Making a fin mould.

Has anyone attempted or made a mould for making fins to fit standard 8"-10" box. I have been thinking of building a single foiled keel mould. Taking two foiled fins left/right with standard box fitting that I will make and using these as plugs to make left/right moulds. I would then need to polish the to mould halfs with a release wax, then place a peice of glass between the two halfs and clamp in a vice with the box fitting up ready for the pour. Will it work?

What could I use to fill the mould on a pour?

I have been thinking of using white resin with chopped strand matt cut into 1/2" + 1/4" peices and mixed into the resin ready for the pour?

Would this project be doomed to failure from the start?

I just would like a quicker way to make keels I guess?

Thanks in advance, Gary.

ive been thinking about this kind of stuff too gazro… heres some muolding links ive come up with.

I’ve been thinking about a simple mold to lay up fins with to cut down on the amount of foiling / grinding as well as to make them consistently the same.

Instead of laying of large sheets of glass I’m thinking that you should be able to make to simple plaster type half molds of the fin you want and then start laying small pieces of glass cut in the basic shape of the outer foil and proceeding with increasingly larger pieces as you near the top of the half mold / middle of the fin.

You would be doing both half molds at the same timne and when you fill the mold you then put them together. After they cure you would have a rough pre foiled fin that would be easier to foil consistently.

Why do it like that?

Why not lay 8 layers of glass on each side, fill the

rest with chopped glass, smash the mold together, and fill with resin?

Keep intact layers of glass on the outside, for maximal stiffness.

Or, put a balloon inside the layers of glass. Pour resin in. Blow up the balloon to smash the glass against the mold. Use 8 ATM pressure. After curing, replace the balloon with really low density cabosil/glass, or just plug the hole.

Or, just make a mold that is 0.1 inches thinner than the fin. Mold something low density (like PU foam). Lam 4-5 layers of glass on each side. Grind for 3 minutes, glosscoat it, ready to go.

However, the major fin companies still make their production fins the old fashioned way. Layup a sheet. Cut out the template. Grind it. That suggests to me that this is probably the easiest way to go.

Yes most of the posters in the archives do it the old fashioed way also. Just seems kinda waste of timeish to build something that you are gonna grind away. Other then support for the inner layers there doesn’t seem to be a reason to lay up outer layers larger then they will be ground to.

Like the fin-shaped ballon / solid outer layer of glass idea tho.

Yeah, I’ve thought about molding too. Basically, start with a fin you like, use it for the master “plug” or male, and brush latex or polyurethane around it, then remove the male master. Trouble is… are… that you can’t pull out the master unless it is of tapering section; that you gotta have excellent mold release.

AND, what are ya gonna use to fill the female mold once you have it? What material would go in bubble free, and penetrate to all edges of the mold?

I don’t think, short of a production (read big $) injection molding setup, that any of us can do this consistently. The comment above that the major manufacturers of glass fins still do it the old way is telling us that we have to as well.

why not use butterfly moulds?

just on the fin mould issue; the young guy working for me is currently doing the surf science uni course in west oz.this week he is apparently doing fin lay ups in a mould produced by 2nd year students.he is year 1.we were talking about this just the other day and he said they were going to use 4 layers of 4oz in both half moulds as the outer skin,then filling the hollow area with q-cell then joining both sides.sounds reasonable at this stage .i think a weak link here could be when they join both halves the centre line would be q-cell only. maybe they could put a layer of mat as the joiner or not fill the mould fully with the interested myself to see the end result.

After grinding about a dozen fins, the grinding process takes me about 30 minutes, start to finish.

I can easily see that this process would take someone doing dozens per day less than 5 minutes a fin.

That’s the advantage the fin companies have - large volumes, and well set-up work-space.

The only reasons to do something different would be if you were looking for something not available in a glass fin. You might want a wider fin that is lighter (plywood core). Or a thinner fin that is stiffer (carbon-fiber spine and epoxy resin). Or if you just wanna play with the process.

But probably, and this is definitely my experience, doing it the way the major fin companies do it a few times until you get good at it, and going to other techniques from there, is a good start in making fins.

3 minutes per fin, by the pro foilers, longbox, longboard. One night at Fins Unlimited, I foiled 587 glass on thruster fins, it looked like the pile was only getting bigger, not smaller!

3 minutes per explains a lot. What kind a tolerance / consistency could a pro foiler keep at that speed from fin to fin?

Really good, the best in the biz’, original employees from the late 60’S and they’re soon to reach retirement age. The bummer is, no young guys are stepping up to the plate, dirty hard work, but pays good.

What about this as a mould filler - Polypropylene is shatter resistant I think!

I found it here[/url]

Fastcast Polyurethane Resin

An odourless two component polyurethane system which is deigned for thin sections, or castings up to 20mm thick that require very quick demould times and can be used unfilled. Does not contain hazardous solvents. Good thermal resistance. With low viscosity it produces excellent surface detail and finish. Does not shatter like polyester casts. Simulates polypropylene when fully cured.[/url]

Cheers Gaz

Couple of notes:

Neither polyester nor epoxy resin will adhere to polypropylene.

Herb Spitzer is very adept at moulding techniques. Maybe he’ll show up and share some of his knowledge, but he may be working on finishing out the “Crossfire” or just trying to hold his family together and trying to get a session in occasionally.

Mahalo, Rich