Wasn’t that bucket board from yesterday a kick? We hope you’ll forgive us for the lead in, it wasn’t completely intentional, James wasn’t able to ride it the first time out, (it seems some old man forgot to pack his wet suit or take the correct dry suit!) so we took advantage of the lack of pictures. We’ve also become accustomed to the process that folks go through when they see something different, so we did play off that.
So today is part one of some GPS Data logging wakesurf testing and research. We’ll explain the process and show you a picture or two and then a short video that will serve as visual observation of what we were doing in our testing and wakesurf research.
Just as a refresher, we took a GPS data logger, wrapped in plastic bag!, out out a wakesurf board and then performed certain positional tests to get data logged to the recorder. The recorder has various settings and without going into that too much, we used a subset of the NMEA sentences. We set the GPS Data Logger to record those sentences once every second.
Now we had hoped that we’d have all this data at 1 second intervals, but 5 second intervals was more like it! We logged every single cotton picking thing and well, our little unit choked on it. So in subsequent data recording sessions, we’ll reduce the number of items we record to just what we need. Some data like direction from true North aren’t really all that necessary! It’s handy, but we aren’t using it for anything.
Now we wanted to test a few things, one is the height of our wake. So we had the rider position themselves at the very bottom of the wake, and hold the GPS data logger unit at a specific position that could be duplicated at the top of the wake and then hold that position for at least 3 seconds. The idea was to be sure we got a reading at that spot.
Then, the next position was at the top of the wake. GPS data logger held in the same position and then held for at least 3 seconds. We used the rope for that purpose. Now we are using the difference between those two points to determine the height of the wake, or at least that was the plan. So the unit didn’t need to be at the bottom or top of the wake, just at a uniform height from them both. Subtracting would then give us the wake height. Well hopefully!
Then after that a final test was to try and determine the terminal velocity of a rider driving forward. Our unit doesn’t really give good readings laterally. We’ve seen units that do, we didn’t buy ne of those.
We did this test once with Jeff Walker and then again with James Walker.
Here are some pictures so you can get an visual of the process. This is of Jeff Walker driving forward. Jeff held the unit in his left hand and you can see the plastic bag on the ride side in the picture. This is of the “speed” test while Jeff drove forward.
That test was performed multiple times. The repetition was a safeguard to insure that we got a solid reading at least one time, if not all of the times the rider performed the test.
We want to put this sort of in perspective. We normally surf at around 11 mph. Now that is a fairly small number but if we convert it into feet and seconds, it gives us a reallt different perspective. We know that a mile is 5,280 feet, so at that 11 mph we are covering 58,080 feet in that same hour. That’s a huge number! Lets bring that down to feet per minute, by dividing by 60 minutes in an hour and we are then crossing over 968 feet per minute. Now THAT’s a pocket! Can you imagine how much surfing you could do in that??!! Oh wait, we do that don’t we? Ok so lets do one last calculation, let’s see how much ground we are covering in one second by dividing that 968 ft per minute by 60.
About 16 feet? So really, that’s a normal sized pocket isn’t it? Pretty average? If your wake has a 16 foot long pocket and it takes you 1 second to drive forward, your effective pocket length is 32 feet. So even the most mundane pocket is twice as long as all of the hyped ones. You just gotta love physics and math! Our pockets are always moving. We are too, that’s how we keep up with the boat, but your pocket length is effectively determined by the difference in speed you travel above the speed of the boat. If it takes you 5 seconds to drive forward at 11 mph, your effective pocket length is…80 feet (16 feet per second boat speed times the 5 seconds it took you to cover it). So you added 3 feet to your pocket length??!!! HAHAHAHAHAHAHA! We can add 60 feet by slowing down how fast we drive forward, take THAT you spammers. :) And get out of our way you 3 foot pipsqueak.
Anyway the point being that there is an effective pocket length that is more relevant than the static measurement that is so often thrown around. The effective length takes into consideration the speed of the boat, which is making the wake and your ability to consume that wake by driving forward. Static measurements are just hooey, because we are traveling at speeds that cover that length in the time it takes you to blink. There really isn’t all that much relevance to a static pocket length, because we aren’t static. Obviously if it was 1 foot long that’s a problem, but if it’s 15 to 16 feet long, at speed, it’s two to three times that in effective length, if not more! So here is a thought. If you don’t want to buy a new 100,000 boat that gives you 3 extra feet of pocket length get a board that extends you existing pocket.
You know how we always hear folks talk about how fast a board is? Oh my super-duper-copy-rhino-slayer goes so fast. Well, ignore those folks. What if your board fit in your pocket, allowed you to do all the tricks you wanted like airs and 360′s but took you longer to travel from the back to the front? Just saved you $99,200 did we? AND we converted your effective pocket into a KILLER wake. Probably 100 feet long!
Revolutionary thinking, right? No, see in ocean board shaping these sorts of things are always considered, and trust us, most of the solid shapers out there know this stuff. We aren’t introducing anything new…well maybe the testing apparatus, we are just UNDOING the crap that gets spewed by some folks and prevents so many of us from getting the right board for our wake.
21 foot or 24 foot pocket length, really? Who cares. I have an 80 fot long pocket If I slow my board down, maybe 150 feet long!!!!
Now that we have all of that out there on the table and we have you ditching all of that sales crap and the mumbo jumbo from yahoos, and thinking EFFECTIVE pocket length lets look at the speed test data from our first test subject. Here is picture of one spread sheet that converted the direct records in Knots to Miles Per Hour. 13.05 MPH! WooHoo! Ripping it up for an old man. In your face!
That’s about a 2 mph difference between the boats speed at this test riders maximum speed. Trust us on this calculation, please. That’s about an extra 3 feet of wake length covered per second from what the boat is traveling. Our pocket length is about 20 feet long, so quess what? Effectively our rider takes close to 5 seconds to travel from back to front and can you guess the effective pocket length? 80 feet. Your boat sucks! Our pocket length is 80 freakin’ feet long! Actually so is yours, but what does 3 feet mean in that? hmmm, not all that much huh? Even 15 feet isn’t all that much in the scheme of an effective length of 80 feet. Making you think differently about your wake? It should.
Now we should say that there is some accleration involved, so the rider in that example doesn’t go from 11 mph to 13 mph instantly, but for discussion purposes you get the idea.
Also, be sure to check back tomorrow for the data on James in our continued discussion of wakesurf research. Here is a quick picture of James driving forward. Can you guess his top speed? :) He was able to go a little faster than on the bucket board.
Thanks so much for following along, we really appreciate it!