*This equation and how it is used is constantly being updated. What you see published here will be updated whenever possible to keep the most current notes available to everyone.
*Last updated December 2024
I’ve been working on a simple equation to roughly calculate ease of takeoff for boards based on your board aspect ratio (B.A.R.) and your guild factor (G. Factor).
I’ve collected data from over 100 different riders and kits at this point and have a few notable data points to share, but need to more deeply refine this equation over time.
Here’s how it works:
Calculate your board aspect ratio by simply dividing length by width. (BAR)
Calculate your guild factor which is calculated by taking your boards liters, and dividing it by your weight in kilograms. (GF)
Next, multiply your BAR*GF to get your BARG Factor.
(Update: Originally I used BAR + GF but over time have found BAR * GF to be superior and use that exclusively now.)
My board progression as examples:
85kg rider.
Learned for 10 days on an 8’x30” 170l monster. BAR = 3.2 GF = 1.98
BAR*GF= 6.34
Very easy to get on foil, I don’t think I ever turned it, no skill yet. Worth noting I was up and foiling on my first day as a self taught rider with a wing. I also caught every wave I paddled for in the ocean even though I didn’t know how to foil and just straight lined them back to shore
First board I owned:
2021
E3 5’10”x29” 123l 15.5lbs BAR = 2.41 GF = 1.43
BAR*GF = 3.45
Not to shabby to get on foil, crummy in the air
2022
E3 4’8”x26 83l 12.7lbs BAR = 2.15 GF = .97
BAR*GF = 2.09
Least favorite board I’ve ever owned, terrible takeoff
2023
Barracuda 8’x21” 112l 13lbs BAR = 4.57 GF = 1.3
BAR*GF = 5.94
At this point in my wing foiling, it was the easiest board I’d ever had to get on foil that was still fun in the air
2023
E3 5’3"x22" 83l 11.5lbs BAR = 2.86 GF = .97
BAR*GF = 2.77
Fun to ride and quite quick to take off in comparison to other boards at the time.
2024
Sunova Carver 5’10"x20" 85l 10.75lbs (vapor construction) BAR = 3.5 GF = 1
BAR*GF = 3.5
This is the potential perfect all around BARG Factor for me. Very good slogging and low end matched with excellent in air performance.
I've ridden it in as light as 5 knots and over 60 knots.
Sunova Aviator 6'6"x18" 11.25lbs (vapor construction) BAR = 4.33 GF = 1.06
BAR*GF = 4.59
An excellent board for low effort takeoffs when underpowered. Slogs great, buttery smooth touchdowns, excellent tiny wing takeoffs in high wind. Narrow width sacrifices maneuverability.
Sunova Carver, Custom, 5'11"x20" 77l 10.5lbs BAR = 3.55 GF = .91
BAR*GF = 3.22
Testing in progress.
Sunova Pilot, Custom, 5'9"x20" 65.7l 9.3lbs BAR = 3.45 GF = .77
BAR*GF = 2.66
Testing in progress.
Note: Over time the growing collection of my personal BARG Factors has become valuable in that it shows me overall trends on what I like my takeoff difficulty to be. You can do this for yourself as well by calculating out all of your old boards and thinking about how they felt. I thought a particularly interesting data point was that the very first board I owned calculated out to 3.45 and then 3 years later I landed on my all time favorite board which had almost the same calculation at 3.5
Things to consider:
With the 100 or so data points I collected from other riders I asked for the sum to be reported and if they felt as though their board was “easy to water start.” Here’s what the results showed.
(update: that these numbers are for BAR+GF and do not take BAR*GF into consideration)
Competent riders considered a BARG Factor of 5 and higher to be capable for DW SUP.
3.5 and higher, to be easy to water start.
3.25 and lower, to be hard to water start.
BEGINNERS considered a BARG Factor of 4.5 and higher to be easier to water start. Anything below that was considered average/hard.
Conclusions this gives us:
This gives some rough guidelines for buyers who don’t have extensive access to gear demos to consider. This gives rough guidelines to beginners who are picking up their first board and want to consider if it will be easy to learn on, and if, when they progress, it would be considered easy for the average rider to get up on.This gives us guidance on how easy takeoff will be. I personally really like that this drives the conversation away from liters, and more towards shape, to define efficiency.
What this doesn’t give us:
This does not take foil into consideration.This doesn’t give you a guide to how fun a board will be once in flight.This doesn’t take into consideration the nuanced details of hull design.This doesn’t take windspeed and water currents into consideration. You can break this equation. For example: an 8’x1’ sheet of plywood would have a BAR of 8 but a GF of 0 = BARG Factor of 8 which sounds highly efficient. But, this is yet to be tested and quite possibly not true. (update: this is what brought about the alternate BAR*GF equation)
I’ll continue to refine this equation to try and take in additional considerations and how each aspect can be weighted and more correctly evaluated. However, while this should not be considered the final word on how to pick your next board, it is a worthy calculation to take into consideration if you are unsure and want to continue to explore the possibility of other shapes.
See you at the river,
Bryan Lee, M.S. Experiential Education.
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