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Sunday, October 06, 2013

Main landing gear - part 5

Lower tabs (28.6 hrs)
When the time came to build the fiberglass tabs, Sam, a friend of my daughter's who lives in the neighborhood, stopped by the shop, curious about the weird brown thing growing ever larger on the bench. We hit it off pretty well, so I decided to offer him the opportunity to try working with composites.

Sam and me

Sam is a very talented kid, and a hard worker, and he quickly got up to speed on composites work. I enjoyed working with him over the span of a week, and certainly hope he comes over to get his hands dirty again.

Picking through UNI leftovers

BID squares for the inner side of the tabs

Because of my higher glass count (324 pieces of UNI and BID) we spent the best part of an afternoon cutting fiberglass. Sam did a great job, and time flew by while in good company.

More squares, more cutting...

Sam hard at work

Sam's first pre-preg

The patient was immobilized

Pure epoxy over the sanded fiberglass

Peeling the back plastic off

First 13 layers of fiberglass applied to the gear bow

Remaining plastic being removed

Looking good after all air bubbles were removed

Second 14 layers of UNI being applied over the first

27 additional layers of BID laid over the 27 layers of UNI on the vertical sections only

The BID kept sliding off, so I used peel-ply to tie the BID to the UNI layer of the center section

Work's finally over for the day

Plywood tabs in conjunction with the peel-ply kept the BID layers from sliding off overnight

A few days later I trimmed and drilled the new outer tabs, then I shaped the contour with a sanding block.

Drilling an access hole for the boring tool shaft to pass through

I know it looks weird, but this is what it takes to drill holes that line up.

Boring tool business end

Boring the fiberglass tabs

The holes needed to be enlarged slightly since this boring tool cut 0.020" undersize

Making the outer tabs pretty and round

Well, this tab actually is pretty nice!

Plywood and Bondo will have to be removed next

Later, I got rid of the plywood tabs and the Bondo, and I sanded the inner surfaces to get them ready for when the inner part of the tabs will be built.

"Thank you for your service, but we are downsizing the operation!  You understand..."

A shot of the inner tab surface after sanding

Other side will get the same "Corporate justice"

And there she goes...

The alignment foam reference is kept a little bit longer

I replaced the steel tubes, and realigned the markings I had previously made. I then scribed new markings on the tubes, outside of the tabs, and knocked off the old foam references.

Steel tubes back in the exact original position

New reference line scribed from the outside surface of the fiberglass tab

The right set of inner tabs was done the same way a few days later, but Sam was not around to help, so I had to do them on my own.

Pure epoxy over  the seat of the new tabs

13 + 14 plies applied

Same thing with the plastic removed

27 BID layers added to the outer tabs curing overnight

Morning ritual of peel-ply removal

These tabs are pretty massive!

Plywood tabs are still wrapped with duct tape

Duct tape in the foreground trimmed off with a razor

Same thing, different tab.

Using my vibrating cutter to trim the excess glass

One tab sanded to size, sporting a brand new access hole

Both tabs sanded, and access hole being used.

Mounting hole bored to 5/8" (1.58 cm)

Opposite side view

Eventually both tabs got bored...

... and the plywood and Bondo was chiseled off

With the outer tabs completed, I couldn’t resist putting the gear back on the fuselage to see how it fit, and I was happy to see that the gear bow was solid.

Here are the finished inner tabs (another nearly identical layup will be done on the inside surfaces)

The fit was incredible!

Right tab detail

Left tab detail

Firewall view

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