Reference / Paper · 2013
Peak of Flight #343: Replaceable Kevlar Lines in Minimum Diameter Models
Apogee Components' Peak of Flight newsletter, issue 343 (2013-07-16).
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- apogee-components
- model-rocketry
Reference / Paper · 2013
Apogee Components' Peak of Flight newsletter, issue 343 (2013-07-16).
Apogee Components' Peak of Flight newsletter, issue 343 (2013-07-16).
In This Issue Replaceable Kevlar Lines in Minimum Diameter Models Cover Photo: The DFR Technologies Atlas V Get one for yourself at: www.apogeerockets.com/ Rocket_Kits/Skill_Level_3_Kits/ Atlas_V_LRO_LCROSS Apogee Components, Inc. — Your Source For Rocket Supplies That Will Take You To The “Peak-of-Flight” 3355 Fillmore Ridge Heights Colorado Springs, Colorado 80907-9024 USA www.ApogeeRockets.com e-mail: [email protected] Phone: 719-535-9335 Fax: 719-534-9050 I S S U E 3 4 3 J U LY 1 6 , 2 0 1 3 Replaceable Kevlar Lines in Minimum Diameter Models By Chris Michielssen My last article in the Apogee Peak Of Flight Newsletter was about how to replace the Kevlar line in BT-50 diameter and larger models. Can you make a replaceable line in a BT-20 or ST-7 model? Yes, and like the last article, it’s easier than you might think. Typical Kevlar Engine Block Tie 18mm Engine The single thinner block at the bottom (Estes EB-20 style) is too thin to allow a notch for the Kevlar tie loop. Here’s the parts and tools you’ll need for the replaceable Kevlar install: From left to right: Kevlar Tie Notch Notched Engine Block Kevlar Line Figure 1: Typical Kevlar tie in a small diameter low power rocket To make a replaceable Kevlar line: Instead of tying the Kevlar around the engine block with a permanent knot you can’t untie, we’ll use a simple noose style knot that can be removed with long tweezers. You’ll be able to check the condition of the line between flights and replace it if needed. To start, you’ll need thicker engine blocks such as those shown in the top row of Figure 2. Figure 3: Tools needed to install a replaceable Kevlar line • A .045” diameter wire to clear the notch of glue • An “L” shaped hook cut from a coat hanger wire • The main airframe body tube from the kit (For this demonstration, the tube is cut short right above the engine block. You’ll need to see both sides of the tube to understand the installation of the tie.) • A thick engine block (this one cut from an engine casing) • A 18 - 24” length of stiff, not braided Kevlar (this line is 135 lb. Kevlar) Figure 2: Different thicknesses of engine block rings The three engine blocks at the top are thicker. The engine block will be still be notched to allow the Kevlar line to be tied around it. About this Newsletter Newsletter Staff You can subscribe to receive this e-zine FREE at the Apogee Components web site (www.ApogeeRockets.com), or by sending an e-mail to: [email protected] with “SUBSCRIBE” as the subject line of the message. Page 2 Continued on page 3 ISSUE 343 Writer: Tim Van Milligan Layout / Cover Artist: Tim Van Milligan Proofreader: Michelle Mason J U LY 1 6 , 2 0 1 3 Continued from page 2 Replaceable Kevlar Lines in Min Dia Models Figure 5: Add glue to the end of the Kevlar line to stiffen the end and keep it from fraying To start, apply some white glue to the last inch of the open end of the Kevlar. Wipe off the excess. Figure 4a & 4b: Simple overhand loop knot used in the replaceable mount Tie an Overhand Loop Knot (as seen in figures 4a and 4b) on one end of the Kevlar. The dried glue will stiffen the line and keep the ends from fraying. You’ll want the end stiff and wound tight to feed through the notch in the engine block. The size of the loop is about 5/8” wide from the knot to the outside of the loop. This makes a loop that easily slips around the engine block. 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Figure 6: Notched side of Engine Block Pick up the dried glue end of the Kevlar with the long tweezers. While the Kevlar glue end is drying, notch the engine block for the Kevlar loop. You can use a sharp knife or a small file. Make the notch large enough so the Kevlar diameter can slip through when the block is glued in place. Match the tweezer and Kevlar position in the picture to easily feed the Kevlar through the notch (Figure 8). Glue the only the block (no Kevlar yet) in place in the main airframe tube as normal. Before the glue dries you’ll have to clear the glue out of the notch for the Kevlar to pass through. Figure 8: Hold the gluestiffened end of the Kevlar with a tweezers or needle nose pliers From the rear, use the .045 wire to push the glue out of the notch. Continued on page 5 We’re Paying Cash For Great Articles for This Newsletter Are you a writer looking for some serious pocket change? We’re paying up to $350 for good how-to articles for this newsletter. If you’re interested, see our submission guidelines on the Apogee web site. www.ApogeeRockets.com/Newsletter/Newsletter_Guidelines Page 4 ISSUE 343 J U LY 1 6 , 2 0 1 3 Continued from page 4 Replaceable Kevlar Lines in Min Dia Models Look through the rear and push the stiff loose Kevlar end through the engine block notch. The tied loop is out the back end. Figure 9: Pushing the Kevlar through the notch Push the Kevlar through the notch until a few inches extend out the top. Figure 10: Looping the Kevlar around the engine block Put the loose end through the tied loop as in Figure 10. Pull down on the loose end raising the loop up and to the top of the engine block. Your body tube should look like the right side of Figure 10. The loose end of the Kevlar has been slipped through the notch in the engine block from the rear. Now pull the loose end out the back of the engine mount tube. Push the bent coat hanger in from the bottom and through the center of the engine block. Turn the coat hanger hook until the Kevlar is looped around the end of the bent hanger. Remove the coat hanger and pull the loose end of the Kevlar down and out the back of the body tube. Pull the loose end of the Kevlar until the tied loop is raised up like the left side of Figure 9. Figure 11: Tightened Loop In Figure 11, looking down from the top, this is how the loop sits through and next to the engine block. Again, this Continued on page 6 • Eliminates Shear Forces on Centering Rings • Mates with AeroPack’s Flanged Engine Retainers • Fits Standard HPR Tubes, Blue Tubes, and Fiberglass Tubes • Made from Aircraft Grade Aluminum www.ApogeeRockets.com ISSUE 343 J U LY 1 6 , 2 0 1 3 www.ApogeeRockets.com Experienced HPR Builders Use Thrust Plates Page 5 Continued from page 5 Replaceable Kevlar Lines in Min Dia Models is a short body tube for illustrative purposes. Feed the Kevlar back up through the top of the rocket and you can tie on the elastic end of the shock cord. Figure 13: Here’s how the line looks pulled out the back of an Estes Sky Hook About the author: Figure 12: Loosening the Loop To check the condition of the Kevlar line between flights – or replace a Kevlar line. Chris Michielssen is an avid builder and flyer of low power model rockets. He produces Odd’l Rockets and accessories, available from Apogee Rockets. Using the long tweezers, reach inside from the rear and grab the knot. (Figure 12, Left side) His building blog: www.modelrocketbuilding.blogspot.com is followed by 650 people each day worldwide. Pull down and the Kevlar loop knot will release. Pull the line out the back. (Figure 13, Right Side) The Most Versatile Alignment Jig Ever Manufactured • Get Perfectly Aligned Fins Every Time • Holds the Tube In a Horizontal Orientation to Prevent Glue Drips • Self Adjusts to ANY Size Tube From 13mm (BT-5) to 66mm (BT-80) • Securely Holds The Fin While The Glue Dries • Kid-Friendly! Helps Them Make Stronger Fins, Resulting in Straighter Flights • Can Accommodate Fins Up To 1/2” Thick • Allows Any Number of Fins on the Tube www.ApogeeRockets.com Page 6 ISSUE 343 J U LY 1 6 , 2 0 1 3 www.ApogeeRockets.com Guillotine Fin Alignment Jig