yes please would like to know how you make them and materials used

decrepit said...

Leo has asked how I make my timber carbon fins.
Anybody else interested?
I've just started another 2 so I can document the process here if you like?

As with a lot of things I do, there's a lot of farting about, there's probably a much easier way of achieving something similar.

mike noticed this after emailing , im about to start one tomorrow but not sure if my photo box can take anymore pics

Yes I'm interested to :-)

Show and tell, please sir's :-)

Got a bit more done today.

Roughed out the 24cm with the grinder.
Note the support under the fin to stop it bending and vibrating.



With the grinder I try to use continuous strokes from the base to the tip, starting at the leading edge in a series of bevels. I treat the trailing edge a bit different, centre the curved surface of the pad about 10mm in from edge, this helps produce the concave at the rear. I've taken it down to within .5mm of the centre gauge mark.
Not everybody will be happy using a grinder, for instance Pepe uses a belt sander with excellent results.
I prefer a flat sanding pad for shaping, but on timber it tends to clog. The pad in the pic seemed very clunky when I first used it, but as it wears out it self cleans, so I put up with it and doesn't feel so bad now.

Next comes hand sanding. I use 80grit paper on 2 pads for this, an ordinary flat piece of wood for most of the work and a firm foam pad for the trailing edge.




By running along the trailing edge, with the curved part of the pad, and the pressure about 10mm back, the concave is maintained.

I use a tyler's profile gauge to compare the timber to a printout of the foil I want.
EDIT. Press the gauge on to the fin, and the shape of the foil is impressed on it, the fin foil can then be compared with the print out. (does that help Keef?)



I have a line at 30deg (the fin rake angle) marked on the bench with horizontal lines across it. This lets me measure across the flow line.
At this stage I don't match the foil, there has to be an allowance for the carbon.

After shaping the foil on one side, the next step is the carbon.




On this fin I'm using 5 layers, 2 full length and 3 successively smaller. There's a mix of 50/50 woven cloth and unidirectional.

A mix isn't necessary, it could be one or the other, but if it's all uni the timber grain needs to be reinforced by running at least 2 layers at cross angles, about 10degrees should do.

Tomorrow I'll get some resin mixed and laminate the carbon on.

decrepit said...

Got a bit more done today.





By running along the trailing edge, with the curved part of the pad, and the pressure about 10mm back, the concave is maintained.

I use a tyler's profile gauge to compare the timber to a printout of the foil I want.

i was wondering how you got the foil so dam perfect, but still none the wiser

keef said...

decrepit said...





I use a tyler's profile gauge to compare the timber to a printout of the foil I want.

i was wondering how you got the foil so dam perfect, but still none the wiser

decrep i imagine you pull the strands out from the gauge and measure it end on end
do you have a program that measures the length to width and prints out the foil depth and width for the angle or rake

yoyo said...

Keef, Mike's been making boards for decades. He has the eye of a craftsman. He pretty much gets CNC level accuracy with hand sanding and comparing his profiles by gauge to printouts of the profile he wants.

yoyo i know exactly what your talking about i have a 26cm, showed it to the illawarra guy's , they couldn't believe how light, stiff, and how well it was made,
as you said yoyo he can stick a thread up and show how its done , but unless you have the EYE OF A CRAFTSMAN and the experience you wont get the same result

keef said...

decrep i imagine you pull the strands out from the gauge and measure it end on end
do you have a program that measures the length to width and prints out the foil depth and width for the angle or rake

Thanks keef, it's questions like this that help clarify where I'm not giving enough detail.
No, you just press the gauge down on the fin, the pins aren't very tight, it doesn't damage the fin. That gives you the shape of the fin to compare to the printout. Where it's too thick I sand a bit more off, at this stage it doesn't matter if I sand too much off, (although I try not to), I'll fix that with bog after the carbon goes on.

Once I have the foil shape I want, I use photo shop, (well "the Gimp" actually, but it does the same job), to adjust the chord to thickness ratio, and then the range of sizes I need for my fins.

For different rakes I just measure across the foil at the angle I want. The curves stay the same.

Laminated today, but first I'll go back to a shaping detail I missed yesterday.

When the fin's in the clamp, and I'm doing the rough work with the grinder, the area at the base in the clamp is untouched. DON'T leave it like this, the foil has to go the full length of the fin!
I didn't bother on an early fin and it de-laminated. By leaving the base thick a concave area is formed between the base and the main blade, when the carbon in this area is under tension, it's being pulled away from the timber.
Bender had a similar experience with his first wide boom mod, between the posts and the flat plate there was a very big concave, this pulled apart under load.

So, here's the start of the laminating process.





It's not meant to be an ad for west systems, I'm sure there are other resin systems just as good, it's just what I used today, I know it's a very good resin and it's available in Mandurah.

The funny looking contraption is my solution to getting an accurate mix with small quantities of 5:1 resin. It's a lever of 10:1 ratio so I can measure tenths of a gram.
In the left bottom corner is some very handy silicone foam sheet, above that is some soft mattress foam.
In the right hand bottom corner is squeegee and Keef's roller, (tried it first time today), and very important, GLOVES, don't play with epoxy without them, epoxy is one of those nasty chemicals that seem quite benign, but slowly creep up on you. After too much exposure you become sensitised, and then all hell breaks loose.

I weighed the carbon at 32grams, typically I use 1.5 times the amount of resin to wet it out, so I weighed 45g of resin and 9g hardener giving me a bit left over to bog one of hardie's fins.
Sorry I don't have any picks of the glassing process, my hands had too much resin on to touch a camera.

But I started by spreading resin over the fin with the squeegee, putting the full length woven carbon over that, then using the roller to smooth it out and draw the resin up into it. spread more resin over that, and repeated process until all 5 layers where on both fins.

Moved them close together trailing edges not quite touching, placed the silicone rubber sheet over them, then the mattress foam, then a flat board and a lot of weight.





This should squash the carbon down, forcing out excess resin and any air bubbles.

The same effect can be achieved with a vacuum bag, but for small jobs like this I find it easier to just plonk on the anvil.

In the foreground is a bottle of vinegar, I use this for cleaning squeegee, roller and gloves. It doesn't act like a thinner, seems to break down the epoxy so it can be removed with a cloth. Doesn't work as well with brushes, it's hard to wipe every bristle!
For that you need a thinner, acetone is no good for epoxy, but the thinner for epoxy paints works great, (not sure how safe it is, smells like you wouldn't want to inhale too much).

If I can get to the fins before the resin goes too hard, I'll cut the excess carbon off with a sharp knife. If not it'll be a hack saw job, we'll see.

Love the extra bits of weight.

Kind of makes my 30 kilo bag of cement redundant

No Anita, almost falls off, no release agent needed.

Keef reminds me to point out, the blank must be straight and square with no twist before the process is started!

Got skunked today, so came home and got a bit more done.

Roughed out the other side, same way as before, except this time I used some heavy foam on the screw side of the clamp, to protect the fin.

Marked about 5 to 10mm in from the edges with marking gauge.




Then removed the timber inside the marks with a chisel and sandpaper








Next I have to figure out where the screws go and remove the timber there. Then I'll fill with a micro fibre bog. This protects the timber from any water entry and gives a bit of wear tolerance.

hey mike i wish you put this thread up earlyer , i brought a profile gauge today 250mm and measured my fins they look a bit sick

decrepit said...

There's not a lot a bit of bog can't fix!
The fin I made you has loads, as you'll find when you wear it down a bit.


And that eppler foil isn't the only one that can work well.

mike i wont be using your fin at illawarra so it wont be getting hammered with a shallow bottom
im doing wider based fins so 9 percent mite be a touch too fat
i must admit im having trouble working those foil graphs out you sent ,but the gauge is fantastic,
i set the gauge to the thickest part of the foil at the base and then ran the gauge down the leading edge , not sure if thats how its done but it looks good