ericjon262

anyone have any tips for me on how to make one, i'm thinking about trying to make a few factory appearing replacement parts for my car.


Thanks-

Eric

radical82

Make sure the "plug" (piece you're pulling the mold off of) is as straight and true as possible!!!! The better the plug, the better the mold, the better the mold, the better the part!!!!

Use quality materials, gel coat, matt, resin, and cloth. Get hooked up with a good fiberglass supplier and take his advice on what to use and how to use it.

You'll also need rollers, mixing bowels, brushes, and other things... If this is your first time, try a google search on fiberglass mold making and do some reading and studying.

make the mold strong and reinforce it well so that the part will not move around and change it's dimensions as it cures out.

Selecting the correct finish for the plug and the correct mold release is important to the quality of the product and getting the most usage out of your molds.

Find an old geezer like me that lives in the frozen tundra and invite him to Pensacola this winter... Give him a place to stay and some food and he'll teach ya how!!!!

ericjon262

after seeing pics of your car I would gladdly do it if I had a place and food for ya, how about for a case of beer?

radical82

I don't do beer no more, but your other expense would be a continuous supply of coffee!!!!!

I've done a number of 'glass cars from Vet repairs to custom built glass bodies,,,, let me know if I can help you with some information and good luck with your project!!!!

Once I get finished with my hood, going to be building it in 'glass--actually core matt and kevlar--light and strong, best of both worlds!

Rolling Thunder

Well question is what is it your trying to do? I mean i know what your asking but heres the thing. First say you are looking into makeing fiberglass body panles for your car example. It wouldnt really make sence to make a mold seeing as how if you were only going to make one for one off pieces it would be easier to just make a one off piece without a mold and secondly fiberglass fenders are already offered for out cars and it would be cheaper and easier to just buy them. Not to mention they can do it better than we could hope to do in our garage because they just have better equipment and will end up with a better product (assuming materials used were of the same quality). So in other words we would need more details about your project to give better advice on it. Although i will say unless its a part that no longer exists or is a custom part that never existed then 99.99999% of the time its cheaper and better to just buy it already made. Not to mention if your going for light weight a lot of times even though fiberglass is stronger than steel by weight thats dosnt mean your part will be lighter than the steel one. Fiberglass also may not have the characteristics you want for whatever part your trying to build like for example it warps over time which might not make it the best choice for body panels or if it is you need to make sure you use a good resins that will shrink/warp less than the cheap stuff. Theres also saftey to concern yourself with. For example if you were going to make your own fiberglass hood i would do that differently than say a dash pad (which would influence the mold design). A dash pad would only need to be cosmetic and wouldn't need to be to strong and if it broke no big deal where as a hood i would construct probably with a steel skeleton wrapped in fiberglass or at least steel around like where the hinges and hood lach bolted up because if a hood breaks on the highway that could be a real bad thing for the person behind you. So befor i could really say what would be the best way to make a piece ide need to know what your making.

ericjon262

what I plan to make wouldn't have to much load on it, and would be braced accordingly, any bolt holes would have "groments" or a metal flange to add strength, don't worry, I don't put the time in to build things that won't last, hence the thread asking about the correct why to go about it!

Rolling Thunder

Well i completely understand what your saying and there's a lot of general tips and tricks to making fiberglass molds as well as books to read up on but depending on what your doing really will determine what kind of mold you'll want to make if one at all and out of what would the mold will be made of. Fortunately i had the benefit from learning from a man who worked at a Ferrari dealership making repairs as well as things like making the custom carbon fiber seats molded to fit the driver like a glove and weigh less than 3 lbs! From my experience what ive come away from with is the basic principals of what a mold is and how to make a mold are simple really but when given a certain task and having to figure out a way to accomplishing that task takes a bit of skill from an engineering stand point in a sence and a bit of creativity. Now back to the original question how to make a mold theres a few different types of molds and materials to make molds out of. What you use will depend on a variety of factors that again without knowing what your really doing its hard to suggest what i would think would be the most efficient way of going about it and how to do it. Further more if its a one off piece theres really no need for a mold because its easier to just make the piece one off. If this was something that you were going to reproduce and sell perhaps that would require a mold but even then the quality and type of mold is dependent on how many copies you intend to make. I understand if this is something your trying to keep quiet about till its done but are there any details you can revile beyond what you have already? Things like number of copies, basic shape (are we talking about a flat piece or a complicated one?), are you trying to copy a factory piece or just make a custom no mods needed bolt in part that will look to be factory, budget, really any information like that or anything else you can divulge. As again its hard to really make a suggestion without knowing what your really trying to accomplish.

ericjon262

I'm thinking about trying to make fiberglass 91-92 chin spoilers, because I don't want to spend 250 on another used beat up one, or 300+ for a re-pro, and I was thinking I might be able to make a mold, and start producing a chinspoiler, or sell the mold to someone who would be interested in produceing them. I was also thinking about trying to make functional cooling ducts for the brakes, If I could get a good re-pro going. I've been watching several you tube videos about making molds, and it looks about the way I envisioned.

any sugestions?

Thanks-

Eric

Rolling Thunder

Do you currently have a chin spoiler to work from?

ericjon262

Yes I do, I planned to use it as my "plug".

Rolling Thunder

That makes it a lot easier. First things first you need to get it preped. What I mean by this is first you need to make yours absolutely perfect. Not only does it need to be perfect but it also must be braced as its too flexable to be left "free standing." Once its perfect and braced so there is no room for any flexing it should be painted and a mold release agent applied to the spoiler (usually a wax but not your typical auto wax though it will work too for less important projects). Next what we have to do is look at what the mold will be made from. How many copies are to be made? If its going to be a limited production run ide use something like plaster. Its real easy to work with, cheap and fairly durable. Problem is its also not going to do many pieces. A more durable mold made from something like fiberglass for example is still not eternal but would be much better but also much more expensive. Once you've decided how many copies you want to make a material for the mold can be chosen and we can get into the more specifics of how to do it. What youll have to do is figure out where the different parting or flange lines will be. For example if you were to make a mold of a ball and you made it from one piece you would never get the ball out obviously so you would need a mold that was comprised of at least 2 pieces. Same thing with your chin spoiler. You need to make it so that youll be able to remove it from the mold. Being that i dont have a chin spoiler in front of me i cant say how many pieces the mold would need to be made from or where the parting lines should be but common sence prevails here. If the part is larger than the opening in the mold clearly that wont work. Something thats not quite so common sence is that even with mold release agents parts will tend to stick can be very difficult to remove from the mold and in a lot of unfortunet cases the part or the mold could be destroyed or permanently fused together even though the technically the mold could work in terms of the part could come out of the mold. This in many cases is the result of either poor prep of the mold or a just poorly designed mold itself. For example molding a 4 side of a cube. although the sides are strait up and could slide in and out of a mold tightly but without interference chances are after laying fiberglass into the mold you wont be able to get it out without breaking it or the mold just because there not enough of an angle to the sides of the mold to allow it to pop out. How you can make it easier is again with making more pieces in your mold. For example say we were just making a mold of the outside of the chin spoiler and the mold was comprised of 1 piece that did the whole front or a 3 piece set up one for each side and one for the front the 3 piece mold though more complicated to make would be easier to remove the part from the mold. We can get into how to create a parting or flange line when youve decided how many and where they will be needed. As you can see it is a fairly complicated procedure and theres a lot of expence involved. Seeing as how you need your chin spoiler in perfect shape to begin with unless you were intent on making additional copies and had people willing to buy them i don't think it would be worth it. Youll probably end up spending the same amount as the repro costs and tons on top of tons of time. Even at that rate theres no promise your first attempt will succeed. Being that this is your first experiment with fiberglass im assuming it pretty likely you will end up scrapping the first mold and try again. Its fun to work with fiberglass and a great skill to have but i think for your first project you should maybe to some smaller less aggressive experiments before trying to tackle something like this. If you wanted to just learn about working with fiberglass and making experimental molds i can give you pointers of things to try and materials to experiment with but i dont think you should start with a part like that. Its just a very expencive way to learn.

ericjon262

how long can a well made fiberglass mold last?

Rolling Thunder

Depends on a lot of factors really too many to guess. I mean a really well made machined steel mold could last virtually forever if the time is taken to prep it and maintain it. Seeing as how thats probably out of the question the best one that could be made is probably fiberglass. If the mold quality and design was really good and you took the time to prep it and maintain it it will probably be able to make more than you could sell. An actual figure would be nearly imposable to give as it really like a car depends on maintenance and the quality of the mold. I mean i could say a really good quality mold could make 50 but if not waxed and maintained well you may only get 10 out of it. Even then say a fiberglass mold could do up into the 100s the design and shape of your mold may only reliably work into the 20s. It really depends too widely on maintenance and design to guess. Although ide say a fiberglass mold should at least do 10 if designed right.

racing geek

iTrader: (5)

Would it be possible to use wood as a mold for a custom one-off part? I know wood is porous so even humidity would affect its shape slightly, but if it is only for a cosmetic part, I would think it would be fine right? I figured I would use a harder wood like oak, then sand it super smooth, put on a couple coats of paint, sand it super smooth, then apply gel coat/wax. Once all that is done I would be able to start producing the parts right? The part I have in mind is only going to have ~1ft^2 of surface area and only have one bend in it. I've been thinking of thermoforming but I don't think that would work right. I've also considered just making it out of sheet metal but I don't think it would be thick enough for it to look good.

Rolling Thunder

You absolutly could use wood for a mold. Actually thats how the original 60 vette prototypes were made out of wooden molds (theres actually a video of them laying the fiberglass in these molds while they were making the prototype 63 vette) and ive bet the later shark body style vettes as well. The reason why wood isnt commonly used is its kinda hard to work with. Its Not the worst thing to work from but its right up there on anything really beyond a flat piece you have to be able to sculpt the wood and that takes a bit of skill. Especially if your talking about making bends in it it can be done by steaming the wood and bending it over some kind of form but its a fairly long and time consuming process when useing other materials would be a lot easier. However it all depends on what your doing like i said if you were making a flat piece a flat board would be perfect. If you were going to do it though ide make once change to your method. Once you have the wood formed into the piece you wanted and painted (needs a nice heavy cote of paint dont want the resin sinking into your mold) once its all dried this would be the time you use the wax and other types of mold release if used. Then when your ready to make your part lay then down the gel cote and then lay the fiberglass on top of that while its still wet. Gel cote is used on molds but ive not on wood or atleast ive neve seen gel cote on a wood mold. In your case you would want the gel cote on the part your making not the mold itself. Without really knowing what your doing its hard to give advice beyond that but i think that answeres your question.

racing geek

iTrader: (5)

Honestly, I'm probably better at working with wood then I am with metal or any fiberglass. I have a ton of wood working tools at home so even making a wooden mold for a third gen fender wouldn't be hard.

When using fiberglass sheets/clothe whatever it's called, is it better to alternate the angle of the weave? If so, what kind of angle is best? 60*? Can you give an example of how strong different numbers of layers would be? Like one layer of fiberglass cloth is the same as stiff un-corrugated cardboard... two layers would be like a a thin sheet of steel... can you see what I'm trying to get at?

Thanks,
Mike

Rolling Thunder

Well to answer about the fiberglass cloth For best streing you want to lay the cloth at 45 degres to the weave for best strength. You may also want to consider useing a fiberglass mat (its the non woven one) its a bit stronger by weight than the woven stuff and is easier to work with especially around curves that cloth may not like to for around without wrinkling. Streingth is a hard thing to really compare to because it depends on a ton of factors. First and for most theres different weights of fiberglass. Kinda like how theres 24 gauge steel and 16 gauge steel theres different weights of fiberglass so it depends on which weight you use. It also depends on thickness and im not talking so much how many layers but if a piece is over saturated with resin it will be thicker than a piece that isnt. The quality of the work done a vacuum formed piece will end up stronger than its equivalent piece made by hand due to over and under saturating the fiberglass air pockets stuff of that nature. Just like a professionally done piece will tend to be stronger than an amateurs piece due to the same reasons. To give you a very rough idea and i mean rough if you were to get a piece of fiberglass thats commonly stocked at walmart 1 layer well done would be like something between a piece of heavy canvas to a piece of thin plastic like a cd case cover. 2 layers would be like a piece of 18 gauge steel. 3 is tough Ive stood on parts of well done fiberglass mat that were 3 layes thick. It can be flexed by hand but takes a bit of muscle. 4+ layers is kinda hard to describe as its just hard and dont really flex enough by hand to make it comperable to anything lol. One of the beautiful things about fiberglass is how much stronger it gets with layers. I believe somewhere i read as a general statement that its strength grows by a power of three for each layer!

racing geek

iTrader: (5)

What I will be designing will be something like this.... (ignore the periods. they are there to space things out.)

.......boltx2.......boltx2
-------|----------|--------------------------
.................................................................\
....................................................................\ <--- speed of car
.......................................................................\

I would think two layers would be enough because that lip hanging down is only going to be about 1" in height. The bolts closest to the bend will be about 4"-5" back and the other two bolts will be another 1"-2" back.

Rolling Thunder

Well I think i see what your proposing here. I would probably use more than 2 layers. Because although 2 layers is roughly reminiscent of 18 gauge steel its doesn't have the characteristics of 18 gauge steel. For example 18 gauge steel can bend fiberglass cracks and when your moveing 100 mph the forces start to really add up. You also have to concider the fact the what you have is going to work kinda like a lever.

.......boltx2.......boltx2
-------|----------|--------------------------
.................................................................\
....................................................................\ <--- speed of car
.......................................................................\
..........................^...........................................^
..........................|............................................|
......................Fulcrum.......................................Lever arm

As you can see not only do you have a fair amount of force acting on that part from aerodynamic drag but its acting like a lever and could potentially crack especially at that first bolt. Also fiberglass will have a tendency to warp unless your useing a really high quality (and expencive) resin. To compensate for these factors i would consider making it thicker or have at least have a steel skeleton thats wrapped in 2 layers of fiberglass. Kinda like how a convertible top is canvas over a steel skeleton. Or if weight is a big issue you could also do whats commonly done to increase strength while being light weight and thats to add a core of some type. For example the new z06 corvettes floor pans are made from balsa wood wrapped in carbon fiber. The idea is that a big part of strength is thickness however it dosnt have to be a solid piece of carbon fiber to get this thickness. The balsa wood is used as like a filler or core material to give the carbon fiber piece thickness. This thickness makes it much stronger and yet dosnt add much weight. Other examples of core materials use to give thickness to add strength are like the ever popular honey come shaped material or even just regular foam.

racing geek

iTrader: (5)

I'm in school for engineering so I understand what you mean about leverage and what not. I'll make a model of this tomorrow afternoon and see what kind of deflection I will really get. I'll test up to 200mph just for the fun of it.

The problem with the idea of using a core is that I would like the whole thing to be 1/8"-3/16" thick. That's why I'm thinking two layers of fiberglass would probably put me right where I want to be. I suppose a third layer wouldn't hurt.

Rolling Thunder

lol well no worries on that one 2 - 3 layers of fiberglass is only about 1/16 thick if done well and not over saturated with resin. So i would definitely use the woven fiberglass as its strongest by thickness and if you do a careful job with it and dont over saturate the resin you could probably get 5 layers in while remaining within the requirements.

racing geek

iTrader: (5)

I did the math and found that if it is 1/8&quot; thick, it would only deflect: 0.0023&quot; at 15mph 0.0086&quot; at 30mph 0.0347&quot; at 60mph 0.0779&quot; at 90mph 0.1456&quot; at 120mph 0.1574&quot; at 150mph I figured if it doesn't even deflect 1/4&quot; at 150mph, there isn't anything to worry about. After all, who will get their car over 150mph and still want what I'm making. haha Sorry, for some reason the text isn't going on separate lines...

Rolling Thunder

Yea fiberglass is pretty tough stuff. Still to get it up to that 1/8 thickness youll need more that 2 layers but with enough layers of fiberglass cloth done well you should have a piece that will withstand that.

my89

So I'm thinking of venturing into the world of custom made parts and am thinking of starting with a spoiler. I've reading many of the posts and have a general idea of the process, but was wondering if you experts had any book recommendations? I'd really appreciate a few good resources to check out over the next month before jumping in.

I plan to try and make a Z20 special appearence style spoiler in the manner similar to that described by jonNYIROC https://www.thirdgen.org/forums/auto...ml#post2244542

I assume there is no good way to make a rigid spoiler in a mold since it has to be closed on 3 sides?

Rolling Thunder

Well not true necessarily, even though your mold may be closed in on 3 sides what they do in this case is create a mold that is made of several pieces that can be disassembled to remove the part. Granted this adds a bit of complexity and would only use this method if i was going to make several of these parts not just a 1 off piece. There are a few books that I read that i thought were pretty good. One was an old book i do not remember but was simply the best for a beginner. I think it was simply titled Fiberglass and was published in like 1953. It covered simple DIY projects to get familiar different kinds of molds all the basics and "sandwich" methods in real simple easy to understand style. Even though its old the fundamentals really havnt changed. Others that i do remember are:

Competition car composites by Simon McBeath
Fiberglass and composite materials by D. Arid Forbes

MSRed91Camaro

iTrader: (2)

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