Darrick wrote:

Thanks for the picture @permnation. So the wide points are at the ends of the effective edge correct? I have seen Furburg specs that show two effective edge lengths. Is one the beginning of the taper and one at the end? The reason this is interesting to me is that I have been making my own boards since last winter and for a few years I have been nerding out on board design. I completely understand the merits of the furburg design, I just want to understand the taper aspect so I can try it out on my own boards. Any other info would be greatly appreciated.

Furberg’s use of the terms ‘reverse sidecut’ and ‘taper’ refer to what might be more accurately called an extended transition at the nose and tail. Many current boards have this design element, but not to the extent that Furberg employs it.

This long transition helps make a board less hooky. It also creates a board with more float in powder (long nose) and a short effective edge for maneuverability, which is probably an important design parameter on a board with an 18m sidecut that is designed primarily to make slarved turns on firm snow.

The end of the effective edge is generally a relationship between the wide points of the nose and tail and the rocker design. In the full cambered days where the camber ended at the wide points of the nose and the tail, the effective edge also ended at the wide points of the nose and the tail. In today’s designs, every board is a bit different and the effective edge usually ends varying distances before the wide points of the nose and the tail. This creates smoother riding boards. Generally, a more aggressive board will have a longer effective edge and a more playful board will have a shorter effective edge. Furberg, with its 18m sidecut and short effective edge is striving to be both aggressive and playful.

I have two measures of effective edge that I use to try to get an idea of how loose a board will feel during transitions and how much effective edge I will have when I put the board on edge. The first one is, where are the contact points when the board is on a flat surface. Generally, the shorter this length, the looser the board will feel (depending on torsional and longitudinal flex) during transitions and the less likely a board is to catch an edge. A short contact length when flat does not mean the board will have a short effective edge when riding. That will in part depend on the rocker / camber profile.

The other test is with the board slightly on edge on a hard flat surface and the camber pressed out (if there is any). Generally, the longer the edge contact, the more locked in the board will feel when you put the board on edge while riding. A board with gentle rocker can still have a long effective edge.

The G3 I had was ever so slightly rockered the whole way but because the rocker was so slight, it had full edge contact when I put it slightly on edge and is a fairly aggressive board (it is also very stiff).

On the Jones Solution, the nose and tail rocker is steep enough that the effective edge ends well before the wide point of the nose and a little in front of the wide point of the tail. It is more playful.

The Amplid Milligram’s effective edge ends quite a bit closer to the nose and tail wide points than on the Jones Solution when the board is put on edge.

The Furberg has a fairly short effective edge for its overall length. I have the first generation Furberg and the effective edge ends before the wide points of the nose and tail. On firmer snow, the ‘reverse sidecut’ area is beyond the effective edge and does not contact the snow. The softer the snow, the more nose and tail length beyond the end of the effective edge will contact the snow.

This is a 172.

In both images the key pinpoints where the rocker begins to rise from a flat surface.

In the shovel, there is roughly 15 cm of edge that is almost straight, nearly neutral sidecut fore of that rise point, before the shovel starts to curve in. The widest point of the shovel is at the “u” in Furberg.

In the tail the rocker begins to rise from a flat surface in roughly the same place that the tail starts to curve in.

I think “taper” is getting misused a bit in the last couple of posts.

Taper has traditionally been used to describe the difference in width between the nose and the tail of a snowboard. A common twin tip park board might be somewhere in the neighborhood of 30cm at the widest point at the nose and tail and 25cm wide at the narrowest part of the middle of the board. Since the board is 30cm at the nose and 30cm at the tail there is no taper. A common “pow” board might be something like 31cm wide at the nose and 29cm at the tail with the same 25cm at the waist. This would be a board with 20mm of taper.

I think the original Burton Fish had ~20mm of taper between the nose and tail, the Option Pintail was ~15mm and the Northshore was ~25mm if I remember correctly. Almost all of the current pow shapes do this. It shifts the center of surface area of the board forward, usually in combination with a long nose, short tail and a set-back stance which shifts the center of stance back. You end up with a board that you can ride with your weight centered on your feet or even biased towards your front foot but still have good float in pow.

A quick note on the Furberg, which is now my go-to resort board…

One thing it does really well, which just baffles me, is rail large radius, high-speed turns–even on steeper, tough-to-stick pitches. It holds highly angulated heel rails, without folding, on a pencil-thin line. For me, that’s typically reserved for longer boards with carving-oriented, or forward-favored geometry. That the relatively short and flimsy Furberg does so is just astonishing, and yet another nod to the virtues of long sidecut radii and even edge pressure.

HansGLudwig wrote:

Furberg combines the two shapes like this. . .
The green line is the edge of that 18 m circle. The red line is the edge of the reverse sidecut circle. The blue is where both circles don’t touch and transition the radii with nominally straight edges.

This is a rough sketch and I’ve exaggerated the curves but that’s the general idea.

@HansGLudwig, I am pretty sure the ‘reverse sidecut’ on the Furberg begins at the widest part of the nose and tail. Otherwise, it is a part of the sidecut curve (although an increasing radius part).

HansGLudwig wrote:

It all seems to me to be a really fancy way to describe elongating the widest parts of the tip and tail.

This.

Jim, it is pretty far back in time now. This is the main reference I am finding at the moment. It is from Alpinecarving.com.

“Burton Fish: For ’05, the 160 cm length had 40mm of taper, which was reduced to 30mm for ’06..”

That would be a scary chute on the Fish! Glad you’ve moved on to a Spliff! ; )

Taylor, you are making me want to try one on the groomers with the kids.

” and yet another nod to the virtues of long sidecut radii and even edge pressure.”

maybe its not so much spreading the edge pressure even as it is keeping it close to your feet, limiting the flex of the board in a powered up carve by virtue of a larger amount of effective edge between your feet than outside of your feet. Cool. Nice range of stance options on those boards also.

If pressure=force over area, then a shorter effective edge should dig in deeper/easier to resort snow and hold better right? Stability at speed comes from the nose and tail not contacting much and thus not flapping around or hooking into too tight of a radius, the long radius, and not much edge far away from the feet (as opposed to standing with a tighter stance in the middle of longer and stiffer carving board).