Standard Sharky          Fold Plot
Fin Sharky
Variations

standard sharky
The K-19 Sharky is a new fundamental delta-wing paper "jet" design.

It's fairly hard to make because of the accuracy required in placing the folds, but can be done successfully on some if not most attempts.

The plans here are calibrated for 8.5" x 11" photocopier-weight paper. I hope to give specifics soon for A4 and maybe other sizes, and check into how much difference the paper thickness makes in the optimal geometric specifications.

fin sharky Key Features
The fuselage is held together at the top (and all around as well) just by folding. No tape needed.
Excellent weight distribution toward the nose.
Optional dorsal fin makes a "Fin Sharky".

Flight characteristics
Flys straight and fast, glides well, resists excessive stalling.
Inherent nosedive usually requires bending the trailing wing edges up a little for good performance.

Made of paper that's different colors on the 2 sides the Sharky looks quite nice. It also helps understand how it's constructed. I couldn't find any paper like this so I had to print it myself. I used a photocopier to print grey matte on oversize paper and then cut it to 8.5" x 11" (necessary because the photocopier doesn't print all the way to the edge of the paper). Maybe using a crayon instead would work.
Background
I started trying to design a plane that would look much like the Standard Sharky and hold together at the top of the fuselage just by folding, way back when I was in elementary school creating the K-20 and its predecessor the K-13B. X-19 was then the designation for this not-yet-perfected plane when I thought of the K-20 variation on the K-13B. When the X-19 project was eventually declared a success the result was dubbed the K-19.

The K-19 Sharky became a reality in mid-1999 shortly after it occurred to me to start a paper airplanes website. I went back to this old line of development with a more sophisticated view and was able to make the previous problems yield easily.

The main way I did that was not so much with fancier math, but just by loosening my definition of perfection a bit in two ways. In elementary school I was set on the idea that an airplane design should be perfectly symmetrical even if the asymmetry is barely noticable. And, I didn't want a design that was very difficult to make due to extreme precision needed in positioning the folds.

As soon as I decided to forego these requirements, presto, I had a K-19 Sharky. Having more knowledge of geometry made it easier. Even without the optional fin this plane reminds me of a shark in looks and behavior, and I started calling it a Sharky almost right away.

Special caution about flying the K-19
It has a very stiff and pointed nose. Please don't fly the K-19 toward anyone unless they're expecting it. Don't try to catch a flying K-19 unless you're being very alert and/or wearing protective eyewear. (The same cautions apply to many toy planes you can buy.)
Images, Text, and 3-D Forms Depicted 2001 PaperAirplanes.net