ONE layer of carbon inside a G-10 layup is plenty for too much stiffness.
For regular glass, mostly 3, one centered, one each on 10th and 30th of 40 layer layup.
I think it’s easier to just use airex core shaped to finish, then lam two carbon each side, then one regular glass. That way, you only foil the airex, which is easy, and finish the glass.
Lexan is clear like glass. It is not very stiff, unless it is loaded with glass fibers. It also melts pretty easily, so you need to keep the RPMs low when you grind/sand it. Its all about the heat buildup.
There are not really any useful plastics that are stiff enough without glass reinforcement - if you make a fin of the same thickness as a glass fin, it will be too mushy. If you make it thicker, you can get the stiffness you want.
The better commercial plastic fins have a substantial fraction of glass in them as a reinforcer for stiffness.
I’ve done carbon/epoxy layups and carbon/glass/epoxy. You make it essentially just like any other layup. The carbon will stiffen things a bit, and you can make thin fins.
If you want to use just a few layers of carbon, you can make them into the spine. The spine, however, contributes the least to fin stiffness. Distance from the center of the stack (for a single) is the all important parameter. If you wanted a really stiff carbon/epoxy fin with minimal carbon, it would be worthwhile making a stack about 0.040" thinner than the desired finish out of epoxy/glass. Then, foil it. Then, epoxy two layers of 6 ounce carbon on the outside, finish foiling, hotcoat it, finish the fin tab. The fin can be any color you like as long as you like black, you won’t foil much carbon, and you’ll make good use of the additional stiffness. And the carbon foiling steps would take almost no time at all.
There are so many ways of approaching fin construction it boggles the mind.
Consider these general comments –
When we separate strong sheer walls from each other they work independently to give the final product added stiffness. They can be separated with all kinds of materials – wood, high density foam, Lexan, or laminations of any less stiff material. Plywood with external polymer is not a bad approach, ask Bert.
The call on progressively more stiff laminations is just a Blakestah has it. Carbon/epoxy is the stiffest, glass/epoxy is next, and then polyester. I don’t know where G10 falls into the picture with carbon/glass/epoxy laminations however. I think plywood may fall on either side of polyester when it comes to stiffness depending on the type of timber it’s laminated from. Some exotic tropical plywood laminations used for marine applications are very stiff. If your using solid wood stock teak is pretty stiff, Some deciduous trees like oak are very stiff, while alder is very nice to work with and is fairly porous. Conifers tend to be very resilient and somewhat pourous and seem a very good choice for fin work to me. Some spruces and port orford have some wonderful qualities and would make a very nice fins if you could get the stuff. I’ll bet Paul Jensen could even make some of his own ply if he was of a mind to. I’d love to have some 6 ply 3/8" of the either one. It’d make super longboard fins. Balsa is very porous and flexible and needs some wall support to work in fins.
Generally with wood if you want much stiffness you going to get density along with it, while with polymers you can vary stiffness without increasing density as much is it happens in wood that’s why we use them. Some plastics work very nicely. Some are a pain. G-10 and Lexan (polycarbonate) are exactly that. Other plastics don’t bond well so they wont fit into the picture at all.
Wood, high density foam, polyester, epoxy, fiberglass and carbon fiber are the materials that I’ve found to be the best ones. There may be something else but I have yet to come across it.
When you boil it all down putting the structure in the right place at the right stages of construction is what will make the fin foil perform the way you want it to.
The fin/fins that will light up a board in triple overhead surf are going to be much different than the ones that work in knee wakers so the composites used will need to change accordingly.
Here’s Young’s Modulus that will shed some more light on the picture.
http://www-materials.eng.cam.ac.uk/mpsite/
interactive_charts/stiffness-density/NS6Chart.html
Off to the fin shop, Rich
#4 Low Density Poly Ethelyne - if you can keep the base thick in a bow with set screws, and not to deep, carves almost like butter, cheap, and flex - in the right dimensions - good stuff, “cutting board” material. Also, just made a fin for FCS boxs out of solid oak, sealed w/epoxy. Worked great.
anyone else used different materials for fins ??
I just feel there’s much more to be said , and tried , when it comes to fins…
cheers !
ben
In reference to carbon fibers in the body.
As a composites tech, fixing our helicopter I have had a few experiences with carbon splinters in my forearm…
Your body attacks the crap out of it and forms a 'BB" like mass of scar tissue around it then works damndest to push it to the surface… a scalpel speeds up the process. this pretty much happens every where in your body, and if you got it in your lungs… good luck. There is an old fibreglasser up here who actually had his lungs scrubbed with a salt water mix due to fibreglass in his lungs. A product of Manliness in the 50’s. Took him about a year to recover from the operation…
okay… thin foam core, carbonfibre , then ‘normal’ [silane] cloth on the outside of that…
would that be stronger / easier to sand than the foam, silane, then carbon outside layer setup ?
thanks !
“chip”
ZoSurf,
Thanks for the “heads up”–much appreciated. Your comments are in line with some other stories that I have heard regarding carbon fibers.
mtb
Hey Ben, I would put the glass on the outer surface.
The strength of any layup is helped by not sanding the fibres, and the integrity of the carbon is more important. The glass outer layer will give you a small buffer zone when you sand it.
Of course if you foil your foam perfectly, do your layup accurately, and sand it carefully, you won’t have any problem. (Isn’t that what we all try to do? Yeah right)
thanks Greg for that !
I figure if I do a very thin foam core and do what you just mentioned, leave foam out of the tabs, making them glass and carbon , it will be interesting to [hopefully feel the difference…and end up with a nice[r] looking fin to boot.
Would I be better off glassing the two layers of cloth at the same time ? And, with epoxy, rather than polyester resin ? …how much does carbon fibre soak up resin , compared to 'normal ’ silane cloth , I wonder ?
thanks !
ben
Bert Burger, I’d like to hear what you have to say on composite fin layup techniques, and your results, please ??
[I’m sure YOU’VE done plenty of experimenting in this field, yes ?
and Greg Loehr, too…do you make carbon fibre / epoxy lam fins for any of your epoxy boards ? ]
…thanks guys !
I’d use epoxy, but it’s up to you. Carbon will soak resin relative to it’s weight, just like glass, and it’s better friends with epoxy than poly. I do find I can get carbon flatter.
You’ll probably get better answers from others.
dam it !!! i didnt even notice this thread , i just posted on virtually the exact same subject on halcyons fin flex thread …
then i noticed this one and the subject matter i posted on the other thread would fit right onto this one …
hey i might see if can cut and paste …
hey chip!!!hows that …
this is just a summary of some recent stuff , theres way more from years past , maybe later …
in the last 6 months ive gone through another one of those intensive periods where i end up trying heaps of different stuff only to confirm what i already knew , but can at least have a deeper appreciation of why and how to add to the intuative feelings i already had …
ive been through a series of fins from thick flexible ones , thick stiff ones , thinner (not blakestah thin) flexier ones and thin rigid ones …
using as a sandwich or filler , core cell , 80 d cell , 60 d cell , 4.5mm ply and 9mm ply …
fabrics were standard e glass 2, 4, and 6 , 200 gram twill weave carbon , hessian , and lastly cotton , couldnt tell you the weight …
plus tried 2 different epoxies , one with a longer pot life , slightly lower hdt, and a lower barcol hardness which gave it a slightly rubberyer feel , 2 polyesters , standard lam res and a gp resin , also tried tooling 2 part liquid urethane …
regardless of flex , , one common denominator was the fins ability to spring back if it did bend , all the floppier softer fins just didnt cut it in , fast sectiony waves that required quick spontaneous manouvers …
the stiffer fins respond way quicker as no energy is lost while the material loads up ,
in certain soft waves the floppier fins still worked fine as long as you had plenty of time to line sections up , and held nice clean arcs that didnt change to quickly in intensity or tightness …
all the stiffer fins gave instant response time (blakestah will like this) even the thin stiff fins responded instantly , but just wasnt as smoothe and fast out the end of the turn , and tended to stagger or make me do my fast drawn turns in stages washing off a touch of speed with each stage …
so many variables to mention , and give details of each combo …
but in a nutshell the light stiff well foiled fins were the winner …
none of the foam filled fins could really handle serious direction changes without some lag , except some carbon/eps combos which i got super stiff …
so many other possibilities as well , because of the board/fin combos …
it comes down to energy transfer …
energy transfers quickest through something that is stiff with a low density …
i started thinking that the weight of the solids had something to do with them feeling slightly spongier or not quite as responsive , but now im convinced that energy wont transfer through the higher density fins quick enough …
your fins are really at the extreme end of your reach , as far as your ability to feel whats happening far away , almost like an extension of your body …
if you were blind and had a long stiff cane im sure you would be able to define more detail at the end of the cane , then if you had a soft rubbery one…
ive always believed that a board should get proportionately stiffer the further away it gets from you , i think that same philosiphy applies to fins as well as an extension of the board , that every part of the board should get stiffer the further away it gets from your center of gravity/mass to give you the most far reaching sensitive feeling of whats going on around you …
dolphins ride the wave in the power zone , if the power of a wave is deeper down , then it stands to reason we can harness some of that with fins that transfer that energy back to us in a more efficient way …
reaching in past the turbulent boundry zone to the clean green water …
i really think tom would agree with the lighter stiffer fin giving more sensitivity as opposed to the heavier stiffer fin …
but i will make that point again that if you have 2 fins with the same stiffness , but one is heavier than the other , the lighter one will respond quicker , not because of lightness or weight but because energy can transfer quicker through a lower density …
also even if 2 fins seem to have the same weight and stiffness , depending on how the molecules are linked , will determine how direct the energy can travel …
the lower the hdt the quicker a polymer based material will reptate …
those thermo softening style polymers and resins with lower heat distortion temperatures dont seem to feel as lively , even tho they feel similar in your hands when trying to bend them …
if making a standard lay up fin it would make sense to put a layer of carbon in the middle , that way as the fin is foiled , even tho the tip gets thinner it also gets proportionatly stiffer in comparison to the rest of the fin , and when doing side fins , putting the carbon on the flat side …
right now im loving my timber carbon combos …
regards
BERT
Ben
Check my post from a little way back “vacuume forming fins and adjustable fin boxs”
These were balsa sandwich ive been riding them for about six months now and would not go back to solids
They are so light you would not belive
And best of all you can make a set in under two hours!!
Mike
thanks Mike !
Yes, I DID see that thread… and read it with interest at the time.
Bert, thanks for sharing, you blinded me with science a little bit there, but I think I followed the stiffer lighter density stuff though. Being I am just a ‘simple Ben’, I would LOVE to see some photos of your “various materialed fins” you mentioned, please ? [ I think I am one of those people who learns more by seeing and trying… ]
I realise you are very busy , but if you did find a bit of time, I’d LOVE to check out some of those fins you mentioned. Thanks mate …you and Halcyon’s stuff I always find very interesting. And Blakestah’s comments too…
I’m sure there are plenty of good fin makers and experimenters out there [?Greg Loehr ? George Greenough , do you view here still ?] …I hope this thread brings them out to play, and " show and tell " about their experiments, and feedback.
Thanks for adding to this thread , Bert…I look forward to seeing and hearing more . [I recommended to Rich to do the composite fin thing here at swaylocks, as I feel people here would be interested to share their findings, so thanks Halcyon, for letting me put this here]
ben
where to start ??
this is what i have left after team guys and regulars poach the stuff with potential …anything i think could be a worthwhile possibility after ive tried them , gets passed on to other better surfers in different conditions and board set ups …
the , i will get back to these later draws and template box , the potential for further development draw , and the im prepared to let these ones get poached shelf …
and heres some of the raw materials still hanging around from the most recent foray into different variations …
as usual most of my favourites are not within easy reach , as long as i have 2 or 3 good sets that work real well it doesnt bother me what the team guys have …
usually at comps any good stuff gets passed around between us, so its still in the family when i really might need something …
it sometimes gets awkward when 2 guys are wanting the same set of fins or board fin combo and they end up progressing to the same heat , we get the funniest reasons why the pecking order should be in a certain order …
fin foils and templates are one thing to explore , but then you change the materials , layups , different composite combos , and it all changes again …
fins you wrote off as a bad design or foil suddenly start to work or have an increased range ,in different material combos …
keep the status quo??? LOL ha ha ha (evil genius laugh). joke!! i think meeting miki has rubbed off on me …hey miki how about the aps foil 3000 , then i wont have to toil behind a jigsaw and grinder …yes one day a factory of mindless robots building whatever my imagination conjurs…
regards
BERT
“HOLY SNAPPING A$$EHOLES BERTMAN”
I wish I had the time and patience to create some of those…
You must be self actuated, Maslow was right…
I bow in your presence…
Hicksy
ooh yeah Bert !!
THIS is why I come here !!
great stuff …now if you just had the spare time I have, you could sit at the computer all day for a few months describing in detail how you made EACH of those fins.
But I totally realise that you have a life !
…keep the shots coming though, if you like !!
Me ?
So far, apart from the shots on the ‘fin photos’ thread I just rescued from the archives,
the materials I have used so far are : -
foam core/ polyester resin/and 6oz cloth fins
wood/ 5oz cloth / polyester resin
solid 5oz [flatweave] panels
tinted 6oz panels [polyester resin]
pigmented 5oz flatweave polyester resin panels
ones I’d like to try…
volan panel layup
5oz/carbon/epoxy
foam/carbon/ silane/ epoxy
foam/wood/carbon / epoxy
wood/ silane/epoxy resin
? wood / carbon fibre / silane / epoxy ?
Can someone please tell me the difference between carbon fibre and graphite [ / ?‘carbon graphite’?] cloth…if indeed that is what it is called ?
Thanks !
ben
Can someone please tell me the difference between carbon fibre and graphite [ / ?'carbon graphite'?] cloth...if indeed that is what it is called ?
Same shiiite.
The graphite cloth I used was assymetric - with 10 times as many fibers funning one direction as the other. I laid it up with the fibers running from base to tip. I think its easier to just stick to generic weave cloths. Doing a good layup (ie: good with the squeegee and roller) and foiling it well are more important than the choice of cloth for me.
I also want to give making curved side fins another go…
Not surprisingly, the wood core ones I made a few years ago snapped [luckily] at the fin’s tabs. The waves I caught on them…the feeling was really different, and fun ! It felt like I was ‘lifting’ out of the water, if that makes sense !
Depending how well cabon fibre curves, I’d like to have a go at making a solid glass curved panel with a layer [?or two?..what do people think ?] of carbon in there. Who has done this ?
…Lokbox / Jim ? …how did / do ‘Rainbow’ lay up their re-release of those curved side fins again , please ? [Or, is that ‘classified’ ? If so, I understand…that’s fair enough ! ]
cheers !
ben
Hey Bert and Blakestah,
What are you guys using to cut out you Carbon/glass/epoxy panels? It looks like I’m gonna have to get myself an industrial band saw pretty soon. Any suggestions will be welcome.
Mahalo, Rich