Well The Cavity Could be somthing as simple as plaster....easy to
drill Lots of holes....and is not so hard to pull masters from as
long as they do not have major undercuts..Plus it can handel heat...Tommrow Im going to buy a 50 lb bag of paster and vacume form somthing simple but this mean's I have to retool the boxes I allready have...or build a new one..


aerogel

aerogel,
You might want to try hydrastone or ultrastone. It works like plaster but, becomes many times harder, like granite! You can drill the vacuum holes with a normal drill, but it takes heat better. We use this at my job when we want to make a temporary vacuum mold. The cool part is that it cost almost the same!
Gary,
www.wallacewireworks.com

Gary the webpage you gave at the end..You make them?

If So Gulp.....that is unreal...I would go mad...Like a hatter Trying to do somthing like that....very kewl


aerogel

Thye make Something called hydracal....I think its kinda the same thing not for sure......



aerogel

aerogel,
Yes, I do make the wire models and sell them all over the U.S.
They do take some time but, I do like to make them! And yes ultracall is the same thing. Glad you like my web site!
Gary,
www.wallacewireworks.com

Hey Gel;

I have used Hydrocal extensively in another hobby and it is a LOT harder than Palster, and has more flexibilty on the mixing time, and will NEVER become water soluble again..

Kirby

I have to order Hydracal this is what sucks The shiping cost more then the product....I will try plaster first then If It works to Hydracal..or somthing like that.


I all so think I will need a higher end Vacume source then what Im Useing for Concave mold's......A Air compressor with a huge
tank and reverse the Input's.





aerogel

Im going to start of with a very simple mold like this one and work up from there
? is You guys think I should Put holes on the mold flat plane or only Were the part is?




aerogel

I have been experimenting with a hot box, what I did was use a cardboard box lined with alum. foil, a hole in one end to fit a heat gun and a thermometer to watch the temp, it works well enough that I am building a better box. My idea for a vacuum former is the vac table and a frame to hold the foam with a skirt all around it and a foam seal on the vac table, heating and vacuuming at the same time, it's nearly finished I will post some pictures if it works.

aerogel,
There will have to be a hole(s) of some kind in the cavity area to pull the softened foam down against the mold. As to how many holes, their placement, the necessary softness of the foam, the correct amount of vacuum needed to fully form the part is probably only going to be learned by experimentation. I still think that this process is going to be more an art than a science. As you go through this, try to design in simple checks. -ie- thermometer, timer, vacuum gage. Knowing the temperature and the amount of time neccessary to soften the foam is knowledge that can be used over and over. Same thing with a vacuum gage that reads either inches/water or inches/mercury. In the event that you do something right, you'll want to be able to repeat all the steps that led to success. Plus, you'll be able to tell the rest of us so we won't have to do all the hard work!

JT

With the cavity design your foam pieces will have the dimples on them.

Yes it will have Dimple's going to have to sand them off I guess
I just want to see if this process with pick up all the Detail...





aerogel

Just have to remember to put the dimples in non-detail areas. The amount of detail will depend on the type of foam used and getting the right temperature and vacuum pressure. Hope it is easier than it looks!

JT

If you want details, I think you may want to consider making both a male and female mold. First, make the male mold (plug) pull the foam over it. Take your time and carefully make all the detail marks you want on it (keep the foam on the plug during the whole operation). Once that is done, give it a light coat of paint, sand with 400 grit paper, paint lightly again, sand again, until you have a nice smooth surface. Then wax the foam carefully, and pour the female mold over top of it.

Now you can pull the foam over the plug, then press it into the female mold to give it the surface detail.

http://www.rcgroups.com/forums/showt...hreadid=70430h

Futher techniques for forming foam described through above link. I've Been doing this for a while now with great results I use color close cell foam sheets, the material is a bit flimsy for large and long fuselages, but works great for canopies and compact fuselage models.

Foam comes in a variety of densities and compositions if you can get some commercial "rubbery close-cell" type foam with a certain amount of stiffness, this works best for detail and rigidity. Some of this stuff is like Depron, which is more like beaded foam (not close-cell)that you find in electronic product boxes but with a bit of rubber added to it, models made from this particular category are ones like the Airhogs airplanes/helicopter shells, they don't have a lot of fine detail but close enough for an appealing model.

Mario I. Arguello
www.micro-flight.com