Fuselage, Part 5 Edge Distance

As others have said, the forward fuselage becomes an exercise in edge distance. This means the closeness of a hole to the edge of the aluminum. It is suppose to be 2 times the hole diameter from the center of the hole to the the edge. So a little fancy math gives 1 1/2 hole diameters from the edge of the hole to the edge of the metal.

This first became a problem for the F-623A clips that couple the mid and aft fuselages. In the picture you will see the plans-built version all primed and ready to go. The non-primed are the ones I remade to solve the edge distance problem as evident by the "x" on the part, where the hole would have ended up.

 Everything was going great until I arrived at the F-719 installation. These parts are "joggled" to overlap the F-904 bulkhead. My parts didn't fit very well; and the rivet would have been right at the jog.  I ended up adapting, as builders often do, and used a second angle piece as shown in the picture. I will round the edges so that these pieces play nice with the passengers. 

Following others advice, I was very careful to measure all edge distances before drilling. Some are VERY close. I followed the plans and drilled the holes in the F-713 longeron on the center line, this puts the hole in the F-9101 close to the edge. But there is also a 3/16" bolt that goes thru this longeron for the front tank mount; everything must be dead nuts on. The F-9101 needs to have the edges radius per the plans, otherwise the holes in F-713 are pushed pretty far off as shown in the picture.

       

So far the kit pieces do fit together very well. I think most of my trouble has been operator error. No more beer for you- Seinfeld

Fuselage, Part 4

Much progress has been made on the fuselage. I realize this is a long build; much like the wings, I look at the instructions and see what I have accomplished and what I have left to go, and just gain a little more respect for all those who have gone before. I keep telling myself there are over a thousand flying, and at least one that has flown around the world. Thanks to all those trailblazers.

The fuse continues with the center section assembly. Much of it to plans, but the crotch belt hold downs were an update that is not explicitly called out in the instructions. I decided to do this while installing the ribs. This allowed me to use solid rivets. I also had to use the 90 degree drill adapter and a 12" #30 bit. I was able to use solid rivets due to my doing this as the center section was assembled. (The separate instructions assume a retrofit and used pulled rivets.) 

Riveting the center section had its difficult moments. It took some effort to get to the rivets for the center ribs and the center-rear bulkhead. If I was to do this again, I would start with the most central ribs and rivet from the center to the outside squeezing the rear and crotch belt supports, and using the rivet gun for the very front.

Once the ribs were in, I turned it up on the edge of the bench and most of the skin rivets were easy with my awesome helper holding the bar. I had to remove the control column brackets and 2 of the 4 seat belt anchors to get access.

To me it was not clear when to dress the R-915 side ribs. I did those after the structure and skin were riveted on and this worked out well. These must be fluted to match the curve of the side skins. I was able to use the prepunched holes and the seat floor edge to judge the fluting. They came out well.

After all this fun, here is the milestone shot. The one that shows real progress is being made. (At least until it comes time to take it apart to deburr and dimple.)

I realize I did not install the optional AHDRS mount in the aft fuselage. I am thinking I am going to put it up front to avoid more wires and tubing going through the center section. That is my story and I am sticking to it. ;-)

Fuse, part 3

So I am working on the aft fuselage. Like many others, I had trouble with the F779 bottom fuse skin at the rear. This is really thick and pre bent. Well sort of.  I had trouble getting the prepunched holes to lie up between the F779 and the bulkheads F710, F711, and F712. I was determined to have these pieces fit without inviting my neighbor, Mr Armstrong, to come over. Finally got it all lined up.

The trick was tweaking F779. First I made a jig to get the sides bent more by hitting it with a rubber mallet on the end; I tried using a piece of pipe on the bends, but this didn't do much. Then I used the rolling trick from the rudder build to finish bending the curve to 90 degrees. The metal has a lot of spring back, so I couldn't due this by hand. Everything fits well now.

Fuse, part 2 of many

Bending longerons. Those words create fear, at least they did for me. I don't care to beat things with hammers, so I borrowed some longeron bending dies. I added scotch tape to the longerons and spread a thin coat of biolube from the aviation isle of  REI. I didn't have a good vise, so I used c-clamps and the old wing crate as a table. I taped the plan's template to the side of the crate. This worked out well.

Using the c clamps, I did the first pass moving the dies about 1 1/2" at a time. For the first longeron I had help and it went well with very little out of plane bending, but I went thru 12 "el cheapo" c-clamps. For the second longeron, I bought three drop forged c clamps. These are still usable afterwards so worked out better. The rear bend is actually much tighter than the rest, so I had to use three pieces of 1/64" model airplane ply to increase the bend radius of the die.

The second longeron bent easier using the better c clamps, but I had much more out of plane bending. Using some scrap wood and a 2" piece of drain pipe, I was able to roll the bend back into plane. Both are well with the 1/16" tolerance.

Fuse, part 1

In looking at various build logs of others who have gone before, it seems the fuse takes just as long as the tail and wings combined. So I decided to use a gifted surplus Hobbs meter to keep track of my build time. Now I am depressed; my per week build time is no where near what I expected. So I have abandoned the Hobbs and am just trying to spend any free time on the plane. Anyone want to come by and paint a house while I build?

The big decision was whether to paint the interior pieces that show at this time. After much hemming and hawing, I have taken other's advice and decided to prime everything as I go and then re-prime and paint once the fuse is together. The crevices in seat back brackets will be hard to get to once assembled, so I will leave those cleco'd for now; those will end up having exposed rivets. This plan prevents me from having to worry about scuffing the paint during the build.

So the fuselage bulkheads are ready for assembly. The decision to prime did not add too much work, but it did add confusion. The various steps to prep the bulkheads had to be stopped while I built up a stack of parts to prime. This priming session was a long one, but went fairly quick.

Lawn Art:

 

Roadie Box

So the wings are done, but how to store them? So I decided to use the pieces of excellent wood from the shipping crates to modify the gifted wing stand and build a roadie box. This will store the wings and prevent any hangar rash. Here is a picture before the top and ends were attached. Like everything else I thought this would be a 1 day project, but alas, it took me a while longer.

Wings..done

Wings are done. Took me 13 months, but I am happy with the results. A big thank you to all those who helped. Now I need to remove the blue plastic and build a roadie box for long term storage. Yeah!

I will add the tips and avionics during the finishing stages; its too early to buy the avionics.

Here is a picture of the pitot and AoA tubes. I just heated them up and slide them on. The metal tube was prepared by plugging the tubing to keep the curd out, rounding the end, abrading the last 1/2" so the plastic tube would stick better, then removing the temporary plugs. Also visible is the bracket to hold the conduit away from the access cover screws.

Wings - It Is the Little Things

It is the little things that take the time, but these little things seem to be less stressful. Let me explain. I was stressing about finishing up the trailing edge of the flaps. So stressed that I went ahead and installed the Garmin autopilot roll servo while I worked up the nerve.

I originally laid out the wiring to have the roll servo in the left wing. Then I read the instructions and realized it goes in the right wing. So I redid my wing wiring diagram and followed directions for the installation. 

Today I got up the nerve to tackle the trailing edge riveting. I had prosealed the trailing edge last week and left it clecoed to the building table to dry. When I pried it loose from the table this morning, I was surprised that the trailing edge was dead straight. I could not see any warpage at all. Amazing considering this thing is, like, seven feet long. OMG.

The riveting was non eventful although I did deviate from the instructions a little. The instructions say to do the bottom of the trailing edge rivets half way and then flip the flap over and do the rivets the rest of the way from the top side. But with the flaps, the flap attachment brackets stick down and I felt it would be nearly impossible to keep the flap flat and true. So I did all the rivet setting from the bottom making sure to keep the flap absolutely flat throughout the process. In a little over an hour, both flaps were done. Easy peasy.  Installing them was straight forward as Sponge Bob watched.

I riveted the aileron push rods, but I think it is best to weld these per the optional note on the plans. The rivets near the aileron side come very close to interfering with the spar hole. At the extreme travel, I could see where this could cause some binding. These rods will be modified and welded while the wings are in storage.

Below are my bushings and top bolt lengths, for reference.  A lot of fiddling, but nothing too difficult or confusing. I measured the travel at 19 degrees down and 31 degrees up. This should be sufficient. 

Here is my build table for the flaps and ailerons. Not sure if I am going to give this away or re-purpose it for a fuselage cart.

I expect to have the wiring and pitot lines installed this week. I am looking forward to riveting the bottom skins on.

Flaps

Moving on to the flaps.
It is after New Years and I still have a little bit left on the wings, namely the flaps and the internal mechanisms.

The normal match drilling and bracket fabrication went as per the instructions, no drama there. The spar is countersunk for AD3 size rivets. The normal method is to go 0.007" deeper to have the spar dimple mesh better with the skin's dimple. However this spar is barely 0.040" thick and this would have enlarge the holes in the spar, so I only went 0.002" deeper.
 I primed and painted  the inside of the flap bracket prior to assembly; I didn't feel this could get painted by the painters once assembled. I also painted the edges of the spacer. When riveting together I found some old hobby spruce that fit very well as a spacer when clamped in the vise.


















When bucking the spar to skin rivets, I used a scrap piece of thin plywood to protect the spar. The plans call out  AD3-3.5 rivets but these are just barely long enough. I used -3.5's on the top spar to skin because these were easy to set and easy to get a precise smash down within spec. However, for the bottom skin to the spar, I used AD3-4's. The extra length made it easy to set within spec without having to really worry about get it exact; these rivet are set blind so are hard to inspect and harder to gauge when being driven. Using the longer rivets and having previously set the spar countersink depth at the low end, the riveting came out nice.

 

I used tape to hold open the skins while riveting the skins. This helped, but it was too easy to open the skins too wide and create a gap between the skins and the spar.

 

 All that is left is pro-sealing the trailing edges and trailing edge riveting.