As the newer breed of surf wings have started to emerge around the 750 sq cm and 800 span size i find myself wondering if the move to 80cm masts was the wrong play or maybe the right play for those front wings and the wrong play for trying to every day something as small as possible
I think two or three years ago when we were all riding wings in the 900-1100 range at 900-950 span the 80 mast made sense for keeping the wing in the water and achieving more critical turns. Riding a smaller wing now with a span under 800 and i’m thinking there’s advantages to going back to a smaller mast. I think for micro takeoffs it helps having the wing closer to the wave energy (in the water column) might help stretch the range on the small wings - and i always want to be riding the smalles wing possible.
I think also its easy to make a case that tip breaching isn’t as big of a factor on the smaller wing. Also i think the smaller mast just whips around faster.
Just took off 2cm from my newest mast down to 76 from 78. Not expecting the world from 2cm but i think changes in this zone should be subtle
I think you’re on to something. I moved to shorter masts for down winding (82cm → 75cm) and use the same thing for wave riding. Now that I’m riding 850 wings in the surf that breach well, I never felt the need for a longer mast. Years ago with the wider wings I preferred longer masts to turn harder and keep the wing in the water.
Lowest part of the leading edge? I know that AFS has alot of dihedral i thought it might be more! But i think its relative - shorter is probably better for those wings for most of us.
I think its also dependent on where you are (Geography is king) Longer period deep water energy is going to penetrate deeper so there’s probably less “low end gain” in deep water energy. In short period energy i think the difference between a 75 and an 80 is like going up or down a wing size.
this pic was AFS skinny 75cm and Code UHM 80cm, it’s angled too high to effectively show it, but you could drop a level across the two LE in the pic and roughly aligned with maybe 1cm in it.
So here is my thought process…and note i ride 750cm2 sk8, wingspan is like 77.5cm or something and a 80cm mast.
Because rotational inertia scales with the square of the length, the 80cm mast requires roughly 13.7% more rotational force (torque) to swing at the same speed as the 75cm one.
SO a shorter mast is about13.7% easier. but the longer mast is easier to take off on steeper waves. now is 5cm that big of a noticeable difference?
I feel like you really need to test the 80cm and 75cm back to back. The difference might just be a slightly easier feeling on the 75cm, but then you’ll just get lazy again.
going from 78 to 76 I don’t think will be noticible.
I have noticed that when i do hit the bottom of the sand or rocks or whatver when I’m sitting on the board waiting for waves….that is usually where the wave ends up breaking anyway. Kinda cool
If you are driving the foil around you in flat water then your applying the torque.
If the face of the wave is driving the foil around you than it is applying the torque and its there to make the most of along with the potential energy of the mast height that can be drawn upon when power is low.
I don’t think of it as rotational inertia. I think to do a turn you have to fly the foil from one side to the other. Like flying the kite from one side of the window to the other. So the foil is swinging an arc under you and the mast is the radius. With a shorter mast the arc is a shorter distance so you don’t fly the foil as far to execute a turn. Oddly enough though that distance is a function of the square of radius so I think that math still maths.
For me though that’s a side effect, this is 90% about squeezing out a little more bottom end by having the foil a little closer to the wave energy in the water column.
Yes Kane explained it to me nicely (I forgot, or it’s here somewhere), but shorter = twitchier / more direct, so yet it cuts both ways. For Florida I see no downside, but for all over compromise I feel like LE to deck we’ve generally converged
You can think of the system as a mass (your weight) at the end of a stick pivoting around the bottom (the foil).
As everything leans over (system rolls), there is a torque from gravity. The torque will be proportional to the length of the mast L.
The moment of inertia is proportional to L^2.
Angular acceleration = torque / (moment of inertia) ~ 1/L
Time to fall over / lean over a certain amount goes as sqrt(1/angular acceleration) = sqrt(L).
So a longer mast feels slower to roll by a factor of sqrt(L).
This is the same physics controlling the period of a pendulum of length L (same scaling with length).
For 75cm → 80cm I think the longer mast should be slower to roll by about 3%.
Though maybe it gets more complicated because the foil itself and the submerged part of the mast has some roll resistance due to the water contact. A longer mast with its higher torque might help overcome that resistance more? Idk real world physics gets hard.
not necessarily agreeing with you on this one, but if we were to calculate that it wouldn’t be based on the length of the mast alone. It would be mast length plus board thickness plus your center of gravity height off the board.
Just to put an example forward, I’m about 1.8m tall, center of mass probably 1.2m off the ground give or take. Compare total lever arm of .75m mast + .1m board thickness + 1.2m = 2.05m versus an 80cm mast with 2.1m. sqrt(2.1/2.05) = 1% difference.
Good point about factoring in height of the rider center of mass. Definitely forgot to account for that and agree with your correction. What else do you think this way of looking at it could be missing?
There are some discussion if you look around about how we set up turns - a little like a motorcycle where you steer the wrong way to get the lean going first. So it isn’t a simple pendulum mode we’re dealing with. To be honest, I have no idea how to calculate the difference between mast lengths even though I’ve thought about it.
I think it’s reasonable to try to understand the behavior of the roll axis alone without introducing any yaw into the problem. Especially because I don’t think mast length would factor into the ability to yaw the board. Sure, I would expect things to get more complicated during an actual turn where yaw does happen and there the mast length probably affects the turn radius that keeps everything in sync. But for the question of how quickly the system tips over without any yaw I would think the pendulum picture should work reasonably well.
From a feeling while riding perspective, I’m wondering what other people’s experience is.
I totally agree with Kanes “shorter=twitchy” (I might reword twitchy to responsive) but if I had to say wether longer or shorter was more “stable”, stable defined more along the lines as controllable and “easier” , I would say shorter feels more stable while also being more responsive/“twitchy” which if that’s the consensus is an important distinction.
is that what other people feel in general?
and I’m talking about on foil and turning on waves. Not like standing on a SUP balancing on the water where a longer mast might feel more stable because it’s deeper in the water.
To me, I’m always seeking “stable/easy” while also “responsive “ combinations of tuning / gear because I think sometimes they actually go hand in hand. Where as a lot of times it is described that you have to make a setup less stable or harder to control to also gain “twitchiness”
long story short I’m all in on the 75cm ish length mast. Especially when paired with a board that doesn’t care about touchdowns on the touch points. Only times I’ve ever preferred the longer 82cm + long masts are like kite foiling or on a board that sucks at touchdowns.
theres also probably some sort of relationship between Foiler height and leg length and mast length that might matter. Similar to board volume and weight so “short” masts might not be the same exact length for all heights of people.
