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| Shaping braces with carbon fibe laminate http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=21333 |
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| Author: | Cecil [ Thu Mar 05, 2009 10:24 am ] |
| Post subject: | Shaping braces with carbon fibe laminate |
If you who use carbon fiber laminates for your braces how are you shaping them? They are destroy the edge on chisels and plane irons. Sandpaper leaves an unsightly mess with dust embedded in the grain of the top. The only thing I have found is a rasp or rotary file. The leave particles large enough to be blown away without staining the top. You must avoid wiping so as not to rub it into the grain. Also, I rough shape my braces with a scroll saw. A blade will do about one set of X-braces but they are are not too pricey. Cecil |
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| Author: | Hesh [ Thu Mar 05, 2009 10:46 am ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
Cecil my friend I recently started using CF laminates for some of my braces. What I do starts with sizing the laminates so that minimal cutting will be required for exactly the reasons that you are encountering. No one wants to be dulling their tools just to make a brace.... So I use strips of CF that once laminated I only have to make one cut and then I do the shaping on a spindle sander with dust collection and a respirator on. You do not want to breath CF dust so this requires a respirator and good dust collection as well as a good clean-up afterwards. For the upper transverse brace for example I will use a 19" X 1" piece of CF in the thickness that I like and laminate it with spruce on both sides. After the epoxy is cured I cut the brace at an angle with a utility knife so as to now have two pieces that are each big enough to get a UTB out of - in this case for an L-OO. This single cut with a utility knife will dull the utility knife blade too but that seems to be the cost of using CF. The cut is made from both sides of the stock scoring the CF. Once I am through the wood on both sides and the CF is well scored I snap it apart with my hands. You don't have to cut all the way through the CF. Then I shape, shooting for the final shape that I know I need, the braces on the spindle sander. The last step is removing the excess spruce only from the sides of the brace to make the profile that I need. I don't cut the CF or shape it again so my chisels and planes never touch it. For now I am only using CF for UTB's. I can't see how one could use it for other braces unless they either use edge tools while voicing and cut the CF dulling tools or have a proven design precluding the need to reduce brace height after gluing them. I suppose that they could be sanded with a Dremel and sanding drum but the dust would be something that we need to be very careful with. |
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| Author: | Bob Garrish [ Thu Mar 05, 2009 1:54 pm ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
As a general rule, when dealing with 'gross and abrasive', which includes CF and other equally nasty things (G10 FR4, for the record, is the devil!), I go with disposable tooling of some sort. If you're cutting, then go buy a pack of 100 razor blades for $5 and use those. There's always sanding to shape, with proper dust collection, as well. The magic bullet, BTW, for cleaning dust off of and out of wood is the highest pressure compressed air you can get. 120 psi does wonders on cleaning things you wouldn't think were cleanable. Just be careful not to spray the CF dust everywhere (I vacuum and THEN hit with the air!). |
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| Author: | Jim Watts [ Thu Mar 05, 2009 9:09 pm ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
You might put some masking tape down in the area your working, vacuum it up or blow it off like bob suggests. Believe it or not a nice eraser will remove the smudge marks also. And as Todd points out a dust mask is always appropriate. |
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| Author: | Cecil [ Fri Mar 06, 2009 9:56 am ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
That's what I thought,no magic bullet, but thanks of the replies guys. I use carbon fiber in my X-brace so I have some to remove during the voicing process. The rasp works fairly well for smaller cuts and the rotary file will remove gross amounts very quickly. With the rotary file avoid applying pressure to the cut, use a wiping motion as though it were a Q-Tip. The rasp is a dedicated, inexpensive, hardware store variety. When it gets dull it is cheap enough to just toss it. As stated above, dust collection and a respirator required Cecil |
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| Author: | Flori F. [ Fri Mar 06, 2009 12:12 pm ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
Cecil wrote: That's what I thought,no magic bullet, but thanks of the replies guys. I use carbon fiber in my X-brace so I have some to remove during the voicing process. The rasp works fairly well for smaller cuts and the rotary file will remove gross amounts very quickly. With the rotary file avoid applying pressure to the cut, use a wiping motion as though it were a Q-Tip. The rasp is a dedicated, inexpensive, hardware store variety. When it gets dull it is cheap enough to just toss it. As stated above, dust collection and a respirator required Cecil Cecil, Can I ask what thickness you're laminating into your braces? Also, I'm curious to know how you decided on the thickness. I've been considering the option, and trying to weigh the merits of .01 stock versus .02, etc. Thanks. Flori |
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| Author: | Cecil [ Fri Mar 06, 2009 12:56 pm ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
Hi Flori, I confess to having no real scientific reason for the choice, other than it was it was the middle of what was offered. I believe that it is probably the best for my application,but it seamed to worked the first time and I have not tried anything else. I decided to try it to try and control the belly behind the bridge. So far it is working as I hoped it would but the first one is only 5 years old so i really need more time to make a final judgment. Cecil |
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| Author: | Flori F. [ Fri Mar 06, 2009 2:53 pm ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
Thanks for the reply Cecil. I'm interested in laminating for the same reason, but (as this thread points out) the shaping of the braces does seem to be an obstacle to voicing. |
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| Author: | Brook Moore [ Wed Mar 11, 2009 11:32 pm ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
It is pretty easy to shape CF/spruce laminate braces with sanding blocks. I use self-adhesive 80p grit on a hardwood block or a piece of pvc pipe. Sand a bit, then vacuum and you won't have too much mess. Sand across the brace, not lengthwise. Do as much shaping as possible before you glue the braces to the top, and then do as much as possible before gluing the top to the ribs. If you run your braces right through the ribs, as I do, you will want to make sure the CF does not extend into the area that you hit with the router bit when doing the binding. In tests I made a few years ago, I found that .020 CF gave me the same stiffness as good spruce, weiging about 20% less, as I recall. The .030 was too stiff and heavy for me, when used with spruce. I tried some .030 with balsa, and it gave me stiffness in a much lighter package, but I abandoned that experiement due to concerns about the long term strength of the balsa-to-spruce joint, and damping issues. I also tested .030 CF with red cedar, but did not see any benefit in a brief test. I have not done any measurments with the .010. Brook |
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| Author: | Cecil [ Thu Mar 12, 2009 8:54 am ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
Brook, I have used 60 and 80 grit sandpaper also but find that the rotary file leaves larger particles that are easier to clean up and less likely to become air borne. The file works best with an air powered die grinder. It can also be used with a laminate trimer although the bulkier body makes it less than ideal. As with all things in luthiery. there are several ways to arrive at the same result. Cecil |
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| Author: | Flori F. [ Thu Mar 12, 2009 10:13 am ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
Brook, Thanks for sharing that info. |
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| Author: | Brook Moore [ Thu Mar 12, 2009 10:56 am ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
I have used the mini sanding drums on a Dremel for shaping the braces once they are glued to the top, but before the top is attached. That is a serious mess, but pretty fast for taking off larger amounts. Thanks for the tip on the rotary file bit, I'll check that out. However, once the top is attached to the body, I am not very interested in using any sort of power tool inside. By the way, I have stopped using the laminate braces on the tone bars and the finger braces, to make the top easier to adjust in those areas. I do all of the initial shaping of the braces on the end roller of my edge sander, and they are 90% to final shape when they are glued to the soundboard. Usually now, I am not touching the laminated x-brace after the box is assembled. Brook |
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| Author: | Darryl Young [ Thu Mar 12, 2009 12:18 pm ] |
| Post subject: | Re: Shaping braces with carbon fibe laminate |
Brook Moore wrote: In tests I made a few years ago, I found that .020 CF gave me the same stiffness as good spruce, weiging about 20% less, as I recall. The .030 was too stiff and heavy for me, when used with spruce. I tried some .030 with balsa, and it gave me stiffness in a much lighter package, but I abandoned that experiement due to concerns about the long term strength of the balsa-to-spruce joint, and damping issues. I also tested .030 CF with red cedar, but did not see any benefit in a brief test. I have not done any measurments with the .010. Brook Does anyone gain enough stiffness adding CF to use a shorter brace possibly decreasing weigh even more (with the same stiffness)? |
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