Cheap and Cheerful Fins

So, being inspired by Sways and my bank balance I decided to make my own fins rather than buy some new ones. Wanted some proper keels for my fish so had decided to shape some out of ply then glass them. However, Seabase messed up my order and the supplies never turned up. So, having read a random post on Swaylocks about making fins I decided to give a real cheap option a try as an experiment.

Take one plastic chopping board (£2.50 from Woolworths with 4 kitchen knives and a pair of scissors!) like this:

Draw your fin outlines on with a permanent pen. I found a picture on the internet of the FCS wood keels that I would have bought, copied it into word and scaled it up to the correct size. Printed onto card and cut out, then used as a template.

As you can see, the chopping board isn’t that thick. About 5mm. I think it’ll be too thin and might flex a bit too much. But then again, I’m no expert on flex characteristics in fins so they might be perfect! The chopping board also has loads of dimples on it which will probably introduce loads of drag but I’ll worry about that later.

Next I chopped them out using my jigsaw.

I then clamped them together in a vice and sanded the outline so they were identical. I started with an electric sander but it blew up after a couple of mins so I resorted to sandpaper wrapped around a bit of foam.

Once the outlines were sorted I foiled the edges. I decided to foil both sides of each fin to give them more drive. The leading edge is thicker than the trailing edge but to be honest I didn’t put a huge amount of design thinking into it!

So there you have it!

Two new fins. Was really impressed how easy it was. Took me a couple of hours with a Sunday roast in between sessions! They’re in no way perfect, but luckily neither’s my surfing. I don’t imagine they’ll hinder me much and maybe they’ll improve the way my board rides.

My next thought was how to make the surface smooth. I could have sanded them but the plastic didn’t leave a particularly smooth surface. Looking round the shed I found a can of Hammerrite metal paint. So I’ve sprayed an off-cut with it and now I’m waiting to see how it turns out!

As you can see it looks pretty smooth so far! Probably end up looking like an old clapped out banger!

LePerit,

I love it. Hope they turn out. Any cabinet grade ply can be used to make fins. I pull scraps from my friends cabinet shop throw away bin. Mike

way to go LePerit!

this is classic Swaylocks!

let us know how they go

I hope the work well for you, but I have my doubts for the following reasons. Two tabs are not enough to hold a keel in, my experience is that it will place too great a stress on the plugs.

nad if its the type of chopping board I’m familiar with, the plastic is not rigid enough and will deform during hard turns with a loss of drive.

Again I hope they work, but if they dont, at least you got good experience foiling fins.

good on ya LePerit !

is the plastic quite hard ? [ie: would a grinder melt it?]

i ask , because i found the chopping board plastic pretty soft when the fcs grub screws are tightened

yes please let us know your thoughts , eh , on how they surfed ?

and how watertight / waterlogged ? they were after a few surfs

wonder if they can be glassed …

[hmmm… i think i feel a chippy choppyboard fin set attack coming on !]

cheers

ben

…I LOVE it when I see other’s fin experiments !!

very cheap. very cheerful. very cool.

That is out of the box thinking…

What is that stuff Polypropyleen? They may be a bix flex, you could sort that out with some fiberglass, if the resin will stick to the plastic. If the resin doesn’t stick to the plastic, that isn’t necessarily bad news… you could use the plastic as a plug for a mould and then cast fins in the mould…

early removeable fins 1964 were made of this cutting board stock.

yater I saw that Stu Fredricks brought north

fin inserted into glass resin amalgum

in routed slot in bottom of tail

mold resist alowed fin to remove

after cooling

that aside

the material is a refreshing return to

a roots plastic application

history …

new to who?

out of box thinking

pandora opened the box long ago

adapting environmentaly availiable

materials to solve problems…

appropriate and genius in action

too flexy?

lam two layers maybe three

to make stiffie keels

tack the fin to board with a drop of gorilla

easily cut with narrow kerf blade.

Le Perit

recieves an excellent for problem solving

inspired use of avaliable materials

and an excellent for simplified process

involving little or no complications

saw and block and paper

broken power tool dont stop no man.

…ambrose…

Just wanted to say thanks for all the comments. You can’t believe the stoke I’ve got from you guys replying to my little project!

Rooster - Cheers man. I work for a construction company and have three bits of ply “borrowed” from my various building sites in the back of my car. Due to lack of glassing materials they haven’t been started on yet. Plus the cost of the glassing materials (£35!) is almost as much as buying new ones. But without the fun of course.

ChrisP - Thanks. Reading Swaylocks everyday you can’t help but get inspired. You should have seen the look on my office collegues face as I came back from lunch with a chopping board and told them my plans for the weekend.

Burnsie - I agree on all three fronts! If they pull the plugs out my board it will be good repair practise. They may well be too flexible which will mean my incredibly rad manouvers will suffer… (as if I ever get “rad”)

Chipfish - Great to get a responce from the mighty chipper! The plastic is relatively soft. When I was doing the sharper turns of the template the jigsaw blade melted it. When I put them into my board and tightened the grub screws they did look like they’d cut in a bit. If they only last a few surfs I’ll have to blow another £2.50 on a new chopping board!

Oldy - You are my hero! The most inspiring post I’ve ever read. I cut and pasted all that post into word, printed it out in colour and it’s the basis for my board shaping project! Thanks for the comments bro.

Surfer Dave - Cheers for the thoughts

Ambrose - Many thanks for the nice comments. Was thinking of doing some two chopping board thick ones next! And broken power tools are the payback for buying them at junk yard sales!

Once again people, for a long time lurker like me, it’s really inspiring to get feedback!

looks like a good way to make runners for your next Bonzer!

So, an update on the cheap chopping board fins! Glorious sunny day in Northumbria, in the far north east of England, although the locals weren’t impressed at our arrival.

After fighting them off we found this little slice of North Sea heaven.

Now the fins were slightly too thin to fit comfortably in the FCS slots so I’d carefully fashioned some tabs out of special surf specific plastic at a cost of thousands. Oh no, hang on, it’s just the middle of an old frisbee cut up with some scissors…

As you can see they looked pretty sweet.

Ed looks on bemused:

So how did they ride? Well, they certainly weren’t any worse than my other real fins. There was definatly a bit more control, however, it might have been in my mind but I thought I could actually feel them flexing. It was pretty small weak surf and I’m not sure how they would have found stronger surf. Then after about 6 or 7 waves I swapped boards with Ed and on his first bottom turn, one of them snapped clean off! He swears it was because of his radical manouvers but I’m not convinced. Mark 2 will need to be beefed up in both thickness and strength of tabs.

Here’s Ed looking guilty for breaking my £2.50 fins. He gave me a fiver so in theory I’ve made money of the whole scenario!

The north sea must be full of broken homemade fins. I lost both of a pair of keels a few months ago. I didn’t realise till the next wave they’d gone! I was a bit dubious about their strength to start with.

The plastic might not be strong enough for keels, but it might be o.k for a small 2x3 trailing fin??. Much less force on a small trailing fin, and with the flexiness, it might stabilise, but not stiffen the board?. When we next update our board ( chopping ), i might do the same, thanks for the idea.

Did the same thing a while ago, with the same result. We used 8mm cutting board ( polyethylene ) easy to shape and didnt think it would flex, but each snapped instantly on 2 bottom turns.

Pass… but it was worth the experience, it’d work on fins with a smaller area but ours were about 9 square inches.

Good on ya tho !!

Great thread mate, pity they snapped…

This is what Sways is all about, trial and error…

The errors get weeded out and we’re left with the best…

Thanks for being the guinea pig…

Quote:

I hope the work well for you, but I have my doubts for the following reasons. Two tabs are not enough to hold a keel in, my experience is that it will place too great a stress on the plugs.

nad if its the type of chopping board I’m familiar with, the plastic is not rigid enough and will deform during hard turns with a loss of drive.

Again I hope they work, but if they dont, at least you got good experience foiling fins.

Yah, I believe the stuff is either high or ultra density polyethylene (HDPE/UDPE) Very tough stuff for cutting board duties, but not much elastic strength. Not sure about sheer strength. I’m also not sure that I’d try to make 'em smooth - that original dimpled surface might be near the ideal…

Samiam

ah, well, it’s the thought that counts. two thumbs up for trying, & documenting your experiment too!

Hey there

I’m really keen on the chopping board fins idea. You said the fins lasted a few waves before they broke off so i’m thinking glass-on may be a better option.

I’ve made a set of fins (7.5" X 4.5") and they lok suprisingly good. There’s a fair amount of flex but not as much “spring back” as normal fins so maybe a glass coat may help stiffen them up. Any thoughts?

Also, I believe that temperature plays a role: polypropylene or polyethylene (like many other thermo-plastics) get much more flexy as temperature increases but they also become more and more hard and brittle when it decreases. Maybe more fitted for tropical waters than Northern England?

It’s fair to say it’s a bit nippy in the North Sea up here. First surf with snow falling last weekend! I think they would have been fine if they were another 1/4 inch thicker.