One of MAN’s most popular construction plans are for the 1/3-scale Howard Ike racer designed by Henry Haffke. Several years ago, I teamed up with Henry to help him build and finish his giant-scale version of his popular 1970s era, .40-size Howard Ike DGA-5 racer, the Miss Chevrolet.
It included several interesting building techniques, one of which was the building and finishing of its long engine cowl. This article takes you through the steps to build and finish a sheet and balsa-block engine cowl. The techniques can easily be applied to any type of scale or sport airplane as the materials and tools required to do the job are basically the same. Let’s get started.
This is a classic technique that uses basic tools and supplies. Besides a completely built model, you need…
■ 5oz. and 1oz. fiberglass cloth
■ Sharp scissors
■ Pacer’s Finishing Resin
■ Denatured alcohol
■ Several grades of sandpaper (150, 220, 320 and 400 grits)
■ Long sanding bars/blocks
■ Mixing cups
■ Playing cards (use as resin squeezes)
■ Plenty of paper towels for cleanup
■ Balsa filler material
■ Spot glazing putty
1.The first thing to do before starting to assemble your cowl is to install the engine and the fuel system. In this photo, a Zenoah G26 is bolted to the plywood firewall. Be sure to plug the carburetor with paper towel to keep out debris.
2.For the most part, the engine cowl section of the Miss Chevrolet starts just in front of the wing. The fuselage is sheeted with 1⁄8-inch balsa up to the firewall. From the firewall forward, hollow balsa rings are glued together to start covering the engine. This is done because aft of the firewall, all the panels are straight with no bends. The forward section of the cowl starts to become compound curves to blend into the cowl front piece which is shaped from a solid block of balsa (several ½-inch thick layers of balsa sheeting form the block).
3. As the balsa rings are added, the carburetor breather opening is cut in place. The last balsa ring is faced with 1⁄8-inch lite-ply to form a hard mating surface for the cowl front piece. This helps produce a straight separation line between the two parts.
4. Here the nose front piece has been carved to shape and sanded smooth. The aft surface of this part is also faced with lite-ply and it is indexed to fit in place with alignment dowels that key into the aft cowling face. Once this is down, go over all the wood surfaces and fill in any major seams and defects with wood filler. Let dry and sand smooth.
5. Remove the nosepiece and the engine so you can fuel proof the inside surfaces of the engine compartment. Use Pacer finishing resin for this. Mix the two parts together and use a stiff brush to apply at least two hefty coatings, letting the first coat cure before adding the second. The resin will absorb into the wood and very little sanding is needed after the resin has cured.
6. Now sand with 220-grit sandpaper and start filling in seams and defects with glazing and Spot putty. Use a mixing stick or scrap balsa to smear the putty into place and let dry. Use a long sanding block and sand over the surfaces. The long block will take off the high spots and leave areas needing more filler and putty.
7. Repeat this process until you have filled all the blemishes and seams and there are no more shallow areas needing to be filled. Go over everything again with 320-grit sandpaper and then wipe clean with a Tach cloth.
8. Cut your fiberglass cloth to size and lay in place on the area to be finished. Use a stiff paintbrush and stroke the cloth into place. Static electricity will help the cloth cling in place.
9. In a disposable plastic cup, mix the finishing resin with one part A, one part B and one part alcohol. Dribble some of the resin on the top of the cowling and use a playing card to spread the resin into the weave of the fiberglass cloth. No need for a brush at this time. Reposition the model so the side is facing up and repeat the process until you have fully saturated the cloth with resin. Check for any dry areas requiring more resin—these show up as white areas. Apply more resin as needed.
10. After the resin has cured up, lightly sand the cloth with 150-grit sandpaper to remove the gloss finish. Wipe clean with a tack cloth and apply a second layer of fiberglass cloth and resin. Any area where the cloth and resin do not lay down flat against the wood, cut slits in the cloth and press it over itself and apply more resin. Fold the cloth over at the front, add more resin and work it until it all lays flat against the wood.
11. Now, do the same thing for the nose piece. Apply the cloth and resin and cut any wrinkles or buckles in the cloth so it will lay flat. Apply resin, let cure, lightly sand. Wipe clean and apply a second layer of cloth and resin.
12. The second layer has been applied and you can see the excess material hanging down. The best way to trim the cloth is to use 220-grit sandpaper and rub where the cloth and wood edge join. Do it lightly and if needed, apply more resin and let set to produce a nice smooth finished edge. Do the same for the openings in the nosepiece.
13. Here the nose piece has been lightly primed with white sandable primer and placed in position on the front of the model. The priming and sanding is very important and may take several coats and sandings to produce a nice smooth finish. Take your time and let the primer coats dry before sanding. Start with 220-grit sandpaper and when you get close to a perfect finish, switch to 320 sandpaper.
14. Even after several coats of primer, you will still find small blemishes needing to be filled. I find that fast-drying Squadron White Putty used for scale plastic models works very well here. Just swipe it on with a fingertip, let dry and sand the access off.
15. Here the nosepiece is about 95% ready for paint. There are still small pin holes needing filling and sanding. Most of the primer will be sanded off before paint is applied.
16. Prepare the aft portion of the cowling like you did with the nosepiece. When you get a very smooth almost flawless finish, add another coat of primer and sand most of it off. Check for mini blemishes and take care of them before moving on.
17. Start applying any surface details you want to enhance the model’s appearance. Here you see the fake piano hinge I added to the top. This was made with a strip of aluminum tape, small screws and a plastic coated wire glued down the center with thin CA. I cut the small barrels into the plastic coating so it looked like a long hinge.
18. Here the cowl is being painted along with the rest of the panels applied to the fuselage. The fabric areas have been masked off to protect the finish. Apply two or three mist coats of paint. You should not have to sand anymore, all the imperfections were taken care of with the primer coats.
19. To complete the scale appearance of the engine cowl, I added the static scale propeller, decals and the fake exhaust stacks which are recessed in circular depressions about ¼ inch deep.
20. That’s it. Here the new 1/3-scale “Miss Chevrolet” Howard Ike racer looks great on a sunny day at the flying field. The nose piece is held in place with long thin screws which can be seen in the cooling openings. It takes only a moment to gain access to the engine. Though this technique is easy to do, it does require an investment in time. It’s no secret, pay some attention to the details and use plenty of sandpaper to make the surfaces of the cowling look flawless.