Free Flight: Duration
Harry Murphy 3824 Oakwood Blvd. Anderson, IN 46011
NFFS NEWS
The month of June looms as a busy one for the National Free Flight Society (NFFS).
- June 1–4 — U.S. Indoor Championships at the University of Tennessee Minidome (116-ft ceiling), Johnson City, TN. There will be 20 official events and a host of unofficial ones. Area hotel and dormitory facilities are excellent. Indoor buffs can send a No. 10 SASE to:
USIC, 1655 Revere Dr., Brookfield, WI 53005 for a three-page contest packet.
- June 19–23 — First annual week-long NFFS/U.S. Outdoor Championships at the Mid America Air Center near Lawrenceville, IL. Over 60 events covering all facets of Outdoor Free Flight competition. A SAM‑type bean feed and an NFFS banquet are planned. There are a number of motels in Lawrenceville and neighboring Vincennes, IN, and plenty of low-cost dormitory space at Vincennes University. Get entry information early by sending a No. 10 SASE to the appropriate address below:
- For AMA and Nostalgia Gas events: A. Italiano, 1655 Revere Dr., Brookfield, WI 53005
- For Old-Timer events (FF or R/C): Don Sachtjen, RR #5, Box 56B, Bloomfield, IN 47424
- For the Flying Aces Club Flying Scale events: Lin Reichel, 3301 Cindy Lane, Erie, PA 16506
A correction: the contest flyer originally specified Category II conditions — this was a printing error. Wind direction and crop situations will dictate actual flight rules, but assume Category III conditions will probably exist.
Another important correction: six NFFS-sponsored events will be split into Jr./Sr. instead of combined Open age categories. These events are:
- Gas (1/2A)
- Hand-Launched Glider
- Embryo Rubber
- P‑30 Rubber
- Pee Wee 30 (Rubber Pee Wee)
- Peanut Scale
Subsequent entry packets have been corrected; if you received the initial distribution, please amend accordingly.
These two back-to-back ventures in 1989 demonstrate renewed energy within NFFS to promote Free Flight competition nationally. Show your support by attending and by joining/rejoining/renewing NFFS membership. Annual dues are $15 — send to: NFFS, 6146 E. Cactus Wren Rd., Scottsdale, AZ 85253
NFFS Plan Service
Bob Klipp directs NFFS Plan Service and reports the 1989 listing of available plans has been updated. The new listing includes 165 designs, including Jackson's Pilfered Pearl and Verbitsky's 1987 BE‑48 F1C World Champion. To request the listing, send a No. 10 SASE to: NFFS Plans, 10115 Newbold Dr., St. Louis, MO 63137
Bob is also offering full-size plans of the Satellite 1000 at a reduced price: $5 postpaid for the first two dozen orders. After that, prices revert to the normal fee: $8.50 for NFFS members, $9.50 for nonmembers, plus 20% postage. If serious about obtaining plans at either price, send the full amount; excess will be returned if the special price is exhausted.
Pertinent Potpourri
- Vic Cunningham’s Geodetic Galaxie (1/4A version) is available again. Kits $24.95 postpaid (California residents add $1.62 tax). Make checks payable to Galaxie Model Co., P.O. Box 4842, Covina, CA 91723. Vic’s original 585 and his new Maxi were scheduled to be available early 1989.
- Model Research Labs (MRL) 1989 catalog is recommended for scratch builders wanting an introduction to space-age composites (Kevlar, carbon-fiber configurations, aluminum wing skins, etc.). The catalog contains in-depth descriptions and do’s and don’ts for proper use of these materials. Send $2 to:
Model Research Labs, 25108 Marguerite, #160, Mission Viejo, CA 92692 You’ll receive an educational catalog on modern composites.
Donations & Contests
- U.S.A.F. F.A.I. F/T Team: Manager Roger Simpson requests cash donations to help outfit the current teams with support equipment. Contributions can be sent to:
Roger Simpson, 2625 Queenstown Dr., Rancho Cordova, CA 95670 Donors can expect a team patch and team decal if funding goals are achieved.
- Canadian Jimmy Allen commemorative contest: Peter Mann reports a possible contest for the 50th anniversary of the Jimmy Allen Model Airplane (originally kitted in 1939; reproduced by Sagamore Models). Flights may be logged anytime between March 1 and September 30, 1989. No entry fee. Send a No. 10 SASE to:
Peter Mann, 36 Sydenham St., Guelph, Ontario, Canada N1H 2W4
Al Lidberg Plans
Al Lidberg offers a 1989 10-page plans catalog featuring a 40-in.-span Jumbo Scale Cessna Airmaster. The catalog is $1, or free if requested with a $6 check for the plan. Plans include four pages of building instructions and three views of the full-scale aircraft. Address: A.L. Lidberg, 614 Fordham, Tempe, AZ 85283 (Tell him Duration sent you!)
The Zeek Chronicles — Part IV
When Bill Cranford’s Premium Manufacturing Company produced the “large-stab” A/B Zeek in the early 1950s, he enlisted Lew Mahieu to help get the project moving. Revisions were made to the original Air‑O design; some changes were obvious, others subtle.
- The Korean War material shortages led to hardwood engine bearers replacing the earlier metal back‑plated steel mount bars found in the original Air‑O kit.
- The enlarged stab and rudder were intended to improve stability.
- A smaller single wheel improved appearance.
- The fuselage profile was simplified, slightly reducing vertical height differences between stab and wing locations.
- Both versions commonly used a glow-powered McCoy .19 engine.
The Air‑O kit plans even showed locations for an ignition coil and batteries, indicating some early models may have used ignition engines.
The Zeek wing remained largely unchanged, helped by using steel‑rule rib dies obtained from Air‑O. Full-size plans of both versions of the A/B Zeek are available from various plan shops.
Lew Mahieu later aided Premium in producing a small ready-to-fly R/C model supplied to the Los Angeles Examiner (powered by a K&B .035). He worked at K&B from 1949–53 and was responsible for the one kit venture there (his A/B Zeek design), intended to match the new K&B .15 Green Head for FAC Power competition. Lew contributed to fuels, engine development, artwork, and contest successes. He later phased out of model building and active competition after the mid-1950s but left a lasting mark on Free Flight history.
Premium’s A/B Zeek kit was the first of the flat‑bottomed‑airfoil spinoffs of the single‑cambered Zeek. Bill Cranford noted in a 1983 letter that flat-bottomed ribs were simpler to make without scale-rule dies, which contributed to that era of Zeek variants. More on flat‑bottomed Zeeks will appear in a future chapter.
Newsletter Spotlight
This month we highlight The Vegas FreeFlight, the official publication of VAMPS (Vegas Antique Model Plane Society). The club is Old‑Timer oriented; most local flying takes place on the one-by-four-mile hard-clay surface of Eldorado Dry Lake, about 25 miles northwest of the Las Vegas Strip. The club attracts about 45 models to its monthly meets. The nearby area (State Road 115 on the California/Nevada border) is close to a hotel/casino named Whiskey Pete’s.
Current club officers:
- Larry Lake (President)
- Frank Gable (Secretary/Treasurer)
- Phil McCarey (Newsletter Editor)
Annual dues are $5. Monthly meetings are the third Wednesday of each month at the offices of UNS Consultants, Inc. (use the back door). The newsletter is reportedly free to nonmembers; for specifics contact the editor: Phil McCarey, 532 College Dr. #212, Henderson, NV 89015
On the down side, Bill Baker’s Okie Flyer newsletter is ending due to burnout. Bill’s Oklahoma-based one-man rag was highly rated while it lasted — best wishes to him in his next venture.
That CG Location Once Again
Matz' Maxim of Murphy's Law: "A conclusion is the place where you get tired of thinking." I’ll use this clinic to correct the misleading formula I published in my February 1989 column for finding the approximate center of gravity (CG) of a model.
I originally presented an incomplete formula that appeared as:
CG = Sa x Tm Wa x Ca
where:
- Sa = stab area
- Tm = tail moment measured from a point 25% back from the leading edge of the average wing chord to a comparable point at 25% of the stab chord
- Wa = wing area
- Ca = average chord of the wing
That presentation omitted a required step. The intermediate number produced by (Sa x Tm) / (Wa x Ca) is actually the tail volume coefficient (TVo). The correct procedure is:
- Compute the tail volume coefficient:
TVo = (Sa x Tm) / (Wa x Ca)
- Compute the approximate CG (as a fraction of the mean aerodynamic chord from the leading edge):
CG = (TVo + 0.25) / 2.5
This yields a more realistic initial CG location. Note this is an approximation — a calculated neutral point — so start flights with a safety margin toward stability.
Recommended starting offsets from the calculated CG:
- Competition Power models and Towline Gliders: move starting CG forward by at least 5%, preferably closer to 10% of the average wing chord.
- Competition Rubber models: move starting CG forward by about 20% of the average wing chord.
Average chord calculation:
- Average chord = area / span (for wing or stab).
These formulas plus the suggested forward offsets should prevent many first-flight failures caused by mislocated CG.
Definitions and Disagreements
There are differing interpretations of tail moment (Tm) in the literature:
- Bill Bogart: Tm is the distance between the wing leading edge (LE) and the stab quarter chord (25% back from LE).
- Bill McCombs: Tm is the distance between the leading edges of the wing and stab.
- Jim O’Reilly: Tm is the distance between the quarter chords of both wing and stab.
All chords are mean average chords; differences in measurement points will slightly affect final computations. This is another reason to include the 5%–20% safety margins.
References and Further Reading
The following sources are useful for deeper study:
- Bogart & Rhodes condensed article in Zaic’s 1959–61 Model Aeronautic Year Book (page 88), originally in Model Airplane News, Jan 1959.
- Bill Bogart’s in-depth study of static stability presented at the 1980 NFFS Symposium.
- Gil Morris’ contribution at the 1984 NFFS Symposium, including a simple computer program for locating CG.
- Jim O’Reilly, "CG for competition rubber-powered models," NFFS Digest, Jan/Feb 1983 (references Bogart/Rhodes).
- Making Scale Model Airplanes Fly — to order send $9.95 plus $1.05 postage to:
Aircraft Data, Box 763576, Dallas, TX 75234
Acknowledgments to Bill Bogart, Bill McCombs, and Gil Morris for pointing out my original misstatement and supplying reference material.
A.L. Porgee once sent a terse note about CG problems: when he has a CG problem on a model, he simply "drills it out!" — a drastic solution that sometimes has its place.
See ya downwind at the USOC!
Transcribed from original scans by AI. Minor OCR errors may remain.
