february, 2003 - rc soaring.com · the internet to the east coast in order to check out the web...
TRANSCRIPT
Page 1February 2003
February, 2003Vol. 20, No. 2
U.S.A. $3.50
R/C Soaring DigestPage 2
ABOUT RCSD
R/C Soaring Digest (RCSD) is a reader-written monthly publication for the R/C
sailplane enthusiast and has been publishedsince January, 1984. It is dedicated to sharingtechnical and educational information. Allmaterial contributed must be exclusive andoriginal and not infringe upon the copyrightsof others. It is the policy of RCSD to provideaccurate information. Please let us know ofany error that significantly affects themeaning of a story. Because we encouragenew ideas, the content of all articles, modeldesigns, press & news releases, etc., are theopinion of the author and may notnecessarily reflect those of RCSD. Weencourage anyone who wishes to obtainadditional information to contact the author.RCSD was founded by Jim Gray, lecturerand technical consultant.
RCSD should not be considered to endorseany advertised products or messagespertaining hereto. An advertising rate card isavailable for businesses, and clubs.
Feature ColumnistsBill & Bunny Kuhlman (B2),
Lee Murray, Tom Nagel, Mark Nankivil,Dave Register, Steve Savoie, Jerry Slates,
Greg Smith, Gordy Stahl
ArtworkGene Zika is the graphic artist
who designs the unique ZIKA clip art.
RCSD StaffJerry Slates - Editor/Technical EditorJudy Slates - Managing Editor, SubscriptionsLee Murray - RCSD Index/Database
(available on-line)Bill & Bunny Kuhlman - RCSD Web Masters
PayPal Coordinators
Copyright © 2003 R/C Soaring Digest.All rights reserved.
R/C Soaring Digest556 Funston Drive
Santa Rosa, CA 95407phone: (707) 578-7871
e-mail: [email protected]://www.b2streamlines.com/RCSD.html
OTHER GOOD STUFF
19 Classified Ads - New Products 4 Schedule of Special Events
Monthly Feature Photography & Web Version of the Printed Article (where appropriate)Highlights & Mailing Status of the Current IssueAbout 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 formatLinks to Organizations, Special Interest Groups & ClubsOn-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............................................................. "Butterfly and Moth Airbrushing Tutorial" by Joedy DruliaBookshelf Listings - A listing of recently published books of interest to aeromodelers.Complete RCSD Index, 1984-2001
RCSD ON THE WEBhttp://www.b2streamlines.com/RCSD.html
TABLE OF CONTENTS
3 "Soaring Site" ....................................................................................... Judy SlatesEditorial ................................................................................................... Eastern Soaring League
5 Skegs, Pros and Cons ............................................................................. Phil Bauer........................................................................................................................ The Skeg from Hell
6 "Tech Topics" ................................................................................... Dave RegisterTechnical Analysis & Design ....................................................................... Geometry of the Wing
10 "On The Wing..." ....................................................................... Bill & Bunny KuhlmanFlying Wing Design & Analysis ........................................................... Richter R/C Aircraft Design................................................................................................................ Weasel and miniWeasel
14 "Gordy's Travels" .................................................................................. Gordy StahlConstruction Techniques ........................................... Goop-hyde Your Foamies to a High Shine!
16 Radio Antenna Installation ............................................................... Dave Register............................................... Installing a Power Duck Antenna in the Futaba 9CHF Transmitter
13 Aerospace Composite Products8 Cavazos Sailplane Design9 CG Sugar Co.9 R/C Soaring Digest
Special Interest Groups19 Eastern Soaring League (ESL)19 International Scale Soaring Assoc.19 League of Silent Flight19 Sailplane Homebuilders Association19 T.W.I.T.T.19 Vintage Sailplane Association
Advertiser Index
Events15 Tangerine Soaring Championships, FL
Don't forget to check out the RCSD web pages each month.Cover photographs are always available for viewing, and
usually available for downloading, as well. Special article .pdf filesare frequently available for a limited time, and of course our webmasters update the highlights and status information of each issueas it becomes available.
Page 3February 2003
TheSoaring
Site
Weasel & miniWeasel
Alyssa, age seven and a pilotin her own right, holds the
completed Weasel andminiWeasel, from Richter R/CAircraft Design, for the camera.
Coverage of the designs, by Bill &Bunny Kuhlman, is included inthis issue.
Back Cover
2001 HLG Champ
Bruce Davidson DS’ing a newCarbon 3-meter Pike at the
Frankfort, Kentucky slope site.According to Gordy Stahl whosubmitted the photography,“The wind was about 17 mph,and he’s doing near 100 mph!”
Eastern Soaring League (ESL)
This month, we took a quick trip viathe internet to the east coast in
order to check out the web site for theEastern Soaring League. The sitedesign has changed significantly fromthe last visit. The home page openedup quickly with 6 card file typecategories: Introduction, Calendar,Standings, Newsletters, Resources, andOfficers.
For those of you interested in the ESLcontest schedule, where to go, andwho to contact, you can access the“Links to Organizations, SpecialInterest Groups, and Clubs” from theRCSD Main Web Page (http://www.b2streamlines.com/RCSD.html),and select the link to the ESL web site.While some of the contest dates and/or contact information will likelychange during the year, for those ofyou without on-line access, whatfollows are the introduction andcalendar pages as they are, today.
ESL Introduction
“The Eastern Soaring League is aRadio Control Soaring contest leagueorganized by soaring clubs spanningthe Eastern Seaboard from Virginia toMassachusetts. The season runs fromApril to October and concludes withan End-of-Season contest organized bythe ESL board.
“Membership in the ESL is free andautomatic when you enter an ESL-sanctioned contest. Members areorganized in Sportsman and Expertclasses.
“At the end of the contest seasonawards are given to the top ten per-formers in Sportsman and Expertclasses and to the individual whoseperformance has improved the mostsince the previous season.
“ESL contests, while competitive andincluding some of the best pilots in thecountry, are characterized by good
sportsmanship and a spirit of inclusionand coaching. If you are an R/Csoaring pilot of any skill level, and youhave the opportunity to attend an ESLcontest, we encourage you to to enterand enjoy two days of competitivesoaring fun.”
ESL 2003 Contest Schedule(Date, Contest,
Location, Contact)
May 3-4, BASS HLGBaltimore, MD AreaJohn [email protected]
May 17-18, SKSS 1Newark, DelawareBob [email protected](610) 363-1631
May 31-June 1, LASSLancaster, PAJohn [email protected](717) 394-3399
June 14-15, BRASSWaynesboro, VATom Broeski(540) [email protected]: Doug Barry
June 21-22, BARCS HL (not ESL)
June 27-28, LISF 1Syossett, Long IslandJohn [email protected](718) 767-1369
July 12-13, DBSFReading, PADale [email protected](610) 821-0977
July 19-26, AMA/LSF NATS
R/C Soaring DigestPage 4
Aug 2-3, SKSS 2Newark, DelawareBill [email protected](610) 255-4844
Aug 9-10, CRRC Soar-InSudbury, MAAnker [email protected](978) 897-1750
Aug 16-17, South Jersey (not ESL)John [email protected]
Aug 23-24, BASS OpenBaltimore, MD AreaJohn [email protected]
Sept 6-7, CASA OpenWarrenton, VASkip [email protected](301) 916-9574
Sept 13-14, South Jersey HL (not ESL)Evans Mill Pond, Marlton, NJJohn [email protected]
Sept 20-21, LISF 2Syossett, Long IslandJohn [email protected](718) 767-1369
Sept 27-28, CASA HL (not ESL)
Oct 4-5, ESL End of SeasonReading, PATom [email protected](814) 255-7418
Oct 10Down East Soaring Society HLG XC(not ESL), Wilson, NCContact: Oleg [email protected]: Dick [email protected]
Oct 11-12Down East Soaring Society HLGThermal Contest (not ESL), Wilson, NCContact: Oleg [email protected]: Dick [email protected]
Happy Flying!Judy Slates
SCHEDULE OF SPECIALEVENTS
March 15-16, 2003The Classic Mid-Winter Southern CaliforniaTorrey Pines Vintage Sailplane Regattahttp://www.agcsc.org
May 15-18, 2003Midwest Slope Challenge Wilson Lake, KSwww.alltel.net/~mwsc
May 24-25, 2003So. California PSS Festival Cajon Summit, CABrian Laird, [email protected]<ourworld.compuserve.com/homepages/slope_scale>
July 19-26, 2003AMA/LSF NATS Muncie, IN
October 10-11, 2003Texas National Tournament (TNT) Dallas, TXwww.SLNT.org
November 29-30, 2003Tangerine Soaring Orlando, FL Championshipswww.orlandobuzzards.org
Please send in yourscheduled 2003 events
as they become available!
Greetings,
Registration opens Friday, Feb. 14for the 10th annual Midwest SlopeChallenge.
Event dates are May 15-18 anddetails can be found at:
www.alltel.net/~mwsc
We’ve added a “What’s New”section to the web page, so you cantell at a glance what has beenupdated and when.
You’ll note that it’s now a four dayevent. We’ve sanctioned Thursdayto make it an “official” fun flyingday. No, you don’t have to show upa day earlier; it’s just a day of openflying with designated time slots forbreakable (non-EPP) planes. Basedon popular sentiment expressed lastyear, we now have two foamiecombat classes: flying wings andconventional planes. And the “Pole
of Doom” seems to have surviveda winter in the garage, so theWarbird race is back.
The Lucas Inn will once againserve as our race HQ and check-inlocation, but it’s no longer in themotel business. So if you wereaccustomed to staying there,you’d best be looking elsewhere.Lodging suggestions are on theweb page.
Other than that, it’s business asusual: combat, racing, fun flyingand Dave Urban’s prime rib. Weseem to have gotten some reallynice publicity from last year, sobeat the rush and get your entriesand frequencies reserved soon...
Hope to see you there,Loren
Announcement
Midwest Slope Challenge 2003
SPRIN G TIM
E!
ZIKA
Page 5February 2003
R/C Soaring DigestPage 6
Dave RegisterBartlesville, Oklahoma
TECH TOPICS
Geometry of the Wing
Over the past couple of columnswe’ve looked at planform optimi-
zation for hand launch gliders with aparticular emphasis on discus launch(DLG). Before leaving this topic, thereis one other planform related issue weneed to discuss. That’s the specificgeometry of the wing.
Although this seems a simple subject,it can be rather complex. To keep it tomanageable terms, we’ll restrictourselves to a Schuemann-Ellipse wingoutline.
By Schuemann-Ellipse we mean theoutline suggested in Wil Schuemann’sarticle in Soaring magazine. This articlecan be reviewed at the Scrollsanderweb site and is a very useful referencefor anyone looking at design issues.Schuemann’s suggested planform mostclosely resembles a quarter ellipse foreach wing with the trailing edgebisecting the long axis of the ellipse.
In general, an elliptical lift distributionalong the wing is considered to beoptimum for both induced drag andstall control. The key here is that we’retalking about an ideal elliptical liftdistribution, which is not necessarilythe same thing as an elliptical geom-etry distribution.
At the Reynolds numbers (Re) wherefull size aircraft operate (> a fewmillion), the lift distribution is reason-ably well estimated by the geometrydistribution of the wing. But at thescale we use in R/C, and in particularfor DLG, the situation is not as simple.
Consider the data of Figure 1 in whichwe’ve plotted X-Foil results for the liftcoefficient of the AG12 airfoil vs.Angle of Attack (AoA) for a number ofdifferent Re values. Add in the obser-vation that the polar analyses we’vedone in the past few months indicatesthat minimum sink for this airfoil willoccur at an angle of attack between 6and 8 degrees.
Page 7February 2003
Under these conditions the velocity ofour aircraft is ~ 16 ft/sec. If we’vedesigned an 8.25" root chord and a1.75" tip chord, the respective Re willbe ~ 70,000 and ~15,000 respectively.
Looking at Figure 1, note that the Clresponse for Re < 20,000 starts going topieces pretty quickly (XFoil Results). Ifthese chords represent our best fit toan elliptical geometry, then the totallift at the tip needs to be evaluated
very carefully.
Another observation to note is that theonset of stall is a degree or so lower forthe lower Re. This fact, coupled withthe lower than optimum lift capabilityat the tip, will almost guarantee tipstall problems if the wing is notdesigned carefully.
How do you fix this problem? Prob-ably the only correct way is to go build
a bunch of wings and pick out the onethat works best. Since we’re intomodeling our models here, I’ll outlinea technique I’ve used to get a goodstarting point for the problem. Thereare much more theoretical ways toapproach these issues but the generalconsiderations which follow haveworked well for me.
First of all, one way to address thelower stall angle at the wing tip is touse some washout. A degree is aboutright for small wings. At larger chords(open class ships), very little, if any,washout is really needed.
Another way to compensate for a lowCl at low Re is to increase the localchord. Since the lift distribution isdetermined by the product of the localCl and the local chord, when Cl drops,increase the chord to compensate.
This gets into an iterative problembecause increasing the chord increasethe local Re which increases the localCl which means you don’t need to useas much chord as you first thoughtwhich reduces the local Cl a bitwhich...
Let’s not get too hung up on this. Iprefer to take only the first iterationwhich will provide some excess loadcapacity at the tip. If we’re making anerror here, it’s on the safe side and, aswe’ll see, the correction is not too largefor most practical dimensions.
I’m also going to limit this discussionto the things I can do in my shop. I canonly cut simple, straight tapered cores.Those beautifully contoured wingplanforms that come from the CAD-CAM machines are out of my league.For DLG, a double taper wing is aboutas complicated as I’ll go. For 2M I’ll doa triple taper while for open class aquad taper is more appealing.
I developed an Excel spreadsheet a fewyears ago to do this analysis. For mostpurposes, the Lift-Roll spreadsheet isequally handy. However, the Solvermacro in Excel can seek the propersolution, which you have to manuallydetermine in Lift-Roll.
As an example, in Table 1 I’ve listedseveral double taper fits for wings withan aspect ratio (AR) of 9 using myspreadsheet and the Solver macro. Thefirst of these (Ellipse) is a best fit to a
R/C Soaring DigestPage 8
simple elliptical geometry. Plug thesevalues into Lift-Roll and you’ll find it’sas close an approximation to theelliptical distribution as you’re goingto get.
I’ve also included in Table 1 theoptimized result for a double taperwing with 1 degree of washout (twist).The AR is again 9. This planformcontains 0.5 degrees of twist in themain panel and 0.5 degrees of twist inthe tip. Again, plugging it into Lift-Rollwill produce an optimized distributionfor this planform configuration.
What we have not yet done is includethe compensation for the low tip Re.This compensation has to include boththe drop off in the local slope of the liftvs angle of attack (AoA) curve and theplateau effect at around 7 to 9 degreesdue to the onset of stall. For open classships, these effects are minimal. ForDLG, they can be significant.
For this part of the analysis, it’sconvenient to develop a better pictureof the Cl response vs Re for a fixedAoA. As previously noted, the stan-dard Cl vs AoA has been shown inFigure 1 for a number of Re values. InFigure 2, we’ve re-plotted that data asCl vs Re at a fixed AoA.
In order to apply this result to ourplanform model, it’s useful to have aclosed form expression for this data toplug into our spreadsheet model. Asimple formula that provides a goodemulation of these data at 7.5 degreesAoA is shown in Figure 3. I chose 7.5degrees since it’s close to the AoA forminimum sink and also represents avalue which begins to catch the affectsof stall onset. Proper compensationhere should be useful for minimizingthe tendency to tip stall.
If we apply our Cl(Re) model for AoA= 7.5 degrees to our double taperplanform with twist, we get the valuesshown as the final entry in Table 1. Asummary of the original ellipticalplanform, elliptical planform withtwist, and the final planform with twistand Re correction is shown in Figure 4.
If you plug the results of the lastcalculation into Lift-Roll, you’ll findthat it appears to overestimate the liftin the tip section and underestimate itin the main. As noted, this is becauseLift-Roll does not include Re correc-tions. However, the method we’ve
used (first iteration only) will providea slight lift excess in the tip even whenRe correction is applied.
This is actually the safer direction for adesign since you WANT the stall toinitiate at the root and proceed to thetip. That’s a much better condition andshould lead to a straight-ahead stall. Ifthe planform were biased towards atip stall, the imperfections that arealways present in our building meth-ods will assure that one tip will let gobefore the other. This leads to an uglyspiral stall tendency. If that happenstoo close to the ground, the results canbe unfortunate.
One more comment on twist (orwashout). The specific value used willdepend on the nature of the wing andairfoil (dihedral, polyhedral, blendingof the airfoil, etc.). For the present case,Cl vs Re for the root and tip sections(with twist) are plotted in Figure 5.Note that the washout used has placedthe stall AoA at about the same pointfor both the root and the tip. Comparethat to the original (untwisted) resultin Figure 1. Without twist, it is verylikely that the tip section will stallbefore the root even with the widerchord developed to correct for Reresponse.
Another way to achieve this sameobjective would be to use a differenttip airfoil - perhaps one that generated
higher lift, or more effectively handledthe transition bubble so flow attach-ment could be better maintained nearthe stall AoA. Using the Ag12-Ag13-Ag14 sequence might be a useful wayto produce this result. The specific Reand twist compensation rules wouldbe a little different than we’ve devel-oped here.
The basic point of all this is that thedesign of the planform must includesome consideration for the stallpotential of the wing and the actual liftdistribution desired at or near mini-mum sink. That’s a complex buttractable problem. The best results arefound by starting with a good estimateand then refining it with real flyingexperience. n
Page 9February 2003
R/C Soaring Digest556 Funston Drive
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e-mail: [email protected]://www.b2streamlines.com/RCSD.html
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R/C Soaring Digest (RCSD) is a reader-written monthly publication for theR/C sailplane enthusiast. Published since 1984, RCSD is dedicated to thesharing of technical and educational information related to R/C soaring.
RCSD encourages new ideas, thereby creating a forum where modelers canexchange concepts and share findings, from theory to practical application.Article topics include design and construction of RC sailplanes, kit reviews,airfoil data, sources of hard to find items, and discussions of various flyingtechniques, to name just a few. Photos and illustrations are always inabundance.
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R/C Soaring DigestPage 10
This photo provides a good view of the fin and controlsurface geometry. These are very compact aircraft.
Alyssa, age seven and a pilot in her ownright, braves the rain (hence the flash-lit
rain drop) and holds the completedWeasel and miniWeasel for the camera.
The completed Weasel and miniWeasel on theglass building surface. The fuselage pods do notextend much beyond the apex of the wings: 2-1/
4" and 1-1/2", respectively.
[email protected]://www.b2streamlines.com
Richter R/C Aircraft DesignWeasel and miniWeasel
Our most recent kit review waswritten about Trick R/C’s original
Zagi, published in the January 1997issue of RCSD. Yes, the original Zagi— the one made almost entirely ofstyrofoam. A number of advancementsin construction technology have comeon the scene since then, but we haven’thad the inclination or the opportunityto construct a tailless glider made ofEPP (expanded polypropylene). All ofthat changed when we heard aboutMichael Richter’s Weasel andminiWeasel.
The Weasel and miniWeasel arrived in
separate boxes. Both wereextremely well packaged andsurvived postal delivery inabsolutely pristine condition.Michael has managed tonestle the wing cores,fuselage, elevons, hardwarepackage and packing tape instandard boxes in such waythat things don’t rattle andone part doesn’t damageanother.
The Weasel
“The Weasel is a small,lightweight flying wing thatis extremely maneuverable,yet forgiving. Its uniqueshape and special blend ofairfoils gives it a wide speedrange and great stability. Thehigh lift design allows it tohover in a light headwind,while the pilot maintains fullcontrol even at this lowairspeed.
“The Weasel is extremely aerobatic inthe hands of an accomplished pilot,but has enough stability for thebeginner. Its small size, light weight,and durability make it a perfectcontender for light combat on theslope. The Weasel is agile and recoversquickly from maneuvers at lowaltitudes. This little glider is an abso-lute joy to hand catch, thanks to itslight weight and low stall speed. Allthis amounts to an aircraft that is purefun to fly.”
The Weasel has a wing span of 36inches and requires a radio withelevon mixing and dual rates, twomicro servos, a mini receiver, and anappropriate NiCd battery pack. Therecommended flight pack includes twoHS-81 servos, a Hitec 555 receiver, anda 4.8V 270 mAh battery pack. We usedHS-80 servos, which fit perfectly in thepre-cut cavities, an FMA M5 receiverand a JR 250 mAh flat battery pack.
Page 11February 2003
The underside of the miniWeasel. Allof the hardware for the controllinkages is included in the kit.
The belly of the Weasel, showingthe empty battery pack and
receiver cavities.
The Weasel and miniWeasel boxes, prettymuch as they arrived. Some of the itemshave been moved so they’re more easilyseen, but you should get an idea of the
great packaging job Michael does.
Kit Contents
EPP foam wing with pre-cutcavities for servos
EPP foam nose pod with pre-cutcavities for battery pack andreceiver
Coroplast™ finbalsa elevonsspruce sparsplywood wing joinerCoroplast battery and receiver
coverplastic tubes for pushrod system
actually done touch-and-goesoff of their own heads! Rolls,loops, inverted flying, theminiWeasel does them all.
“You may think that this smallglider would be difficult to fly,but it is actually not. It takes alittle time to get used to theincreased sensitivity of thecontrols, but it shares the samehands-off stability of its largerbrother, making it relativelyeasy to fly.
“Discus launching (alsoknown as side-arm-launching)with this glider is great;simply grab a wing tip at the
is set up to take two Cirrus CS-10bbMolecular servos, Cirrus MRX-4 sub-micro receiver, and a Wattage 4.8V 150mAh NiCd battery. We found MPIMX-30 micro-servos to be the exactsize for the pre-cut servo wells. Astandard Batteries America 150 mAh(N) battery pack fit with plenty ofroom to spare, but we had someproblems fitting the M5 receiver in thismodel. We’ll take a look at this diffi-culty in greater detail in a moment.
Kit Contents
EPP foam wing set with pre-cutcavities for servos
EPP foam nose pod with pre-cut
Du-bro control hornsDu-bro clevisesroll of colored tape for coveringconstruction manual
The miniWeasel
“The miniWeasel is a miniaturizedversion of the original Weasel slopeglider, as the name implies. Its smallersize and light weight make it ex-tremely maneuverable. We think thatthis glider is a blast to fly in smallplaces, close to the ground. Its lowwing loading allows it to fly in thermalconditions and its special blend ofairfoils makes it fast for its size. (If youreally want to keep the weight downfor thermal flying we recommend thatyou not cover the elevons and fin withtape; however cover them if you planto fly mostly on the slope, as this willmake them more durable.) Thisairplane really comes alive on theslope in 5 to 15 m.p.h. winds. You willhave hours of fun flying this littleglider, literally in your face — we have
spar with three fingers andfling it into the wind. You willbe amazed at the altitude youcan get from such a launch.This type of launch enablesyou to fly on flat fields, wherethermal updrafts are the mainsource of lift. You can fly thisglider practically anywhere.Take miniWeasel along withyou on a hike, a road trip, tothe local slope, to a nearbyschool yard, or simply give it a fling inyour own backyard. Get a couple ofthem together on the slope and pre-pare for insane miniWeasel combat!This glider has been known to makepeople’s heads spin.”
The suggested radio gear for the 24inch span miniWeasel includes atransmitter with elevon mixing anddual rates, two sub-micro servos, asub-micro receiver, and a 50 to 150mAh NiCd battery pack. The airframe
cavities for battery pack andreceiver
Zepron fin and elevonsbasswood spars3/16" x 3/8" balsa wing joiner3/32" sq. x 5" long basswood fin
reinforcementCoroplast battery and receiver
covermusic wire pushrod materialDu-bro Micro control hornsplywood control horn mounting
platesDu-bro Mini EZ connectorsDu-bro micro EZ linksroll of colored tape for coveringconstruction manual
Construction hints and tips
Construction manuals for both aircraftare available on-line on the Richter R/C Aircraft Design web site<www.flyweasel.com>. They’re at<http://www.flyweasel.com/
R/C Soaring DigestPage 12
Another of Michael Richter’s designs.We’re still trying to talk him into kitting
this ‘wing! It just looks soooo cool.
instruction_files/weaselinstructions_1.pdf> 610K, and<http://www.flyweasel.com/instruction_files/miniweasel_instructions.pdf> 1.2 MB.While you’re there, make sure youdownload all of the cool Weasel andminiWeasel movies.
A few suggestions which may helpduring construction of the Weasel, inorder roughly parallel to the construc-tion manual:
• Drip small quantities of epoxy intothe spar slots, then use a 1/8th inchdowel, held at 45 degrees along thelength of the slot, to spread the epoxyin the slot. Run the dowel back andforth in the slot in a dragging motion.This wipes epoxy downward into theslot while covering the sides andbottom, and tends to put a bead in thelower corners of the slot.
• Rather than covering the plywoodjoiner with epoxy, and having epoxystick to your gloves and make ageneral mess, bend the wing over theedge of the building table to open theslot in the foam. Drop some epoxy inthe slot, them take a wooden coffee stirstick, again held at 45 degrees to thelength of the slot, to spread the epoxyacross the vertical sides of the slot. Theplywood joiner can then be easilyinserted.
• We applied a single coat of dope onthe elevons, lightly sanded the surfaceswith fine sand paper, then used theincluded packing tape to make thehinges, as outlined in the instructions.Looks good and works as it should.Not sure if we saved any weight, but itdid give us the opportunity to exerciseour olfactory nerves.
• The directions explain how to sprayon the 3M 77 adhesive and wait beforeapplying the tape covering. We waitedovernight and applied the top cover-ing, but ended up tearing it all offbecause it just would not stick for morethan a few minutes before comingloose. Fortunately, taking it off waseasy. We applied a very light coat of3M 77 adhesive over what was alreadythere, then covered, and everything isfine.
• We build on glass (an old slidingglass door) and used a smaller piece ofglass to fully support the wing at the
proper angle (one inch at the wing tip)while placing the dihedral brace. Aftercovering was completed, however, thedihedral was down to a fraction of aninch. In retrospect, we may have put asmall amount of tension on the tapewhile covering the lower surface.Michael said some people are buildingthe Weasel with no dihedral at all, withno adverse effects, but we were morecareful when covering the miniWeasel,and the dihedral turned out exactly asspecified.
• The instructions mention that lightlysanding the covering material on thefuselage should be done before apply-ing the double-sided fabric tape. Thesame should be done to the lowersurface of the wing where that sametape is expected to stick. The double-sided tape supplied in the kit stickswonderfully well — enough that wedid not bother to use the crisscrosstape over the fuselage and leadingedge.
• We used a very light coating ofHousehold Goop to glue the fin intoposition rather than using the tapingmethod. This technique was picked upwhile our granddaughter Alyssa wasbuilding her MAD Highlander.
Other than some of the tricks we usedpreviously on the Weasel, we did makea few changes to the miniWeaselconstruction process.
• We didn’t add the strapping tape tothe wing tip, as we have no plans todiscus launch.
• The fuselage is supposed to beattached to the wing by means of thetape covering material. We used Goopinstead. After the exposed portion ofthe bottom wing surface was covered,a length of tape was folded along itslength and applied to the fuselage sothat the folded part would attach to thelower surface of the wing. The creditcard idea, as described in the instruc-tions, works like a charm!
• We did not use the full tape width toattach the basswood strip to thebottom of the fin, but rather cut thetape in half along its length and usedonly one half. Goop was used again tomount the fin in the fuselage slot.
A couple of suggestions which applyto both the Weasel and the miniWeasel,
as well as other foam-based aircraft:
• 3M 77 and packing tape do notreally make the ideal covering mate-rial. One trick we use to smooth thingsout is to set our Goldberg coveringiron to “2” and use the low heat to getthe tape to stick. Your thermostatsetting may vary. This tightens tapewhich is slightly slack and worksespecially well in areas where the tapeseems to resist sticking.
• The trick with Goop is to use verythin coats — just enough to wet theporous surface. When used in this waythe Goop vehicle, toluene, evaporatesso fast that the initial bond is verymuch like working with contactcement. EPP foam lets enough evapo-ration to take place that the joint isnearly fully cured in a half hour or so.
After we had the Weasel covered,Michael wrote and made the followingsuggestion,
“I forgot to mention a trick that Irecently learned regarding tapingthe wings. The problem with tapedwings is that the edges always tendto pull away when a little dirt getsunder the tape. This makes forsome really unsightly wing tips.Instead of using Goop to seal thetape edges, as some people do, goto a home improvement or craftstore and look for stretchableplastic tape — 3M makes it in 3/4”rolls in a variety of colors. This isgreat because you can match thetape with your color scheme. Ithink it is called 3M Plastic Tape.This tape has NO filaments in itand has the stretchiness of heavy
Page 13February 2003
duty black electrical tape (youcould use black electrical tape ifyour plane is black). Simply takethis tape and stretch a single piecealong the leading edge and aroundthe wing tip. It will conformbeautifully to the compound curveand will seal all the small packingtape seams. It is quick, clean, andsimple.”
This works! And if the tape deterio-rates beyond usefulness, it’s a simplematter to pull it off and apply a freshstrip.
Between both aircraft, the only prob-lem we had is with the receiverinstallation in the miniWeasel. The M5would be a nice fit with a bit of roomto spare if only it had end plugs. Theservo plugs stick up because of thevertical plug orientation, and theassociated wiring bends the Coroplasthatch below the bottom of the fuselageabout 1/8th inch. We thought aboutmodifying the servo plugs so theydon’t stick up so far, or waiting for anend plug M5 to be released. (We hearFMA is considering putting out an endplug version.) In the end, we simplytook out our Dremel tool and routedout the bottom of the receiver cavityuntil we were slightly into the wing.Now everything fits and the Coroplastcover is flush with the fuselage foam.
Construction time for the Weasel isprojected to be five to ten hours.Despite the noted changes in thebuilding process and the usual unex-pected minor snags, our time was justover seven hours. The miniWeaselbuilds faster. Actual construction timefor it was exactly as estimated — fivehours.
The balance point for the Weasel isdirectly on the wing joiner. Elevatorfunction is set up for 3/16th to 3/8thinch up and down, aileron function for1/2 inch to 3/4 inch up and down. Weadjusted the servo travel at the trans-mitter so that all control throws werein the middle of the suggested ranges.Our Weasel weighs 310.5 gm, 11ounces, ready to fly. About a halfounce of nose weight was needed toget the CG right. This is closer to theminimum weight than the maximum,and we’re pleased with the way thingsturned out. It looks and flies great!
The CG location for the miniWeasel is 4-
15/16 inch forward of the hinge line.The instructions state that the locationis critical on an airplane this small, sowe quickly manufactured a balancestand. The recommended deflectionsare 3/16 inch up and down for eleva-tor and 5/8 inch up and down foraileron. Our miniWeasel came in at 127gm, 4.5 ounces, ready to fly. An ounceof lead was needed in the nose toachieve the correct CG location. This isthe maximum suggested overall flyingweight, so we’re glad we didn’t addthe cross of fiber tape on the wing tip!The miniWeasel flies extremely well, abit faster than expected, and is veryresponsive.
Test flying both models was incrediblyeasy and went extremely well. Wecould not have been more pleased withinitial flights. The CG locations andcontrol throws provided in the instruc-tion manuals are right on! Amazing.This is the first time in our experiencethat the provided set-up instructionshave actually been accurate!
Weather here in the Pacific Northwestis in one of its weird states again thisyear. It’s windy when it’s raining andcalm when it’s not, so slope flying toany great extent has so far not beenpossible, but hand launches over flatground have demonstrated a lot ofpotential, and it looks like the fun toprice ratio is going to be extremelyhigh.
Our thanks to Michael Richter forsupplying the kits for these reviewsand for being incredibly responsive toour suggestions and feedback. We’restill trying to talk him into kitting someof his other designs, like the very coolswept forward ’wing pictured here!
Suggestions for future columns can beaddressed to us at either P.O. Box 975,Olalla WA 98359-0975, or<[email protected]>.
Sources:
Richter R/C Aircraft DesignMichael Richter1250 Northridge RdSanta Barbara CA 93105Phone/FAX: (805) 687-4435Web site: <http://www.flyweasel.com>E-mail: [email protected]
Prices:Weasel $50 plus packing and postageminiWeasel $35 plus packing andpostageOrders may be placed on theflyweasel.com web site.
FMA Direct5716-A Industry LaneFrederick MD 21704Sales: (800) 343-2934Support: (301) 668-7615FAX: 301) 668-7619<http://fmadirect.com>
Batteries America, 2211-D ParviewRoad, Middleton WI 53562Orders: (800) 308-4805, Inquiries: (608)831-3443, FAX: (608) 831-1082Web site: <http://www.batteriesamerica.com>E-mail: [email protected]
n
R/C Soaring DigestPage 14
GORDY’S TRAVELS
Gordy StahlLouisville, [email protected]
”Goop-hyde Your Foamiesto a High Shine!”
On one of my recent trips, I wokeone night late in my motel room
and screamed out into the darkness,”I’m going to build my EPP Moths!”...Then went back to sleep.
So inspired, I went to work at re-searching the construction informationand the web site for North CountryFlying Machines on the Moth.
http://www.northcountyflyingmachines.com
In case you didn’t read the review inRCSD, May 2002 issue, the Moth is a48” EPP tailless Foamie that hasproven to be a rocket Dynamic Soaring(DS) machine that flies in the lightestslope lift, often working the wispiestthermals to the sky. It has such anincredible speed range that it hasdistinguished itself as a most amazingFoamie. The Moth is not a cranked-plank Zagi-esque combat ship; insteadit has more fighter jet lines, with astraight leading edge and taperedtrailing edge, a fuselage and promi-nent vertical stabilizer. If you haven’tbeen to the web site to see photos andDS video of this little ship, you arereally missing out.
Enough of that! Mostly what I foundin my construction research was somewell proven innovations. The numberone trick was the use of thinnedMarine Goop. (Marine Goop is in apurple tube and claims greater UVresistance than the other Goop prod-ucts. It is available at all Home Depotstores.)
The Goop is thinned with Toluene, astinky solvent found also at HD, but inthe paint department. Getting theGoop to accept thinning takes somestirring, mashing and more stirring.You will swear that it’s not going tohappen, but stir on young soldier, as itdoes work!
Anyway, NCFM suggests coating theEPP fuselage with Goop to create atough skin or hyde to protect the foamand as part of the finishing process.
I decided to give it a shot and learned afew things in the process not men-tioned on the web site tips. First thingwas amazement! The Goop cures to anincredibly clear and ultra glossyfinish... And it goes right over EPP thathas been painted with enamel - paintslike Krylon! I then found that youcould actually create an EPP Foamiefuselage that looked like molded glass... Only shinier!
Here’s the step by step:
Final shape the foam fuse with screentype sanding paper, usually used fordrywall finishing. 80 grit is good forthis.
Next wipe on some light spackle to fillall the dents in the foam. Then sandwith a light touch so as not to com-press the surface while sanding. If youwant you can do this a few times toreally fill in the foam.
Next mix up some thinned Goop to aconsistency of runny pudding. Stir theheck out of it to make sure it’s notlumpy. You will stir it to almost afoamy consistency. Then using a 1”brush, paint a good coat onto the fuse.You’ll want to let it dry at least 24hours, then sand it with the screenlightly and then coat it again with thesame consistency.
This time when it dries, use some 220sandpaper to get it fairly smooth. At
Page 15February 2003
this point you can decide if anothercoat is desired or, if it is fairly smooth,you are ready for paint.
Keep in mind that Goop-hyde is goingto be seriously clear, so any paintingyou do will show through. This is justlike the clear protective coat on yourcar!
You can paint canopy lines, letters,numbers, etc., and it will seem like it’son the outside but won’t rub off. Anyenamel, like Krylon and paint pens, isfine.
Let it all dry over night and then getready for some more Goop coats. Thistime thin the Goop to the consistencyof thin paint and coat the whole fuseagain. You want to be sure to coat theentire fuse, inside wing holes, RXcompartments - everywhere, in orderto avoid creating weak spots.
Don’t be afraid to sand and recoat, as itwill end up clear. Also if you need toadd some paint over the Goop coats,not a problem!!!
What is a problem is the smell! TheGoop coat STINKS, especially if it’scold outside. You can heat cure thesolvents in the curing fuse with a heatgun or just let it sit for a few weeks.When I did mine it was less than 20degrees in the garage. It was greatfrom the stand point that the Goopdidn’t harden and ball up when Iwanted to re-stroke some spots withthe brush.
By the way, if you soak some papertowels with the Toluene, you can washthe Goop out of the brush for reuse.Don’t throw the unused Goop mixout!!! If you have a wood top that youwould like ‘sealed’, pour the rest on itand just sort of brush it or wipe it on!
Your fuse will stink for quite awhile ifit’s cold, as in weeks. So plan onstoring it outside for awhile or the wifewill get nuts on you!
Most Foamie kits recommend packingtape for strengthening the EPP fuse-lage. I believe that you could first fillwith the spackle, coat with your Goop-hyde mix, sand, 3m spray glue, do thepacking tape thing, then Goop-hyderight over the tape before painting andfinish-Gooping.
This process has some other interesting
possibilities! For instance, for provid-ing a protective ‘skin’ on the bottomnoses of glass fuselages, to keep themfrom getting scratched up on grittylandings!
This process isn’t rocket science... So,there isn’t a lot to ask about it. Myadvice is mix some up in a plastic cup,using something blunt like a popsiclestick, and paint some EPP.
If it is hot out, the solvents will dryquickly and your Goop-hyde mix willstart getting sticky and messy quick.I don’t know if you can store thinnedGoop in a glass, sealed jar, but youcould try it!
Don’t even bother considering weight!The benefits far outweigh any weightadded to the airframe. Functionalweight is a good thing!
Did I mention that you will not believe
how shiny your Foamie will be!!!! Soshiny that you can’t look at it in thesun... Not kidding.
Give the Goop thing a try if you arebuilding a PSS sloper or a Moth. Youwill notice that I refer to it as Goop-hyde, which means that it creates adurable skin that will help the EPPresist tears on impact and compres-sion, too. So coating the leading edgesand tips of Foamie wings is a reallygood idea.
3m spray glue is still needed for Ultra-Coat or taping over the Goop-Hydeand EPP foam, so nothing new there!
I’ll be checking your Foamies forGoop-hyde when my travels bring meto your slope, so don’t brush me off...Instead, brush some ‘Goop-hyde’ on!
See you on the road! n
R/C Soaring DigestPage 16
Figure 1 Figure 2
For years I’ve used a Power Duck(aka Rubber Ducky) antenna on my
Futaba 7UGFS. After mangling theoriginal antenna into the ground abunch of times, something had to give.
After converting my Fut 7 some fiveyears ago, I’ve never had a hit or lossof signal. I’ve flown open ships to thelimits of my eyesight (actually, beyondjust a bit - but I had a great spotter thattime!). Since flying DLG I just don’t seehow you can launch well with thatlong telescoping antenna whippingaround all the time.
When I recently went to a 9C, the oldtelescoping antenna caused all thesame problems. A quick call to GeorgeVoss (Soaring Specialties: http://www.soaringspecialties.com/) and ahot pink Power Duck was on the way.
Installation of this antenna is verysimple and requires maybe threeminutes of work on the Futaba 9CHF.One must note the disclaimers:
1) This voids the warranty on yourTransmitter, and
2) Since this is not an OEM antenna,it is not AMA legal and can besubject to disqualification at AMAsanctioned meets.
That said, I’ve never had a problem sofar at contests or with range andoperation. Once you’ve popped outyour Tx batteries, it’s hard to dodamage to your Tx while installing themounting post.
If you’re thinking of doing this conver-sion, but might be intimidated by thethought of getting into the innards ofyour Tx, here’s some notes and pic-tures of what to do.
Figure 1:
1) Remove the frequency module (justpops out by squeezing the endtabs).
2) Remove the battery (remove thebattery cover, pull out the pack andunplug).
3) Undo the four screws on the backpanel and lift off the panel. There
Installing A Power Duck Antenna In The Futaba 9CHF Transmitter
By Dave RegisterBartlesville, Oklahoma
are no wires or attachments to theback panel.
Figure 2:
4) Lift of the board that accepts thefrequency module. It has noretaining screws or clamps, it justlifts off and can be set to one sidedue to the ample wiring harness.
5) Unscrew the antenna from thebase bolt and remove it.
Figure 3:
6) Screw in the top fitting (BNCtype) with the washer on theinside. The hole for the antennahas a slight inward lip on it onthe outer surface so the BNCconnector will move around a bitat first.
7) Tighten up the retaining bolt onthe antenna connector. About 1/6turn past hand tight is aboutright. The BNC mount for theantenna no longer rocks in theseat now.
Page 17February 2003
Figure 4
Figure 3
8) Undo the nut on the antennawire connecting bolt and put thewire from the BNC connector onthe inside of the screw. Replacethe nut and tighten it up. At thispoint, the original white wireshould be in its original positionwhile the orange wire from theBNC mount is on the oppositeside of the slotted plastic retain-ing tab.
9) Put the board (from step 4) backin place. Make sure the littlealignment blocks are in theirproper positions in the board. Putthe cover back on and tightendown the 4 screws. Reinsert thebattery and plug.
10) Plug the RF module back into therear of the case. Be a little carefuldoing this as the pins are verylong and easy to misalign. Ifthere’s ANY resistance then thepins aren’t aligned. Back up,check the pin spacing andstraightness and try again.
Figure 4:
That‘s it. Maybe took all of threeminutes. Your Power Duck is up andrunning. Range check as recom-mended with all of your planes.
(Anyone out there know what BNCstands for? Nuclear physicists need notreply.)
n
R/C Soaring DigestPage 18
Page 19February 2003
T.W.I.T.T.(The Wing Is The Thing)
T.W.I.T.T. is a non-profit organization whosemembership seeks to promote the researchand development of flying wings and othertailless aircraft by providing a forum for theexchange of ideas and experiences on aninternational basis. T.W.I.T.T. is affiliatedwith The Hunsaker Foundation which isdedicated to furthering education andresearch in a variety of disciplines. Fullinformation package including one back issueof newsletter is $2.50 US ($3.00 foreign).Subscription rates are $20.00 (US) or $30.00(Foreign) per year for 12 issues.
T.W.I.T.T., P.O. Box 20430El Cajon, CA 92021
www.twitt.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 arecontinuously developed and applied in a drive to achieve the highest quality competitionspossible.Typical ESL competition weekends feature 7, or more, rounds per day with separate contests onSaturday and Sunday. Year-end champions are crowned in a two-class pilot skill structureproviding competition opportunities for a large spectrum of pilots. Additionally, the ESL offers aRookie Of The Year program for introduction of new flyers to the joys of R/C Soaring competition.Continuing with the 20+ year tradition of extremely enjoyable flying, the 1999 season will include14 weekend competitions in HLG, 2-M, F3J, F3B, and Unlimited soaring events. Come on out andtry the ESL, make some new friends and enjoy camaraderie that can only be found amongst R/CSoaring enthusiasts!
ESL Web Site: http://www.e-s-l.org
The League of Silent Flight (LSF) is an internationalfraternity of RC Soaring pilots who have earned theright to become members by achieving specificgoals in soaring flight. There are no dues. Once youqualify for membership you are in for life.The LSF program consists of five “AchievementLevels”. These levels contain specific soaring tasksto be completed prior to advancement to the nextlevel.Send for your aspirant form, today:
League of Silent Flightc/o AMA
P.O. Box 3028Muncie, IN 47302-1028 U.S.A.
http://www.silentflight.org
SailplaneHomebuilders
Association (SHA)
A Division of the SoaringSociety of America
The purpose of theSailplane HomebuildersAssociation is to stimulate interest in full-sizesailplane design and construction byhomebuilders. To establish classes,standards, categories, where applicable. Todesiminate information relating to constructiontechniques, materials, theory and relatedtopics. To give recognition for noteworthydesigns and accomplishments.SHA publishes the bi-monthly SailplaneBuilder newsletter. Membership cost: $15U.S. Student (3rd Class Mail), $21 U.S. RegularMembership (3rd Class Mail), $30 U.S. RegularMembership (1st Class Mail), $29 for All OtherCountries (Surface Mail).Sailplane Homebuilders Association
Dan Armstrong, Sec./Treas.21100 Angel Street
Tehachapi, CA 93561 U.S.A.
Classified Advertising PolicyClassified ads are free of charge to subscribersprovided the ad is personal in nature and does notrefer to a business enterprise. Classified ads thatrefer to a business enterprise are charged $5.00/month and are limited to a maximum of 40 words.RCSD has neither the facilities or the staff to inves-tigate advertising claims. However, please notifyRCSD if any misrepresentation occurs. Personalads are run for one month and are then deletedautomatically. If you have items that might be hardto sell, you may run the ad for 2-3 months.
For Sale - Business
PARACHUTES: $12.50 (includes S&H U.S.A.)Send check or money order to Dale King, 1111Highridge Drive, Wylie, TX 75098; (972) 475-8093.
Summary of Low-Speed Airfoil Data - Volume 3 is reallytwo volumes in one book. Michael Selig and his studentscouldn’t complete the book on series 3 before series 4was well along, so decided to combine the two series ina single volume of 444 pages. This issue contains muchthat is new and interesting. The wind tunnel has beenimproved significantly and pitching moment measure-ment was added to its capability. 37 airfoils were tested.Many had multiple tests with flaps or turbulation ofvarious configurations. All now have the tested pitchingmoment data included. Vol 3 is available for $35. Ship-ping in the USA add $6 for the postage and packagingcosts. The international postal surcharge is $8 for surfacemail to anywhere, air mail to Europe $20, Asia/Africa$25, and the Pacific Rim $27. Volumes 1 (1995) and 2(1996) are also available, as are computer disks contain-ing the tabulated data from each test series. For moreinformation contact: SoarTech, Herk Stokely, 1504N. Horseshoe Circle, Virginia Beach, VA 23451 U.S.A.,phone (757) 428-8064, e-mail <[email protected]>.
Reference Material
BBS/Internet
Internet soaring mailing listserve linking hundreds ofsoaring pilots worldwide. Send msg. containing theword "subscribe" to [email protected]. The"digestified" version that combines all msgs. each dayinto one msg. is recommended for dial-up users on theInternet, AOL, CIS, etc. Subscribe using [email protected]. Post msgs. [email protected]. For more info., contact MichaelLachowski at [email protected].
Books by Martin Simons: "World's VintageSailplanes, 1908-45", "Slingsby Sailplanes","German Air Attaché", "Sailplanes bySchweizer". Send inquiries to: Raul Blacksten,P.O. Box 307, Maywood, CA 90270,<[email protected]>. To view summary ofbook info.: http://home.earthlink.net/~raulb
There is a growing interest in scale soaring inthe U.S. We are dedicated to all aspects ofscale soaring. Scale soaring festivals andcompetitions all year. Source for informationon plans, kits, accessories and other peopleinterested in scale. For more information:
web site: www.soaringissa.org
InternationalScale SoaringAssociation
R/C Soaring DigestPage 20