Vacu-forming mold

[T.S.Davis]

I know I've read posts about vacu-forming and I've found sites on how to do it and what not. My question is, what material do you use to make the mold/plug? Foam? Plaster? Gouda?

Terry

[Doug Forrester]

Terry
Personally, I've had great results with Brie and then hardened with CA.

Seriously though ..... I've always used wood for my vacuum-forming plugs. Depending how many parts you want to pull, soft wood such as balsa is very quick to carve and sand but won't stand up to a lot of production. Pine is better but is a lot more work to shape.

[T.S.Davis]

Thanks doug,

Brie, gouda, CA. All good on crackers.

I suppose if I carved from balsa a form that I thought was great I could seal it with a layer of cloth and some epoxy. Do you have a procedure to ensure your pieces are symetrical or do you eyeball it? For a hatch I'm sure you could eyeball it but if you were to trying to design a hull wouldn't symetry be critical.

Terry

[RCBoatingNewbie]

As I'm gong to give vacuforming a go, I was planning on using some balsa as a base, seal it, cure it, make a female mold, then pour a solid plaster mold that would be the final mold. I'm thinking the plaster would render a MUCH smoother finish in the end product (and last forever, too!). I've noticed w/ wood (I can't say what type, but it looks to be pine from the grain impressions inside the hull) that the grain tends to transpose onto the inside surface, and this gives a VERY slight texture to the outside surface.

As for the surface of the plaster, I'm thinking either a) some high temp paint, or b) maybe a resin layer, to seal the porous plaster.

Alternately, I could pour a resin cast into the female mold- in the end, I don't want a wooden mold / surface! :) That's just the way I want it to be... LOL

I'll also be adding some "suction lines" to inside corners (on the mold) and such, whereby, a sharp narrow groove has a few tubes leading to a cavity under the mold. This should make inside corners more square and pull down more sharply. I think there's an art to this aspect...

The wife and I where talking about this yesterday- at least for my own sake, I can form hulls quickly and easily (once the mold is done, the rest is cake). If the designs and quality turn out well, I may sell some hulls...

At the least, I'll be learning something new.

Paul

About the symmetry, I'll probably start the design on the PC, and print out cross-sectional templates that I can cut and glue onto something stronger to ensure uniformity. If I build a mold "free hand", I'll probably use a gauge like carpenters use for base / crown molding.

[RCBoatingNewbie]

Question, what sort of ovens are being or will be used to heat the ABS? I'm in need of a larger oven.... was thinking about looking into home brewed kiln construction, doing something similar to that.

[key]

I've seen som 15 years ago an artikel on making scale huls 3 to 6 feet long the used 500w halogeen lamps to heat the plastic.

[AndyKunz]

ABS is extremely temperature sensitive compare to HIS. There are only a few degrees between poorly-formed part and alligator skin.

If you are making small things (cowlings, hatches, etc), skip the vacuum and go pressure.

Make your plug (mold) out of whatever - balsa, pine, etc. Stuff it into a 1L-3L bottle, depending on what size fits best. Jam it in with extra bits and pieces of wood (make sure they won't cut through the plastic). Heat it up with a heat gun like is used on model airplanes. Voila.

Andy

[toyboy4145]

I work for a boat company and have made some vacumm form molds and run the ungodly large machine to make the parts. This is very interesting to say the least. Like Andy K. said if you are making hatches and such go with the easiest method. I have made a mold of a hull that I plan on pulling a part off of soon. I have some crystal clear .040 plastic that i will use. Theres just something very cool to me about a clear hull. I have used this plastic before at work and you can get corners that are sharp enough to feel the ridge on the edge. I will post pics when I get it done. Just a lot of other things to do right now.

The suction holes are critical to getting sharp corners and a true representation of the mold. I am sure that it is overkill, but at work we drill holes every 1/8" in corners and sharp edges. Do a search on the net, there is alot of information to be had about this subject.

[REBEL RACING]

That is a lot of good helpful information thank you smart guys.