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Thursday, June 25, 2015

Nose and nose gear - part 26

Strut outer cover (13.8 hrs)

You are not going to find the “strut outer cover” anywhere in the plans. As a matter of fact I made up the name as I was writing this post. 

So, what is it?

Well, it is definitely not my idea. 

I am actually borrowing the concept from my friend Beasley, as I am trying to recreate his beautiful gear doors. Where did he get the idea, I don’t know, but he’s a very creative guy, so if he didn't come up with it himself, I'm sure he probably improved on the design.

Anyway, the idea behind the nose gear covers is to try to seal the nose compartment as much as possible, helping to prevent cold air infiltration that could affect the pilot’s legs at altitude (especially during winter), and improve aerodynamics a little.

Most Long EZs have the nose gear strut exposed and flush with the bottom nose skin, but my strut retracts further into the nose than normal, leaving an open slot that I will now try to backfill with foam and fiberglass. And while we are an the subject of foam, today’s story begins with finding enough of it to fill the gap.

Getting some foam to fit the channel

Countersinking some room for NG3

Foam glued to nose gear leg with 5 minutes epoxy

Note the wedge-like foam shape after sanding it flush to the fuselage bottom

I decided to add three BID plies in front of the strut (as seen when extended), and two behind it, sandwiching the leg. One thing to keep in mind is the need to leave enough room for these last two plies below the front three when doing the first layup (with the gear retracted). Failure to account for this could prevent the gear from retracting completely, and perhaps bend the outer strut cover, or even break it.

It turns out that two plies of BID are about as thick as four plies of duct tape.

2 cured plies of BID equal 0.023" (0.58 mm)

4 plies of duct tape equal 0.022" (0.56 mm)

With this in mind, I padded the area where the front layup would rest with four extra layers of duct tape, then I closed all gaps with the wheel well with Plastalina.

4 extra plies of duct tape added to both sides the foam

After cutting the fiberglass, and applying it to the foam, it was off to curing.

I used 3 plies of BID for the front side of the leg cover

"Sleeping beauty"

The next day I used a ruler to help me make straight cuts, and leave the cover about 3” (7.6 cm) wide.

Carefully trimming the new cover to size

Gear leg sporting the new cover (front part only)

The Plastalina was its usual pain in the neck to clean up, after which I trimmed the foam flush with the gear leg, and gave it all a good sanding.

Lot of cleanup to do on the back side

Plastalina removed, fiberglass sanded, foam getting trimmed.

All that was left to do was to prepare the two remaining BID plies, add a flox fillet to all 90˚ corners, apply the glass to the gear leg, and let cure.

2 BID plies getting wet

Same 2 plies in position after cutting a pass through hole for NG3 & 4

Letting it rest till the next day

The overnight wait was rough, all I could do was think about whether this leg would fit in its well once again or not, but you won't have to wait, you are going to find out right now.

So, did it fit?

Well… no, not really.

It kind of fit, but it wouldn’t close all the way, leaving a gap between the back side of the strut cover and the fuselage bottom, mostly on the strut end closer to the wheel.

This gap didn't exist before glassing the backside of the strut cover

Apparently the extra 2 plies of BID and the flox transition had swelled up the leg enough to create some tight spots. In some places the unwanted contact was was pretty evident, in others I had to use carbon paper to highlight the issue.

Carbon paper

Face down, the carbon paper is leaving a mark on the strut cover (SC)

Carbon deposits highlight area where rubbing occurs

Carbon transfer on the gear leg after turning the paper around

No need for carbon paper here, it's pretty obvious where the problem was.

More issues

Carbon = problem

The final check was done by slipping a feeler gauge between the gear leg and the strut cover (SC), and sliding it along the length of the strut while feeling for resistance, then sand as needed.

Feeler gauge would stick between the black marks

This process was very time consuming, but in the end it yielded good results, and I was happy with the outcome.

Gap is gone!

Testing the fit of the new strut cover

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