Carbon fiber is difficult to paint and coat. We use a plasma oven to change the surface tension.
I think you misunderstand the process. You're definitely talking about something different than what I am planning!
The process is simple and easy. It starts with carbon fiber cloth. I lay the cloth over the speaker box, and then spread epoxy resin over the carbon fiber cloth. The epoxy soaks through the carbon fiber cloth, stiffening it and bonding it to the wood.
Coating the resulting laminate is also easy. I just need a material that will bond to epoxy, which is pretty much anything. I'll spray it with a polyurethane clear coat (Auto body clear) because it takes a polish and is easy to work with.
The process is simple and easy. It starts with carbon fiber cloth. I lay the cloth over the speaker box, and then spread epoxy resin over the carbon fiber cloth. The epoxy soaks through the carbon fiber cloth, stiffening it and bonding it to the wood.
Coating the resulting laminate is also easy. I just need a material that will bond to epoxy, which is pretty much anything. I'll spray it with a polyurethane clear coat (Auto body clear) because it takes a polish and is easy to work with.
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There's not a whole lot to be gained from a wet layup skin of carbon over a speaker carcass. Without decent vac bagging to promote best adhesion to the substrate you'll only get part of the properties showing through, and even then it'll just mildly raise the Q of the finished structure, and not by much more than adding a single internal stiffener would achieve in all likelihood
\I didn't intend this to be a crash course in composites, but I feel it is irresponsible not to respond.
Vacuum bagging is typically done when you are using a mold. But building a mold is expensive and extremely labor intensive, so nobody would choose to build a mold for a pair of one-off speakers. Just thinking about it hurts my head!
Vacuum bagging is not magic. It doesn't "promote adhesion" or change the strength of a laminate. All it does is compress the laminate, which has the benefit of squeezing out excess resin. This just changes the ratio of fiber to resin in the laminate.
The strength of any composite/ FRP material comes solely from the fiber being used. The amount of resin doesn't affect the strength, as long as there is enough resin to bond all the fibers together. Adding more than the minimum amount of resin adds weight, but it doesn't increase or decrease strength. So excess resin from a hand layup process doesn't matter when building a speaker! In fact, I will add extra resin on purpose to fill the weave!
Some people just paint their speakers. Some people cover their speakers with fancy veneer. I want to have a "veneer" of carbon fiber on mine. It will look cool. And nobody else has one.
I am not using carbon fiber to improve the characteristics of the cabinet. The carbon will have an effect on the stiffness of the cabinet, but that is not my reason for choosing carbon.
Vacuum bagging is typically done when you are using a mold. But building a mold is expensive and extremely labor intensive, so nobody would choose to build a mold for a pair of one-off speakers. Just thinking about it hurts my head!
Vacuum bagging is not magic. It doesn't "promote adhesion" or change the strength of a laminate. All it does is compress the laminate, which has the benefit of squeezing out excess resin. This just changes the ratio of fiber to resin in the laminate.
The strength of any composite/ FRP material comes solely from the fiber being used. The amount of resin doesn't affect the strength, as long as there is enough resin to bond all the fibers together. Adding more than the minimum amount of resin adds weight, but it doesn't increase or decrease strength. So excess resin from a hand layup process doesn't matter when building a speaker! In fact, I will add extra resin on purpose to fill the weave!
Some people just paint their speakers. Some people cover their speakers with fancy veneer. I want to have a "veneer" of carbon fiber on mine. It will look cool. And nobody else has one.
I am not using carbon fiber to improve the characteristics of the cabinet. The carbon will have an effect on the stiffness of the cabinet, but that is not my reason for choosing carbon.
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I'm not sure how much the vac bag would add to adhesion. For the timeframe of curing (even 24 hours with the tropical hardener), I suspect the vac cannot drag epoxy too deep into the wood. Whatever wet obtained at the jump is probably all you will get.
Not sure what you mean by "Q" of the structure. I assume it meant increased resonant frequency, which I certainly agree with.
As to internal stiffener, I violently agree with you; the stiffener is far better at reducing panel movement than a one side laminate. I suspect even a two side laminate will require webbing between to add to shear strength.
Your explanation is great, thank you.
I was going to put carbon fiber weave over the rack cases I am currently building. but at 200 USD, I decided to try some "speaker paint" with a foam roller.
Not sure if I'll like it, but I'm not gonna date myself with carpeting, that's so 80's..
Still trying to design a decent case for the mixer though. The channel inserts are placed low on one side, and I think I need a back panel there for strength. I suspect I would never need the inserts, but can buy 1/4 right angle plugs if need be.
Already got the "demountable" hinges and the front locking "things" to be able to remove the top.
Edit. As to squeezing out resin, that will reduce the z axis thermal coefficient of expansion from close to the resin (90 ppm per degree C) to that of the fibers (10 to 12 ppm/degree C). Of course, that is below glass transition...above, it's roughly 120 ppm/C. During re-entry, that's a different story.. (don't ask)😳
If you are smart, you will not ask me how I know this garbage...
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Ed, you're channeling Homer...love it..
sq225917;
To quote Jack Reacher (the new one)... details matter.
When you make stuff at room temp up to 175C using resins, and then expect them to work at 1.8 Kelvin while supporting 5 to 10 kpsi forces in compression only, details matter.
We have to use filled epoxies using alumina powder, glasscloth, glass roving, carbon fibers to mitigate the shrinkage that would occur with unfilled plastics and resins.
Our current builds, upgrade magnets for that place in Geneva, are a nightmare as we have to vacuum impregnate structures that use glasscloth insulation. We can't use filled epoxies as the glasscloth would filter the particles out, leaving clumps that have TCE's around 8 PPM/C outside the cloth, and 90 PPM/C inside the coil wires where the TCE needs to be about 16. Unfortunately, the glasscloth insulation is the only insulation that survives the 800C bake required to convert niobium tin to superconductor.
As it is, the resin cracks all to "heck" anyway, so the magnets always require training to try and resolve some of the stresses built into the structure when it gets to 1.8 kelvin.
Current work challenge... we have roughly 600 PID controlled valve controllers, many starting to fail. I took one home and used the mill to open and do an autopsy. When the bit broke through the case, I could smell burned electronics.
The internal controller board looked perfect, but the lytic cap (50 volt/470 uF) had a bulging end. Tech unsoldered it, it reads 3 pF.
So now, I'm building an external diode/cap adapter that will provide the 24 VDC needed for the unit, hoping to recover about ten units that have stopped working so far. The replacements are roughly 300 USD and we've purchased 40 new ones to stock for repairs, so it'll be much cheaper if 2 dollars worth of components can recover the failed units.
I'm also hoping to extend the lifetime of the remaining controllers, as I am hoping that without the ripple currents the internal cap sees, it might live longer as it's ESR increases due to electrolyte drying.
See... be careful what ya ask for, I've been accused of "running at the mouth" so to speak... I deny that accusation (of course).🙄
John
sq225917;
To quote Jack Reacher (the new one)... details matter.
When you make stuff at room temp up to 175C using resins, and then expect them to work at 1.8 Kelvin while supporting 5 to 10 kpsi forces in compression only, details matter.
We have to use filled epoxies using alumina powder, glasscloth, glass roving, carbon fibers to mitigate the shrinkage that would occur with unfilled plastics and resins.
Our current builds, upgrade magnets for that place in Geneva, are a nightmare as we have to vacuum impregnate structures that use glasscloth insulation. We can't use filled epoxies as the glasscloth would filter the particles out, leaving clumps that have TCE's around 8 PPM/C outside the cloth, and 90 PPM/C inside the coil wires where the TCE needs to be about 16. Unfortunately, the glasscloth insulation is the only insulation that survives the 800C bake required to convert niobium tin to superconductor.
As it is, the resin cracks all to "heck" anyway, so the magnets always require training to try and resolve some of the stresses built into the structure when it gets to 1.8 kelvin.
Current work challenge... we have roughly 600 PID controlled valve controllers, many starting to fail. I took one home and used the mill to open and do an autopsy. When the bit broke through the case, I could smell burned electronics.
The internal controller board looked perfect, but the lytic cap (50 volt/470 uF) had a bulging end. Tech unsoldered it, it reads 3 pF.
So now, I'm building an external diode/cap adapter that will provide the 24 VDC needed for the unit, hoping to recover about ten units that have stopped working so far. The replacements are roughly 300 USD and we've purchased 40 new ones to stock for repairs, so it'll be much cheaper if 2 dollars worth of components can recover the failed units.
I'm also hoping to extend the lifetime of the remaining controllers, as I am hoping that without the ripple currents the internal cap sees, it might live longer as it's ESR increases due to electrolyte drying.
See... be careful what ya ask for, I've been accused of "running at the mouth" so to speak... I deny that accusation (of course).🙄
John
Doh. Seems to me if you power the thingies with DC to begin with the filter cazapatators won’t heat up.
Perhaps if the cloth filters the filler, you are using the wrong filler! Can we talk polar-nonpolar?
Doesn’t seem you are running at the mouth, just typing too much without editing.
Perhaps if the cloth filters the filler, you are using the wrong filler! Can we talk polar-nonpolar?
Doesn’t seem you are running at the mouth, just typing too much without editing.
Oooooh, you vill pay for your insolence.
The valve actuators are designed to handle either 24VAC or 24VDC, with a 2 to 10 volt PID input signal for valve position control. We use an omega panel mount temp controller to drive the valve position.
I was never involved in the controller design. But now that they are experiencing failures, they give me the failures so that I can produce an autopsy to determine the failure mechanism. I am THE expert at hurting myself with saws, milling bits, lathe tools, soldering irons, exacto knives, scissors, nail guns, table saws, and drill presses. (edit: I do not mention the kitchen, where I inflict wounds far more often and deeper than in the shop) Who else has the injury skills I possess, with finely honed blood stopping methodologies using PVC electrical tape and paper towels?? I am one of the world leading experts in stopping personal human circulatory fluid releases (self inflicted).
Edit: I will admit, I am incredibly afraid of trying to use super glue to close a wound, there is no way I would do that...
I took one unit home and used my mini mill to carefully expose the guts, finding the cap failure.
Flipping to DC is what I think can be used to stop future failures (you agree which gives me a more comfortable feel for that method), I can have them put a bridge into the chassis with a decent 1000 uF 100 volt cap to zero out the cap ripple currents within the valve control unit. I gave the tech a bunch of bridges from my supply at home so that he can build a proto.
Because the glasscloth sock over the super has a fine mesh, even 2 to 5 mil alumina particles will clump. The problem is the environment of the magnet is a very VERY high level radiation fan (an inch or two from a 7 TEV, ampere level proton beam bending in a 5 to 7 tesla field with the resultant radiation fan, even Kapton has issues at that level of radiation. We are using CTD 101, which apparently has high radiation resistance.
And, what??? I edited...
Current home challenge: I have a pair of omega pro 15s, so may be askin the guys here for either a horn cab, tapped horn cab, or reflex design to put them into. Maybe down to 50 hz, just for kick without real low end. PA stuff I could make using some kind of foam/fiber design for low weight but well engineered material-wise to fight the gravity increase.
John
The valve actuators are designed to handle either 24VAC or 24VDC, with a 2 to 10 volt PID input signal for valve position control. We use an omega panel mount temp controller to drive the valve position.
I was never involved in the controller design. But now that they are experiencing failures, they give me the failures so that I can produce an autopsy to determine the failure mechanism. I am THE expert at hurting myself with saws, milling bits, lathe tools, soldering irons, exacto knives, scissors, nail guns, table saws, and drill presses. (edit: I do not mention the kitchen, where I inflict wounds far more often and deeper than in the shop) Who else has the injury skills I possess, with finely honed blood stopping methodologies using PVC electrical tape and paper towels?? I am one of the world leading experts in stopping personal human circulatory fluid releases (self inflicted).
Edit: I will admit, I am incredibly afraid of trying to use super glue to close a wound, there is no way I would do that...
I took one unit home and used my mini mill to carefully expose the guts, finding the cap failure.
Flipping to DC is what I think can be used to stop future failures (you agree which gives me a more comfortable feel for that method), I can have them put a bridge into the chassis with a decent 1000 uF 100 volt cap to zero out the cap ripple currents within the valve control unit. I gave the tech a bunch of bridges from my supply at home so that he can build a proto.
Because the glasscloth sock over the super has a fine mesh, even 2 to 5 mil alumina particles will clump. The problem is the environment of the magnet is a very VERY high level radiation fan (an inch or two from a 7 TEV, ampere level proton beam bending in a 5 to 7 tesla field with the resultant radiation fan, even Kapton has issues at that level of radiation. We are using CTD 101, which apparently has high radiation resistance.
And, what??? I edited...
Current home challenge: I have a pair of omega pro 15s, so may be askin the guys here for either a horn cab, tapped horn cab, or reflex design to put them into. Maybe down to 50 hz, just for kick without real low end. PA stuff I could make using some kind of foam/fiber design for low weight but well engineered material-wise to fight the gravity increase.
John
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Seems like a good enough reason to me. Some people spend more on haircuts, and those don't last as long...
A conservative project cost estimate for successfully doing the carbon fiber would be to take your current estimate, and multiply by 2! Atleast 2x. It's all the little things that'll cost you.
I already spent a ridiculous amount of money on an ongoing product design project, so I just pretend the carbon, epoxy, and supporting accessories are all "free". It's a pleasant fantasy.
(I agree that applying an FRP layer on one side only does essentially nothing to increase the rigidity of a panel, and in addition it would introduce all kinds of problems with warping....which is why I will laminate both sides of the panels to create a balanced laminate. But only the outside will be pretty! All the test panels I made were laminated both sides.)
Try just using thinned down resin on mdf surface, it soaks in and cures very hard. Does not leave glossy finish, and adds at least 2x original strength AND waterproofs it.
Ive used thinned down polyester resin/lacquer thinner with good results on mdf and chip board and plywood...
Its cheap, and a very worthwhile upgrade on those sets of speakers that are mdf, but decently designed.
Use about 2 percent by volume curing component to 98 percent polyester. It takes 25-50 percent more catalyst than usual but still cures with the lacquer thinner as it cures and off gasses.
Use as much thinning agent as you like, its dependent on the consistency and penetrating properties you want. About the same as "half and half" or even whole milk works well.
It doesn't take much to get a uniform waterproof and nice satin finish on mdf. But it does take several coats because it soaks in so well.
It looks quite professional.
Best of all it adds rigidity and performance to any sort of mdf box like structure. It is like having a fiberglass or carbon skin, sandwiching the mdf, but its using the mdf fiber instead. It works quite well because surface adhesion is not a concern. Take a cross section of it and you will see about a solid 1/8th inch of penetration with the resin, because of thinning it down with lacquer thinner.
Does great.
I have done it with several subwoofer boxes, went well on those, and I will do it with my mdf enclosure mirage om-10 speakers when I completely restore them.
Ive used thinned down polyester resin/lacquer thinner with good results on mdf and chip board and plywood...
Its cheap, and a very worthwhile upgrade on those sets of speakers that are mdf, but decently designed.
Use about 2 percent by volume curing component to 98 percent polyester. It takes 25-50 percent more catalyst than usual but still cures with the lacquer thinner as it cures and off gasses.
Use as much thinning agent as you like, its dependent on the consistency and penetrating properties you want. About the same as "half and half" or even whole milk works well.
It doesn't take much to get a uniform waterproof and nice satin finish on mdf. But it does take several coats because it soaks in so well.
It looks quite professional.
Best of all it adds rigidity and performance to any sort of mdf box like structure. It is like having a fiberglass or carbon skin, sandwiching the mdf, but its using the mdf fiber instead. It works quite well because surface adhesion is not a concern. Take a cross section of it and you will see about a solid 1/8th inch of penetration with the resin, because of thinning it down with lacquer thinner.
Does great.
I have done it with several subwoofer boxes, went well on those, and I will do it with my mdf enclosure mirage om-10 speakers when I completely restore them.
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Like this?
When I'm machining molds out of MDF, I always seal them with epoxy. I kind of swore off polyesther resin a couple years ago in favor of epoxy. The epoxy costs more, but doesn't have the shrinkage issues that polyesther does.
But I admit I have been looking for an epoxy that cures faster, to seal MDF. I hadn't thought of using polyesther. When machining MDF I get best results machining when I seal the MDF before the final finish pass. That final pass takes off ~.010", and give an extremely smooth finish, since I'm essentially machining plastic.
The image is the baffle for the new speakers...atleast part of it. My CNC router is only a 30"x40" work surface, so I'm machining it in sections. I'm not worried about joints, because it'll all be covered with carbon fiber.
When I'm machining molds out of MDF, I always seal them with epoxy. I kind of swore off polyesther resin a couple years ago in favor of epoxy. The epoxy costs more, but doesn't have the shrinkage issues that polyesther does.
But I admit I have been looking for an epoxy that cures faster, to seal MDF. I hadn't thought of using polyesther. When machining MDF I get best results machining when I seal the MDF before the final finish pass. That final pass takes off ~.010", and give an extremely smooth finish, since I'm essentially machining plastic.
The image is the baffle for the new speakers...atleast part of it. My CNC router is only a 30"x40" work surface, so I'm machining it in sections. I'm not worried about joints, because it'll all be covered with carbon fiber.
Has anybody tried using premixed shellac to coat the mdf? Highly soluble, should penetrate deeply, dries quickly and is easily sanded.
ripblade: that sounds like a generic sanding sealer product to me.
The big question is what are you doing after you seal it? If you just want to sand it smooth and apply a clear finish, then sanding sealer is the product you want to use. Sanding sealer won't significantly change the properties of the material.
rschmitt100 seemed to be suggesting that the polyesther resin would increase the strength of the MDF. I don't know how it affects acoustics, but it would strengthen the material to a degree, although the result will vary depending on the grade of MDF you start with.
I'm using epoxy because I'm trying to create a hard surface on the MDF that I can sand smooth and ultimately apply carbon fiber over the top of. Or I can use autobody products over it, like primer and clear coat. The thing is I know that epoxy is compatible with all the products I'll be using along the way, so it is the obvious choice for me.
The big question is what are you doing after you seal it? If you just want to sand it smooth and apply a clear finish, then sanding sealer is the product you want to use. Sanding sealer won't significantly change the properties of the material.
rschmitt100 seemed to be suggesting that the polyesther resin would increase the strength of the MDF. I don't know how it affects acoustics, but it would strengthen the material to a degree, although the result will vary depending on the grade of MDF you start with.
I'm using epoxy because I'm trying to create a hard surface on the MDF that I can sand smooth and ultimately apply carbon fiber over the top of. Or I can use autobody products over it, like primer and clear coat. The thing is I know that epoxy is compatible with all the products I'll be using along the way, so it is the obvious choice for me.
hi fredygump,
nice baffle, I wonder if vacuum infusing mdf material would be possible.
It seems like the overall acoustic performance would be increased. The resonance of the cabinet might change, increase above the critical lower frequencies where most likely affected, and of course the designed resonance of the box shape and dimensions itself would stay the same or very close to that tuned specification.
Adding the stiffness helps mostly with the baffle front facing portion of the box, as any sort of resonance frequencies and inertia of the drivers will resonate, the more compliant the material the more likely for it to have those off tones.
The stiffer, the more higher the spl I would assume, and more of a monitor type of music generation where the input most closely matches actual sound wave output. Most made by the driver, then the tuned frequency lowend of the box, and then all the rest of it noise from the box vibrating.
I like boxes that are very heavy to counteract that.
Ive thought of welding solid 1 inch steel plate together to see what the drivers themselves sound like sealed.
nice baffle, I wonder if vacuum infusing mdf material would be possible.
It seems like the overall acoustic performance would be increased. The resonance of the cabinet might change, increase above the critical lower frequencies where most likely affected, and of course the designed resonance of the box shape and dimensions itself would stay the same or very close to that tuned specification.
Adding the stiffness helps mostly with the baffle front facing portion of the box, as any sort of resonance frequencies and inertia of the drivers will resonate, the more compliant the material the more likely for it to have those off tones.
The stiffer, the more higher the spl I would assume, and more of a monitor type of music generation where the input most closely matches actual sound wave output. Most made by the driver, then the tuned frequency lowend of the box, and then all the rest of it noise from the box vibrating.
I like boxes that are very heavy to counteract that.
Ive thought of welding solid 1 inch steel plate together to see what the drivers themselves sound like sealed.
rschmitt100: I'm not sure how you are thinking of doing an infusion? Vacuum infusion is just one technique, and I'm not sure why I would use that technique on this project.
The plan is a wet layup over the MDF. It's all that is required. I'm going to lay the fabric over the surface, and apply the resin on top. And I'll let the excess hang off the edges to cut once it is cured.
Vacuum infusion is good if you have a mold and are making complicated parts, because you have unlimited open time. But in my case, there is no mold, no flange. And doing it by hand will take less time than an infusion would take, even if you ignore the setup time. Another reason to use infusion or vacuum bagging is to reduce the amount of resin in the laminte, but in this case I don't care. I will be applying extra resin afterward to build up enough of a layer that I can sand everything flat, without going through the carbon.
I've put a lot of thought into how to coordinate the lamination and assembly, and the only thing I can imagine working well is to laminate the panels individually, and then assemble. The front and back panels include the side and top radius, so from the front or back it will be seamless. Side panels and top panel will be laminated separately also.
I am documenting as I go, and I'll create a build thread about it once I have one cabinet complete. It shouldn't take too long!
The plan is a wet layup over the MDF. It's all that is required. I'm going to lay the fabric over the surface, and apply the resin on top. And I'll let the excess hang off the edges to cut once it is cured.
Vacuum infusion is good if you have a mold and are making complicated parts, because you have unlimited open time. But in my case, there is no mold, no flange. And doing it by hand will take less time than an infusion would take, even if you ignore the setup time. Another reason to use infusion or vacuum bagging is to reduce the amount of resin in the laminte, but in this case I don't care. I will be applying extra resin afterward to build up enough of a layer that I can sand everything flat, without going through the carbon.
I've put a lot of thought into how to coordinate the lamination and assembly, and the only thing I can imagine working well is to laminate the panels individually, and then assemble. The front and back panels include the side and top radius, so from the front or back it will be seamless. Side panels and top panel will be laminated separately also.
I am documenting as I go, and I'll create a build thread about it once I have one cabinet complete. It shouldn't take too long!
Thats just an aside.
Im always thinking on ways to improve materials Economically...
With carbonfiber laminations of any woodlike structure, you would probbably HAVE to vacuum laminate, as epoxy buildup is always a hassle, has to lay flat, be even, conform to corners and edges, no air gaps etc.
I say forget laminating with cf, its always a hassle, is tedious and is too expensive. Nice wood grain, stain or well pigmented paint will probably be an adequate finish, unless ones goal is to make it completely difficult and nearly unachievably perfect
Shoo why not gold leaf finish it instead?!?
Europe/german specialized lumber stores sells cf laminayed plywood which is just compelety awesome.
Im always thinking on ways to improve materials Economically...
With carbonfiber laminations of any woodlike structure, you would probbably HAVE to vacuum laminate, as epoxy buildup is always a hassle, has to lay flat, be even, conform to corners and edges, no air gaps etc.
I say forget laminating with cf, its always a hassle, is tedious and is too expensive. Nice wood grain, stain or well pigmented paint will probably be an adequate finish, unless ones goal is to make it completely difficult and nearly unachievably perfect
Shoo why not gold leaf finish it instead?!?
Europe/german specialized lumber stores sells cf laminayed plywood which is just compelety awesome.
LOL! How can you give me advice about composites? It's nice that you know vacuum infusion exists, but I don't sense you have any experience from which to base your opinion. I would be surprised if you have ever handled raw carbon fiber, let alone laminated something with it.
You're forcing me to be a broken record. I'm making it from carbon fiber because I want to. I have the carbon fiber on hand...I actually have a couple different weave options to choose from. It'll be cool, and nobody else has one. Wood veneer speakers with square corners are boring because it's easy and everyone is doing it....they're doing it because it's super easy!
We all set standards according to our abilities and experience, and you're projecting all kinds of assumptions onto my project! What I'm doing may seem difficult to you, but to me I'm just building on previous projects and experience. I know what I'm doing, and I know it'll turn out great.
You're forcing me to be a broken record. I'm making it from carbon fiber because I want to. I have the carbon fiber on hand...I actually have a couple different weave options to choose from. It'll be cool, and nobody else has one. Wood veneer speakers with square corners are boring because it's easy and everyone is doing it....they're doing it because it's super easy!
We all set standards according to our abilities and experience, and you're projecting all kinds of assumptions onto my project! What I'm doing may seem difficult to you, but to me I'm just building on previous projects and experience. I know what I'm doing, and I know it'll turn out great.