Budget building: how to edge-glue balsa

Mar 21, 2013 12 Comments by

At some point in your model-building career, you will be faced with a problem.  You will have an area of your model that requires a sheet of balsa wider than the material you have on hand.  If you are like me, this usually happens when you are starting to make significant progress and when the local hobby shop is closed for the evening!  Let’s say additionally you need a sheet of balsa that is 10 inches wide (sheeting a wing for example) and the local hobby shop only stocks 6 inch wide sheets.  Even if the hobby shop is open, it seems you are out of luck.  Another factor with wider balsa sheets is cost.  It would seem that the cost per width of balsa sheet should be pro-rated but that isn’t so.  One online resource lists 3×1/16-inch balsa sheet for $.90 per sheet, so a 12-inch-wide sheet of balsa should cost $3.60.  Try $10.23!  What’s a modeler to do?  That’s right, we edge-glue sheet balsa to make the size sheet that we need!

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The easiest technique I have found was learnt from Randy Randolph’s column right here in Model Airplane News.  I have used it many times and the result is a strong, nearly seamless joint.  With this technique, you can theoretically make balsa sheets as wide as you like, only limited by the degree to which you’d like to become a benefactor of Ecuador.

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Step 1:  True your sheets
It would seem that sheet wood from the factory should have a very “true” edge, meaning it should be perfectly straight along its border.  There are a number of reasons that this doesn’t happen.  If you lay the sheets flat and they are perfectly congruent along their edge, you can skip this step but I’d wager the farm that your sheets aren’t true.  The 3/32-inch sheet I laminated had nearly a 3/32-inch gap mid-sheet due to untrue edges.  Take a long straightedge (I used an aluminum framing square) and cut the mating edges true.  Make sure your blade is vertical when cutting.

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Step 2:  Tape sheets together
Lay the sheets flat on your building board.  Approximate the edges you have just “trued” and hold the sheets together.  I find it helpful to pin and/or weigh down the sheets to keep them pressed together.  Check that the edges are pressed tightly together along the length of the seam.  Tape the seam together along its entire length with masking tape and turn the sheets over.  The seam should be held tight by the tape.

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Step 3:  Glue
The glue used is a matter of preference.  I used thin Zap but others may prefer Titebond as the seam will be a bit easier to sand afterward.  Gently fold the seam back to open it slightly on the side opposite the tape.  Lay a thin bead of glue along the seam, and place the glued sheet tape side up on your building board.  Use a sheet of wax paper under the balsa otherwise you’ll have a bugger of a time getting the sheet unstuck from the building board.  Weigh or pin down the sheet while the glue dries.  Remove the tape, sand the seam, and resume your build!

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This technique is a little more work than buying sheets that are already the dimension needed, but the savings in the hobby budget will allow you spend those dollars on other things.  Be frugal and edge-glue! BY SCOTT COPELAND

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12 Responses to “Budget building: how to edge-glue balsa”

  1. Alex Guzman says:

    My way to get two nice and straightedge is by sanding each one and for that I made one laminated board with one aluminum angle in one edge with sanding paper and one aluminum angle that help me to hold the piece of balsa during the swing-sanding process, with this way you can correct any edge and the wood will keep this shape.

  2. Alton says:

    Been doing this for 45yrs!!!!! Nothing new!

  3. Sig Seemann says:

    Scott: In working with two long sheets of balsa, how to you keep the glue from drying at the beginning to the glue joint before before you reach the end, then flatten and butt end the to two sheets and flip them over–all before the CA drys?

  4. bigglesbazy says:

    Good tip, thanks

  5. John Sohm says:

    There’s all kinds of ways to do this task, all basically the same if you look deep. I’ve been using Dave Platt’s method since I got his first series of Black Art VHS tapes back in the early 90′s and I still use use that method to this day as it works very well.

    True up the edges, lay side by side as they will be assembled, lightly sand the two sheets, hold together and using thin CA tack glue in several places then you can run a bead the entire length as you press down the sheets. When done, sand both sides and you’re done.

    No waiting for glue to dry, no worries that glue set before you get pieces together, it’s ready when you finish sanding it. Just remember, do place a piece of wax paper under sheets before gluing.

  6. Scott Copeland says:

    Alex- I like your idea! That certainly makes a lot of sense if you will be doing this frequently.
    -Scott

  7. Scott Copeland says:

    Alton- I know this is nothing new, and I’m not claiming this is “my” technique. Some readers are new to the hobby and may never have done this before. We all had to learn from somewhere so I put together this “How-To” for their benefit.
    -Scott

  8. Scott Copeland says:

    Hi Sig-
    Like the 4th picture shows, the seam is opened held on the opposite side by the masking tape. If you use medium Zap-A-Gap or slow Zap, the glue won’t dry during the process. Once you run a bead of glue along the seam, place the sheet wood glue side down (tape side up) on your building board and weight it down for a minute or two. The whole procedure probably takes less than 30 seconds. I hope that answers your question.
    -Scott

  9. Scott Copeland says:

    bigglesbazy- Thanks for the compliment!
    -Scott

  10. Scott Copeland says:

    John- Great tip! I have learned a tremendous amount from Dave over the years and I trust all of his techniques work extremely well. Thanks!
    -Scott

  11. Bill says:

    Keep up the good work Scott and don’t pay attention to people like Alton. No matter what hobby you select there will always be an Alton in the wood pile.

  12. tom P says:

    I like to put the tape side down and squeegee off the excess with an expired credit card.
    I also pretape accross the gap with 6 or so pieces stretching the tape slightly.
    That makes the gap tight and the sanding minimal.

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