Here’s a visual (and this is on firm snow surfaces in the context of effective edge length)

You and I lay a piece of 4 by 8 plywood over an open gap on the upper floor of a Park City cabin-mansion that is 7’6″ feet wide. We each stand on either end of the piece of plywood one foot out over the gap, no problem. Then we both stand right in the middle of the piece of plywood, in the middle of the gap=going down!

So the closer the weight distribution of each foot is to the outside of a flexible piece like a snowboard, makes it flex less than if the weight is closer the middle of the board. Shortening the effective edge is like putting your 26″ stance on a conventionally shaped 130 or 140cm board or something like that. Imagine standing with each foot 6 inches from the nose on a tiny board, no matter how soft it was it just wouldn’t bend out too much because of where your weight is.

I think that is part of the reason why shortening the length of the effective edge gives surprising stability in a railed carve without the longitudinal stiffness that you would expect. Rocker profile can also shorten effective edge and shallow sidecut also discourages the board from flexing too deep.

So adjusting stance width (or where a carving plate is anchored to the deck of a race board) can affect the degree to which a board flexes making it effectively softer or stiffer. (The same is true in deep snow where you are riding on the base but it’s then all about surface area distribution and not effective edge. If you are going to have a long nose that projects out a lot in front of your front foot for easy float, it will have to be a bit stiffer not to overflex than when you have a shorter twin tip type nose.)

I agree with all that you said. What you are getting at with increased stability at length are two factors. Longer contact with the snow and longer material length. The Furbergs seem to be a clever cheat that gives them a wide range by design but of course at the real high end there will be differences. I haven’t ridden one but I could see, as Taylor notices, how they could have a lot more stability in hard carves than their flex or length would suggest. If you look at the evolution of world cup skis I think all the answers are shown pretty clearly.

1. Having a longer contact with the snow creates a lot of stability or resistance to swivelling out. All that edge grabbing on to the snow over a longer distance keeps you going straighter (along the arc carved). You just could not go downhill or Super G speeds on a race slalom ski with a downhill sidecut. Well you could, but not before either over turning or having your weight fall fore or aft too much and eating it. (And like you said if grip is weak there are situations where more length of edge gripping could prevent losing an edge by spreading the load and asking less of the snow.)

2. Longer material length is just about weight at a distance from your feet. Rotate a 4 foot long 2×4 and then try to spin an 8 foot long piece back and forth with the same speed.

These are huge effects and cant be ignored. I like to rail turns pretty fast sometimes, I’m guessing 40-45mph or better when conditions are consistent. My older poplar core boards that weigh 9.5 pounds just handle a lot better at higher speeds than my board this year that is just under 8 pounds and the same length. Between boards that I have that are identical but 175 as opposed to 184-187, this difference is not so noticeable at normal speeds (other than float in the deep and dry) but at higher speeds the longer boards are so much smoother, quieter and more confidence inspiring despite the difference not being that huge- I mean it’s just two inches on either end.

The bigger issue for me than length or weight though is how so many boards flex way too deep in a fast pow turn for anything other than drifting through the end of the turn and slowing down unnecessarily.

Yep, and in good 3D snow, I’d say that the actual curve of the board moving through the snow (as the result of its flex and starting curve and mass thrown at the board) and balance of the actual surface area in front of and behind your feet is most determinative of how a board feels and performs, these two elements together maybe 90% from my perspective.

(thread resurrection-got linked back here from Furberg thread- I get all techy this time of year b/c it’s make-boards time instead of ride-boards time for me.)

ieism- these boards fly in low angle probably for two reasons. One is massive surface area with the bulge in the middle of the boards. Two, with a full and deep rockered board on low angle terrain the boards will turn naturally and freely into arcs without having to push the board away from you to bend the camber into a turning arc (especially if you are lighter weight) which displaces more snow than is needed to make a turn and really reduces your speed in low angle terrain. Still, great looking boards they should have Ptex already.

I think boards with high surface area and reverse sidecut are possibly the best design for maintaining speed in low angle pow riding. I don’t ride one just because I’ve cut too many shallow soft slabs off of harder bed surfaces where edging mattered to feel comfortable with them outside of the safest terrain. I also never really know what terrain I might get into in a day because sometimes there isn’t a slab yet in new snow that we were expecting or it only snowed 8″ new where we went instead of the 20″ in another part of the range, etc. So I really just use the same board every day, albeit in the Wasatch where maybe it is easier to use the same board.

If I had some large areas of terrain that were all low angle, like some of those big round Colorado mountains, I’d probably have a super wide reverse camber and reverse sidecut board and take it on those days. But in the Wasatch the low angle terrain is kind of just tucked in between the steeper terrain or there is usually steeper terrain at least right next to the lower angle so there is always a possibility that you might step up your angles once you learn what is going on in the snowpack that day.

Highly technical explanation: