How to pick a cheap fin for an old board?

[rfromm]

I was sailing at Berkeley on July 4th weekend, enjoying the wind, when all of the sudden there's a loud cracking sound and I totally lose control of my board. My fin snapped off by the base. (And I learned how hard it is to try to sail without a fin.)

So now I need to buy a fin. My board is a old Astro Rock. And after reading the Bic Astro Rock's Legendary Status thread, I bet that the response here is going to be that I should just get a new board. And I definitely could use a smaller board (I'm wondering if it's holding me back), but that's another discussion. In the meantime, I want to be able to ride my existing board, but it's not worth it to spend a lot of money on a fin that's going to be worth more than the board. So definitely used, but that still leaves plenty of (perhaps too many) options.

Looking around at what people are advertising for sale, I'm a bit daunted by how many sizes and styles of fins exist. I suspect that the answer is that maybe it just doesn't matter, if I'm not a good enough sailor to be able to tell the difference. But maybe it does, which is why I'm asking. (And do all fins attach the same way, or is an older board going to be different? I could attach a pic if it mattered.)

I weigh about 150 pounds. I sail in the SF Bay area, Berkeley being where I go the most. Other than a 7.something (7.2?) that I almost never use, my sails are 5.0, 5.7, and 6.3 m^2. (And I believe they're all of roughly the same vintage as the board.) I'd consider myself an intermediate sailor (no problem water starting and planing; comfortable and enjoy a reasonable amount of chop; I'm satisfied with the quality of maybe about 50% of my tacks; my biggest weakness is that I really need to learn to how to jibe for real).

Any advice?

[jp5]

Does your fin box have the spacers in it which move back and forth to allow for fin placement? If it does then that box is a Power Trim box. I have an old pointer fin for that which should work just fine. PM me if interested.

[pjs]

Here's a little video on fin box types. Although, they're missing a few of the strange old types.

http://www.youtube.com/watch?v=sJL_Pwn130s

[swchandler]

If I recollect correctly, the Bic Astro Rock used a fin base style very similar to the A box, which was the first fin on the left in the video provided by pjs. However, it would be slightly different in that the Europeans used what was called the E box. The difference was that the base depth was just a bit deeper. I believe that you can get by with an A box fin, if the roll pin is located in the right position, but it's appropriate to use a spacer of some kind to make up for the difference in depth. If the roll pin is not positioned correctly, it's very possible to remove the existing roll pin, drill a new hole in the right position and press in a new stainless steel roll pin.

Hopefully you still have what remains of the old fin base, assuming the fin sheared just above or flush with the finbox. This would allow you compare the old fin base with a new or used A box fin, to discern what modifications might be needed.

[bigron]

i have a nice fin in new condition i can sell you for $40 in san jose
it has two deeper nodes to fulll the box better and sliders on both front an back you should not get a fin longer than 14-15 incches for the aluminum tracck box as the torque will rip out the fin box on a hard jybe
so a wider base in important for tracking. send an email to bigronsurf@yahoo.com and i can scan the fin for you and send jpeg

[LeeD]

Ebox.....
BigRon is right, but for your weight, no more than 12" maximum, cause bigger will rip the finbox right out.
You can cut down a longer fin too.....

[d0uglass]

I had a bic electric rock which has the same finbox as the astro rock. It will take a standard "US Box" fin, also known as an "A box" fin, but you may have to put a slice of an aluminum can or some layers of packing tape around the base of the fin to make sure it fits snug.

Used US box / A box fins are very easy to find at any windsurfing shop that sells used gear. You'll want to pick one in the 30 - 35 cm range (12" - 14"). I have used up to a 40 cm fin in a US Box, which was a good match for my 7.5 sail (bigger sails need bigger fins), but that was definitely pushing it since the box isn't strong enough to resist the torque from a long fin.

As for fin styles, you don't want to get an extreme raked fin like a wave or weed fin, but you don't want a narrow upright fin like a slalom fin, either. Something with a moderate curve and fair amount of width should work well.

... Just as a side note, you could probably find a good board 5-10 years newer than the Astro Rock for under $250.

[rfromm]

[rfromm]

[jp5]

I had one of the type A finboxes in an older Fanatic and used a longboard surfboard fin in it.