Mulliken's Sequoia Falco F.8L

Aligning fuselage frame #3

This frame is glued to the front face of the forward wing spar.  Since this spar also carries one end of the landing gear pivot shaft, I've clamped the forward spar to the main spar using the landing gear pivot hardware for alignment.  Next, I leveled the main wing spar, and checked for vertical on the #4 fuselage frame center line, since that frame is now glued to the main spar.  Finally, I attached a plumb bob at the center line on the top of frame #3, and clamped the frame in place with the plumb bob over the front spar centerline after making sure that centerline matches the spar centerlines.

After double-checking all of this, I'll drill holes for dowel alignment pins so all of this can be unclamped and reclamped for gluing.  Also, there is a cavity between the frame and spar that needs to be varnished.

The gray metal gadget is a drill guide to assist in getting the dowel alignment pins square.

The view here is from aft.  You might wonder why the forward spar is clamped behind the main spar.  It's just that this turns out to be a convenient arrangement for aligning the landing gear hardware, and everything else is relative to the gear.  There's no chance I'll forget to put the front spar in front eventually.

The #3 frame carries the base of the windshield.

 

Mating the #4 fuselage frame to the main wing spar

Hooray for the shortest day of the year!

The first task was to lay out and cut the notches for the fuselage longerons in the fuselage frame.  I made a master template for this that can be used with all the other frames.

The #4 frame is the largest of the frames. It forms the "roll-bar" of the cockpit, and supports the canopy latch.  It is fastened with glue to the front face of the main wing spar.  It is an important glue joint, as it provides a lot of strength in mating the fuselage to the wing.  It needs to be positioned with accuracy.  For this job, I removed the spar from the jig.  Three holes will need to be drilled through this assembly for the gear retraction gearbox.

  The Christmas lights are not permanent, only seasonal!

In preparation for attaching frame #4, the wing spar needed to be trimmed to close to its final dimensions.  These were determined from templates I made from plywood for transferring the rib chord lines to the spar.  The trim lines could then be placed by measurement from the chord line (a chord line is a bit like a center line, but its not in the center of anything, more like a free spirit).  The gap between the try-square and the wood shows the taper that the top surface of the wing will have.  When you multiply this cross section by a 27' wing spar, it amounts to about 2 gallons of wood shavings.  For this task, I purchased an electric hand-held planer, which made the task easy.  The angel is taking a good look at my work, so as to report to my guardian.

Happy Holidays everyone!

 

Wing jig

Time to build the wing.  The first step is to build a jig for it.  The wing is built in a vertical position, with the leading edge up.  Since the fuselage is attached to the wing, the center section of the fuselage is part of the jig.  In the photo, the horizontal slots in the center section will hold the fuselage frames.

In addition to supporting the ends of the wing spar, the endpieces establish the angle of the ribs with reference to the horizontal, or 0 degree angle of attack.  The wing chord line is marked on the jig endpiece, and will be matched up with the rib chord line when the end rib is installed.  It also locates the strings that will be stretched along the leading and trailing edges.  This photo is blurry, but the wing chord line appears at the top of the "window" in the center.

The wing spar supports were leveled with a water level.  The "horizontal reference lines" for each piece were positioned with plumb bobs.  Because the wing is in a vertical position, 'horizontal' is vertical here.  The end pieces are braced with wires and turnbuckles.  The center piece is braced with a diagonal 2 x 4.

Yes, I've moved to the big shop.  Aligning the jig is too difficult where a wall intervenes.  Besides, to work on the other end, I'd have to pull the whole thing out and turn it 180 degrees, and reposition it, with a lot of adjustments to assure level and plumb.  The main disadvantage to this shop is I can't control humidity.  But for attaching ribs, this is not an issue.  I'll be working on ribs for a long time.

The jig is on a plywood and 2 x 6 framework that can be skidded around if need be.