Compsand Community

[RCC]

Hi All,   

I thought it might be nice to have a discussion on the pros & cons of different fin box systems with respect to compsand construction.   Any relevant installation tips & tricks would be handy also.

FYI, there is an existing thread discussing the use of Fins Unlimited boxes here:
http://www.compsand.com/forum/composite_surfboard_discussion/fu_box_in_compsand-t562.0.html

~RCC

[RCC]

I'm still working on my first compsand, so I don't have any veteran experience to offer here. 

I see a lot of people using FCS with compsands, which I presume is because it is light, attaches to both skins, and is conducive to flex... but I'm just guessing.   Is it difficult to install FCS in such a way that it will be strong enough?

I like using Lokbox for "normal" surfboards because it allows a fair amount of forward-backward adjustment, it is relatively easy to make my own fins to fit into it, and it seems pretty sturdy.  However, I'm not sure how well they'd fit into a compsand design, considering that they have a bit larger footprint, which might reduce flex undesirably.

[dougirwin13]

Actually I think part of the attraction with FCS is that it doesn't have to attach top the top and bottom skins.  hence it doesn't tend to interfere with flex (bonding the deck and bottom skins to each other inhbits flex).

Reading between the lines I think FCS is the way to go once you know exactly where you want your fins set.  If you do not know yet then you are probably better served using an adjustable setup.

Just my 2c!

[Kit Sidwell]

I've tried a few different fin systems, and to be really honest, I havn't noticed any adverse affects on flex with any.... even the ones that tie to the top skin!
Not saying it doesn't have an affect, just that it's not glaringly obvious to me.
I've made really good and really bad boards with a variety  of systems

As long as you have them set in high density foam inserts they will be strong enough.

The reality is, that people I will be making boards for are most likely to have a prefered fin system already.
So it makes sense to build them in such a way that they will flex using any system....

Most professional board builders choose a system for any of many reasons, but i've never actually heard one mention that they chose it for it's flex allowing properties!

[paul cannon]

makes sense to me kit
im pretty open
though im not a fan of futures
im sampling probox and they seem good
fcs are easy but a pain for mutli finsetups
cant say about lokbox cuz i dont know the system

i like fcs because they are simple repair and dont damage the glass if they fail
i dont like glassed over systems at all to be honest for that reason

[Bernhardt]

Hi All,   

I thought it might be nice to have a discussion on the pros & cons of different fin box systems with respect to compsand construction.   Any relevant installation tips & tricks would be handy also.

FYI, there is an existing thread discussing the use of Fins Unlimited boxes here:
http://www.compsand.com/forum/composite_surfboard_discussion/fu_box_in_compsand-t562.0.html

~RCC

I like glass-ons cause they just stick to the bottom letting the frame flex and are stiffer but they take more work. FCS are fine as are pro-boxes which are simpler to install except on complex(concaved) bottoms.

In my opinion the best and strongest fin system for an light core EPS install is Tom's RedX fin system in my opinion. You go straight through the board so no thermo andf they get locked in solid. No cant movement but alot of forward and back movement which in reality is all you need.

Greg Griffin gets the same effect with FCS boxes by making his tabs a little smaller and his fins out of G-10 material for stiffness. What Greg has taught me is that 1/8" to 1/4"  forward and back movement is all you really need other wise something is seriously wrong with the overall design of the board cause fins don't make up for what going on with the rest of the design. But that's just one old timer's view on board design which I have adopted.

You have to look at the whole thing not just any one part.

[Benny]

... No cant movement but alot of forward and back movement which in reality is all you need...

Pardon the editing, Bernie, but that's the part of the quote that jumped out at me. 

I don't know enough about cant to set it just once.  And actually, on a longboard, I don't think I'd want to. 

I just got back from 4 days at San Onofre, surfing 4-5 times a day, through all tides, in waist to shoulder high beachbreak.  For the trip, I made a fin testing platform out of a 10' surftech, by adding 4 Proboxes in addition to the center longbox.  I'd made a 5-box longboard before, but that had my 'normal' noserider rocker & rails and I don't think I was getting everything out of the fins that I could with a different board.  Randy Rarick recently posted on Sways about modding one of his (signature) Surftechs for fin testing on a trip, and I pretty much tried to do the same thing he did.  I've found that cant angle is radically important to performance, at least in the longboard. 

All quad testing was done with the same 4 fins - 4.5" Hanalei paddles front, 4" Hanalei rakes rear.  Trailing edges of the fins are at 6" & 12", front toe is 3/16", rear is 1/8". 

With fronts at 8* and rears at 6*, the board would whoosh around in a deep gouging turn - on a dime - like a waterski, when back foot force was applied right over the fins (this is not my normal style of surfing, so it was quite a surprise to feel it).  It would also, a little surprisingly to me, noseride very well.  Lots of hold.  On the downside, it slowed in straight-line trim, like a thruster and didn't pump for speed at the center of the board very well either.  So basically good in the pocket, not so good in a high line or on the shoulder.

With fronts at 4* and rears at 0*, it was a totally different board.  Felt like a narrow, raked single fin going straight - very fast in trim and easy to steer from the middle of the board.  But also loosened up when I backed up to over the fins & rollercoastered easily.  But - no hold or stability for noseriding.  Get up past the center and it felt like there were no fins at all. 

So then I split the difference and went to 6* & 4*.  Predictably, it did a little of all of the above, but nothing very well.  If I was glassing on or using a fixed system, it would be tempting to hit these midpoints, but it would never be as good a board as it could be otherwise.  So the other option is to choose (compromise) with either the noserider/turning quad or the speed quad which obviously brings out one kind of good performance but limits the versatility.  Or put in ProBox 

I did also try it out as a thruster, generic-looking 4.5" rakes all around, center back edge at 5", fronts at 12".  As draggy as the high-angle quad, but without the noseriding.  No thanks, won't bother with that one again.  I also rode it a few times as a single fin, which was good on the mushier higher tides.   Rarick said his favorite setup was actually 8* fronts and 0* rears.  Unfortunately, I didn't remember that until I got home & re-read his posts so I didn't get a chance to test that. 

Sorry to ramble, but testing is always good.  And, on a longboard at least, cant angle is the most important adjustment.  If you can decide which type of performance you want, no need to adjust it.  But if you want to be able to tinker with it, put in Probox.

I have photos on the computer at home if you want any...

HTH

Ben

[Bernhardt]

Aloha Ben
I usually choose 6-8-10 degrees for my fronts
and usually 0-4 degrees for the rear quads usually 4

I go with 8 or 10(H2s) on the fronts in a thruster configuration long or short board with a spiral vee or concave engine less for a flatter bottom
or
6-8 on the fronts in a quad configuration

for a long board 2+1 I wouldn't go more than 6 on the fronts
I've tried 8 and 10 but I don't get the drive I get at 4-6
Again this depends on the longboard's tail rocker
if there's alot of rocker and it's pulled in alot too
I'd ride it in a high performance thruster or quad setup or a 2+1 in a cluster layout with big fronts and a 6-7 inch small rear pulled way back in the box.

In most of my 2+1 configs I like to use the curved CRVs or Robin's boomerangs on the sides and a wide variety in the center. Or a smaller set of standard sidebites and more drive off the center using the sides more as setup training wheels for the rear.
If the center is flexy or narrow then I'll put the drive up front with 4.5" or bigger sides
If the center has a lot of rake like a harbour big red or something similar then I'll drop the sides to 3.5" or less.
Instead of cant angle I'm more interested in the relation of base drive/tip release and waterflow between the sides and the center so all the three fins work in harmony. In other words what ever the fronts start the back's has got to finish or they will fight with one another.

It's real important to understand what the tail rocker is doing depending on where you stand and how it's orienting the fin to the face and while in trim. Outline is important too. Once you lock into your boards sweet spot and understand what happens when you do something from that position then it almost seems detrimental to do something that would somehow affect its location at least from a short board perspective. Some guys who walk the plank could say the same I guess once they figure out all the positions they need to be in depending on where you're at on a wave. I guess that while I enjoy watching Herbie wildly do his thing on a single fin. It may not be graceful but he's maximizing what he gets out of the whole board from the nose to that functional sideslip technique he has down pat.

The problem with having too many golf clubs or tennis rackets in your bag is you always get fooled in thinking that something will play better that what your using versus learning how to maximize what you have in the first place.

Usually not knowing what the surf will be like I pull up with 5 different type of boards in the car packing 20+ fins to choose from when in reality all I truly needed was the right board for where I surf in the first place and then learning to ride it to the best of it's ability in a widest variety of conditions. But I like tinkering too much and in the end I think it really hurts my surfing.

Again it's all personal taste.
What works for one won't for another..

[RCC]

Greg Griffin gets the same effect with FCS boxes by making his tabs a little smaller and his fins out of G-10 material for stiffness.

I have been able to do this with Lokbox and get even more adjustment - at least 1/4" in either direction (1/2" total).  The extra adjustment was nice for me, as I was doing a 5-fin layout similar to Griffin's, and all I had to reference was photos.  (By the way, I am really happy with the results... might never bother with a 3 fin layout again.)  I made the tabs out of s-glass and RR2000 epoxy and they've held up just fine so far, despite my less-than-perfect molding results.


Interesting stuff folks!

[Benny]

Dang, Bernie.  I cant believe what you're able to explain right off the top of your head.  I've almost never ridden anything but single fins.  My first board was a 6'1 Becker from about 1980 (got it in about 83-84 when thrusters hit big) and I liked the feeling & just stuck with it.  All sizes, really, 6 to 12 foot, in singles.  So all of this stuff is new to me.  I'd try one every now & then, and even spend a few months on something every now & then, but always went back to the simplicity, drive, and feedback of a single. 

But I think you're especially dead-on about how moving forward on a longboard creates changes in rocker line vs. fin angle and that's got a lot to do with the cant settings.  Toe-in on longboards (if you're basically pointing at the nose) is pretty slight, so the drag is more affected by trim angle than water hitting toed-in fins...  Ben

[mark venn]

Lokbox is all I have been using, No board damage if you hit something, rock solid, if a little complicated install (due to glassing over).
Less chance of leaks due to glass over.  Can't tell if more or less flexy than any other system, just don't tie any of them to the deck.
Mark

[paul cannon]

whats the depth of lokbox mark

[mark venn]

Hi Paul, not sure from memory, I will measure one and report back

[RCC]

Anyone have any thoughts about or experience with using this spray foam stuff to serve the purpose of HD foam inserts for fin boxes?

http://greatstuff.dow.com/greatstuff/diy/products/bgf.htm

I'm thinking along the lines of routing out a hole of the size desired for the insert, then holding the fin box in place and spraying the foam around it.  I've thought of a few different ways to accomplish this, but I have yet to try it.  I figure it if it works well, one could devise a pretty efficient means of installing fin boxes with a good tight fit.  I picked up a can of it to experiment with, but I figured I'd start by asking the experts. 

[Benny]

I've thought about that too, RCC. 

But what I really think is that we're doing it in the opposite order than we should.

We route a big hole, install HD foam, then route a small hole, and install the box.  The box & resin are trapped within the entire board, holding in all that heat & risking the board itself (integrity). 

Why not just install a bunch of loose boxes into squares or ovals of high-density foam, cut to the same depth as the box?  No exotherm - the bottom of the box would even be open to the air.  You're really just gluing foam onto a box, rather than the box into the foam.

Then, when its time to put those into a blank, you just route the hole you need for the whole box/foam assembly, and lay it in with a thin layer of epoxy.  Or better yet, Pu glue - no heat & great foam adhesion. 

For rail fins, you can trim the boxes' foams narrower on the rail side.  You could even pre-laminate the assemblies with glass or even your skin material (i.e. balsa). 

I've done this before with longboard center boxes into d-cell.  It works great.  I think I'm going to pre-build a bunch of proboxes with foam around them too, and then a masonite router guide.  Its easy stuff - no possible way your installation can fail.