Dorade Cowls and boxes.

Zach · Post by **Zach** » Thu May 08, 2008 8:23 pm

Hi guys,

Wondering if any of you all have a 3 or 4 inch diameter dorade cowl, and if you'd be so kind as to measure the diameter of the horn end. I haven't paid all that much attention to them to guesstimate how big to go.

I'm looking for something to play around with lost foam molding of fiberglass. Think it'd be a pretty cool, and useable something to make. styrofoam tube, and a styrofoam ball from a craft store and a little bit of shaping and we oughta be in business!

Thanks!

Zach

deckhand · Post by **deckhand** » Fri May 09, 2008 11:41 am

lost foam fiberglass? I've worked in lost foam metal casting using the ceramic shell method but I've never heard of it being used for fiberglass. Unless it just refers to making a part around a die and melting the die out with solvent of some type after its finished. hmm interesting.

As for the opening, check here

Zach · Post by **Zach** » Fri May 09, 2008 1:27 pm

Thanks Deckhand, thats perfect!

Yup, you got it. Use a foam that dissolves in acetone or other solvent. For polyester: wrap it up with a packing tape. Wax everything and glass around it. Let the glass cure, dissolve the foam and pull out the packing tape. Polyester resin does a number on dow board... shape shifting mold... Hehehe!

3m 77 and a few other headliner adhesives will stick the extruded polystyrene together without eating it.

Epoxy you can just glass right over a foam that it doesn't eat, and solvent does. (I like epoxy, but its to expensive for me to do much experimenting with!)

Ceasar Choppy · Post by **Ceasar Choppy** » Mon May 12, 2008 10:51 am

Zach wrote: Let the glass cure, dissolve the foam and pull out the packing tape. Polyester resin does a number on dow board... shape shifting mold... Hehehe!
...
Epoxy you can just glass right over a foam that it doesn't eat, and solvent does. (I like epoxy, but its to expensive for me to do much experimenting with!)

I suspect that Dow stuff is styrene which is reacting to the styrene of your poly resin.

Zach · Post by **Zach** » Fri May 30, 2008 12:45 am

Ceasar, You got it!

---

So, I'm back at it once again. I started pondering making flat sheets into tubes. (Still have the 12incher waiting in the wings!)

Anyone have preferred tools and methods to cut a nice concentric circle out of a foam core? At the moment I've smashed it, mashed it, made powder and dust... but have yet to emerge victorious in my battle. A hot wire on a built on the end of a drafting compass comes to mind... but theres gotta be an easier way.

Thanks.

Ceasar Choppy · Post by **Ceasar Choppy** » Fri May 30, 2008 7:56 am

My friend Dan Pfeiffer did something similar... he flattened the end of a pistol-type soldering gun. There's a picture of it here in the first picture:
http://dan.pfeiffer.net/10m/quarterbert ... ebuild.htm

Zach · Post by **Zach** » Wed Jun 04, 2008 9:21 pm

Cool beans!

Oughta have a rig built tomorrow that looks a bit like a jig saw.

Thought this was an interesting way to make a circle with a table saw... of all things! http://metalcast.boorman.us/circles.html

Zach · Post by **Zach** » Mon Jun 09, 2008 9:01 pm

Update:

Hooked a 5amp ceiling fan dimmer (rotary style) to a 110v outlet. From there plugged in a solid state 6v/12v battery charger. Wound a piece of stainless steel fishing leader around the alligator clips. It burns a bit hot so I grabbed a 110v to 24v/16v/18v ac transformer for door bells and will give that a try too.

Cuts EPS board like butter. Gotta build a bow or jig of some sort to hold the wire under tension, and orient it.

Next up... figuring how it cuts glue lines.