[jrebman]

I'm considering using some carbon fiber panels for top plates on a set of two monoblocks and matching preamp, but I really have never workedwith CF before so I'm not sure what's involved as far as tooling, safety, lubricants, finiishing, etc.

If there's anybody out there who has experience with working with CF and can guide me, it would be much appreciated.

Thanks,

Jim

[Mikeinsacramento]

I've never done it, but there are tons of video on youtube showing you how. 

[Peter J]

I'm considering using some carbon fiber panels for top plates on a set of two monoblocks and matching preamp, but I really have never workedwith CF before so I'm not sure what's involved as far as tooling, safety, lubricants, finiishing, etc.

If there's anybody out there who has experience with working with CF and can guide me, it would be much appreciated.

Thanks,

Jim

Jim, I've done a little layup with carbon fiber, and a bunch more with fiberglass. It's usually set with epoxy resin and best results will be with a vacuum bag. Are you talking about laying up panels or buying them and machining to size?

Friendly guys here to supply and help if you're doing from scratch:

  http://www.fiberglasssupply.com/

If you're just talking machining panels to size, woodworking tools will be fine. Clear finish? I prefer lacquer or catalyzed urethane...either can be sanded and buffed to look great. BTW, I'm not talking about oil based polyurethane you would buy for wood finishing, that's a different animal.

[Jazzman53]

Hi Jim,

The previous post might be a good source, especially if they can provide a precured panel for you.

I've worked with aerospace composite materials, including carbon composites, for more years than I care to admit.

Generally, carbon laminates would be used where low weight, high stiffness, high strength and resistance to fatigue and corrosion would warrant the high cost of the material and fabrication.  From a structural standpoint, a carbon fiber laminate would be over-kill for an amp cover but I suppose if you like the sexy look of a highly polished woven carbon laminate, it would be different, at least. 

Most aerospace applications would use what we call "prepreg" fabrics; which would be carbon or other fabric that's pre-impregnated with a thermosetting epoxy resin.  The thermoset resin transitions (irreversibly) from a highly viscous liquid to a very hard solid when exposed to heat.  Prepregs come on rolls with a non-stick poly backing on both sides and is stored in a freezer at zero-degrees F or below because it starts setting when exposed to heat (any heat) It's good for 6 months at zero degrees but 250 degrees will transition it to a solid in a few minutes.  We cure it at 350F for 2 hours to achieve it full properties.

You can also buy the dry woven carbon fabric and a two-part catalyzed resin that sets at room temperature and mold anything you want.  Even though you can use a room temp curing resin system, the resin matrix will soften to a rubbery state if exposed to heat thats much above its curing temperature.  So, if you expect the panel to see any heat in service, you would need to first post cure it in an oven for a couple of hours at a higher temperature than it would see in service (to raise its "glass transition temperature").  Also, you would need to lay it on a flat surface to post cure it, as the resin matrix will initially soften at the glass-transition temperature.  Once post cured, it can't soften unless you exceed it's post-cure temperature. 
   

To mold a laminate you need a mold coated with a non-stick release agent (you could probably get by with several coats of a good carnuba car wax).  The surface finish will only be as good as the surface of the mold.  A pane of glass coated with car wax would give a fairly nice finish.  You could also scuff sand the finished panel and spray on a clear coat of paint and then buff it to a high shine. 

The easiest way would be to buy a precured carbon panel.  Even better if it's precut to size; otherwise, you would need a diamond grit cutter wheel to trim it to size (carbon is very hard).  But don't expect to find any at a cheap price.   

[bregez]

The easiest way would be to buy a precured carbon panel.  Even better if it's precut to size; otherwise, you would been a diamond grit cutter wheel to trim it to size (carbon is very hard). 

Just would like to add that if you plan on cutting a precured panel, it may be a good idea to do it outside with at least a dust mask or better a canister type respirator.  Carbon dust is not good for the lungs.

[jrebman]

Folks,

Thanks much for all this, and yes, I should have said that I would be using a precured, and probably, pre-cut to size thin panel (approx 0.100", though the molding possibilities could be interesting for some other things later on.

The machining is somewhat minimal, but would involve a large-ish rectangular hole for a horizontal, drop-in transformer, and then some larger holes for ux4, noval and octa tube sockets.

I have a good master drill index of ti nuitride bits and figure the rectangular holes could be made with a pilot hole in each corner and then using an abrasive cutter in my dremel, but the only thing I have available for the larger holes is a nice set of 2-flute Greenlee unibits (which work so much better than any other unibit I've ever tried), but I still don't know how well they'd work in the CF panels.

Peter J, thanks for the finishing tips, and I'd likely take the finished plate over to Ruben of Fallen Enclosures fame and let him clear coat it with a 2-part urethane and buff it to a black mirror finish.

So yes, in effect, I'm going for both a look and as a sort-of experiment with materials resonances and tube amps.  I'm familiar with the aluminum, buwant to see if the CF adds, subtracts, or has any effect at all, and in what way.

If this works out, there will be a nice PP el84 amp project that will have a CF top on a stacked BB ply base.  Then again, if I go into sticker shock when I price out the panels, I may skip it for the trio and just use it for the PP amp, which would also negate the need for a large rectangular cutout.

Also, thanks for the tips on the dust -- either shop I'd be using is well ventilated with air cleaners and nice dust collection systems, and both are essentially double-car grages so thedoors can be opened too, and I don't work with most woods without a respirator.

If any of you know the book on Wood Technology by Richard Jagels, he goes into wood toxicity pretty thoroughly and there is a lot of good advice in there.

Thanks everybody for the info, links, and input.

-- Jim

[TomS]

Jim,

Here is a nice source for carbon fiber sheets and a great variety of material. You could certainly use this is a veneer of sorts. http://dragonplate.com/default.asp

Tom

[jrebman]

Tom,  Wow, great link -- thanks!  I see something there that looks even more interesting -- a birch ore CF sheet.  This is something I'm going to have to look into more closely as I've long thought that a wood top on a SE tube amp would be desireable, when you look at the problems with heat, heavy transformers, etc., it soon starts to look not so appealing, this cf/birch sandwich looks really interesting through.  I could easily get two 8-1/2" x 11" tops out of a 12" x 18" sheet.  Hmmmm, going to ponder this one a bit, but sounds interesting to say the least.

Thanks,

Jim

[jrebman]

Just A little update:  Looks like the working max temp for the cf plates is 140 F, which is a bit too low for my intended use, but I'm sure I'llfind something to build with this material sooner or later.

-- Jim