Friday, November 30, 2007

Horz stab skinning

Build hours: 315

The UCA tail is now hanging from the rafters waiting for the lexan inspection plates to be installed before final closure. The UCB tail is installed and drilled awaiting cleanup, and inspection holes. The UCB tail has taken half the time and a fourth of the struggle to complete since we have the experience from UCA! A few steps in the manual could have made it all a lot more painless. I do not recommend building the tail on the plane but the alternatives suck too.
The clamps pictured below are cheap and easy and greatly simplify the skin installation. Some light spring clamps on the trailing edge will hold until the skin is positioned.

Here are five items to watch for when constructing the tail -
spar level
correct incidence
inboard edge fit
outboard edge square
spar pucker
Check each item and often during the fitting.

Plan note:
The basic steps (which the kit guide doesn't mention, (falls under - should have prior building experience)) are:

1) Mark all flange centerlines before assembling the spars and ribs on the fuselage. Extend the forward spar centerline onto the fuselage and onto the outside of the outboard rib.
2) Install the rough cut skin as pictured and clamp. (Check the 5 items).
3) Use a guide to create the fuselage trim line

4) Remove the skin and trim the fuselage line.

5) Reinstall the skin (Check the 5 items). Mark the ends of the forward spar on the skin. Mark the trailing edge trim line. Mark the outboard rib trim line.

6) Remove the skin. Trim the trailing edge and outboard edge. Mark the spar rivet lines top and bottom, front and rear. Mark the rivet pattern on the inboard rib. Measure and record the distance from the inboard rib rivet to the fuselage and record it on the fuselage.

7) Reinstall the skin (Check the 5 items) . Mark the inboard rib rivet pattern using the recorded distances.

8) Drill and cleco several inboard rib holes top and bottom (Check the 5 items).

9) Push or pull the forward spar to align the flange line and procede to drill every 3rd or 4th hole to the tip (Check the 5 items).

10) Mark and drill the top trailing edge (Check the 5 items) and bottom trailing edge every 3rd or 4th hole. Drill the outboard rib top and bottom and then complete all drilling.

11) Go to bed - you've been at this for a long time!

Wednesday, November 21, 2007

Horz stab skinning

Build hours: 297
The UCA stab only needs inspections holes, cleanup and final riveting. The stab skins have taken a surprising amount of work with a lot of attention to plumb, level, square etc. It is also made more difficult by having to build and skin on the plane which requires a lot of inverted work. The actual steps will be documented on UCB.

Friday, November 16, 2007

Horz. Stab Skins

Build hours: 286
Well, a quick post about stab skins. After installing a stab skin, your are qualified to be a one-armed wallpaper hanger. We have not actually completed a skin yet but here's a quick clip on vacuum forming.

Monday, November 12, 2007

Horzizontal Stab Spar

Build hours: 281
The patient has been moved to a clean room environment for appendage attachment.

Actually, we were getting tired of seeing our breath when working in the unheated shop so a 12x16 enclosure was arranged with a 5400W electric heater so that we can work in comfort through the winter months. Each UC will be positioned through the enclosure as needed. The fuselage has been clamped level across the rails so that the stab can be aligned without worrying about the fuselage moving even though we still do a paranoid check regularly:)
The tail spar was built and bolted to the inboard ribs. The 1x2 is used to stiffen the spar in the fore and aft direction while positioning the outboard rib and preparing for the skin. A prop protractor was set for the -3 degree incidence angle and used to check the angle from the inboard to the outboard end.
The plans reference the dimension from bulkhead "F" to the rear of the stab spar as 2 3/4". When ours came out to 3 1/4" we were "concerned". A call to the factory confirmed that the 3 1/4" measurement was correct and that the 2 3/4" measurement was based off of the center of the inboard rib rear bolt hole instead of the bulkhead!
Also, an AN-6A bolt was substituted for the AN-7A bolt called for the rear hole on the inboard rib. The AN-7A would have bottomed in the nutplate without too many additional washers.

Thursday, November 8, 2007

Vertical Stab Dorsal Fins

Build hours: 277
Both dorsal fins have been installed. The steps were posterboard pattern, metal template, vaccuum formed radius, particle board form blocks, flanging, shrinking, drilling, deburring, riveting, ADMIRING!
Some of the rivet stems in our latest batch of Avex rivets have been breaking above the rivet. This may be due to the thinner materials being riveted or inconsistency in the Avex "non-structural" rivets. Either way, when the stem breaks above the rivet, the formed head is opened like flower petals. In the tail area, this has been happening approx. 1 out of every 30 rivets requiring the rivet to be removed and replaced.

After the dorsal fin high, we moved on to kitting the horizontal stab. The outboard ribs were shaped over form blocks with a small amount of shrinking work and all of the spar components were formed up in the break.

Friday, November 2, 2007

More formation flying

Build hours: Who cares!


Going :)

Thursday, November 1, 2007

Vertical stabs completed

Build hours: 272
The top rib and forward spar were positioned. The lightening holes were left out because the weight removed is negligible (see weight calc below), stiffening is minimal and warping during flanging is almost guaranteed!
Weight calc = Holes * pi * radius^2 * thickness * lb/in^3
lbs = 14 * 3.14 * .75 * .75 * .016 * .1
lbs = .04
ounces = .63!

Top rib installed.
Here the skin is clecoed into position for the final riveting. The skin was vacuum formed instead of "carpet formed" as described by Bill Spring and Morry. We hated to break tradition but after seeing the Sonex guys form their wing leading edges on YouTube?? we had to try it. A short video clip will be added later when the horizontal stab skins are made but we had so much fun forming the vertical stab skins that we couldn't stop:)!
The process was - make a rough pattern from poster board, cut out a skin blank, tape the rear edges together, wrap with 4mil plastic, seal one end and stick the shop vac hose in the other and seal. Finally, hit the switch, and before you can say oh crap, the skin is formed and ready for fitting. The process is easy and repeatable.
1) Cut your skins with the grain running in the same direction. The skin is stiffer and will form a different leading edge across the grain than with the grain.
2) The empennage skins do not require a mandrel since the skin stiffness stops the bend with a nice radius.
3) Clamp the skin on the vertical stab spar as plumb and true as possible checking alignment from every angle possible! Then, mark a line approx. 1/8" up on the bottom edge with a guide against the fuselage (just like Norm would do on This Old House:)). This will give the skin a good fit with the least amount of effort.

And here is the final product. The top rib has not been riveted so that the refuge from installation of the dorsal fin (coming next) can be dumped.