Airfield Models - How To

How to Make Balsa Wood Plywood

May 03, 2015



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Airfield Models (http://www.airfieldmodels.com/)How to Make Your Own Plywood

Commercial plywood is always warped and is available in only a few types.  Working with warped pieces does nothing but make model building more difficult.

In one case, a kit-supplied plywood former was so warped that I actually damaged the structure of the fuselage while attempting to get the former glued in straight and square.  It simply did not want to go into place the way it was supposed to and kept springing back to where it wanted to be.

Eventually I got the former glued in how it should be, but some time later I jolted the fuselage which caused it to explode (yes, really) due to internal stresses of parts that required brute force installation.

I learned some valuable lessons that day one of which is that kits are crap compared to what can be accomplished by scratch building (if I take this concept any farther than I have already, I'll be planting my own balsa and birch trees soon).

This tutorial demonstrates how I make plywood using balsa wood, but I do exactly the same thing to make plywood from aircraft ply.  Plywood can be made from any sheet material that can be laminated.  The end result should actually be flat if properly made.

The point of plywood is to have wood that withstands forces coming from more than one direction unlike regular wood which is weak across the grain.  I use plywood to make various small reinforcements, such as mounting blocks, as well as formers having large cut-outs.

Avoid the use of large slabs of plywood because it is heavy and there is almost always a better method to reinforce larger areas.

Also see

Tools and Materials

  • A hard, flat surface
  • A hard, flat board or piece of glass
  • Weight or clamps
  • Wood to make the plywood
  • Epoxy or polyurethane glue
  • Squeegee
  • Wax Paper
 
 

Making the Plywood

Gather the materials and tools needed.  Cut the wood blanks so that they are large enough in all dimensions.  If you need to edge-join wood then you can simply join them when you laminate the wood together.  This allows you to skip the step of joining the wood and waiting for it to dry.

Squeegee slow-drying epoxy or polyurethane glue on each face.  Remove as much glue as possible to save weight. Use 30 minute epoxy or polyurethane glue such as Gorilla glue.

Pour glue on each face.  Use a squeegee to spread the glue and work the glue into the grain.

Very little glue is needed to make an extremely strong bond.  After the face is thoroughly coated scrape off as much glue as possible.

Note: If you make plywood using aircraft plywood be sure to place concave sides together so that warps oppose each other.  The warp will probably come back later if you stack the parts like bowls.

Wood grain of adjacent pieces of wood should be at 90 degrees. Normally I use two laminations of wood to make my own plywood.  However, you can add as many laminations as you think you'll need.

Arrange the laminations such that the grain is at 90 as shown here.

Note that more laminations will make the part stronger as well as heavier.  Don't go overboard.

Three pieces of 1/16" balsa are laminated to make a piece that is 3/16" thick. In this case I am using 3 laminations of 1/16" balsa to make a former that will be 3/16" thick.

I could have used 2 laminations of 3/32" balsa but I wanted more vertical support for this piece.  This blank will be a former having a very large cut-out.

Place the plywood between sheets of waxed paper and place on a hard, flat surface. Fold a piece of waxed paper in half and place the part in the middle of the fold.

When making smaller pieces I make at least 2 at a time so that I can space them apart.  The space between parts provides better support for the board placed on top which in turn provides more even pressure.

This piece is large enough to be self-supporting so a second piece isn't needed.

Be sure to put the plywood on a hard, flat surface that can handle the clamps or weights.

Obviously you should have confidence that the weight won't break the table.

Cover the plywood with a hard, flat board.  Use weight or clamps to provide a great deal of pressure while the glue dries. Cover the plywood with a flat board and clamp it down.  I often stack up heavy items from around the shop rather than use the clamps.

Tool boxes, more boards, car batteries, socket sets, etc. all provide good weight in compact packages.  Stack up weight until the plywood is under a lot of pressure.

The bare minimum you should allow the glue to dry is 24 hours.  Normally I allow the plywood to remain under pressure until I need it or until it's in my way.  The longer you leave it, the better it will be.

Plywood is an excellent material for making parts that have large cut-outs. The finished former weighs only grams but has the necessary strength to do its job.

Aircraft ply would have been stronger and heavier than necessary and balsa sheet would have been too weak with an opening this large.  Balsa plywood is just right.

OK, so now you're looking at this former and thinking, "That was a lot of effort for a stupid former!"

Yes it was.

You're also thinking, "Man!  That stupid former was really expensive too!"

Yes it was.

Finally, you conclude, "That just wasn't worth it!"

Yes it was.

I try to build the best possible model regardless of the effort or expense.  A lighter, stronger model simply flies better.

By the way, keep the scraps because they make excellent gussets.

 
 

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How to Add Decorative Inlays to a Model Aircraft
How To Repair a Flying Model Aircraft

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Copyright 2004 Paul K. Johnson