Wing Tanks and a parts aircraft

4-3-2018 – 3 hours

It has been nearly a month since I worked on the RV6.  That’s for a variety of reasons.  It was a good stopping place, I went on Spring Break and went traveling with the family, I had several intensive issues to take care of at work, and I also had to catch up with grading and preparing papers to keep the students busy.  Of course, there was also the money thing.

Next on the list is fuel tanks.  Unfortunately, some of the parts are missing or were never present since I don’t have the finishing kit.  KW had finished most of the drilling and dimpling of the right wing tank, but none of the finishing or mounting.  The tank is integral to the wing, and needs to be sealed.  I need sealant, and no way that I know of can get around buying the stuff.  I’m going to have to bite the bullet and buy a can of sealant.

I went to the Van’s web site, and a quart kit costs $41.  That isn’t too bad.  If I do it carefully, this should do both tanks.  However, there is no point buying the stuff in advance, as the shelf life is a meager 4 months.  This means I need all the parts  ready to install before I buy it.  I made a parts list, and this is what I need.  (Note that I added a few small parts that would not need to be purchased now, including a new O-ring and the Quick drains).

If you’ve followed so far, you know that $188 isn’t what I want to spend.  Is there a cheaper way?  I think so.  I bought a wrecked badly wrecked RV7, and will be scavenging parts off of it soon.  I’ll make a post about that as soon as the transaction is complete.  I hope to salvage enough salable parts off of it to make it free, but even if that doesn’t work, I can nearly cover what I paid for the plane by taking the scrap to recycling.

Until then, I’ll concentrate on prepping the tanks.  Here is the right one, removed from the wing.

Clecoing the tank together was a challenge, as many of the parts were loose and out of order.  It took some time, but all the parts were found for this tank, and there proper locations were identified.

Here is the plan for the tank.  Lots of consulting this sheet today.

My first chance to try the free #8 screw dimple dies I got in my last transaction.

Here is a #8 screw sitting in the dimple.

Lots of nut plates to attach.  I like to partially thread the nutplate on a screw, and use that to hold the nutplate while I flush rivet the nutplate in place with little bitty 3-3 rivets.  BTW, KW had already drilled and coutersunk for nutplates on the right wing, so this was pretty rapid and easy.

First time looking in this part of the wing.  Note the large number of ribs in the wing walk area.

And here is the 406A and 406B fuel cap and neck.  Still have more nutplates to mount, and I have to figure out the best way to countersink for my #8 screws that require countersinking instead of dimpling.

Something funny happened while I was working with the #8 screw dimple dies.  One of my students grabbed the dimpler while I wasn’t watching, and tried to dimple for #4 rivets.  His buddies teased him pretty hard – but it was funny.  I guess there is nothing like learning the hard way that there are several sizes of dimple dies, and you need to make sure you have the correct one.



Finishing up the Flaps

2-29-18 – 3-8-18.  8.5 hours.

I have always known that keeping up posting on this blog would be tough – and it definitely is.  I see that it has been half a month.  That has been busy time for me, buying a wrecked RV7 for parts – more on this soon – as well as selling stuff out of the hangar to finance the RV6 and annualling a friend’s airplane.  Then there was spring break.  Overall, I guess I’m proud of the 8.5 hours I have managed to spend riveting up the flaps.  Not much in the way of pictures, but both flaps are now pretty much done.  That is the last of the control surfaces.  I definitely enjoyed the flaps the most.

The skeleton – drilled and dimpled.

Riveting the trailing edge “spar” to the ribs.

Everything clecoed in place.  I used huge numbers of clecos in ordre to make the dimples fit down tight and the hole thing “pop” into position.

After clecoing the flap together, the front spar is removed, and the rivets are bucked through the skin seam and ribs.

The most difficult part of the job was reaching the rivets “blocked off” by the flap actuator.  I don’t like “pop” rivets, so these are all solid on my plane.  Lots of creative bucking bar placements.

Nearing the end – the spar gets riveted in.  This involves bucking rivets in the top seam – here almost completed –

and squeezing the rivets through the spar, skin, and hinge on the bottom size.  Much quicker to squeeze than buck.

I thought about trying to use bucked rivets through the spar into the ribs, but decided that this would be overkill.  Note the three cherry-max rivets on the actuator and rib.  I used cherrymax here, as they are stronger than avex.

And here are the avex rivets as per plans on the other ribs.

At this point, I haven’t touched the plane for a week, and can’t wait to get back at it.  The control surfaces are mostly done, and it is time to get to those wings!


Zipping Up the Impossible Rivet Seam

2-18-18 and 2-19-18 – 5 hours

So this session is mostly about closing the impossible back seam on my modified aileron – although my son and I spent also dimpled the second aileron.

He clecos and dimples.  A 13 year old assistant is good news every now and again!  Thanks Jason!  Look carefully, and you can see the laptop playing Pandora tunes in the background.  Also, notice the two flaps and the rudder on the wall.  We’ll be adding to that wall in this post.

Its not a red carpet, but it is a big help.  Here we are assembling the trim tab.

And so we ended up with a dimpled aileron, ready for riveting.

And here is the trim tab, mostly riveted in place on the aileron.

And we ended the day by spraying zinc chromate on the second aileron structure.  KW already got the skin.

And for this act, I will rivet together not one but two impossible rivet seams.  First I have to rivet the trailing rib inboard of the flap.  THer are 7 of these little boogers.  The rib faces into the aileron, so NONE of the rivets are reachable without “going deep” from the other side.  I had a piece of 1″ square aluminum in the shop, and I taped my smallest bucking bar onto a short scrap aluminum.  This will just reach the right area if I can just attach it properly.  It has to be flexible to get into the right spot.

And this, boys and girls, is where to use pop rivets when building an airplane.  Actually, these are worse than pop rivets – they are harbor freight imitation pop rivets.  Think of them as tiny single use clecos.  At a penny each, the cost is right.  These will hold the bucking bar in position, but allow some side to side movement and control.

An here is the jig in use.  I C-clamped the aluminum bar over a 2×4, so it can be shoved into the aileron.

Its hard to see in the photo, but the bucking bar is in there, and in position.  I got 3 rivets without moving the rig.  Riveting like this, you carefully raise the aileron with one hand while you use the gun with the other.  Like any other technique, it takes practice.

Moving up the seam, I withdrew the bucking bar and reattached it – this time in a notch I cut in the aluminum arm.  Electric tape worked well.  This got the last four rivets of the first seam.  Seven rivets in 1.5 hours!  This is why Vans suggests just pulling the back rivets.  About now, I am wishing I had!

Now I’ve switched bucking bars to reach the other (long) seam.  Too bad this arrangement didn’t quite fit due to the height of the stiffeners inside the aileron.

And now I am on to my 4th cantilever bucking bar arrangement for the day.  It looks kind of like a prehistoric spear.  This arrangement worked well.  You can also see the unzipped seam in this photo.

With the right arrangement, it only took a few minutes to zip up the aileron.  I did the previous seam while I was alone in the shop, as I needed to concentrate.  By the time I got to the second seam, class was back in session.  You can see my students busy working on their projects in the background.  This pic shows the seam about 1/4 zipped up.  I kept this bucking bar arrangement taped together, because I’ll use this on the normal aileron tomorrow, DV.

And now I have an aileron to join the “long term storage” wall of parts!  On to the next aileron, which I anticipate will be done MUCH more quickly.

This also is a major milestone.  I have now completed the preliminary structural mods to add my trim tabs.  They say to count on 100 hours per departure from the plans.  I have made two significant departures, and am coming in way under budget on hours according to that math.  Of course, I haven’t added the servos yet, nor have I wired them in to the autopilot, so I still get lots of hours to spend…

Zipping up the Aileron/Trim Tab

2-16-18 – 7 hours spent

So today’s goal was to close the dimpled aileron.  This was a lot of work, because 1) I don’t like pulled rivets, and 2) the internal structure that was added to this aileron to strength it for the trim tab did not lend itself well to using solid rivets.  Still, whats building an airplane for if you don’t like 3D puzzles?

So here is the skeleton clecoed together.  I started with the squeezer, and I wanted the rivet heads (factory) to be facing outward if I ever needed to drill them off and open the rivet.

Unfortunately, the squeezer wouldn’t fit all the locations, so the long #4 rivet set comes out and into play.  And I got out the first bucking bar for the day.

Now its time to drive the skin rivets into the top of the aileron.  This is a relatively simple operation, as the way the skin wraps around the bottom of the aileron, the top rivets are pretty easy to reach.  Other than the need to use LOTS of clecos to keep the dimples nested, it should be pretty straightforward.  And the rivets go in one by one until

Uh Oh!  Somebody (me) screwed up the dimpling.  Here you see the pretty dimple on the skin – but you will notice it isn’t lying flat.  That’s because I didn’t dimple the hole underneath it.

I was going to countersink this hole, because the dimple die doesn’t fit due to the nutplate that is in the way.  There is no way the dimple die would fit before – but now I am up a creek without a paddle.  There is no way I’m drilling out all those rivets and countersinking the hole, and I can’t countersink the hole with the skin over it.  I built that rivet gun dimple adapter yesterday, but that won’t work without a low profile female dimpler.

So its time to modify another bucking bar.  The foot of the standard bucking bar makes a great female dimple die.

And its hard to see in the pic, but now I have ALL the holes dimpled, and the rest of the rivets in the top went in smoothly.

When I say smoothly, that may be a bit of a stretch.  You can see the tools and the coffee mug.  One rivet at a time.

And here is the results on my hand.  Lots stress and one bandaid…

Before zipping up the back, I think that I’d better zip up the trim tab.  It’s going to be a difficult process.

And so I’m motivating by looking at the top surface of the aileron.  I’m pretty happy.

Although if you catch the light right, it isn’t perfect.  Still, it beats a lot of production aircraft…

So before closing the trim tab, I need to add a control horn.  I’m going to put it near the center.  It would be so easy to just make an angle and rivet it on the outside, but I need better than that.  After all, this is probably the only RV6 I’m going to make…

Here is a first try to sketch a control horn that works.  But I really want to catch the front spar and the center rib.  Probably overkill, but I want to make sure that there is no way that fatigue can crack that skin.

So here is the trim tab control horn sitting on the end of the tab.  Of course it needs to be mounted in the middle.

And its going to need a slot cut in the skin.  The most important measurement for this is the alignment with the side of the rib.

Clearing out the slot with 1/8 drill bit.  Then a set of needle files to finish it up.

Here is the control horn sticking out of the slot.  Now I need to ensure that the horn is appropriately situated inside when I drill the holes.  I held the horn against the spar and the rib at the same time, and drilled the angle to the spar.

And here is the horn.  I got the three holes drilled into the spar and the control horn.  I also drilled the back of the control horn, but I have not drilled the rib.  I can do that last – after that aileron is skinned.

Now I have to zinc chromate the control horn.  Back to closing the aileron while I wait until the chromate dries…

Its going to need to be done in the exact right order or there will be no way to git-er-done without those unfortunate “pulled” rivets.  (Spits on floor.)  The good news is that I found the perfect bucking bar.  This little beauty fits exactly in the spot it needs to.

So here goes.  First the underside of the two nose ribs – one faces each direction (outboard).  After I got those three rivets on each nose rib, I had to tuck the rear skin under the front skin.

After tucking the skin in, I used a LOT of clecoes to make sure the dimples align.  Luckily, the trim tab cutout lets me get in there with a long bucking bar.

And here is one side of the aileron closed.  The other side will be a little easier IF I remove the rear rib from the other side, I use my long bucking bar.  But I’m out of time for the day, and its time to quit.

Before I put everything away for the night, I did want to take a picture of all the bucking bars I used today.  So glad that I have a lot of options on the shelf.  There is no way I could do this without pulled rivets if I didn’t have the tools…

More Stuff to Sell

One of the things I promised my wife when I started this project is that I would sell what I don’t need.  With the fresh success of selling the tools I didn’t need for the price I paid for all of them, I am going to sell the parts of the kit I don’t need:

The elevator trim cable.  I’m going digital electronic.

The electric aileron trim.  I’m going to use more modern servos that can be easily interfaced with arduinos.

This is a Falcon DG that I got from another source.  It would go well in any RV’s cockpit that still has a vacuum system.

And here is the BRS system.  It is a 1050 pound unit, so the only RV it would work in is an RV3.

I Begin Dimpling the Ailerons…

2/15/2018 – 4 hours.

So here you see the extent that you can reach the rivet holes to dimple with a 3 inch rivet yoke.  This is obviously not going to cut it, and the reason I had to spend money on a long reach dimpler.

More stuff I can’t reach.

I think the ailerons are particularly hard to dimple, because the skin curls all the way around.  I ended up chucking the dimpler in the vice in order to  cantilever over the other side of the skin.  I also set a piece of carpet up  at about the same height to help me not to scratch up the skin as I work.

Here is the dimpler in use.  I personally found it easier to remover the spring from the head.  This helped me find the holes, support the sheet (critical) in a flat level attitude, and then strike the rod with a hammer.

This is as far as my dimpler will reach, and it STILL ISN’T FAR ENOUGH!  Look close, and you will see 3 rivets that could not be reached.  Time for a little creativity.

I had an old #4 rivet set that ruined the rivets each time I used it.  I chucked it in the drill and ground the end off flat, with a nice bevel.

All I need is a 3/16 inch hole down the center to hold my dimple dies.

Luckily, there is a lathe in the building.  I had a bit of trouble with my old drill bit, but got it sharpened enough to do the job.

Here is the new tool along with the rest of the set.  The bucking bar (which I already had) has a hole drilled in it for one side of the set – in this case the female die.  The male die is in the adapted rivet set.

Look at the beautiful uninterrupted row of dimples!  I really can’t tell which ones were made with each tool (Squeezer, Long Reach Impact Dimpler, Rivet Gun Dimpler).  I do have a couple of cautions:  1) make sure you stay perfectly aligned with the gun, and 2) don’t overdrive.  Both will make you regret your carelessness.

So I also dimpled the structure.  I did have to dissasemble several parts, but in the end I was able to dimple all but one hole.  This was too close to the structure for the dimpler to reach, and I countersunk it

Here is a rudder with trim tab ready to rivet together.

Rudder Trim Tab – Additional Details

2-14-2018 – 3.5 hours and 2-15-2018 0.5 hours.  Total 4 hours.

Confession time – I’m just guessing at hours.  It isn’t simple, because I am also teaching full time while I am working on the plane.  So I just guess at the number of hours I got in, and the number of hours that were spent answering student questions and keeping students from chopping fingers off.

So let’s get on to today’s work – completing the rudder trim tab from the parts I made yesterday…

The first thing I had to work on today was adding a way to remove and install the hinge pin.  This involves drilling 2 holes in the rudder – one through a stiffener and one through the bottom rib.  Note the sheet of folded 0.060 aluminum also in the picture.  This is what I intend to make the control horn from.  It has a wide radius bend, as this has a large minimum bend radius.

Here is the route plan for the hinge pin install/removal holes.

Here you can see the hinge pin emerging from the holes.  Now it is on to making the control horn for the tab.

Here is my first attempt at the control horn.  It is folded from 0.060 2024-T3, and looks great.  The only problem is that I would have to cut into the rudder spar to make it work properly.  FAIL.

Another view of my failure.

Here is the control horn 2.0 being planned.  I used another one of the 2024-T3 fittings that I had.  It has a sharper bend, so I can tighten up the location and make it open and close.

Here is the completed control hon, with most of the riveting done.  (Picture out of sequence.)  The horn should be aligned/streamlined with the direction of travel.

And now its time to talk about riveting.  I planned my riveting poorly, and ended up having to set the rivets with odd shaped bucking bars – one at a time.  I have all but three of the rivets set now, and will bring a thin bar clamp to use as a bucking bar for those last three rivets tomorrow.  (See the picture of the complete trim tab control horn with its missing rivets.)  I will not cut in the access panel for the servo or the control arm slots until I have the servo in hand.

Just a little more piddling around, and I will have my first trim tab completion done.  The extra dimpled holes in the skin will have to be filled before paint.

So I went back in today (2/15/2018) and got those last 3 rivets.  Here is the bar clamp I referred to.  Note that it makes a long bucking bar that covers the entire rivet seem.  It did take quite a few more blows to buck the rivets, but they went in.  Rudder trim tab is done except finishing!


Adding Rudder Trim

2-12-18 and 2-13-18 – 4.5 hours spent

So here is the trim tab I decided to add to my rudder.  Note the holes in the corners of the cutout.  I cut the skins with a Harbor Freight “High Speed Panel Saw.” It worked fairly well after I re-tightened all the loose set screws that it came with.

Here is the trim tab spar.  It extends about 1.5 inches past the trim tab on each side.  This was a complicated fold, as the rudder tapers, so the spar lines are not parallel.  I was pretty happy with how the spar folded and went together – nailed it on the first try!

I drilled the stiffeners off the inside of the trim tab, but cutting away the stiffeners on the inside of the rudder was tricky.  I borrowed a dremel with cut-off wheel, and sliced through the bent portion of each stiffener.  I also ground halfway through the flat portion.  After folding the bent portion relatively flat, the stiffeners could be bent the other way.  A couple of back and forth bends, and they snapped neatly off.

Here are the cut stiffeners.  No damage to the inside of the skins.

Here is the hinge going onto the spar and into the opening.

Spar, hinge, cut/broken off stiffeners, and the c-clamps to get them into position to drill.

So I was so proud of myself when folding the rudder trim tab spar.  Folding the spar for the other side did NOT go well.  The Z-fold didn’t work on my brake, and I ended up trying 5 times before I finally got it right.  Here are 4 failures.  The final one that did work is not in this pile.

The trim tab going together.  You can really see the Z bend in the spar.  I’ll fill the rivet holes before prep and paint.

Trying to dimple inside the tiny spar openings was hard.  I eventually had to build my own very low profile female dimple die.  I chucked a unused rivet set in my drill, and profiled it on the grinder while spinning.  Next, I drilled the hole with a #40 drill bit.  Finally, I finished the countersunk portion with a standard #40 100 degree countersink.

Zinc Chomate on all the new parts.

Next up – forming a control horn and riveting the hole thing back together.