Thruster set, three 4.8″ fins, set area 30.42″ sq.



  • Total area, set of 3: 30.42 sq. inches
  • Area per fin: 10.14 sq. inches
  • Height: 4.8 inches
  • Rake/sweepback: 22 degrees
  • Stiffness: Semi-flex or stiff
  • Colors: Glossy black, blue, or matte black
  • Fits FCS
SKU: FSI-07 Category: Tags: , ,


FinSciences 4.8 inch fins in a three pack have 30.42 square inches in area for the set, and are for use as a smallish-sized thruster set for those who want a lot of speed, easy wave-catching, and a looser feel.  These fins still have a lot of control, drive, and power by virtue of their design.

Our concept is to take a typical fin, chop off about 30 percent of the fin’s least-efficient area, then add back a few percent in ways that it’ll do the most good.  So our fins are a bit smaller than others’ fins, and they look different. But they resemble airplane wings, race-car spoilers and boat keels–because we share the same high-tech design concepts.

We recommend starting with this setup if you’re looking for a change from the everyday hum-drum thruster setup.  And you might get a single larger fin (the 5.8-inch fin) to mix, match, compare, and allow for shifting gears in different conditions.

By way of comparison, a typical 4.25-inch fin set has about 14. 5 square inches in each fin, for a total set area of about 43.5 square inches. 

This set of three FinSciences fins has an area of 30.42 square inches–a whole lot less fin area to drag around that you’re used to! 

Note:  Some photos show smalls in combinations with other fins in thruster, quad, and 2 + 1 setups.

Shortboard Fin Small Specs:

  • Total area, set of 3:  30.42 sq. inches
  • Area per fin: 10.14 sq. inches
  • Height/depth: 4.8 inches
  • Rake/sweepback: 22 degrees
  • Foil section: symmetrical (double)
  • Winglets area alone: 0.9 sq. inches
  • Planform area alone: 9.75 sq. inches
  • Fits FCS

Sizing of FSI Fins Compared to Typical Fins

Our fins have a lot of power. They generate a lot of hold and drive for their small size.  (Read more about hold, drive, lift and drag.)

Because they have a lot of power, your right-sized FSI fin will have an area smaller than what you’re used to.  And because they are smaller, they have less drag.  This means that you can accelerate more quickly, paddle more easily, or surf longer.

Winglets/finlets and other features we use make these fins about 20 to 30 percent more efficient than larger, older styles, so you need to downsize by about 20 to 30 percent as compared to the fin or set of fins you typically use.  See

Example: If you typically surf a set of mediums in a thruster setup, fins that are usually about 14.5 sq. inches each, you are surfing 43.5 sq. inches of fin. Our smalls are 10.14 sq. inches, and a set of three is 30.42 square inches, a 30 percent reduction in fin surface area, and a 30 percent reduction in skin-friction drag.

Another example: If your longboard or SUP board has a center fin and two sidebites, calculate the area, then try downsizing–try pulling off the sidebites and going with a single Wavegrinder 2 longboard-SUP fin. You will dramatically decrease the area, yet still get good hold and drive because of the winglets and other features of our fins.

FSI Fins, Areas in Sets

Because FSI’s current fins are symmetric, you can either get a set of the same fins, or mix smaller and larger fins to get the ride you want.

Fin type FSI size Area, each Area, set of 2 Area, set of 3 Area, set of 4
Shortboard fin Small 10.14 sq. in. 20.28 sq. in. 30.42 sq. in. 40.56 sq. in.
Shortboard fin Large 14.58 sq. in. 29.16 sq. in. 43.74 sq. in. 58.32 sq. in.
Longboard-SUP fin  Wavegrinder 2 30.60 sq. in. 61.20 sq. in.    


Additional information

Weight 6.6 oz
Dimensions 5 × 3 × 1.0 in
Select a stiff-and-color combo, the ADD to CART

Stiff, in matte black, Semi-flex, in gloss black, Semi-flex, in translucent blue


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