Priming Skins, Flap Braces, Etc. – 7 hrs

Sunday Apr 3, 2011

My key objective today was to get the flap braces and wing bottom skins primed. This should be my last priming operation for the wing kit build. Along the way I put off work on the wing access covers so I realized that I better get those prepared for priming also. So I first match drilled the holes for the mounting screws; #6 along the top row and #8 around the rest of the perimeter (remember to check the drawings).

Match drilling access covers

Then I removed the vinyl on the inside surface (facing the interior of the wing) and deglossed the surface with a scotchbrite pad attached to my orbital sander. Next I dimpled the holes using the appropriate size dimple dies. Here are the six covers prepared and ready to clean and prime.

Access covers dimpled and deglossed

Next was dimpling the wing skins. There are a lot of holes on those skins and this task took the better part of two hours to get all those holes dimpled. I did not take pictures of that process. You’ll seen it before if you look at some of the earlier posts. With dimpling done I was ready to prime. So I grabbed the Simple Green bottle and a hose and did a complete wash and scrub down of all the surfaces to receive primer. Handling the parts with nitrile gloves, I dried the parts and put them all in the spray booth. About an hour and a half later all the parts had been primed and were drying. The Stewart Systems primer dries pretty fast, especially if you can get a little direct sun on the parts, and they could be handled in about a half hour. Here are the parts after priming and vinyl masking was removed.

Skins, flap braces, and access covers primed

A day without driving rivets is missing something so I installed the two nut plates on the flap braces for hinge pin retention.

Nut plate for hinge pin retention

While I was tinkering I remembered that the aileron pushrod on the left wing was running a little bit close to the cutout in the aft spar so I took out the rotary tool and opened up the kidney shaped hole just a little on the upper end (right in this view). Now it clears the pushrod by about 0.100 inch at the closest point. I put a little touch-up primer on the bare metal when done.

Aileron pushrod hole

Denise was still out shopping so I went ahead and installed the nut plates on one of the inboard bottom skin sections (two access covers). First you have to match drill the nut plates to the skin, then dimple the nut plates and the skin holes.

Installing nut plates for access covers

Then just squeeze the rivets to mount the nut plates and done! Two down and four to go (you can’t see the other set in the picture below).

One set of nut plates installed

In this picture you can see that inboard skin section cleco’d to the wing with the nutplates installed. That section is now ready to be riveted to the wing but I will hold off until I am sure I have all the internal work of the wing done first like electrical wiring and pushrod rigging.

Skin primed, dimpled and ready to rivet

Right Flap Brace and Skin Prep – 7.5 hrs

Saturday Apr 2, 2011

The pictures don’t really show it but I did a lot of work today. First off, I machine countersunk the right flap brace for the skin dimples. That didn’t take too long.

Right flap brace holes countersunk

Then I measured, cut, and bent the flap hinge pin just like I did on the left flap. That includes making two more clamps from excess hing stock and drilling and countersinking for a #6 nut plate.

Right flap hinge pin mounting

Then I started preparing the flap braces and bottom skins for priming. Initially I thought I could get them prep’d and primed today but as time went on I realized it wasn’t going to happen. It just burns up so many hours deburring all the edges, removing vinyl in selected areas, deglossing the areas to be primed, and cutting scarf joints in the overlap area. My goal changed to just getting the parts far enough along that I have a shot at priming tomorrow. Here you can see one of the inboard skins with vinyl removed for priming.

Devinyling, deburring, deglossing bottom skins

Here is a closeup of one of the scarf cuts on the front corner where the skins overlap. I scarf both skins on the inside surface so the scarf is not visible from the outside.

Closeup of a scarf joint

Here is one of the outboard skins. A lot of area, a lot of edges, and a lot of time.

Outboard bottom skin prep

I used the edge forming tool on the inner overlap edge of one of the outboard skins but I just ran out of time before doing the other one. And tomorrow I still need to dimple and clean everything before priming.

Mounted Right Flap – 1.5 hrs

Thursday Mar 31, 2011

Tonight I set about to mount the right flap to the wing skeleton. First I rechecked the straight edge on the end rib of the wing to establish the trail position of the right aileron. Remember: measure twice, drill once.

Rechecked aileron alignment

With that confirmed I placed the right flap on the wing and clamped it roughly in place with a couple of cleco clamps. Then I tweaked the position longitudinally for a 1/4 inch gap between the flap and the aileron and I used a bubble level to set the trailing edge level with and parallel to the aileron trailing edge. After checking it about five times I was ready to start drilling. In this picture you can see the flap aligned and I have already drilled two holes at the far right end of the hinge. I used a few clecos to hold the flap brace in position relative to the wing skin but the clecos tend to push the hinge inward away from the skin so I kept the clecos along that row at least 6 to 8 inches away from where I was drilling. That seemed to work fine.

Flap aligned and drilling started

Here is a shot after all the holes were drilled through the hinge and cleco’d. Yay! Both flaps mounted. Now I get to take it apart, deburr it, and cut and mount the hinge pins like I did on the other side.

Flap hinge drilled and cleco'd

But before that I started removing vinyl from the bottom wing skins. This is just one of those boring, time consuming tasks that I have to do so I will spread it out over time as I do other things.

Started removing vinyl on bottom wing skins

I got word from Vans that my slow build fuselage kit was shipped today. It should arrive at my garage by Tuesday next week. Thus starts Phase 3 of a 6 phase plan; empennage, wings, fuselage, finishing, firewall forward, avionics!

Left Flap Hinge Pin – 2 hrs

Monday Mar 28, 2011

After researching the two recommended methods of installing the flap hinge pin I decided to use the method where the pin is split in the middle and clamped down to the flap brace. I want to be able to remove the flap without removing the aileron first and this method lets you do that. So I cut the hinge pin into two pieces, both longer than necessary and bent one end 90 degrees then added a jog of about 30 degrees as you can see in the picture. I had several feet of excess hinge stock left over so I cut two pieces of one loop each which slip right over the end of the pins. The hinge pieces overlap so I drilled one .144 diameter hole through both pieces and through the flap brace. Then I trimmed the ends of the pins to fit nicely. Most of the time was spent measuring and getting things lined up properly for a good fit.

Flap hinge pin mounting

I lined up a #6 screw nut plate with the hole and drilled and countersank the rivet holes for the nut plate. I will install the nut plate after I prime the flap brace.

Countersunk for a nutplate

Then I used a microstop to countersink the holes in the flap brace for the skin dimples.

Machine countersink flap brace holes

Finished Right Flap – 6.5 hrs

Saturday Mar 26, 2011

First in the agenda today was to finish the right flap. Having just done the left flap last weekend the procedure was fresh in my mind and it went smoothly, taking less time than the left flap. The process was basically identical to the steps I posted before so I did not take many pictures. Here is the right flap finished except for riveting the hinge to the spar. Before doing that I wanted to check the alignment to the wing to make sure which loops of the hinge I wanted to remove near the middle for installing and removing the hinge pin. Disclaimer: I came up short three MK-319-BS rivets in my inventory for some reason so I could not install those on the inboard rib. I’ll have to order some more from Vans. They can be installed anytime.

Update: I found five more MK-319-BS rivets in my kit in the stall warning subassembly bag. I used solid rivets to install the stall warning switch so I used the rivets to finish the right flap.

Right Flap Finished

Once the right flap was done I started the alignment of the left flap to the wing. I wanted to get the wing half of the hinge aligned and drilled so I could move on the cutting the hinge pin and making a tie down point for it on the  flap brace. The plans don’t really help much on this area. The drawings are about the only help Vans give you on this. But I researched how others have approached this process so I had a pretty good basis for my plan. The first step was to align the aileron longitudinally. That means putting the right number of washers between the outboard aileron bracket on the wing and the bracket on the aileron itself. With that done I installed the tool that Vans provides to set the aileron in trail to the wing. Then I mounted the flap using one cleco clamp at each end to hold it in place. I checked and adjusted the gap between the aileron and the flap to 1/4 inch per the drawings. I adjusted the position to make the trailing edges co-aligned.

Aligning left flap to the wing

I also checked the level of the aileron and the flap. They don’t need to be exactly level, they just need to match.

Checking level on aileron and flap

When everything looked right I began drilling the hinge starting on the left end. I drilled with light pressure, and put a cleco in every hole. Here is the end result with the hinge completely drilled.

Flap hinge drilled and cleco'd

Then feeling all satisfied with a job well done I realized that I forgot to check the actual angle of the aileron relative to the tooling holes on the end ribs. Darn it if the aileron wasn’t slightly off in the up direction. I removed the lower outboard skin so I could get to the aileron pushrod and adjusted it. After lengthening the pushrod a few turns I got the tooling holes aligned using a piece of aluminum angle as a straight edge. This picture is not very good but take my word for it, the center of the holes are now aligned to the edge of the angle.

Setting left aileron in trail

Then I rechecked the alignment of the trailing edge of the flap to the trailing edge of the aileron and now there is just a slight offset with the aileron about .010 aft of the flap. It’s a tiny difference and you can’t see it with the naked eye unless you put a straight edge across the two surfaces so I ‘m not concerned about it. But it bugs me a little that it would have been perfectly flush if I had adjusted the aileron before drilling. Live and learn. Measure twice, drill once!

Edge alignment check

Started Assembly of Right Flap – 1 hr

Tuesday Mar 21, 2011

Tonight I cleco’d the ribs and bottom skin to the spar of the right flap and riveted the FL-706A reinforcement angle to the spar with five universal head rivets shown here.

FL-706A riveted to the flap spar

Then I riveted the ribs to the pseudo-sparthat is actually part of the bottom skin using the small shims custom made to fill the gap that naturally occurs.

Ribs riveted to the psuedo-spar

Then I cleco’d on the top skin and set the flap in the stand. Next step (another day) will be riveting the ribs to the skins. That’s all I had time for tonight.

Skins cleco'd on and ready to rivet to ribs

Finished Left Flap – 2.5 hrs

Monday Mar 21, 2011

Tonight is the final push to finish the left flap. Picking up from yesterday I riveted the spar to the ribs using LP3-4 blind rivets. The upper most row was tight with the top skin in the way but I was able to get them in. Then I riveted the top skin to the spar. The prescription here is rivet gun, flush set, tungsten bucking bar. No problems. Here is a sample of some of the rivets.

Flap spar to top skin rivets

Then I riveted the inboard reinforcement plate to the reinforcement angle on the spar. That is the top row of fiver rivets in this view.

Inboard reinforcement rivets

Then I riveted the hinge onto the spar/lower skin. But first I removed three hinge eyelets at the middle of the hinge assembly so I can install the hinge wires from the middle out. This is the alternate method described in the plans that makes it easier to install and remove the flap. I just cut the eyelet off with the band saw and smoothed the edge with the scotchbrite wheel.

Hinge riveted to bottom skin and spar

By the way the seam of the skin overlap region turned out really well. I mentioned several days ago that I used the edge forming tool to bend the edge down a few degrees before dimpling the skin. In the picture below you can see that the seam is completely flush. I doubt it would look this good without forming the edge.

Skin overlap nice and tight

Here is the completed flap. One down and one to go.

Left flap done!

Left Flap Assembly, Part 2 – 5 hrs

Sunday Mar 20, 2011

This morning I began riveting the left flap skins to the skeleton by riveting the longitudinal row of rivets that join the top skin to the bottom skin because those rivets are down in the bottom of the interior. The idea was to start there and work my way up to the spar. First step was to wrap my bucking bar in foam packing material and tape to keep from scratching the skins up inside the cavity. I left two open areas where the bucking will take place.

Bucking bar wrapped up for protection

I also put a piece of foam packing material down in the bottom of the cavity for extra protection. In this picture you can see I’ve riveted a few of the rivets in the first cavity. It turned out all I had to do was put one finger behind the bucking bar with slight pressure to get a good rivet with the flush set on the rivet gun. The weight of the bucking bar was resting against the foam material.

Reaching the rivets way down inside

The rivets along the ribs turned out to be harder because the space is too narrow for my big hands to hang on to the bucking bar in those tight confines. So I used wood blocks to support the weight of the bar. I also taped a paint stirring stick to the bar so I could hold it above the cavity. That helped quite a bit.

Riveting skins to ribs

Here is the make-shift bucking bar handle.

Improvising for better reach

There is one rivet directly underneath the nut plate on the inboard rib that I tried to shoot but the bucking bar wouldn’t get enough area on the rivet shank and it rolled off the edge when I drove it, leaving an unacceptable shop head. So I drilled it out and installed a MK-319-BS blind rivet instead. You can see it right below the nut plate in this photo. I’m not the only builder who has done this.

Used a blind rivet right below the nut plate

In this photo the skins have been riveted together and to the ribs but the spar is not installed yet.

Skins all riveted to the ribs

Next I riveted the FL-706A reinforcement angle to the spar. These rivets are unreachable after the spar is installed. Notice that the shop head is on the thicker material side as is recommended.

Riveted the reinforcement angle to the spar

Then I cleco’d the spar and the hinge to the skins in preparation for riveting. But not today. First I have some shop rearrangement to do.

Spar and hinge cleco'd and ready to rivet

I finally took down the wing assembly fixture, freeing up space I will need to build the fuselage. I saved the pieces however because I might reassemble it behind the paint spray booth to provide more storage space. I think I will need it when I start unpacking the fuselage parts.

Wing stand is gone!

Flap Parts Primed, Assembly Started – 6 hrs

Saturday Mar 19, 2011

This morning I picked up where I left off last night with deburring, deglossing, and dimpling the parts for the left flap. This is a necessary process but a slow one. It took a little more than two hours to finish the left flap parts.

I have to say that the instructions for the flaps are a little short on details. You have to think the process through based on the drawings. The plans don’t prompt this but I used my edge forming tool to put a slight bend in the edge of the top skin that overlaps the bottom skin. This is to get a nice tight overlap on the free edge. I’ll let you know how it turns out.

After all the parts were ready I needed to clean them before priming. Since there are quite a few parts and some are large I did something a little weird. I put them all in the shower and went in with some scotch-brite and the Simple Green. It was much easier to rinse them in the shower than in the sink. Then I dried them and set them up in my spray booth for priming. I have learned to wait a while for parts to air out in case I missed any water. After spraying on a couple of light coats of Ekoprime I laid them out on the work bench to dry. Here are the parts for the left flap.

Parts of the Left Flap Primed

A few hours later I began the assembly starting with the nut plates and reinforcement plates on the inboard rib. These are riveted on with the pneumatic squeezer.

Nut plate riveted

Then I cleco’d together the skeleton of the left flaps and cleco’d on the bottom skin installing the shims I made for the aft end of the inner ribs. I then riveted the inner ribs to the bottom skin on the aft end.

Skeleton cleco'd to the bottom skin

Next I made a stand for the assembly as recommended in the instructions. This was made from scrap material I had lying around including some self adhesive foam weather stripping to protect the skins from scratches.

Made the assembly stand

I slipped the flap into the stand and it fit like a charm. This guy is now ready to be riveted from the inside out – but that will have to wait for tomorrow.

Flap inserted into the assembly stand for riveting

Overall good progress today!

Deburring, Deglossing, Dimpling on the Flaps – 2.5 hrs

Friday Mar 18, 2011

Tonight was spent deburring edges of the skins, deglossing the surfaces to be primed, and dimpling holes to get ready to prime parts for the flaps. I finished the parts for the right flap, tomorrow morning I will start again on the left flap. In this picture you can see the selective removal of vinyl and the surfaces are deglossed. Next step is dimpling the holes.

Flap skins being prep'd for priming