Home Made Hang Glider

Design Notes and Construction

This glider was not designed to perform anywhere near as well as a commercial model, but I wanted to fly. I've flown some fairly small aircraft in the past (Cessna 180 and a sailplane) so I figured this couldn't be much harder.

I chose this particular wing design due to it's simplicity and inherent stability. Some commercial hang gliders are fairly unstable to allow for a larger range of maneuverability, however I just want to fly... straight line or otherwise. The wing is called a Rogallo wing after Francis Rogallo, a NASA engineer who designed it to return Gemini capsules to earth. At that time he felt that the design had no value outside the space industry, and thus chose not to publicize it much. However, quite the opposite happened: NASA decided not to use the design, and random people started hanging from them.

A bit later, Bill Bennett took the design and really made it into what we would call a hang glider today. He built several different versions of various sizes... take a look at some of his ideas here.

These four guys have the design I was going after, mostly for easy of construction, but also because it looks like it will survive well if I do something stupid: Interesting sitting position, Pretty colors, Look out for those power lines, Awsome outfit.

I started really working on this by wandering around looking for possible materials. My original plan was to use PVC pipe and 4-mil plastic tarp from Home Depot. My friends Paul, Chris, and Theo luckily talked me out of that. I ended up with a 1.5" 0.1" thick aluminium keel tube that joins to a thinner tube at the end, a 1.25" 0.058" thick aluminum crossbar, and 3/4" EMT electrical conduit for the leading edges (galvanized steel). The EMT really is the lamest part of the project, and if I ever get more money I'd love to buy real tube to replace it. The steel is WAY heavy, and bends more than the aluminium. Steel has an elastic modulus three times that of aluminium, but a pound of aluminum is much stronger than a pound of steel.

The sail ended up being the hardest part. I decided on ripstop nylon after much pressing from Chris and Paul. Luckily I listened, because it came out VERY nice, if I do say so. The sail is 155 square feet and weighs about 1 lb 3 oz. We got some interesting looks marching into Joanne's Fabric and asking for 13 yards of material, but in the end it all worked out.

The sail has DEFINITELY been the most work of the project. We spent several all-nighters with Chris's mom's sewing machine. As the sail got larger and needed to be laid out on the frame, we commandeered the lounge of the humanities and arts building at WPI. We started sewing around 11:30pm, and the janitors were amused when they arrived at 5am. We finally left at 10am that morning. I then brought it to my parent's house in NJ for the break. I got brass grommets from the hardware store and put them in where lines would go so as not to rip the fabric. It really does look awesome, even though it is slightly off center with the colors.

Unfortunately, when I went to open the outside basement doors to get the frame in, it turned out my parents had built a deck over the door! I spent the rest of the evening disassembling the deck, much to their dismay. I did in fact get everything in, but it fit just right with no room to spare! My parents certainly didn't design the basement for aircraft manufacturing... I'm going to have to talk to them about that.

Here's the sail laying on the frame, ready to get the holes cut for the grommets. Note that the yellow covers a good bit of sail on the left corner, but doesn't go very far over the right edge. (click any image for larger version)

The frame with the control bar attached. I machined a block of aluminum to bolt to the keel and support the control bar, though most of its rigidity should come from the lines to it.

The frame with the lines attached. Not only do the lines keep the control bar centered and help it to move the airframe, but they prestress the frame downward, so that when the air lifts it up, it will be about straight. The thing only weighs about 30 lbs, so with my 130 lbs we get a wing loading of 1.03 lbs per square foot - pretty much nothing compared to most airplanes.

-Jack Carrozzo