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Archive for December, 2011

Flaps Trimmed to Fuselage – 3 hrs

December 31, 2011 Leave a comment

Saturday Dec 31, 2011

Today I finished trimming the inboard edge of the skin on both flaps so they can come all the way up without rubbing on the side skins of the fuselage. This was a slow trial and error process, putting the flap on, check the fit and marking it for trimming, taking it off, trimming a 32nd or so off and repeating the process. I must have put each flap on 10 times. It turned out nice however. This picture is of the left flap down.

And this is the left flap up. The lower flap skin tucks nicely up against the fuselage bottom skin without trimming required.

The right flap looks similar, only mirror image of course.

I found that two of the rivets on the end of the flap were rubbing once I trimmed the edge of the skin back so I replaced the universal head rivets with AN426 flush head rivets at those location. You can see the two flush rivets on the end reinforcement plate in this photo.

The rest of the time I spent cleaning up the shop. It was so messy in here with tools and stuff scattered all around and I decided it had to get back to order for the new year. So that wraps up 2011. Two years down and hopefully not much more than one year to go.

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Categories: Fuselage, Mating the Wings

Aft Wing Spars Drilled! – 12 hrs

December 30, 2011 Leave a comment

Friday Dec 30, 2011

I haven’t posted for three days but I have been working off and on to get the wings aligned to the fuselage in preparation for the big event of drilling the aft spars. In my last post I was working to get the wing forward sweep down from about 5/16 inch. On Wednesday I filed a bit more off of the aft spar ends on both the left and right sides and was able to bring the sweep down to about 1/16 inch. You can see in the photo below that the plumb bob is off by about the width of the plumb line which I estimate is about 1/16 inch. Since Van’s guideline is 1/2 inch or less I am satisfied. Over all I took about 1/16 inch off the wing spar ends and the forward fork of the F705 bulkhead on each side. This is consistent with what other builders have reported.

Then I turned my attention to triangulating from the tail to a rivet on each wing tip. This ensures that the two wings are perpendicular to the fuselage centerline. I measured 173.125 on the right side and 173.187 on the left side, a difference of 1/16 inch. Again, van’s guideline is 1/2 inch so I am happy.

Next was setting the angle of incidence of each wing. This involves shifting the aft spar up or down as required to make both wings have a 1 degree nominal angle of incidence. Vans has you make a leveling tool that spans about 27 inches between the main spar and the aft spar of the wing with a 3 inch spacer to provide a “level” surface when the wing is at the nominal incidence angle assuming the fuselage is level. So I leveled the fuselage first using the main spar as the reference side to side and the side rails for fore and aft.

I started out using my Craftsman digital level measuring the incidence at eight positions across the wing span; near the root, 1/3 span, 2/3 span, and near the end, and I was initially surprised how close the numbers matched. However, after repeating the measurements several times I saw inconsistencies in between the readings on the order of 0.1 degree. I also saw inconsistencies between the digital level and a carpenters bubble level. The accuracy of the digital level is rated at 0.1 degree and I assume that means +/- 0.1 degree which is equivalent to about +/- .047 inches across the length of the tool. And since the nominal incidence angle is 1 degree I was not happy with +/- 0.1 degree accuracy for this critical measurement.

My solution to better accuracy was to combine the digital level with a carpenter’s bubble level and a bull’s eye level. You can see all three in the photo below. After doing some tests I found that I could resolve a relative change of about +/- 0.05 degrees with the bull’s eye level. You can’t see that small of a change on the digital level. Once I got the two wings close to the desired alignment I could look at relative changes between successive positions using the bull’s eye level. If the reading was not dead on bull’s eye I used a .025 thick shim under the end of the tool to put in a small bias angle of about .05 degrees to shift it toward nominal. If it then read zero or shifted to the other side I knew I was within .05 degrees of nominal.

By making multiple measurements across the wing span and comparing them I became comfortable that I could discern relative shifts in the bulls’ eye level of +/- .05 degrees. I also found that slight shifts in the tool placement could shift the results significantly because the wing surface is slanted in both the longitudinal and lateral directions. So I measured the correct positions and put markings on the wing to used as a guide to be consistent. By sharpening up my process this way I was able to measure the variation in the twist of the wings which I could not reliably measure with the digital level alone. It turns out the surfaces of my wings vary a total of about .035 inches from high to low at the aft spar along each wing relative to nominal incidence. This is probably partly twist and partly surface waviness. Whichever, it makes setting both wings to a common incidence a little more complicated.

I made at least a dozen measurements over the last two days combined with small tweaks of the wing incidence. The wing aft spars fit tightly into the fork of the F705 bulkhead so adjustment consisted of tapping the wing on the aft spar with the ball of my fist to shift the position up or down. I wanted to get this right. In the end my final readings came out as follows

Left Wing
End 0.0
2/3 span 0.0
1/3 span  +.05 deg
Root  +.05 deg
Right Wing
Root 0.0
1/3 span  +.05 deg
2/3 span  +.05 deg
End 0.0

At that point I felt that any further adjustments or readings would just be in the noise and a wast of time. So it was time to drill and move on! This is a big deal because once it is drilled there is no going back. I started with a new #30 drill, first centering the drill in the “box” I marked on the aft spar to bound the 5/8 edge distance limits. I drilled a very shallow point first to get it started so it wouldn’t walk on me. Then I used my drill cup to hold the drill perpendicular to the surface and drilled the pilot hole through. To my relief the exit hole was well within the box on the other side of the spar when I checked it.

Then I moved up to a new 9/32 drill bit I bought from Home Depot. To keep it near perpendicular so it would follow the pilot I made a small block of hard wood as a drill guide for this drill bit. It went through and again the exit hole was well within the “box”. Finally, I used my .3125 chucking reamer to drill to final size. The reamer is definitely the way to go for the final hole because it results in a much cleaner, accurate round hole. Some folks use a .3115 reamer to get a tighter fit but don’t really think the extra .001 will make any difference. The final reamed hole on the right wing is shown below.

I put the bolt in without a nut to check the fit and hold everything stable for final measurements to confirm everything remained in alignment through drilling. It did.

Then I decided to put the flaps on to check the fit of the skin under the fuselage. As I put the left flap on bit of a surprise was that the top skin of the flap rubs against the side skin of the fuselage preventing the flap from coming all the way up. This is true on the right flap as well. I looked at the web sites of some other builders and found that this is common so it’s not an indication of anything serious. Just more work to do to trim the flap skin to clear the fuselage.

Categories: Fuselage, Mating the Wings

Right Wing Mated to Fuselage – 5 hrs

December 27, 2011 Leave a comment

Tuesday Dec 27, 2011

As I prepared to mate the right wing this morning I was wondering how I would torque the lower outboard main wing spar bolts. The tough part is getting a wrench onto the nut on the forward side. Then I remembered that I have a set of crows feet and the 11/16 piece just fits into the nook of the weldment as you can see in the photo below. That should do the trick. I got lucky on that one.

Then I installed the pilot and copilot control columns. These are a pain because of all the washers that you have to insert as spacers and they are hard to slip into place between the bearings and the yoke. I decided the easiest way to do this was to install the main cross link first and shim that out so it runs smoothly. Here is a photo of that installed.

Then I assembled the secondary cross link to the two control columns. Here it is laid out on the wing as a convenient surface. I set the length of the secondary arm to the dimension shown on the drawing as a starting point.

Then I installed the columns with the secondary link onto the main cross link. When I checked the parallelism of the two control columns I initially found they were tilted toward each other. So I removed the control columns and readjusted the length of the secondary link. By trail and error I adjusted the link until the columns are parallel as best as I can eyeball it. This is now set up for the aileron linkage checkout coming later.

Then with the help of my daughters again we mated the right wing to the fuselage. This one was much easier and quicker than the left wing. I think the main difference is knowing what to expect and how to wiggle the thing into submission. I love this next picture. There’s an airplane trapped in my garage!

After I leveled the fuselage longitudinally and side to side I made a wing incidence tool like the one described on the drawing. I was anxious about the first measurement because this is where any twist in the wings or fuselage will show up. I checked the angle at four places on each wing and to my great relief they were all right on 0.1 degrees tail high. The absolute value is not important, its the fact that they are all the same that is great news. The wings are straight and both side are the same so concerns about a “heavy wing”, i.e. a tendency to roll to one side or the other are greatly diminished.

Then I ran a plumb line from the tip of the left wing to the tip of the right wing to measure the sweep. You can see the line running under the leading edge and the fuselage in the picture below. I found that both wings have a slight forward sweep, about 1/4 inch on the left wing and about 3/8 inch on the right. These are both within Vans guidelines of 1/2 inch but it’s not good enough for me. I can do better so why not? As expected I found that the rear spar is limiting the forward sweep so I will file a little off to bring the wing tips back a tiny bit.

Jennifer helped me pull the right wing back out so I could get access to the aft spar. In the photo below I have taken just a touch off the forward bar on the fuselage side and I trimmed the upper corner of the wing side where the universal head rivet comes close.

I don’t have pictures but we remated the wing and I checked the sweep again only to find it better (5/16) but still not where I want it to be. So I will give it one more shot tomorrow by filing a little bit more off the spar. Stay tuned for a report on the results.

Categories: Fuselage, Mating the Wings

Left Wing Mated to Fuselage – 5 hrs

December 26, 2011 Leave a comment

Monday Dec 26, 2011

Today I completed a milestone of sorts by mating the left wing to the fuselage. Wing mating is a big event in the build process that involves some anxiety because one always wonders “will it fit”? I started out this morning “warming up” by riveting the flap hinges to the wing. This could not happen until the bottom skins were on of course which I just completed recently. I need these hinges installed because fitting the flaps is part of mating and fitting the wings to the fuselage. The picture below shows a closeup of a section of the flap hinge after riveting because the wide angle view of the whole hinge shows little detail. Riveting these on was not big deal. I used the squeezer on all the rivets so once it was set up it was like a production line.

Then I did something that after reviewing everything at the end of the day probably turned out to be a mistake. I riveted the side rails on the fuselage. These have been clecoed on for a long time and I went past the point in the plans where it said to rivet them on but I learned there is an issue with riveting 705G angles with the side rails installed. I may have to drill out those rivets. More to come on that at a later time.

Part of the prep for mating the wings was to mark the aft spar bars to clearly define the 5/8 inch edge distance required for the attachment bolt there.The center of the drilled hole must be inside that inner box. I marked it on both sides so I can check it on both pieces.

The actual mating of the wing took about an hour with the help of my two daughters, Jennifer and Jessica. There was additional prep time to cut down a saw horse to the right height to support the inboard portion of the wing and to rearrange and prepare the area for the move.

When we began the actual mate the main spar did not slip in as easily as I had hoped. The fit was tight and we had to wiggle the end of the wing to get it to slide in. Also the rear spar of the wing did not line up exactly with the gap between the two bars of the F-705 bulkhead and I had to pry them apart slightly to get the spar engaged. I also had to get under the wing at one point and push up to get the bottom skin of the wing to slide above the bottom skin of the fuselage. But after fiddling with it a while we got it in. The drift pin I made was critical to getting the screws in. Once we got one hole close enough to install the drift pin it pulled that hole into alignment well enough to push the bolt in from the opposite side and drive the drift pin back out. Then Jennifer raised the end of the wing enough to get the camber angle right and bring the second hole into alignment and then the pin would go into that hole as well. That one went in easier if Jennifer wiggled the end of the wing as I installed the bolt. Here is how it looked with one wing on.

I also like this picture from the other side. Believe it or not there is still room to mate the other wing which will allow me to set the wings parallel to each other an perpendicular to the centerline of the fuselage. It’s going to be tough to move around in here though.

Categories: Fuselage, Mating the Wings

A Day of Redo – 4 hrs

December 25, 2011 Leave a comment

Sunday Dec 25, 2011

Merry Christmas! We had family at our home yesterday so today was actually quiet around the house after church and I had a few hours to work on the project after lunch. To prepare for assembling the wings to the fuselage I turned the fuselage cradle around so the tail is facing outward. There is just enough room to put both wings on in this position in the three car garage.

But most of today was about redoing a couple of things I should have done right the first time. Two days ago I started removing the landing gear weldments to file out the holes for the main wing bolts. Today I finished that job by removing, filing, and replacing the right weldment. I hate redoing something I should have done right the first time.

Then I marked the bottom skins of the wings as instructed in the plans. Sorry about the bad picture but in the image you can see horizontal lines from the open hole going outboard and I put tick marks at 3 and 4 inches outboard along those horizontal lines. The idea is to be able to drill through the bottom fuselage skin and hit these holes later, or at least get pretty close to centering on these holes.

The other redo today was to remove the right wing aileron bellcrank and grease the bushing. I forgot to grease it when I put the aileron servo in so out it came. I also took the opportunity to trim the bushing slightly because I had too much free play before and the bellcrank would go “clunk” when I would slide it along the bushing. Now the gap is small enough that you can just barely hear it click if you slide it. Of course the roll autopilot servo is mounted to that bellcrank so it came out with the bracket. Fortunately, I did not have to remove the safety wire.

Finished Right Wing Bottom Skin Riveting – 4 hrs

December 23, 2011 Leave a comment

Friday Dec 23, 2011
Yahoo! I finished closing up the right wing this morning. It took about an hour and a half to finish riveting the last two ribs and the front and rear spar sections between them on the outboard bottom skin. Here is a view of the finished wing still on the work table.

A package arrived from Tower Hobbies today with the control rod hardware I need to mount the Ray Allen POS-12 position sensor for the flaps. I got this parts tip from Mike Bullocks web site. Here are the parts I ordered.  You can see Mike’s installation here.

LXK088 THREADED COUPLER 2-56(0.074″), 2 ea.
LXK064 THREADED PUSHROD 2-56X12″, 6 ea.
LXK077 STEEL CLEVIS 2-56, 12 ea.

And here are the parts. I need one coupler, one pushrod, and two clevis’s for the flap setup but I may use the same approach to install an elevator trim position sensor also so I have extra hardware I can use for that.

I was at Lowe’s this morning and I picked up hardware store bolts for the upcoming wing assembly to the fuselage. I bought eight 7/16 bolts that are 4 inches long and one that is 6 inches to make a drift pin. In this picture you see one of the four inch bolts and the six incher that I modified. I cut off the threaded portion and ground the end of the shaft to a slight taper.

The bad news today is I tried to run the drift pin through the holes in the main spar and I found that it hangs up tight on the landing gear weldment holes. It seems that the holes are not quite large enough or are slightly off center to the spar holes. I wish I had discovered that before I “permanently” installed the weldments a couple months ago. Back when I installed them the plans warned me that I might need to file the holes for the weldment mounting bolts but I did not check the holes for the main wing bolts. My mistake.

So I started the process of removing the weldments so I can file the holes into submission. I got the left weldment removed and filed before I ran out of time (and steam) today. I still need to final torque the weldment bolts on this side.

Categories: Fuselage, Fwd Fuselage, Skins, Wings

More Right Wing Bottom Skin Riveting – 4 hrs

December 22, 2011 Leave a comment

Thursday Dec 22, 2011

Ok, so I admit I am bouncing back and forth a bit between different parts of the project but that variety makes it more fun. this morning I finished building the right fuel vent line. No I didn’t screw it up on the last bend.

Later I continued riveting on the right outboard bottom skin. Here is one of the “down under through the hole” positions used to rivet along the aft spar. The skin is being held up by a string attached to a hook on the ceiling. Photo courtesy of my daughter Jessica.

I finished all but the last bay. The rest will be easy to set by comparison but I’ll have to finish those tomorrow.

Categories: Fuselage, Fwd Fuselage, Skins, Wings