Unconventional molds

**Gorilla0178** · 03-25-2019, 11:17 AM

So I've used lots of things as molds. Example. Im rigging my boat with a electric fuel pump. Wanted a small box to cover it and just keep it safe. Found something perfect, so I used it as a mold.

**Gorilla0178** · 03-25-2019, 11:20 AM

Pump will be mounted to a vertical wall with the box over it. With cutouts for hoses.

**Instigator** · 03-25-2019, 12:10 PM

That’s bad asss!

I do the same thing.

Half the trick to working w/glass is getting the MEK to resin ratio right.

I build small, custom glass pts all the time.

Keep it up.

**Gorilla0178** · 03-25-2019, 12:19 PM

Oh, im sure you have.

**Gorilla0178** · 03-25-2019, 12:20 PM

What about the mek ratio?

**Instigator** · 03-25-2019, 01:30 PM

Up here in Ohio where temperature chgs constantly, that chgs how much catalyst you add.

I’ll use up to 3% if I’m working in bellow 70* weather but normally between 1% - 2%.

If you get it wrong, it either sets up before you’re ready or not at all.

Ive done both.Ruined a bunch of pts, resin and cloth.

Down there, you’ll be at 2% in spring/fall or for small pts and 1% - 1 1/2% in August.

Get you a graduated dispensing bottle if you don’t have one.
Makes it idiot proof.

BTW, I still get all my glass supplies from Fiberglass Supply Depot on US1 in Ft. Pierce.
Great people, product and cheap.

**XstreamVking** · 03-25-2019, 01:35 PM

I've just used the tupperware containers as is. The waterproof snap on/off lids are great. Battery switches and elec buss gangs etc. Mount the stuff thru the bottom of the box into a bulkhead and it's dry.

**Gorilla0178** · 03-25-2019, 03:09 PM

It was a lunchmeat container. But I've seen Tupperware used. And thinking about it, I could have easily used one. As far as ratio of hardner, 1% is standard when making bigger parts. 3% is usually max. For small stuff I don't even measure closely. I only needed 15 min with that part so I kicked it off hot.

**Gorilla0178** · 03-25-2019, 03:09 PM

I've put buckets of resin in the fridge before to extend gel time too.

**Tin Man 2** · 03-26-2019, 05:14 AM

I thought mixing to “hot” caused the part to be too brittle. A slow kick time can be speeded up by using heat lamps.

**Instigator** · 03-26-2019, 06:49 AM

Correct.

The excess heat it causes will also cause pre-release where the glass pulls away from the mold.

Ambient trmerature dictates required amount of MEK.

Originally Posted by Tin Man 2

I thought mixing to “hot” caused the part to be too brittle. A slow kick time can be speeded up by using heat lamps.

**GregAdams** · 03-26-2019, 10:06 AM

hey fellas, I know you know what you mean when you refer to catalyst as MEK, but that makes it rather confusing for any novices reading your posts, when MEK and MEKP are both commonly used in the composites industry and are readily available at most suppliers. If someone were to mix MEK into there polyester or vinylester resin they are going to have a bit of a mess to clean up

**LakeFever** · 03-26-2019, 10:30 AM

I know MEK as methyl ethyl ketone. We use it for some PVC/ABS work here and there

**Gorilla0178** · 03-26-2019, 10:43 AM

That's right. Mek is thinner/cleaner. Mekp is hardner. And by hot I just mean more than 1% not crazy hot.

**XstreamVking** · 03-26-2019, 11:49 AM

Rule of thumb.....2% is max for resin and 3% for gell. This can be increased by 1% in cold weather but the catalyst has to be used up in the hardening process or it remains in the laminate and can be a problem later. So, use it correctly. Blisters/yellowing of the gellcote is one problem, weakened blistered laminate is another.