Official Luthiers Forum!

I meant to ask this quite a while ago. If I did, I can't remember what folks said, and can't find it. When I glue carbon fiber bars in my neck, the epoxy and trapped air conspire to push the CF back up out of the neck. How would a guy avoid that? Am I cutting the slot too tight?

Thanks,
Mike

_________________
Mike Lindstrom

Eat more slowly... Seriously, either slide it into the slot from the end to avoid trapping and compressing the air, or clamp it down thus leaving compressed air in there, or else provide some escape path ( a hole somewhere? ) for the air. Those are the tings I'd try, anyway. I'm going to be trying to use CF soon myself so maybe I'll find out.

Cheers,

Alan

That can happen when gluing things with epoxy. There has to be adequate clearance for squeeze out. I usually make the slot wide enough so the CF rods will just fall out during a dry fit if I turn the neck upside down. When I glue I push the CF into the slot and hold it down while the excess epoxy escapes. Only takes a short time. Other option is to clamp it so it can't move while it sets. Also try not to use too much excess epoxy in the glue up.

_________________
Steve Smith
"Music is what feelings sound like"

Since my router bits are the same size as the rod I'm cutting the channel for, I just cut the channel a little deep and clamp until cured.

_________________
Joe Beaver
Maker of Sawdust

I cut the slots with the 1/8" table saw blade and if the rod fits too tight run it through your thickness sander to tweak it. I cut the slots just a hair deep. Clamp it during glue up. I just use 1/8" dowels with wax paper under and spring clamps. I usually mask off the fretboard during installation, it can sure get messy!

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

LOL!

Mike

Is there a rule on how much gap epoxy can fill or what's optimal?

_________________
Mike Lindstrom

If the CF rod is too tight in the slot, I just sand it a tiny bit thinner. I like to sand the CF with 220 grit anyway to scratch the surface a bit. The tiny scratches seem to give the epoxy an escape route. Personally, I think the CF should be firmly bedded into the bottom of the slot, without a thick layer of glue underneath.
Easing the corners is a good idea, on machined CF rods, which have sharp, square corners. A few quick strokes with 220 sandpaper does the trick.
To prepare the neck, I cover the entire surface with masking tape & then cut the tape away from the slots with a sharp x-acto knife. Makes cleanup a snap.

I do something similar except I just put masking tape on - no cutting.

_________________
Steve Smith
"Music is what feelings sound like"

You could cast a neck out of epoxy, so there's no issue with gaps.

Any trapped air will seep out eventually, so you just need to hold the rod in place until the air pressure leeches out. As others have suggested, I'd clamp down the rod until the epoxy cures.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

I honestly did not know you needed to glue a CF bar. Assumed that the expoxy used in the FB glue up was enough. I've only done one so far, a uke. Is this something I need to do?

Mike

Mike, it needs to be securely glued IMO, so if the neck wood trys to bow, the CF will resist it in shear (rather than just slipping in the slot). Ideally, it should be a zero creep glue joint (which is what is in shear).

_________________
Dave
Milton, ON

Ok then. I will add that to my process. Is epoxy zero creep?

Thanks Dave

Mike

The label begs the question: What is Sticky Ass Glue made from?

Mike

+1 this works

_________________
The Shallower the depth of the stream , The Louder the Babble !
The Taking Of Offense Is the Life Course Of The Stupid One !
Wanna Leave a Better Planet for our Kids? How about Working on BETTER KIDS for our Planet !
Forgiveness is the ability to accept an apology that you will probably NEVER GET
The truth will set you free , But FIRST, it will probably Piss you Off !
Creativity is allowing yourself to make Mistakes, Art is knowing which ones to Keep !
The Saddest thing anyone can do , is push a Loyal Person to the point that they Dont Care Anymore
Never met a STRONG person who had an EASY past !
http://wiksnwudwerks.blogspot.com/
http://www.facebook.com/groups/GatewayA ... rAssembly/