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There’s a perfect prop for every plane. By LeRoy Cook

26 KITPLANES January 2019 www.kitplanes.com & www.facebook.com/kitplanes Propellers, like wing spars, are among the few parts on an airplane that abso- lutely, positively, must not ever break. Under continual stress while absorbing engine power and converting it into thrust, the lowly propeller has to keep performing its function, year in and year out, with scant attention paid to it. Catastrophic propeller failure imme- diately produces severe vibration as the engine continues to run with an out-of- Sensenich ground-adjustable prop on an RV-4. balance prop, and the resulting stresses can lead to failure of the engine mount. one revolution of the propeller under from the hub. At the blade’s tip, the speed If the engine departs the airframe, the perfect conditions, assuming that it’s of the airfoil’s movement through the air airplane becomes uncontrollable due turning in a medium devoid of slippage is vastly different than it is near the root, to the shift in CG. And yet, most of the or resistance. Think of a screw boring thus the tip requires a minimal amount of time we just give the prop a light caress itself into soft wood. Usually expressed pitch and thickness as the effective speed during our preflight inspection and say in inches, a propeller’s pitch is com- nears supersonic flow. Tip speeds in excess “Yep, it’s still there.” monly quoted in conjunction with the of Mach .75 result in loss of efficiency. A Propellers deserve a little more diameter, as with a 72/56 prop being propeller with too much angle of attack, respect. The design and creation of these one with 72 inches of disc diameter and or pitch, retards rotation and places an exquisitely shaped rotating airfoils is as 56 inches of perfect forward movement inordinate load on the engine. One with much akin to art as to science. The effi- in one revolution. For aircraft certifi- too little pitch, on the other hand, allows ciency of some propellers can reach into cation, propellers of a certain size and the engine to overspeed. the 90% range, as they screw their way pitch are part of the approved equip- Changing airspeed away from a into thin air while pushing or pulling ment, and a minimum-permissible designed peak performance target the entire aircraft. Nothing could be static (full-power runup) rpm may results in less efficiency. At low speed, simpler—or more complex. The sim- be specified as part of the limitations. engine rpm may be limited by the large plest of all aircraft propeller types is, Static rpm proves that the engine and bite of a high propeller pitch, as in “high of course, the humble fixed-pitch two- propeller combination is capable of angle of attack,” while at a high diving blade airscrew, found on basic airplanes producing the thrust suitable for flight. speed, the rpm may rise to beyond red- optimized for low-cost operation and Proper choice of propeller pitch is criti- line as the engine becomes unloaded. uncomplicated piloting. cal to achieve maximum efficiency. There Owners of airplanes with fixed-pitch are actually several pitches and blade propellers sometimes exchange props Perfect Pitch thicknesses existing in the twisted airfoil to maximize one or the other edge of The term “propeller pitch” refers to along the propeller’s length. The adver- the performance envelope, referring to the amount of forward motion that tised pitch is usually measured at a mid- a “climb prop” as one with a low pitch could theoretically be achieved in point blade station about 75% outward angle allowing extra rpm for takeoff, or a “cruise prop” with a higher pitch to optimize speed rather than climb. The Best of Both Obviously, it would be desirable to be able to change a propeller’s pitch, giving the best of both worlds without having to swap between two or more propellers. The first efforts to do this were ground- adjustable arrangements, with the blades held in a hub that permitted their shank to be rotated for pitch change. Such propellers are still available today. In-flight pitch changing came next, using various methods of “shifting gears” from climb to cruise. The Kop- WhirlWind composite propeller on a trigear RV. pers Aeromatic propeller, used on light

Photos: LeRoy Cook, Paul Dye, and courtesy of the manufacturers KITPLANES January 2019 27 aircraft of the 1940s, balanced centrifu- Propeller Corporation in the 1940s, it gal force against airspeed to adjust pitch was reportedly the most efficient pro- for best performance without cockpit peller design. But its weird look, with control. Aeromatic props may be return- a counterbalancing weighted stub ing to at least the experimental market; on one side of the hub, kept it from the rights to the design are now owned becoming popular. by Tarver Propellers in Fallon, Nevada. In experimental aviation, we are per- Simple manual propeller-pitch shift- mitted to build any part of the aircraft, ing, adjusted by pulling or pushing a and that includes carving our own pro- control to shift from a low-pitch take- peller; some dedicated individuals have off/climb setting into a higher-pitched done just that. Unless you are particu- cruise position, was incorporated in larly gifted or inclined toward propeller the Hoffman Dimona motorglider I fabrication, however, it makes more sense Three-blade GT ground-adjustable prop. flew back in the 1980s. One idled the to purchase a ready-made prop from the Dimona’s Limbach engine to reduce dozens of suppliers specializing in them. A buyer’s guide of any type is stress when making the change, and A simple laminated-wood propeller is no bound to have some flaws in it, but when the engine was shut down for longer sufficient for most homebuilts; we’ve attempted to cover the propel- soaring, a third position could move carbon fiber blades, ground-adjustable ler industry as thoroughly as we can. the blades into feather. pitch angles, and even in-flight control- In the accompanying tables, certified Controllable propellers, with vari- lable and constant-speed governing are propellers are listed first, followed by able pitch adjustment using an elec- available to maximize the performance the burgeoning list of non-certified tric motor or oil pressure to position envelope of our homebuilts. propeller manufacturers. The tabula- the blade angle, were developed in the Use of a non-certified propeller, tion includes contact information, 1930s to allow the pilot full control even if the Lycoming or Continental the date of the company’s founding, of optimum engine power, although engine is bone stock, usually requires types of construction, and horsepower rpm still varied with airspeed because an expansion of the Phase I flight test- range available. the propeller was essentially in a fixed- ing period from 25 hours to 40 hours, Some of the larger propeller com- pitch setting once adjusted. This short- just as would a non-certified engine. panies concentrate on type-approved coming was alleviated by coupling the The effect of any pitch adjustments or props for certified engine applications, pitch-change mechanism to a governor other changes needs to be documented while the smaller firms market to the that operated to automatically main- as part of the testing regimen. experimental non-certified user. And tain a constant rpm, the constant- some are doing both, offering a line of speed propeller in use today. Picking a Prop certified props but also more than will- As with choosing a certified Continen- ing to build a custom non-certified pro- How Many Blades? tal, Lycoming, or Rotax engine, there peller for a specific project. The best number of blades to use, fre- are a limited number of suppliers of Established propeller manufacturers quently two blades versus three blades, is certified propellers, perhaps five or six, may sell their products through a distrib- a frequent topic of discussion. With lower which is the reason one finds Hartzell, utor or dealer network, through suppliers horsepower engines, adding an extra McCauley, Sensenich, and MT propel- like Aircraft Spruce, Univair, Wag-Aero blade is largely a matter of sex appeal and lers attached to most of the world’s cer- and SportairUSA, and aircraft kit mak- noise conversion; all things being equal, a tificated airplanes. Hartzell has been in ers may have distributor arrangements to two-blade propeller is more efficient than the propeller business for over 100 years, supply props to their customers. an equivalent three-blade, although the and Sensenich isn’t far behind. Even the three-blade prop will boost thrust at low new kids on the block have a long his- Certified Propeller Companies airspeed during takeoff and climb. How- tory behind them. GT Propellers ever, with increasing horsepower, extra However, the lower-horsepower kit Founded in 1969, GT has produced blades will be needed to absorb the addi- and E/A-B airplanes can be equipped over 30,000 propellers. At last count, tional power. Both the disturbing quality with propellers from a large number of more than 200 propeller variations of the perceived noise and the noise level companies. Some are handcrafted by were available. itself are reduced by adding blades. And, cottage-industry entrepreneurs, each GT fixed-pitch propellers and vari- adding a blade allows the same thrust to with their own following and specialties. able-pitch propeller blades are made be developed with a shorter blade length, Laminated wood predominates as the from a variety of laminated hardwoods reducing tip speed to a quieter level. medium of choice for low-performance that are reinforced with composite Yes, there was a single-blade propel- aircraft, but many prop builders are laminations. Many models comply with ler. Built by Sensenich for the Everel turning to composite materials as well. JAR/EASA 21P Rules.

28 KITPLANES January 2019 www.kitplanes.com & www.facebook.com/kitplanes Sensenich fixed-pitch aluminum prop on a Bearhawk. Hartzell three-blade constant-speed prop.

Ground-adjustable LSA props are Sensenich Propeller Company City, Florida, that builds wood and com- made with monolithic carbon tech- The venerable Sensenich Propeller Com- posite propellers, established in 1999 to nology and incorporate a metal strip pany, established in 1932, now operates as better serve airboat propeller customers. to protect the leading edge. Two- and two divisions: the original company based Sensenich does just about everything three-blade configurations are available in Lancaster, Pennsylvania, which makes in propellers; it still makes fine laminated for engines up to 110 hp. On ground- only metal props, and a division in Plant wood props, it has ground-adjustable adjustable propellers for larger engines, GT uses the same blades found on their variable-pitch props. Certified Propellers GT also makes “old style” propellers Company Date Founded Construction Horsepower Range for replica aircraft and original aircraft that date back to the 1920s–1940s. GT Propellers Via del Commercio, 7 Although they follow original draw- 47838 Riccione (RN) Italy Wood and 1969 30 to 2500 hp ings, these props are often updated with phone +39 0541 69 33 99 composite modern airfoils. fax +39 0541 69 33 31 www.gt-propellers.com Hartzell Propeller, Inc. Hartzell Propeller, Inc. Hartzell has been in the propeller busi- One Propeller Place Piqua, OH 45356 Metal and 1917 Up to 2180 hp ness for almost as long as airplanes have phone (800) 942-7767 or (937) 778-4200 composite been flying. Robert Hartzell and Orville fax (937) 778-4321 Wright were near neighbors in Day- www.hartzellprop.com ton, Ohio, when the company made its McCauley Propeller Systems 10511 East Central Avenue first airplane propeller in 1917. Today, Metal and Wichita, KS 67206 1938 100 to 1200 hp composite Hartzell supplies certified constant- phone (800) 621-7767 or (316) 831-4021 speed propellers for nearly any propeller- www.mccauley.txtav.com driven airplane, including turboprops MT-Propeller USA, Inc. with six-blade configurations. 1180 Airport Terminal Drive Deland, FL 32724 Natural In addition to forged-aluminum 1981 Up to 5000 hp blades, Hartzell has been making phone (386) 736-7762 composite fax (386) 736-7696 structural composite propellers since www.mt-propellerusa.com 1978 and is now building ASC-II Sensenich Wood Propeller Co. (Advanced Structural Composite) 2008 Wood Court propellers with carbon fiber lami- Plant City, FL 33563 Wood and 1932 50 to 275 hp nates and a stainless steel shank. The phone (813) 752-3711 composite Hartzell Trailblazer composite props fax (813) 752-2818 www.sensenich.com feature a swept tip and are now avail- able for 17 aircraft models, includ- Sensenich Propeller Mfg. Co. Inc. 14 Citation Lane ing the Bearhawk 4-Place and Patrol; Lititz, PA 17543 1932 Metal 65 to 200 hp CubCrafters XCub, Carbon Cub, and phone (717) 569-0435 Top Cub; Glasair Sportsman; and fax (717) 560-3725 Vans RV-8. www.sensenich.com

KITPLANES January 2019 29 McCauley prop on a Cessna Skycatcher. MT-Propeller has extensive experience with composite props on experimental aircraft. composite propellers for experimental prop projects on McCauley’s plate is a Non-Certified Propeller Companies and ASTM-certified LSA airplanes, Black Mac Carbon five-blade reversible As would be expected, the world of pro- and it builds aluminum two-blade fixed- constant-speed propeller that will be on pellers built specifically for experimen- pitch models for both homebuilt and cer- the Cessna Denali turboprop single. tal aircraft is expansive and active. The tified applications. freedom to innovate and modify designs MT-Propeller means a lot of choices are out there, in McCauley Propellers MT founder Gerd Muehlbauer began both materials and execution. Some The McCauley Propeller Systems divi- working with composite propellers propeller manufacturers have been in sion of Textron Aviation originated in in 1968 and founded his company, the same location for decades, others are 1938, introducing its first forged alu- MT-Propeller Entwicklung GmbH, more recent start-ups or continuations minum propeller in 1946. McCau- in 1981. Based in Germany, MT pro- under new ownership. ley was purchased by Cessna Aircraft pellers are well supported in North Company in 1960, hence its pres- America by a service center in Airmaster Propellers, Ltd. ent ownership by Cessna par- Deland, Florida, and other loca- New Zealand-based Airmaster offers ent Textron, which also owns the tions. Although primarily known a wide range of options in electrically Beechcraft and Hawker brands. for its “natural composite” propel- controlled constant-speed propellers McCauley’s sales and engineer- lers, some MT applications have an for experimental and ultralight-type ing offices are in Wichita, Kansas, aluminum blade option. aircraft. Their unique mode selector while manufacturing takes place in MT-Propeller has extensive experi- allows the pilot to dial in preset takeoff, Columbus, Georgia. ence providing propellers for Experi- climb, and cruise pitches, after which Long a builder of certified alu- mental/Amateur-Built aircraft, from it holds the desired rpm with little minum-blade props in both fixed- RV-4s to Lancair Evolutions. The interaction. Two- and three-blade hubs pitch and constant-speed variants, company has supplied certified pro- hold a variety of blade styles; Airmaster McCauley is also experienced with pellers for engines of 5000 hp, incor- builds no blades of its own, providing composite propeller construction, porating up to six-blade hub systems. complete propeller systems in collabo- supplying the composite two- In addition to hydraulic constant- ration with existing blade makers. U.S. blade propeller for the Cessna speed propellers, an ELCOPROP resellers include Custom Flight Cre- 162 Skycatcher Light Sport air- electrically controlled propeller is ations, The Airplane Factory, Kitfox plane. Among the composite available for engines up to 350 hp. LLC, RANS Aircraft, Kaolin Aviation Services and Arion Aircraft.

Arrowprop Company, Inc. Primarily a builder of fixed-pitch wooden propellers for ultralight and light experimental airplanes, along with other specialty props, Arrowprop supplies props up to 72 inches in diam- eter. The Oklahoma-based company has been in business since 1961.

Bolly Aviation Based in South Australia, Bolly Propel- Airmaster electrically controlled constant-speed prop. lers first established itself in RC (radio

30 KITPLANES January 2019 www.kitplanes.com & www.facebook.com/kitplanes Non-Certified Propellers Company Date Founded Construction Horsepower Range Airmaster Propellers, Ltd. 20 Haszard Road, Massey Aukland 0614, New Zealand 1999 Metal/composite 80 to 200 hp phone +64 9 833 1794 fax +64 9 833 1796 www.airmasterpropellers.com Arrowprop Company, Inc. P.O. Box 610 Wood and Meeker, OK 74855 1960 Up to 100 hp composite phone (405) 279-2377 Three-blade Catto fixed-pitch prop. www.arrowprop.com control) model aircraft as a supplier Bolly Aviation Hangar 1 Calvin Grove Airfield of wood and composite props, then Virginia, South Australia 5120 1978 Composite 15 to 180 hp branched out into full-size aircraft. Spe- phone +61 8 8380 8396 cializing in ground-adjustable carbon fax +61 8 8380 9083 fiber blade construction, Bolly propellers www.bollyaviation.com.au are available in five Optima Series models Catto Propellers Jackson Westover Airport for increasing horsepower ratings, using 12370 Airport Road, Hangar 156 1974 Composite 65 to 300 hp two-, three- and four-blade hub styles. Jackson, CA 95642 phone (209) 754-3553 Catto Propellers www.catoprops.com Craig Catto started Catto Propellers Competition Aircraft, Inc. 10925 Shire Court in 1974, building two- and three-blade Grass Valley, CA 95949 fixed-pitch props for a variety of non- (888) 634-9839 1984 Composite Up to 100 hp certified applications. Construction or phone (530) 268-3048 fax (530) 268-2321 utilizes a wood core encapsulated with www.competitionaircraft.com structural composite overlay. Catto Pro- Culver Props pellers has achieved ASTM certification 15685 Co. Road 7100 to equip Light Sport Aircraft with its Rolla, MO 65401 1983 Wood Up to 300 hp props. Optional electro-formed nickel (573) 364-6311 www.culverprops.com leading edges create a durable leading edge for the blades. DUC Hélices Aérodrome de Villefranche-Tarare 289 Avenue Odette & Edouard Durand Competition Aircraft, Inc. 69620 Frontenas, FRANCE 1997 Composite 100 to 160 hp Also known by its primary product name, phone +33 (0) 4 74 72 12 69 fax +33 (0) 4 74 72 10 01 Ultra-Prop, Competition Aircraft has www.duc-helices.com long been a builder of ground-adjustable GSC Systems, Inc. composite props for ultralights, trikes, #8 - 2440B 14th Avenue Vernon, BC, Canada V1T 8C1 gyrocopters, and powered parachutes 1984 Wood 35 to 115 hp phone (250) 549-3772 with engines up to 50 hp. It is now pro- fax (250) 549-8441 ducing the Ultra-Prop II, a carbon fiber www.gsc-systems.com reinforced propeller for applications Ivoprop Corporation of 25 hp per blade at about 2500 rpm, 2615 East 67th Street, Unit E making it suitable for engines up to 100 Long Beach, CA 90805 1986 Composite Up to 700 hp phone (562) 602-1451 hp. The 66-inch diameter Ultra-Prop www.ivoprop.com II can be furnished in two-blade to six- Performance Propellers USA, LLC blade configurations. 466 Pr 5832 Donie, TX 75838 2009 Wood 50 to 300 hp Culver Props phone (713) 417-2519 www.performancepropellersusa.com Valley Engineering, suppliers of Culver Props, bought the Culver propeller com- Powerfin Propellers 705 S. 5300 W., Suite 4-5 pany in 2000 to complement its line of Hurricane, UT 84737 2008 Composite Up to 160 hp ultralight and light E/A-B airplanes. The phone (435) 627-0942 two-blade fixed-pitch props are available www.powerfin.com

KITPLANES January 2019 31 for engines up to 300 hp, using laminated maple, mahogany, birch, and cherry wood. Much of Culver Props’ expertise is devoted to replica propellers for WW-I and antique airplanes, including scimitar shapes favored by those early planes.

DUC Hélices Culver fixed-pitch wood prop. DUC Hélices composite prop. The DUC line of forged-carbon com- posite propellers from France carries giving a constant-speed effect for higher propellers in fixed-pitch and ground- European Aviation Safety Agency certifi- speed airplanes, while the Windspoon is adjustable styles, and it also builds a cation and is available for a wide range of designed for slower aircraft. GSC-GTA in-flight adjustable-pitch ultralight and experimental aircraft up to prop, using a mechanical adjustment. 140 hp. DUC Hélices’ ground-adjustable GSC Systems The GSC-GTA can be supplied with propellers come in “Swirl” and “Wind- Based in British Columbia, Canada, either GSC wood blades or Warp Drive spoon” models, the former reportedly GSC makes its Tech Series wood composite blades. An 18-degree adjust- ment is possible. Fixed-pitch propellers are available in 32- to 72-inch diam- Non-Certified Propellers(Continued) eters. GSC focuses largely on Rotax engine applications, including powered- Company Date Founded Construction Horsepower Range parachute propellers. Prince Aircraft Company 6774 Providence Street Ivoprop Corporation P.O. Box 2669 Wood and Whitehouse, OH 43571 1979 100 to 300 hp Ivoprops are widely known for the tor- composite phone (419) 877-5557 sion rod embedded in each blade, allow- fax (419) 877-5564 ing pitch adjustment by tightening or www.princeaircraft.com loosening the adjustment rod to slightly Props, Inc. twist the blade. The Ivoprop Magnum 354 S.E. 2nd Street Newport, OR 97365 1984 Wood Up to 260 hp propeller can be manually adjusted on the phone (541) 265-3032 ground or fitted with an electric in-flight www.propsinc.net variable-pitch control in the cockpit. Ivo- Edward Sterba Propeller Company prop’s latest innovation is an electronic 9660 Southeast 72nd Avenue governor for constant-speed operation. Ocala, FL 34472 1980 Wood 30 to 200 hp phone (941) 778-3103 Blade construction is carbon fiber com- www.greatplainsas.com/ed.html posite, finished with black gelcoat and a Tarver Propellers stainless steel leading edge. Two-, three-, 1500 Rio Vista Drive, Hangar C-4 or six-blade systems are available. Fallon, NV 89406 2003 Wood/composite Up to 170 hp (775) 423-0378 www.aeromatic.com Performance Propellers USA, LLC Frank Johnson’s Performance Propellers Tennessee Propellers, Inc. 7031 Highway 157 company supplies two- and three-blade Rising Fawn, GA 30738 1981 Wood 28 to 100 hp CNC-cut laminated wood propellers (706) 398-0651 for experimental and aerobatic aircraft. www.tn-prop.com Ultra-Prop (see Competition Aircraft) Warp Drive, Inc. 1207 Highway 18 East Ventura, IA 50482 1989 Composite Up to 180 hp phone (641) 357-6000 or (800) 833-9357 www.warpdriveinc.com WhirlWind Propellers Corp. 1860 Joe Crosson Drive, Suite C El Cajon, CA 92020 1973 Composite 80 to 400 hp (619) 562-3725 www.whirlwindpropellers.com Ivoprop ground-adjustable prop.

32 KITPLANES January 2019 www.kitplanes.com & www.facebook.com/kitplanes Performance Propeller wood prop. Sterba fixed-pitch wood prop. Tennessee propellers are made in Georgia. Custom tweaking is provided, allow- Sterba Propellers Construction is of rock-hard maple, using ing the customer to test-fly and return Ed Sterba started carving handmade resorcinol-type glue and finished with a the prop for changes after static and propellers in 1980, initially focusing two-part polyurethane coating. max rpm are verified. A rainproof lead- on props for converted Volkswagen ing edge and fiberglass tips are then powerplants, and he’s still producing Warp Drive, Inc. installed, along with a clear finish. his beautiful laminated wood two-blade Warp Drive propellers have been in fixed-pitch propellers. Sterba Propellers production since 1989. They are well- Powerfin Propellers are available for engines up to 200-hp, as regarded ground-adjustable props with Powerfin builds ground-adjustable car- used in the RV kit aircraft series. solid carbon blades. Many of the Warp bon fiber propellers for a variety of light Drive blades are fitted into other brands experimental aircraft, primarily for Tarver Propellers of ground-adjustable hubs. Warp Drive Rotax engine installations. Hub styles The legendary Aeromatic propeller, with markets primarily to ultralights, trikes, for up to five blades are available, and its automatically shifting blade pitch and gyrocopters, powered parachutes and the company is working on a six-way blade construction using wood core and light experimental planes, along with hub for drone use. Powerfin denotes its laminate overlay, has a long history dating airboats and other users. Two-, three-, products as “professionally designed, from the 1940s. The Aeromatic’s prin- and four-blade styles are available. handcrafted,” with over 20 years of ciple of aerodynamic shifting of propeller experience producing propellers. pitch, with no pilot interaction required, WhirlWind Propellers Corporation was popular for postwar planes until the WhirlWind Propellers makes carbon Prince Aircraft Co. general aviation collapse in the late 1940s. fiber ground-adjustable propellers for Lonnie Prince has been in the propel- The rights to the Koppers design is now the experimental aircraft market in ler business since 1979, building custom owned by Kent Tarver of Fallon, Nevada. two- and three-blade styles. Whirl props for everything from ultralights to At this point, no certified production is Wind Aviation is the company’s con- NASA wind tunnels. Prince props are planned, but new Aeromatic props for the stant-speed propeller division. Whirl- created from rock-hard laminated maple experimental aircraft market are under Wind blades are used by some other and carbon fiber laid over a wood core, development, with one currently flying brands of ground-adjustable props, and feature a scimitar shape that pro- on a VariEze for testing. showing the esteem to which they are duces an aerodynamic pitch change as regarded in the industry. The company speed increases, reportedly a four-inch Tennessee Propellers, Inc. also offers such diverse products as change in pitch from takeoff to cruise. Although it’s now based in Georgia, just replacement blades for Russian Vperod The famous P-Tip option remains avail- outside Chattanooga, Tennessee Propel- propellers on the M-14P engine. able, delaying the tip vortices by curling lers continues to supply two-blade fixed- We trust that you’ll find this over- the prop tip to create the effect of a pitch wood props for ultralights and view of the propeller industry useful. longer blade length. small experimental aircraft, along with Help us keep it up to date by passing propellers for airboats and other users. along changes or corrections. J Props, Inc. Oregon-based Jeff Bertuleit has been carving fine wood propellers since 1984 for homebuilts and ultralights. He focuses primarily on two-blade fixed-pitch props for E/A-B airplanes up to 260 hp. Props, Inc. propellers are made from laminated eastern maple and are up to 35 pounds lighter than a constant-speed prop. As Bertuleit points out, wood’s natural damping avoids having rpm restrictions. Three-blade Warp Drive prop. WhirlWind prop on a CubCrafters Cub.

KITPLANES January 2019 33