM

Here's what I'm doing for plans.

The plans come in sets. Order a kit and you get the plans for just that kit. When I made my first order, I requested that I get all the plans at once so that I could look around and check things - highly recommended for RV-3B builders. Even with all the plans here, they aren't anything like the double-digit RV plans. These are large sheets of paper, with something just a wee bit better than blueprints on them.

The original plans are over 24 inches tall and long. That was a bit too large for my work tables, so I took them down to Rocky Mountain Blueprint Co. They made me a set that was 18 inches tall. These fit my work benches much better. I've still got the originals for when I need "full size" patterns. It sometimes happens.

They also scanned the plans in and made a single PDF file of them. It's 9.5 mb. On my Mac, they show up quite well. The Mac lives about a dozen feet from the shop so I generally don't need to use the computer to look at the plans.

I also loaded them on my iPad. The iPad (mine is generation 1) is a bit poor at this, though. I know from the Mac that the files have ample detail, but the three apps I've used just don't show it. I've used Goodreader (worthless), iBooks (so-so) and the Kindle app. Kindle is a hair better than iBooks for the plans, and that's still marginal.

If anyone has a better app for viewing these plans, please let me know.

And since my iPad is a 1st generation one, it's very slow loading these things. I mean glacially slow. And old style glacier speed at that, not the new speeded-up glaciers of our climate change era. 15 minutes to load the plans isn't unusual.

Still, if I'm away form the shop and need a look at them, well there they are. And the first page I need is a bit quicker.

Another thing that I did is really useful. I made a parts list in a spreadsheet, that lists the part number, name, what its material is, the as-received source material, quantity, and best of all, every drawing page that refers to it. I printed this out and keep a copy in the shop and another at the hangar, where I store the parts that I haven't used yet, like the fuselage and finish kits. The preview plans are there too.

Since the RV-3B is sort of a unique RV kit, I have a copy of the preview plans for the RV-4 and RV-8 in the shop. When starting something new, those are the places to check, to make sure that the RV-3B design isn't too obsolete. Sometimes it is. In any case, it's a quick and easy sanity check before cutting or drilling something.

Which reminds me that the Mac, just outside the shop, is handy for one important thing. I also check VAF and sometimes vendors for information relating to what I'm doing. You never know. Sometimes the oddest things pop up, like needing to leave the connector cap off the autopilot servo in the right wing. That was the latest useful bit of data I got. Or maybe it was that Lexel is a decent sealant that's compatible with acrylic. One of those. Anyway, thanks, Doug!

And with all these resources at hand, I still sometimes miss things.


David Paule 06-17-2014 08:33 PM

I've been working away in spite of nearly continuous interruptions.

The fuel pick-up lines that Van's sells almost fit the RV-3B. I had a pair and found that they were just under 90 degrees as received. I closed them up a bit, not too much, and now they fit fine.

It looks like the tool overlaps the hardware on the line but that's just the photo. The line fits fine but there's not a lot of extra clearance.

You might remember that I'm making new tanks. I'm making the various parts that fit the ribs now.

And the slow progress will continue for at least another month.


David Paule 07-05-2014 07:47 PM

2nd Tank Work
Some of the unrelated personal things that took a great deal of time and energy have ended and I can now work a bit more on the plane. But some of them might resume and can't be forecast. I'm working while I can.

The small stuff like the hatches and the rings and the rest of the small parts are all done for these tanks. I've fluted and marked all the ribs, drilled them to the baffle and aligned the frame parts on the wing in the jig.

Here's the right wing.

And on the left wing, the skin is on for the initial fitting. Before I got this far, all the tank ribs needed tweaking because they were just a skosh too long to line up with the outboard leading edge. Looking across the leading edge, it now lines up nicely.

Thanks, David Howe, for teaching me about these wooden fittings.


rockwoodrv9 07-05-2014 08:17 PM

It is really looking nice David. Keep plugging away!

David Paule 07-24-2014 07:59 AM

With the left tank now all drilled (but not deburred, I'm saving that until both tanks are ready), I'm working on the right tank. As of last night the top surface is drilled and clecoed to the ribs and the bottom surface is marked but not drilled.

It's strapped down to hold it in shape for the drilling. But no clecoes in the photo - l must have taken the photo before drilling the top. Well, just use your imagination. They're in there.

Also you can see those handy square .063 tabs that I'm using to hold the skins fair. The tabs are an inch square, with a #40 hole drilled 1/4" from the edge in the middle of a side. All edges rounded. Someone should make these and sell them....


David Paule 07-30-2014 07:42 PM

Both Tanks Drilled
Both tanks are drilled, skin to baffle and ribs, and skin to the spar flange. The spar flange holes are pilot holes for now.

Gettin' closer.... Closer to deburring and dimpling and countersinking, anyway. I left all that to do at once and shortly there won't be any excuse and I'll have to do it.


David Paule 08-27-2014 04:51 PM

Doing the Gooey
Yes, I ran out of excuses and started assembling the tanks. Here are the inboard and outboard ribs:

More recently all the parts are riveted on and the -6 rivets too. Those were easy. And the blue tape's gone.

Then I put the stiffeners on using tank sealant. When cured, I started riveting them. This was taken before I got the tape off the first side.

I'm now riveting up the second tank's stiffeners. My work is outpacing the photos.


David Paule 09-05-2014 03:35 PM

Still Gooey
The tank stiffeners are riveted on, as well as the filler cap rings and the drains. I've been using the more syrupy type A tank sealant to dot the rivet heads and add additional sealing around the perimeter.

So far, with the end rib assemblies and the stiffeners, I've used 132 grams of the regular type B sealant and 81 grams of the type A sealant. I expect that another 20 or 25 grams of the type A will finish sealing the end ribs. Sealing around the fancy sealed nutplates takes a bit.

I started using hardware store plastic syringes with the ends cut off to open up the applicator end, and found that it wasn't necessary. I get better results and use less type A sealant with the normal narrow stock end.


David Paule 09-11-2014 06:58 PM

With a whole afternoon available, I used the tank sealant to glue five of the six ribs to the skin for one of the tanks. I didn't glue the inboard rib yet because I need to rivet the skin/ribs before I slip in the vent tube, and the inboard rib needs to be off to do that.

Five ribs and a bit under 80 grams of sealant. Previously, I'd abraded the parts, cleaned 'em and taped off the parts I didn't want to get sealant all over. Today I recleaned them, got them all goopy with tank sealant and then clecoed the ribs to the skin.The only really messy part was putting those #4 nuts on the clecos to get more clamping pressure. The clecos push some sealant through the hole and that gets on the small nut. And of course that's working blind, by touch.

Fun day.

I think I used something like seven or eight pairs of gloves. if it hadn't been for those silly little #4 nuts it would have been one or two pairs.

The photo was taken after I'd pulled the tape out. That's another fun job, reaching in and pulling out tape that's got tank sealant on it. After I took the photo, I clecoed in the baffle just to ensure that the tank would cure while it was held in the right position. Without the baffle it didn't have any shear stiffness.


David Paule 09-25-2014 10:02 AM

Quick update on the tanks.

I've got the left tank riveted but haven't yet dotted the rivet heads with tank sealant. Also the inboard rib is still out pending the vent line installation.

The right tank is assembled and glued and clecoed, all but the inboard rib, and is curing.

I borrowed a #8 nutplate tool to drill the nutplate attachment holes on the spar flanges but haven't actually drilled the #40 holes yet. The screw holes have been drilled but not countersunk.


rightrudder 09-25-2014 12:11 PM

Lookin' good, Dave! I went QB on the wings, so I'm missing this rite of passage. :o I'm sure it will feel great to apply that last dab of sealant and finish them up.

dave4754 09-28-2014 08:39 AM

Excellent work
I have done the left tank completely and I wouldn't worry about your use of gloves, as I bought a box and have almost used it all. About one half of those went into tank construction.

I offer this as a question though, it would be a concern to me that any tape might have been left behind to cause a clog in your fuel system. I bet you already know this though. :rolleyes:

Nice work!

David Paule 09-28-2014 12:29 PM

You're right - we've got to be careful to get that tape off while the sealant is still wet. I didn't do that with the first set of stiffeners and spent some happy hours listening to the radio as I worked the tape free of the cured sealant.

Got it all and then went back with the thinner type A sealant and resealed those sealant edges.

Learned that lesson!

To date, the tanks have used 333 grams of the usual type B thicker sealant and 112 grams of the thinner type A. But I've got a way to go. And "used," in this context, included sealant that's still in the mixing containers and syringes.

I haven't even bothered with the SEM gun I bought.

This shows the rivet dotting that I did yesterday on the top ribs of the left tank using the type A sealant in a syringe. I didn't do the bottom rivets because I didn't want the sealant to run. It's like honey and it might not, but I didn't want to risk it.

I decided to do the top first so that I could get the vent tube in place before proceeding.

You'll note that one rib seems to be reversed compared to the other. The right rib in the photo is the outboard rib. The plans say to have the flange outboard, which would be consistent with the other rib, but that doing it this way is optional for more fuel. It's about half a gallon and hey, I LIKE having more fuel. Beats the alternative.


David Paule 10-13-2014 07:12 PM

Well, a friend came over and helped me rivet the tank skin to ribs on the right hand tank. We'd already done the left tank, and I'd installed the inboard rib on that tank.


ijustwannafly 10-15-2014 09:30 PM

So dave, when you do a plans built kit like this. I know you have to drill all the skins with a fan spacer and such is anything drilled for you? Or do you literally get a box of stamped parts and thats it

David Paule 10-16-2014 09:03 AM

There are probably a dozen parts that come with holes, and that includes the main wing spars, which are drilled and riveted (except for the holes on the spar flange that attach to the skin, those aren't drilled). None of the skins, ribs, bulkheads, etc., come with holes.

Take a peek up to post #99 for a look at the right tank still undrilled. The first photo shows the undrilled ribs and the next, the skin. Here's how I drilled those holes.

1. I carefully located the ribs in the jib and secured them in place. I used a bit of brass tube as a bushing to back-drill through the spar to get the aft flange holes, removed the ribs, and opened them up to #30. Post #51 shows that. Then I clecoed them to the spar and put some threaded rod through their leading edge.

2. Place the skin in position and do any trimming to get the aft top edge in perfect alignment. Use the Howe fittings to strap the skin into place, see post #75. This is kind of an iterative process.

3. When I was happy with the fit, I removed the skin and drilled the top skin for the the spar flange holes using a handy jig I'd made from some scrap 4130. The jig rides on the edge and locates a position 1/4" in from the edge; I still need to mark the spanwise locations. Then I removed the ribs from the wing jig.

4. I located all the holes on the rib flanges top and bottom and drilled just the top rib flange's holes.

5. Replaced the ribs and skin with the Howe fittings and straps and drilled and clecoed the skin to spar flange holes, securing the skin into position.

6. Starting at the aft-most holes, I back-drilled and clecoed every top rib flange hole in the skin. At the leading edge, I had to hold the skin to the ribs, but that wasn't hard, just a bit awkward.

7. With every top hole clecoed, I made a table of measurements locating every single hole in the bottom except the spar flange holes. I measured everything as many ways as I could, paying special attention to external references so that I could transfer the hole positions to the skin.

8. Strap down the skin again with the Howe fittings, and when satisfied (it takes me a couple tries to get it right) measure and mark the hole locations on the bottom of the tank skin.

9. I didn't bother using a center punch. The vinyl holds the drill position well enough. Starting at the most forward, blindly drill through the rib and skin. I could see the mark on the ribs so I knew it was okay. Placing a cleco in each hole as I went along, I drilled about 1/3 to 1/2 of the way to the aft edge. Then I stopped.

10. I removed the bottom skin clecos and Howe fittings and straps and opened up the bottom and checked the holes. This let me assess how I was doing. I didn't do this on both tanks because on one of them I could see the marks on the ribs better through the holes and knew that everything was okay, so I just kept going.

11. When the clecos were in every hole, I drilled through the spar flange on the bottom.

At this point all the ribs and the spar and skin are all drilled. There's been a cleco in every pair of holes.

This was probably more information than you wanted, eh?

Still, this is the major reason I chose the RV-3B kit, so that I'd have a number of fun problems to solve. In that regard, it hasn't been a disappointment. But I can't say that it's going together quickly or that I haven't made plenty of mistakes - my scrap pile is big. Still, all in all, I'm making progress.

RV-3B -- Some thinking required

HFS 10-16-2014 11:16 AM

When The Real Fun Starts!
Wait until trying to jig the fuselage if you want some real fun!


Ironflight 10-16-2014 06:07 PM


Originally Posted by HFS (Post 925650)
Wait until trying to jig the fuselage if you want some real fun!


Second that! Of course, you can take the easy approach - build the jig precisely, mount the bulkhead on the jig precisely - then close th ebuild manual, put away the plans, and build an airplane around the bulkheads. Many of the measurements don't quite add up anyway, so don't sweat them - just make it all work!

Oh - no pre-drilled holes in anything.

David Paule 10-17-2014 08:53 AM

You're Getting Ahead Of Me!
I'm looking forward to the fuselage, I've got to admit. The engine is standing by and so is the finish kit. I even picked up something for the cockpit: an ARP carburetor ice detector, like the one in my Cessna 180 that works so well.

But for actually building it, that's in the future. All I have right now is anticipation and, well, this:

It's a Frye steel jig, folded up so I could haul it in my pickup (yeah, these jigs fold - cool!) and it's not set up for an RV-3B. I don't have instructions for it - but I do have a bundle of small parts that comes with it. If anyone has instructions, give me an email or PM please. As it is, I'm expecting some "real fun" just getting it to work. But since it's already built a couple of airplanes, this one should be easy for it.



David Paule 10-22-2014 11:31 AM

Spar Flange Nutplates
Right now, the top skins are off the wing so that I could install the spar flange nutplates and the autopilot roll servo and things like that. Before, I hadn't countersunk the tank nutplate holes (they had been pilot-drilled and on the tank skins, dimpled), and had to at least countersink these to get the tanks back on when they're complete.

The countersinking of these holes wasn't well-documented in the RV-3B manual. I used the tip given in "27 Years of the RVator," to open them up to .365 to .375 inches outside diameter. It took some fiddling to get there since the one-flute countersink bit was .377 inches diameter. Interestingly, I noticed in the RV-14 wing section on Van's revisions page, that for the RV-14, the max countersink outside diameter is .370 inches. No minimum is listed.


David Paule 11-01-2014 07:15 PM

Playing With the Gooey Stuff - Tips
After riveting up the tank skins and ribs, the edges of the tank sealant looked like this:

Then I saw this:

And went back into the tanks with some of that type A sealant in a plastic syringe and a tongue depressor that I rounded off to 1/4 inch radius. In the how-to, a mill is 1/1,000 inch, so 250 mills is 1/4 inch. I've got a little more to do but now they're looking like this:

Have to admit, this part was fun.


ijustwannafly 11-01-2014 07:56 PM

Looking good Dave! now i know who to call for help my with tanks!

David Paule 12-14-2014 07:42 PM

The outboard leading edges are riveted on to the spars.

I didn't forget the rivets through the rib flanges to the spar web.

If you look closely you can see at least one of the alignment strings through the holes in the front and rear spar that let me check for twist. And the landing light lens and stall warning vane are visible too, all on the left wing, the one in the background.


rockwoodrv9 12-14-2014 08:27 PM

Looking good Dave.

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