Disclaimer

This blog is for entertainment purposes only, and is not meant to teach you how to build anything. The author is not responsible for any accident, injury, or loss that occurs as a result of reading this blog. Read this blog at your own risk.

Tuesday, October 27, 2015

Center section spar - part 7

Closing the box (7.0 hrs)

Before I closed of the center-section spar by microing a lid over the top of it, there was still one thing I needed to do. 

You see, the spar has additional ancillary functions beside connecting wings, fuselage, and engine together. It doubles as storage compartment, and as an avenue for fuselage wiring to reach the far end of the wings. This last function is what I'll address.

I will be able to drill entry and exit holes into the spar at any time during construction, but what will be hard to do later on is cutting holes through the inner bulkheads. Such task is nearly trivial at this stage, so I took care of it now.


Opening up a hole into CS7 inner bulkhead for wiring

I used a 1" (2.5 cm) spade

Same thing happening to CS6

The edges of this hole are pretty sharp

I worried about the wires chafing on the glass edges

I chose to do a flox corner to provide better wiring support. I started by removing the foam.

Those holes were tough to get to, so I improvised this foam removing tool made out of folded sandpaper.

The idea was to remove foam and micro from the inner walls of the bulkhead
This little tool worked flawlessly

I filled the gaps with flox, then made a small flox ramp in front of the holes.

The idea was for the ramp to help guide the wires straight into the hole later on.

This is the ramp after curing and a little sanding

I fed a few wires along the back wall, and all easily found their way into the hole. Perfect!


With this small but important task accomplished, it was time to close the lid to this box.


I marked the bulkhead location on the inside of the lid

Then sanded the glass rough.

Running very low on micro-balloons, I opted for another flox corner on the bulkheads.

Good thing I did, because the last few joints had to get micro mixed with flox.

Flox corner on CS7 ready to go

Same thing on CS6

Using up the last of my micro (I really thought I had another bag of it somewhere!)

I used nails to prevent the lids from sliding overnight

Nails, I had a lot of, more micro is what I needed.

Last time anyone will ever see CS7...

... and CS6

That is actually micro/flox mix

At this point I just wanted to get it done.

There you go... done!

This box will have to sit a few days for the micro to dry, before getting out of the jig.

Getting some help from gravity

Just about all the heavy thing I could find got to ride the spar

Finally, there she is! Out of the jig for the first time. Her daddy is so proud ;-)





Sunday, October 25, 2015

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!