|
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | My laser cutting guy was able to turn around the order very quickly. I got the parts today. 
I popped the parts (cut out, really) out of the carrier sheets and did a dry-run assembly of the 'table' base parts.
This next pic shows the 1-1/2 degree angle of the 'table' top. 
I slid the neck base into place. 
Put the 'table' top onto the base.
Placed the doublers/heat shield bases. The nomex paper strip will be glued to the inside lip of the doublers.
Here's the basic idea of how it will (should?) work. The guitar will rest on the 'table' and the neck base.
The neck base will be screwed to the work bench.
The neck caul will be put into place.
Then, the clamping plate will be screwed down to the work bench. This will pull the neck down and cause the bowl to warp away from the neck to the 1-1/2 degrees needed to bring the neck back in-line with the bridge. Once the neck is clamped, then it's time to apply the heat to re-shape (warp/bend) the bowl.
So far, so good. Next up is to break out the gobar deck, then glue the table together in preparation for the bowl bend. Pics to follow.
|
|
| |
|
Joined:
October 2012
Posts: 1018
Location: Yokohama, Japan | Wow, that was quick! Laser cutting and CNC routing make wood working so much easier nowadays. Immaculate planning and preparation DanSavage! Will bowl bends work on old hand laid fiberglass bowls as well as new molded bowls? Once the bowl bend is complete, how long does it take to cool off and set into its new position permanently? Don't mean to pester you with questions, but this is really interesting stuff!
Edited by arumako 2014-11-06 6:44 AM
|
|
| |
|
Joined:
August 2007
Posts: 1008
Location: Tuscany, Italy | Dan you are a great source of ideas. Whatever it turns out, it will be a success.
Edited by marenostrum 2014-11-06 11:45 AM
|
|
| |
|
Joined:
January 2014
Posts: 402
Location: Taxed To Death State | Dan, man not only is your work, your home made jigs, fixtures, and ingenuity amazing, your attention to detail in writing these posts is incredible. Doing an extensive rebuild like this is engineering art, and your posts are no less impressive. I dream of having the time and patience you have. Kudos Dan. Just f'n awsome stuff. |
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | Hi Arumako,
Yeah, I wasn't expecting to get the parts until the end of this week or the beginning of next week. Sometimes he's able to squeeze these little jobs in.
Fiberglass resin is plastic. Not the same type of plastic as say, ABS or polystyrene, but it's still plastic. And all plastics can be made to deform with heat. So, in theory, both old hand-laid bowls and the SMC bowls can be deformed.
The hand-laid bowls are probably trickier because they're thinner and heat up more quickly which makes it easier to overshoot the maximum temperature. The TG or translation temperature (basically, the temperature at which the resin softens) on resin depends on the maximum temperature used during the curing process. The higher the curing temperature, the more heat-resistant the part.
Room-temperature curing usually results in a TG temperature of around 160-180 degrees. SMC bowls are formed in molds heated to 300-degrees. Naturally, the SMC bowl would require higher temps than a hand-laid, room-temp cured bowl.
Since this guitar is hand-laid cloth that's been vacuum-bagged, there's a minimum of resin. This means that I'll need to be very careful and monitor the temperature of the bowl very closely to prevent overheating the resin.
Cooling times will vary, but generally the part only needs to cool to room temperature for the resin to take the new set. There is a little spring-back, but I'm planning to leave the guitar in the jig for 24 hours or so just to make sure the resin takes the new set. If it springs back too far, then I'l try another shot. I don't want to attempt this too many times because I'm afraid of crystallizing the resin.
Luckily, I've got a small piece of molded fiberglass used as a reinforcement of the A-braces on my 1617. I'm going to pop that off the braces, then experiment with that before going after 485's bowl. This should give me a good idea of what kind of temperature and what effect the heat has on the molded part.
Dan
arumako - 2014-11-06 4:38 AM
Wow, that was quick! Laser cutting and CNC routing make wood working so much easier nowadays. Immaculate planning and preparation DanSavage! Will bowl bends work on old hand laid fiberglass bowls as well as new molded bowls? Once the bowl bend is complete, how long does it take to cool off and set into its new position permanently? Don't mean to pester you with questions, but this is really interesting stuff! |
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | Thanks, Riccardo.
I'll consider it a success if when I'm done I'm able to send back to Jay, a nice sounding, nice playing, nice looking guitar. 
Dan
maremagnum - 2014-11-06 9:42 AM
Dan you are a great source of ideas. Whatever it turns out, it will be a success. |
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | Thanks, for the kind words, Dan. :D
danomyte - 2014-11-06 11:56 AM
Dan, man not only is your work, your home made jigs, fixtures, and ingenuity amazing, your attention to detail in writing these posts is incredible. Doing an extensive rebuild like this is engineering art, and your posts are no less impressive. I dream of having the time and patience you have. Kudos Dan. Just f'n awsome stuff. |
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | It's been a few weeks since my last post.
First job was to assemble the table top. I used tape as the 'hinge' to keep the two halves in alignment.
Fold the halves back to expose the joint, then run a bead of medium CA.
Remove the 'hinge', then use go-bars to secure it to the deck.
Assemble and align the lattice and use more go-bars to keep them in place. Once everything aligned, I ran a bead of medium CA along each side of the lattice and top joints. I used ZIP kicker to speed up the process. 
After all the glue joints were kicked, I laid the deck on each side so I could glue the lattice joints for extra strength.
The glue is dry and I pulled the table off the deck. Next task is to assemble the 1" wide nomex cloth heat shield to the 1/4" birch ply frame. I sprayed kicker on the cloth, then applied a bead of medium CA to the frame and pressed the cloth strip. When the two parts are pressed together the glue dries in a few seconds. Repeat for the other side.
My measurements were off slightly, so I omitted the bottom plate and just used the neck caul and top clamping plate. To speed the process and assure accurate alignment of the top clamp plate I drilled pilot holes in the workbench and drew alignment marks using a Sharpie.
Before clamping, the gap between the kerfing and the table top was about 1/4".
The screws are tightened to pull body down to the table top.
 
The heat shields were clamped into place and an extra strip was used to protect the neck to body joint. These were only used during the first heating session. I actually found I didn't need to use the heat shields, so these were omitted during later heating sessions.
Break out my handy-dandy heat gun and IR thermometer. As you can see, ambient temp was 72.3° F. 
Before any heating the neck geometry is about 1/4" or so below the top of the bridge.
It took several heating/cooling sessions. I would heat the bowl, let it cool, then pull the screws to check the change. Here we see the neck geometry is about 1/8" below the top of the bridge.
I wasn't sure how hot the fiberglass needed to be, so I started off heating it to about 160° F, which is a safe starting point. I found I was able to make more progress by heating it to higher temps. My biggest fear was overheating the fiberglass and causing it to ripple.
By the end, I was heating it to about 210° F to 230° F. In addition to heating the sides of the upper bout, I also heated up the back up the upper bout.
The neck geometry is now about 1/16" above the top of the bridge. I could have kept going, but this is plenty good, so I think this is a good stopping point.
Next is to start gathering the materials to build a new top. |
|
| |
|
Joined:
January 2009
Posts: 1249
Location: Texas | Nothing but incredibly awesome. So were you suprised that the bowl could take that much heat? Did you guess at the time the bowl needed to be heated, or could you visually gauge movement? |
|
| |
|
Joined:
March 2002
Posts: 15652
Location: SoCal | This is so cool....
|
|
| |
|
Joined:
October 2012
Posts: 1018
Location: Yokohama, Japan | Man, that is good stuff DanSavage! Incredibly thoughtful and informative. 210 to 230 degrees is way up there... this Lyrachord stuff is pretty incredible stuff isn't it? Just awesome! |
|
| |
|
Joined:
March 2005
Posts: 12750
Location: Boise, Idaho | Love it. |
|
| |
|
Joined:
March 2002
Posts: 15652
Location: SoCal | Ok, I've got a couple of questions. First, how is the body of the guitar secured down, or is it? Second, when you heat the bowl, are you slowly applying pressure on the upper bout of the bowl, pushing it down to close the gap between the table and the top, which would push the neck back into proper alignment? Do I have that right?
I'm looking forward to playing this guitar before it goes back to Texas...... |
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | amosmoses - 2014-11-23 7:02 PM
Nothing but incredibly awesome. So were you suprised that the bowl could take that much heat? Did you guess at the time the bowl needed to be heated, or could you visually gauge movement?
Thanks, Jay.
Actually, I had no idea how much heat it was going to take because I didn't know what brand of epoxy was used during the lay-up.
Generally speaking, epoxy used in a room-temperature lay-up has a Tg (glass transition temperature) of about 170° F or so. The Tg represents the temperature where the resin transitions from a solid state to a rubbery state.
The Tg is determined by the initial curing temperature. If you know the piece is going to be used in an environment experiencing elevated temperatures, then you post cure the piece at a temperature of about 30° F higher than what you expect it to be. Post curing is done inside a hot box where the temps are raised a little at a time over the course of several hours up to the max temp, then kept there for a set period, and then brought down gradually so the piece doesn't warp. Post curing is usually done inside the mold, again, so the molded piece doesn't warp. Needless to say, in such cases, the mold is post cured before it's used to lay up any parts.
Some epoxies are so-called high-temp epoxies that can be post cured up to 300°-400° F. That's usually about the limit an epoxy can take. If you want higher temps you need to move to different chemistry of resins.
Getting back to the bowl, I wasn't sure what the Tg would be so I started at 160° F. I also didn't know what how much of the bowl would need to be heated to realign the neck. During the dry runs, I could see the area around the upper bout where the neck joint was warping, but I didn't think just heating this area would have the desired effect.
At first, I clamped the neck, heated up sides of the upper bout, down to the waist area, then let it cool back to ambient temperature. Once it was cooled, I removed the clamps and checked alignment and didn't really see any perceptible change. So, I repeated the cycle raising the temps until I did see an effect.
Once I found that the temp that the glass needed to be heated to effect a permanent change, (~200° F) I just worked to get the areas heated to that temperature.
Rather than attempt to bend the bowl all at once, I effected the changes a little bit at a time. If you look closely at the clamped bowl pic, you can see the top of the bowl is about 1/2" or so from the table top. With each heating/cooling cycle I gradually moved the bowl down the table top to keep increasing the neck angle. By the last cycle the upper bout overhang the table top by about 1/4". |
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | arumako - 2014-11-24 6:15 AM
Man, that is good stuff DanSavage! Incredibly thoughtful and informative. 210 to 230 degrees is way up there... this Lyrachord stuff is pretty incredible stuff isn't it? Just awesome!
Thanks, Arumako.
Like I've said before, Lyrachord is just a name Ovation marketing gave to the fiberglass bowls. By itself, there's nothing special about the fiberglass they used.
The SMC bowls are made from the same materials as Corvette body panels and both use the same heated compression molds to make the parts.
Speaking of Corvettes, it should come as no surprise to anyone what kind of car I drive. 
Edited by DanSavage 2014-11-24 11:28 AM
|
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | immoody - 2014-11-24 8:55 AM
Ok, I've got a couple of questions. First, how is the body of the guitar secured down, or is it? Second, when you heat the bowl, are you slowly applying pressure on the upper bout of the bowl, pushing it down to close the gap between the table and the top, which would push the neck back into proper alignment? Do I have that right?
I'm looking forward to playing this guitar before it goes back to Texas......
The body isn't secured to the 'table', per se. Rather, the table top raises the body above the work bench at a 1-1/2° angle, which is the angle needed to restore the neck geometry.
Clamping the neck down to the workbench pulls the body down into full contact with the angled table.
Because the bowl is flexible, clamping the neck distorts the bowl by the desired amount. Heating it, then cooling it causes the resin to take a new set.
Since I wasn't heating the bowl to fully melt the resin, it retained some 'springiness', which when the pressure was relaxed caused it to pull back a little bit. This springiness is what required several heating/cooling cycles to walk the neck back into alignment.
The last thing I wanted to do overheat the resin and cause the bowl or sides to sag, or worse, potato chip.
Sounds good. Once I get it finished, we'll get together so you can play it. I know I would really like to try your 1537 and/or your 1987 CE, neither of which I've ever played and both of which I would like get an earful.
|
|
| |
|
Joined:
March 2002
Posts: 15652
Location: SoCal | Sounds good Dan. When the factory was up and running, they had one guy in the repair shop who did bowl bends. Don't know if he still does them or how they were done.
|
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | That's interesting to know.
If I were to do this in a production environment, I would use several IR heat lamps instead of a single heat gun.
This would allow the tech to heat a whole area of the bowl at once instead of slowly passing the heat gun over small sections. This would also allow the tech to better control over the temperature. It's pretty easy to overheat a section by lingering too long in one spot. |
|
| |
|
Joined:
March 2002
Posts: 15652
Location: SoCal | Wish you had been able to do this about 10 years ago. I had a 1763 that needed a neck reset and was told the factory couldn't do it. I still miss that guitar.
|
|
| |
|
Joined:
March 2002
Posts: 15652
Location: SoCal | DanSavage - 2014-11-24 9:27 AM
arumako - 2014-11-24 6:15 AM
Man, that is good stuff DanSavage! Incredibly thoughtful and informative. 210 to 230 degrees is way up there... this Lyrachord stuff is pretty incredible stuff isn't it? Just awesome! Thanks, Arumako. Like I've said before, Lyrachord is just a name Ovation marketing gave to the fiberglass bowls. By itself, there's nothing special about the fiberglass they used. The SMC bowls are made from the same materials as Corvette body panels and both use the same heated compression molds to make the parts. Speaking of Corvettes, it should come as no surprise to anyone what kind of car I drive.
It's not a Mustang Bullitt, but not bad regardless...... |
|
| |
|
Joined:
November 2002
Posts: 3599
Location: Pacific Northwest Inland Empire | "It's not a Mustang Bullitt, but not bad regardless......"
Wrong town. That would be Frisco.
Nice work, Dan. The IR lamp scenario would be ideal.
Persevere! |
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | immoody - 2014-11-24 11:03 AM
Wish you had been able to do this about 10 years ago. I had a 1763 that needed a neck reset and was told the factory couldn't do it. I still miss that guitar.
IMO, the bowl bend success would probably be limited to hand-laid bowls. The SMC bowls would require so much heat that the paint on the bowl would bubble and scorch.
|
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | immoody - 2014-11-24 11:04 AM
It's not a Mustang Bullitt, but not bad regardless......
Thanks.
My first car was a 1967 big-block Mustang coupe. (390cid) I really like the 2005-2010 Mustangs because they took a lot of their styling cues from the 1st generation.
I rented a V6 convertible `Stang in 2005 and really liked how it drove. It felt light and nimble and was pretty peppy for a V6.
Then, I rented a Shelby GTH in 2006 and it was really nice, too.
When I was looking to replace my Chevy Astro last year, I seriously considered buying a Mustang convertible. In the end I decided on the Vette, mainly because I wanted a sports car. |
|
| |
|
Joined:
June 2012
Posts: 2303
Location: Lake Forest, CA | seesquare - 2014-11-24 11:35 AM
Nice work, Dan. The IR lamp scenario would be ideal.
Persevere!
Thanks! |
|
| |
|
Joined:
March 2002
Posts: 15652
Location: SoCal | Dan, since 1996, Chevy has been building really great Vettes. Actually I'm not a fan of the new one, or the 2015 Mustang. Too busy looking on both, and I prefer the retro look of the pony. Your model Vette is one of the ones I really like..... |
|
| |
1967 Balladeer Rebuild...
