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PostPosted: Wed Apr 22, 2020 6:11 am 
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Brazilian Rosewood
Brazilian Rosewood
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Joined: Mon Jul 27, 2015 8:21 am
Posts: 2071
First name: Brad
Last Name: Combs
Focus: Build
Status: Amateur
Hello,

I’m working on a tenor uke, it’s the one in the build thread next door. :) I wanted to start a separate thread and ask for help. Somethjng strange has happened and it’s the first time I’ve seen this.

The details:
- Adi top from LMI (currently at 2.1 mm)
- Sitka bracing
- Rosewood bridge plate (1.25 mm thick)
- Upper transverse is put on flat
- Braces put on at 30’ radius
- Bridge plate was flat, now radius to 30’ (details on that below)

I first braced everything up with the UT and bridge plate flat, and the remaining braces at 30’. This is the first time I’ve used a bridge plate that is not spruce. After taking it out of the go-bar deck the two outside fan braces were telegraphing through the top very clearly. There was a very distinct line along the outside edge of each of the braces and the “wings” of the lower bout were curled up.

I thought it was perhaps the flat bridge plate. It never mattered with spruce but I thought the rosewood being harder might be forcing the top to distort somehow. So I took the fans and bridge plate back off (glad I used hide here :)) and remade the bridge plate this time putting a radius on it in the dish. I glued on the new bridge plate.

I haven’t put the fan braces back on yet. The edges of the top are still curled up. Not quite as much as before but it’s noticeable when running my hand across the top, there is a distinct line where the outside fan braces used to be. Here are a couple pics:

Image

Image

A couple questions:

1) Any ideas what is going on here? Humidity is constant at 43-46% in this space.

2) Should I consider widening the splay of the fans to try to “go across” the previous locations to try to get it to lay down?

Other ideas?

Thanks!
Brad


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PostPosted: Wed Apr 22, 2020 10:51 am 
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Contributing Member
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Joined: Mon Aug 23, 2010 11:42 pm
Posts: 1582
First name: John
Last Name: Parchem
City: Seattle
State: Wa
Zip/Postal Code: 98177
Country: USA
Focus: Build
Status: Amateur
That curl would not bother me in the least, especially as it is in the good direction. I would brace as normal, between the braces and the rims the top will happily lie flat. My very uneducated guess is the heat to remove the bridge plate dried out the brace side of the top more than the string side.

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These users thanked the author johnparchem for the post: bcombs510 (Wed Apr 22, 2020 10:58 am)
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PostPosted: Wed Apr 22, 2020 11:54 am 
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Brazilian Rosewood
Brazilian Rosewood
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Joined: Mon Jul 27, 2015 8:21 am
Posts: 2071
First name: Brad
Last Name: Combs
Focus: Build
Status: Amateur
Thanks, John. That's good feedback. I'm going to push ahead after work and (re)brace the top fan braces. I'm hoping to close the box tomorrow morning so I can work on binding this weekend. :)

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