Can I Build an HP-Series Glider From Scratch?

Bob Kuykendall, 16 August, 1999

The answer to that question depends absolutely on who you are, and how you define "from scratch." If it means that you buy a few Essential pieces from HP Aircraft, LLC and make the rest yourself, then yes, building an HP from scratch is within the reach of most amateur aircraft builders of moderate skill.

If building from scratch means starting with raw materials and proceeding from there, then the question becomes a little more complicated. If you are comfortable with the thought of commissioning thousands of pounds of custom aluminum extrusions from Alcoa or Reynolds Aluminum, then the answer is an unqualified yes. If you are comfortable with the thought of chucking up a bar of 1" x 2.5" 7075-T651 aluminum on your twelve-foot mill table and hogging out a spar cap, then the answer is also an unqualified yes.

Having said all that, keep in mind that you don't really have to build an HP from scratch; virtually all of the components for the HP-18 and RS-15 are available from HP Aircraft, LLC.

The Resourceful Builder

Whether or not it is possible to build an HP at all depends on whether or not one is what I have come to call a "resourceful builder." This term probably conjures up visions of the sort of folks who read Popular Mechanics and built their own submarines from plans advertised in the back. And well it should - the HP series of gliders have always been somewhat of a challenge to construct. Compared with Dick VanGrundsven’s RV-series airplanes, the modern standard by which all sheetmetal kitplanes are measured, the HP kits are far less intuitive, and offer far more opportunities to go astray.

To build an HP kit, you need to do more than read step-by-step procedures. You need to interpret and understand the intent of the blueprints and instructions. Everything you need is there; you just have to look deep and find it. The resourceful builder’s most important resource is between their ears.


HP Aircraft, LLC currently has plans in stock for the HP-18 and RS-15 series sailplanes. Other plans sets, such as for the HP-11, HP-14, the T-tail, and the Schreder trailer, will be available soon.

This is good news for those who have completed HPs but no drawings; the plans are indispensable for repair and maintenance information. For the scratch builder, however, the plans are only useful if you can procure the necessary Essential Parts (or suitable substitutions) described later.

Regarding the HP-18 (and probably true regarding the RS-15), Dick wrote:

"It should be emphasized that the '18 can't be built from the plans alone. Detailed dimensions are not included for parts that are already made or that have been scribed on material in the kit. The prints are intended to help in assembly only."

While this is absolutely true for Essential parts, the HP designs are generally so completely straightforward that the resourceful builder should be able to obtain dimensions for the merely Troublesome parts by careful inspection of the plans or by measuring the parts of an existing aircraft.

Essential and Troublesome Parts

All of the common HP-series gliders are based on a handful of essential parts that are pretty much indispensable, i.e. you can't really build the glider without them, and you can only get the parts from HP Aircraft or from an unbuilt kit.

There are also some of what I call "troublesome parts"; these are parts that are somewhat difficult to make or obtain, but can be obtained or made by the resourceful builder.

The following sections describe each of the common HP gliders in terms of essential and troublesome parts. Starting from the top:

HP-18 and RS-15:

The HP-18 and RS-15 both use aluminum wing spars, PVC foam ribs, and a bonded wing skin. Both have fiberglass fuselage pods with an aluminum aft fuselage; but the RS-15 uses an tubular aluminum tailboom while the HP-18 uses a conventional aluminum monocoque tailcone. Because of the remaining stocks of wing spar caps and fuselage pods, these are probably the most buildable HPs left.

Aesthetically, I find the HP-18 and RS-15 to be among the most pleasing and well-balanced homebuilt aircraft ever. With the sleek flowing lines of the narrow-waisted fuselage, and the smooth bonded wing skins, they were among the first homebuilt aircraft ever to not look like they were built in garages. Dick Schreder deserves a lot of credit for coming up with those two designs.

Essential Parts:

Troublesome Parts:


The HP-16 comes in two different flavors: Early, and Late. The early birds used an aluminum I-beam spar where the whole spar was milled from a single huge chunk of 7075-T6 aluminum. Actually, it came in two pieces, since there's a splice at the 12' line. However, Dick didn't like that arrangement very much, and so later HP-16s used the same wings as the HP-18/RS-15. The following information applies to the later-type HP-16.

The HP-16 generally seems to perform about the same as the HP-18 and RS-15; due largely to the similarity between the wings of all of these aircraft. However, the HP-16 seems to find more favor with larger pilots because of its more generous cockpit. The -16’s greater girth probably makes for some penalty at higher airspeeds, but the difference is seems to be pretty subtle.

Essential Parts:

Troublesome Parts:


The HP-14 is pretty much the definitive HP-series glider; all metal and All-American (well, North American, eh?). The fuselage lacks the pod-and-boom look of most other HPs, and the wings have tons of area that make it a great ship in most conditions. Dick Schreder won the 1966 nationals in Reno in his new HP-14. Also, the late Les Sebald flew his all over the high parts of California and Nevada, and accomplished some incredible feats with it. Once, when he was diving downwind off the top of a Sierra wave, Oakland Center clocked him on radar with a groundspeed of over 300 knots. Subtracting the 100 kt tailwind and correcting for altitude brings it below the HP-14’s Vne, but still… And to answer your next question, yes, Les was one of the first to regularly carry and use a transponder in his glider.

Essential Parts:

Troublesome Parts:


As a representative example of early 1960s technology, the HP-11 is a fine balance of ruggedness and performance. Like the later HP-14, it is entirely conventional in construction, with no structural fiberglass or foam. However, it does have its share of what I refer to as Troublesome parts.

Troublesome Parts:

HP-7 through HP-10

I don't know enough about these earliest HPs to say what's inside of them. I will offer the opinion, however, that unless you absolutely must have one of these for a documentary or for a museum piece, there is little point to building one. One of these would be every bit as hard to build as a more modern HP, and would have significantly less performance.