*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.
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, add your BAR+GF to get your BARG Factor.
(Update: If you are comparing sinker boards you will get better comparisons by multiplying the BAR*GF to see a wider and more accurate variance in those boards. For everything -10l to positive buoyancy BAR+GF works fine.)
My board progression as examples:
85kg rider.
Learned for 10 days on an 8’x30” 170l monster. BAR = 3.2 GF = 1.98 Sum = 5.18 (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:
E3 5’10”x29” 123l 15.5lbs BAR = 2.41 GF = 1.43 Sum = 3.84 (not to shabby to get on foil, crummy in the air)
E3 4’8”x26 83l 12.7lbs BAR = 2.15 GF = .97 Sum = 3.12 (least favorite board I’ve ever owned, terrible takeoff)
Barracuda 8’x21” 112l 13lbs BAR = 4.57 GF = 1.3 Sum = 5.87 (easiest board I’ve ever had to get on foil and was fun in the air)
E3 5’3"x22" 83l 11.5lbs BAR = 2.86 GF = .97 Sum = 3.83 (fun to ride and quite quick to take off, or so I thought...)
Custom 6’3"x20" 83l 9lbs BAR = 3.75 GF = .97 Sum = 4.72 (extremely fast off the water, track boxes were awkwardly placed so I didn’t get a good feel for it in the air unfortunately)
Sunova Carver 5’10"x20" 85l 10.75lbs (vapor construction) BAR = 3.5 GF = 1 Sum = 4.5 (An excellent board. I've ridden as light as 5 knots and over 50 knots on this board)
Sunova Aviator 6'6"x18" weight TBD (vapor construction) BAR = 4.33 GF = 1.06 Sum = 5.39 (this board arrives in summer 2024 and is yet to be tested)
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 absolutely 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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