MIMF

Hi everyone, I'm at the preliminary steps of building a Double top Arch Top & would like some opinions on bracing.
I've watched the Steve Andersen video W/ Bill Frisell playing several times & wish to achieve more bass. I have no Idea
if bracing will even be required. My plans are for a 17" body & a 24.9 scale.

http://www.fretboardjournal.com/video/s ... op-archtop

I don't think anyone really knows. There isn't much on Andersen's site on his double tops. I wonder if he still makes them. I've experimented with about a dozen different composite configurations. Parallel, x, and even no bracing. I'm still not sure what I like best. You are also not limited to the 0.060 nomex. Just because classical builders use it doesn't mean that is the best for archtops. Do you need bracing if you use 0.125 Nomex? (Hint, I don't thin so). Of course I haven't been making composite top archtops long enough to know how they will do with twenty or thirty years of down force.

Wow, What a treat to talk with someone who has actually built some. You just pointed the way out of the box. Andersen's approach is to use 1MM top & bott. skin w/ a 2MM core so thanks for the .125 option.
I assume you used a Vacuum bag, However I've been considering a modified Go-Bar deck & a large inflatable rubber ball - am I nuts ?

Thanks for the help...Information is freedom

Robert Freemond wrote: I assume you used a Vacuum bag, However I've been considering a modified Go-Bar deck & a large inflatable rubber ball - am I nuts ?

You may be....

Seriously, delamination is a real possibility. There is not much glue surface between the nomex and your skins. I would think you want to be sure of good consistent pressure. An unexpected bubble where the laminate wasn't pressed tight may be disasterous. Again, not enough experience on this probably anywhere for absolutes. But after the experiments I've done, I don't think I would use anything but a vaccum bag or table.

OK, So now I have to consider a vacuum system. I'm Reluctant to get in too deep at this point, but I'm sure there's a way.
Would you mind telling me what you think a minimum PSI should be & also Would you use a somewhat flatter arch ?
I have a mold that I've been using for steamed tops, but because of spring back I made it taller.

I just use a venturi system from Joe Woodworker and my existing compressor. A couple of hundred bucks all in. Not a huge commitment, and super useful for all your friends looking for a 335 clone!

I bring the bag to 24" because I can, not sure it is really that necessary. I think that is about 12psi. That is a ton of weight! (Sorry, couldn't resist the joke. 12psi x 200sq.in. is about 2000lbs). My guess is that for epoxy glue that is probably more than is necessary by an order of magnitude. Don't know for sure. Mostly I think what is useful is the way the bag conforms to the mold and the top. If you really don't want to use a vacuum bag, try a 50lb bag of sand from Home Depot. Put it in smaller bags so that it can spread out and conform to the top. That would work best with a female mold, not a male plug.

I use a standard .75" arch because it makes figuring the neck angle easy and standard. Would changing the height affect the sound? Probably. Too many different variables to test them all, so I try to keep everything I can as close to "standard" measurements when I do experiments.

You wont see much "spring back" in a composite top. Veneer is not going to move like a 1/4" thick piece of wood, and the core material doesn't want to move in the same way as wood. In the end, it is hard for me to tell since I'm putting 20-30lbs of down force on the bridge. That has WAY more impact than some spring back of veneer.

I have in the past steamed spruce and bent and glued in layers for my arch top as well.
I would like to try a double top or even a carbon fiber/spruce laminate?
My sides are 2 cherry1mm thick with carbon in between, the bindings are bent cherry and carbon as well, very stiff.
I'm guessing Anderson has bracing as well, maybe more for tuning?

I too am glad to hear of others willing to share this information.
I am about ready to order the nomex for my 16.25 lower bout arch top.
I am hoping that a bridge plate is not necessary, just the nomex.
Does changing the Nomex thickness change the tone? Or is just about stiffness?
Any favorite sources of suppliers?

Hello Eldon, How are you doing? Glad to see you made it over here, welcome to the MIMForum!

Well it's good to be welcomed in.
We've been out West for a while, but now were back home. Stopped by at Rockford brewery tonight and even played a few songs.
David and Lee are such good host.

Yes they are! I'll be stopping by there soon, I have a featured spot near the holiday so maybe we can catch up!!

What about the center joint? I have been using hide glue for this.
What glue could we use for the flexible joint? What if it needs to be steamed?

Are you going to the Luthier's Concert Eldon?

Yes, I'll have a couple projects at my dads table.

Great! I'll see you there. I think I'll take some photos, and post them here with a little background.

Thinking of flying braces?
Mostly to reduce neck rotation over time.
The Nomex top is installed and seems to be quite stiff.
I'm thinking of very light X bracing with the center of the x to be
north of bridge to reduce mass in the lower bout and bridge area?
The sound hole is in the upper bout top and side.

Hi Eldon! We should talk about this sometime. So, the top is installed before you braced it? I think your ideas for bracing type are just fine. I use flying butresses in that guitar you see me play all the time.

Mark, I'll bring in what I have done on Tuesday night.

I brought the low E string up to 440 pitch and the Nomex top lowered about .5 mm with no bracing and has not changed for 48 hours.
I don't know to expect for drop with a 3/4" nomex archtop?

Sounds great! I'd like to see it!

Hey mark, My original question was about Bracing, so I guess Bracing up old friendships
would qualify.
but every time you contact Eldon you also contact me. I think i should be eliminated from this conversation.
Peace...Robert