Wing Walk and some test photos.

I started modifying the L/H wing to reinforce the leading edge so I could add a wing walk. The redesign was pretty straightforward. I removed the existing wing skin with my multi-tool. That thing zipped right through the fiberglass. After the skin was removed, I reinforced the foam ribs with a ply of 8 OZ fiberglass on each face of the exposed ribs.

lateral stiffeners

I then slotted the ribs every 2 inches and inserted a wooden stringer. the Stringer was sized to react 250 lbs between the farthest span (6") so basically each stringer can support the weight of one step. In reality the load will be distributed between at least 3 members. The stringers were potted in with micro balloon and epoxy. Using the leading edge lay up mold, I laid up a 2 ply skin of .012 thick carbon fiber.

leading edge walkway skin

2 ply's of graphite and a single lightweight ply of glass comprise the walkway skin. The leading edge was taper sanded  to allow blending into the existing skin.


Right now the skin is curing after having been bonded 8 hours ago. Tomorrow I will be able to flip the wing over and finish sanding the skin in preparation for covering. I should be able to finish the covering tomorrow.

rib stitching

My airfoil is a Worttman 170 low speed laminar flow airfoil. It has a reflexed trailing edge on the upper and lower surface. Because of this, the fabric tension after shrinking will try to pop off the reverse curve surface. So I elected to rib stitch the trailing edge where the reflex is. Everywhere else on the wing, the fabric is bonded.

wing re test

The original wing test spar has been sitting out in the weather for over 2 years. The ultra violet radiation has attached the foam and the fiber glass. Periodically I retest the wing. The original wing was rebuilt after initial destruction testing and re mounted to the back side of my test stand. A 2 x 10 wood extension was added to increase the applied moment such that it equals the actual moment on the wing. This is a little conservative because the wood does not deflect similar to the wing. Because of this the stress is concentrated more toward the root, there is no relief that would normally occur it the complete wing was allowed to deflect.

anyway, this is a picture of the wing at just a little over limit load. There is 1200 lbs of force being applied. In the previous picture you can see my load cell that I designed. I made a piston with exactly 1 inch of area. I then bored a cylinder out of some scrap aluminum.I drilled and tapped into the cylinder and installed a 3000 psi pressure gauge. I filled the void with transmission fluid. The actual load now is a one to one read out. I calibrated the load cell at work on a universal testing machine one day at lunch. There is a little hysteresis error, but that was under 100 lbs. Close enough!!!