Author Topic: Calculating your BARG Factor.  (Read 3997 times)

B-Walnut

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Calculating your BARG Factor.
« on: December 27, 2023, 04:05:47 PM »
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 8x30 170l monster.
AR = 3.2
GF = 1.98
Sum = 5.18 (very easy to get on foil, I dont 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 510x29 123l 15.5lbs
BAR = 2.41
GF = 1.43
Sum = 3.84 (not to shabby to get on foil, crummy in the air)

E3 48x26 83l 12.7lbs
BAR = 2.15
GF = .97
Sum = 3.12 (least favorite board Ive ever owned terrible takeoff)

Barracuda 8x21 112l 13lbs
BAR = 4.57
GF = 1.3
Sum = 5.87 (easiest board Ive 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.

Foil_Dreamer

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Re: Calculating your BARG Factor.
« Reply #1 on: December 27, 2023, 08:20:02 PM »
Been trying to paddle up/catch small bumps on a board with a 5.32 BARG for me.

It's been an excercise in futility but I did get a few quick elevator rides with a wing in crappy conditions. I have no doubt the thing would work fine for getting up with a wing in half decent conditions.

New board will be a 6.63 BARG and I am figuring if I cannot paddle that one off the water with a nice big foil then it ain't ever gonna happen. Should have a decent shot at ultra light wind wing popups as well.

sflinux

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Re: Calculating your BARG Factor.
« Reply #2 on: December 27, 2023, 08:38:58 PM »
Lindsay Lord studied aspect ratio in planing hulls:
https://etchellsfleet27.com/wp-content/uploads/2019/08/Naval-Architecture-of-Planing-Hulls.pd
Lindsay Lord found that aspect ratios(W/L) 0.35-0.45 to be most efficient for holding weight. 

Your E3 4'8" x 26" had a W/L of 0.465, above that range was was your least favorite. 
The E3 5'10" x 29" had a W/L of 0.4149 and was not to shabby.
The E3 5'3" x 22" had a W/L of 0.35 and was quick to take off
The 8' x 30" montser had a W/L of 0.31 and was very easy to get on foil.
The Sunova Carver 5'10" x 20" had a W/L of 0.29 #untested
The Barracuda 8' x 21" had a W/L of 0.22 and was easiest board I've ever had to get on foil
The Custom 6'3" x 20" had a W/L of 0.27 and was extremely fast off the water.

With hydrofoils, things are different as you are not concernced about holding weight, you just need to build enough speed in order for the lifting force of the foil to take off.  Dave Kalama discovered that speed is your friend for early takeoff.

I would think there are other things to consider.  Were you using the same foil when comparing all of the boards?  Was the mast position tuned for each board?  Were the bottom shapes off all of the boards the same?  I would think that bottom shapes would be a big influence on ease of popping up.  And was the same tail used for all the testing  (same foil profile, size, same shim angle)?  Same energy in the water? (different days, different energy)
I'm am not sure about your equation.   You are focusing on Guild factor. Guild factor could have an influence, but I would think you would have to be at the extremes to feel much of a difference, G/F < 0.8 or > 2. 
Rather than Guild factor, I would be interested to hear the relation of surface area (or projected area) of a foil to a riders weight.  A smaller lighter rider can get by with a smaller faster foil.  Where a heavier rider will need a larger foil, but have to deal with the increased drag.

Lindsay Lord also noticed that the optimal angle the board makes in the water changes with respect to aspect ratio.  Boards with
aspect ratio .2 had a planing angle of 0.75 deg
aspect ratio .3 had a planing angle of 2 deg
aspect ratio .4 had a planing angle of 3 deg
aspect ratio of .5 had a planing angle of 3.75 deg
aspect ratio of 0.6 had a planing angle of 4.25 deg

I would think that as the optimal planing angle changes, the aspect ratio of the foil can become important, where you would want to dial in the optimal aspect ratio (lift/drag) and area of the foil with the speeds in question.  And as some foils have different cadence for optimal efficiency, I wonder if having a board with an aspect ratio that is in the range of the optimal planing angle would make popping up easier.
No doubt a complicated recipe to get it all right.  My hat is off to all of the early adopters paving the way.

I use foils for kiting.  My first foil was a 5'6" x 16" 2002 Rush Randle W/L 0.29.
Second board was a liquid force 4'2" x 19.5" W/L 0.39 (with 2017 Cloud IX foil).
Different foils for each board.  Boards have completely different bottom contours.  Volume unimportant.  The W/L 0.39 has a lower takoff speed, but the foil section is thicker and probably larger area too.
« Last Edit: December 27, 2023, 09:15:02 PM by sflinux »
Quiver Shaped by: Joe Blair, Blane Chambers, Jimmy Lewis, Kirk McGinty, and Bob Pearson.
Me: 200#, 6'2"

Beasho

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Re: Calculating your BARG Factor.
« Reply #3 on: December 27, 2023, 10:05:30 PM »
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.

OK - Here is my data. 

My Sailfish had a total of 5.88.  Was pretty good at Downwinding.  Then I added 2" of tail.  It is slightly better, but I may be getting better too. 

I have a board in the hopper that is 10'.  It will push your number to 7.01.  We will see how that works for paddle up. 

As you may be aware I have been focusing on keeping weight down with the HL factor which is (Weight in lbs / 100 Liters).  10.0 is par. 

  • Sailfish Original - 5.88
  • Sailfish New Tail - 6.03 - 8' x 21" x 6" x 130 liters @ 10.5 lbs.  Paddles up very well.  Gets up with a 5.5 meter sail in the lowest wind.  NO NEED FOR BIGGER SAIL.  Light weight 10.5 lbs means I don't need a smaller board.  No downside until you get into the open ocean, hard to start in 8+ foot open ocean conditions when its 20+ mph.  AKA too rolly polly.  Dicey on bigger waves meaning 7+ feet going fast with a bigger foil because of light weight.  BUT GREAT, GREAT in small short period chop
  • BumbleBee - 4.42.  6' 9" x 26" x 5" 115 liters @ 11 lbs.  No way I would use this for downwinding unless it was perfect Gorge chip-in conditions.  Otherwise I love this board for SUP foiling in good, uncrowded conditions.  It is my preferred Wing Foil board.  Plenty of volume, 115 liters, means it never sinks and will work from 10 knots to 25 knots comfortably all on a 5.5 meter wing.  Because of its width, 26" it is stable in open ocean chop.  Still super light @ 11 lbs with footstrap.  So
  • Javelin - 7.01   I am building this board.  10' x 22.75 x 5" should come in ~ 13 lbs.  Designed for big wave SUP foil Rhino Chasing.  Still being built.  Report to follow.

The Sailfish has ~ 170 sessions now
The BumbleBee has almost 100 sessions
« Last Edit: December 27, 2023, 10:18:53 PM by Beasho »

B-Walnut

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Re: Calculating your BARG Factor.
« Reply #4 on: December 27, 2023, 11:57:04 PM »
Been trying to paddle up/catch small bumps on a board with a 5.32 BARG for me.

It's been an excercise in futility but I did get a few quick elevator rides with a wing in crappy conditions. I have no doubt the thing would work fine for getting up with a wing in half decent conditions.

New board will be a 6.63 BARG and I am figuring if I cannot paddle that one off the water with a nice big foil then it ain't ever gonna happen. Should have a decent shot at ultra light wind wing popups as well.

Let us know how the new one goes!

B-Walnut

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Re: Calculating your BARG Factor.
« Reply #5 on: December 27, 2023, 11:59:31 PM »
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.

OK - Here is my data. 

My Sailfish had a total of 5.88.  Was pretty good at Downwinding.  Then I added 2" of tail.  It is slightly better, but I may be getting better too. 

I have a board in the hopper that is 10'.  It will push your number to 7.01.  We will see how that works for paddle up. 

As you may be aware I have been focusing on keeping weight down with the HL factor which is (Weight in lbs / 100 Liters).  10.0 is par. 

  • Sailfish Original - 5.88
  • Sailfish New Tail - 6.03 - 8' x 21" x 6" x 130 liters @ 10.5 lbs.  Paddles up very well.  Gets up with a 5.5 meter sail in the lowest wind.  NO NEED FOR BIGGER SAIL.  Light weight 10.5 lbs means I don't need a smaller board.  No downside until you get into the open ocean, hard to start in 8+ foot open ocean conditions when its 20+ mph.  AKA too rolly polly.  Dicey on bigger waves meaning 7+ feet going fast with a bigger foil because of light weight.  BUT GREAT, GREAT in small short period chop
  • BumbleBee - 4.42.  6' 9" x 26" x 5" 115 liters @ 11 lbs.  No way I would use this for downwinding unless it was perfect Gorge chip-in conditions.  Otherwise I love this board for SUP foiling in good, uncrowded conditions.  It is my preferred Wing Foil board.  Plenty of volume, 115 liters, means it never sinks and will work from 10 knots to 25 knots comfortably all on a 5.5 meter wing.  Because of its width, 26" it is stable in open ocean chop.  Still super light @ 11 lbs with footstrap.  So
  • Javelin - 7.01   I am building this board.  10' x 22.75 x 5" should come in ~ 13 lbs.  Designed for big wave SUP foil Rhino Chasing.  Still being built.  Report to follow.

The Sailfish has ~ 170 sessions now
The BumbleBee has almost 100 sessions

It will be incredibly interesting to hear the results of the Javelin. With a BARG Factor all the way up to 7 it will be great to hear how performance at the extreme end is, to start to consider and evaluate where the point of diminishing returns is. Sharing all the data is how we find the sweet spots and know what to build next!

B-Walnut

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Re: Calculating your BARG Factor.
« Reply #6 on: December 28, 2023, 12:09:59 AM »
I would think there are other things to consider.  Were you using the same foil when comparing all of the boards?  Was the mast position tuned for each board?  Were the bottom shapes off all of the boards the same?  I would think that bottom shapes would be a big influence on ease of popping up.  And was the same tail used for all the testing  (same foil profile, size, same shim angle)?  Same energy in the water? (different days, different energy)
I'm am not sure about your equation.   You are focusing on Guild factor. Guild factor could have an influence, but I would think you would have to be at the extremes to feel much of a difference, G/F < 0.8 or > 2. 
Rather than Guild factor, I would be interested to hear the relation of surface area (or projected area) of a foil to a riders weight.  A smaller lighter rider can get by with a smaller faster foil.  Where a heavier rider will need a larger foil, but have to deal with the increased drag.

No doubt a complicated recipe to get it all right.  My hat is off to all of the early adopters paving the way.

I use foils for kiting.  My first foil was a 5'6" x 16" 2002 Rush Randle W/L 0.29.
Second board was a liquid force 4'2" x 19.5" W/L 0.39 (with 2017 Cloud IX foil).
Different foils for each board.  Boards have completely different bottom contours.  Volume unimportant.  The W/L 0.39 has a lower takoff speed, but the foil section is thicker and probably larger area too.

I think you're on the path of the old saying: "Perfect is the enemy of good." I can only imagine the nuanced details of an equation that would take into consideration the water condition, wind condition, board shape, foil design, even riders style would need to be quantified somehow. However, as a basic template to consider what to try for new production boards or custom designs/shapes/volumes I think this is a valid reference point to consider. These basic conclusions were made after compiling data from over 100 kits and probably 70 riders. I think I'm aiming for something simple and widely useful in this first crack. If we dive too deep the equation become unusable to most. If you can't touch a board, what equation can use the generic information that is published by most board manufacturers? Even weight isn't published by many!

So yes, lets figure out the perfect equation, but let's not forget about the guy who lives in remote Alaska and wants to order a board and has no reference point to make his purchase off of!

 


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