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Old 08-20-2017, 01:59 PM
Rv3Dave Rv3Dave is offline
Join Date: Jul 2016
Location: Florida
Posts: 62

I would be concerned about how much material you have removed in the side skins to make your access openings, especially since you removed it all the way to the top. On my project I made the access hole square, only on one side and left an inch of side skin at the top.
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Old 08-21-2017, 11:02 AM
sblack sblack is offline
Join Date: Dec 2009
Location: Montreal
Posts: 1,524

Originally Posted by Rv3Dave View Post
I would be concerned about how much material you have removed in the side skins to make your access openings, especially since you removed it all the way to the top. On my project I made the access hole square, only on one side and left an inch of side skin at the top.

If there is a longeron there that bridges the gap it should be fine.
Scott Black
Old school simple VFR RV 4, O-320, wood prop, MGL iEfis Lite
VAF dues 2020
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Old 09-19-2017, 08:24 PM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,127
Default The King

I've been doing a bunch of small boring things like trimming, countersinking, priming and deburring. I finished making the access hatch covers and doublers but haven't riveted any of that together yet.

Both tailcone belly skins are ready to glue on.

I found that the only tool that would get in to the top longeron where the jig interferes is a flexible drill extension with a threaded end. I used a 3/8" countersink bit that wasn't in a cage for this.

One night I was countersinking and the radio played some of The King's songs. His songs move. I was moving too, right along with the music. Gotta say that Elvis has that title for a reason.

The bit of red electrical tape is something I use as a marker. I'll frequently countersink a bunch of holes and then measure them to make sure they're deep enough, with the tape keeping me from getting lost - one countersink an a longeron looks much like the one next to it. Here, there wasn't an issue but I used it anyway.

Trimming the tailcone side skins left me with some good quality squigglies. These are the kerf from the nibbling tool. Too bad that there's no use for these.

The aft bottom bay is a bit difficult to get into. Here's a look.

In the background, we're looking up and can see the ceiling. I had the bare structure sprayed with foam insulation, 6" of it, and it's very effective. Before that, I had ceiling outlets added for both the radiant heaters and for ceiling lights. The standard double socket in the top center is for the lights, while the single socket to the top right is for a heater. This gives me a lot of flexibility as to where I put these things.

When the taped skin is back on, it'll be hard to remove the tape after gluing. I left fold-unders at one end of every piece of tape, hoping that I can get it out.

The skin is .040 and is too thick to dimple with my equipment, so I'm going to have to countersink the skin.

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


Last edited by David Paule : 09-19-2017 at 08:26 PM.
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Old 09-25-2017, 08:37 PM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,127

Finally got the aft-most belly skin glued on. This is the one right in front of the rudder. On the RV-3B it's .040 thick and in previous posts you've seen it in progress at various stages.

I used West System's G/flex epoxy, the pre-thickened variant. This is just thick enough that it doesn't run. It's too thick to laminate with, being intended strictly as an adhesive. It's a relatively tough, flexible epoxy but that's relative to stiffer varieties. I chose this on the basis of good results reported by two very experienced and knowledgeable friends. 3M's 2216 adhesive is another that would work well, and perhaps better.

This particular skin was small enough that I could manage it all myself, within the 45 minute pot life. I think that for anything larger than this I'd need assistance.

In the photo, I've got the longer tailcone belly skin clecoed on just ahead of it, to its left.

This aft-most belly skin still needs rivets. More than that, it needs countersinking too. I decided to wait on that until after gluing because even for .040, there's not much cylindrical bore remaining after countersinking, and I wanted the clecos that were in place while the glue set up to give good alignment.

The photo is also here, in case it's not visible above.

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Old 10-02-2017, 10:53 AM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,127

My mentor suggested that I install supports for a future tailcone work platform now, since this would be a lot harder after the tailcone skins are on. Here are the supports at the two aft-most bulkheads.

This is for the F-309 bulkhead, as far aft as the platform will go. Those clecos are simply making sure that the skin, now glued on, stays good until I can get some rivets on it.

And this one is for the F-308 bulkhead.

Then for some reason I decided that this was the right time to make the transponder mount. Why now? Because it gets mounted on the right side of the tailcone just aft of the baggage compartment, and that side was clecoed on at the moment, and also because I had a transponder on hand just for this. It's been suggested that I make a mock-up of the transponder (a very good suggestion, by the way) and use that for fitting but I was able to obtain an actual one and being lazy, used that instead.

Why there? It's not far from a convenient place to hang the eventual antenna and while it's out of the way of the snug cockpit, it's not buried deep in the tailcone. I should have reasonable access to it in this location.

Here goes.

This is the basic mount clecoed in place. I'll probably use LP4 blind rivets when this finally goes on, sometime after the skin is riveted and the canoe is flipped, hard as it is at the moment to imagine those events.

Then I finished up the mount, rounding some corners, final-drilling and adding a lightening hole.

Just to prove that it all hangs together, I temporarily installed the transponder on the mount.

And whew, it fits.

Moving right along, the right hand tailcone side skin's aft inspection hatch doubler needed to be glued on. First it needed to have the nutplates installed and the holes dimpled. I hadn't gotten to the dimples yet when this got taken, but I did do that later.

These photos are also hanging out here, here, here, here, here and here.

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Old 10-26-2017, 08:13 PM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,127

Trimmed some edges the other day to save some weight. I saved about 40 grams, almost 1 1/2 ounces, and it only took me four hours. Anyone can make a bargain like that if they want it badly enough. To honor the effort and keep blood off things, I put two timely bandages on my fingers.

One unexpected workshop observation is that I seem to need a number of different kinds or sizes or colors of tape. They take an entire shop drawer. Who'd have expected that?

The aft-most belly skin has been glued down for a while now. I took the time to rivet it to the flanges.

After that, I went back to the rear spar carry-though, which still isn't riveted. Back in post #209, you can see the rear spar locating fixture I made when the wings were on the stand. It contained a conceptual error that's worth pointing out and you might already know what that is -- the fixture goes inboard of the inboard ribs, and on the fuselage, well, the fuselage is there blocking that location; the fixture can't go to the right place. What to do?

Here's what I did.

1. I got some 1" square aluminum tubes and match-drilled some of the 3/8" spar bolt holes through them. They are 18" long and when pinned into the fuselage spar bulkhead, protrude outboard far enough to work off of them. The top face of the top tube on each side was matched to the top face of the spar, since that was a location point for the fixtures.

2. Since the spar gap in the bulkhead is 1 1/16" wide, I glued some 1/16" model airplane plywood to these bars so that on the front face, the plywood fills the gap between the tubes and the bulkhead. 1/16" aluminum would have worked as well.

3. With the tubes pinned in place, I now had an aft spar simulator face for the fixtures to register against. This located them vertically, fore/aft, in pitch and in roll. The construction of them located them in yaw. What was in error was that fact that they are located outboard of where they were when they were built.

4. I removed the rear spar carry-through and marked a horizontal centerline for the future rivets and the proper length according to the plans. Originally, I'd left the length untrimmed but now I can see that this dimension is reasonably close. It'll get trimmed in length when I first mount the wings.

5. Knowing how far outboard the fixture is now compared to when I built it, I was able to position the carry-through in height so that it should be correct. The main spar is at a 3.5 degree dihedral angle and the fixture is based on that, while the rear spar carry-through is horizontal. This means that the spanwise positioning error puts the rear spar carry-through locating angle that's on the fixture slightly above where it ought to be: the distance is off thusly:

Error = Spanwise error * tangent (3.5 deg.)

So I think that I was able to get reasonably close, as the height error is under 1/16" per inch spanwise position error, and that spanwise error was less than 3/8".

The wings are presently stored out at the airport, half an hour away, and this took a few trips to get nailed down.

The rear spar carry-through is shown on the plans as being held on with a single row of rivets. Not shown are the seat-belt mounts, which bolt through it and the curved pieces at the aft side of the rear spar bulkhead that attach the long belly skin at its shoulders. I need to allow for these, too.

After some more messing around, mostly with getting the rivet spacing so that they would go where they needed to, I riveted the rear spar carry-through to the seat bulkhead. You can see the empty outboard holes for the seat belt anchors.

Then I drilled the exoskeleton angles to the lower longerons for the eventual gluing of the belly skin.

If you haven't seen the two photos in this post, please try
here and here.

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Old 10-30-2017, 08:14 AM
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kentlik kentlik is offline
Join Date: Sep 2015
Location: Oregon
Posts: 919

This is really fun to watch this come along!
RV-7A in progress
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"The credit belongs to the man who is actually in the arena..." Teddy Roosevelt
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Old 11-03-2017, 08:26 PM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,127

Today's job was to glue the long belly skin to the fuselage. I'm using G/Flex epoxy, the thickened variety, which has a 45 minute pot life. A dry run showed that it took me 1/2 an hour to get the skin and the hardware all set up, so I knew I needed some assistance. Dave Dooley stopped by to lend a hand.

The skin and substructure was ready to go, with tape on and the cleco tips oiled.

I mixed up a couple tubs of the glue and we started buttering it on. It went to the perimeter and the shoulders of the bulkheads. Then we lifted the skin into place and with the exoskeleton, started clecoing it all together. We only needed one cleco every four rivet holes but we added a few more, here and there, for assurance.

Then we wiped the epoxy off the tips of the clecos and pulled off some of the tape and made fillets at the edges of the joints. Dave left and I took this not-so-great photo.

After a couple hours I replaced all the clecos with fresh one that I hadn't oiled. The glue had cured enough that it wasn't going to stick to the new ones, and I really didn't want the original ones to get glued into the airplane.

Later still, I removed the exoskeleton and the remaining tape. With the exoskeleton off, the sides of the skin stayed stuck down, a very good sign indeed. I replaced most of the clecos for security anyway since the epoxy hasn't fully cured.

If you can't see the photo above, please try here.

This was an uncommonly productive day. I even had time to start a loaf of sourdough bread for rising and baking tomorrow.


Last edited by David Paule : 11-03-2017 at 08:31 PM.
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Old 11-03-2017, 09:32 PM
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ColoCardinal ColoCardinal is offline
Join Date: May 2010
Location: Morrison, CO
Posts: 372

Too strange. Just by chance, I made a loaf of rye bread today when I couldn't take any more priming and sanding.
Are all of the skins bonded and riveted on the RV3?
Carl - - Morrison, CO
Airworthiness cert issued 12/24
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paid 'til 10-19
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Old 11-03-2017, 10:36 PM
David Paule David Paule is offline
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,127

Bread's good, and compared to an airplane, it's almost like instant gratification.

I made a loaf of sourdough rye a couple days ago - good stuff. Funny that you made a rye loaf too.

The bonding is not to the plans. The RV-3B is a riveted airplane, and riveted only. My mentor is out of state and I went for a visit and was struck by the quality of the rivet lines, which were superior to those on most of the non-bonded airplanes I'd seen. He gave me his gluing process and I started gluing things together prior to riveting. At first I merely used it as a holding fixture, but as I got more confidence with it, I decided to try that aft-most belly skin. That went relatively well and I bonded and riveted some flanges and stiffeners onto this skin.

They came out the way I'd hoped and with considerable trepidation, I decided to go ahead and attempt to bond this skin on.

The overall bonding process takes a fair bit of additional time but it seems to me to be worth it. The initial look of this skin was favorable so I am currently planning to bond the long tailcone side skins on too. After that there's only the cockpit area skins and I'll decide about them when I get to them.

I did not bond the wing, tail or control surface skins. But if I were starting afresh, I believe that I would, especially as the difference is so clearly discernable. Worth noting is that I don't really need this airplane and have no plans to use it as much as I should. I'm mostly interested in it as a construction project and to keep from getting bored or intellectually lazy, and for that purpose, bonding is excellent. So for me, the bonding fits well into the project.

Would I recommend this to everyone? No, of course not. If you want a flying airplane in a realistic amount of time, skip this idea. The airplanes are entirely satisfactory if they are built to the plans.

Am I trying for a Lindy? Absolutely not. In fact, I have no plans to ever again go to Oshkosh at all. In any case, the wings are not nearly show quality. All I'm trying to do is indulge myself.

In that respect it's a bit like baking sourdough bread. It takes longer for somewhat better results, but it's not necessary.

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