Calculating your B.A.R.G. Factor

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. Add that number to your guild factor which is calculated by taking your boards liters, and dividing them into your weight in kgs.

My board progression as examples:
85kg rider.

Learned for 10 days on an 8’x30” 170l monster.
AR = 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 in all but the most extremely light winds)

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 (arrives next week, weight tbd)
BAR = 3.5
GF = 1
Sum = 4.5 (unridden, testing begins early 2024)

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 waterstart.” Here’s what the results showed.
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.

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.

I, personally, expect to focus my research on board efficiency in the 4-4.75 range.


Nice way of looking at it.
Just for the record for myself later
Gofoil 4’8 BARG = 3.37
Armstrong 7’2 = 5.8
Board: Aspect ratio + Volume ratio

Board AR (length/width) + Board (Litre) /Rider weight kg).

Need similar formula for foils

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Nice, fwiw here are some board dims when I did something similar for DW boards by looking at the AR

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Interesting as I’ve just ordered 5’1 x 20 50L
I’m 92kg so comes out at 3.59

Which is higher than my Sky style sls 4’9 x 23 65L @3.18
My custom 5’3 x 23 83L comes out at 3.64

I can’t imagine the 5’1 will go as early as the 5’3 but hoping at least as early as the 4’9.

Can’t wait to test this out :call_me_hand:

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That’s a great chart! Would be cool to see something like that done over a 5 year span of wingboard development.

This is a good example of why the equation needs a little tweaking. I would agree with your assumption about the 5’1" vs 5’3". I think the guild factor is under valued/weighted in the equation but I haven’t dove in on how to adjust this yet.

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Yeah especially as my 5’3 pulled in tail and bottom

I think that’s right, I have a 5’0"x20" ~50L that is way harder to get going vs my 5’0" x23 85L. Both right around 3.5

Sinkers require dynamic lift to get to the surface to begin the takeoff. My 50L sinker has a displacement type hull (rounded nose and very large bevels with a narrow flat area) and so there’s not much dynamic lift to pull the board to the surface. For that volume and length, I suspect a wider/flatter planform would take off earlier since it would be easier to get to the surface and start skimming.

I think for weighting, volume fraction needs more weight below 1.0 and less weight above 1.0.


Wonder if thinking about this in terms of Guild helping or hurting Bar would better take into account how volume affects ease of take off.

Take a 100kg rider. Above 20+ liters the marginal effect of each additional liter is probably minimal. Below 50 liters or so each liter reduction will also have less impact.

The relationship with BAR doesn’t seem additive. A 40 liter high BAR board might get out of the water easier than a low BAR board once a 100kg rider has the board on the water and is standing on it with some speed, but at that point the rider is basically home free anyway.

If we multiply instead of add:


and do some shaping to the Guild curve, this might better represent the interaction between Guild and Bar.


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I like where your head is at on this and hadn’t considered that change before. I’m going to play with this for a little bit and see what I come up with and will give a better response/comment then.

Thanks for helping!

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I played with this a bunch on smaller boards and it undoubtedly was a better representation of takeoff ability when approximating sinker boards. So, that’s an awesome upgrade to it for sure. I have not played with it a lot on bigger boards of higher volume. I wonder if it would make sense for the guild factor to get capped at some point? 1.5 maybe? I’d imagine that there is a point where it doesn’t add much to the takeoff any longer but I’m not sure what that number would be?

Awesome! Glad it’s helpful.

Yeah, agree on the different relationships between guild and boards on the small and large side. The shaped guild curve above was manually shaped to account for those effects. The benefit trails off where liters > rider weight and likewise the penalty is less pronounced per liter the lower you go (reasoning there probably isn’t a big difference between 35 liters and 40 liters if you weigh 100kg).

Here’s how the manually shaping was done for guild (assuming a 100kg rider). We could adjust these numbers and possibly approximate them with a simple equation with a few coefficients that would take into account rider weight.