Bottom Skins and Flaps

I haven't posted in awhile, luckily more work has been being done on the plane than this blog. Quite a bit of progress has been made on the wings. The right tank is sealed up and waiting to be leak tested. Then it was time to move back to the left wing. We began by installing the rivets that attach the leading edge ribs to the main spar since we had skipped these before.

Left Wing Torque Tube

We constructed and installed the aileron actuation torque tube for the left wing. Getting this setup correct and tight was an important consideration. Having sloppy bolt holes would mean sloppy control feel, and having the part too short or too long would induce additional stress on the brackets. I think that we did a pretty good job of putting it together, and everything is good and tight. We also constructed the push tubes but set them aside until the bottom skins are riveted on.

Speaking of the bottom skins, they are all prepared for the left wing as well. I want to have angle of attack indication in the plane so instead of using the bent tube pitot that Vans has in the plans we needed a mast to attach either the Dynon or Garmin pitot aoa tube to. I went with the safeair1 pitot mast since it seemed to be the easiest to install and was reasonably priced, at least in comparison to some of the other on the market. I wasn't looking forward to making this cut in that large expensive bottom skin, but using the provided pattern and sneaking up on it with the Dremel tool made it not bad at all. The hole isn't perfect, but it's pretty close. There won't be too many people climbing under the wing to get a look at it anyway.

Pitot Mast

We began to rivet the left bottom skins on but quickly found out that the rivets around the flap hinge brackets were going to require a different tool. The flush set that came with the tool kit just won't get to the rivets that sit right next to the brackets. I've ordered up a long offset flush set but it will take a few days to arrive, so it was on to working on the flaps.

Flap Skeletons Clecoed Together

I got all of the various flap parts deburred and preped for both flaps at once as we have plenty of room to work on both sets of the smaller components. The plans have you cleco the skeletons together, add the skins, and then match drill some holes in the nose ribs as well as the trailing edge. The nose skin is one piece that you form around the nose ribs. When I was installing clecos I didn't notice that one of the ribs was not sitting correctly and the forward cleco pushed the front of the rib over rather than going in the hole like it was supposed to. When I match drilled through the skin the holes in the ribs ended up way off as you can see in the picture. It also tweaked the rib pretty good. I'll be having to order up a new nose rib on Monday. This pretty much killed my plan to have one completed flap today but in the big picture isn't that big a deal.

Misdrilled Flap Nose Rib, Note the Scar Near the Front From the Misplaced Cleco

 Until the long flush set arrives I'll continue preping the flap parts. Things are moving along well, and it won't be too long till we can get started on the tail kit.

 

Flap Hinges

 

Working on right tank and tail kit gets delivered

Been doing some more work on the right tank, and will be closing it up this weekend. I've also been preping the flap and aileron gap fairings getting them ready to install. The big news of the week though is the fact that my tail kit arrived yesterday.

The kit arrived in one box, undamaged this time.

 The tail kit includes the tail cone portion of the fuselage, or everything behind the baggage bulkhead. The kit came in a single crate that didn't really weigh too much. Two of us were able to carry it easily. Once the top was off it was time to look at the new toys. The first thing you see are the two top side fuse skins.

 

Top off the crate and looking at some fuse skins.

There are a lot more small parts in this kit, and it looks like it will be fun building. Plus things are really starting to look like airplane parts as they go together. I'm also looking forward to being done with the tanks and proseal.

One of several bundles of small parts with some stiffeners and longerons in the background.

Another good thing is that I'm going to be home next summer so I'll easily be able to keep progress going instead of falling behind like this year.

 

Back Home and Ready to Work

Well things did not progress as well as I had hoped this summer, but I'm back home for at least the winter and will be back to working on the plane frequently. Over the past few months we got the left tank complete and it tested leakfree so it's hung on the spar. I was also able to get the wiring harness in the left wing as well a tubing for the pitot static and AoA lines. I decided to go with the Safe Air 1 system for the air data tubing since the system seems to offer the best as far as ease of connection and possible future work. I also picked up and will be installing the Safe Air 1 mast for the pitot tube itself. The wing is really starting to look complete with the tank installed.

Left wing with the tank installed.

 

Left wing from bottom showing the wiring for landing light and tip strobes.

Air data lines and ADAHRS wiring.

Now it's time to begin working on the right tank. We started out again by riveting the bottom stiffeners to the skin a couple weeks ago. We were able to get all 5 interior tank ribs installed in one work session over the weekend. We've adopted the opinion that it's better to just cover every joint in a thick layer of proseal and work faster rather than taking a bunch of time to do a super neat job. No one should ever see the inside of the tanks again anyway so all of the masking and such was really just wasted effort. I'm comfortable with the small amount of added weight and the few ounces less fuel capacity.

Right tank with interior ribs sealed and riveted.

 The tail kit is supposed to be shipping the week of October 14th so it's unlikely that we'll have the wing complete prior to it's arrival as hoped, but we'll be pretty close. Hoping to get the right tank completed this week and next weekend.

Slow progress...

I haven't made any updates in the last month because I haven't really gotten anything done. I'm back working on the road again for the summer and I'm lucky if I get 48 full hours at home each weekend. I've devoted my Saturdays to hiking, and with laundry and the normal stuff to get done on Sunday there isn't a lot of time left for the project. The heat hasn't helped my motivation either. It's hard to keep working when it's 110 degrees in the hanger before noon. An airport buddy dropped by Sunday though and was kind enough to lend me a portable swamp cooler to help with the heat. Progress may proceed at a slow place for the rest of the summer.

I have managed to fabricated and place the vent line, adjust and prepare the fuel level sender, and place the fuel pickup screen and return line plug for the left tank. I've also got the skin for the right tank all deburred and the baffle rivet holes counter sunk. The right tank ribs are all final drilled and deburred. I will take some time over the holiday to do some final sealing in the left tank to prepare it for placing the baffle and sealing it up permanently. I will also try to get all of the dimpling done for the right tank. My goal for the month of July will be to have both tanks complete and hung. August will hopefully see the wiring completed and the bottom skins on. I'd like to get the flaps and ailerons built and hung in September. I should be back in the office in October and can go full force again, working on the wing tips and starting the tail, if the kit is available by then.

 

Left tank fuel sender, vent line, and fuel pickup screen.

Left tank progress

Progress on the left tank has been pretty good and working with the tank sealant isn't nearly as bad as I had thought it would be. The stuff certainly makes a mess of everything but if your careful and watch what your doing it's manageable. I bought a quart of acetone and a bag of rags to use for clean up. The rags will be plenty for both tanks, but I should have bought a gallon of acetone. The recommended solvent for clean up is MEK but that stuff seems really awful for you, and is hard to find in CA. The acetone has worked very well as long as you don't let the stuff fully set prior to cleaning.

   

Left tank rib installation with sealant bead

We tried to get 2 ribs done each work session, and the long stiffener done with the tank filler and drain flanges. The inboard most rib and forward attach bracket were done Saturday prior to leaving for the holiday weekend. All the contact surfaces were scuffed up and cleaned well prior to starting, with a final cleaning of the surfaces planned for that day right before beginning. Our process was to mix up the sealant, place three good beads of sealant material on the skin, and then 100% cleco the rib into place. Sealant would squeeze out of the sides and the rivet holes and this sealant would be used to create a continuous fillet of sealant around the edges of the rib. In a few cases the squeezed sealant was not enough to create a fillet large enough for my satisfaction so I added some and spread it out.

Left tank prior to placing inboard end rib

 

Once we were satisfied with the fillet we riveted the ribs into place. Rivets were also cleaned in acetone before use. We would remove a single cleco, place a small dab of sealant on the hole, and then place the rivet. This process left a small ring of sealant around each rivet. There are a few rivets that stand just a bit proud because of the sealant, but I would prefer that to having a leaky tank cause paint blisters later. Finally we spread sealant on the shop head side of the rivets to ensure coverage there as well.

Outboard tank bay with fuel tank filler flange

We put a lot of excess sealant on the long stiffener since we were a little worried that sliding it in from the side would squeegee all the sealant from the inboard end. Turns out this fear was unfounded and we ended up with crazy fillets and plenty of excess to cover the shop heads as well. One rivet on the filler flange will have to be drilled out and replaced. I forgot to install the vent line clip on the aft side as called out in the plans. I thought about just drilling a new hole aft of the flange and using a rivet specifically for the clip, but decided that it would look funky.

The vent line will have to be installed prior to dropping the back baffle and completing the left tank. I ordered up the required tool to create the flare in the tubing, so this will probably get done this weekend. Then it will be time to cross our fingers and pressure test the tank. In the meantime I'm getting all of the parts for the right tank ready. All in all I don't think that doing the tanks is too bad of a project, certainly not as bad as countersinking the spar flange. That said, I will be glad to get them done.

Introduction to Fuel Tank Sealant

 Been working on the fuel tanks all week but haven't accomplished a whole lot. The tanks seem to take extra time, and I'm not sure why. Originally I figured that without having to prime any of the tank interior parts the prep would go rather quickly, but that's not the way it has worked out so far.

 I started out last Friday by breaking a tool which slowed me down some as I waited for a replacement to be shipped. The plans have you countersink (my favorite build activity) the tanks rear baffle. This baffle is the last item to go on, and as such you have no access to form a fillet with the fuel tank sealant. The process used is to layup a pretty healthy bead of sealant on the skin, and then drop the baffle straight down. This should push the bead of sealant ahead and create a good seal. Obviously having to spread the skins to allow skin dimples to pass and then seat could cause a problem, so we countersink. Anyway, I had finished one side of the skins and decided that I could use a break for a few minutes. I knew that I would need to countersink the fuel cap flanges for skin dimples so I decided to knock these out. While countersinking the final hole my hand steadying the flange slipped allowing the flange to tilt and snapping the pilot off of my countersink cutter. I ordered up two this time so that a future breakage wouldn't slow me down.

 

Fuel tank cap and flange. The countersink cutter broke while cutting the incomplete countersink on the right.

 I wasn't comfortable placing any of the ribs without all of the countersinks done on the skins, so there was no rush getting everything preped. Over the next several days I dimpled the left tank skin, got all of the contact surfaces for the left tank roughened and then cleaned well, and continued on parts prep for the right tank.

This past Friday we got our first taste of working with the tank sealant. With the short stiffeners ready to go, and relatively easy to do, we decided to go for it. The first step was to clean the contact surfaces very well so that the sealant would be able to make a good bond. The plans called for using MEK but it seems that it's hard to get in California, so I used acetone instead. After the acetone had evaporated I masked the areas where I didn't want to get sealant, leaving enough space for a good fillet seal around each stiffener. I didn't mask the area where the ribs will go later, thinking that I would just clean those spots afterwards. I'm not really happy with the way that turned out, and I will be masking the rib spots on the right tank for sure.

Left tank skin with the stiffeners riveted and sealed and the masking tape still in place

With everything clean and masked we mixed up a batch of sealant. The sealant is a two part system and claims to have a working time of about 2 hours. I had heard that this stuff smells bad, and they weren't kidding. When I opened up the can of base it smelled like raw sewage, in fact if it weren't for the white color and thick consistency you could easily think you had a can of sewage. After mixing in the accelerator either the smell got a little better or I was used to it. I wasn't sure how much would be needed for each stiffener so we mixed up about 35 grams in the first batch. In the end we would need another 35 gram batch to finish up.

Left tank skin with the masking tape removed

 At each stiffener location we ran about a 1/16" bead all the way around the rivet holes and then a small blob between the interior holes. We then laid the stiffener and placed a cleco in every rivet hole. The clecos did a good job pulling the stiffener in tight and sealant squeezed out of all sides. I then used my finger to form a fillet all the way around each stiffener. There were only a couple of places where we needed to add a little sealant to form a solid fillet.

Once all of the stiffeners were clecoed on we moved the skin into the cradle and began to rivet. The process was to pull a cleco, place a small dab of sealant in the hole, push the rivet thru, and then drive the rivet. This should have created a good seal around the rivet dimple and hole, and after driving there was a small sealant ring around each rivet head.

Rivet shop heads sealed

After all the rivets were driven we used the remaining sealant to seal the shop heads of each rivet. This will hopefully form a complete seal of each stiffener. I then cleaned the excess sealant from each location where ribs will pass thru, and then pulled the masking tape. I feel like the fillet seal may have been compromised while cleaning for the ribs so I'll be sure to place extra sealant during rib placement. When we get to the right tank I'm going to be sure to mask the rib locations as well.

I also received the new countersink cutter Friday, so I was able to complete all of the required countersinking today. Tomorrow we'll start with the left tank ribs. All in all I don't think our first run with the sealant was too bad, certainly not the disaster others have made it out to be. The sealant certainly smells bad and is a sticky mess, but if you take your time and watch what your doing it's alright.

 

Starting the fuel tanks

I've been working on the fuel tanks this week. The tanks seem to me to be a little more parts intensive. I started by getting the ribs for both tanks final drilled, fluted, and deburred. The z brackets that will hold the tanks to the spar web come as one long piece of aluminum formed into the z shape. The brackets have the holes punched in them and have nearly all the material between the individual brackets milled out, leaving just a couple tabs to be cut thru to separate them. After cutting them all free the brackets must be deburred and then countersunk to rivet on the nut plates that will take the AN3 bolts thru the spar web. I really really hate countersinking after the hundreds of holes on the spar flanges, but with only 36 holes per set it wasn't too bad. The z attach brackets are one of the few parts that get primed on the fuel tanks as well.

One set of z attach brackets and the inboard and outboard tank ribs

Once the ribs and z brackets were all set I started to cut the skin stiffeners. The bottom of the tank ribs do not have any cutouts in them, so instead of the full length stiffeners used elsewhere on the wings, the tank bottom gets two rows of short stiffeners that only span a singe rib bay. I imagine the ribs are stronger this way, and the breaks prevent fuel (and more importantly water) from getting trapped behind a full length stiffener. The stiffeners also come as several long pieces of formed aluminum with slots and holes to guide your cutting. After cutting them all free, and there are a bunch of them, I deburred them all and dimpled them. The top stiffener is cut full length from a piece of j channel and match drilled from the skin. Because of my cutting error earlier in the build I had to buy a couple of new pieces of j channel to fabricate these.

All of the tank bottom stiffeners after deburr and prior to dimpling

I went ahead and clecoed the left tank together to match drill it's stiffener, this was not an easy task. The tank skin does not want to take the shape of the ribs and required more than a little persuasion. I even broke out the dead blow hammer to get some of the ribs to line up. I have read other build logs that talk about spending pretty significant amounts of time for each rib when doing the final construction with the tanks sealant, and had wondered why it would take so much time. I don't wonder anymore. Tomorrow we'll be messing with the assembly trying to figure out a good way to get things to fit together easily before trying it with wet sealant everywhere.

 

Left tank clecoed together to match drill stiffener, note the dead blow hammer

 

Right wing structure riveted

Went on a riveting spree the last couple days, and got the right wing top skins riveted on as well as riveting the outboard leading edge together and to the spar. Now both wings are completed to the same stage and are ready for the fuel tanks. 

Right wing with top skins and leading edge riveted on

 I'm out of town for the weekend but I will start preparing all the parts for the fuel tanks next week. Hopefully it isn't as bad as it seems and I can construct leak free tanks on my first try.

 

Left wing structure

Continuing Work On Right Wing

Haven't posted in awhile, but I continue to work on the right wing. Pretty much everything is a repeat of the left wing, but I have avoided a couple mistakes I made and don't have to take as much time studying the instructions. I've got the main ribs all riveted to the main spar, rear spar and doubler plates riveted on, top skins and wing walk doublers ready to go, and everything but the skins ready for the outboard leading edge.

Right wing ribs going on to main spar.

 The right wing should be at the same point as the left in a couple more days work, I just need help to get all the riveting done. I should be getting the j stiffener that I need and the sealant for the tanks any day now so that I can start work on the fuel tanks. I think that I'm about half way done with the wings at this point, so should end up with about 400 hours or so of work on them.

Left wing hanging above right wing waiting for top skin rivets.

 I haven't been working as much on the weekends lately since the weather has been so good, spending more time in the outdoors. It was a very poor winter for snow, with almost nothing left below the 10,000 foot level.

Lake Sabrina

Setting aside the left wing, working on the right.

Finally got the leading edge riveted together and onto the spar, now it really looks like a wing. I was a little worried about riveting the leading edge due to the limited access but it went together quite easily. We turned down the air pressure to the gun and I think the rivets ended up much better. The top skins aren't horrible but there is more waviness and a couple dents that are pretty much absent from the leading edge. We will definitely be using the lower pressure for skin rivets from now on.

Left wing hanging up and out of the way.

I had considered waiting until the very end to construct the fuel tanks, but have decided to follow the plans sequence instead. Building the tanks at this point will allow bolting and torquing the tank to the spar with the bottom skins off. There are plenty of access hatches in the bottom skins, but obviously access is much better with it fully open. I still haven't ordered the proseal or the j stiffener that I need, so I'll spend the next few weeks bringing the right wing up to this point. It will probably work better this way since all of the required tasks are still fresh in my mind from the left wing.

   

Left wing cross section at the tip.

So far I've got the very fun task of main rib prep completed, flap hinges and hinge ribs preped, aileron torque tube bracket constructed, and aileron hinges constructed. I'm working on getting the rear spar and doubler plates all ready to go. Hopefully this weekend I will be able to get all the ribs riveted to the main spar and the rear spar riveted to the ribs. Then it will be on to the top skins and the leading edge. Things are going much faster on the right wing since I don't have to spend so much time studying the plans.

  

Right wing spar with ribs clecoed to spar and bolts installed and torqued.

The down side to working quickly is that it just hastens the start of tank construction. Most of the build logs I've read suggest that the tanks are the hardest part of the build, or the least fun anyway. Hopefully I'll find that it isn't as bad as it seems on the surface.

Right wing rear spar.

Leading Edge

Been working on the left outboard leading edge this week. The inboard leading edge will be the fuel tank since the design uses a wet wing for fuel. The kit is easier than the previous Vans designs since it already has the landing light cutouts in the skin. The mounting bracket is also provided and the skins are prepunched to rivet it to the skins. 

I plan on using a pitot tube and EFIS system that provided angle of attack info so I thought about not installing the standard stall warning actuator. The weight of the unit is almost nothing though, and it was provided with the kit, so I went ahead and mounted it. It's never bad to have a backup right? Plus I would not want to try to install it later with the leading edge attached, the provided access hatch isn't that big. I waited to install the unit until I had squeezed the rivets on the splice rib and strip. That was a mistake! It took me almost an hour to fight with the cap screws and get them all the way in. The screws seem really really long, and the nut plates are formed somewhat out of round to give them a self lock. Now I have to use the warning, just so all that effort wasn't wasted.

Access hatch for stall warning actuator.

Stall warning actuator mounted to splice rib.

    I squeezed the rivets I was able to reach. The rest of the assembly is sitting on the bench until I can get some help to set the rivets. It's much easier to get good quality rivets when your not contorting yourself to reach both sides of the unit. Lee should be able to give me a hand either tomorrow or Friday.

Left outboard leading edge clecoed together and read to rivet

While I'm waiting for help riveting the leading edge, I pulled out the right wing main spar and began working on it again. I got all of the tank attach and access hatch nut plates riveted on and completed all of the countersinks on the bottom flange. I think countersinking is my least favorite task that I've had to do so far, it's incredibly boring and surprisingly tiring.

I found out that I made a mistake earlier in the build as well. The plans have to cut some pieces of J channel to serve as skin stiffeners in certain areas. You can see a piece on the left in the picture below. The kit contains 6 pieces 8' long and 4 pieces 6' long. The instructions don't give an indication on how to make your cuts, so earlier in the build I used 8' pieces to cut the main wing long stiffeners and 6' pieces to cut the main wing short stiffeners. Now I will end up short two pieces to make the tank stiffeners. I should have cut two of the short stiffeners from an 8' piece. I'll need to order a couple of 6' pieces for the tank stiffeners. I can't wait to see that shipping bill.

Looking down the leading edge, the J stiffener is sitting in the cutout in the top of the rib

 

Busy week

Got quite a bit of work done this week on the plane. Riveted the rear spar on to the ribs on Thursday. Got all the top skins dimpled and primed thru the week. Started preparing the leading edge ribs on Friday. Finally got the top skins riveted to the structure on Sunday. There were a total of 698 rivets in the top skins. We managed to set them all with only two small dents in the skin, not really noticeable unless you know where to look, and one of them is in the wing walk area and will be covered with grip tape. I've been working on preparing all the parts for the outboard leading edge the last couple nights, and hope to have it riveted together and onto the spar this weekend.

 

Top skins clecoed on and ready to rivet.

Most of the rib and rear spar rivets set.

Underside of the left wing with all the top skin rivets set.

Slight corrosion on a leading edge rib.

Ribs riveted on

No work on the plane this weekend, but the last couple days have been productive. A friend who built an RV 9 had some extra nut plates laying around so he gave me enough to get one wing done. With help from Lee I got the nut plates riveted on, countersinks done, and the left main ribs riveted to the main spar on Monday. Tonight I clecoed the rear spar and doubler plates on to the ribs, got everything final drilled, countersinks where called for, dimples in the flanges, and everything deburred and ready for primer. I'll get the rear spar and doubler plates primed tomorrow and start working on the top skins. I'd like to have the top skins on before the weekend is over. Things are actually starting to look like a wing now.

More incorrect parts

I've been working on the plane a few hours each day this week. I'm still waiting on the correct tank attach nut plates to ship from Vans so there isn't any big hurry. I spoke with them today about another issue and I was told that the nut plate manufacturer was between runs. They aren't sure when they will receive their order and can ship, hopefully not too long.

In the mean time I've gotten a few things done. All of the left wing main ribs are ready to rivet on. There are a ton of skin attach holes on the main spars that have to be countersunk to accept the skin dimples. Just countersinking all those holes took about 3 hours of work.

Countersunk skin attach holes in left wing spar.

  I also started on the rear spar prep work so it will be ready to attach once the ribs are on the main spar. There are three doubler plates that attach at high stress areas where the aileron and flap hinges attach, as well as a reinforcing fork and doubler at the fuselage attach point. All of these doubler plates are now final drilled, deburred, primed and ready to go. The fuselage attach point is a critical hole and requires a precise ream in a drill press. I don't have a drill press in the shop so I'll need to pick one up or take the parts to someone else's shop to drill.

The aileron hinge brackets that attach to the rear spar have also been constructed. One of the nice things about this kit is the fact that nearly all the moving parts run on bearings. This contributes to the light and smooth control surface movement that makes these planes such a joy to fly. A lot of kits, and even production aircraft, run everything on bushings. This contributes to the heavier feeling in the control surfaces of some aircraft.

Outboard aileron hinge bracket parts final drilled primed and ready to assemble.

Inboard aileron hinge bracket clecoed together and ready for rivets.

 

 

Inboard and outboard aileron hinge brackets riveted together and ready to install on rear spar.

With the rear spar prep pretty much complete I was at the limit of how far ahead I wanted to get on the main structure. I decided that I would go ahead and build the ailerons while I waited for the nut plates since they are stand alone components and would be easy to store out of the way. I flipped over to the aileron plan sheets and began to gather the parts I would need. When I pulled out the very first parts I noticed that my parts looked nothing like the  parts shown in the plans. I decided that I had got enough done for the day and would call builder support to find out what was going on. After speaking with them today I guess I got sent old versions of the parts and will have to wait for the correct pieces. At least these parts shouldn't be on back order.

Incorrect aileron hinges sent with my kit.

 I really don't want to stop the build for a week just to wait on parts, so I pulled down the right wing main spar and began to work on it. Depending on how long it takes to get the nut plates I may bring the right wing to the same readiness as the left. I still want to work on the main structure of one wing at a time due to space constraints, but I guess it won't be all bad to have all the right wing parts ready to go later on.

Rib prep continues

So it turns out I way underestimated the amount of work that goes into preparing each main rib. I've been down at the hanger a couple hours each night the last few days working on drilling the systems holes and priming. I would have finished but I ran out of primer. I've read some guys saying they only used 8 or 10 cans of primer on the whole airplane, I've got 3 cans just on the ribs. I don't think I'm putting too thick a layer on either. I'm not sure where the difference is.

Rib work continues

Well I almost completed the rib prep today. There are 48 skin attach holes, 7 main spar attach holes, and 4 rear spar attach holes on each rib. Each hole has to be final drilled, and deburred, with nearly all the skin attach holes also being dimpled. And there are 14 ribs in each wing. That's a lot of holes, it was a big job so say the least. And I forgot drilling and enlarging the wiring holes for snap bushings. I'll be doing that tomorrow, along with priming each rib.

 

 The flap hinge brackets and the aileron torque tube support are all primed and ready to install on their respective ribs.

 

 

In order to drill the top and bottom bolt attachment holes and final drill the main spar attach rivet holes I had to cleco all the ribs in place on the spar. It was nice to be able to see the structure coming together. 

I realized a mistake I made in dimpling the ribs during the prep stage. The plans have you only dimple the bottom flange of each rib at this point, dimpling the top flanges just before placing top skins. The reason for this is that the ribs at the wing walk do not get dimpled on the top flange, but skins get countersunk. Following the plans method would require dimpling 220 holes with the squeezer, while the structure is riveted together. I decided that I wanted to use the DRDT-2 to form all the dimples, easier and quicker. I carefully noted which ribs were in the wing walk area and set them aside to not get dimples in the top flange. Somehow though I ended up dimpling the W-1010R top flange. An online search showed that I was not the first to make this mistake, and the others were told by Vans to just press out the offending dimples, so that's what I did. I'm going to make triple sure on the right wing that I don't dimple the tops in the wing walk area, in fact I probably won't dimple any of the top flanges until I've clecoed the ribs on the spar.