diabloadsit
New member
LOL, just remember cross hatch pattern. Plus, you will need couple of good coats of clear coat to protect the CF.
Carbon Fiber parts, interest?
- Thread starter 04fxt
- Start date
Spiller1327
New member
Sorry for the statements earlier but they are true. Some quick info for you 04fxt. Carbon fiber yellows under uv rays and the resin will crack. A good uv deterrent gel coat will give u a slight milky color but will completely stop the carbon from yellowing and cracking. Also it is best to use epoxy resin and to make a plug and a mold so that is is exact size and the a side(top side/good clean side) is on top. Both me and ray learned from some of the best composites workers in the state if not the whole east. I like the idea of cheaper Maine made carbon parts for Maine cars and I'm hoping u take my advice.
Nicklepage1010
New member
He meant instead of making a mold, you place the carbon fiber cloth on top of a hood/truck/ect, and then clearing over it, and taking it off and replacing the metal piece with the carbon piece you just made. Matt do a little more research on creating carbon fiber parts, youll be surprised of the complexity of it.
gakosaurusrex
New member
i feel like a cf lip wouldn't be a good idea. the seconded u bump something it done. the rubberized lips hold up better because there not brittle like cf
yea, i did that after the previous posts and agree its very complex, i wasnt aware how difficult it is......ive actually noticed my hood turning a little yellow, i want to get a s201 hood scoop and hope the hood isn't to far gone in color. 200 bucks for the scoop, maybe you can make one for cheaper???
Apollyon12
Active member
^ I could have told you that was going to happen...
If I created an object I wanted in carbon fiber could you make a mold of it and then make it out of carbon fiber? It's a piece I made custom for my boat with fiberglass over the original plastic piece but it started to fall apart after a few years of hard use... I'll try and get you pics of it...
boxer3main
<1.8 liter
a hood weighing a ton on a subaru...?
you guys gotta start eating some wheaties.
does your sube remind you of a 1974 plymouth wagon or what?
back to a reality for carbon...if you are trying to make money,
how about a part for many subes (37 years) could be differential related, cover protector...?
or heck, not knowing carbon fiber strength... maybe a diff cover r160, r180...?
or like on outback on the bottoms of doors.. some covers to mimick that as a generalization?
or center console stuff for amercian male sized hands...they are still midget even today.
edit: just thought of another multimillion piece... wagon tailgate handle. a legacy fits a loyale and legacy fits an outback/ forestor... as tricky as the differential in altering sales... yet they are ALL THE SAME.
Last edited by a moderator:
Spiller1327
New member
diff cover wouldn't work. Carbon is brittle.. Not good for protecting things just good for making things light weight. If you ever bought a hood out of carbon that is heavier than your oem one you got royally FUKKED. There is no way one of the lightest frp materials weights more that steel unless 3 times thicker or something.
Apollyon12
Active member
I really didn't want to get into this but it's getting to be too much.
First off, everything I am going to talk about is not the specificly designed race application parts. Short of that, stuff that was designed and built for a race team, almost everything out there for commercially available automotive applications are improperly designed and badly executed. There are exceptions, Seibon spends a ton of money making parts that work as designed, the price reflects that. Companies making nock-offs just take their design and steal it.
Properly designed carbon parts are NOT brittle. The carbon fibers themselves have an infinite strain to failure. This means that as long as you do not strain it past it's yield point it will never break, deform, or change it's properties. In plain english, if you put a steel bar under tension (pulling) and apply and release a force (that doesn't break it or cause it to pull into two pieces, yield) and cycle it thru this loading and unloading, it will eventually strech and break over a long period of time. Steel has a very low strain to failure rate but a high yield point, it's able to bend and contort without breaking. It can also carry a very high load without breaking initially but will eventually change shape. Carbon fiber is basicaly the opposite. As long as you only apply (or load and unload) a force that is less than what it takes to break it, it will strech and return to its orignial shape forever. But there is a problem with this.
The five fundamental forces are:
Tension
Torsion
Bending
Compression
Shear
While steel has good properties for all five forces, with bending probably being the weakest (fyi, concrete is great in compression but very bad in torsion, bending, and shear), carbon fiber is really only useful when it is under tension. Think of trying to bend a single carbon fiber, it won't support much load. So when any other force but tension is applied to a carbon fiber part, one that also includes resin, it is actually the resin that is carrying the load. Under compression, the carbon isn't doing anything, it's the resin. It's basicly the same for all the forces but tension.
So, back to being brittle. The example of a skid plate is actually a very good one. What is really needed is high shock resistance, we have a two ton car hitting an "immovable" object (a rock) at 35,60,90 mph. A metalic (steel or aluminum) plate is going to yield, bend and distort, but probably not break. It will probably keep you oil pan from getting a big old gouge or dent in it by getting torn up itself. It's a sacrifical item before any really important parts.
If we have that same impact hitting a carbon fiber plate, what is actually happening is that the resin is alowwing the structure (plate) to deform until the carbon fibers are placed under tension and are able to carry the loads (up to their breaking point). As long as the carbons yield strength has not been exceeded and the fibers have not been scratched or otherwise compromised, the structure maintains it's effectiveness and will work properly in the next impact. However the resin will be broken and cracked. If the yield strength is exceeded, the fibers will break and the structure is now useless.
The first problem is determining what kind of forces to design your structure, or plate, to withstand. The impact of a car hitting a bolder at 25mph is VERY different than 75mph. The plate for the 75mph crash will need to be signifigantly thicker than the 25mph. (I am not positive but I don't think that simply tripling the thickness would be sufficient). It may be that, for this example of a skid plate, the carbon will end up being heavier than an aluminum plate would need to be. Remember that if it isn't think enough it will be useless and your car will still get banged up.
The next problem is designing a structure that will not deform too much and end up transfering the load to your oil pan. The thicker, and heavier plate (than the aluminum) may be able to resist the impact but may bend too much.
Something that is brittle has a very low strain to failure rate, actually most resins are very brittle. They have a low tensile strength but are better in compression, they are also very rigid. This is why they are paired with something that is so good in tension but bad in compression, carbon. Most people think of carbon fiber being brittle because they have only ever seen the pieces that are for decoration, such as a pulley cover. They are very thin, have very few layers of carbon and probably have a very cheap resin. If you take a panel like that and bend it, of course it is going to crack the resin, but you probably won't be able to break the carbon fibers without some significant effort. That behavior is what carbon\resin composites are designed to do. A properly designed skid plate could withstand you taking a sledgehammer to it all day and you would probably only screw up the surface resin and the first layer of carbon. (fyi, if an individual fiber is damaged or compromised in any way, that fiber is no longer able to bear the same load, in the same way, as an undamaged fiber. This is why carbon is usually manufactured as a net shape and not machined)
Real world applications, a pulley cover is not load bearing and can be very thin, and needs to be in order to be light. A hood is also not load bearing and can be only a few layers of carbon, less than 1/16" and do it's job (which is covering the engine, nothing more). But all the hoods that I have seen are not made that way. They are the OEM shape, thickness and have the same structure on the underside that the metal ones need for support. Add in the fact that, most likely, the cheap ones are nothing more than one layer of carbon on top for looks and the rest is heavier fiberglass mat and I am not the least bit surprised that they are heavier than OEM. Real racing hood are probably exactly that, just a couple layers of carbon held on by hood pins. I have an old school fiberglass hood for my datson and while I haven't weighed both of them yet, I believe the glass one is going to be heavier. Same thing for my fenders.
Designing a carbon fiber part to meet all its needs is not cheap and if there is little or no design work done, the parts just aren't being made right. My opinion is that 99.9% of stuff out there is useless and a waste of money because of this fact.
It's late, I hope more coherent than most of Boxer3Main's posts.
First off, everything I am going to talk about is not the specificly designed race application parts. Short of that, stuff that was designed and built for a race team, almost everything out there for commercially available automotive applications are improperly designed and badly executed. There are exceptions, Seibon spends a ton of money making parts that work as designed, the price reflects that. Companies making nock-offs just take their design and steal it.
Properly designed carbon parts are NOT brittle. The carbon fibers themselves have an infinite strain to failure. This means that as long as you do not strain it past it's yield point it will never break, deform, or change it's properties. In plain english, if you put a steel bar under tension (pulling) and apply and release a force (that doesn't break it or cause it to pull into two pieces, yield) and cycle it thru this loading and unloading, it will eventually strech and break over a long period of time. Steel has a very low strain to failure rate but a high yield point, it's able to bend and contort without breaking. It can also carry a very high load without breaking initially but will eventually change shape. Carbon fiber is basicaly the opposite. As long as you only apply (or load and unload) a force that is less than what it takes to break it, it will strech and return to its orignial shape forever. But there is a problem with this.
The five fundamental forces are:
Tension
Torsion
Bending
Compression
Shear
While steel has good properties for all five forces, with bending probably being the weakest (fyi, concrete is great in compression but very bad in torsion, bending, and shear), carbon fiber is really only useful when it is under tension. Think of trying to bend a single carbon fiber, it won't support much load. So when any other force but tension is applied to a carbon fiber part, one that also includes resin, it is actually the resin that is carrying the load. Under compression, the carbon isn't doing anything, it's the resin. It's basicly the same for all the forces but tension.
So, back to being brittle. The example of a skid plate is actually a very good one. What is really needed is high shock resistance, we have a two ton car hitting an "immovable" object (a rock) at 35,60,90 mph. A metalic (steel or aluminum) plate is going to yield, bend and distort, but probably not break. It will probably keep you oil pan from getting a big old gouge or dent in it by getting torn up itself. It's a sacrifical item before any really important parts.
If we have that same impact hitting a carbon fiber plate, what is actually happening is that the resin is alowwing the structure (plate) to deform until the carbon fibers are placed under tension and are able to carry the loads (up to their breaking point). As long as the carbons yield strength has not been exceeded and the fibers have not been scratched or otherwise compromised, the structure maintains it's effectiveness and will work properly in the next impact. However the resin will be broken and cracked. If the yield strength is exceeded, the fibers will break and the structure is now useless.
The first problem is determining what kind of forces to design your structure, or plate, to withstand. The impact of a car hitting a bolder at 25mph is VERY different than 75mph. The plate for the 75mph crash will need to be signifigantly thicker than the 25mph. (I am not positive but I don't think that simply tripling the thickness would be sufficient). It may be that, for this example of a skid plate, the carbon will end up being heavier than an aluminum plate would need to be. Remember that if it isn't think enough it will be useless and your car will still get banged up.
The next problem is designing a structure that will not deform too much and end up transfering the load to your oil pan. The thicker, and heavier plate (than the aluminum) may be able to resist the impact but may bend too much.
Something that is brittle has a very low strain to failure rate, actually most resins are very brittle. They have a low tensile strength but are better in compression, they are also very rigid. This is why they are paired with something that is so good in tension but bad in compression, carbon. Most people think of carbon fiber being brittle because they have only ever seen the pieces that are for decoration, such as a pulley cover. They are very thin, have very few layers of carbon and probably have a very cheap resin. If you take a panel like that and bend it, of course it is going to crack the resin, but you probably won't be able to break the carbon fibers without some significant effort. That behavior is what carbon\resin composites are designed to do. A properly designed skid plate could withstand you taking a sledgehammer to it all day and you would probably only screw up the surface resin and the first layer of carbon. (fyi, if an individual fiber is damaged or compromised in any way, that fiber is no longer able to bear the same load, in the same way, as an undamaged fiber. This is why carbon is usually manufactured as a net shape and not machined)
Real world applications, a pulley cover is not load bearing and can be very thin, and needs to be in order to be light. A hood is also not load bearing and can be only a few layers of carbon, less than 1/16" and do it's job (which is covering the engine, nothing more). But all the hoods that I have seen are not made that way. They are the OEM shape, thickness and have the same structure on the underside that the metal ones need for support. Add in the fact that, most likely, the cheap ones are nothing more than one layer of carbon on top for looks and the rest is heavier fiberglass mat and I am not the least bit surprised that they are heavier than OEM. Real racing hood are probably exactly that, just a couple layers of carbon held on by hood pins. I have an old school fiberglass hood for my datson and while I haven't weighed both of them yet, I believe the glass one is going to be heavier. Same thing for my fenders.
Designing a carbon fiber part to meet all its needs is not cheap and if there is little or no design work done, the parts just aren't being made right. My opinion is that 99.9% of stuff out there is useless and a waste of money because of this fact.
It's late, I hope more coherent than most of Boxer3Main's posts.
04fxt
New member
Well this thread has turned to POOP.
I was going to try and do this in my spare time, as a hobby, and nothing more. I don't have any formal training, except for my self taught fiberglass. I didn't realize there were so many carbon fiber experts here, so I guess I should leave it to the pros. Sorry if I got anyones hopes up.
I was going to try and do this in my spare time, as a hobby, and nothing more. I don't have any formal training, except for my self taught fiberglass. I didn't realize there were so many carbon fiber experts here, so I guess I should leave it to the pros. Sorry if I got anyones hopes up.
stiXXX
Active member
OEM STI (not WRX) hoods are aluminum, not steel.
Fwiw. "wet" carbon has nothing to do with "frp" (fiberglass reinforced plastic) but Seibon's CF uses FRP as a framework for their wet CF hoods.
Their DRY carbon, RS-style hood weighs 4kg (8.8#)
XXX
Spiller1327
New member
I didn't mean to say carbon is brittle, just that a diff. cover isn't a good application for it. Where did u work or learn your composites Apollyon. You seem to know a lot. I'm 2 years into composites schools. 1 year under Mr. Macdonald and steve hassett with custom composites and 1 year in The Boat School under Bob Turcotte. I know quite a bit but plan to learn much much more. We build a Carbon BMW hood that fit seamlessly last year. We built a plug off the oem hood and made a fiberglass mold off that and then sprayed it with a uv protectant gel coat, layed 2 layers of 0-90 10 oz carbon, 1/4" foam core, then 3 layers of 10 oz biax glass on top of the foam. It was infused with vinylester. Came out amazing. Also stixx I didn't realize the sti hoods were aluminum. that&#39;s quite interesting. I still don't understand what you are saying about wet and dry carbon, Are u taking about infusion and hand lay or molding? You need a resin to keep the carbon together. Please explain. Sorry to 04fxt for ruining your thread, we should have started a new thread about frp.
Last edited by a moderator: