hoods

[tubbs]

what is the proper or best way to cast hoods.... for a beginner.

[Excrewchief]

Clay up the bottom apx 3/8" high. Make sure all the edges are very clean and sharp put it on cardboard. Alot of times I will put two drops of super glue on the clay before you put it down on cardboard so that it can not float.
Than build a wall around 1/4" or more larger than clay I use legos greg uses clear acrylic. So it looks like a fish tank. Then I assume you don't have a vac chamber or a pressure pot. Use the slowest curing silicone you can get . The reason I say slow it gives you more time to get air bubbles out . Also I glue the legos down with white school glue . It peels off later but holds it all down. Then set a weight on top and let it dry. When ready mix the silicone ( stir very slow ) so you dont cause lots of air bubbles. Hold it high in the air and poor very slow you want a thin stream ( less air )
Pour until it is apx a 1/2 " over the top of hood. And let it cure. When dry peel cardboard off bottom . Then stack another row of legos on what should be the bottom. Slowly dig the clay out and do a good job around edges dont take the part out or knock it loose. I will hold the part in when the clay is out and take an air hose holding tight and blow all the tiny pieces of clay out . Then prefer spray in mold release here everyone does different I spray several light coats on it greg sprays a very heavy coat. I do light coats because heavy ones will show up in the parts. Sometimes not always.he likes some is good more is better. My self I spent to many years doing custom paint jobs were there is no room for error. And I love to tease him about it because he does such nice work. And I don't know how sometimes . (Right greg )
Man I like to bug him he takes it so well. Anyway I forgot to mention after you poor the silicone you can use Dremel tool or small bench grinder something like that and hold it to the side of the mold. As the mold vibrates you will see air bubbles come to the top. That is a good thing the more air that comes out the less stays in the mold. If they get up against the part it will always be there and show up in your parts.
Now go look around the forum and greg has posted lots of photos that you can see were parts are clayed up and in the mold box and I think he has posted some the he put silicon in part way and photographs to see what the heck im talking about. Then ask more questions. Good luck have fun and remember it may take a couple time the first time you do it to get it right also you tube has some good vidios. Alumalite and smooth on both I like the alumalite one they are put very simple.

[Mastercaster]

Yes, Rocky does give me grief sometimes. Yes, I do pretty good work for the most part. He is describing spraying mold release when prepping the mold for the silicone to be poured in for the other side. I do spray in plenty. I also carefully remove the mold release overspray from the masters part surface with cotton balls and Q-tips. This is a important step on parts with fine detail. The rough looking areas on the underside of a hood is important. It is supposed to look like insulation. Seat and carpet detail is important on interior parts. Silicone is sensitive and it sees everything. It can even pick up a fingerprint!
A vacuum chamber and pump are helpful here too with fine detail parts. Once your parts are clayed up, you can pour a thin film of silicone over dash parts, wheels, grilles, etc.in your mold box. Set your mold box in the chamber and cycle it. It will pull bubbles out in detail where otherwise the silicone might be trapping air. It will tighten up the silicone. I am amazed where silicone will go and yet won't go in detail. Vacuuming will help. Purchase some silicone oil and thin it a bit to help too. There is a lot to know and learn.

[tubbs]

wow!! aaaahhh, I either say thanks or what have I just gotten myself into??? lots of stuff to learn is right. ok another question, you both talked about clay, what type, brand? anything special?

[superstock]

al..go to you tube..type in...resin casting part 1    by thumbresin..there is a part 2a also...superstock

[Excrewchief]

Jun 14, 2017 10:37:23 GMT -7 tubbs said:

wow!! aaaahhh, I either say thanks or what have I just gotten myself into??? lots of stuff to learn is right. ok another question, you both talked about clay, what type, brand? anything special?

I get mine from alumilite. Hobby lobby sell there clay and you can use 40%off cupon.

[Mastercaster]

I purchased mine from Alumilite also. If you are planning to mail order it, this might be the best price online. Their clay might be repackaged KLEAN KLAY.

[tubbs]

thanks fellas.

on a side note - hey Rocky, still working on those engines. have not been to a few meetings due to bowling season. well let you know when I get them.

[Excrewchief]

Jun 15, 2017 4:59:08 GMT -7 tubbs said:

thanks fellas.

on a side note - hey Rocky, still working on those engines. have not been to a few meetings due to bowling season. well let you know when I get them.

That's ok I have more than enough to do . I have not packed up your stuff send me a pm letting me know when yhe next meeting you are going to attended. Thanks

[grozny]

You can get that white sign board for cheap. Very cheap. Make the base a bit bigger than your master. After it's clayed up make high walls and seal it up good with a hot glue gun, again cheap. After you have cast the first half and removed the clay, you can clean it all up and use a dull knife to work the edges loose around where the base had been. Then just slide the half of the mold upwards so you can flip it over and pour in from the "bottom". You will need to reseal the edges. You can later throw away this signboard box or re-use it. The glue is pretty easy to cut. it's faster to work with then legos, and you don't have to clean silicone from dozens of legos later, you can throw it away.

[tubbs]

thanks....

[gothic]

I use fiberglass, pam, one to one glass resin, spray the hood I wanna do, then mix, slather lay glass on one side, using a brush I tap till I'm nut'z forming to the hood, one layer will work, when just about cured, spray otherside, even the fiberglass, mix, slather, and tap yer but off, I wait about 48 hours, then pop'em apart, pop the hood out, whaaaala, hood mold, oh yeah don't forget to leave some edge around the hood, mix the resin, pour into one side till just about full, then rubber band it all together, or book it, I let it sit about 24 hours, oh yeah use pam, before ya pour the resin, after 24, pop it all apart, waala, yer hood is ready sir....

[Excrewchief]

Sounds like a lot of work .
I did fiberglass for years. And never went to that much work . We always used past wax then gel coat big stuff we used a chopper gun mix it somewhat hot hour later done. Little stuff like you are doing does have to be by hand . But the molds will last forever

[gothic]

I haven't try'd this yet but Bondo has Bondo glass, fiber glass mixed with resin, mixed with Bondo, ?, as for using fiber glass, to make the mold, we at the shop use'd to use it to make molds for ground efx kits, now they do speaker boxes and what not, hell even door panels and dashes, seems like allot of work for just a hood, but it's not, considering ya can use the fiber mold? lol, for what like, almost a life time, or intel ya snap it, lol, but yeah, now thinking about it, all for just "A hood" it kinda is, I'm an L88, and stinger hood nut, and I have just got done doin a double L88 hood for the '68 Elco, I will post pic's in this stage, next day or 2, but yeah for just one hood,

[Excrewchief]

Yep it's not the Bondo. As you know it . There has been many brand's out there its better known as resin jelly its fiberglass mat chopped up real fine with resin mixed in so it kinda is Bondo.. for fiberglass. Work very well. Have used It for years remember to use mat not cloth . Cloth has no strength mat is the strong stuff then you lay the cloth over that so you can roll or brush the air out and it lays down nice with no fibers sticking up to slice your hands on..

[gothic]

Jun 24, 2017 20:02:36 GMT -7 Excrewchief said:

Yep it's not the Bondo. As you know it . There has been many brand's out there its better known as resin jelly its fiberglass cloth chopped up real fine with resin mixed in so it kinda is Bondo.. for fiberglass. Work very well. Have used It for years

Is there a name brand, "Bondo" can I find at, say, the parts store, checkers, or just hop over to my wally world??? thanks...

[Excrewchief]

It's all about the same now . I really don't remember brand names I know I saw it at auto zone not very long ago . I remember when it came out it was used to mount corevette bodies . You used it as a panel adhesive the first time I used it was to hang a corvette body.we started using it for boat repair I have used it for many things . If you are going to use it to make a mold use about three coats of carnauba wax first. It is also best to put a piece of tube somewhere in the master fiberglass shrinks when it kicks if you have a Tube you can apply air with a hose and nozzle to separate the part from mold because it does not flex . With the mold on outside most of the time they get very tight. Even works good to remove parts from master. Do a couple holes and make sure no negative edges or it will never come out. If you have a west marine by you it may be alot cheeper. Just dont forget nothing flex's that is why there are so many parts to a corvette body. If you get into mass production they make a flex agent and that will blow your mind how much flex you get we could take a racecar fender and twist it into a knot. If you can belive that. Very pricy don't remember cost we bought everything in 55 gal drums and resin was apx 1000.00 a drum . I have not used that type of stuff for about 5 years now. And when I stop I try my best to erase from the brain.I have thought about making some mold in fiberglass but they have to be perfict but will last forever.I have had molds 10 to 15 years and still good. And if you chip or crack..it you can fix it. Have fun..

[tubbs]

holy crap! all this from 1 question. I guess there IS many ways to skin a cat... or cast a hood!! thanks all.

[Excrewchief]

If you can handle it there is more . Just for you

[gothic]

Jul 12, 2017 4:38:46 GMT -7 tubbs said:

holy crap! all this from 1 question. I guess there IS many ways to skin a cat... or cast a hood!! thanks all.

[Excrewchief]

Jul 12, 2017 20:58:53 GMT -7 gothic said:

Jul 12, 2017 4:38:46 GMT -7 tubbs said:

holy crap! all this from 1 question. I guess there IS many ways to skin a cat... or cast a hood!! thanks all.

I always wanted to learn how to use resin. They say it's fun ?

[gothic]

Loads of fun, hehehehehehehe

[Mastercaster]

Hood molds are pretty easy. The "claying up" process is where your attention to the detail is important, for any part large and small.  Go look at my thread about the Judson dual supercharged engine.  That is the way I clay up parts.  A hood is just a bigger part.  Rocky makes molds a bit different than I do and that is good that you can see variations on how to complete the same task.  My goal, once a mold is made, is to have really thin flash around the part that I am making.  It is important to put weight on top of your mold once your resin mix is poured in and the mold is closed and in the pressure pot and air pressure applied.  For any given mold, 5 to 10 milliliters of mixed resin is all that is needed to make most sets of parts.  It is also important to realize the physical size of your mold once completed.  Will it fit in my pressure pot?  Here is another important point to consider.  If you are using pressure pots like I do, the bottom of the pot will actually push out so the bottom won't be flat anymore.  It is a little scary at first.  You might want to build a metal cage to shove it in and then apply the pressure.  If you have kids and a significant other this might be a good idea.  I suggest that you put something solid and round in the bottom of your pot so that the surface will be flat when you slip your mold in.  If your mold is large and is making many parts the flash around the parts in the middle of the mold might be a bit thicker.  These are details you will need to experience and observe from your own experiences.


I should relate a incident that I had with a large pressure pot that I bought from a Ebay auction back when I first started casting.  A big pressure canner that I converted to hold body molds.  I had a decent air compressor with a regulator that would occasionally stick open for some reason.  So I converted it to a pressure pot.  The first time I put air in it, it over pressurized and the lid blew off.  THAT WAS SCARY!  It bent the bottom out a bit and ruined the lid gasket.  I really thought that hundred bucks was gone!  I got a different regulator and gasket and it worked good after that.  You can buy adjustable pop of valves too just so you know  It might make your kids and significant other feel safer if your hobby workspace is in your home.  For a good while when I first started casting my stuff was covering a 9 foot long island counter in our kitchen.  Yes, My wife was not a happy camper.  She finally gave me a spare bedroom that was crammed full of her hoarded crap.  It actually helped her organize her stuff and let go of useless stuff.  I have to admit we both have hoarding tendencies. I have my own boxes of stuff and I am not good at organizing either.

[tubbs]

ahhh, I don't think I will go as far as getting pressure pots, you convinced me of that!! I am just looking on making a few parts for myself. heck, I haven't touched anything in months so we will see. thanks for all the great info.