Main landing gear - part 1

She's got legs... (16.2 hrs)

Welcome to the landing gear construction page, where you’ll be a witness to how I turned the basic fiberglass structure into a landing gear.

Let me first introduce you to the basic components, the main gear bow, and the nose gear strut.

Main gear weighs 22 lbs

A bit dorky I know, but since the FAA will want to see pictures of me during the construction process (in order to prove I actually built this thing), you’ll have to suffer through a few bad photos of me as well.

I will focus on the main gear today, and leave the nose strut for a later date.

Let me answer a few questions up front... 

• No, I did not build the bow, I bought it from FeatherLite. 

• No, they don’t have a website, these guys are old school, and they have been making the gear for nearly 30 years. 

• Nope, no one else makes the gear and it would be too big a project for me to make just one. 

• Yes, this is a major choke point in the supply chain, and you have to order it as soon as you can, because it takes a long time to make.

• Yes it is expensive. $730 shipped for both gears.

As received, the gear still needs a lot of attention though, and the first step is to sand the shine off of it, because more UNI is in its future.

The table top worked quite well holding the gear bow for sanding

That was easier said than done though. Sanding cured fiberglass is very difficult, and I was having a hard time making progress.

This step was too slow, and too painful.

Thirty minutes later, I knew this wasn’t going to end well for me and, suppressing the purist in me, I enlisted mechanized help.

This is the way to go... carefully!

I felt very guilty about this choice, for about one second. The truth is that in the next thirty minutes I was nearly finished sanding. The sander worked out great, and the vacuum did an excellent job sucking up all the tiny strands of itch producing fiberglass.

Contraption holding gear bow like a Texas long horn hood ornament

Less than an hour later I was already planning my next step.

The main gear bow needs to be completely enclosed within 8 layers of crisscrossing UNI, 4 of them applied from the trailing edge, and 4 from the leading edge. Because the gear bow is so long, the layup is split into two sessions, one per leg, for a total of 16 smaller plies.

The big idea

Gear bow cross-section

These plies are cut at a 30˚ bias from a 38” (97 cm) wide UNI roll.

Fiberglass cutting plan

Cutting the glass

Measuring and cutting the strips of UNI took a long time, but eventually I had them stacked up and ready to go.

3 lbs (1.4 kg) of fiberglass will require 3 lbs of epoxy

The important thing to remember at this point, is to flip over every other ply, to make sure the threads crisscross.

With the table cleared up, I put 3 screws into the top, mixed some 5 minutes epoxy with flox, put little dabs of it on the head of the screws, and attached the gear to the screws. This is done to elevate the gear bow off the table, in order to better apply the UNI in the next step.

Gear bow epoxied to screws

These plies of bid are so big that merely handling them is quite a challenge, so I decided to pre-preg them, to make my life easier.

a full cup of epoxy (0.78 lbs, 350 gr) wetting 350 grams of fiberglass (4 plies)

Plastic sheet folded over the fiberglass

Epoxy squeegeed over the fiberglass (between plastic) 

Pre-pregging fiberglass packages your layup into a big Band-Aid, which is then applied where needed after removal of one side of the plastic.

Preparing the gear bow by wetting it with pure epoxy

Pre-pregged 4 plies layup applied to gear bow (bottom plastic removed)

At this point the top plastic sheet is also removed, the glass is then trimmed, and smoothed out.

Top plastic removed, fiberglass trimmed, and smoothed.

The next layup will butt (not overlap) in the middle of the gear

Because another 4 ply layup will straddle this one from the front side, I decided to peel-ply the gear leg. However, this turned out to be unnecessary, since I ended up sanding the whole gear down later.

Peel-ply added to the layup

Top side view

At this point my next door neighbor Phil, an F18 driver, wandered into my shop, and was promptly put to work pre-pregging fiberglass for the other gear leg.

Unsuspecting neighbor trapped in the house of horrors!

The fiberglass was again applied to the gear bow, and peel-plied.

Two layups finished (two more to go)

Left to cure overnight

The next morning the fiberglass had hardened up, so I knocked the bow off the screws with a mallet, and started cutting the excess glass off.

Looking a bit rough prior to sanding

Unfortunately, when I removed the peel-ply it left all kinds of nasty strands, so I decided to sand them off, making the peel-plying an exercise in futility.

Annoying strands left by peel-ply

Once again, I carefully used the power sander to remove all the leftover strands, as well as to feather the front side fiberglass edge, in order not to have a bump there later.

Rear fiberglass gear bow wrap completed (front is next)

The yellow hue on the front edge is the original gear bow glass, awaiting the front layup.