Single fin thickness

General Discussion
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Many years Ago I made a 9" lacewood fin for a longboard.  I foiled it, sealed it with epoxy, and never finished it.  Its outline was a cutaway base model that were more popular in the 90’s than today.  About a year and a half Ago I busted it back out, glassed it, haloed it with carbon fiber, and put it on my favorite longboard, and really liked it.  Lost a little drive but gained some sensitivity compared to a more traditional fin without the cutaway at the base

I rode it for about a year, and then on a super small day was kicking out and drove it into the sand, and broke it about an inch above the base.

Recently I have been making some other fins, and rather than wasting  extra mixed epoxy, I decided to use the excess to put the broken fin back together. I cut tapered grooves into the wood across the break and filled them with woven roving, then glassed over them with about 8 or 10  layers of 1.25oz cloth on each side on the base, and less over the tip.

At this point the fin was nearly 3/8 of an inch thick at the base, and I got it to fit nice and tightly in a FU box, and stressed it.  Way too much flex at the base for my liking.  It would both lean over and twist in a manner I had never seen any other fin do, and while interested in performance, I feared it would just break again above the previous break destroying considerable effort to repair it in the first place.

I only have 1.25 oz cloth on hand.  I taped off the base, then layered about 12 more layers of cloth so that there was 12 layers over the cut out at the base, and only 1 additional layer at the tip, and when the epoxy was razorable, I cut it at the tape and removed the excess.

Now I have nearly 3/32" overhang over the box on each side of the fin.  Still need to sand it and finish coat it, so I am not  yet sure how much stiffness was added, but I think the ~ 1/2 inch total thickness will only help with drive and projection on an old school type of longboard ridden traditionally.

What’s the thickest fin one would recommend before it becomes too thick?

I acquired the 1.25oz cloth hoping to gain more clarity and not obscure the grain of the wood so much. I’ve failed, so far, to achieve this, but function before fashion is what I tell myself.

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http://www.swaylocks.com/groups/thick-fins-vs-thin-fins

http://www.swaylocks.com/forums/whats-correct-fin-thickness

Some light reading.

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I have a wood longboard pivot fin I made, that I intentionally left thick, at least a half inch.  it worked great until I busted it off the tab. The tab was an experimental product that was discontinued because of being too brittle. 

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Thanks for posting those links RDM. ‘light reading’ for sure.

 

Huck, I’ve had a few single fins snap just above the box.  I’ve employed long SS screws through the base of the Fin, but SS is not rust resistant when not exposed to oxygen while encased in epoxy, and they just move the breaking point up higher.  I’ve experimented with all sorts of methods to increase strength in this area.  Generally there is way too much labor into each fin, but so be it.  I’ve not purchased any fin in 15 years. But when they break there is lost of lost effort.

 

Lately I’ve been employing tapered grooves filled with  CF or fiberglass roving from base  upwards on both Single fins and FCS fins.  The roving did break on the fin posted above though, but well above the base.  I ground it out and made it deeper and longer on the repair, but should have gone further.

I guess I should go sand it now. and apply  another hotcoat, while I wait for the Mem day Hordes to vacate the ocean.

 

I am seeking no flex from box to fin and no flex at the base of the fin, only at the tip, and as I weigh 220 Lbs, I prefer less flex.

My FU boxes are greatly reenforced too.  I have a theory that the less flex betwen foot and fin, the better the response and control.

 

 

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5/8" thick or so.  Works excellent.  Bill Thraikill concept.  Warrior 1515 the fin foiler.  Mike

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Here is another thick foil from bill. 

Can’t wait to get it in the water. Should only be a week or so till I finish glassing the Edwards template it’s going in.

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Paul Jensen likes thick fins:

http://www.swaylocks.com/node/62027

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I’ve had fins that were pretty thick. One was wood with a glass core. The glass center was standard thickness for an FU box and the wood was added to both sides, then foiled and glassed. The outline was the Brewer thick foil that is still around today.

Funny thing, I was just thinking about building some fins again. Was pricing resin online this morning. Haven’t built a fin in years. Looking to do some wood fins similar to waht I described above. Glass core with wood as the outside layers. That method is much more snap resistant.

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This is the fin I described, above

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Here are three Fins Unlimited fins from the mid 70s. Note thickness specs. As much as 1". None less than 3/4"

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Love that Koa wood fin.

 

Wow, 1 inch thick fins.  Do they have any flex?  Was the polycarbonate part of the reason for going this thick?

Mine has been sanded and I’m likely in the 1/2 inch thick range, forgot to bust out the calipers.

Certainly stiffer at the base, but lost a lot of clarity.  Oh well, I’ll have to make another, someday, and make it thicker.

 

I did make one 7.5 inch Fin out of IPE wood, that has glass in the middle.  That one was a lot of work, and still I did not get the cloth to disappear. 

 

 

 

 

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12

12.5 years ago, I built a 21# traditional railed/rockered 9’6" HWS, and universal opinion was that it rode like a dog.  That was my impresson, and my friend’s impressions, and I was very disappointed.  I made a few half ass attempts to sell it what it was worth to me, failed, and put it in storage rarely to see the light of day.

I’d built a 9’7" HWS that became my best friend soon after.  The 9'7" is now in drydock for sealing the little dings and re enforcing a few areas on the deck, the Lacewood fin, now significantly thicker at just under 9/16", the topic of this thread, is in the 9’6" dog all the way back, and I took it out today.

I saw all those little imperfections in the shape of the Dog as I stretched, and convinced myself I’d be putting it back in storage and the rebuilt thicker fin in my favorite 9’7", but the Dog, did not bark.  It accellerated as I walked up the board.  I do not remember it doing that before, my main complaint.  It had all sorts of glide, and turned well. 

Long story shorter, I actually got one of the best barrells I’ve ever gotten on a longboard, pigdogging.  Clean exit on a chest high wave. Incredible visual until my Hair covered my eyes near the end. Another Surfer was hooting at the top of his lungs after I made it out, later said only 1’ of nose was visible and thought no way number one was this spot actually thowing a barrell, or that I could ever make it.  But it did, and I did.

 I have nothing I can complain about with the way this board rode today.

Now I can’t say it was all the  thicker fin.  I’ve 13 more years longboarding experience, the peaky swell and sandbar were coming together, and the ocean was throwing me some much needed Love, but my dismal expectations of how this board would ride, were not met.  

I am going to keep riding it, and raise the imaginary price.

 So glad i could not sell for what I was asking in 2003.

All future fin builds, are going to be thicker.

 

 

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    I can.

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Perhaps so.  Another very fun session this morning on it.  No complaints on how it rode.  I was impressed to be able to straighten out in time on a few runners.  Being more buoyant the board is harder to hold onto after straightening out than my thinner pintail longboards.

This board has no  accommodations for a leash.