Center-section spar - part 6

Step 4 at last! (16.4 hours)

Warning: What you are about to see is not exactly as laid out in the plans. If you’d like to know my reasons for changing the layup schedule (slightly), read my previous blog entry. Your life depends on following the plans only, not copying what I am doing here.

I started Step 4 on the right side of the spar (left in the jig) by mixing up some micro slurry and coating the spar inner surfaces. I stopped the slurry treatment before reaching the inner attachment point area, this way I didn’t commit to doing anymore fiberglassing than I had to on day one. 

Since I still wasn’t sure how long would take to do the first section, I planned for one section a day, maybe two, to finish all four areas of the inner spar.

Keeping out of the busy inner bulkhead area

Next, I prepared a plastic bag with some micro, and used it as a pastry bag to create a fillet in all corners.

Micro pastry bag ready to go

A nice micro fillet in all corners

Close up of the bulkhead fillet

Working solo can be a real pain sometimes, especially when handling the large plies of BID of layup #2. I used a bunch of pins to help me hold it where I laid it.

Pins holding up the BID

The bulkhead section could not be straightened out, so I sliced it and overlapped it.

Wetting the glass using the shortened paintbrush worked well, but it took sometime to get the glass straight, and all the air bubbles out, especially at the far end where the glass bunched up like crazy. After trying unsuccessfully to make a round peg fit into a square hole, I ended up slicing it vertically and overlapping the two ends on the bulkhead.

The first section of layup 2 is completed

I'll be working on this end now

With the fist quarter of layup #2 done, I moved on to layup #4, where BID and UNI get together. This turned out being easier to do than to talk about it.

This is the way the next BID ply will have to fold

The BID is in!

I decided to pre-preg the UNI, then lay it in place.

UNI pre-preg

Showing the way the UNI will lay

UNI plies over the BID

The LWA1 aluminum plates had to be floxed with the rounded edge down, and facing the spar corner. I drew arrows on them ahead time in order to avoid confusion, and was careful to make sure their distances from the edge was 0.75” (1.9 cm) per LPC #28.

The inner metal attachment points get floxed. The pins hold the tabs in the proper position momentarily.

One last small layer of BID covered the tabs.

A layer of BID went over the metal tabs

That went pretty fast I thought, until I looked at the clock and found out 4 hours had already gone by.

This first section was completed in about 4 hours

Feeling pretty good, I decided to do another section before  quitting for the day.

Slurrying the second section

Adding the fillet in the corners

BID layup 2 covering the second section

Inner bulkhead and fillet added. Note layup #2 generous overlap area.

Other side of CS7 inner bulkhead

Demoing the BID layup on CS7...

... and the UNI stack.

BID and UNI in place

One more layer of BID on the outer side of CS7

Setting LWA1

LWA1 25" from centerline

LWA1 distance from CS7 set to 1"

Plastic sheet pieces set over the metal tabs

Device holding 10 lbs (5+5) bearing down on the outer tabs...

... and 10 more on the inner tab and a squeegee.

20 lbs (9 kg) spread over 3 tabs and a squeegee (5 lbs each)

Looking at the clock now, I had been working for eight hours non stop, and my lower back was starting to feel it. Oddly enough though, the most discomfort concentrated in my shoulders, no doubt due to the spar sitting high on the table. Oh well, I peel-plied the transition, and went to bed.

I began the next morning by trimming the glass, removing the peel-ply, and doing some light sanding in a few spots. 

Overall things looked good.

Sanding down the sharp hedges

Outer bulkhead CS8 detail

CS8 as seen by CS7

Since day one had worked so well, I repeated the same exact sequence of events on day two.

Day two took 8 more hours of non stop work. There was just no way I could have done Step 4 in one day by myself. I turned the shop’s heater up to 80℉ (27℃), and went to bed hurting in places I didn’t remember having.

After a good night sleep, I woke up and I once again trimmed glass, removed peel-ply, and sanded a few spots, then Step 4 was finally done!