Bridge patch and bridge.

[DarwinStrings]

G'day Trevor. Is the CF you use under the bridge patch and in the bridge mainly for stiffness across the sound board or does it need to add stiffness along the soundboard as well?

Jim

[Trevor Gore]

It's mainly there for stiffness across, because the bridge/bridgeplate assembly is pretty well the only thing that crosses the centreline on a falcate braced guitar, unlike the X-braces on a typical Martinesque guitar. The primary and secondary falcates provide the longitudinal stiffness to dump most of the torque over the soundboard and onto the rims, so by messing with how much and where you put the CF in the bridge/bridge plate you can play with the dynamic stiffness of the soundboard whilst knowing you have enough longitudinal stiffness to cope with the static torque.

[DarwinStrings]

Thanks Trevor. Can I assume from that that I can use unidirectional tape for the patch and bridge running across the board. I need to buy 3k tow as I only have 6k and splitting it seems a bit rough so thought I might be able to kill two birds with just the tape.

Jim

[Trevor Gore]

I've always used woven cloth. I think you may find the uni-directional stuff hard to use, though I've never tried it myself. There's a good discussion here about the options that some of the guys have tried.

[DarwinStrings]

I have read through that Trevor, have read this whole section of the forum. I could use the 6k tow I have but figure why use twice as much as I need. Also I have sandwiched CF tow between pieces of wood in the same way you use the mat so that won't be a problem. Oh, well, maybe cutting the shape and holding it all together might be easier with the mat thought the tape does have a bit of fiberglass across it to hold it together.There is a slight difference between tape and mat/cloth in that the mat has "hairspray" on it and tape as well a tow don't have it. The "hairspray" doesn't make much difference except that it can hold a little bit of those kinks in it when you pull rove from mat.

Jim

[Trevor Gore]

OK, Jim. It sounds like you've tried a few options already. Have a go with the 3k tape. With the experience you already have, I reckon you'll do fine. If it all goes pear shaped, just pull it and get the acetone out, then have another shot. No big deal! There should be no structural implications of doing it that way. You could also try Dom's method of laminating up the bridge plate with the CF first, then cutting out the shape, then gluing down the lamination onto the soundboard. It's two operations rather than one, but should get you out of jail if the unidirectional tape won't behave right.

[DarwinStrings]

Thanks again for your help Trevor. Just in case anyone else is looking for CF tow or mat "Carbon Fibre Australia" sell online and use Paypal. Their products are from Toray and although they do not list 3k tow they can get it for you in the form of the last bits on the spool from Toray (there is quite a bit left on the spools when they manufacture the cloth as they change spools before they empty) however the unidirectional tape is the same as the tow and can be bought in smaller quantities (per metre in fact for around $6 or $7 per metre for 75mm wide). One other thing I checked that didn't seem to be mentioned in the CF thread is the difference between 198g and 200g, this is a description of how bunched up the rove is in the mat, so more or less strands of rove per metre.

Jim