Top five building tips

Written by Jay Smith Advice from some top kit manufacturers How-to As seen in the October 2014 issue of Model Aviation.

Click here to listen to a podcast featuring building advice from these top kit manufacturers! Whether you’re new to building or have completed several models, it never hurts to get some insight from others skilled in the craft. These tips can be invaluable, and are possibly a little harder to come by in a hobby filled with RTF and ARF aircraft. It occurred to me that kit manufacturers, such as Stevens AeroModel, Mountain Models, and Retro RC, have a unique insight into building. They design their models, they build and test-fly them, and finally they write an instruction manual to assist builders of all skill levels. Beyond that, they provide support to their customers and answer countless questions relating to building. Eager to share their knowledge and insight, I solicited each of these manufacturers with the same question: What are your top five building tips?

Brian Eberwein of Mountain Models

Follow the instructions: When building from a kit or following a construction article, always read the instructions before you start building. Also, follow the instructions, no matter what your experience level. Modern laser-cut kits often have to be assembled in a specific order, and if you don’t follow the instructions, you may find yourself unable to get some parts assembled. Use a glass top: Use a glass top on your workbench. During construction of a laser-cut kit that does not require pins, it makes a terrific flat building surface. It is also useful while covering your airplane. CA tips: Always use a CA tip when working with thin CA. It prevents you from slopping on too much and helps keep you from gluing your fingers to your model. Use thin CA sparingly. It does not require much CA if your joints are flush. A couple drops on a joint are usually enough. Any more than that is not adding to the strength of the joint, makes a mess when you go to remove the finished part from the building board, and makes it more likely that you’ll need to get your wife’s nail polish remover to unstick your fingers from your model. Sand before covering: If you want your finished model to look better, be sure to sand it smooth before covering. The finer the grit of sandpaper you finish with, the smoother your covering will look. Always use at least 320-grit sandpaper and consider going to 400-grit sandpaper on your models before covering. And make sure you remove all that dust that you created before covering. Applying trim: To use covering for trim pieces on top of other covering, you can apply it before you add the whole piece to the model. Lay your base covering on your glass top with the backing still on. Spray it with Windex. Remove the backing from your trim piece and lay it in place. The Windex lets you move it around slightly to place it where you want. Use an old credit card to squeegee out the Windex and allow it to dry for an hour. Use your iron on a slightly lower heat to quickly activate the adhesive on your trim covering. Then you can apply the entire covering piece to your model and you won’t have air bubbles under your trim.

Brian Eberwein—Mountain Models

Mark Freeland of Retro RC

Flexible fabric glue hinges for control surfaces on small models: If you have ever been perplexed about how to get that perfect gap-free hinge without having the awful visual of a piece of tape stuck over your covering, then you should try this method. It works for balsa and for foam models. Before separating the control surface from its flying surface, apply a double layer of blue painter’s tape roughly 1/8 inch on either side of the hinge line. Apply a small bead of a flexible fabric glue (I use Sobo glue) along the hinge line and smooth it to the height of the painter’s tape with a plastic card (used gift cards work well). Immediately peel off the tape and leave the assembly aside for the glue to dry—usually overnight. When the glue is completely dry, flip the surface over and carefully cut through half to three-quarters of the balsa or foam. Now fold the hinge line back 90° to crack through the rest of the material. Finally, sand a bevel on the bottom side so the control surface can move down as far as you need. Easy way to build an undercambered wing: It can be a real pain to block up the front of the TE of an undercambered wing to get a smooth transition from the ribs to the TE stock. The following method makes it easy. Drill a single hole through every rib. Use a drilling jig or stack-drill the ribs to get the hole in the same location on each. Insert a rod through each rib. I like to use a 7.5mm carbon rod for thicker ribs, or a 3.25mm knitting needle for smaller ribs. Support the building rod in a suitable support or on small blocks of wood at either end, with the wing ribs upside down. Use a second rod to support the rear of the ribs off the building surface. The second rod should be parallel to the first unless the wing is tapered. Now glue the LE and spars in place. Add the TE and use a narrow strip of wood (protected with parchment paper so it won’t stick to the wing) and some light clamps to align the lower surface of the ribs with the lower surface of the TE. Magnetic building jigs are much easier than pins and are a great time-saver: Have you ever wished you could build wooden models without having to pin the parts to a board to hold the alignment while the glue dries? Well, magnets are a wonderful tool. They are quick to use, and do not leave holes or dents in the wood. I have a bunch of laser-cut plywood custom jigs that accept 1/4-inch rare earth magnets, available at www.RetroRC.us.com. If you want to avoid the expense of buying custom jigs, start collecting magnets to repurpose wherever you can find them. For example, if you use an electric toothbrush, save the magnets at the bottom of the brush head when you replace it with a new one. Either use them by themselves or glue them to pieces of wood to clamp your parts down to a magnetic building board. Where do you get a magnetic building board? That’s easy! Get a flat piece of 3/4-inch plywood from the local building supply store, and stick a sheet of galvanized steel plate to it with a contact adhesive such as 3M 77 spray adhesive. A 12 x 24-inch piece is a nice size to work with for most models. Alternatively, you can buy a metal shelf from a variety of sources. Ikea has shelves that are painted steel on both sides of a 1/2-inch-thick board available in two sizes at a reasonable price. Decorating a foamie: Most of us have used a stencil at some time in our lives for school projects or home decorating. Have you ever thought of using this technique to decorate your model? I have used cardstock stencils to paint racing numbers and N numbers on several foam airplanes. Cutting a stencil from cardstock is much easier and cheaper than using the plastic ones sold for that purpose. Use craft store paints and a stiff stippling brush. Just make sure to use a dry brush so the paint does not bleed under the edge of the stencil. Apply a second coat of paint if the first is not dense enough. You can even use the edge of the card stencil to guide a marking pen around the edge to highlight it in a different color. Bending matched wire parts the easy way: If you are anything like me, you find it hard to make identical left and right wire parts for your landing gear, wing struts, etc. I make a simple bending jig. I mark the pattern for one side on a piece of paper, and then glue the paper to a scrap of thick plywood or hardwood. Drill a 3/32- or 1/8-inch hole with its edges aligned with the inside edges of each bend. For sharp bends, it is helpful to also drill one lined up to the outside of the wire. Now insert a drill shank protruding up 1/4 inch through each hole. Starting with the center bend (if both sides are bent from a single piece of wire), use a strong pair of pliers to coax the wire into shape around each of these pegs. Flip the wire over and repeat for the second side of the job again starting at the center bend. If it is a lightweight model, stainless steel spring wire is easier to work with than music wire, and does an adequate job.

Mark Freeland—Retro RC

Bill Stevens of Stevens AeroModel

A sanding tip: Many models require sanding or shaping balsa wood, especially for nose blocks and wing LEs. Often the part to be shaped is adjacent to a delicate fuselage former or rib. Although it is tempting to grab the sanding block or bar and dive right into the task of shaping, some thought should be given to protect the surrounding areas (fuselage sides, ribs, etc.) from unintentional sanding. These delicate areas can be spared from inadvertent shaping by strategically applying masking tape over the area to protect it. After the bulk of the shaping is completed, remove the protective tape and use fine-grit sandpaper to feather the protected area into the newly shaped part. Tape hinge help: Tape hinges have become a popular way to rig control surfaces on electric models because they are quick and easy to prepare and leave a clean gap/sealed hinge line. Applying the tape hinge itself, however, can turn into a mess if your parts move around during the hinge-application process. To make a beautiful, straight, and evenly spaced tape hinge, first lay out parts to be hinged on your building board, carefully setting the distance between control surfaces using an appropriate spacer (scrap of cardboard, plywood, music wire, etc.). Now use a low-tack masking tape and tape the parts to your building board to retain the part placement and hinge line spacing. With the parts held firmly to the building board, there is no need to worry that your hinge line might shift. Proceed to apply your tape hinge directly across the hinge line, then use a sharp knife to trim away the excess hinge material. A glue tip: Instant-set thin CA glues can be challenging to work with because the watery nature of the product (low viscosity) can lead to the glue running long distances over and even through balsa wood. These instant-set glues have a reputation for traveling several inches through the pores in balsa wood, curing instantly upon contact with a hand or finger. To prevent getting a finger stuck to your work, wrap the fingertip(s) that will be used to hold parts in place during bonding with masking tape. The CA glue will not readily stick to the tape. Perfect holes in covering: Many entry-level models use dowels passed through the fuselage to retain the wing during flight. These dowels are installed after the covering process, and it can be quite difficult to navigate a sharp hobby knife accurately enough to trim out a perfect circle through the covering. To prevent making a mess of things with the knife, leaving all sorts of gashes in your fine covering job, you might take this tip to heart. To make a perfectly round hole through covering, fire up a fine-tipped soldering iron, pass it through the center of the hole to be cut, and rapidly draw it around the hole’s edges. This tip has applications well beyond placing holes for wing-retention dowels. It works great for wing-bolt holes, stabilizer slot LEs, and finishing off any other tight-radius penetration through the covering. Clean your soldering iron immediately to remove the residue from the covering. Sharpest tool in the shed: When you were a kid, you had a printwood kit and a dull razor blade. Now that you are an adult with an income, do yourself a favor and buy blades in bulk packs. Use only the sharpest blade for your detail and finish covering work. When working with film coverings, especially the thinner and lighter coverings so popular for park flyers, frequently replace your worn hobby blades. Drawing a new blade through plastic covering and into a cutting mat or glass work surface significantly dulls the blade tip, so that after three or four cuts, the blade will begin to snag rather than cleanly cut the covering film. It is especially important that when attempting to trim covering directly on the model, you reach for a new, sharp blade because the fresh blade will take less effort and pressure to draw across the covering, leaving a finely trimmed edge with little risk of snags or tearing.