Another question on mould flanges.

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#1

Hi everyone,

Sorry if this has already been answered, but I tried searching for it and read loads of posts on flanges but couldn’t find a definitive answer.

What is the best material to use for my flanges when the flange needs to sharply change direction by twisting 90 degrees? I need something that can be bent to this extent easily but is also strong enough to hold the weight of the gel coat. Iv tried plasticine however it keeps falling off the part when it is moved or collapsing under its own weight. Iv read that aluminium and certain woods are good to use however i think they wont be flexible enough.

And also i read somewhere that people fill the void between the flange and the part used for the mould, i was thinking, wouldn’t leaving this void be a good idea as when the part is finished it will give me an indication of where to sand back to?

Thanks

#2

you can make thin fiberglass sheets off glass. MDF can be carved and shaped.

#3

I usually lay my parts on a 1" slab of MDF board. I’ll adhere the part so its permanently on, then fill in all the gaps and voids with either bondo, clay, or dry wall joint compound. I like a mix. Joint compound as the main filler, let it sit over night, then bondo over that to shape it nicely.

If you are doing a very complex part that it will not make sence to use a flat base. I’d recommend aluminum flashing from home depot. You can buy it by the roll, or in pre cut shapes. The best way to adhere that to your part is by hot gluing it from behind the part, then using white glue or some sort of slow drying glue to fill the seam where gel coat can run into and sneak behind the part. You can also use clay or a similar material to mold the aluminum to the part.

If you are doing mostly flat shapes, I find foam poster boards with the glossy paper front and backs work pretty well. Be careful though, when you PVA the board, PVA it slowely. Too much will soften the material and destroy everything.

#4

Metal sheet stock is good. aluminum tape (for duct work, NOT DUCT TAPE) is also good for part-to-flang areas. All of them can be release coated easily (no priming/panting needed like bondo.)
You want to seal the areas between the part and the base always. if you have a gap, and you get resin in there, it can lock the part into the mold forever. You’d have to cut out the material that went into the gap. You can plan HOW you use the gap filler and maybe even add a score line into the area you want to cut down too. (imagine a solid metal plate mold, with a shape scored into it. When you finish your composite part on the mold, it will have that score shape into the finish.)

#5

I can’t upload pictures,but I have been making parts for years through trial and error.resolving solutions,regarding making flanges Make sheets on glass,using cheaper polyester resin chopped strand matt,depending on how flexible you need it to comply to shape.

#6

Hi guys,

I had a bash at making flanges using CSM however iv found that it is not flexible enough to flex around the part around the part properly. I will go out and get some aluminium flashing and give that a god a bit later.

#7

I cant seem to find any flashing suitable in the uk, iv ordered some sample of aluminium sheet however i dont know how long it will be until it gets here so iv started using milliput.

Does it matter what way the flanges lie? My part is sort of a U shape. Iv made my flanges vertical to follow the sides of the U in order to make the fabric fit easier. I was wondering if this is ok or should my flanges be horizontal. For example of made them like ‘u’ instead of -u-.

Thanks

#8

Can you fill in the harder areas with clay or putty?

#9

If you can’t find flashing chech with your local printers. Lithography uses aluminum plates. At one point we would give them to whoever wanted them but now with the price of aluminum you might have to ask them real nicely or offer them a beer or
Two :slight_smile:

#10

We use a composite panel made from aluminium skins and plastic core 3mm.
It is used in the sign industry you can bend it to shape and it stays bent. easy to cut, bend, grind and plane. Will have a look on the panel tomorrow to find the name.

#11

The name on the panel says Aluwedo but google only came up with distributors from china. It’s good stuff.

#12

Its hard to picture the shape you are trying to flange if its a sharp curve through 90 degrees or a longer one with a twist, a pic would really help.

Trying to think of easy to find materials

If you have a B&Q near you maybe go take a look at some Conti Board/Laminate edging strip you would need a couple layers to build up thickness, some have a adhesive backing which would make this an easy task. Or you might be able to use some strips of sheet wax in your shaped areas, perhaps 3mm (they do thinner and thicker) it will bend round most shapes at room temperature, then when in place reinforce it with some chop strand wetted out on the backside to make it all solid. Its easy to find craft shops, ebay, composite suppliers. You could hot glue a few tongue depressors or thin strips of ply to the back of the mould to lay the wax on and keep in place while you add the csm.