very new and first project

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#1

I am going to make a carbon fiber intake scoop for a motorcycle that will show the weave. For simplicity, think of it as a cone shape. I made one out of laminated rigid foam insulation to confirm the design. I am now wondering how to form the mold.

If it is made from a female mold, I assume it would need to be made in two pieces and each piece will be bonded together, since you could probably not work from within the open end of the cone. If this is the correct way, how would you make sure the two pieces fit together exactly? Is it just by simply making sure the two molds are accurate and the final trimming is accurate?

Is there another way to make it from a single mold?

If it requires a male mold and a lot of finish work to get the outside smooth, how would you get the foam out from the inside after it sets up? is there another amterial I should use?

Thanks,

Chris

#2

Im assuming youre actually making a cone.

The cone could be made from foam and cut/sanded to shape. Finish the outside of your cone to perfection and make sure it is actually a cone (meaning it has draft. Then prime it and polish it like crazy.

Lay up your material and use some sort of film like bagging film to compress and hold it to your cone. When its cured use more material to make it thicker and the slide it off your cone.

It should look pretty decent on the “inside” of the duct which is what I imagine you are going to use as the “show” side and if not you can always spray some auto clear coat to make is smooth and shiney.

This is a male mold seeing as your inside is your show piece.

Drawings would help me more though, Im a motorcycle guy as well

#3

I will make the mold and finish it as well as possible. It is really not a cone shape but somewhat similarso how do I pull the mold out of the part? There is nothing to grab and since it is a male mold, I cannot do much prying the part away from the mold. I would love to keep the mold for another part so I would rather try pull the part off the mold instead of dissolving the foam mold inside the part.

Thanks,
Chris

#4

Without actually see a picture, it is hard to fully answer this question. If this is not a one off part, then you will need to take the time and make a multi flanged mold from your plug.

You might want to make the first one as a one off and test fit on the bike. Then re-engineer any changes and make a final proper mold.

#5

Well Im going off what youre sayign your making…

If its a ram air duct, you have to have an open end for the air to end up going into the tubing leading to your airbox.

this is ghetto but

now see what I mean about the draft angle and the straight tube end for where you will attach your ducting to? If you built your cone out of foam and shaped it like what you see above you would have draft and on both ends you wouldnt be making anything.

So, now we have the rough shape for draft and what not…

When you use the foam and bondo…sand it smooth as possible and then prime it. Sand it and polish it to super glossy and then wax the piss out of it…like 8 times. Do as I posted previously and you should be money with the first layer and remove the bagg…then build up your thickness.

Then you should be able to push the plug out from the duct. If you cant, you didnt have it smooth and drafted. You would have left waves in it.

If you know someone with wood working tools you can do this with wood and prime it and polish it as well.

#6

Hybrid,

Think of the shape as something like a mailbox that decreases in size toward the back of the mailbox, so it will have enough draft. There will be a hole cut in the bottom of the mailbox shape to attach to the carb once the part is complete. Since I will not have an open end to push the part out and only a shallow draft angle, how can I get the mold out of the part?

How many layers of material do you think I should use?

Thanks,

Chris

#7

Well there are two schools of thought here.

Make the plug and then build a mold that is at least two parts and flanged. (alot more work but will give you the cosmetic side on the outside of the duct if it is visible from the outside of the bike.

Or…

Build the plug, make the part and then start digging the foam back out. After you get it started to come out in chunks it will eventually fall out. The downfall here is that its a one time use. Its cheaper and easier to build but you only have one shot at it.

Now only because I know alot about this subject do I dare threadjack this…

Do you know what your calculations were for this ram air duct?

Do you know why you are designing it like you are?

There is a lot more to this unless youre just trying to get cold air intake.

You should draw some of this stuff up and scan it, save to an image hoster and let me see what youre trying to do.

#8

Also, it sounds like you will have to make 2 seperate parts and bond them together too.

#9

ah yes I meant to say that!

#10

I took a photo of my screen showing a rough dxf file of the intake. I want a formula 1 style intake shape. I dont care too much about performance/sizing because it is cosmetic only.

If I made a two piece part and bonded them together, do I then cover the entire intake with another layer of CF to eliminate the seam?

I might first try the styrofoam one shot male mold for my first part and them go for a better quality multiple use mold for my next piece.

Thanks for the help.

Chris

#11

If you make it in two parts just try to hide the seam, if you cant this pic my give you a idea for a seam line.

It can get ugly on the inside but you can sand it out if needed.

#12

Well what you would do for the male disposable mold is to lay it up with a couple layers of fiberglass. Then do what is called an OVERLAY with a layer or two of carbon fiber. I would hide your seams on the side that is not easily visible. Going off your drawing it would seem that you could easily do this, then chip out your male plug and call it a day. Ill try to draw a pic and scan it as this computer doesnt have any cad on it and I hate trying to work with paint… hahahaha

#13

DUDE I LOVE HOW YOU GET THAT TEX TO SEAM UP SO CLEANLY!

#14

Yet another ghetto paint picture…I was going to just draw it and scan it but it would be massive in file size. My scanner doesnt like poor resolution…haha

If you look at my crappy drawing, youll see I have a gray shaded area. That should be recessed with a smooth bead befor going flat. You can do that with the foam and some bondo and a shaper.

Why? because thats how we make the “inlet” appear to be professional. (At least this is how I would fabricate this thing)so say its inbetween an 1/8th to a 1/4" in its radius.

The red line (which may have gotten chopped a bit is supposed to represent how you would wrap the layers of cloth around it so your seams would end up on the exit plane (indicated by the blue lines representing the diameter of the carb flange) I would wrap a couple of layers of fine cloth to start a base on. Maybe even some surfacing veil to build the initial layers. your seams wont matter with the plain glass as it wont show. Make sure you make cuts of material to go on your recessed portion as it will help to anchor your carbon around your recess later on and you will trim it out when you are done.

Anyways after you lay a couple layers, let it cure and then scuff it down (if your resin blushes especially) and lay a couple layers of heavier plain weave glass.

After that cures, you should be pretty money for OVERLAYING your carbon cloth. This will be a piece thats obviously bigger than the part. There are lots of opinions on how to overlay but I struggle with it.

If I was doing that part, Id carefully start applying some resin to just a single side of the triangle (being really carefull to stay away from the radius) and letting it B stage so it holds the cloth taunt. This way you wont have airbubbles or lifting of the cloth. Then pull it tight and do the next “flat” and so forth. Finally cutting your wedges out to get it to fold over the radius and since you are cutting the “inlet” out of it, we dont care about the center of that.

Your angle of the weave orientation will be the part that makes or breaks you on how well it lays around the duct. Id expect to have double the amount you think you need as you will probably need to cut it one way and hope it lays right but may not and need another angle on the weave.

This is a pretty cool idea and Im assuming it for a harley or some V twin that has a side mount air box.

#15

fz1,

I also love how the pattern lines up. When matching the halves, how do you make the straight cuts perfect? I assume there is extra material that extended beyond the mold. Is that just cut and sanded until it is straight?

Hybrid,

It is for a Harley pro street style bike with the carb on the side. I agree that there should be a rounded edge on the inlet and I am going to try to make it. Thank you for the layup info.
I will do what you suggest. As most on these forums have mentioned, I would love to take a class. It would speed up my knowledge of making parts.

Chris

#16

You dont need it. I bought the vids form fibreglast (which most of them didnt help but the original mold building one did) and the rest I gleamed from here or racing composites.

There is tons to learn and the only real way is to try it.

If I was building that part…Id probably have it done from start to part in about 3 days. I dont like to constantly work at one thing…you get frustrated and start making mistakes.

Go get some foam and what not and have at it. Its really not that hard.

#17

That tail is carbon, my camera sucks LOL.

for that part I have a “cut” line and a "align"line in the mold. The cut line makes a ridge in the gelcoat for cutting.

The “align” line is for the fabric layup. and is about 1/8" above the cut line.

I cut the fabric a bit larger then what is needed for the side, then pic one strand of the fabric and run it along the “align” line then lay the fabric in the mold like any other. It comes out close.

Then I take the two parts when there trimed and use a flat file to make the edge. hold the two parts with modle airplane glue then run some fabric on the inside with epoxy.

Its more work but if you cant hide the seam it works well for me anyway.