Schreder HP-18

"HP-18" redirects here. For the Hewlett-Packard calculator, see HP-18C.

HP-18
An HP-18 dis-assembled prior to display at the Paradive Flight Gallery in Habonim
Role	Club (formerly 15 metre) class Sailplane
Manufacturer	Homebuilt
Designer	Richard Schreder
Number built	180 kits sold [1]

The HP-18 is a Richard Schreder-designed metal Racing Class sailplane that was offered as a kit for homebuilding during the 1970s and 1980s. ^[2]

Design and development

The HP-18 is a flapped (15-meter) sailplane featuring a V-tail and 90-degree flaps for glidepath control. The fuselage is composed of a prefabricated composite forward fuselage and a semi-monocoque aft fuselage, and features steeply reclined seating and a side-stick controller ^[2] although modifications using a conventional stick have been made.

Major features:

• Very low cockpit with reclining seating position
• Sidestick (changed to conventional stick by some homebuilders)
• Two-piece canopy (changed to single piece forward opening by some homebuilders)
• V-tail that folds upwards for easy storage
• Wing structure composed of spars with caps pre-machined from solid aluminium plate and aluminium wing skins bonded to closely spaced foam ribs
• Fiberglass fuselage pod, wing tip skids and tail fairings
• Aluminium tail cone
• Winglets added by some homebuilders
• Water ballast carried inside the hollow aluminium wing spars
• Typical Schreder trailing edge flaps/airbrakes partially interconnected with the ailerons

Variants

As most homebuilts, the HP-18 has been constructed with many variations in detail. Perhaps the most significant version is the Super HP-18 developed by Canadians Ed Hollestelle and Udo Rumpf, which features a modified wing airfoil, winglets, a front-hinged canopy, conventional control stick and higher ballast capacity.

Aircraft on display

• EAA Airventure Museum, Oshkosh, Wisconsin ^[3]
• National Soaring Museum, Elmira, New York ^[4]
• US Southwest Soaring Museum, Moriarty, New Mexico ^[5]

Specifications

General characteristics

• Crew: One pilot
• Length: 23 ft 2.4 in (7.07 m)
• Wingspan: 49 ft 2 in (15.00 m)
• Wing area: 113 sq ft (10.5 m²)
• Aspect ratio: 21.4
• Empty weight: 470 lb (213 kg)
• Gross weight: 970 lb (446 kg)

Performance

• Maximum speed: 150 mph (240 km/h, 130 kn)
• Maximum glide ratio: 38
• Rate of sink: 126 ft/min (0.60 m/s)

References

1. Said, Bob: 1983 Sailplane Directory, Soaring Magazine, page 23. Soaring Society of America, November 1983. USPS 499-920
2. Activate Media (2006). "HP-18 HP Aircraft, LLC". Archived from the original on March 3, 2008. Retrieved July 24, 2008.
3. "Bryan/Harris HP-18 Sailplane". Archived from the original on July 19, 2011. Retrieved March 28, 2011.
4. National Soaring Museum (2011). "Sailplanes in Our Collection". Archived from the original on May 16, 2011. Retrieved February 26, 2011.
5. US Southwest Soaring Museum (2010). "Sailplanes, Hang Gliders & Motor Gliders". Archived from the original on November 20, 2022. Retrieved May 26, 2011.

• Schreder Designs webpage
• R Johnson, A Flight Test Evaluation of the HP-18W Sailplane, Soaring, July 2003

External links

• HP-18 Reference Info Link