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Kimba said..




Mould surface.

Only 2 fins out of the mould so far and they dropped out, only wax - no pva.

tim very great looking mould, ive seen your fins and very professional, I mite give up on posting how to doo's until I get something that looks as good as yours

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pepe47 said..

Hey Kimba, are you going to do a step by step on Whitelion windsurfing. Makes it easy to follow your mould making design. I like the idea of aluminium powder. And $80.00 sounds better than $1200!

Hi Pepe, I will put it on the blog at some stage as well as the fin layup. It will be a while though as I am doing up the backyard at the moment, feeling like an old man! I have a super quick mould as well which costs about $20 but is less durable. I will get some pictures and post that one first as there are only 2 main steps in the mould construction and you can finish it in an hour or so.

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keef said..

tim very great looking mould, ive seen your fins and very professional, I mite give up on posting how to doo's until I get something that looks as good as yours

Thanks keef! You should definately keep the how 2's coming, we can all learn things from each other. Everyone has their own spin on things...

I went down the same route as Pepe, it was going to cost $1000 to get my Tomahawk mould cut in aluminium and since I am trying a new moulding technique(for me) I wanted to be sure it would work so I made a proto mould. The Slingshot 23 was similar in plan and chord/thickness ratio once swept to 45 degrees so this was the basis for the proto. It needed to be extended and the steps in the foil would be at an angle to the flow(causing changes in the foil profile) but it was only ever going to be a test mould for proof of concept. The fins worked well with a "normal" layup and I got an hour PB on the 24 but I still have to get the proper resin for the new process and make a curing oven with ramping to suit.

I think my $1000 will be better spent on buying components for my cnc router which should hopefully eat ally as well as G10! Then I only have to buy materials...

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Kimba said..

quote]

The fins worked well with a "normal" layup and I got an hour PB on the 24 but I still have to get the proper resin for the new process and make a curing oven with ramping to suit.

I think my $1000 will be better spent on buying components for my cnc router which should hopefully eat ally as well as G10! Then I only have to buy materials...

, i got an email from one of the leading fin guys and he basically said G10 is too heavy for the larger fins and the way to go is molded carbon, the problem is setting up with high tech molds= slower proses and more quality control
you can call me a hoader but i save all my foam dust, bog dust, and glass filings, if you want a bullet proof resin for your molds, mix some fine pvc foam dust with some vinyl ester resin with 2% cat and some glass fillings or bog dust as well as your aluminum, what you will find is the foam dust is impregnated with the resin mix, the resin dust already has been cured so you get a second cure (compound) let the mix soak over night and degas you will notice the mix has already started to thicken and no air bubbles , now you can add your alloy powder and 2%cat, as you mentioned the alloy powder will sink to the bottom so the pvc mix is acting as reinforcement
don't take my word for it first do a test first, let it set for a day and try and sand or destroy it, i use that mix for my fin boxes and it can be extremely hard the drill the holes
i have some stainless powder so when i do another mold ill let you know how it goes
kimba i noticed theres no drain holes how do you control the excess resin

Hi Kimba,
Nice mold idea.
What's your alu/epoxy mix ratio?
Is the backing board MDF board?
Is the back board fitting a post cure operation?
Is it alu oxide powder that you use?
Like you I'm getting tired of the gelcoat/glass/epoxy process for molding.
They work great but very time consuming, have 6 of them now, getting sick of it.

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keef said..

Kimba said..



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The fins worked well with a "normal" layup and I got an hour PB on the 24 but I still have to get the proper resin for the new process and make a curing oven with ramping to suit.



I think my $1000 will be better spent on buying components for my cnc router which should hopefully eat ally as well as G10! Then I only have to buy materials...

, i got an email from one of the leading fin guys and he basically said G10 is too heavy for the larger fins and the way to go is molded carbon, the problem is setting up with high tech molds= slower proses and more quality control you can call me a hoader but i save all my foam dust, bog dust, and glass filings, if you want a bullet proof resin for your molds, mix some fine pvc foam dust with some vinyl ester resin with 2% cat and some glass fillings or bog dust as well as your aluminum, what you will find is the foam dust is impregnated with the resin mix, the resin dust already has been cured so you get a second cure (compound) let the mix soak over night and degas you will notice the mix has already started to thicken and no air bubbles , now you can add your alloy powder and 2%cat, as you mentioned the alloy powder will sink to the bottom so the pvc mix is acting as reinforcement don't take my word for it first do a test first, let it set for a day and try and sand or destroy it, i use that mix for my fin boxes and it can be extremely hard the drill the holes i have some stainless powder so when i do another mold ill let you know how it goes kimba i noticed theres no drain holes how do you control the excess resin

Sounds like I need a rack of potions keef, too complex for me - I like things simple...
I also only use epoxy as I dont like the Vinylester and Polyester shrinkage rates. The last big mould I made with woven rovings and left on the plug for days still had 1.5% shrinkage from memory!
I have a large vent at either end of the mould for when I start using vacuum infusion, there is also a spillway/intentional flash of 1mm to vent the leading and trailing edges and allow 4layers(.25 each) to extend past the finished edges. This way there is less air trapped in the region that you finetune by hand post moulding. I did try slate powder as the gelcoat for the weedies and it worked really well, the coating self levelled really well but will pool(in the bottom of the mould) if the ambient temp is too high.

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Te Hau said..
Hi Kimba,Nice mold idea.What's your alu/epoxy mix ratio?

Is the backing board MDF board?Is the back board fitting a post cure operation?

Is it alu oxide powder that you use?

Like you I'm getting tired of the gelcoat/glass/epoxy process for molding.

They work great but very time consuming, have 6 of them now, getting sick of it.

Hi Mike, its been a while!
Ratio:
I dont remember the ratio as I use a pump pack and teaspoon but warm honey would be about right. I vacuum degass and also pour in a fine stream to further degass and minimise air entrapment on the mould surface. Also pour from wide end of the mould to the narrow to avoid "weld lines" or multiple resin flows meeting.
Backing Board:
30mm chipboard benchtop from the new kitchen years ago. I imagine it is high moisture resistant but I seal the edges with the alu mix so there is no moisture induced movement. First side I poured in 1 step, the second side was done in several steps to keep the heat/shrinkage down. Each additional pour was done at the green stage of the previous layer. This method probably trapped a bit more air but i didn't want to run the heatgun over the surface, again to reduce overheating.
Aluminium powder:
I use 200 mesh aluminium powder at about $20/kg from my local mould & casting supplier.

I think I will try a mashup between the quick and super quick moulds and it should only cost about $40 but have the benefits of both systems. I also still like your tooling board moulds and will probably go that way when my CNC is finished. I hope to have a 1200x600x100 envelope to work in so that should cover most of the small scale stuff.

I'm in the process of doing a fin mod, it's an old, big (about 40cm) power box weedy of Elmo's, I'm cutting it down to a 21cm low aspect 45deg weedy.



I came across the joining piece for these 2 profile gauges, I was struggling a bit before, getting the long chord section right.

It's ready to be reboxed now, then some fllier paint and a final wet and dry.


EDIT, woops I had the gauges the wrong way up, you can't see the join. It's just a little plate with appropriate holes for the screws on the other side that hold everything together.

Must be fun constructing you own fins

They say that neccessity is the mother of invention, if you like shaping that's just a bonus.
I've had discussions with fin manufacturers asking if they can do a certain shape according to my requirements. The answers have ranged from "nah it's too hard" to "that's not what you need". I imagine most people who do their own fins have been through this and decided "##ck em" I'll do it myself! At least this way I'll get close to what I want. In the end one fin maker will pick up the design and run with it.
I'd like to exclude Boogie @C3 fins, who is approachable and is working on a prototype that is pretty close to what we're after. (also MXR with their wide base speedy)
I find that sanding a fin is relaxing and am now looking for a way to fit my stubbie through my dust mask. Bit of a problem that one!

easy use a straw