Model Aviation Construction Series: Balsa Builder's Basic Toolbox

Written by Paul Kohlmann The Balsa Builder’s Basic Toolbox Construction feature As seen in the March 2015 issue of Model Aviation.

I heard from Model Aviation Editor-in-Chief Jay Smith regarding some feedback he had received since redesigning this magazine. He explained that Model Aviation readers had been randomly polled each month to get their opinions on the magazine. Surprising to both Jay and me, an overwhelming response was that many readers wanted more building-related content. In fact, the October 2013 build-themed issue was frequently cited as the most popular in recent memory. As our discussion continued, Jay offered me an opportunity to write a series of articles introducing basic building techniques. The target audience would be those readers contemplating their first balsa build, but we plan to provide enough content to make it interesting for more experienced builders, too. This was music to my ears because I am a better builder than a flier. That’s not to say that I have a Scale Masters trophy on my mantle—I don’t. But I’ve built a respectable number of kits throughout the years, from Guillows through my own creations. Along the way, I have learned two things. The first is that when it comes to building, there is always more than one way to get the job done. With that in mind, I’ll offer a range of ideas on the topics I take on but there will always be room for other solutions. I will also avoid rehashing subjects that were recently covered in Model Aviation by referring readers to past articles, now that the magazine is easily searchable online. The second thing that I’ve learned is that like many builders, I am cheap. I get a thrill out of figuring out how to make do with tools at hand or household products from my local hardware store. After all, that’s part of the fun of building from scratch! So with these two points in mind, let’s start by filling a basic toolbox that we will use to make our first balsa build a reality.

Toolbox Basics

Building Board

Balsa • Flat, soft, lightweight • Available from Great Planes Acoustic ceiling tile • Flat, soft, lightweight, inexpensive • Available at The Home Depot or scavenge them Shelf/cork covering • Flat, soft, lightweight, inexpensive • Available at The Home Depot or McMaster-Carr

Pins

T-pins • Available from Great Planes, Tower Hobbies, Micro-Mark Pushpins • Barrelhead • Available from Tower Hobbies Dressmaker pins • Fine wire, long • Available at fabric and craft stores

Cutting

X-Acto knife • #11 blade • Available from Micro-Mark, Tower Hobbies Razor blades • Single-edge, inexpensive • Available at The Home Depot Razor Saw • Available from Micro-Mark, Tower Hobbies Balsa stripper • Available from Micro-Mark, Tower Hobbies

Sanding

Paper • 60, 150, and 220 grit Bars • 6 inches and 12 inches • Available from Micro-Mark, Tower Hobbies

Odds and ends

Clamps, files, pin vice, bits • Available from Micro-Mark

Selecting a Building Board

Most wood-framed models are built by pinning parts to a flat board. In some cases, a fuselage is built on an upright jig, but even then the wing and tail are often built on a board. In a sense, the building board is the foundation of the workshop. As such, it should be large enough to fit the types of models that you intend to build on its surface. It’s almost impossible to build a warp-free structure on a warped board, so flatness is a must. The surface of a good board should be soft enough to allow you to stick pins into it to hold parts down. If you don’t have a dedicated work area, it may also be good for it to be easily transportable. Building boards made from softwood or balsa can be purchased from Great Planes and other vendors, but to get started, many builders begin with an acoustic ceiling tile from a hardware store. These are inexpensive, flat, and commonly found in lengths of up to 48 inches. The size can easily be adjusted by joining or trimming the tiles.

The author's board is a shelf covered with a sheet of 1/4-inch cork. When the plans are in place, they are covered with waxed paper to protect them.

In my case, I picked up a flat particle board shelf from the lumberyard and covered it with a sheet of 1/4-inch-thick cork using 3M spray adhesive. A quick pass with a sanding bar between projects has kept it going strong for many years. A more advanced strategy is to use a magnetic building board. A common construction technique is to cover a workbench or wooden board with a steel panel. This enables strong magnets to square up and hold down parts instead of pins. A thorough explanation was provided by Mark Freeland in the “Top Five Building Tips” article in the October 2014 issue of Model Aviation. These systems cost slightly more to set up, but the ability to create fixtures and jigs is a significant advantage. After you have selected your board, it is time to mount the plans. It may be necessary to fold them to fit onto the board. Tape the plans down with low-tack tape and then cover it with waxed or parchment paper to keep it clean. The waxed paper also allows parts to easily be removed after gluing. This is a good time for reflection. I like to pause over the clean plans to think through my goals for the project and to plan its path.

Tools of the Trade

Parts are typically held in position with pins while the glue cures. T-pins are often used because they are easy to handle. Tower Hobbies offers barrelhead pushpins that are thinner than T-pins. My preference is dressmaker sewing pins because of their availability and fine wire size. I go through many pins because I discard them after they are contaminated by glue.

Some of the uses for pins include holding parts to the board (crossed T-pins and trailing edges) and sticking parts to other parts (wingtips). Squares keep parts true.

Clamps are used for joining assemblies such as wing panels. Light structures require light clamping forces, and cheap clamps are perfect for this application. Clothespins work well, particularly if they are modified as shown. Small, plastic spring clamps are also handy. In my shop there are three cutting tools that I can’t do without: a #11 X-Acto blade, a box of single-edge razor blades, and a razor saw. Like the pins, the X-Acto knife blades and razor blades are frequently replaced. A simple balsa stripper is also worth the minimal investment.

Cutting tools include single-edge blades, a #11 X-Acto knife, a razor saw, and a balsa stripper. A triangular sleeve to keep the knife from rolling is a must!

Sanding is as important as cutting. I use 60-grit sandpaper for rough shaping and sizing, 150-grit for fitting parts, and 220-grit for finish sanding structures and sheeting. Sanding bars are used for finish sanding and to keep parts square. A small square ensures that wing ribs and fuselage formers are properly positioned. I use several steel machinist’s blocks as squares or to weigh down parts. In the odds-and-ends category, a pin vise, an assortment of small bits, and a collection of small, shaped files are invaluable.

Sanding supplies include 60-, 150-, and 220-grit sandpapers. The short bar on top is fitted with 60-grit sandpaper, while the longer one below has 150-grit sandpaper.

Adhesives deserve an article of their own, and fortunately, Terry Dunn wrote an excellent piece on the subject, which can be found in the October 2013 issue of Model Aviation.

Wrapping It Up

If I were to find myself marooned on a balsa tree-studded island, I would consider myself well prepared to pass the time with this toolbox. Of course, builders accumulate many more tools as they go along, but this will give a new builder a solid start. This information has been condensed into sidebars for your convenience.

A collection of jeweler's files, clamps, and a pin vise with bits rounds out the basic balsa builder's toolbox. Note that the clothespin's spring has been removed.

Until next time! —Paul Kohlmann [email protected]

Follow the whole build! (Building the Miles M.20)

Installment #1 (Toolbox basics)	Installment #5 (Building the tail group)	Installment #9 Casting detail parts
Installment #2 (Balsa builders' parlance	Installment #6 (Building the fuselage)	Installment #10 (Waterslide decals)
Installment #3 Reading plans	Installment #7 Building the wing	Installment #11 (Wrapping it up)
Installment #4 Workflow planning	Installment #8 Polyspan and paint	Download all installments (.zip format - 46MB)

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Download the free plans!

Full-size plans Click here for page 1 of the full-size plans (44" x 34") Click here for page 2 of the full-size plans (44" x 34") Tiled plans (8.5 x 11" pages) Click here for page 1 of the tiled plans (24 sheets at 8.5x11") Click here for page 2 of the tiled plans (24 sheets at 8.5x11")

Sources:

Tower Hobbies (800) 637-6050 www.towerhobbies.com Great Planes (800) 637-7660 www.greatplanes.com McMaster-Carr (330) 342-6100 www.mcmaster.com Manzano Laser Works (505) 286-2640 www.manzanolaser.com Micro-Mark (800) 225-1066 www.micromark.com