Hatz CB-1

The Hatz CB-1 is a tandem two-seat, open-cockpit biplane designed by John Hatz and first flown in 1968. Conceived as a smaller, simpler, plans-built homage to the classic Waco F-series biplanes of the 1930s, the CB-1 designation stands for "Continental Biplane" because the prototype "Happiness" flew behind an 85 hp Continental C-85. At roughly 875 lb empty, it is widely regarded as the lightest true two-place biplane available to homebuilders. Construction is traditional: welded 4130 steel tube fuselage and tail with fabric-covered wooden wings (spruce spars, built-up ribs). Approximately 150 CB-1s were reported flying as of 2011, with many more projects in progress. The airplane is owned and supported today by the Hatz Biplane Association (hatzbiplane.com), which stewards the plans for the CB-1 and its derivatives. It is a sport airplane in the purest sense — pilots who own Hatzes fly them for the sheer joy of low-and-slow open-cockpit flight, breakfast runs, formation work, and the occasional gentle aerobatic maneuver.

All four are plans-built (the Classic is also offered in kit form by Makelan). Because every Hatz is homebuilt, no two are identical — engine choice, wheel pants, cowlings, headrests, and instrument panels vary widely.

The CB-1 is honest and slow. Book cruise of 80 mph (about 78 KTAS) with the 115 hp O-235 is realistic; operators with the 85 hp Continental report 75 mph cruise. With the huge wing area (178 sq ft) and modest power, it climbs well but accelerates deliberately. Stall is a non-event at about 40 mph. The airplane is not stressed for hard aerobatics in the original configuration — builders typically describe it as capable of gentle loops, wingovers, and lazy eights, but it is not a Pitts. Density altitude hurts badly at these power-to-weight ratios; operators in the Mountain West generally specify the O-235 or larger. Range is limited to roughly 170 nm with VFR reserves from 18 gallons. Open cockpit means real-world cross-country cruise is further limited by pilot endurance in the slipstream.

With a 725 lb useful load and 18 gallons (108 lb) of fuel:

• Full fuel + pilot + passenger: 725 - 108 = 617 lb for two occupants and baggage. Two 180 lb adults + 20 lb of baggage fits comfortably (380 lb). Full-fuel endurance is approximately 3.0 hours at 5.5 gph, for 170-180 nm no-wind range with 30 min reserves.
• Two 200 lb adults + baggage: 400 + 40 = 440 lb, leaving 285 lb (47 gal) available — exceeds tank capacity, so the airplane is tank-limited rather than weight-limited with any reasonable passenger load. This is typical for sport biplanes.
• Solo pilot, full fuel: Easy; CG shifts are manageable because the pilot flies from the rear seat.
• Density altitude reality: At 5,000 ft density altitude with two 180 lb adults aboard, the 115 hp O-235 version still climbs acceptably; the 85 hp C-85 version struggles and is best considered a sea-level-to-3000-ft airplane in the West.

The CB-1 is not fuel-range constrained by weight — it is constrained by tank size and pilot comfort in the open cockpit. Most owners plan 1.5-2.0 hour legs regardless of what the math says.

• Flight training (2/10): Not a trainer. Tailwheel, biplane sightlines, and homebuilt insurance make this a poor primary or transition trainer.
• Backcountry (3/10): Short-field numbers are respectable (400 ft ground roll), but small fuel, open cockpit, and no cargo volume rule out serious bush work.
• Business travel (1/10): 78 kt cruise, no IFR, no enclosed cabin. Zero utility.
• Aerobatics (5/10): Capable of basic positive-G maneuvers within its power range, but not a dedicated aerobatic platform. See Acro Sport I / II and Smith DSA-1 Miniplane for comparison.
• Cross-country (2/10): Open cockpit and 170 nm range limit this to short legs between fuel stops.
• Cargo hauling (1/10): Two small baggage areas, if any. Not applicable.
• Local fun flying (10/10): This is the mission. Sunset hops, pancake fly-ins, formation with other Hatzes, low-and-slow sightseeing — the CB-1 was built for exactly this.
• Surveying (2/10): Open cockpit precludes mounted sensors; slow speed is OK but payload and endurance are not.

CB-1 panels are minimal by design. A typical build has:

• Basic VFR day: Airspeed, altimeter, compass, tach, oil pressure/temp, CHT. Often no electrical system at all — hand-prop start, no radio. Panel cost under $1,500.
• VFR with comms: Add a handheld or panel-mount comm (iCom A220), intercom, and a basic transponder with ADS-B out (uAvionix tailBeacon-X or skyBeacon on position light). $3,000-$5,000 installed.
• EFIS-equipped modern build: Garmin G5 or Dynon D3 Pocket Panel, GTR 200 comm, GTX 45R transponder. $8,000-$12,000 installed. Rare but seen on newer builds where the owner wants ADS-B in traffic and basic situational awareness.

See Avionics Pricing Reference for experimental pricing baselines. No IFR approvals — the airplane is visually and aerodynamically a day-VFR machine.

As an Experimental Amateur-Built aircraft, the CB-1 does not use STCs. Builder modifications are common and legal, including:

• Engine upgrades: Moving from C-85 to O-200 (+15 hp) or O-235 (+30 hp over baseline) is the single most impactful change. O-235 builds cruise ~5 kt faster and climb noticeably better.
• Wheel pants and streamlined cowlings: +2-3 kt cruise.
• Extended baggage: Small compartment behind rear seat, useful for a soft bag.
• Larger fuel tank: Some builders extend to 22-24 gallons for extra range.
• Symmetrical ailerons / stressed wing kit: A few builders have beefed up the wing structure to permit more aggressive aerobatics, though this is not a blessed modification.
• Hatz Classic conversion: Some CB-1 projects are finished to Classic standards (push-pull controls, O-320) mid-build.

• Parts availability (fair): Engine parts (Continental/Lycoming small engines) are readily available through the normal GA channels. Airframe parts are all builder-fabricated or community-sourced. The Hatz Biplane Association forum is the main hub for plans, drawings, and tribal knowledge.
• Mechanic familiarity (specialist): As an experimental, condition inspections must be performed annually by an A&P (any A&P, IA not required). Finding one comfortable with wood-and-fabric structures is the hard part — most modern A&Ps have never touched a spruce spar. Tube-and-fabric specialist shops are valuable and getting rarer. See Maintenance Ecosystem.
• Annual inspection cost: $800-$1,500 for a condition inspection, assuming no major squawks.
• Typical annual operating cost: $4,000-$5,500 including hangar, insurance, fuel (50 hr/yr at 5.5 gph), and routine maintenance. Recover years push this to $10,000+.
• Expensive items to watch: Wing recover ($6,000-$10,000), engine overhaul ($31,000–$39,000), prop ($2,500-$4,000 for a fresh wood Sensenich).

Prices for flying Hatz CB-1s in 2026 typically range from $20,000 (tired fabric, runout engine) to $55,000 (fresh recover, mid-time O-235, nice paint). A typical well-sorted CB-1 with a mid-time engine and decent fabric sits around $32,000. Factors that move price:

• Engine condition: A fresh or mid-time O-200/O-235 is worth $15,000-$20,000 of the asking price alone. A runout engine subtracts heavily because experimental owners must pay for overhauls out of pocket (roughly $35,000 for an O-235 overhaul).
• Fabric age: Fresh fabric (less than 5 years) adds $8,000-$12,000. Tired fabric requiring recover subtracts the same.
• Workmanship and rigging: A Hatz known in the community as a "good flying one" commands a premium.
• Builder's log and documentation: Clean condition inspection history and a complete builder's log are essential for resale.
• Hatz Classic vs CB-1: A Hatz Classic with the O-320 typically asks 20-40% more than an equivalent CB-1.

See Aircraft Valuation Methodology for engine/fabric adjustment formulas applied to experimentals.

Experimental amateur-built aircraft do not receive FAA Airworthiness Directives. However, recurring condition inspection findings and community-known issues include:

• Wood wing rot: Spruce spars in fabric-covered wings are vulnerable to moisture, particularly at drain grommets and the lower wing root. Any prospective buyer should have the wings inspected by someone familiar with wood structures.
• Fabric life: Dacron (Poly-Fiber/Ceconite) covering has a 20-30 year life depending on hangaring and sun exposure. Recovering is a $6,000-$10,000 material-and-time project.
• Engine hours on small Continentals: Many CB-1s fly behind C-85s or O-200s that are decades old. Chrome cylinders, camshaft corrosion from infrequent use, and magneto timing issues are common.
• Control cable wear: Original cable-operated ailerons and elevators should be inspected at every condition inspection for frayed strands and pulley wear.
• Builder quality variance: Because every Hatz is unique, workmanship varies enormously. A poorly built Hatz can have heavy controls, rigging problems, or marginal fits. A well-built one is a jewel.
• Tailwheel steering: Steering springs and chains wear; ground loops during training transition are not uncommon.

CB-1 insurance lives in the experimental taildragger niche and is shaped by three factors: experimental amateur-built, tailwheel, and open-cockpit biplane sightlines. Typical 2026 premiums:

• Hull: $1,500-$2,200/yr on a $35,000 hull for a pilot with 500+ hours total, 100+ tailwheel, biplane checkout
• Liability only (smooth $1M): $600-$900/yr
• Full package: ~$1,800/yr typical

Underwriters (Avemco, BWI, EAA Insurance Solutions) will typically require a biplane checkout with a CFI and some dual in type or similar (Pitts S-2, Acro Sport, Starduster). Low-time pilots may be declined or restricted to liability-only. See GA Insurance Underwriting for experimental and taildragger adjustments.