Fin Advice

What works and what doesn't. Share design ideas, references and contacts for paipo board builders.
Atlantasurfer
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Fin Advice

Unread post by Atlantasurfer » Mon Apr 13, 2015 5:11 pm

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Here is my new project. I found a free template for the outline at Blending Curves. As you can see, she is a Simmons type shape, 5' 2" by 23" (a mini platter?). For reference I took a picture with my 50" Ashton. Right now the board is in the garage under some heavy junk getting some some nose rocker bent in. I ordered some 2" polyethylene foam and this FCS kit for attaching fins.
http://www.hydrosurf.co.nz/fcs-ding-rep ... 10556.aspx

I am pretty sure I want to set the board up as a twin fin with a small amount of toe-in (I believe NomasThomas suggested 1/8 inch for use with flat foiled fins).

What fins do you recommend? It should be able to take any FCS two tab. It seems that prone boards just don't need as much fin as a stand-up board. When I looked up FCS fins, I saw that G5s were really inexpensive. At 4.5" depth/height is that a good starting point?
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Re: Fin Advice

Unread post by jbw4600 » Mon Apr 13, 2015 8:07 pm

I have used FCS M7 fins. I think it the same shape but the next size up. What I have found is that a fin smaller than a "7" size fin don't hold enough and anything bigger than a "7" is unnecesary. I have used Futures Aipa twins and T1 (or Twinzers). They were plenty loose, but I found the "7" size held enough and is a little looser. On the FCS site they are M3, M5 and M7. (Futures has a similar series) The M7 size I think is a great size for Paipos. Enough hold, but still very loose. I switched to the True Ames Channel Islands fin. It is about the same size, but it is stiffer and it has a flat inside foil. The M7 has a foil on the inside, which I think causes the board hold a turn too long.

But my board is only 4'3". A 5'2" board might need more fin

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nomastomas
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Re: Fin Advice

Unread post by nomastomas » Tue Apr 14, 2015 4:28 pm

Clever adaptation, Atlanta. Foam thickness should cover fin tab/box, and will allow you to trade-out fins. Don't forget to set the toe-in on the boxes if you are going to use asymmetrically-foiled fins. Fin-size is more determined by rider weight and wave size, so its nice to be able to mix and match. I would agree with JW that you probably don't need more than about 4.6"-4.7" fin depth on a belly board. The True Ames CI template (same as FCS AM2) was designed for heavier riders at long point breaks, like Rincon (AM=Al Merrick=Channel Islands=CI). It has a lot of rake for more projection, so its not very "pivoty", if that makes sense or matters. The "-7" series fins are more upright/more pivoty, but similar in depth. I like pivoty fins on a belly board. The True Ames Side Bite 4.6" is pretty close to the 7 series, too.
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Re: Fin Advice

Unread post by bgreen » Tue Apr 14, 2015 4:36 pm

The less fin the better for me. My boards are 53". My favourite, for a twin fin is these, just over 4": http://scarfini.com/collections/quad/pr ... -dual-tabs

Perhaps I like them because although just over 4" this is to the flex tip. The core is smaller.

I have also tried:

FCS
GL - http://www.finshop.com.au/Products?Prod ... md=Display
GX - http://www.surffcs.com.au/shop/surf-qua ... vAodLj8AaA
PC-5 - http://www.surffcs.com.au/shop/surf-thr ... vQod94wAMg

A board I got from Jeff Quam shipped with M.R-TX -
http://www.surffcs.com.au/shop/surf-spe ... vQodaX8Aeg

DVS
D.V.S 87mm fins - http://www.wetfins.com.au/surfboard-fin ... dvs-smoke/

I've also tried smaller homemade (by Huie).
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Bob

Atlantasurfer
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Re: Fin Advice

Unread post by Atlantasurfer » Tue Apr 14, 2015 8:04 pm

Cool. Thanks for the input, y'all. I like the idea of "pivoty" fins. With a pair of '7''s or similar, what should be my rule of thumb concerning the distance between the tail and the fin boxes? Is 1/8" toe in a solid idea for a twin fin?

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Re: Fin Advice

Unread post by nomastomas » Tue Apr 14, 2015 10:32 pm

Most mini-Simmons twin keels have the keel fins placed about 4" up from the tail. But, you ride a mini-Simmons standing up, with your back foot just in front of the fins. This allows the rider to modulate pressure on the fin and adjoing rail with the rear foot. Prone riders typically use their hip to "weigh" the fin and rail, so I believe that the position of the hip when in the turning position, determines the best location for the fin. If you intend to slide back on the board to turn, place the fins closer to the tail. If you intend to turn from a more forward position, place the fins accordingly. I think often times fins are just placed in a specific location for any one of numerous reasons, and then the rider adapts riding position to maximize turning. That being said, and given the flat rocker of your board, I would think that, in order to turn, you will need to slide far back on the tail. This will elevate the front part of the board, and help you to keep from catching a rail (especially true with the wide-point forward). This argues in favor of placing the fins 3'-4" up from the tailblock. I would line them up with the corners of the tailblock.

As far as toe-in, 1/8" favors speed over turning. Using 1/4" favors turning over speed. With the flat rocker, speed won't be a problem. Sometimes you just have to go with your gut...
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Re: Fin Advice

Unread post by Atlantasurfer » Fri Apr 17, 2015 10:45 pm

When you say 3-4" from the tail block, do you mean the fin box or the trailing edge of the fin?

Sorry if that is a beginner's question. This is all new to me.

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nomastomas
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Re: Fin Advice

Unread post by nomastomas » Sat Apr 18, 2015 3:45 pm

We were all beginners once...standard fin set marks are inches up from the tail to the trailing edge of the fin, and inches in from the rail to the trailing edge. There are a few different ways to measure fin toe-in, where the leading edge of the fin base is closer to the stringer (or centerline) than the trailing edge of the fin base. With "0" toe-in, the distance is equal. With 1/8" toe-in, the leading edge is 1/8" closer to the stringer than the trailing edge. To be fair, some shapers define toe-in in degrees of angle, with 0-deg = no toe-in and 2-deg = about 1/8". The third way is to pick a spot on the nose, say 2" off both sides of the stringer, and point the leading edge towards this point. I use the "measurement off the stringer" method, and employ a tool called thee "Shaper's Square" from FoamEZ to mark this out.

Old school, low-tech method:
1. on the bottom, place a mark on the stringer equal to the distance that you want to set the trailing edge of the fin.
2. Place a second mark the length of the fin-base up from this first mark.
3. Hold a framing square, with the corner at the lower mark, so that the short side of the framing square is parallel to the stringer and the long side reaches across the bottom to the rail.
4. Place a mark on this line 1-1/4" off the rail (or whatever distance you chose).
5. Repeat on the opposite side of the bottom.
6. Measure the distance from the stringer to this mark and write it down. Example 10-1/4"
7. Next, move the square up the stringer to the second mark, and pace a mark equal to the distance you measured in Step 6 minus the amount of toe-in. Example 10-1/4" - 1/4" = 10"
8. Repeat on opposite side.
9. When finished, you should have two marks on each side of the stringer, out by the rail. The marks you have made are commonly known as "the shaper's marks", and can be found on most surfboards if you look hard enough.

Remember, with all fin boxes, the base of the fin that actually goes into the fin box may be a different length than the base of the functional part of the fin (Futures), or just two small tabs (FCS). There are router jigs available for each fin system so that fin boxes can be installed accurately, and these jigs use the shaper's marks for alignment. Go online and find a template for setting FCS plugs. This template should line-up with your marks, so that you maintain the correct toe-in, keeping the flat inside edge of the fin lined up with a line drawn between the two marks. The template will have to be modified to match up with your plug box. Otherwise, with FCS, you will need to measure the distance from the trailing edge of the fin you choose, to the trailing edge of the rear fin tab to calculate where to install your plugs.
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Re: Fin Advice

Unread post by Atlantasurfer » Sun Apr 19, 2015 7:04 pm

Thanks nomasthomas. I appreciate it. I'll post some pics when I get it cooking.

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Re: Fin Advice

Unread post by Atlantasurfer » Wed May 06, 2015 9:10 pm

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This is a tough time in my work calendar, but I finally got this thing going. I used 1" pine as a sort of socket for the FCS fin adapters, then I put the foam on with contact cement.

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Re: Fin Advice

Unread post by Atlantasurfer » Wed May 06, 2015 9:18 pm

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It came out looking pretty homemade, but I learned a lot, and hopefully it will function correctly. I'm heading down to Florida in a week to try it out and see the family.

When I make my next one I'll use thinner polyethylene. 2" is just too much of a good thing. I think this thing is going to duck dive like a canoe. But, even if you horse comes out looking like a camel, there is something so satisfying about surfing a board you make--unless it doesn't work!

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Re: Fin Advice

Unread post by Sparx45 » Thu May 07, 2015 6:58 am

looks good.....hope u get out on it soon !

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Re: Fin Advice

Unread post by Atlantasurfer » Mon May 11, 2015 6:25 pm

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I think I have this Frankenboogie about ready to go.

I began noticing that I had toed one of the fin boxes too much, and I began to wonder if this thing would be hard to paddle (or maybe it would paddle in a circle), So I added a third box. I'm going to try it with some sidebites and an M7 FCS fin. I'm actually still waiting on the postman to bring those fins.

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Re: Fin Advice

Unread post by rodndtube » Mon May 11, 2015 11:04 pm

When do you test drive the FrankenBoogie?
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Re: Fin Advice

Unread post by nomastomas » Tue May 12, 2015 10:58 am

You shouldn't need the center fin. Worst-case, your board will turn easier to the side with the most toe-in, and go faster (in a straight line) on the side with the lesser toe-in. Just tell people that the board features an "asymmetric" fin configuration...
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Re: Fin Advice

Unread post by rodndtube » Thu May 14, 2015 11:53 pm

The FrankenBoogie Ripper pocket player.
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rodNDtube
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Atlantasurfer
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Re: Fin Advice

Unread post by Atlantasurfer » Mon May 18, 2015 12:03 pm

Someone also posted some video of my Florida surf trip. This one has some cursing, so you might not want to play it at work.





https://www.youtube.com/watch?v=Ig1ytto6rNg

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Re: Fin Advice

Unread post by Nels » Mon May 18, 2015 9:54 pm

Okay...that's ME! Awesome video. Even watched the next one up, which is the same clip with a little more at the start to give it a real beachy flavor.

https://www.youtube.com/watch?v=x4e53wnInX4

Atlantasurfer, may you receive a thousand waves in return for this gem.

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Re: Fin Advice

Unread post by rodndtube » Mon May 18, 2015 11:24 pm

Please do NOT make those promises to AtlantaSurfer. He may end up thinking he deserves them!!
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Re: Fin Advice

Unread post by Nels » Tue May 19, 2015 10:54 am

I don't know, Rod, that was a really funny clip. Just the thing to start summer off with. Atlantasurfer deserves something. Maybe "wave of the day" ...

But then again, I'm on the West Coast...a thousand waves in the Atlantic? :twisted:

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