July, 2002 Vol. 19, No. 7 U.S.A. $3.50
July 2002 Page 1 ABOUT RCSD TABLE OF CONTENTS /C Soaring Digest (RCSD) is a reader- written monthly publication for the R/C sailplaneR enthusiast and has been published since January, 1984. It is dedicated to sharing 3 "Soaring Site" ...... Judy Slates technical and educational information. All Editorial ...... Cartoon Humor material contributed must be exclusive and original and not infringe upon the copyrights 4 "Tech Topics" ...... Dave Register Technical analysis & Design ...... Omen and Omega-E Electric Sailplanes of others. It is the policy of RCSD to provide accurate information. Please let us know of 8 "Have Sailpalne Will Travel!" ...... Tom Nagel any error that significantly affects the Travel Sagas ...... Converting a Chrysalis HLG into a Park Flyer meaning of a story. Because we encourage ...... The Chrysl-Stick new ideas, the content of all articles, model 10 NATS Coverage ...... Lee Murray designs, press & news releases, etc., are the ...... Comments on the 2002 LSF/AMA NATS opinion of the author and may not necessarily reflect those of RCSD. We 13 F3B News ...... Glenn Dean encourage anyone who wishes to obtain ...... A View from Base B: additional information to contact the author...... The US F3B Team Trials RCSD was founded by Jim Gray, lecturer 16 Technical analysis & Design ...... Gregory Ciurpita and technical consultant...... Bending-Moments
RCSD should not be considered to endorse any advertised products or messages pertaining hereto. An advertising rate card is available for businesses, and clubs.
R/C Soaring Digest 556 Funston Drive Santa Rosa, CA 95407 phone: (707) 578-7871 e-mail: [email protected] http://www.b2streamlines.com/RCSD.html RCSD Staff Advertiser Index Jerry Slates - Editor/Technical Editor Judy Slates - Managing Editor, Subscriptions Lee Murray - RCSD Index/Database 6 Aerospace Composite Products 9B2 Streamlines (available on-line) 6 Cavazos Sailplane Design Bill & Bunny Kuhlman - RCSD Web Masters 18 Hobby Club PayPal Coordinators 6 R/C Soaring Digest OTHER GOOD STUFF 19 Classified Ads Feature Columnists Special Interest Groups - New Products Bill & Bunny Kuhlman (B2), 19 Eastern Soaring League (ESL) 3 Schedule of Special Events 19 International Scale Soaring Assoc. Lee Murray, Tom Nagel, Mark Nankivil, 19 League of Silent Flight Dave Register, Steve Savoie, Jerry Slates, 19 Sailplane Homebuilders Association Greg Smith, Gordy Stahl 19 T.W.I.T.T. 19 Vintage Sailplane Association Artwork Gene Zika is the graphic artist RCSD ON THE WEB who designs the unique ZIKA clip art. http://www.b2streamlines.com/RCSD.html
Monthly Feature Photography & Web Version of the Printed Article (where appropriate) Highlights & Mailing Status of the Current Issue About RCSD ...... Subscription Information ...... Advertising Rate Card (Adobe Acrobat PDF format) ...... RCSD Feature Columnists, Reporters, and Editors ...... (E-mail/web addresses, plus general information about their areas of interest) "Getting Started in RC Soaring" ...... Getting started guide - Adobe Acrobat PDF format Links to Organizations, Special Interest Groups & Clubs On-Line Articles - Great articles originally written for the printed version of RCSD...... "Trimming Your Sailplane for Optimum Performance" by Brian Agnew ...... "Flys Faster" by Dr. Michael Selig ...... "The Square-Cube Law and Scaling for RC Sailplanes" by Dr. Michael Selig ...... "Modifying & Building the MB Raven (Parts 1-4)" by Bill & Bunny Kuhlman Copyright © 2002 R/C Soaring Digest. Bookshelf Listings - A listing of recently published books of interest to aeromodelers. All rights reserved. Complete RCSD Index, 1984-2001 Page 2 R/C Soaring Digest The Soaring Site
Cartoon Humor
ope all of you enjoy the 'toons Thanks for your patience and under- included in this issue of RCSD. standing! Enjoy! OurH thanks to the talented Gene Zika and Phil Bauer! And, don't forget that cover photogra- phy is available in full color for Cajon 2002 I'm still having quite a few computer downloading from our web pages. problems, but neither rain, sleet, snow, an Sampson’s Sukhoi Su-25 or tornados have stopped us from Frogfoot tank-killer. Built Happy Flying! fromD Carl Maas molded fiber- enjoying this wonderful hobby and, Judy Slates glass fuselage, balsa sheeted foam with this issue, it catches us up another wings. month! Photography by Dave Garwood, New York.
GONE OOWW !! SOARIN' ZIKA PP I SEE YOU'VE DECIDED TO TRY SCHEDULE OF SPECIAL ELECTRIC EVENTS
FLIGHT! October 18-20, 2002 Deep South Soaring Championships Houston, TX http://home.houston.rr.com/kovacs/hawks/deepsouth.htm February 1-2, 2003 Southwest Classic Phoenix, AZ
Please send in your scheduled 2003 events as they become available!
18 eautiful in full color, all cover photographs are availableB for downloading from ZIKA the RCSD main web page.
July 2002 Page 3 TECH TOPICS
Dave Register hour to spare, one or two battery packs The fuselage is unpainted fiberglass Bartlesville, Oklahoma will fill the bill nicely. with a gelcoated canopy. The trim and [email protected] fit of the canopy was excellent and the Which leads us to a review of the fuselage finish was virtually free of pin Omen and Omega-E designs from Sal’s holes and surface irregularities. A light Omen and Omega-E shop (Northeast Sailplane Products). rub down with solvent would prob- Electric Sailplanes The way this all started was helping a ably be sufficient prep for any addi- young pilot (Andrew Geibel) put tional painting. ver the past year there hasn’t been together the Omen and then realizing much time for soaring at the that this type of ship was a heck of a The push rod jackets are preinstalled RegisterO household. When you don’t lot of fun to fly! and metal pushrods of more than have a lot of time to spare, HLG/DLG sufficient length are supplied. A beefy is a great way to get some exercise and The Omen uses a geared Speed 400 plywood servo try is supplied with the stick time without a lot of parapherna- with a 11 x 8 Graupner folding prop accessories. The wing mounting plate lia. But after you’ve pranged your last and a 7 or 8 cell Sanyo pack. A Sun is already installed, drilled and tapped. DLG, or you’d like a few long flights 1000 unit provides the BEC/Throttle The Omen used metric nylon bolts, the after work, what’s a soaring pilot to function. The Omen planform is Omega-E used English (8-32 panhead). do? I’d highly recommend the new polyhedral with ailerons and a V-tail. I re-drilled and tapped the mounting class of smaller electric sailplanes that The planetary gearbox on the Speed plate for English 10-32 panhead. run on geared Speed 400 motors. If 400 makes for a sleek front end and the you stick with a 500mAh, 7 or 8 cell overall performance was impressive. The wings are pre-built and covered pack, the cost is very affordable. and a suitable length extension cable After getting Andrew up and flying, I out to the servo wells is provided. All The beauty of these systems is that really wanted to give this a try but I connectors, linkage and hardware are they are compact enough to fly safely also wanted flaperons for camber supplied. The V-tail is glass over foam in a decent athletic or soccer field changing ability to help with the low (built up geodesic balsa in the case of (PLEASE have your AMA insurance end of the speed envelope. A quick the Omen) and uses the upper surface just in case), they’re nimble enough to look through Sal’s website found that glass for the hinge (Omega-E only). jog around the occasional tree when the Omega-E matched all my require- This hinge is too brittle and won’t landing and they’re light enough to ments. stand up very well, so a strip of clear not be a serious threat if something hinge tape was applied. goes awry. In addition, the onboard Construction of both the Omen and launch equipment and soaring ability Omega-E is very similar so I’ll high- The V-tail is sufficiently light that CG of the more recent designs can give light the most recent experience balance is not a problem. For the you 20 minutes or more of flight time. (Omega-E) with notes where there are Omega-E, I had to add weight to the Since I rarely have more than about an differences. tail to balance it out properly. On the Page 4 R/C Soaring Digest Omega-E, the rear of the fuselage has a wide and deep enough for the Omen off, we started looking more critically molded in 100 degree slot. The tail but they are marginal in depth in the at the settings. You can get at least 4 surfaces are beveled so that they glue Omega-E. Servo mounting used my decent climb-outs with the 7 cell pack. together at that angle with no extra standard practice of wrapping with The thrust is adequate but not over- fixtures needed. For the Omen, tubes masking tape and then using Goop powering enough to haul it into the are pre-drilled across the fuselage to adhesive to glue the servo in place. (If sky. If the climb angle is too steep, the accept the tail surface mounting rods. you need to remove the servo, unwrap plane will stall or mush. So you need Alignment and decalage of the V-tail the masking tape and lift the servo to use a little down stick under power in both ships is excellent. out.) Then cover the outer surface with to keep the speed up. Flying the climb a stiff prismatic tape and it’s locked like this appears to be more efficient on The power system (several options are down nice and tight. power and altitude than just brute recommended) is a Speed 400 with a forcing it into the clouds. planetary (in-line) 4.4:1 gear box. Prop Connection to the V-tail in both ships is a Graupner 11 x 8 folding unit with a used a Z-bend at the tail surface and a Dive test showed that the CG could spinner. The speed control/BEC is a standard clevis at the servo. move back a bit, but for Andrew it was Sun 1000 and provides a JR style fine pretty much at the factory setting. connector for power and throttle to Ch Radio set-up Aileron differential also helps. This 3 of your receiver. Battery pack is a 7 plane will NOT axial roll so just get the or 8 cell 500 mAh Sanyo with a Deans Andrew used his Hitec 5 channel in differential and rudder coupling where power connector. the Omen. This allowed the use of you want for coordinated flat turns. channels 1 and 5 for ailerons and 2 and Barrel rolls are also a bit dicey unless With all the prebuilt components, 4 for the V-tail. Channel 3 was the you’ve got lots of altitude. Thermal these ships should go together very throttle control to the BEC. turns are smooth and tight without quickly and they did. The only hiccup dropping a tip. The wing loading was setting up a template for the 4- For the Omega-E, my trusty Futaba comes in at ~ 11 oz/sq. ft. so you need hole pattern to mount the motor on the 7UGFS was used. The complication to allow the plane some decent flying Omega-E. What worked well was to here is that channel 7 is aileron while 5 speed or you’ll mush it. But it banks measure the mounting diameter and is flap. Since I was using a 5 channel and cranks just fine when you core a then set up a template in a CAD Rx (Hitec 535), a little programming good thermal. program and print it to size. Then tack was in order. In this case, the simple the paper template on the flat at the solution is to use Glid2F with 100% 15 - 20 minute flights are pretty typical front of the fuselage, drill the shaft aileron to flap coupling. This has the for a climb and glide flying style with hole and the bolt pattern and you’re benefit of putting camber control in its the Omen. You can zip around some done. normal position. After some flight more under power with a subsequent experience, a flap trim value of ~ 20% drop in flight time. Your choice. Once the motor is mounted, solder on works well. (Note - since this first the speed control connectors (blue and experience I’ve upgraded to a Futaba The experience with the Omega-E was green using the European convention) 9CHF and used the channel 5 option.) similar to the Omen. Factory settings, and then solder a capacitor across the etc., and it climbed out nicely on the power leads (supplied with the kit). I’d Off to the field first flight. About two clicks of up trim suggest using some insulation over the were all that were needed. It became capacitor leads so you don’t short The Omen was finished first so let’s apparent that the CG was too far something out by accident. I mounted start here. The CG was set where forward for me but even at that the the speed control circuit to the bottom recommended. Throws were adjusted first flight was 25 minutes. of the fuselage with double-sided foam to the suggested values. The motor tape. It sits directly under the servos control took a bit to set up on the Hitec Next flight looked at the flaperon (fuselage depth is pretty good). namely because it’s different than on setup a little more carefully. Although the Futaba and we didn’t have the turns were very crisp, there was a On the Omega-E, FMA S-60 servos manual at the field that day. But we tendency for the nose to drop into the were used for the fuselage to save nose dumb-thumbed our way around until turn. Loops tracked very well but rolls weight. After a couple of adventures, I we found it and got the reverse weren’t very axial at all, again with the think I’d go a little beefier. Say S-90s or settings right. nose leading into the roll too hard. HS85s or CS21s. The S60s have plenty After about 22 minutes, it was time to of torque but the gears strip easily if In a fit of confidence, I decided to toss come in. you tangle up the tail surface. For the it and let Andrew see what he could Omen, Andrew used standard servos do (he had become quite adept with Next step was to move the CG back which fit in-line behind the battery. his Razor). The first toss was supposed about 0.5. The rudder coupling was This was a bit of a chore to get them in to be just a glide test. However, the eliminated and flaperon differential there so I’d recommend something in setup was so right on the money that I decreased (about 3:2). Next flight the HS80 or 85 category for easier told him to give it some throttle after it showed much better glide and turns. installation. had cruised out a few dozen yards. Rolls were nearly axial from a modest And off it went just like that! dive. At these settings the camber Aileron or Flaperon servos were S90s changing capability began to really or CS21s. The wing wells are plenty After the euphoria of this success wore pay off. With more sensitive thermal
July 2002 Page 5 recognition from the rearward CG, and easy to repair! cranking in camber at the first sign of lift really helped this ship take advan- At any given time, various suppliers tage of light, small thermals. Flights of have different designs in stock. But for 35 minutes or more are not hard to fun and uncomplicated flying close to achieve! home, these smaller electric-assist sailplanes are a great way to get in As with the Omen, powered flight is some relaxing flying time with mini- not intended to haul this ship vertical. mum of equipment. Give em a try With the 7UGFS (or 9CHF) I’ve been some time! able to use the Start preset for very nice climb capability. In this case, a n touch of down is added and about 10% camber. This gives a little extra lift to the wing but with enough down elevator compensation to keep it from porpoising. At least 4 very nice climb outs are typical for the field where I fly.
Both the Omen and Omega-E have proven to be really fine designs that work well. Each is a bit different in performance but both provide their pilots a lot of enjoyment. Each has also had reconstruction opportunities. Andrew got a tree shot from a loose battery connector and I augured in inverted while trying to hot-dog without enough mustard. Both ships have proven to be remarkably robust
A MONTHLY LOOK INTO THE WORLD OF SAILPLANE ENTHUSIASTS EVERYWHERE R/C Soaring Digest (RCSD) is a reader-written monthly publication for the R/C sailplane enthusiast. Published since 1984, RCSD is dedicated to the sharing of technical and educational information related to R/C soaring. RCSD encourages new ideas, thereby creating a forum where modelers can exchange concepts and share findings, from theory to practical application. Article topics include design and construction of RC sailplanes, kit reviews, R/C Soaring Digest airfoil data, sources of hard to find items, and discussions of various flying 556 Funston Drive techniques, to name just a few. Photos and illustrations are always in Santa Rosa, CA 95407 abundance. e-mail: [email protected] There are RCSD subscribers worldwide. http://www.b2streamlines.com/RCSD.html
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Page 6 R/C Soaring Digest July 2002 Page 7 HAVE SAILPLANE, WILL TRAVEL!
By Tom H. Nagel 904 Neil Ave. Columbus, OH 43215 [email protected]
Converting a Chrysalis I consulted with my friend Bill second hole parallel to the first. The HLG into a Park Flyer – Hoelcher who had been flying some diameter of the drill bit isn’t too electrics. He recommended using critical, as long as it is less than 3/16". The Chrysl-Stick about 5 degrees of down thrust and a Use a file and create a rectangular hole couple of degrees of left thrust on the through the nose block, sized to accept on Stackhouse and Joe Hahn are motor mount. Then I consulted the DJ a left over piece of Pico Stick fuselage buddies of mine. They have been Aerotech plans for the Chrysalis HLG stick. (Even after a thorough stuffing, I makingD world class sailplanes since to find out where the center of gravity had a few pieces three or four inches before I ever stripped my first servo. A was supposed to be. That was the long. The Pico Stick fuse stick is metric few years ago they introduced the extent of my design work. sized, but approx. 5/16 by 3/16". You Chrysalis HLG, intended to be an can cut and sand one to fit the hole in entry level, all-wood, easy to build, Step A: the Pico Stick motor if you have to.) good performing HLG. That was The Pico Stick motor sticks on this before discus launch had ever been Cut a piece of thick balsa sheet (1/4" if motor stick. I put it on so the motor heard of, and back when I had a you have any) into a long thin triangle, was below the stick, and I used a clip- shoulder that could marginally launch with the skinny angle 5 degrees; and a on aluminum heat sink, which had a HLG. right angle for the second corner been on the Pico Stick. (which mathematically leaves the third Neither the Chrysalis HLG nor my angle at 85 degrees). The short side of Step C: shoulder are even marginally competi- the triangle needs to be about _ inch tive anymore. The Chrysalis is still on long, which is the distance from your Drill a 3/16" hole (or thereabouts) the market and easy to build. This workbench surface to the center of the through the plywood bottom of the article explains how you can use left Chrysalis nose, when the fuse is on the fuse, right behind the nose block. Use a over Pico Stick parts to convert a bench. This is the guide for drilling small file to open it up into an oval. Chrysalis to a ROG Park Flyer, in holes in the nose block of the Chysalis The Pico Stick motor wire and plug go about twenty minutes. for the motor mounting stick. through this hole into the cockpit area, and connect to the speed control. This project started when one of my Step B: son’s buddies stuffed our GWS Pico Step D: Stick in a thoroughly convincing Tape the triangle to the workbench, manner, fracturing the wooden with the skinny angle at the edge of Find a piece of threaded rod about 1 1/ fuselage stick, cracking the wings and the bench, and tape the Chrysalis 2" long; drill a hole the diameter of the leaving me with a GWS motor, prop, fuselage to the workbench right behind rod through the plywood floor of the flight pack and speed control, and a it. Using a long drill bit, drill a hole fuselage, just about a half inch in front handful of styrofoam parts. I decided through the nose block of the Chrysa- of the first former (at the back end of to find out if the little Pico Stick motor lis, just a smidge off center. Move the the cockpit area, on the center line). I would fly a 60" HLG. fuse over one smidge, and drill a used a small piece of formica sample
Page 8 R/C Soaring Digest re-charge without having to take the end to end – it fit nicely between the wing off. Chrysl-Stick pushrods, under the wing, and I have had a couple of 20 + That’s it. Done. You got a Chrysl-Stick. minute flights so far, without running And while it is not a Speed 400, the out of power. little Pico Stick motor has plenty of power to fly the Chrysalis airframe. The conversion is about 99% revers- ible. Unbolt the landing gear, plug up Using the stock Pico Stick motor, GWS two holes, and you are back to HLG. (As if.) I fly the Chrysl-Stick a whole lot more as a park flyer than I ever did (free samples from Home Depot left as a HLG. over from building RDS pockets) and glued a piece inside and outside the n fuse, and drilled through that. This hole and threaded rod is the landing gear mount. Use a nut or two on the inside; slide the Pico Stick landing gear GONE wire over the rod outside the fuse, and SOARIN' clamp it down with a small piece of thin ply, or formica or a big washer. I set mine up so the gear trailed behind ZIKA the threaded rod, but it works OK either way.
Step E: receiver, landing gear and speed control, you should be able to ROG Stick a piece of velcro on the bottom of and fly long, high semi-thermal flights. the fuselage behind the first former If you use a GWS 0806 prop, you will (under the wing). Initially I used a be able to stop the motor and have the nicad 150mah seven cell pack, and got prop spin down to a stop while flying, 8 minute flights in dead air. Whatever so you can thermal; and you will have pack you use, velcro it down under the plenty of airspeed at full throttle to do wing so that the CG is correct. (I fly loops. ROG takes a smooth surface and mine with the CG almost three inches a 30 to 50 foot run, but is totally from the leading edge of the wing.) reliable. I eventually bought a 650 mah The battery connector can stick out on NIMH pack, a sort of carrot shaped the front side of the former so you can thing with 4 cells and 3 cells attached
July 2002 Page 9 Comments on the 2002 LSF/AMA NATS By Lee Murray Appleton, Wisonsin Jon Stone’s [email protected] Addiction fuse and MH-32 wing (custom).
Don Woelfel’s Edge. “Gravity Sucks” on left wing...
fter an 8-year absence, I returned to the NATS. One thing that was theA same was the oppressive heat and humidity. Some of the things that I found different, I think readers will also find interesting. I’m not going to cover what you can download from the AMA site because much of that is excellent in coverage. The NATS results can be obtained at: http:// www.modelaircraft.org/Comp/ 2002Natsfront.htm\.
I arrived Wednesday afternoon and, after unpacking, I headed out to see Ben Roberto & Stingray 7. Hand Launch Golf at Cardinal Hills Lenny Keer’s Escape, Golf Club. I shot some nice video on convertable sailplane. the 9th hole capturing the entire flights from tee to green. Seeing the discus launches was new to me. I would Lenny Keer’s never have imagined that launches like Escape w/ sailplane nose. that were possible by athletes and old timers alike. With some coaching on the green, modelers landed their models very close to the cup in a single flight. Following the golf task there James Beck & was the task of knocking a plastic Ernest bottle off an inverted paper cup Schlumberg’s without knocking over the cup. Several Eminar 100’s. people were able to do it and one even hand caught the model after being successful at the task. contest so some were out and in use. Some of the more artistic models are Thursday was the start of the Unlim- The photograph of the transmitters shown in the photographs. Jon Stone ited event. The number of molded being used in RES showed a much of Madison, Alabama designed his airplanes being entered surprised me: different distribution of older and own. Jon said he used a number of Edges, Icons, Emeralds plus some lower cost radios. programs including PC-Soar (my strange looking sailplanes, Mantises. favorite design program - ljm). These were long poles with a very Radios used for small pod on the front for the electron- Unlimited Class: RES and Nostalgia were flown on ics and the wing on tall pylons. A high Airtronics 32 Saturday with alternating rounds. percentage of the radio transmitters JR 24 These events were more relaxing for were computerized. I took a snapshot Futaba 10 the competitors. Several were heard to survey of what brands of radios were Multiplex 5 say, “The pressure is off.” One reason being used. This was during the Hitec 2 may have been that the landing task Page 10 R/C Soaring Digest Gerry & Jim Marcicki w/Edge. was modified to increase the distance between the landing circle and the safety line. I believe it was doubled from 8 to 16. While I didn’t violate the safety line, several people did includ- ing one LSF official who will remain nameless. Only one person in 2M and UNL (4 days of flying) was able to get a 100 point landing. The 100 point landing was earned by landing on a 4" disc. That would be about 1 perfect for 2000 tries. Some competitors felt like the landing circle met the goal of eliminating fly offs. Others felt like landings were too difficult and had a RES radio sample. way of ruining an otherwise good performance, especially if you slid past Mark’s Esprit, Nostalgia. than those who had more conservative the safety line. There was a suggestion launching methods perhaps dictated that a plastic snow fence be provided not expecting the power that these by the durability of their models. next year to protect fliers and timers winches were capable of producing. but end the problem of sliding past the Utilizing the capability of the winches The LSF was balloting for 4 options for safety line. in zoom launching was very spectacu- future NATS event schedules. Some lar and I suspect was an important part events attract only a few competitors Many RES and Nostalgia models were in winning the UNL event if you had a while others fill up. There is some overstressed on the launch equipment. heavy ship or needed more time to pressure to give more time to RES and It was possible to launch models safely find some lift. People who could F3J. It is not clear how much support but I believe many people just were maximize the launch were 1/3 higher the new class will receive in registrants July 2002 Page 11 and volunteers to run it. President Jack Strother and the LSF crew did a great Motor Used Energy Estimated Altitude Reached job of running the contest, communi- cating the goals of the LSF and plan- Aerotech D7 re-load 20 Newton-sec 500-600 Feet ning for future NATS. Aerotech E6 re-load 40 1200 Aerotech E6 expendable 44 1300-1400 ~limit of visibility During the lunch break, there was a demonstration of a rocket-powered including coming up with the Aerotech E6 expendable/40N-sec model glider. The model, a Stingray wing and tail airfoil and cut the ignited by an electrical system. Details series 7, was designed to compete in cores. George shaped the core of available systems can be seen at the S8E FAI event, which includes a leading edges and cut the fiber- http://www.aerotech-rocketry.com/. declared duration and a precision glass and carbon pieces. And I did landing. The Stingray series was first the rest of the molding and bag- A full size ASW-27 glider was as- designed by Kevin McKiou of Chicago. ging work including the fuselage sembled in the parking lot and was Versions 5, 6 and 7 had the additional plug. admired by all. The detail on the full design support of George Riebesehl size glider was very impressive. A and Ben Roberto. Ben is pictured in the Stingray 7 featured a more conven- modeler or two was commandeered to photo holding the Stingray. Phil Barns tional dihedral scheme with a flat help set up the glider. was the pilot. center section to accommodate a full-span center section landing Saturday evening, the night before the Three demonstration flights were flap for the new precision duration electric competition, I watched some of performed with three sizes of motors. rules. Stingray 7 also had a larger the competitors limbering up with FAI motor limit for Impulse is 40 inverted v-tail tail. The original park fliers. Even these flights were Newton-sec.; a combination of force formula for the v-tail was based on impressive for the length of time in the produced and burn time. The rulebook projected area. The newer one took air and the variety of aerobatics says you’re allowed +10% more power into account the v-tail angle as per performed. In another field the free than the 40 N-sec, hence the 44 N-sec Mark Drela flight modelers were making test motor. The English equivalent of 40 N- www.charlesriverrc.org). flights of their limited motor run sec would be 9.0 lbsec. models, towline gliders, and hand Phil built several Stingray 7 using launch gliders. Phil demonstrated that the model my notes and plans. He used could be pointed straight down to Kevlar for the wing skins instead On Sunday morning I went out to the return it to earth without a problem. In of 0.75 oz. glass and Japanese field to scavenge information from the the boost phase, the model was tissue as we used on #6. The same Class A and 1/2 -A electric competi- actually flying faster. Good engineer- carbon spar was used. Phil also tors. Lenny Keer showed me his ing and a strong lightweight model are used my original fuselage plug/ molded Escape sailplane. Some obvious essentials. Even with the all mold combination for the pods. modelers feel that this may be the best these requirements, the model would For the pods, I used 2 layers of 1.5 fiberglass fit and finish of all the slow down for hand catches. oz. Kevlar. Phil chose to use the molded ships. The model was quite hybrid Kevlar/carbon fabric. The versatile. That one could change power Ben describes the model’s construction tail boom is an Avia G-Force plants by exchanging nosepieces. Even as follows: Standard Ultra-Light. a glider nosepiece was an option. Lenny was partial to Hacker motors The Stingray series of rocket Ben says that the 2002 World Champi- because he felt they gave the best gliders was designed by Kevin onship event is now a precision performance for the dollar. I saw McKiou ([email protected], duration event with a 6 minute task models where the pilots would not [email protected]) up here in onto a landing strip scored man-on- spend all their motor run time at the Chicago. George Riebesehl and man. The landing strip is 50 meters start of a flight for visibility reasons. I myself teamed up with Kevin to long to accommodate up to 5 pilots. was also impressed with James Beck develop Stingrays 5, 6, with 7 Landing within 0.5 meters on either and Ernest Schlumbergs “Eminar” 100 being my notes for the next side gives you 100 points, 1 meter on for limited motor runs. They each had version. The Stingrays up to #6 either side gives you 50 points any- a one-piece 100" wing that they featured parabolic dihedral thing outside of that but within an vacuum bagged. They were generous scheme like the Hobie Hawk. This overall landing boundary gives you 25 in giving me information about low was done by bagging the wing points. (A big contrast to the 4" 100 cost - good performing systems. Before while on a curved bed. The lay-up, point circle of this year’s NATS - ljm.) I left I saw an official Class A electric from top to bottom: top core bed/ Ben believes that the working time is flight that was very impressive. I’m wing lay-up, pink foam core/ 12 minutes to get your transmitter and thinking that I have some work to do Mylars/ vacuum bag/bottom core make a flight. The Spacemodeling in matching my components to get that bed/curved bed. organizers will probably adopt the kind of performance. procedures used for F3B or F3J dura- Stingray 6 was a team effort of 12 tion, but still limit it to 3 mandatory n models for the 98 World Champi- rounds, and 2 flyoff rounds. At the onship. Kevin did the aero work World Championships Phil will use
Page 12 R/C Soaring Digest A View from Base B: The US F3B Team Trials These guys know exactly what their airplane is capable of, and fly right up by Glenn Dean evened out some, and several flight to the outer limits. They aren’t extreme [email protected] groups had very light and spotty lift, planes — they’re actually quite pre- Decatur, Georgia resulting in some very impressive and dictable. The pilot has to know exactly tactical flying. Round 6 speed and how much to expect from a launch, or (Originally appearing on RCSE, reprinted distance will be flown in the morning, how far he can search under what with Glenn’s kind permission.) followed by round 7 and then the final conditions, in case he has to bail across results and identification of Team a field of sink to find the one patch of he US F3B Team Selection Trials USA. rising air on the field. continued today with 15 of the hottestT soaring pilots in the US com- Lessons Learned 4. Check small things. peting for the three coveted slots on “TEAM USA”. Five rounds are com- I’ve had the distinct pleasure as Attention to detail is where it’s at. The plete; rounds six and seven are ex- serving as an official timer and punch- F3B guys here obsess over the exact fit pected to finish Monday and we will ing laps down at Base B in the hot and finish of their airplanes, and have name the team for next year’s world Georgia sun, and have seen a lot of the them trimmed to perfection. They have championships. action. So what did an average thermal intricate systems to keep track of what flier learn from watching F3B? Well, winches and batteries have launched The day’s flying started before 8 AM like one of our club members Buddy how many times, with what line, so with challenging conditions. Pilots Roos said, it’s like getting free sail- they know when to change out a line flew two rounds of duration first, plane lessons all day long. It’s not that’s about to go. All those little under heavily overcast skies and every day you can watch the best of things add up to a big increase in temperatures in the low-to-mid 60s. the best compete up close. Here’s some performance. Lift was sparse, and many pilots of the general things I observed: scratched their flights out between 5. Know when t’ hold ‘em; know treetop height and launch level. Winds 1. It’s all about TEAM. when t’ fold ‘em. all day were about 8 knots out of the east, with little slope lift to be found on I was surprised to see how much a The best teams/fliers have figured out the tree lines. Still, the skills of our best great team makes or breaks a pilot. The their go/no go criteria before they pilots showed — they still maxed their whole group has to be functioning launch, and talk about it during flight. times, even with heavy F3B planes in flawlessly to put a good round to- “Past relight point, fly what you got,” conditions that would have your gether, and the winch guys are really you hear. If conditions don’t meet their average thermal pilot on the ground in humping, especially when they are criteria, they come down NOW, under 3 minutes. switching drums, changing lines, and decisively. Indecision on relaunch running back and forth for multiple loses precious seconds that you may Two rounds of distance followed reflights. West coast team Botha/ not have. I saw teams relaunch three under the same conditions — ex- Zaballos/Jennings, and East coast times during a speed round — three tremely difficult with lift spotty on team Lachowski/Kiesling/Lawless launches in under four minutes! — to course, but the occasional thermal seemed to have particularly well- get what they wanted. That whole drifted through to make things excit- practiced techniques and procedures. team had to move like clockwork to ing. About noon the skies cleared to It may be individuals who get selected make that happen. bright blue with cumulus clouds, and for Team USA, but these guys are conditions became strongly cycling, knocking themselves out to make each 6. Good enough is all you need. and a third round of distance (the fifth others’ flights the best they can be. for the weekend) was flown after I noticed this watching some of the lunch. Gavin Botha put up the high lap 2. Ya gotta be smooth. less-experienced F3B hands. Some count for the weekend with 25 laps. pilots will bail from lift that is weak — Smooth, consistent flying is the name but will get them their 10 minutes — to Two rounds of speed followed. of the game. Inconsistent fliers will put go after something that looks stronger, Slightly variable winds and cycling up one hot flight only to bomb the only to have it fall apart on them. conditions on course caused many next, and low-level pilot-induced Other relighted after an OK — but not pilots to elect to relaunch to try and oscillation cost more seconds on speed ballistic — launch, only to get a launch maximize their conditions. Times were runs than any bad launch (AKA too that was worse than the first, or get generally in the 18-22 second range, LOW too FAST). One of the most sink on course. with the fast time of the contest thus memorable speed runs, for me, was far set by Darrell Zaballos on Saturday flown by Gordon Jennings. It wasn’t 7. CONFIDENCE, BABY! with 16.9 seconds. Despite the close-in the fastest, but the plane looked like it tree lines providing a psychological was on rails from the start of the The fliers who grabbed victory from hazard for the pilots, everyone finished launch to the end of the speed run — the jaws of defeat in marginal lift on a speed without incident. smooth, steady, consistent. long flight stayed confident the whole time, and their crews were always We flew two more rounds of duration 3. Know your limits — and use positive. I won’t say they made their after speed, starting round six with the ‘em. own lift — but the mental edge had to last duration task. Lift cycles had help. I know I’ve been more often July 2002 Page 13 defeated by sinking feelings than almost completely dead air, with the USA at the World’s in Germany next sinking air, myself. high times in the 19 second range. year. GO TEAM USA! Light thermals began to cycle onto the What were the hot planes? course by 0930 as we started round 7 Here are the final scores, after speed, and course times improved to a throwout. The closeness of the scores The ones flown by the hot pilots, of fast time of just over 17 seconds, not will give you the idea of the kind of course! Heck, from Base B I can tell quite beating the course record set on flying we saw over seven rounds: you there were 14 V-tails and one Saturday. We lost one plane — which cruciform tail — what more do you fortunately was not severely damaged 1. Gavin Botha 17652 need? — to a radio failure during one speed 2. Mike Lachowski 17566 run, when the radio shut off just as the 3. Darrell Zaballos 17545 OK, there were a few planes that dive onto course began. The plane 4. Tom Keisling 17437 caught my eye among the Ellipses, pulled out, circled, and landed all on 5. Gordon Jennings 16948 Cobras, and Tragis. its own with some minor cracks and a 6. Ben Lawless 16898 delam. Oleg Golovidov finished the 7. Rich Burnoski 16760 - The “SP1”, an original design contest flying his backup Stratos. 8. Phil Renaud 16632 flown by Botha and Zaballos. 9. Brian Agnew 16400 Following speed we flew round 6 and 10. Dennis Phelan 16355 From down at the turnaround, it 7 distance. Lift conditions continued to 11. Oleg Golovidov 16114 looked like these planes were consis- improve with cumulus formations 12. Jeff Stiefel 15332 tently outlaunching the rest of the over the field, leading to strong cycles 13. Mike Leal 15064 field. Of course, I’m sure the pilots of lift and sink. Several flight groups 14. Don Sciegel 14642 helped, as did the unique super- were able to turn in fast courses with 15. Bill Wingstedt 14244 special construction winches with the strong thermals on course -- high lap double-bearing extra-long drums. count set at around 24 laps. Several Flying Technique Observations These planes seemed to range well, other flight groups were treated to hang well, go fast, and go slow. The heavy sink, and rushed to relaunch What follows are the specific observa- planform looks unique, probably into better air. tions about flying techniques that I specially tailored. Gavin said the plane found from watching pilots at the F3B was designed specifically to launch Following the two distance rounds and finals. For those familiar with F3B, this well, and that it definitely does. a lunch break, we flew round 7 is probably old hat, but I find that even duration, which saw two flight groups reinforcing things I know can be - The Icon. launch into booming thermals, and the useful. other two flight groups launch into Of course it stood out; it was the only marginal lift that resulted in scratching 1. Launching conventional-tailed airplane on the to make times. One pilot fought for air field. It’s a BIG plane, and flew like it time at treetop height way downwind, If there is one absolutely critical must- was on rails. Its pilot (Jennings, I and clipped a tree, luckily recovering have skill for F3B, it seems to be think) put up some very consistent just above the ground and recovering launching. Heck, that’s probably true flying. the plane back to the field. of any sailplane flying — barring good air, you only have the energy you put - The Caracho (sp?). Despite a few thought of putting in into the plane at launch, so you’d round eight, we ended the contest better make the most of it. Lachowski & Kiesling flew this design, after round seven, at about 1300, and and possibly some others. Has a pretty had the field cleared by 1530. I saw a lot of different launching unique look — pylon mounted wing, techniques and styles at the finals. The unique planform, wide-chord ailerons The combination of good conditions, highest, most consistent launchers & flaps. These seemed very fast & thorough preparation, herculean work seemed to have the following in maneuverable — quite impressive in by the CD and his assistants, great common: speed & distance. club support, and outstanding flying and cooperation by the attending - They know their equipment. The - Brian Agnew’s plane — a Warp pilots and crews combined to make plane is trimmed for a hard pull and (I think). this a great event. quick rotation on launch — a carefully tuned mix of CG, hook position, flap Clean lines, nice handling — a lot of I’m glad I came and helped out. I had a settings, and elevator preset. They potential there. Someone told me lot of fun, and learned a lot watching a know what their winches are capable Agnew hadn’t flown much F3B — you lot of great fliers. of, and adjust both line and drums to could have fooled me! suit conditions. Teams were running Who made the team? mono as narrow as 1.05 mm and 1.11 Day 3 ... mm, changing out entire spools as Congratulations to: Gavin Botha, Mike needed if the line got nicked or over- Flying began just after 8 am today after Lachowski, Darrell Zaballos, and Tom stressed. They had those procedures the mist lifted, revealing clear, cloud- Keisling (alt) for their great flying. down, and had their winch-area set up less skies and virtually dead calm just so, to maximize their launch conditions. We flew round 6 Speed in These pilots will be representing the effectiveness — marking winches and Page 14 R/C Soaring Digest batteries based on number of launches, - The pilots immediately started to myself thinking: “Where are the guys keeping equipment clear in case of a execute the task at hand. They had a like this when I need a timer?” winch backlash, and that sort of thing. plan beforehand — if they were going to abort based on the launch, they 4. Distance - The whole team drilled the same aborted right then, otherwise they technique over and over, and the went into their plan. You could tell the - I thought this was the best event. launch was a team event. Pilot checks indecisive pilots — they would kind of (Partly because I got to fly a lot of it airplane; winch master confirms float around a bit off of launch, losing leading up to the event when we were correct winch is selected and winch is altitude without accomplishing training the officials. It’s a LOT harder on. Timer indicates ready. Spotter anything. than it looks!) It’s not as pure-adrena- checks the air, and confirms the pilot’s line ballistic as speed; it’s much more flight plan. Pilot tells launcher when to 2. Landing tactical, combining good air reading go (on the horn, or wait). Pilot: skills with good turning and racing “Ready.” Launcher: “Set,” braces, and - Unlike TD, F3B is not a landing skills. Except for the number of people gets arm back into throwing position. contest — or else it is, and everyone is needed to run it, it would be a great Pilot: “Go.” — Launcher (or just too good at it. It’s a big spot, 1 event all by itself. winchmaster) stands on the pedal, meter per 5 points, and I saw very few building tension until the winch starts landings under 95 points. Crews - These guys know a lot about ballast, to stall. Then the launcher leans back helped by laying the tape out into the and have tried all different settings at and throws the plane for all he’s wind, and counting down time until all different conditions. They’re worth. The well set up planes are the plane was right close to the end of constantly adjusting to suit conditions, flying the second they leave the the tape. and comparing notes with each other launcher’s hands, already rotated for about how much lead they’re adding. maximum climb. Less proficient crews - Also unlike a TD contest — where had a jerk or waggle as the plane you see every kind of landing tech- - It’s tactical flying. Sometimes its best stalled on launch, losing some poten- nique imaginable, from the wallow- to cover the top guy in the group, tial as the plane got back to flying stall-splat to the speed-dork-spike — flying in his air, so at worst he beats speed. everyone used a very similar tech- you by a lap or so. Other times, your nique. They used their flaps early in read on the air is best — we had a - The launch is consistent. I saw a the approach, to get down to one couple of rounds where there was one number of pilots that circle-towed, approach speed — fast for control, but guy on one side of the course, and the doing big S-turns on the line to build not too fast. Then (unlike me) they other three on the other. Sometimes line tension before climbing and came in with a clean airplane on a the lone wolf buried everyone; some- zooming. Except in the cases where steady glide path (about two spans up times he got buried; once it even they used this for a slight adjustment at 15 seconds and 75m out), applying looked like the lone wolf was in worse to get into the wind, though, I never flaps right at the end to stop the plane air but tricked the other three into saw this pay off. The highest launches over the spot, either settling in or with coming down and relaunching into his all seemed to come from pilots who a slight nose push to stop the plane on air. Definitely a thinking man’s game. climbed straight and smooth into the the spot. I didn’t see too many AMA wind with minimal heading correction “spikes”. - Smooth flying pays. The high lap before the zoom. Of course, they also counts not only usually had good air, got the best setup, tension, and throw, 3. Duration but every turn looked the same. Know too. when to speed up, and when to slow - Not too much different here, except down. Denis Phelan was explaining - Zooms. That monofilament zoom is that F3B guys fly heavy airplanes for how to get consistent — by timing amazing. The consistent teams would 10 minute tasks every round, and we’d every lap until you get each two-lap have a signal when the line was at max rather have our 3-5-7 landing contest upwind/downwind combo to the tension, and would tell the pilot when with 57 oz. airplanes. The pilots had a same rhythm. It looked like the team to zoom. This wasn’t really that far up good plan at launch, adjusted for the helped out here, too — the turn the climb — maybe 60-70 degrees up conditions, and weren’t afraid to bail indication system worked on both from the turnaround, no where near as to cross the field or run way down- light and audio signal, but since when far as we tend to do on braided line wind if necessary. They turned several planes turned at once the audio with thermal winches. They didn’t perfectly smooth, whether it was a could get slightly delayed, the guys dive too deep to start the zoom, and slow, wide, 10 degree bank circle, or a turning on the light wasted less time immediately rotated smoothly and tight, spinning 45 degree bank circle. than those turning on audio only. pinged off into a climb. I saw all sorts And they weren’t afraid to circle at of climbs, from shallow to vertical, and treetop level a quarter mile downwind - Have your relight drill down. ‘Nuff even past vertical. I guess in theory if that’s where the lift was. Know you said. vertical is probably best, but the best airplane is the name of the game here. zooms seemed to come from about a 5. Speed 70-degree climb. Too many of the fliers - A good team helps here — the best doing vertical climbs pulled past were giving constant, positive feed- - You’ve got to be ready. The start of vertical, climbing inverted, or pushed/ back about where the lift was, how to your working time is no time to find rolled out too late, losing altitude at adjust the thermal circle, when to stick out that something on your plane the top because they had no airspeed. with it, and when to bail. I found ...continued on page 18 July 2002 Page 15 Bending-Moments
Greg Ciurpita Somerset, New Jersey http://ciurpita.tripod.com/rc
think most wings are over-built. This doesn’t mean that they can’t be broken,I just that they are built too strong where they don’t need to be, and not strong enough where they could be. Rather than guess, a modeler needs to know how strong the wing needs to be, and where that strength is needed. The simple answer is they can be weak at the tip, and strong at the root. The more complete answer is how much stronger.
It should be obvious that a little upward force near the wingtip creates a much larger force near the root if the fuselage is held still. This force is called a bending moment. It is actually trying to pull the bottom spar cap, putting it in tension, and is compressing the upper spar cap. Both of these forces are greatest near the top and bottom, and decrease to zero near the middle of the spar.
The bending moment at any point is calculated by multiplying a force by the distance between that point and the force. Figure-1 shows these forces on a wing where the tip is on the left, and the root on the right. The 3 ounce force at the tip is shown with the upward arrow. The moment arm is 40". The bending-moment is shown with the clockwise arc on the right, and is 120 oz-in.
The same force produces a bending- moment all along the wing. Figure-2 shows the bending-moment due to the (constant) across a rectangular wing, lb. at its midpoint which is 75" from same 3 oz. force at a point closer to the then the entire force of each halfspan the root, producing a moment of 75 lb- tip. In this case, it produces a bending- can be approximated by a single force in. The combined moment for the moment of only 90 oz-in, 30" from the midway between the root and tip. For halfspan is still 100 lb-in. (See Figure- tip. Any force on the wing contributes a plane with a 200" wingspan and 4.) to the bending-moment at all locations weighing 4 pounds, each halfspan is from the point of the force toward the 100" and supports 2 pounds. This This example emphasizes how much root. Similarly, the bending moment at results in a bending moment of 100 more the outer portions of the wing any point on the wing is due to all the pound-inches (lb-in) at the root. See contribute to the total bending moment forces outward of that location on the figure-3. at the root. It also seems to suggest wing. how the moment may be calculated for Another way to come to the same multiple tapered wings by multiplying While a wing is generating lift, there is result is to split each half-span, with the force generated by each section by not a single force near the tip, but an each quarter-span supporting one the distance from the root to where upward force distributed all along the quarter the weight of the plane, 1 lb. that force is effectively centered. But wing. The bending-moment at the root The inner quarter supports 1 lb. at its these examples assumed a uniform lift is due to the entire force on the midpoint which is 25" from the root, distribution. halfspan. If the lift is (unrealistically) producing a moment of 25 lb-in. assumed to be evenly distributed Likewise, the outer quarter supports 1 To precisely determine the bending Page 16 R/C Soaring Digest how little variation there actually is between the too extremes, a rectangu- lar wing with uniform lift distribution, and a triangular planform.
Figure-5 shows the bending moments from root to tip for several representa- tive wing planforms. While we’ve only discussed the total bending moment at the root, it’s important to know the total bending moment at each location on the wing to properly design the spar at that location.
There are two plots for a rectangular wing. The 1st and uppermost plot, is a plot assuming a constant lift distribu- tion across the entire span, from root to tip. This is the same as the example illustrated by figure-3. The 2nd is a rectangular wing using a more realistic lift distribution. The 3rd is an elliptical wing with an ideal elliptical lift distribution. The 4th, and bottom-most plot is for a triangular wing with a somewhat realistic lift distribution. The rectangular and triangular wings represent the two extremes. Any other wing planform should be somewhere between the two.
All of the plots are for wings of the same area generating the same amount of lift, but because of their shape, the center of lift may be closer to the root. The rectangular wing has the center of its lift force furthest from the root at midspan, and therefore has the highest bending-moment. The triangular planform has the center of its lift closest to the root, and therefore the smallest bending moment.
The most important thing to see in these plots is that the bending moment decreases very quickly. For the rectan- gular planform, it is has decreased 25%, roughly 1/8 of the distance from the root to the tip. It is nearly half at approximately 1/3 the distance to the tip. And is approximately a 1/4 at 1/2 the distance to the root. From a differ- ent perspective, a wing needs to be twice as strong at the root as it is at 1/3 the distance from root to tip. The outer moment, requires an accurate lift an accurate lift distribution, but more half need only be half as strong as it is distribution for the planform being methodical accounting by dividing the at 1/3 the halfspan. And these ratios considered. Even a rectangular plan- wing into many small sections. This is are basically the same for all plan- form has a more elliptical than uniform more easily accomplished today than forms. lift distribution. This means that the when Martin Simons discussed wing loading across the span varies bending moments in a short series of The bending moment at the root is four with span location for all but truly articles entitled Elementary Stress, in times greater than at midspan. Making elliptical planforms. Accurate bending the Nov-Dec 1996 issues of RC Soaring the wing twice as strong at the root moment calculations not only require Digest. But you might be surprised than at midspan is not enough. It will July 2002 Page 17 (dimensions and material) for large ...continued from page 15 still break at the root, before it breaks portions of the wing. This note shows at midspan. While adding weight in doesn’t work. (Finding out when you that the bending moment decreases the wings doesn’t make the problem enter the course is even worse!) rapidly. If the wing fails, it will most any worse, it does make the plane likely fail for a given spar design at the heavier, and adding weight to the - The consistent runs started at the point closest to the root. If a wing does outer parts of the wings makes it more launch. The speed run really started at fail away from the root, most likely it difficult to roll the plane, and less the push -over from the zoom, with a will fail where the spar design changes sensitive to thermals. While bending steady dive toward base A followed by (e.g. no webbing). Since the bending moments are an important consider- a quick vertical dive and smooth pull moment reduces quickly, even some ation in designing wing spars, shear into the course. The guys who moderate strengthening near the root strength is another. “floated” off the line generally seemed can help tremendously. But it’s also to lose more altitude and start with important to recognize that material Shear affects wings in the vertical less speed than those who were and weight can be removed from the direction, and is simply the strength aggressive at entry. The initial dive spar further from the root. While this needed to support the load on the onto the course looked really hard to does weaken the spar where it doesn’t wings. The bending-moment causes judge — a perfect dive meant coming need to be as strong, it makes the wing horizontal forces putting the lower on course at maximum velocity. Dive lighter and more sensitive to lift. spar in tension and the upper spar in too short, and you lose velocity pulling compression. Shear force affects the out; dive too long, and you waste It is very important to recognize that entire spar from top to bottom, unlike altitude without gaining any more the numbers used in this note are for the bending-moment which has speed. The fastest had a fairly constant illustration only. A 200" sailplane maximum affect on the top and bottom altitude usage through the first three supporting only 4 lb. has both a of the spar and zero affect in the laps of the course, with of course halfspan and bending moment of 100 middle. Webbing can significantly extremely smooth consistent turns. which is easy to discuss in terms of increase the shear strength of the spar. percentages. However, it’s not weight Like the bending-moment, shear - A few pilots did split-S’s mid course, but maximum load that must be strength is maximum at the root, instead of the tight pylon turns most of considered, and this typically occurs where the entire lift generated by the the others did. I never figured out if during a winch launch. The breaking wing supports the plane, and is zero at this was better — it looked like they strength of the winch line is often the tip. not only bled off speed turning, but used, and values of 180 to 220 lb. are sacrificed altitude in the process. I not unusual. For the example in figure-4, with a don’t recall a run where it looked like rectangular wing having a constant lift this tactic paid off. Knowing the bending moment and distribution, the shear strength at the shear strength, and how they vary root is 2 lb. At midspan, it is half, or 1 - It’s not for the faint of heart. Any across the span, are important in wing lb. At 25" from the tip, it is 1/2 lb. It is altitude left at the end of the run is spar design. Spar design is a lengthy simply the total lift from the tip to that wasted, and we saw a lot of potentially discussion and whole books have been point on the span. With an accurate lift really fast runs blown in the last lap written on the subject (Strojnik, Alex, distribution, the shear strength across because there was altitude that wasn’t Low Power Laminar Aircraft Struc- the span can be accurately determined used; or there was altitude wasted tures, 1984). Spar design has also using the same methods used to early on in the run; or because the become very sophisticated with the use calculate bending-moment. Figure-6 elevator was over-controlled and the of various composite materials and shows the shear strengths for the wing plane bled off a good bunch of air- structures. And of course, Mark planforms shown in figure-5. speed. Drela’s Allegro is an excellent example. Thanks Ollie for all your help. My hat’s off to the guys that fly F3B. To simplify construction, it seems n common to use the same spar design I’m really impressed with their pilot- ing skills, and the amount of things they have to master to fly one round — let alone fly well and be competitive.
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Page 18 R/C Soaring Digest Classified Advertising Policy Classified ads are free of charge to subscribers provided the ad is personal in nature and does not refer to a business enterprise. Classified ads that refer to a business enterprise are charged $5.00/ T.W.I.T.T. month and are limited to a maximum of 40 words. The League of Silent Flight (LSF) is an international RCSD has neither the facilities or the staff to inves- (The Wing Is The Thing) fraternity of RC Soaring pilots who have earned the tigate advertising claims. However, please notify T.W.I.T.T. is a non-profit organization whose right to become members by achieving specific RCSD if any misrepresentation occurs. Personal membership seeks to promote the research goals in soaring flight. There are no dues. Once you ads are run for one month and are then deleted and development of flying wings and other qualify for membership you are in for life. automatically. If you have items that might be hard tailless aircraft by providing a forum for the to sell, you may run the ad for 2-3 months. exchange of ideas and experiences on an The LSF program consists of five “Achievement Levels”. These levels contain specific soaring tasks For Sale - Business international basis. T.W.I.T.T. is affiliated with The Hunsaker Foundation which is to be completed prior to advancement to the next PARACHUTES: $12.50 (includes S&H U.S.A.) dedicated to furthering education and level. Send check or money order to Dale King, 1111 research in a variety of disciplines. Full Send for your aspirant form, today: Highridge Drive, Wylie, TX 75098; (972) 475-8093. information package including one back issue of newsletter is $2.50 US ($3.00 foreign). League of Silent Flight Reference Material Subscription rates are $20.00 (US) or $30.00 c/o AMA Summary of Low-Speed Airfoil Data - Volume 3 is really (Foreign) per year for 12 issues. P.O. Box 3028 two volumes in one book. Michael Selig and his students T.W.I.T.T., P.O. Box 20430 Muncie, IN 47302-1028 U.S.A. couldn’t complete the book on series 3 before series 4 El Cajon, CA 92021 was well along, so decided to combine the two series in http://www.silentflight.org a single volume of 444 pages. This issue contains much that is new and interesting. The wind tunnel has been improved significantly and pitching moment measure- ment was added to its capability. 37 airfoils were tested. Sailplane Many had multiple tests with flaps or turbulation of Homebuilders various configurations. All now have the tested pitching Association (SHA) moment data included. Vol 3 is available for $35. Ship- ping in the USA add $6 for the postage and packaging costs. The international postal surcharge is $8 for surface A Division of the Soaring mail to anywhere, air mail to Europe $20, Asia/Africa Society of America $25, and the Pacific Rim $27. Volumes 1 (1995) and 2 The purpose of the (1996) are also available, as are computer disks contain- Sailplane Homebuilders ing the tabulated data from each test series. For more Association is to stimulate interest in full-size information contact: SoarTech, Herk Stokely, 1504 N. Horseshoe Circle, Virginia Beach, VA 23451 U.S.A., sailplane design and construction by phone (757) 428-8064, e-mail
There is a growing interest in scale soaring in the U.S. We are dedicated to all aspects of scale soaring. Scale soaring festivals and competitions all year. Source for information on plans, kits, accessories and other people interested in scale. For more information:
web site: www.soaringissa.org The Eastern Soaring League (ESL) is a confederation of Soaring Clubs, spread across the Mid- Atlantic and New England areas, committed to high-quality R/C Soaring competition. AMA Sanctioned soaring competitions provide the basis for ESL contests. Further guidelines are continuously developed and applied in a drive to achieve the highest quality competitions possible. Typical ESL competition weekends feature 7, or more, rounds per day with separate contests on Saturday and Sunday. Year-end champions are crowned in a two-class pilot skill structure providing competition opportunities for a large spectrum of pilots. Additionally, the ESL offers a Books by Martin Simons: "World's Vintage Rookie Of The Year program for introduction of new flyers to the joys of R/C Soaring competition. Sailplanes, 1908-45", "Slingsby Sailplanes", Continuing with the 20+ year tradition of extremely enjoyable flying, the 1999 season will include "German Air Attaché", "Sailplanes by Schweizer". Send inquiries to: Raul Blacksten, 14 weekend competitions in HLG, 2-M, F3J, F3B, and Unlimited soaring events. Come on out and P.O. Box 307, Maywood, CA 90270, try the ESL, make some new friends and enjoy camaraderie that can only be found amongst R/C
July 2002 Page 19 Page 20 R/C Soaring Digest