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Double-top glue ups
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=19285		 Page 1 of 1
Author:  ClintB [ Wed Oct 22, 2008 2:11 pm ]
Post subject:  Double-top glue ups
This question is for anyone who has some experience building nomex-cored double top guitars. I'm planning to give this style a go for my next build, but the only qualm I have is with using 2 layers of epoxy on my tops to pull it off. I know that properly done, the epoxy should only be applied to the honeycomb (i.e. you don't spread it over the entire surface of the spruce pieces).

What I'm wondering is if anyone has tried using other, more acoustically transparent beehive , glues. Would fish glue work (and is it thought to be acoustically transparent like HHG or LMI white)?

Any input would be appreciated.

Thanks in advance.

-Clint
Author:  Jim Watts [ Wed Oct 22, 2008 2:40 pm ]
Post subject:  Re: Double-top glue ups
Clint, I cant respond to "other glues" than epoxy as that's what I use on my double tops. However I can tell you that you need to have a fillet form between the core wall and the skin for a good bond. System 3's T-88 seems to work well and I'm sure that the West System stuff would also work, but you'd probably have to play with the viscosity some, as this helps to control its fillet forming ability.
Fish glue may actually be worth trying on a scrap lay up also. Is fish glues only draw back its cure time?
I believe some have also tried the urethane glues, but I don't really know how well it works.
Good luck!
Author:  Mike Collins [ Wed Oct 22, 2008 2:53 pm ]
Post subject:  Re: Double-top glue ups
Randy Reynolds builds some incredible double tops!
He's approachable !


He did a great layout for the GAL about a year or so ago!
Check their back issues!!!
That's what Randy will probalby tell ya also!!!!

http://www.reynoldsguitars.com

Mike [clap]
Author:  ClintB [ Wed Oct 22, 2008 5:06 pm ]
Post subject:  Re: Double-top glue ups
Thanks for the replies, guys!

Jim, the need for the proper viscosity for fillets makes sense to me. I guess that means that whatever I use needs to be very strong when built up thicker. That's probably why I've never heard of anyone using anything but epoxy. I imagine most adhesives simply wouldn't be strong enough.

I guess epoxy just intimidates me a little because I've never really used it (except for the 5 min. stuff the odd time). The appeal of fish glue or LMI white to me was primarily that they seem more manageable to me in my mind. I know fish glue is very strong for wood to wood, but I have no idea how a fillet would perform in holding things together under tension. It will weaken if exposed to excessive moisture, but I can't imagine that would ever happen inside the top. Maybe I'll still try a few adhesives out on scraps when the time comes, but I suppose I'll find the epoxy necessary.

Mike, Randy's instruments were actually what got me thinking about double tops in the first place a year or two ago. Maybe I'll ask him if he's tried any alternatives.

Thanks again! [:Y:]
Author:  Martin Turner [ Thu Oct 23, 2008 3:04 am ]
Post subject:  Re: Double-top glue ups
I second that....this article is a must read if youre into double tops.


Mike Collins wrote:
Randy Reynolds builds some incredible double tops!
He's approachable !


He did a great layout for the GAL about a year or so ago!
Check their back issues!!!
That's what Randy will probalby tell ya also!!!!

http://www.reynoldsguitars.com

Mike [clap]
Author:  Brook Moore [ Thu Oct 23, 2008 9:18 am ]
Post subject:  Re: Double-top glue ups
I have made several double-tops with epoxy, using West 105/205. In my opinion, the glue application is the trickiest part of the process: it is easy to use too much and end up with a heavy top. In trying to use as little glue as possible, it is also easy to end up with inadequately glued honeycomb, which is a lurking disaster. I strongly suggest that you refine your process with several tops made of inexpensive materials.

I have now made one double-top with polyurethane glue, the newer Gorilla version. I found it much easier to control the process, and the Gorilla seems to glue well with a smaller quantity than epoxy. I can't give a long term report on this glue yet.

I prefer the 3-piece method over the routed out 2-piece method.

Finally, I believe that the honeycomb sold by LMI is better suited to classical guitars and that if you are building steel strings, a stronger honeycomb is desirable. YMMV.

Good luck,
Brook
Author:  ClintB [ Thu Oct 23, 2008 11:49 am ]
Post subject:  Re: Double-top glue ups
Thanks, Brook.

I think I'll give a few methods a try on scraps first, including the gorilla glue. I'm going to go with the 3 piece method as well. I really want to avoid a heavy top (sort of defeats the purpose for my going to a double-top).

What honeycomb spacing do you recommend for Steel strings? I was thinking of using 3/16" on classicals (.060" thick) and maybe 1/8" on the steels.

I was planning on ordering from Aerospace Composite Products. I think I found a link to them on Randy Reynolds site, or maybe it was Fritz Mueller's.

Again, thanks to all you guys for your help.

-Clint
Author:  Brook Moore [ Thu Oct 23, 2008 7:11 pm ]
Post subject:  Re: Double-top glue ups
For steel strings, I like the ACP 1/8" 3 lb honeycomb. As it comes in .125" thickness, you will need to sand it down to whatever thickness you want to experiment with. I am sure there are others that have more experience than I do with this process, and may have different opinions.
Author:  RaymundH [ Fri Oct 24, 2008 8:39 am ]
Post subject:  Re: Double-top glue ups
To see a nice tutorial go to www.dunwellguitar.com and click on "Luthier Pages."

If you have a question or two Alan is very approachable via e-mail.
Author:  ClintB [ Fri Oct 24, 2008 9:30 am ]
Post subject:  Re: Double-top glue ups
Filippo,

I've looked for the GAL article and came up empty. Does he state specifically what thickness of nomex, and the cell spacing, that he is using? I didn't see this on his website, just a note that it typically comes in 1/8 or 3/16, and that he finds one works better than the others.

Raymond,

I've been to his site in the past, and yes, it is quite a detailed tute, isn't it?

Thanks,

Clint
Author:  KenH [ Fri Oct 24, 2008 4:21 pm ]
Post subject:  Re: Double-top glue ups
I dont mean to sidetrack this thread, but I have wondered if anybody has tried other materials instead of nomex? I recently saw something very similar in texture made with kevlar and have wondered if the epoxy would be enough to bind these together as well as the nomex? Another thought is about the strength of using fiberglass or kevlar or other materials and its sonic properties.

any thoughts?
Author:  Brad Way [ Fri Oct 24, 2008 5:05 pm ]
Post subject:  Re: Double-top glue ups
Ken Hodges wrote:
I dont mean to sidetrack this thread, but I have wondered if anybody has tried other materials instead of nomex? I recently saw something very similar in texture made with kevlar and have wondered if the epoxy would be enough to bind these together as well as the nomex? Another thought is about the strength of using fiberglass or kevlar or other materials and its sonic properties.

any thoughts?


Ken....I was thinking about this same topic. Anyone have any thoughts?
Author:  peterm [ Fri Oct 24, 2008 6:28 pm ]
Post subject:  Re: Double-top glue ups
I build all my double tops with an all wood inner core. The core is hollowed out and then glued with epoxy in a vacuum fixture. I have used aliphatic resin to glue them up but now have switched to high-strength epoxy.
Author:  ClintB [ Fri Oct 24, 2008 6:28 pm ]
Post subject:  Re: Double-top glue ups
I've thought about it too, Ken. At least at first I'm going to stick with the nomex just because it's known to be able to produce great instruments (although, like anything, I'm sure it depends largely on the individual builder). I've seen the stuff you're talking about (I think). I'll maybe order a small sample when I get the nomex as I'm planning on gluing up a few scraps to be sure I've got the proper adhesion happening.

I'd be interested to see if it's much stiffer than an equal build-up of the nomex. And of course I'm interested to see how it would differ to the ear as well.

-Clint
Author:  ClintB [ Fri Oct 24, 2008 11:04 pm ]
Post subject:  Re: Double-top glue ups
Thanks a lot, Filippo. That really helps. That's the size I was leaning towards, but it's hard to know if you're on the right track or not when you've never worked with it.

I'd love to play one of his classicals someday. I've never heard anything but great reviews, and they just look so... classy.

-Clint
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