September 12, 2008
While waiting for some riveting assistance on the ailerons, I started in on the flaps by deburring the flap spars. Nothing tricky or visually interesting here, so no pictures.
October 3, 2008
Got both flap spars clecoed to their respective lower skins and ribs. That was pretty satisfying after all the irritation I've experienced with the ailerons. The clamp in the second picture is just to hold the rib in place as one cleco is removed for drilling.
October 6, 2008
For some reason known only to Vans, there are a few places in the flaps where shims are required to fill gaps between the skins and adjacent substructure. One place I can understand - a gap formed by the overlap of the upper skin on the lower skin at the outboard and inboard ribs. The upper skin actually wraps around the trailing edge and is riveted to the J-channel formed in the lower skin. Here's a picture of an outboard rib...look closely and you'll see an 0.025" shim under the lower aft side of the rib.
You'll also see that the skin doesn't fit well. That's a topic for a future post.
October 9, 2008
Another area where shims are required is between the aft end of each interior flap rib and the lower skin's J-channel. This is one I really can't understand...why doesn't Van's just make the ribs long enough? Ok, enough grousing already.
One minor catch here...the aft-most hole in each rib's lower flange isn't drilled. That gets done by using the corresponding lower flap skin as a drill guide. Without a cleco to hold them together, the rib flange and skin must be clamped together tightly before the rib's rear tab and shim are match-drilled to the J-channel, pulling the tab into the proper position. Clear as mud, right? Anyway, I used a small piece of plywood and a clamp to pull the flange in place, and another clamp to hold the shim in place as it and the tab are match-drilled to the J-channel. The shim gets trimmed to length after drilling.
October 9, 2008
Another area where shims are required is between the aft end of each interior flap rib and the lower skin's J-channel. This is one I really can't understand...why doesn't Van's just make the ribs long enough? Ok, enough grousing already.
One minor catch here...the aft-most hole in each rib's lower flange isn't drilled. That gets done by using the corresponding lower flap skin as a drill guide. Without a cleco to hold them together, the rib flange and skin must be clamped together tightly before the rib's rear tab and shim are match-drilled to the J-channel, pulling the tab into the proper position. Clear as mud, right? Anyway, I used a small piece of plywood and a clamp to pull the flange in place, and another clamp to hold the shim in place as it and the tab are match-drilled to the J-channel. The shim gets trimmed to length after drilling. Also, the shims were of varying thickness; I used 0.025", 0.032" and 0.040" stock and some trial and error to get a fit. I repeated the same process for all interior ribs on both flaps.
October 18, 2008
With all those shims in place, it was time to drill the flap hinge and lower skins to the skeleton. With the spars and shims drilled, match-drilling the lower skins was easy. Drilling the flap hinge took a little more work, since it's one, long floppy piece of AN piano hinge. There's also very little room for error when drilling it with the proper edge distance as specified by the plans.
The first step was marking a centerline on one leaf of the hinge. I fabbed up a homemade edge marker block similar to the one sold by Avery Tools and marked the leaves of both flap hinges. I then clamped the hinge in place on each flap spar, making sure to align the centerline and spar holes. One minor trick...I used small pieces of thin plywood between the clamps and hinge leaf to avoid squeezing and deforming any hinge eyes. A few minutes with the Sioux and a #41 drill bit, and the hinges were match-drilled to the spar. I then match-drilled the entire structure to #40.
Things were going great, I was on a roll...so I decided to finish up by match-drilling the upper flap skins to the lower skins, spars and flaps I had done over the last two days. I grabbed those flap skins, clecoed them in place...and then found a problem. Remember that picture from October 6?
If you noticed before that the trailing edge bend didn't look right, you're very observant. Other builders have had the same problem with flap skins delivered in late 2005 and received replacement skins at no charge. I called Vans and reported the problem, we'll see what they propose.
October 21, 2008
Vans' response on my flap skin problem wasn't exactly what I was hoping for. They're aware of this issue, but don't ship replacement skins any more. They suggested using replacement inboard and outboard ribs with no prepunched holes; according to Joe Blank at Van's, match-drilling those ribs to the skins will fix this problem. I agreed to try their solution, since the replacement ribs are free. We'll see if they work.
Meanwhile, I did some cleanup work on the flap braces on both wings. One thing I had neglected to do in the past was match-drill them to the lower wing skins. Before I could do that, I had to tweak the braces a bit with a hand seamer to make them line up smoothly with the skins. The braces are left with a bit of a twist due to the way they're riveted to the rear spar and doublers. With a little adjustment, the braces and skins line up nicely for match-drilling.
November 2, 2008
Work has been busy; getting the flap braces tweaked took several days with little time spent each day. After match-drilling, the braces are countersunk to accept dimples in the skins. This leaves the upper surface of the brace flush to mate with the flap hinge. Taking a cue from Brad Oliver, I drilled a piece of wood to each brace to guide the countersink pilot and then countersunk the holes. Easy!
November 9, 2008
The replacement unpunched flap ribs arrived from Van's; the lower flange of each rib is not punched. I was anxious to try them and get going on the flaps. Long story short - the flap skins were mis-bent and no amount of tweaking with the ribs would fix the problem. I spoke to Joe Blank at Van's and asked for new skins. To his great credit, he shipped them right away at no charge and with no complaint. Thanks Joe!
November 21, 2008
Those new flap skins arrived today. I couldn't wait to yank those bad boys out of the box and see if they fit properly. And they did! Very cool.
December 6, 2008
With the flap skins fitting properly, it was time to start fabricating and fitting the flap braces. The aft part of the brace is precut and prepunched by Vans, but the forward angle is fabricated from 1"x2"x0.125" 6061 angle stock. Nothing particularly difficult here, just exercise due dilligence in laying out rivet holes to maintain edge distance on the angle - repeat for the other flap and we're done.
The aft brace also gets a slight bend just behind the area where it joins the angle. The bend allows it to set flush against the inside rib. Here are the two parts clamped together and ready for fitting to the left flap. The angle is predrilled. Sorry, no pictures of the right flap brace...
December 7, 2008
With flap brace parts fabricated, bent and predrilled as necessary I started fitting them to the flap skeletons. The aft-most hole on the rear brace lines up with a prepunched hole on the inboard rib, so positioning the brace is relatively easy. With a cleco in that hole I match-drilled and clecoed the forward end of the brace, then drilled the rest of the holes through the rib. After making sure that the angle was snugly in place and still clamped securely, I match-drilled the angle to the spar...at least the holes I could reach.
The upper flap skin must be removed to finish match-drilling the angle to both the spar and the inboard rib's forward tab - in fact, the spar is sandwiched between the angle and the rib tab. I know, clear as mud. If you're to the point of building your RV-7 or -8 flaps, you'll understand. Some holes can be drilled from the front, but the three holes closest to the angle - the ones that go through the angle, spar and rib - have to be drilled from behind with a 12" flexible #30 bit.
The end result looks like this...
One last detail - that reference hole at the rear end of the brace gets enlarged to accept the rod end that attaches the flap actuator arm. Once that hole is drilled, two others are drilled for the nutplate that holds the rod end. A nutplate threaded on an AN3 bolt made a good drill jig. The forward nutplate hole is countersunk to accept an AN426 rivet, and according to Vans' plans the rear hole should be too...but the rib really isn't thick enough to countersink. I have some AN470-3 universal head rivets, so I decided not to countersink the hole.
December 13, 2008
I repeated the Dec 7 process on the right spar, with the exception of one minor oops...when back-drilling the angle-spar-rib holes I managed to egg out a couple of them in the spar and rib. Per Van's, the spar holes aren't a big deal because the spar is sandwiched between the rib tab and the angle. But the rib holes were not so great either, so I took one of the spare non-prepunched holes (see this entry) for the details) and match-drilled it to replace the old rib. Problem solved.
December 19, 2008
Now the fun part...over the last week I started deburring all those flap components, as well as those for the new aileron. If you have a Dremel tool, buy a 500 finishing wheel - it's essentially a 1" diameter Scotchbrite 7A Medium wheel for Dremel tools, and it's freakin' fabulous for deburring in tight spaces!
January 17, 2009
I've been deburring and dimpling flap components as time allowed over the holidays. Finished 'em today.
January 28, 2009
Nothing to report, I've been on a work trip to Seattle.
February 14, 2009
Still nothing to report, except the reason now is that I just got back from a two-week work trip to Huntsville, Alabama.
February 21, 2009
Got a lot of work done on the flaps this weekend. Friday was a day off for me, so I spent the afternoon prepping and alodining small flap and aileron parts - ribs, stiffeners, brackets and spacers.
It was too cold to spray and scrub the larger flap and aileron parts outside, so early the next morning I hauled those parts over to the Hanscom Aero Club hangar and did all the cleaning, scrubbing and alumiprepping there - nobody minds a wet floor as long as you clean up after yourself. With that done, I packed up everthing including primer, spray gun and miscellaneous supplies and headed up to Maine where my friend Antony Parchment, RV-7 builder and all-around great guy, allowed me to use his paint booth to get all those parts primed.
Antony's paint booth is wicked great - it's collapsible and folds against one wall when he's not using it. I helped him assemble it and got right to work priming. Here's the booth...sorry for the crappy pictures, I did 'em with my cell phone.
And here's the flap/aileron priming in progress.
Meanwhile, Antony worked on fitting steps to his RV-7 fuselage.
After a hard day's work, we hunkered down on some great Japanese food in Portland with Antony's wife and a neighborhood friend. I packed everything up and motored back to Boston. A hard 15-hour RV workday, but worth it. Mission accomplished!
March 1, 2009
Just as soon as the parts had dried, I riveted the flap actuator reinforcement plates to their respective inboard ribs - making sure to get the nutplate in there too. One note here - make sure you squeeze the aft nutplate rivet before you put the reinforcement plate on, otherwise that rivet will be difficult to get with a normal squeezer yoke. The sharp-eyed builders among you will also notice that I used AN470 rivets here; Vans calls out flush rivets but I didn't want to countersink the rib - it's not really thick enough. I had the 470-3s, so I used 'em.
The next day I riveted the rear tabs on each flap rib to their respective skins, and clecoed the flaps together for final assembly. I'm not going to cover assembly of each flap, they pretty much go together the same way. Big thanks to Dave Rogers for letting me use his flap assembly V-jigs. I screwed 'em to my worktable and leveled them to each other - no problems.
One gotcha...after spending all that time in Antony's paint booth, I realized that I forgot to prime the faying surfaces (i.e., skin overlap areas) on the flap bottoms. Since this is an area where moisture can get forced in between skins, I did some quick masking/alodining/priming of those areas and fixed the problem.
March 15, 2009
Did some marathon airplane building over the last three days, and Ellen and I managed to complete the left flap. First, I pulled the bottom skin off and riveted the ribs to it, bucking bar access is a lot better without the upper skin in place!
Next, I reassembled the flap without the spar. Ellen and I riveted the upper skin-to-rib and bottom skin overlap rivets. Access was tight, but the tungsten bucking bar made riveting relatively easy.
Ellen did the shooting, I bucked...
The next day I reinstalled the spar and pop-riveted the rib leading edge tabs. Nothing too tricky here, just need to gently push aside the flap leading egde to get the pop riveter in place. I used my cheapo riveter which I ground down to fit in tight spaces, worked fine.
After that, I solo-shot the upper skin-to-spar rivets and squeezed the rib-to-skin rivets - came out great!
Before squeezing the spar/skin/hinge rivets, I removed one eye from the center of each hinge. This is where the flap hinge pins will be inserted; I liked this idea better than drilling a hole in the inboard aileron bracket to facilitate inserting the hinge pin.
Squeezing the spar/skin/hinge rivets was easy, just had to make sure the squeezer set was narrow enough to make the shop head without hitting the hinge eye.
The only remaining task was to squeeze the rivets that secure the flap brace angles. Easy-peasy...
Don't know why I didn't get a shot of the completed left flap...but it looks just like the right one - so keep reading. One more thing... this flap came out with zero twist. Very cool!
March 16, 2009
In another fit of marathon airplane building over the last three days, I finished the right flap. Did it just like the left one, so I'm not gonna waste your bandwidth with more pictures.
One not-quite-cool note, this flap came out with 1/16" twist. I'm not quite sure how that happened, because I rechecked the jig before starting. But there it is and from some research I found out it's not uncommon, so I'm not gonna stress over it.
With that, I'm declaring the flaps complete...for now.