Kayak Trig

On Facebook, we had a discussion on whether one should buy a Native Slayer Propel 10 or its big brother, the 13, and it made me want to do the math.

So, just the trig related to stability in choppy water, say a 2 feet tall wave comes directly on straight into the bow, for a 10 feet kayak, it would raise the bow relative to the stern 11.31 degrees; for a longer 13 feet boat, it would only raise it 8.75 degrees.

Yes, I know there are many other factors; I am just indicating what happens to say when a horizontal stick of a certain length is lying on the ground and one end is raised by 2 feet, what angle does that create.

Getting hit with a 2 ft. wave from the side has different possible outcomes and effects: A Propel 10 is 34" wide and if it is raised 2 ft., it rolls the vessel 35.22 degrees. If the opposing gunwale dips under and water comes in, well, you will have some issues. You want to get off the water or otherwise take precautions well back of that happening.

Finally, vessel length has another advantage: waves come in multiples and a long boat can ride over successive waves better. The prior wave might be working back along the underside of the boat toward the stern when the next wave hits. This lessens the effects of waves. A short boat rocks more in multiple sets of waves.

Nerd stuff.

Brad

Very Interesting!

That isn't necessarily the way it works. If the bow is shaped correctly it will tend to cut through the wave especially with a longer kayak. And side waves need not rock the kayak at all if they are anticipated and with a little judicious paddle work.

Again, yes, I know this isn't at all the way it actually works when one takes into consideration myriad factors.

All these calculations do is help someone visualize the most basic principle at work, all other variables removed and/or the same for each vessel.

If you put a 10' long 2 by 4 on the ground on your driveway and raise one of its ends up 2 feet (to simulate the lifting action from encountering a wave on the bow), the angle created is 11.31 degrees; if you place a 13' long 2 by 4 on the ground and raise one of its ends up 2 feet, the angle created is a lesser 8.75 degrees.

It is just putting a number to, proving, something we all know . . . that small vessels are less stable than larger ones in waves, all things being equal, and this is a way to broadly quantify what the effects are on a wave lifting the bow of a boat as it smacks into it, depending on the vessel's overall length.

So, less than 3 degrees difference but on a percentage basis, the smaller length "pitches" +29% more. It makes a difference if you go offshore, that is for sure.

For sure, though, just the raw math.

Brad

Your math appears to be spot on. I own both a 10 and a 13 and find that there is very little difference in how they perform on the water. This Saturday we will have both available for a test drive at White Rock Lake Boat Club. Seems like a great opportunity to merge the actual and practical into a solid theory!

No no no, you're all wrong. Just go get an FS12T and watch how it allows 14 gallons of water to come into the kayak when you hit so much as a 12" wave head on. That's how it should be done. Period

Good stuff, I will be going from my FS12T to a Slayer one day in the next few years.

Ha! Rhino, that sounds like a bath to me!

For sure, ya'll get what basic fact I was trying to communicate, all stripped down using trigonometry.

Jerry, I am building a lake house and I know I'll need at least another vessel for kids/grandkids/friends, and I want to eventually hit the ocean and go offshore, so I see a 13 in my near future.

Yes, I was handling the big wind this past Saturday, 15 mph recorded down at the airport but likely windier on the water, and it did really well. The 10 does lose some handling in big waves but I turned broadside to the waves several times and it handled them effortlessly. I was never even close to tipping over.

I am beginning to think for those "on the fence" between a Propel 10 and 13, maybe a Hobie PA 12 versus PA 14, that other than matching the specifics of the water you will likely fish most, the most important criterion is which kayak will you use more. If for any reason a 13 would cause you to go out less often, I'd get the 10.

Ty Southerland made a recent video where he chose a Hobie Outback, specifically the improved 2015 model, over a PA 12 or 14 for this very reason as his favorite fishing kayak. He said he can take the Outback anywhere, drag it across the sand, do things with it/ take it places he simply can't do or go with the big PAs which usually require boat ramp launchings. I get his logic.

Brad

I don't need no math,,, I got me a Hobie. And another shorter one comin.

Carver, one of the very best made, most innovative kayak makers ever: Hobie!

Few handle rough water as well, that is for sure.

Ignore the math, plow on!!!

brad