I did a little work on the W-721 flap braces and W-724 aileron seals tonight. I had match drilled them to the spars and skins in a previous session, so this session I focused on deburring the holes, edges and getting them ready for priming. Here are the time lapse videos:
I started out by removing the parts from the wings, and then deburring all the holes in them. I did the Flap braces first, as they had a lot of lightening holes that needed debured as well.
After I had the holes deurred, I needed to trim off a small section of the flap braces, per the plans. Vans put notches in the braces similar to the stiffeners for us to use as guides for our cut lines. I used a straight edge and marked my cut lines.
Then I used aviation snips to cut off the little piece making sure to follow that cut line. There is not much clearance on one of those rivet holes, but folks have reported Vans is aware and tells builders to either skip it or build on and rivet that hole as it won’t affect much where its at.
After I had them trimmed, I deburred all the edges on my scotchbrite wheel, and the removed the plastic from both flap braces. They are ready for scuffing and priming.
Next up was to deburr the holes and edges on the aileron seals, and remove the plastic from them as well. These went quick, theres fewer holes snd not lightening holes that need attention with scotchbrite. After this short work, they were added to the priming pile.
I am going to prime the aileron brackets in my next priming session, so I needed to mask off the bearings really well to prevent paint from getting in them. So I spent a few minutes masking them off and trimming the excess. They are also in the “priming pile”, so it looks like my next build session will probably be either a priming session, or I’ll deburr the edges on the bottom skins.
Thats it for tonight. Quick session, and quick update.
After grabbing a bite to eat after finishing up the wing skins, I came back down and decided to rivet together the aileron brackets. In the last session with these things, I alodined all the parts and sprayed primer on the angle brackets mating surfaces. Everything is cured and ready to rivet together now. Here is the time lapse for this session. The first is the overhead:
The second is the closeup view of my workbench:
I laid out all the parts for the left wing brackets and briefed over the assembly directions and plans. There are a few rivets that need countersunk and a few different sizes, so I triple checked everything, then clecoed the outboard bracket together.
I made sure I was using the correct sized rivets by checking them with a rivet gauge for the -4 diameter shanks. I also DOUBLE CHECKED to make sure I inserted the bearing in between the plates for the aileron bracket before clecoing them together. This would be a hard mistake to learn if I left it out:-)
I also countersunk the correct side for the AN426AD4-7 rivets, and used my squeezer to set them. I also squeezed the AN470AD4-9 rivets They came out very nice:
After getting the W-414PP-L bracket (outboard)
riveted, I moved on to the W-413PP-L (inboard) bracket, and did the same procedure. There were a few spots that needed countersunk rivets, and I made sure to get the oritentation correct.
You can see a small amount of overspray from the self-etching rattle can primer from where I sprayed the aluminum angle brackets mating sides. Oh well, I guess it can’t be “PERFECT”. I am still waffling on if I want to completely prime these brackets or leave them alodined. The plans says they can be left bare, but I may go ahead and prime them just for extra protection? After getting the left brackets done, I moved on to the right, and did the same procedures.
And here is the W-413PP-R bracket. These things look like they are factory made 🙂
Well, except for maybe the rattle can primer overspray 🙂 I decided to wrap up the night with this work. These look pretty great, and I tucked them away into my storage boxes, as they’ll be getting riveted onto the wings in short time. I think I will work on the flap gaps and aileron braces in the next few sessions, and then get them ready to prime. I am thinking I may prime those braces and gap seals and also prime the bottom skins in one session to save a little work. It will be a LONG time before I need the bottom skins, but why not go ahead and prime them now and keep them protected? That will probably finish off the remaining AKZO, leaving me with only a very small amount which is pretty ideal.
Big day today thanks to the help from my wife Tammy! We managed to get the top skin fully riveted on the left wing! This is a big step in the wing construction, as it means the wing can officially come out of the wing stands, and can go in the cradle for the rest of the assembly. I did capture a timelapse, but I think it ran out slightly before we were done. Here is the overhead view.
And this is a closeup I took of the top side of the wing. Tammy decided to be the bucking bar person, and we used the back rivet method to make some really nice looking rivets on the skins. She is holding this bucking bar, and I am using this extended reach back rivet set in my rivet gun, all available from Cleavelend tools, and well worth the small cost!
We started out by looking over the rivet call outs and coming up with a plan of attack. Per the plans, we’d start with the inboard skin, and the center rib of the inboard skin and work our ways outward. So, we picked the center rib, and then the center hole in that rib, and riveted up the rivet line from center, and then down the rivet line from center to make sure the skin stays nice and right. Once we had the first set done on the inboard skin, we removed the clecos, and did the same procedure for the remaining holes. We did however leave the trailing edge on both the skins for the very last, as I could squeeze them by myself. We also made sure to leave the two rows of rivets where the skins over lap alone as well, per the instructions.
You’ll notice we also left the very last rivet on where the skin, rib and main spar flange are for the last, as we’d need to use a longer rivet here. There are several spots on the skins where a few different sizes are use, so we made extra sure to not mix up the rivets. I also would check the tails with a rivet gauge after they were set to make sure everything is coming out correctly. Once we had all the rivets except the trailing edge left, Tammy left to pickup our daughter Acacia from “Nanas” house, so I used my squeezer to set these last rivets. Before she left, she made some neat little notes on which rivets needed the “weird” sized rivets, as they needed to be a little longer due to doublers and skin overlaps. This was helpful!
Eventually we ended up with a very beautifully riveted skin top skin! This back rivet method works very nice, leaving super flush and smooth rivets. All of the skin edges mated up very nicely as well, and I am super happy with the quality of the work we’ve done. There are a few superficial scratches on the skin from dimpling, and being worked on the bench, but they are surface only, and will completely be scuffed away when its painted anyways.
Thats it for this session. Since Tammy had left, and I decided to go up and grab a bite to eat, and then come back down to do some more piddling work while she was picking up Acacia. We are going to rivet the right skin soon, when we are both free again for at least three hours. Maybe next weekend?
Changed it up a bit tonight! I am still holding off on riveting the wing skins until my wife is free to help, which is kinda rare with a 4 year old! So, I decided to go ahead and get the aileron brackets assembled and ready. I also grabbed all the parts from the SB 16-03-28 kit, as I am going to address this now during the build. I did grab a timelapse of the work, heres the overhead view:
Vans ships the brackets in a sub-kit complete with its own plans on how to assemble the brackets. The main assembly plans just shows us the already-assembled bracket and where it goes on the wing. Heres a photo of me studying the plans and the sub-kit instructions.
I had taken some time previously to look over the plans and do some rough assembly of these things just to get an idea. So I dug into it, and got them clecoed together, and then match drilled all the holes.
Once I had the holes match drilled in the brackets, I took the assemblies over to the wing and clecoed them in place so that I could match drill the holes for the brackets with the rear spar, as well as the doublers that shipped in the service bulletin kit. This SB includes a several doubler plates that get mounted on the rear spar side of where the inboard aileron brackets mount, and serve to reinforce this area against cracking. It’s good to get this done while building as its super easy to access. You can see the doublers no the leading edge side of the rear spar (interior of the wing):
You’ll notice in the photos above how the webs that are sticking up in those photos interfere with the rivet holes in the rear spar web where the bottom skin rivets. I marked on these webs with a sharpie where I thought it would be good to remove a small portion of the web to make clearance for those rivets. Later on, I used my bench grinder to grind off this area that I had marked. At this point, the aileron brackets for both wings had been fully match drilled.
Next it was time to deburr the edges and the holes in these parts to get the ready for final assembly. I made sure to keep the left wing and right wings parts separate on my bench, and then disassembled the brackets, removed the plastic and then smoothed all the edges of each part on the scotchbrite wheel. After that, I deburred all of the holes in each part. Reading the plans, it tells us there is only a tolerance of .005″ gap between the two plates of the aileron bracket. I decided to NOT spray AKZO primer on these surfaces because I didn’t want to get too big of a gap, so I am going to alodine them. That will give PLENTY of corrosion protection and be well within the tolerances for gaps. So off to the Alumaprep33 and then Alodine baths!
Instead of wasting time, waiting on the parts to soak in their Alodine baths, I decided to go ahead and match drlll the W-724 aileron gap seals and the W-721 flap braces to the rear spar, since these are my next step. So, I clecoed them into their respective places on the rear spar, in every other hole, and then match drilled both of them to the rear spar. There’s a little trimming work needed on W-721 flap brace, and the holes will need deburred. I am also going to prime these braces and gap seals with AKZO.
The Aileron brackets came out looking very nice when Alodined! The plans do point out to prime the mating surface of the angle aluminum, so I dried the parts and hit them some self-etching primer, right over the top of the alodine. I figured this extra little bit of corrosion protection wont hurt on these angle brackets, and since they are not part of the “sandwhich” for the actual bracket, there isnt a worry of clearance here.
Thats it for tonights work session. I did capture a closeup timelapse, that you can see below. I will let the alodine cure overnight, as well as the rattle can primer, and then start the work of riveting these brackets together, so they can be riveted to the rear spar, after I get the top skins riveted. I only have a couple more work sessions left (priming bottom skins, priming gap seals and braces, etc) before I will be at a critical path waiting on the top skins to get riveted.
Another good session today! I managed to get the right wing to the same point as the left wing, its skin dimpled and clecoed in place, waiting on riveting. Here is the overhead timelapse of the work:
And here’s the “mobile” camera view thats a little closer up:
I pulled the right wing top skins from the paint booth, and got to work removing the blue plastic from the rivet lines on the outside of the skins. I used the dull soldering iron and straight edge trick for this on both skins.
After that, I setup the DRDT-2 for a dimpling session on these skins, and masked off the holes that wont be getting dimpled per the plans. After a decent round of work, both the right wing top skins were dimpled and ready to get clecoed onto the skeleton.
I then clecoe’d the inboard skin to the right wing skeleton, and realized I forgot to dimple the wing walk doubler! So I made a quick trip back to the DRDT-2 and got it all dimpled and ready. Then I slipped the wing walk doubler behind the top skin and clecoed everything in place. I started. by clecoed the very forward edge of the skin to the main spar flange, then working from the center rib of each skin, I clecoed every other hole. Then I placed the outboard skin and did the same with it. I had JUST enough clecos to get every other hole on this wing, minus about 8 holes. I double checked that all the lap joints and skin intersections looked good and took pride in the fact I have what looks like two wings!
Heres the back side of the right wing for completeness:
Yeap. That last picture is every single one of my 3/32″ clecos, all being used. Both wings top skins are now ready to be riveted, and they are at the same spot in the build again. Instead of calling it a day, I decided to go ahead and get the pitot mount plates and braces aldoined, because I could use a small dish to contain the parts. So, I scuffed them up a little, and the put them in bath of Alumaprep33 for 10 minutes.
After a quick rinse of the parts and the plastic dish, I put them into a aldoine bath for a other 15 minutes. Then rinsed them off. They came out looking great!
The sunlight from the window washed the camera photo, but they are indeed a nice and golden color. I’ll leave them alodined and skip priming them, since they will have a good corrosion protection from the alodine. I am going to call some of the local chrome shops Monday morning to see about sending my pitot mast off to be chromed.
At this point, I am ready to rivet on both the top skins for both wings. I’ll wait till I have help to do that, and I think I’ll use the backriveting technique since I have the extra long back rivet set and bucking bar for it. There’s still a few things I can probably do in the mean time, I’ll read up and see whats doable until riveting time. Thats it for today!
This is going to be a long blog, with lots of pictures. So sit back and get ready. I got a LOT accomplished today. It started with the arrival of a few tools I needed. A nibbling tool, and a Tekton 1/4″ torque wrench. I wanted to get the Gretz Aero pitot mount installed, and the hole for it cut in the left wing before I riveted on the top skins. Here’s the ovehead timelapse of the work:
And here is a closeup view, that I moved around the shop as I worked to get a better view of what I was doing:
So, lets dig in to the details. I took a lot of photos because there is a lot of “custom work”, outside of the normal Vans plans, since Vans only has you use a small piece of aluminum tubing for the pitot. I decided to go with a nice heated pitot that has an AOA sensor in it as well, since this airplane will be used for IFR work. I elected to go with a Gretz Aero pitot mount, because I like how the mast screwed in to the wing via reinforcement plates. This makes the entire pitot assembly (tube and mount) fully serviceable in the future. In the end, I really like the Gretz mount and highly recommend it. Here’s what you get in the kit:
The instructions are pretty decent, and I gave them a good read before starting this session, since the mount came in a few days ago. Gretz tells us we may need to file down the openings in the reinforcement plate and washer plates due to slight manufacturing tolerences in the mast itself. They also make these holes very close tolerance to give a very nice finish, but it requires a little filing work on the customers end. I actually like this, as I ended up with a very tight fitting assembly that is going to look fantastic. I just had to use an assortment of files to get the mast tube to fit in the plates first. A half-round bastard file was what I used most, followed by some small round files.
There was a lot of gentle filing, test fitting, filing some more, test fitting, etc, etc, etc. But eventually I wound up with the pitot mast fitting very snugly into the plates:
Next, its time to fit the reinforcment plate (the one with the little joggle on it) to the wing skeleton, and start drilling some holes. The plate does not have any rivet holes, as its designed for the builder to fit it whereever they want. I chose to mount my pitot just one bay outboard of the access hole for the aileron bell crank. This is pretty typical of most RV-7’s, and I figured if it works well for all the others, it should me too. Its far enough away from the tie down ring it shouldnt be a problem, and also close enough to the access hole I can easily service it if needed. The reinforcment plate was designed for a Vans RV airplane, so the joggle on it was just perfect, with only a little forming needing to fit snug. Next, I measured where I wanted the rivet line to be. I found the center of the joggle, and marked the rivet line with a sharpie, and used this same distance for the other three sides as well. I then used a Noxon center-punch to mark the first hole location for reference.
I wanted to verify the lines on the joggle part lined up nicely on the spar flange, and that I didn’t have any interference issues, so I grabbed a cleco clamp, and clamped the plate on to the spar flange, making sure to line up the blue sharpie line with the rivet holes in the main spar flange, then I checked that I had plenty of clearance from the leading edge skin rivets. This looks good so far.
And here’s what it looks like from the bottom side of the wing. Yes, I did indeed write “PITOT” on my wing, so I would make sure I got it in the right rib bays. It also lets you get a better idea of where I am installing this thing on the wing.
Happy with how its looking so far, its time to start drilling the holes into the reinforcement plate! Gretz gives us a rough layout of where the holes need to be, so I used that as reference on how to lay mine out. I used the spot I center punched to drill the first hole, then I cleco’d the reinforcement plate back onto the spar, lined up the blue sharpie line and then clamped it into place so I could back drill the other holes using the spar flange as my guide. Back drilling from the spar scratched some primer off, so I’ll need to touch that up, no biggie.
With those 4 holes done for the main spar flange on the plates joggle, its time to get the rest of the holes done. This was pretty easy as I used a rivet spacing fan to help. I’ve had this tool for a long time, but never really used it much, until tonight. It worked great. Its a nice tool to make very evenly spaced rivet holes! Using the outer hole I just drilled into the joggle, I clecoed the rivet fan in place, and spread it out until I had the 5th hole in the spacer lined up perfectly with my centerline I drew earlier. This gave me 5 very evenly space holes to use.
I center punched the end hole using the spacer fan as a guide, the drilled it with a #40 drill. To get the other three holes perfect, I clecoed the fan at both ends, and then center punched the other three holes using the spacer fan as my guide. Then I removed the fan, and drilled the holes to #40.
I just followed this same procedure all the way around the plate until I had all my rivet holes drilled and nicely spaced. However, Van’s used a different spacing on the spar flange, and I am butting up against the back of the rib so my bottom holes don’t line up exactly to my top holes, but thats only cosmetic, and wont be seen once its all painted anyways.
Now its time to make the small reinforcement bracket that is used to brace the reinforcement plate to the nearest rib. Gretz plans tells us to use .032″ to make the support brace / bracket, and luckily I had a sheet of .032″ in my scrap bucket to use. I clecoed the bottom skin to the skeleton, and then clecoed the reinforcement plate onto the spar flange so I could measure and fabricate the brace.
I made my brace by measuring and cutting a piece of the .032″ aluminum sheet and then bending it to make a 90 degree bracket in my bench vise. Then I clamped it in place against the rib, making sure it was sitting nice and flush with the reinforcement plate. This took a few times of bending, fitting, and bending, fitting again, before I got to what I liked.
I wanted to backdrill the bottom wing skin to the reinforcement plate before I drilled the bracket to make sure the plate was completely flush against the skin. So, I back drilled the wing skin, using the reinforcement plate as my guide, and clecoed the holes as soon as I was done to make sure it didn’t move. Then, I clamped the brace into place against the rib and lined it up with the reinforcement plate. At this point, I had all the holes back drilled into the SKIN from the plate. An important point, since once I had the brace clamped on, I needed to go to the other side of the wing, and backdrill the brace using the new holes in the skin and reinforcement plate as my guide.
After I had the brace drilled and clecoed to the reinforcement plate / skin assembly, I back drilled the plate to the wing rib. I decided to make these holes BETWEEN the holes I just drilled into the plate from the bracket. This would give me clearance to rivet the holes when I do the final assembly and riveting.
I’m committed at this point. The holes are drilled into the skin for the plate, now its time to cut out the hole for the pitot mast into the skin. I removed the skin and the reinforcement plate from the wing, and set it up on my bench. To cut out the streamlined shape of the mast, I decided to drill some holes, and use a nibbling tool. I picked out a drill bit that gave me a decent shape for the small end of the mast hole, I don’t recall the size, I was eyeballing what would get me close. I think it was a 3/8 bit? I used the same bit to drill the hole in the large end, and opened the hole up using a uni-bit.
Notice I did leave the reinforcement plate clecoed on, and marked the hole with a thick sharpie. I am using this as my template for the skin cutout.. The uni-bit was able to get really close to the blue sharpie. Next up I grabbed the new nibbling tool and slowly and gently nibbled out along the blue line. I found that I was able to place the nibbling bit up from the bottom of the skin, and use the shoulder created by the reinforcement plate as a guide for the nibbler, and this worked out very good. Its a great tool for this work, and it costs like 14 bucks!
I worked very slowly and took very small nibbles to make sure I didn’t go to far. I highly recommend using this tool for doing this sort of complex hole cutting. Here is a photo showing where I am sticking the nibbler UP from the bottom side of the skin and using the cutting head to rest on the reinforcement plate to use as a guide. Eventually I had a very nice, rough cut that required very little filing and finish work
Then, I removed the reinforcement plate, and used a combination of files to smooth out the edges of this new hole, and then widen it ever so slightly to fit the pitot mast. Very similar to how I had to file down the plates to fit the mast at the first of this build session. The time lapse show this work much better. Eventually I ended up with a very close fitting hole that will look great for the pitot mount to stick through on the skin! Here is how it looks mid-process:
To make sure everything is correct before I do the last bit of finish work, I clecoed everything back onto the wing skeleton and fit the pitot mast in its new home. It turned out really slick! I am really happy with this.
Here is how it looks on the inside of the wing. This is going to be very easy to service if I ever need to. It’s also very strong with all those plates and braces securing it to the skeleton of the wing, its not just dangling and flopping around from being attached to the skin or an access plate. This is solid.
Then, I dissambled everything, and cleaned up all the holes with some files, deburring tools and scotchbrite. I made sure to get the hole I nibbled in the skin for the mast nice and smooth with no sharp corners to start a crack. These parts are now ready for assembly. I am going to alodine all the plates and braces for the pitot, and then I am considering sending off the pitot mast itself to be chromed at a local old-school hot rod shop thats been doing chrome since the 50’s. I think a chrome pitot mount will look very nice, and be very durable. Maybe it won’t cost much? I’ll report on it later.
I had a few loose ends to finish up tonight. My Tekton 1/4″ torque wrench delivered today and MAN is this thing nice! I am now a huge Tekton fan. This wrench was only about $43 bucks from Amazon: https://amzn.to/33n1Ce2 I love it. I needed to torque down the fuel tank Z-bracket bolts on the main spar web. I decided to go with 40 inch/lbs, as the spec for this is 28 inch/lbs plus the drag of the nutplate. I measured about 14 inch/lbs of drag so I went with 40 inch/lbs and I think thats good. The Tekton has a nice “thunk” when it hits the torque spec. Once I had all the bolts torqued, I marked them with some orange TorqueSeal. I did this for both the left and right wings. The tanks are now mounted!!
Lastly, I decided to go ahead and cleco the left wing outboard top skin to the skeleton, as the left wing is now 100% ready to have its top skins riveted on. It feels amazing! I am planning on getting Tammy to help me do this, maybe the right wing too, later on this week. It’s looking like a wing now!
That’s it for today. This was a LONG work session, and I got a ton completed. I’m stoked to have my pitot mount done, and I’m looking forward to all the rest of the work now. I still need to get the right wing skin dimpled, and clecoed on, so that maybe work for tomorrow. Then I’ll alodine the pitot mount parts, and send the mast off for chrome plating. I think I will go ahead and get the bottom skins primed now as well. They won’t get riveted until WAY later right before mounting on the fuselage, as I still haven’t decided which autopilot I’m going with, or lighting.
Pretty simple build log entry tonight. I got both the top skins dimpled for the left wing, and even got the inboard skin clecoed in place. Heres a couple of time lapse videos of the session:
Heres a little bit better closeup view. When I started clecoing to the skeleton, I moved the camera over to get a good view of that too 🙂
The session started by pulling the skins from the paint booth, they’ve been curing for about 2 days now. Then I setup my DRDT-2 dimpler and removed the blue plastic from the rivet lines on the skins. I used a dull tipped soldering iron to make the removal process a bit easier.
You can see on that right side of the photo above where I sprayed the AKZO primer on the outside facing part of the skin. This is where the inboard skin and outboard skins overlap, so I wanted to make sure there was adequate corrosion protection in this lap joint. Yeah, I sprayed a little to far outside the lap joint, but its no big deal since I plan on painting the airplane anyways. Once the plastic was removed, I masked off a few holes that will be used to attach the fuselage fairing, I dont want to dimple these just yet. Then I used the DRDT-2 to dimple all the skins. After a little bit of easy work, I got both the left wing top skins dimpled:
I also needed to dimple the wing walk doubler as it goes under the inboard skin, between the skin and the rib. So I clecoed it in place to verify I had the orientation right, then made some referenc marks. After that I got it dimpled on the DRDT-2
I decided to go ahead and get the inboard skin clecoed in place tonight, including the wing walk doubler. This skin won’t cause any issues with me installing the pitot mast tomorrow, and there is nothing else left to do on that inboard side, so I clecoed the inboard skin in place, and slipped the wing walk doubler behind the skin and clecoed every other hole, so its ready for riveting. I’ll need to find a helper to get the skins riveted. Then I took a little time to ponder my wiring installations, pitot and AOA plumbing etc. I’ll work on getting the pitot mast installed in the next session, I’ve got a nibbler on the way to make cutting the skin out a little easier.
Delivery day! I got my shipment in from SteinAir, which included my pitot mast, as well as a few 18 gauge ring terminals that I needed to attach the wire to the fuel level sender on the back baffle of the fuel tank. Here’s the goods:
I did capture a few timelapse videos, heres the one from the overhead that captured the full session. I had a few visitors and helpers there for a bit :). My little girl Acacia was playing and my wife was working just outside the shop in her flower garden.
I started off by crimping the proper sized ring terminal onto my 18 gauge Tezfel wire. I picked up a few different sizes just in case.
I inserted a plastic bushing in one of the existing holes in the spar web. It was there from the factory, and in a darn near perfect location. The plastic bushing (I don’t recall the exact sorry unfortunately) will keep the wire from chaffing. I will leave enough of a service loop that the tank can be removed. I’ll also use a pin connector so it will slip through the plastic bushing as well.
Then I sat the tank on the spar, threaded the wire through the bushing and shimmied the tank into place. I then threaded the AN3-4A bolts with their AN960-10L washers into the Z-brackets nutplates. I am only going finger tight for now, as I need to pick up a 1/4″ drive torque wrench. I would use my beam torque wrench but it’s gonna be awkward to use in these spaces. Following that, I threaded all of the AN509-8R8 screws into the tanks skin. Theres a bunch of these things. I did however, tighten these screws down, and I did dab a little Boelube onto the threads to help thread into the brand new nutplates and maybe prevent corrosion. Here’s a timelapse and closeup of the actual mounting work.
And a little bit later, I have the tank mounted! I’ll torque the bolts down on both wings once I get a torque wrench, and then apply some torque seal to them. Now both wings are at the same progress in the build. They are both ready for the top skins to be riveted. I think I will move on to getting the pitot mast done first, then dimple the skins for riveting. Soon they will be off the wing stands and into the cradles for the final control surface mounting!
Thats it for tonight. I need to pick up a nibbler for the wing skins so I can neatly cut out a hole in the skin for the pitot mast. I’ll pick up a torque wrench then as well. Here’s all the photos from tonight:
I was able to get all 4 top wing skins primed tonight. They’re ready for dimpling, and then riveting! It looks like my pitot mast should be here in a day or so, which is pretty good timing, as thats about when I’ll need to get it installed. I grabbed a couple of time lapses for this build session. The first one is the entire session, the other is a shorter on thats close up of me scuffing and cleaning the skins.
I started out by scuffing the 4 top wing skins. I had a bright idea of borrowing my wifes orbital sander and seeing if a scotchbrite pad would stick to the velccro attachment…..AND IT DID!!!
This made is SOOOOOOO much easier to scuff these skins! Just check that timelapse. Each skin was very nicely scuffed in a few minutes with very little work. I did go back over them with the pad in my hands to touch up a few spots, but the sander left a very nice and uniform scuffed surface for priming. After that, I cleaned the skins with MEK and acetone, using a clean paper towel on each wipe till it came up clean. Then off to the paint booth they went. Heres a timelapse and closeup of this work:
And here’s what a skin looks like from using the scotchbrite pad on a sander:
I mixed up 8 ounces of AKZO primer, which seemed to be a little more than I needed for the 4 skins. Not much excess though, maybe 1 ounce? As the AKZO was doing its 30 minute kick off, I setup the paint booth, and then donned my bunny suit. I wound up making some covers for my shoes with paper towels and masking tape. It worked better than I thought!
Heres my obligatory selfie in a bunny suit to show I am doing the work 🙂 I need to replace the dust filters on the respirator chemical cartridges. This bunny suit is also a little worn. I might be able to get the rest of the priming sessions for the wings done with it though.
Then, I sprayed the skins with AKZO in the booth, and did my clean up. I need to spend some time on this paint gun, as my nozzles are getting a bit clogged causing an uneven spray pattern. This is of course a $10 spray gun, so it might be worth trashing and buying new? I have sprayed with this thing a bunch so far, and its give great service up till now. Here’s how the skins turned out:
Thats it for tonight. I’ll let these cure for a day or so, then start the work of dimpling them. After that, they’ll be ready to go on the wing skeleton for final riveting!
Time to get the top skins ready for priming. I’m waiting on my pitot mast and some terminal connectors for the left wing, so I decided to go ahead and start prepping the top skins so they’ll be ready for priming then dimpling. I am priming first, THEN dimpling because its SOOOO much easier on my scotchbrite pads, and I am running low on pads. Hopefully these’ll last until I order my fuselage. I got a timelapse of this session:
I started out by gathering up all the top wing skins. I first went to work on the W-727 wing walk doublers by rounding all the corners and then deburring all the holes. These holes were backdrilled into this sheet, so they needed conventional deburring. Then I took all the blue plastic off of these doublers. After those, I did the same to the inboard and outboard top skins for the left and right wings. I rounded their corners, and then used a bastard file to knock down all the rough edges from the sheering. After I all the rough high points on the skin edges, I went over the edges with a scotchbrite pad to completely smooth the edges nicely, on all 4 skins.
The next step was to remove all the blue plastic from the inside surface of the skins, since I am planning on priming the insides with AKZO. Once I had the plastic removed from each of the skins, I used the edge break tool to for a nice edge break on the skin edges that will be overlapping either another piece of skin or the main spar and ribs. This will make a nice flush joint.
That has all 4 of the large top skins done, so I set them over to the side for now. I’ll be scuffing and priming the inside skin surface in a later build session. For now, I wanted to go ahead and alodine the wing walk doublers. My reasoning is to save some weight, and to provide these doublers a nice layer of corrosion protection. Since they will fit in my alodine baths, it was a no brainer. So, I drug out my alodine equipment and got to work on them.
Typical process: Soak the skins in the Alumaprep33 for about 10 to 15 minutes. I lightly scuffed mine while it was in the alumaprep. Then I rinse off the alumaprep and dunk them into the alodine bath for about 15 minutes. Then rinse off the alodine and let dry. A pretty easy process, and during the waiting times, I reviewed my plans and double checked I was where I needed to be and that I hadn’t forgetten any other steps in the build. The wing walk doublers came out looking pretty nice, with their golden hue.
The doubler on the right of that photo is in direct sunlight so it looks “washed” out, but its the same hue as the skin on the left in normal light. These will be good to go! Then I cleaned up my mess and called it a night. The next build session will probably be a priming session, where I’ll scuff, clean and shoor primer on these skins so it can cure a few days before dimpling. Unless my pitot mast gets here before then!
