Edge Joining Balsa Sheeting

I tried out a the technique for edge joining balsa sheeting described on the Airfield Models website on my TF P-47 build. Note: If you have not checked the Airfield Models website, I highly recommend it. A wealth of information and some truly impressive work.

The technique is easy and quick and produces a strong joint. I will summarize the process, but suggest you read through the full description here. The key is the use of standard model airplane cement (such as Ambroid) in place of CA (which is hard to sand) or aliphatic resin (which is slow to dry).

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Step 1: Make certain that your edges are clean and straight. I used a single edged razor and a steel straight edge to cut pieces to the desired shape and 150 grit sandpaper on a hardwood sanding block to lightly clean up the edges before joining. In order to prevent rounding of the edges, hold the balsa flat on your work surface and gently slide the sanding block (with sandpaper on the edge perpendicular to the bottom) against the balsa edge.

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Step 2: Use masking tape applied perpendicular to the joint one one side to hold the two pieces together. The pieces should be pushed snuggly together.

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Step 3: Flip the piece over and apply a length masking tape along the seem.

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Step 4: Remove the tape applied in Step 2 and hinge the pieces back along the tape applied in Step 3.

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Step 5: Apply a liberal film of cement along both edges, then flatten the pieces against your work surface. Using a cloth damp with solvent (e.g.; acetone), wipe away the excess glue that oozes out and re-tape the joint with tape perpendicular to the seem. Be careful not to use too much solvent. My first attempt, I used too much and basically washed away all the glue! At this time, remove the tape applied along the seem and replace with tape perpendicular as well (this allows the glue to dry more quickly and minimizes the chances of solvent melting the tape glue and leaving goo on the surface).

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After the glue dries, remove the tape, lightly sand the joint and your done!

P-47 Stab Construction

Construction of the TF P-47 officially got under way this weekend with the (where else) the stab. Before getting under-way, I paid a visit to the local Staples and had a full scale copy made of the plans. This gives me one set to post to the wall, and another to pin down to my building board. Also, as I plan to make some minor mods to add scale details, I wanted a set of plans I could mark up while still having the originals to refer to.

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Speaking of building boards I recently ordered a Great Planes balsa building board, but as it is on back order until mid-October, I have resorted to the tried and true method of using an upside down ceiling tile with my plans pinned to the surface. At this stage, I am following along exactly per the stock instructions. However, I have marked off the scale hinge locations on the plans and will be using Robart hinge points in place of the standard CA style hinges provided.

Before pinning down the ribs, I sanded a bevel on the front edge to match the leading edge sweep. I used this angle sanding jig which I put together earlier out of scraps from old wood-working projects (you can buy a commercial product for about $25). The jig lets you hold a thin wood strip at any angle relative to the sanding block and make smooth and precise bevels.

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The two large steel wedges are simple dead weights used to keep everything flat to the building board. Going forward, I have ordered a 25 lb bag of reclaimed lead shot from Rotometals and will use this to make up a set if weight bags. For now, the wedges will do.

I have completed the basic stab structure and am ready to move onto sheeting.

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So far so good, but this is the easy part!