Official Luthiers Forum!

I posted briefly about this guitar a few weeks ago when it arrived in my shop. I spent a week or two deciding on how to approach the repair and completed the job today. I hadn’t found much information about fixing these models of Ovation online so I thought I’d document my process in case it could help someone in the future.

This Adamas 1597 arrived in the shop with the top separated from the bowl, from one side of the next extension all the way around to the other. Prior to arrival in my shop it spent a year in the shop of another repair guy without much progress being made. Eventually the owner took it back and asked me if I’d like to take a shot.

The top on these models are a thin laminate of carbon fiber and veneer. The bowl is the usual Ovation fibreglass yacht hull. The top was loose but the binding remained glued to the bowl:



It looked to me like the neck and fingerboard extension were the only thing keeping the top in place. Gentle heat easily released the FB extension. Undoing the two neck bolts was all it took for separation to be total.



The underside of the FB extension (and the portion of the top it was glued to) were kinda funky, with a hunk of (presumably not factory) wooden shim and a thick buildup of epoxy on the top - a build up at least 1/16” higher than the top finish itself. The neck looks to have been on and off a few times.




The top seemed to have almost no residue of any adhesive on it - the sole exception was a few inches near the tail with some thick gobs of rubbery stuff that looked like it came from a prior repair. The rest of the top was as clean as a whistle. The fibreglass linings in the bowl sported a layer of what I presumed was epoxy - it clearly showed the indentation of the weave from the carbon fibre top:



I’m slicing away an extra fillet of epoxy here as part of the cleanup but the shot shows the “weave” pattern in the epoxy.

The epoxy itself was incredibly soft and rubbery. Clearly it had totally lost what grip it once had on the top, and even it’s bond to the linings was tenuous - it scraped off cleanly without much effort:



I really don’t know why such a total glue failure occurred - a factory error in epoxy mix ratio? Exposure to extreme environmental conditions? Surface contamination on the top?

Getting good adhesion was going to be key. I spent some more time re-scraping things to get the lining surface as clean as possible. I roughened it slightly with coarse sandpaper and washed both it and the underside of the soundboard down with a strong detergent to get rid of any residual amines or waxyness.

To glue up I chose a high strength boat-builder’s epoxy. My main concern was dealing with squeeze out and the difficulty of keeping the finished exterior surfaces clean of epoxy residue during the glue up. I didn’t want goobers of epoxy running everywhere inside the bowl either.

The top itself would not drop directly back into its original location on the bowl without some internal pressure to manipulate the rim outwards - but push it just right and top would pop back into place and be held there tightly, with the binding squeezing it from the outside. This greatly simplified matters.

I decided to thicken the epoxy and try to apply just the right amount so I could pop the top back into place and have it sitting down on a thick bed of the stuff. My aim was to get the top held tightly by the bowl itself, in firm contact with the epoxy layer, without the need for any additional clamping which could cause squeeze out. I went with a slow hardener to give 60 minutes of working time, mainly to give me plenty of time to clean up. I thickened the glue to about the viscosity of soft-serve ice cream with a high-strength filler designed for structural applications.




I masked off the sides and top, gloved up, spread the glue and changed gloves before handling the top. I popped the top in and peeled back the masking tape. There were a few tiny beads of squeeze out to deal with but in general things were neat. The next 20 minutes were spent wiping with soap and water and lots of clean rags as insurance against any tiny smears that might manifest themselves once things had cured. I set the guitar aside for 24 hours.

The next day I scraped the area of the top where the FB extension would lie clean of epoxy buildup, fashioned a wedge to go between FB and top for correct geometry, bolted the neck up and glued the FB extension down with a little fresh epoxy.




Some strings and a setup later and she’s back in action. Geometry is good and this thing can play cleanly with action at 3/64ths and 5/64ths





Fingers crossed the top stays on for good this time round!

Nice job! I still hope I don’t see any more of those in my shop! And thanks for documenting your process- just in case.

_________________
Steve Smith
"Music is what feelings sound like"

Well done, Josh - you're a braver man than I am.

I'm now wondering that kind of temperatures and humidity combined to get that vaunted Ovation aircraft grade epoxy to let go? Very strange.

_________________
"Act your age, not your shoe size" - Prince

Thanks fellas. Yes its an odd failure … I’m stumped but I’d guess some kind of heat exposure must be involved somewhere. And of course it’s humid here. In theory this boat epoxy should be more resistant to both heat and humidity. Time will tell, I suppose.

I should note that, a year or so prior to the top failure, the decorative soundhole leaf things had also fallen off and been reglued by someone…

The main lesson from the job so far is that my estimate for the customer was a trifle low. I didn’t lose my shirt but I’ll bid higher if another one of these comes through the door in future.

I've found that when they suck in their breath..... THAT'S the price you want to quote.

_________________
"Act your age, not your shoe size" - Prince

So, what is the name of that bracing variant? I would call it "Random bracing" or maybe "Don't care bracing"

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

No idea what they call it, and it would be disastrous on a traditional soundboard but I think it makes at least some sense for a cf soundboard that is more or less equally stiff in every direction, sitting on a fibreglass bowl. There is no bellying or bridge rotation with 12-54s. This, at least, makes it very predictable to set up. The braces get taller towards the neck, which makes things stiffest under the FB extension - that’s necessary as there’s no neck block like a traditional guitar.

Volume is good and tone is… ok. You might even call it good if you’re looking for a very even, non-dynamic, flat sound because you’ll use the instrument amplified as a strummer and you want it to sit in a mix. The fact that it has an XLR output even saves the curmudgeonly sound guy from having to break out a DI box. I spent enough time driving around in a beat up econoline full of gear that I can see there is some utility there.

Good going Josh you done good man and you should be very proud!

Thanks for saving yet another guitar my friend.

Thanks Hesh, appreciate it. It was definitely gratifying to get a result on this one.

Only about 170° or so.

A hot car can easily reach these kinds of temperatures.


Most epoxies that are cured at room temperature with no post-cure schedules have a glass-transition (Tg) temperatures around 170° or so. A few, such as Hysol 9462 are able to withstand temperatures as high as 250°, but these aren't really suitable for guitar work.


It's called Quintad bracing. When Kaman was developing the Adamas line of guitars, he tested several brace patterns using a laser interferometer. He found that the strings cause the guitar top to 'twist.' Traditional patterns such as the X-braces resist this twisting action and inhibit sound output. This led him to develop this brace pattern and allows the top to twist more freely. Taylor Guitars' Andy Powers' V-Class braces also allow the top to 'twist' or rotate more freely for more volume, longer sustain and better balance between bass and treble strings.


This brace pattern was modified slightly and used on the Ovation Elite series of guitars which use wood tops. It works just fine. In fact, I've re-topped an Elite-style Ovation using torrefied Sitka spruce and it sounds pretty spectacular, even when played purely acoustic. Early Ovations, including the Adamas and Elites used traditional wood neck blocks. It wasn't until 1982 when the SMC bowls were adopted that Ovation did away with the traditional wood neck blocks. The SMC bowls still a neck block, but it was molded into the bowl instead of being glued on after the bowl was molded.

When Ovation developed the Custom Legend, they modified the Quintad braces to work with a center sound hole and called that new brace pattern the A-braces. Taylor's V-Class bracing follows the same principles as the Quintad-braces and later A-braces

Here's the Ovation A-braces:



Here's the Taylor V-Class braces:

So, there is a method to the madness after all. I guess I let loose my inner hate for Ovation guitars, sorry about that.

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

Roger, don't apologize for what is a legit opinion of these atrocities. I don't allow them anywhere near me.

My usual recommendation is to casually drop an anvil on Ovations.

_________________
"Act your age, not your shoe size" - Prince