Above was actually taken after the mold building had progressed, but it shows the backside of the parting flanges I made. A plug is made so that it has no negative draft, hopefully. This would allow a one piece mold, which is easier to build and maintain. But if negative draft is unavoidable, or the plug it too large, or the part has a lot of complex corners and edges....you will build a mold that is really several molds that bolt together to form one master mold.

Such was the case here. I decided where the parting lines would be and ran a dam of plasticine clay along the backside of each line. On the side where the mold was to be built, I placed playing cards against the plug surface, and pressed them into the clay dam. Then I applied metalic furnace tape to the mold side of the playing cards. This creates a flange, and when you build the removable part of the mold, you also build the flange. It is later drilled thru so it can be bolted to the rest of the mold.

Note: The parting flange was actually installed after waxing, and before spraying the PVA. Then when spraying the PVA, the plug and the flange get sprayed. You can use any number of things to create a parting flange, but I like this method because it is easy to construct, and can follow contours easily.

Just before spraying the gelcoat, the rest of the plug is masked off. This is to prevent spraying gelcoat on it, and allows you to work only on the removable parts of the multi-part mold.



Above was actually taken after several layers of the mold were laid up. But it shows some of the masking. I use typical painters' paper and masking tape, you just have to be sure it sticks. So the next step was to spray the gelcoat. A tooling gelcoat gives the mold a hard smooth surface from which to build new parts. It is thick and dense so you can sand or buff it if necessary when building new parts. A color like orange is often used because it helps highlight air bubbles during the layup or new parts. But it can be grey, or black, whatever.

The gelcoat is pretty finiky stuff. It needs to be sprayed on in three wet passes to a thickness of 20 mils, and allowed to cure to a no thumbprint or thumb drag state. Then a second coat is applied, just like the first. There are many things that can screw up a gelcoat. I like to keep the layup area @ 65 degrees, and monitor part temps with an infrared temp gun.

As soon as the second coat of gelcoat cures, the layup can begin. The base of the flange is usually a pretty sharp angle, so it gets a fillet of resin thickened with cabosil and milled glass. Then a "skin" layer of 1 oz. mat is applied to everything. This layer is allowed to cure past peak heat an cool a bit. Then a second coat of 2 oz mat is applied. Between layers you lightly sand edges to remove needles of glass, and the surface of the layup itself to remove any unseen stickups. Anything that sticks up will create an air bubble in the next layer, and you want to achieve a solid layup for your mold.



For a mold I usually apply a 1 ounce skin, followed by two layers of 2 oz, and then a layer of coremat and 2 oz, another layer of coremat and 2 oz, and then a layer of woven tooling cloth. A mold needs to be thick enough to prevent warping and distortion. Some production shops will tell you you can apply 5 layers in a day, but I like to apply two at the most. Polyester resin generates heat as it cures. Too much heat causes shrinkage and warping, and can cause problems with the gelcoat. The resin I use has no wax added, so the outside never cures untill you air deprive it. This means you can take your time and add a couple of layers a day, and when finally thick enough, I spray PVA onto the backside of the mold, causing the final cure.

The pic with the sprayguns shows the coremat. It is a thin, cardboardpaper-like material with microspheres in it, and is used as a bulker to thicken layups. The manner I apply it is to leave an edge around the coremat, for the fiberglass layer above to bond around it. This creates a composite sandwich layup, similar to what we used in composite aircraft building, and imparts great strength and rigidity to the mold.



Above shows the center console taken thru these stages, with the first layer of coremat going on. Coremat also spreads the load of the eggcrate structure which is added to the backside of the mold. Eggcrating is simply wood or steel bars that create bracing and also create a stand for the mold.

David Breeze

[This message has been edited by opm2000 (edited 03-07-2007).]

Above shows the parting flange dam being removed. The removable apart of the mold and it's flange have been built thick enough to go ahead and remove the dam.



Next, the edges of the newly created flange are squared up and the PVA layer is removed. The PVA was now a thin film which easily removed from the orange flange.



So now we have to build the rest of the mold. The new parting flange will recieve three coats of wax, and then it and the rest of the plug will be sprayed with PVA, gelcoat, and then followed by the layup schedule. After the last layups are done, it's best to exercise restraint and wait 3 to 5 days for the mold to set. Then you can part the mold from the plug, and begin to make new parts!

BTW, this is a dash plug I'm working on for Blackram's convertable :>



David Breeze

[This message has been edited by opm2000 (edited 03-07-2007).]

[This message has been edited by blackrams (edited 04-27-2007).]

One thing to consider, Ron, in the "worth the effort" equation is if you make the interior box of the glove compartment removable from the OUTSIDE, you can easily pull it and get to things like the mounting points, wiring to the back of the radio/HVAC controls, relay module, etc., without having to stand on your head and look up under the dash without being able to get any light on the subject.

You're old, like me, and not nearly as limber as you used to be. You're also getting bigger around, like me, and let's face it, we just don't fit places we used to.

John Stricker

Edited to add..................Not everyone is built like David. I think he has tapeworms or something.

quote Originally posted by blackrams: I'm assuming you consider that a good thing. In that my Pantero version will be a roadster with a raked windshield, I think the Lambo version works. It's all a matter of taste, some will like neither version. You can't please everyone but we feel that these two versions work for the car. I'm trying to decide if installion of a "glove compartment" in the Lambo dash is worth the effort. I know the utility of such a install would be very useful but I'm not sure it's worth the effort. As these projects move from one phase to another, lots of ideas come up. But every idea effects something else and slows the whole process down. Dave is the craftsman with the knowledge in this project, I'm more of the "stand by and hold this" helper but this is and has been one hell of a project. I'm thankful for the opportunity to work with Dave on this.

[This message has been edited by jstricker (edited 04-27-2007).]

quote Originally posted by jstricker: You're old, like me, and not nearly as limber as you used to be. You're also getting bigger around, like me, and let's face it, we just don't fit places we used to. John Stricker Edited to add..................Not everyone is built like David. I think he has tapeworms or something.

John,
The paragraph's that are not quoted are worthy of consideration. The part that is quoted is simply not true, I'm young, limber and skinny, just ask my....I can't afford to have anyone lie for me. ;(
OH crap, never mind. You're right but I'm still cute.

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Ron
Land of the Free because of the Brave. Most gave some, some gave all. Some ran the other way.

quote Originally posted by jscott1: I haven't poked my head in this thread in a long time so forgive me if I speak out of turn, but I don't understand why someone would go through all the trouble to do a custom dash and stick with the stock gauges? To me, it instanly looks retro 80s and not as nice as a custom autometer or dakota digital, or a later model cluster like the firebird or grand am. That's just my unsolicited opinion, you can easily disregard, but if its the wiring the scares you off I can help you with that.

Your opinion is appreciated, I can't speak for Dave, speaking for myself, alternative gauges are a very real possibility, and that may end up where we go. My thoughts are that not everyone wants alternative gauges, with this dash, there are several possibilities. It's easy to put a different dash guage panel in for a different look, this set up allows us to go several directions. I'm personally leaning toward a digital dash with HUD but that is somewhere down the road. Who knows where this will end up. You have to start somewhere. Thanks for the input.

Now I have to start that diet so that Stricker will shut up.




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Ron
Land of the Free because of the Brave. Most gave some, some gave all. Some ran the other way.

[This message has been edited by blackrams (edited 04-28-2007).]