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Before gluing braces . . .
Posted: Sun Sep 10, 2023 8:40 am
by Gary Davis
. . . do folks scrape or plane the bottom of the braces after shaping on the radius dish and the corresponding locations on the top . . . or not? If not, why not?
Thanks y'all.
Gary Davis
Re: Before gluing braces . . .
Posted: Sun Sep 10, 2023 9:33 am
by tippie53
no the dish does the work
Re: Before gluing braces . . .
Posted: Mon Sep 11, 2023 9:11 am
by Gary Davis
Thanks John.
Re: Before gluing braces . . .
Posted: Mon Sep 11, 2023 11:20 am
by phavriluk
I do wipe the dust off as much as I can...
Re: Before gluing braces . . .
Posted: Mon Sep 11, 2023 6:33 pm
by Bob Gleason
I make all my curved bracing with a handplane and a simple jig, so I have a very smooth gluing surface to begin with. The whole bracing thing is way over thought IMO. If you have a decent fitting joint, modern glues do the work. To get into the complexity of perfect brace fitting into the geometry of the spherical top or back, is completely mind boggling. If we can get close, whether it is done by CNC or by hand, the glue takes care of things.-Bob
Re: Before gluing braces . . .
Posted: Tue Sep 12, 2023 8:48 am
by Gary Davis
Thank you Peter and Bob.
Re: Before gluing braces . . .
Posted: Tue Sep 12, 2023 10:16 am
by MaineGeezer
It never occurred to me that there was any need to. I radius the braces in the appropriate radius dish,then set the top (or back) in the dish and clamp the braces with go-bar rods, mashing everything down against the dish.
Re: Before gluing braces . . .
Posted: Tue Sep 12, 2023 10:54 am
by Gary Davis
I just remember reading that sanding is not as effective for gluing surfaces as planing or scraping. I would think that that would be an important consideration given the stresses associated with bracing.
Gary Davis
Re: Before gluing braces . . .
Posted: Tue Sep 12, 2023 1:42 pm
by MaineGeezer
Gary Davis wrote: ↑Tue Sep 12, 2023 10:54 am
I just remember reading that sanding is not as effective for gluing surfaces as planing or scraping.
Hmm...that's interesting. I would have assumed that a sanded surface would provide a better grip for glue than a planed one.
Re: Before gluing braces . . .
Posted: Tue Sep 12, 2023 3:25 pm
by rcnewcomb
I wanted to check Gary's statement about glue and sanding vs planing/scraping. There was a discussion on a classical guitar forum on this topic. ->
Link
Apparently the research comes from the aircraft industry in the early 1940's using the waterproof glue Resorcinol. I have no idea if these findings would apply to Titebond original.
The other finding is that gluing freshly sanded/machined surfaces have a lower failure rate than surfaces that have had more time between sanding and then the glue process. I wasn't familiar with the concept of
surface energy, but it does make sense.