Airfield Models - How To

Build an All-Wood Landing Gear for a Model Airplane

December 18, 2021



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Airfield Models (http://www.airfieldmodels.com/)Laying Up a Wood-Composite Landing Gear

I laid up the entire gear in one shot.

I didn't keep track of time while I was doing this but I would say 20 to 30 minutes for the lay-up and then lingering in the shop to make sure I double checked everything before it was too cured to make any corrections.

 
 

Laying Up a Wood-Composite Landing Gear

Resin and other items used to lay up the landing gear. I used 30 minute epoxy laminating resin.  This brand (EZ Lam from Aerospace Composites) has well over 30 minutes working time.  Even though I stopped frequently to take photos I was never in danger of having the resin set up too quickly.

I mixed 60 ml of resin (about 1-1/2 ounces) and had plenty.

This little foam roller is great for applying fiberglass.  It comes with a tray that I threw out after using it the first time because I didn't want to spend a fortune on the solvent needed to clean the tray.  And unlike the ads say, I can't ever get dried resin to peel out of anything cleanly.  I always end up spending a lot of time picking it out so for me disposable is better.

The rollers come in packs of two and cost less than two bucks.

I use a foam plate as a roller tray.

You can also use a squeegee.  Just be careful not to pull the weave of the cloth apart.

The first lamination (the bottom of the gear) receives a liberal coat of resin on the top.  The other side is masked to keep glue from the outer surface.

The one thing about using a roller is it puts a lot of air bubbles in the resin.  If you use a slow enough resin the bubbles will float their way out of the resin.

If you use a roller and the cured resin contains air bubbles then use a slower resin, a less viscous resin or a squeegee.

(In case you're forgotten, ALWAYS test new techniques and finishes on something other than things that you prefer to come out a certain way)

A layer of 8 ounce fiberglass is laid over the blank and more resin is applied.  You can apply resin reasonably liberally.  The excess will be squeezed out when it's all clamped together.
The first blank with the attached fiberglass is put on the form.  Using my high-tech pointy stick (a lead holder with a compass point) I put holes in the glass to insert the pins.
Turn the second layer upside down to coat the underside only.
Place it on the form with the uncoated side up.
Use the upper clamp block to push the blank down.
Remove two of the pins and coat that side with resin.
Replace the pins and coat the other side.
Remove all the pins and add a layer of 2 ounce fiberglass.
Wet out the middle area of the fiberglass.  Replace the pins and then wet out the legs.
Repeat the above steps for all the middle laminations.  Coat the underside of the next blank, put it on the form, coat the top, add the fiberglass, wet it out and repeat.

Above the second to the last lamination goes the second piece of heavier 8 ounce cloth.

Coat the inside of the last plywood lamination with resin and add it to the form.

Again, this is how I laid up the gear for my application.  Yours may need to be lighter or heavier and you may need to do it more than once if you guess wrong.

Begin clamping from the center and work your way out.  Don't tighten the clamps too much at this point.  Snug is good.

At this point you can remove the pins if you like.  I just left them and gave them a quick, sharp twist with vise-grips after the epoxy cured.  The epoxy sheared cleanly from the pins with no damage to the gear.

Work your way around the form adding clamps.  A second person can help by holding the legs to the form while you apply the clamps.

At minimum there should be a clamp on both sides of every bend and if there's room, one (or more) in the middle of each leg.  More clamps are better as long as the weight doesn't twist the form.

When all the clamps are in place go back to the center and further tighten the clamps.  The clamps will loosen as resin squeezes out so check them every ten minutes for about thirty minutes or so.

By the time you're finished the clamps should be applying a lot of pressure to the lay-up.

Allow the gear to set up at least 24 hours.  Longer is better.  Before you even think about taking it all apart check the excess fiberglass and ensure the resin is hard.  That means hard not just mostly firm.

Roast chicken is on sale.  I feel hungry all of the sudden.

Remove the clamps in reverse order.

Woo Hoo!  Captain Morgan is on sale too!

Try to stay focused.

So far so good.
The gear released easily and cleanly from the form.

Before I trimmed the gear, I used my shop vac to pull loose fiberglass strands from around the lay-up so that it wouldn't come loose on its own and float all over my shop.  That made a big difference in clean up.

 
 

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Preparing the Blanks
Trimming the Gear and Adding Axles

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