Reference / Paper · 2017
Peak of Flight #448: Filling Spirals and Seams
Apogee Components' Peak of Flight newsletter, issue 448 (2017-07-25).
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- apogee-components
- model-rocketry
Reference / Paper · 2017
Apogee Components' Peak of Flight newsletter, issue 448 (2017-07-25).
Apogee Components' Peak of Flight newsletter, issue 448 (2017-07-25).
ISSUE 448 July 25th, 2017 IN THIS ISSUE Filling Spirals and Seams www.ApogeeRockets.com/Rocket-Kits/Skill-Level-2-Model-Rocket-Kits/Sea-Sting Filling Spirals and Seams By Chris Michielssen Tim did a recent video showing how to fill balsa wood grain using Elmer’s Carpenter’s Wood Filler. (In the video, Tim showed the old Elmer’s Fill N’ Finish tub. All new Elmer’s Filler is now renamed Carpenter’s Wood Filler.) The balsa grain on your fins is filled and smooth, but what about the body tube, launch lug, and nose cone seams? In this article, we’ll tackle a sometimes-overlooked aspect of rocket finishing: filling the tube seams. In the pictures, you’ll notice I’m going back and forth between brown and white body tubes. The filling techniques are the same for both types of tubes. Dope based Sanding Sealer and Balsa Fillercoat is getting scarce and very expensive. Elmer’s Carpenter’s Wood Filler (CWF) can do the job inexpensively without all the dangerous fumes. When buying CWF pick out a tub with an orange lid, and look for the word “Interior”. Don’t buy the Pro-Bond “Max” formula CWF, and avoid the black label tubes and tubs. These are made for exterior use. It’s very gritty, dries hard, and is very difficult to sand. You’ll have to thin the CWF with water to fill seams and balsa. A good starter mix ratio of water to CWF is 1 part water, 2 ½ parts CWF. Figure 2: Thin the Carpenters Wood Filler with water before use on seams and balsa. Mix well until smooth. To mix it up, don’t shake it. Use a stir stick and work it for a few minutes until it’s smooth with no lumps. Keep your mixed filler in a small airtight container. If it starts to thicken or dry out you can add small amounts of water and re-mix. Continued on page 3 Figure 1: Elmer’s Carpenter’s Wood Filler www.ApogeeRockets.com/RockSim/RockSim_Information About this Newsletter You can subscribe to receive this e-zine FREE at the Apogee Components website www.ApogeeComponents.com, or by clicking the link here Newsletter Sign-Up Page 2 Newsletter Staff Writer: Chris Michielssen Layout/Cover Artist: Chris Duran Proofreader: Will Franks Issue 448 | July 25th, 2017 Filling Spirals and Seams Continued from page 2 Figure 5: Dip an old X-Acto blade into the mixture Figure 3: Finding seams on the tube Run your fingernail across the body tube. If you can feel the seam it will show up when the model is painted. Dip just the tip, about 1/4” of an old X-Acto knife blade in the mixed filler. Don’t use a new blade, you’ll just be dulling it in the next step. Wipe the excess filler off the back of the blade onto the lip of the container. This is important, you won’t need all the filler clinging to the blade. Figure 6: Use the blade to apply the Carpenter’s Wood Filler Figure 4: Marking the seams The seam is hard to see, especially on brown tubes. You can’t fill what you can’t see. Using a mechanical pencil, draw the lead down the seam trough, marking it down the entire length of the tube. Don’t worry, spray paints will cover the pencil lines. Page 3 Set the filler blade tip in the seam, working it back and forth in the trough. This pushes the filler directly in the seam and eliminates any trapped air. If the blade stays in the seam trough, you end up with less filler to sand off later. Continued on page 4 Issue 448 | July 25th, 2017 Filling Spirals and Seams Continued from page 3 Dip and repeat the entire length of the body tube. It sounds like a lot of work, but like anything else it gets quicker and easier as you go. There is no need to scrape off the excess raised filler, let it dry as is. Any remaining tube seams will be filled with a spray and sand of automotive filler/primer. Figure 8: Sanded after primer Here’s a recent build. You can see some filler/ primer remaining in the seam (over the CWF filler) at the center running from the top left to the lower right of the tube. The tube is now ready for the white undercoats. Figure 7: Sanding the filler Let the filler dry a few hours before sanding or you run the risk of knocking the filler out of the seams. On the left, the picture shows a brown tube with the dried filler in the seams. Sand down most of the dried filler with 220 grit, knocking off the top almost to the body tube surface. I use a sanding block with 220 grit. Follow with 400 grit next to smooth, leaving just the filler in the seams. Filling Launch Lug Seams People rarely fill the seams in launch lugs but it’s easily done! You’ll find it easier to fill the lug seams before gluing the lug onto the body tube. CWF is water based and does not seal filled surfaces so the wood glue will stick to it. Continued on page 5 Need Rail Buttons And Stand-Offs? www.apogeerockets.com/Building_Supplies/Launch_Lugs_Rail_Buttons/Rail_Buttons www.ApogeeRockets.com/Rocket_Kits/Scale_Rockets Page 4 Issue 448 | July 25th, 2017 Filling Spirals and Seams Continued from page 4 Filling Nose Cone Molding Seams Blow molded plastic nose cones will typically have mold seams on opposite sides. The older the molds, the deeper and rougher the seams. First, sand off any raised molding flash with 220 grit sandpaper. Recessed seam troughs will still remain. Figure 9: Insert a Q-Tip into the launch lug Push a Q-tip into the launch lug for an easy painting handle. You don’t have to fill the launch lug seams using a dull knife blade, just brush the filler over the lug and let dry. Figure 11: Use super glue on the nose cone seam Some builders use Squadron Putty to fill plastic joints. It has a plastic solvent in it but the putty starts to dry as soon as it is squeezed out of the tube. I’ve had very good results using the cheap, Dollar Store medium super glue on nose cones. Continued on page 6 Minimum Diameter Motor Retainers! Figure 10: Sanding the launch lug Sand off the dried filler, again removing most of it with 220 grit, then smooth to surface with 400 grit. On the right, you can see the filled lug seams after final sanding. Apogee is your one stop shop for your minimum diameter rockets projects! • Fly High • Fly Fast • Impress Your Friends! We Have: • Minimum Diameter Retainers • Motor Extenders • Threaded Forward Closures • Adapters for Cesaroni Cases www.ApogeeRockets.com/Building_Supplies/Motor_Retainers_Hooks Page 5 Issue 448 | July 25th, 2017 Filling Spirals and Seams After the first seam side dries, apply a glue bead over the seam on the other side. Let it dry thoroughly. Sand the glue line to surface with 220 grit. You can also use a fine diamond file to remove the glue bead. The dried Super Glue is hard to sand, like a hard plastic. Afterward, smooth sand the glue with 400 grit. It’s hard to see the clear glue in the seam after sanding and you won’t find the seam after painting. Follow-up the CWF filling with a good grade automotive filler/primer and final smooth sanding. Like any new technique, this might take some practice. At the next club launch, you could get a few compliments on your building techniques. Continued from page 5 Figure 12: Using super glue on the nose cone seam On the left is the new Apogee PNC-33 nose cone. After sanding, there was a very slight recess seam. Run a bead of medium super glue down one side of the nose cone seam. The bead should be raised over the surface. Only do one side at a time, the glue will run. Block the nose cone so it sits horizontally as the glue dries. This thick glue bead will take a few minutes to dry. About the Author: Chris Michielssen is an avid builder and flyer of low power model rockets. He produces Odd’l Rockets and accessories, available from Apogee Rockets at www.ApogeeRockets.com/Oddl_ Rockets. His building blog, www.modelrocketbuilding. blogspot.com, is followed by 1,250 people each day worldwide. Experienced HPR Builders Use Thrust Plates • Eliminates Shear Forces on Centering Rings • Mates with AeroPacks Flanged Engine Retainers • Fits Standard HPR Tubes, Blue Tubes, and Fiberglass Tubes • Made from Aircraft Grade Aluminum https://www.apogeerockets.com/Building_Supplies/Thrust_Plates www.ApogeeRockets.com/Building_Supplies/Parachutes_Recovery_Equipment/Shock_Cord Page 6 Issue 448 | July 25th, 2017