thick dark strip on bottom of foil boards

[liv2surf]

what is the composition and function of the thick dark strip to the nose-ward side of the foil boxes visible on the bottom? I have a production board with two full length 1/4" stringers connected to the outer side of the foil boxes.

[DavidJohn]

I’m guessing it’s carbon fiber and there to add stiffness to the board.

The glass or skin on the bottom of boards is usually very thin because the surface is supported evenly across the whole bottom buy the water and it’s usually under tention like when you stand in the middle (on the top) pushing down but if you were to flip the board over and stand on the bottom this puts the bottom skin in compression and a crease would normally be the result..

I’m thinking this carbon reinforcement strip not only acts like a stringer but protects against these tension/compression forces.

[surfcowboy]

It's carbon, yes. And think about pumping. Unlike standing in the middle on a surfboard which is stretching the bottom skin, you are actually potentially compressing it (greatly) if you have your feet apart and press down hard which you do while pumping. Especially if you're bridged with a foot behind the mast.

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[liv2surf]

My no-name 'production' foil board has 2@ 1/4" thick parallel stringers on the outside of the foil tracks (foil tracks are installed up against these) which go tail to tip and I think goes from bottom to deck (they show on the bottom, I can't tell if they are full depth).  These would seem to be low tech analogs of the carbon in the picture?

[surfcowboy]

Yes, stringers for stiffness. But in that case they are also likely tying the boxes to them so they serve 2 purposes, stiffness in the board and keeping the foil from ripping the boxes out. My orange board is constructed like this.

[liv2surf]

I believe I have heard that with foil boards there is a desire to link the foil forces to the deck and board so it can be more effectively linked to the rider. Does this make sense? Can anyone articulate this better?

[liv2surf]

what is the CONSTRUCTION of the thick dark strip to the nose-ward side of the foil boxes visible on the bottom? Is it a foam wedge wrapped in carbon dropped into a recess?

[TallDude]

It looks like a painted graphic. Maybe exposing a bit of CF for that sense of strength. They sound like they are built pretty strong.