The Hatz Homepage

535

"Bratz"

OWNER/BUILDER: Randy Brooks

REGISTRATION: NX24B

NX24B "Bratz" CB-1 S/N535

Randy has provided the procedure he used to calculate his Center of Gravity Range. Click here to review that procedure.

The Bratz (Brooks - Hatz) has been flown 64 hours since certification.

The Bratz is powered by a Lycoming 0-320A, 150 hp, turning a Sensenich W74-56
wood propeller, and equipped with Cleveland wheels with chrome discs and Maule
tail wheel.

The aircraft was flown to the National Biplane Fly-In at Bartlesville,
Oklahoma and to the Antique Fly-In at Blakesburg, Iowa.

Before I started my project I reviewed the plans (S/N535), observed and flew
other Hatz biplanes, and then decided to make several changes.

Modifications were made as follows:

1. Aluminum ribs in wings and ailerons to save maintenance and reduce labor in construction.
2. Modified wing tips to reduce stalling speed and reduce maintenance.
3. Installed ailerons on only lower wings to reduce number of parts. Ailerons were redesigned as friese type 100% static balanced to reduce the chance of flutter and reduce adverse yaw.
4. The wing spars are 1/2" deeper due to the use of aluminum ribs and all fittings were increased from 80 thousands to 90.
5. Raised center section 2 inches with Stearman-type cut out to give additional entry space for front cockpit.
6. The lower wing dihedral was increased to 4 degrees for lateral stability. Due to friese-type ailerons and increase in dihedral, the Bratz in cruise flight requires little or no rudder input for turns.
7. The cabane struts were modified to provide adjustment of stagger for easier rigging.
8. Provisions were provided for ground adjustment of horizontal stablizer so aircraft could be rigged for cruise flight with elevator trim in neutral.
9. A 15 gallon fuel tank was installed in front of front cockkpit to give a total of 34 gallons of fuel for the 150 hp Lycoming engine.
10. Toe brakes were installed in both cockpits at the request of wife who holds a private pilot certificate. Cessna 140 type pedals were used in front and my own design pedals in rear.
11. Landing gear was lengthened three inches to allow for slower landings.
12. Aluminum panels were installed from firewall to the aft cockpit to prevent fabric damage around cockpit area. It also decreases fire hazard.

Performance figures after 64 hour of flying

Take-off distance	300 feet
Landing distance	400 feet
Stall speed	40 mph
Approach speed	60 mph
Rate of climb	800 fpm @ 70 mph
Cruise speeds	88 mph @ 2300 rpm 95 @ 2400 rpm 105 mph @ 2500 rpm

Click on thumbnail pictures or text to see full size

	In flight photo of the Bratz
	Randy Brooks and the Brooks-Hatz "Bratz".
	Another in-flight picture
	Construction of ailerons, Friese type, 100% static balanced
	Note: Cabane adjustment for stagger Windshield - no frame Fuselage aluminum panels Center section cut-out
	Landing gear covering: 3/4" foam with wooden strips to keep fabric off the foam
	Wing construction: metal ribs, 2024T-3x.025
	Wing, aileron, and tip contruction: Note fueltank and fuselage formers
	Center section/cut-out: Cabane strut with stagger adjustment Wing construction: Root rib
	Fuselage with metal panels and cabane struts Note the navigation light and fin-to-fuselage fairing
	Building interplane struts Note: Fuel tank, baggage metal covering, and fin fairing Metal fuselage formers
	AFT STABILIZER FITTING Uses a slip tube similar to a Piper Cub.
	RIBS and TANK Aluminum ribs constructed with .025 2024 material. Tank (19 gal.) is constructed of .050 aluminum.
	VERICAL FIN and RUDDER Fin is removeable from fuselage
	FUSELAGE (excuse my Cub) Longerons are .049 tubing Shoulder harness tubes aft of each cockpit Wing fittings are made of rectangular tubing Front of fuselage modified for 15 gal. fuel tank Controls mounted in aluminum blocks with zerk fittings for lubrication Control stick brackets constructed of rectangular tube Seat frames are welded tube with aluminum bottoms
	AIRFRAME Note wing-tips, ribs, and fairings
	CENTER SECTION Note metal covered
	FRONT STABILIZER MODIFICATION Raise and lower leading edge of stabilizer using washers (AN 970) as spacers

---

Copyright © 1999-2004, The Hatz Homepage, All Rights Reserved Webpage design by Douglas MacBeth, Wee Beastie Biplane Works Comments, suggestions always welcome at admin@weebeastie.com

---