Williams County Airport, Box 488
Bryan, Ohio, 43506



After caps are cut and straightened according to instructions, draw the following:

1.   Box spar centerline. 
2.   "I" beam shear web line (front face)
3.   Rivet lines

Make sure that box spar centerline and I beam shear web line are on continuous straight line before starting spar assembly.  Hammering the edge of the cap will be necessary to accomplish this step as outlined in the HP-14 Instruction Sheet No. 2, "Cutting and Finishing the Spar Caps".

Consult drawing for proper hole locations and drill spar caps with a No. 41 drill using a hardened drill guide.  The drill guide is important as it is used again later to pick up the same holes when drilling through the skin into the spar.

Be sure also that spar caps in each wing panel are matched in width, are straight, and have their original extruded edges facing the same direction.

Place extrusions on a long table, plank or saw horses.  Put the first inboard shear web in position with web horizontal and flanges up.  Place steel bars or short wooden pieces cross ways under the assembly to give flat surfaces on which web and two extruded plate edges can be aligned.  Drill web through cap holes every six inches and Cleco.  Note that these assembly holes fall in between the one-inch-spaced skin-attach holes.

Put other inboard shear web in place, drill and Cleco.  Use a straight-edge across the top of the spar and hold web up against straight-edge with thin metal strips, one inch wide, having a short 90 degree bent leg which is inserted between web flanges and extrusions.

Repeat the above procedure for the two outboard webs in the box section of the spar.  Make sure that the spar caps are perfectly straight and that the ends of the web are properly trimmed to make a good contact butt joint.

Double-check straightness of spar caps and tight fit of ends before drilling holes.

Install outer I-beam shear webs in the same manner.

It is recommended that strings be stretched on the outside of both caps to double-check spar straightness during the entire assembly operation.


Second edition
LO 12-28-66