Keels look like the fin that never changed: the same low, long shape on every fish since the seventies. The ten sets on this wall disagree. They span an inch of height, nearly two inches of base, two different foils and a published cant figure, and they split cleanly into two camps that ride nothing alike. This page is the difference between them.
If the question is still twin or quad or thruster, that's the twin fin guide's job. This page assumes twin boxes and a wide tail, and picks the keel.
The quick answer
| Your board, your wave | Take |
|---|---|
| A classic fish, and you want it to feel like one | Hobie Fish |
| Points and long walls — low, fast, drawn all the way out | Mackie Sidecut |
| A modern performance twin shape | Channel Islands AMK |
| You want keel drive without the tracking | Wayne Rich Nightmare (Futures; the FCS version is its own listing); the quieter version of the same idea is the McCallum Keel |
| Glide and trim over everything | Danny Hess Noriega |
| A hybrid twinnie that sits between keel and upright | Lovelace Piggyback Keel |
How a keel works, in one minute
Every measured fin on this page is wider at the base than it is tall. That is the whole design, and nothing else you can bolt into a twin box does it.
A fin's base runs along the board's rail line, so a long base acts like a short extension of the rail itself: it resists sideways slip along the whole line the board is trying to travel, which reads underfoot as drive and hold. Keeping the fin low puts that area in solid water under a wide, shallow fish tail, and the swept rake carries the turn out long instead of snapping it around. That is why a fish trims so fast and turns in arcs.
The trade is pivot. A long base resists rotation the same way it resists slip, so tight, tail-pivot turns cost real effort — the more keel, the more the board wants to draw its turns. Every set below is a different answer to how much of that trade to take, and the differences are large enough to publish.
The numbers
The hero above is the honest version of this section: the six measured keels at true relative scale. The differences that matter are visible — how low and long the Sidecut runs, the Nightmare's hatchet — and the figures behind the picture are here if you want them.
The published numbers, per fin
| Set | Height | Base | Area | Base ÷ height | Inside foil |
|---|---|---|---|---|---|
| Mackie Sidecut | 4.69" | 7.80" | 22.45 in² | 1.66 | not published |
| Tyler Warren Modern Keel | 5.25" | 7.30" | 25.25 in² | 1.39 | 80/20 |
| Hobie Fish | 5.25" | 7.25" | 26.16 in² | 1.38 | flat |
| Danny Hess Noriega | 5.04" | 6.30" | 24.56 in² | 1.25 | not published |
| Channel Islands AMK | 5.17" | 6.38" | 26.07 in² | 1.23 | not published |
| Wayne Rich Nightmare | 4.88" | 6.00" | 25.81 in² | 1.23 | concave "football" |
Keels come as sets of two; figures are per fin, as their pages print them. Six of the ten designs publish a full block; the other four publish nothing and are placed by their maker's own description instead.
Two readings. First, the areas barely differ — 22.45 to 26.16 in², a spread you could cover with a playing card — so a keel choice is not a size choice. The base-to-height ratio is the real axis: above 1.38 sit the true low-and-long keels, and around 1.23 sit the taller hybrids that give back some pivot. Second, the ratio agrees with what each maker says its fin is for, fin by fin, which is what makes it worth sorting on.
The shelf runs $108.50 to $118.50 as of 13 August 2026 — a ten-dollar band. Price decides nothing here; the ratio and your boxes do.
The classic camp: low, long, drawn out
Hobie Fish — 5.25" tall on a 7.25" base, the biggest area on the page, flat inside foil. Its page calls it the maker's most popular keel set and "an industry standard for pairing with fish surfboards," an early-'70s San Diego template drawn with Hobie Surfboards — "wide base and large sweeping profile … ideal for down-the-line surfing and free-form style." This is the reference point: the keel the others are deviations from. In both box systems, nine colorways.
Mackie Sidecut — the extreme of the camp: the shortest fin here on the longest base, a 1.66 ratio nothing else approaches, with the least area. Mick Mackie drew it low and heavily raked for "fast and smooth surfing with heaps of drive and down-the-line projection … boards that love a long drawn out wall or point break style surf." The name is literal — the trailing edge steps in a sidecut. Maximum trim, minimum pivot: the point-break keel.
Tyler Warren Modern Keel — the Hobie's proportions drawn for "the modern twin fin shape," with an 80/20 foil and RTM Hexcore construction — "super light" with "excellent flex characteristics," their page says, and it is the one keel here not built in solid fiberglass. The classic outline for a board shaped this decade.
Gephart #2 and Gephart 70/30 — Larry Gephart's templates from the glass-on era, remade in fiberglass for Futures boxes "true to form." The #2 keeps the 50/50 foils of the original marine-ply fins and is the only fin on this page that publishes a cant figure — 4 degrees. The 70/30 is named for its foil. Neither publishes dimensions; both are bought on provenance — the closest thing here to the fins that were on fishes the first time around.
Wild Things 4.8 Volan Keel — the wildcard: a 4.8" Volan keel twin from Byron Bay's Wild Things, the one non-True-Ames set on the shelf. Its listing publishes no dimensions, so it sits here on its name and its glass.
The hybrid camp: some pivot bought back
Channel Islands AMK — Al Merrick Keel: "classic keel fin glide, but also elevated turning ability for quicker redirections," drawn in-house with Channel Islands and "finely tuned for high performance surfing." Near-Hobie area on a much shorter base — keel drive with a modern twin's manners. The two-tone colorway runs five dollars over the plain white, as listed.
Wayne Rich Nightmare — the "swept-back, hatchet style profile" reaches for "maximum drive while still allowing for release and maneuverability without tracking," and the inside face carries the page's concave "football shape" foil "which provides extra lift and reduced drag" — the most designed surface on this page. Its own copy names the buyer: "a hybrid-keel alternative to spice up your twin fin." Separate SKUs per box system.
McCallum Keel — Jeff McCallum's "modern interpretation": traditional keel base length, added rake, "overall reduced surface area … a somewhat narrow tip and less wetted surface" for "greater performance and more release compared to a classic keel fin." The same promise as the Nightmare made the quiet way — by removing material rather than sculpting the foil.
Lovelace Piggyback Keel — Ryan Lovelace's bridge, in his page's words "between a wide-base traditional keel and an upright late '70s style design," made "to work fluidly with performance hybrid-style twinnies." If your twin is a hybrid rather than a fish, this is the keel drawn for it. Both systems.
Danny Hess Noriega — the balanced one: mid-pack in every measured column, "created for endless down the line speed, glide and trim … smooth arcing turns and easy transitions for any fishy type craft." Where the AMK spends its hybrid shape on turning harder, the Noriega spends it on gliding longer.
Their maker also builds keels this shop doesn't stock — the Pinder Half Keel, the Neal Purchase Jnr. Cutaways, the Dice glow-panels, and the glass-on family the boxed fins descend from. The wall above is what you can bolt in and ride this week.
How to choose
Start from the default: the Hobie Fish is the reference keel — the template its maker calls the industry standard for a reason, and the middle of every measured column but area. Every other pick below is a deviation with a condition attached.
A classic fish, ridden the classic way. Hobie Fish. Drive off the bottom, speed in trim, arcs instead of snaps — the feeling people buy a fish for, from the template that defined it.
Points and long walls, and you'd trade your last snap for more speed. Mackie Sidecut. The lowest, longest, least-area keel here. On a wall it is the fastest thing on this page; in a beach-break pocket it is the wrong tool, and that's the deal you're signing.
A modern performance twin. Channel Islands AMK. Keel glide with real redirection — the set drawn for boards that want to be surfed hard, not just trimmed.
You want keel drive without the tracking. Wayne Rich Nightmare (Futures; the FCS version is its own listing); the quieter version of the same idea is the McCallum Keel — less area where the Nightmare adds foil.
Glide and trim over everything. Danny Hess Noriega. The most balanced numbers on the page, spent on flow rather than fight.
A hybrid twinnie rather than a true fish. Lovelace Piggyback Keel. Drawn for exactly that board — the keel that meets an upright template halfway.
If none of those conditions is yours, it's the Hobie, in whichever system your boxes take. A keel rewards commitment more than comparison: pick one, ride it until the board's arcs feel like yours, and only then decide whether you want the shelf's faster end or its looser one.
Sources
Product pages for all eleven listings on both stores, read 13 August 2026 — heights, bases, areas, foils and the Gephart cant figure as printed there (six designs publish full blocks; the unit conversions on all six check out). Shelf prices from our catalog the same day. Working, including the derivation of every ratio, on file.
