My flat top top is actually flat. OK?

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Red Dogg
Posts: 26
Joined: Sun Dec 06, 2020 12:46 pm

My flat top top is actually flat. OK?

Post by Red Dogg »

I'm working on a StewMac OM kit and have the braces and tone bars all glued up on the top. According to the instructions, as I understand it, there should be a bit of a "dome" as measured from side to side (across the bouts).

FYI, the braces and bars have a curve pre-milled into them, which I understood would impart that radius to the top. Now I see that the top is quite flat, side to side. From end to end, the top appears to be pretty flat from the neck block to the soundhole, but drops off from there to the tail block.

If I hold a straightedge end to end, tight to the neck end of the top, there is a gap of about 3/8" at the tailblock end. Hope this makes sense.

Also, the sides and kerfing are sanded flat as per the instructions, so I'm wondering how this will all come together.

Is this normal? Ok? Can I live with it? Could this cause problems trying to align the neck & bridge when the time comes?
phavriluk
Posts: 554
Joined: Mon Jul 09, 2012 9:49 pm

Re: My flat top top is actually flat. OK?

Post by phavriluk »

Results can be influenced by assembly technique. Was the top bracing installed while the top was shimmed to conform to the arc of the braces? Or assembled in a radiused dish? Did Stew-Mac mention the radius of the dome? And suggest how to retain it?
peter havriluk
Skarsaune
Posts: 239
Joined: Mon Dec 03, 2018 9:12 am

Re: My flat top top is actually flat. OK?

Post by Skarsaune »

They're glued on now - you can likely live with it.

With the sides/kerfing sanded flat, gluing the top to the sides & clamping all around is going to force it flat anyways.

The end to end curl is a bit more concerning. You don't want to have to force parts together to glue them in position if you can avoid it.
If you set your assembled top on the sides, how much gap do you have?
Note - you will need to cut notches in the kerfing for the brace ends for the top to sit in position. You'll need to do this anyways, so do this then check the fit of the top.
Red Dogg
Posts: 26
Joined: Sun Dec 06, 2020 12:46 pm

Re: My flat top top is actually flat. OK?

Post by Red Dogg »

The instructions said to lay the top onto a flat board and clamp the braces/bars in place, which is what I did. I assumed that the bars, given the radius on their backs would somewhat force the top into the right shape. Wrong!

Now, I've trimmed the bars to their final length and marked the kerfing to be notched. Will do that later today.

Hoping the Guitar Gods are looking over me.
carld05
Posts: 170
Joined: Mon Mar 19, 2012 4:19 pm
Location: Forest Ranch, CA

Re: My flat top top is actually flat. OK?

Post by carld05 »

Here is a link to an article by the late Ken Cierpilowski that describes a way to maintain the arc of the brace while gluing that doesn't require a radiused dish. Too late now but something for your next build. I made several from my old business cards rather than 3x5 cards. http://harvestmoonguitars.com/kennethmi ... rtool.html.
Lots of guitars are made with "flat" tops. You'll be OK with it.
Andy Mitchell
Posts: 58
Joined: Mon Dec 28, 2020 8:54 am

Re: My flat top top is actually flat. OK?

Post by Andy Mitchell »

Red Dogg wrote: Now, I've trimmed the bars to their final length and marked the kerfing to be notched. Will do that later today.
Just a heads-up - make sure you have trimmed the braces down to the thickness specified (0.10" ??) at the ends where they fit in the kerfling... if you cut those slots in the sides too deep you run the risk of the binding they supply not being wide enough to cover the gap.
Diane Kauffmds
Posts: 3246
Joined: Sun Mar 09, 2014 8:13 pm

Re: My flat top top is actually flat. OK?

Post by Diane Kauffmds »

The gap at your tail block is okay. I aim for 1/4" gap. You'll do fine.

If you trim your brace ends too thin, the braces will relax and you'll lose some of your radius. I try to keep them ~ 1/4" thick. When you notch the kerfing for your braces, don't go through the sides; just notch the kerfing. That way, you won't have to worry about whether your binding covers the braces.

There are various ways of gluing curved bracing without a radius dish. I simply used a piece of foam, laid on the bottom of my gobar deck. The foam allowed enough cushioning to maintain the radius. You can buy it at Walmart or fabric stores.

You do want a radius on your sides and kerfing, because if you don't have it radiused, you're in effect flattening a curve, which stresses the top and back. You're also limiting your gluing area. You don't have to have a dish. You can make a simple radius bar. If you search the forum, you'll see how this works.
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Diane Kauffmann
Country Roads Guitars
countryroadsguitars@gmail.com
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