My eyes are. Math not bad either, good enough to bid on millions of dollars in masonry and do millions in masonry.
Your’s is better measuring though, measuring and comparing routes to the hundreds of a minute with devastating conclusions.
I could pull a center line on the hull and measure what one inch side to side is in degrees but I have other things planned.
Or I could pull a line 18’-10 and measure 1" then measure the degrees.
I can’t, but what I do works for me, even if it slows my progress. I have enough to satisfy my quest for speed. After all, I don’t race.
One inch would work out to be about 1/2 degree.
Now you want to know how I came up with that estimate, right. You said the boat is 18’10", but the length you should use is from the center of mass to the tip of the bow. Unless you are very light, compared to the kayak, that center will be about your center. I assumed that, as in most kayaks, you set a little bit forward of half the length of the kayak, so I used 9 feet as the distance. The perimeter of a 9 foot circle is about 678 inches. Which works out to just under 2 inches per degree. So one inch would be about 1/2 degree. That should be close enough for what you are discussing.
So I go like an ARROWHEAD 
@szihn, for a paddle to work most efficiently, it must remain stationary. However, to emphasize the point, even a child could tell you the paddle will move. It slips, oscillates, cavitates (or whatever name anyone prefers to apply for creating air voids or bubbles that result in inefficient power, since the air pockets offer no resistance), or flutters because the paddle becomes unstable, either from improper tracking, one side of the blade entering the water first and causing unequal pressure on the shaft which torques the blade around the axis of the shaft.
So if a blade can’t remain stationary, why not just use a double bladed pizza peel. The same reason its better to spin on bicycle pedals than stomp on the pedals to climb. That makes climbing similar to running up a flight of stairs. So why do professional bicyclists do it? Physical capacity and conditioning. It would be delusional for me to watch olympic athletes performing and think I could match the performance at my age of 73. I need a different paddle and technique. I simply do not have the stamina, conditioning, the go-fast boat, or physical capability to paddle a traditional high angle stroke. Therefore, If I want to figure out how to go faster or further, I need a paddle to match my personal attributes. Every paddle has its niche. Every paddle has the ability to tackle specific conditions. Although my whitewater experience is limited, based on typical WW design, paddles are typucal short with big blades. The streamlined design isn’t so critical, maybe because the WW boat is floating in a fast current, where braking is just as critical as propulsion - instant response, whether from a high angle stroke or a rudder stroke.
So why is this paddle different than a low angle paddle or a high angle paddle.
I asked this question but got no answer. Given that this is my natural torson rotation, and I do use a rigid paddlers box, except for shuffling outward at the 2nd part of the paddle arc (tip of paddle ends up about 42 to 44 inches away from the boat), what would anyone suggest to improve my paddle length selection?
As you can see, my low angle stroke is low, skimming the deck. If a short person paddled low angle from chest level, would that paddler need a longer of shorter paddle than me at 6 feet tall.
Ever paddle has a design parameter. Whether it’s length, dihedral, spoon shoon shape, symmetric or assymetric shaped blades. If you need to decide on shaft diameter, consider how much leverage you need in controlling torque. For example, if you need to control the cant for a Greenland laddle stroke, the 30° angle creates torque thst is more easily controlled using a wide loom but bulk adds weight. Dihedral stabilizes a blade as it “tracks” through water but do you want it to track or do you want to moderate the speed of the paddle’s attack and build speed more gradually.
Here’s a detail that I purposely omitted from discussions to see if anyone would address it.
There’s about an 11 minute window where the speed had some spikes, but the range was essentially within (+/-) .34 mph. Now I hrant the GPS can be misleading, but it could also err on a wider band, for example show greater variations up to twice that. I honestly doubt that my speed variations were actually less than the .34 mph range indicated. Such details do not escape the attention of one kayaker when we discuss paddling, which in my opinion is why he reaches the speeds he does. But that doesn’t detract from the fact that he’s a one eyes Sasquatch with a wooden leg. He still manages.
I don’t have the same power, so I use the paddle’s design features to improve my advantage. One new guy explained to me that the Kalliste didn’t have as much dihedral, which stabilizes the blade. At first, I dismissed it, because the only experience this Marine had in paddling water craft was using a rifle butt to move a blunt rubber boat the size of two king-size matresses in ocean current. Well that made me think, and he was right. Rather than suffer instability from a lack of dihedral, I realized how to take advantage of the spoon shape as I shuffled outward during the stroke. It stabilized the blade without adding drag and allowed just a little energy loss while keeping up the paddles force.
It doesn’t matter what paddle you use or the technique you prefer, I can’t tell you how to paddle, what size paddle you use, length, sq inch, blade design or technique. Even if you have a busted flipper, you can do what I do. If you have the stature of Adonis and are a one-eyed Sasquatch with a wooden leg, you can follow that other guy. If you look at the paddles the Marine uses, notice they typically break at the hand grip area behind the trigger guard.
Find the attributes of your paddle and exploit them until they become automatic.
at-least I can give you some of the why a WW blade is that way.
Bracing becomes more paramount that actual paddling and the shape of that blade allows for a better slap brace, as well as a sweep brace.
Rolling is also paramount, because anyone who has done class IV will tell you upside down is a thing. and that big wide flat blade makes rolling a breeze. (also why GP paddles excel at rolls.)
Since in WW you’re generally running with the current paddling is more of a “stop” the water from moving past you than trying to push the water behind you. you more or less use the current to drive you so you really don’t need then same things you want for touring.
And in that use that blade is quite efficient.
