Center section spar - part 14

LWAs and layup #7 (8.0 hrs)

Front face of center-section spar not glassed yet

Before skinning the front face of the spar, there were still a few items to finish up on the back side, namely the wing attachment points LWA2 and 3, and layup #7 over the top of them.

I didn’t want to take a chance with the aluminum plates sliding out of position again, so I decided to flox them, and let them cure in place overnight before moving on to fiberglassing.

Floxing LWA3

With the fiberglass already cured, the weighted aluminum tabs would no longer slide out of position.

LWA2 getting the same treatment

LWA2 

This step is a lot easier to accomplish with layup#6 cured

I begun the next day by measuring and cutting the UNI and BID necessary for layup #7.

CS spar ready to go

Staggered UNI and BID cutting plan (all the above must be doubled)

This is when saving glass scraps comes in handy

All layup #7 fiberglass cut

Marking plastic sheet for pre-preg

Just add epoxy and peel plastic off

I then marked the UNI and BID layups from step 9 on the spar itself.

Outlines of where UNI and BID should go

After mixing up some flox, I created some nice fillets around the plates for the fiberglass, and also wetted the spar with pure epoxy anywhere BID or UNI would go.

Flox fillet around LWA2

Working on a flox fillet around LWA3 sharp edges

Pure epoxy painted within the marked boundaries

Pre-wetting the spar to help the next fiberglass layup stick better

I finally poured epoxy on the ready to go UNI pre-preg strips, then laid them on the spar.

Pre-preg UNI is finally getting wet

Pre-pregged UNI strips ready to peel and use like Band-Aids

Peel-ply in use over LWA2

Peel-ply over LWA3

Lastly, I applied the BID over the plates, and peel-plied all edges.

BID single layer over LWA3

Same thing after wetting with epoxy

BID over LWA2

Using a small plastic sheet over LWA2 to squeegee air bubbles out

All edges peel-plied

Putting layup #7 to bed for the night

After another overnight curing cycle at 80ºF, I ripped off the peel-ply, and sanded off the loose peel-ply strands.

LWA2

LWA3

Spar ready to move on to final wrapping