If they had powerboxes in them you could put a decent pointer fin in them for freeride.
What's the advantage of a US box?

A lot thinner

I didn't think they made any more upright fins for US box but found a few..Would putting a more upright fin in a smaller Kode make it better for B & J . allow earlier planing and better upwind but still keep a nice gybe and control in the chop?

Adjustability. Powerbox fin means the fin is locked into one position. With a regular US box you usually have some small adjustment options.

There are some idiotic exceptions to this though. Goya for some unexplained reason used mini US-boxes on their large size wave boards. The result was that you couldn't fit standard US box fins. And even mini US-box fins had no room for adjustment.

fore-aft adjustment is the primary reason. If you see a modern board with US boxes chances are its more geared towards wave sailing. Wave boards are all about turning & have specific rocker through the back of the board, moving the fin(s) back-forward in the tail section allows personal adjustment for turning, rate at which a board planes, water conditions etc... so power boxes remove this flexibility. You can have different fins that go someway to adjusting the capability of the power box board, you just end up with a stack of fins to muck around with, my experience is match a sail with a fin to get the most out of a free-ride/wave board.

AFAIK, powerbox, gets in the way of the rear foot strap, with smaller boards.

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sboardcrazy said..
I didn't think they made any more upright fins for US box but found a few..Would putting a more upright fin in a smaller Kode make it better for B & J . allow earlier planing and better upwind but still keep a nice gybe and control in the chop?

Absolutely!

The powerbox should have never happened when the Tuttle box design was a available to all.
The last wave board I built in 1994 had a Tuttle box that was too far back and had to re install new Tuttle box under back foot strap.
The US box is great for wave/jump boards if 100 liters or less with fins max length 300 mm but average 250 mm and can move smaller fin underneath your rear foot for maximum foot steering or further back for maximum speed.

US box as mentioned by some good posters above is good for adjustability fore and aft. However also weight is lighter (or should be) and tail can be thinner.

Agree with most posters,
it exists because the tail at the time was thinner, it offers adjustability as well. It's strength was ok , because the fin size was small. It's used as a multi fin box , and usually shortened, in this case it's much cheaper than a slotbox/ star box.

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sboardcrazy said..
I didn't think they made any more upright fins for US box but found a few..Would putting a more upright fin in a smaller Kode make it better for B & J . allow earlier planing and better upwind but still keep a nice gybe and control in the chop?

That advantage here Sue is in the 1990's there was a lot of elliptical pointers in US box that can be quite fast. Nobody really wants them anymore.... so if you want a US box freeride or slalom fin they are really cheap!
I often see good examples in the shops for $20-$50
Ring around and u may score
Else, anything can be converted easily by simply sanding it down to a flat 3/8" thick base. The front tab is a screw-on stainless fitting that is still around if anyone can rememeber what it is called...?

Thanks everyone. Makes sense.
It's hard for smaller sailors to get small freeride type gear.
I've got an old 68litre starboard acid which is good but we rarely have consistent enough wind.
Probably after c 80 -85 ltre board comfy in Lake sailing in 2 -4' chop / rollers .
Prefer control and comfort in those conditions, something I can try and get back into chop hops and goes upwind well.
Currently sail slalom boards and I don't want to be on the edge in those conditions.

You need a JP or RRD FSW 85 from about 2008-10

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Mark _australia said..
You need a JP or RRD FSW 85 from about 2008-10

Thanks..

Why would you even want to put a pointer fin in a wave board, Its a wave board.

You can adjust the fin possition in a US box.

Because I can't find a small enough freeride board and I have to compromise with a wave type board but I want more slalom / freeride upwind performance.
Maybe modern boards are better. I know my 2004 78ltre Tabou pocket wave didn't point as well as the 2008 79ltre Falcon I replaced it with. I'd probably be buying an older board..

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sboardcrazy said..

Mark _australia said..
You need a JP or RRD FSW 85 from about 2008-10

Thanks..

Mark's right, that's exactly the board you want and for hi wind lakes/chop stuff (which is where people use wave boards with pointer fins, PC simpson) this is the fin.
Even the bigger sizes are still ok in lots of wind.
I (75kg) use a 29cm which honks upwind and is still ok with a 4.0 sail, 35+kt winds

Thanks. Sounds like the modern ones come with a powerbox..

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sboardcrazy said..
Thanks everyone. Makes sense.
It's hard for smaller sailors to get small freeride type gear.
I've got an old 68litre starboard acid which is good but we rarely have consistent enough wind.
Probably after c 80 -85 ltre board comfy in Lake sailing in 2 -4' chop / rollers .
Prefer control and comfort in those conditions, something I can try and get back into chop hops and goes upwind well.
Currently sail slalom boards and I don't want to be on the edge in those conditions.

Hear you! I am 70 Kg and it took me a while to find a 80L board, most stop at 85 or jump to 75 that is too small for the conditions I sail in. I got a Starboard FSW 80 last year, it is a great board but unfortunately it is now out of production. Consider a Flikka costum, they are "cheap" and very well built ... and do get US box, under 5.0 it is nice to have the option of move your fin.

Another advantage of US Box if you hit rocks etc hard enough, the fin can break out of the box instead of ripping out the whole rear end - no guarantees, but eg Maui Ultra fins have this design feature ....

This is quite complicated to answer because we have different boxes that have developed over time.
The longer the fin you use the more it places torque load on the box, so with slalom and big freeride kit you need a deeper box for the longer fin - in exactly the same way that you need to concrete a fence post deeper into the ground if the fence is higher.

Wave fins can be quite short, and even single fin set-ups often require no more than 24cms or 25cms max nowadays. If however you use a 6m rig often, then you may benefit from a longer fin and the US box is ultimately too shallow for that - and a Power box or Tuttle box would certainly be safer for fins of 30cms and over.

As has been said, the advantage of the US box was and is that you can move the fin fore and aft, and that's then a tuning option to match the footstrap hole positions offered on your board and the mast track options for the mast foot.

The US box is still seen in many boards but has been superceded by the 'slot box' and the 'star box' in many wave boards. These new boxes are for the short fins typically used in multifin wave kit, and the new boxes still allow a bit of fore-and-aft adjustment.
Some tri fin boards often come with short slot boxes for the rail thruster fins., whilst having a US box for the centre fin. That means you can ditch the thrusters, fit blanking plates, and just go old school single fin for early planing in marginal wind - like with a 5.3 sail or bigger.