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Model Airplane Workshop Tips — Laminating Balsa Parts

Model Airplane Workshop Tips — Laminating Balsa Parts

As my online Build-Along for the Sopwith Camel continues, I recently did some lamination work on the top wing, and thought it would make a good How To. This technique has been used for decades but to a new generation of RC model builders might be worth explaining in detail. Here’s how I did.

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There’s nothing exotic about the technique. I use soft A-grade (often referred to as “Contest Grade”) balsa, good old TiteBond yellow wood glue and some Ammonia from the grocery store.

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For the center trailing edge of the top wing, I needed 5 layers of 1/16-inch balsa and I cut strips using a straight edge. The strips are a little wider that the finished height of the wing ribs in that section of the wing.

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Fill the kitchen sink with hot water and then pour in about half of the ammonia in, (that’s about 30 oz. of Ammonia to 2 gallons of water.) Open a window for proper ventilation. Place the strips in the solution and use a handy weight (like a hammer,) to hold the strips submerged for about 2 hours.

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Remove the balsa strips from the sink and wipe with a towel to remove access water/ammonia. The strips will be nice and bendy at this point and I used an old engine cowling to do the first bend. Use some cloth pins and clamp the strips as shown here.

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Don’t use any glue. This bend does not have to exact, it is just the first step. Now let the strips dry overnight.

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Here you see the strips now have a “set” and are still very bendy and flexible. They are also still a little damp but not wet.

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To form the proper shape for your model, use your plans and make a forming block to match. I used 3/4 inch pine and a plywood base board.

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To prevent the glue from sticking, I cover the plywood base and the forming block with Great Planes Plans Protector clear material.

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Now lather up the strips with glue and then stick them all together.

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Start at the center and use nails to “clamp” the strips tightly around the form block. Don’t worry about access glue oozing out. Just wipe it away with a paper towel.

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The important thing is to apply enough pressure with the nails to eliminate any gaps between the strips and between the strips and the forming block. When satisfied, place the whole thing in a warm area and let dry completely. Titebond dries quickly, but I usually leave it for about 2 days to make sure it is completely dried.

That’s it for now. To see how to work with laminated parts and incorporate them into a wing structutre, click the link: http://www.modelairplanenews.com/blog/2014/09/03/workshop-tips-working-with-laminated-parts/

 

 

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12 Comments

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  1. Rather than a tank/bowl/or whatever to put the ammonia in, I found it easier and faster to spray it with a window spray bottle of ammonia. You could dip it but this is fast. Then wrap what you just wet in Saran wrap. You can make up lots of these, they take up no space and they are flexible in less time. I don’t usually reduce the ammonia, just straight.

  2. Spray the wood, of course

  3. This looks good for scratch building! I will give it a go.

  4. Thanks for the showing the process. I wish I had this to work with when scratch building the Grumman Goose!!

  5. Instead of many nails and or clamps I use contest rubber strip on a roll that I keep as a spare and wrap it around the balsa like a boa constrictor, works in many similar forms and can be used over and over. Needs to be kept tight multiple wraps , maybe one pin at the start and one at the end .

  6. Love this kind of building. Mine started when I built the Northcraft Tigermoth wingtips rudder stab and elev.are built that way. on large scale it’s the only way to go I only use bass or spruce

  7. Rather than use plans protector, clear packing tape also works well to prevent the glue from sticking and is what woodworkers normally use. If the balsa sticks are long, use PVC pipe of the appropriate diameter with one end capped to soak the wood. Other options instead of the nails for clamping are to use a bicycle inner tube or strips cut from one or a female form; these spread the clamping pressure evenly and reduce the possibility of denting the outer layer of balsa while ensuring a good tight fit between the balsa layers.

  8. I recommend Titebond III for the adhesive. Stronger and easier to sand than the yellow wood glue. I have started making just about all my wing tips using this method and have also used it for stab/elev outlines. The lamination, even when sanded down to a small cross section, is incredibly strong

  9. I have used SMALL inner tubes for all my engine cowling forms. Position it carefully then inflate ( be careful NOT to over inflate ) or you will be cussing like I did on my first attempt. You will have equal pressure all the way around , and I almost forgot ! Use wax paper between the tube and wood!!!!

  10. Wax paper is all you need to keep glue from sticking. Been using it over plans for 40 years!

  11. Great article…. Good responses too to it. I would only suggest adding a small bit of stain to the spray amonia. Gives a great effect if your laminating something not hidden like making older large wooden propellers. Test each one after construction and balancing on a test engine with eye protection. If it handles full throttle for 15 seconds, your good to go.

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