Washboarding on Top

The Achilles' Heel of Luthiery
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SColumbusSt
Posts: 11
Joined: Thu Apr 22, 2021 3:52 pm

Washboarding on Top

Post by SColumbusSt »

I'm not sure I'm using the right terminology but there is what looks like washboarding in a few areas on the top of my first build. It was somewhat evident prior to finishing but really obvious at a certain angle now that I've french polished it. I thought the finish would fill the ridges but it only made them more noticeable.

As this is my first build I'm not too concerned about it and it kind of just looks like pick wear (I'm going to claim it's reliced to a level 1.5 like those popular PreWar guitars) but would like to prevent it on future builds. Did I just need to sand the top more aggressively in those areas? I went after them pretty hard and it did not seem to have any effect on the ridges and I was worried about thinning the top too much. Is there some type of pore filler you can use on a top? Thanks for your help.

Keith
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jread
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Re: Washboarding on Top

Post by jread »

It looks like the same issue I had with my last build. I had the drum sander paper fall apart mid run and it seemed to rake into the top and make the same kind of ripples that seemingly would not sand out.

Like you, I just french polished it but it wasn't gonna fly. I could feel them. I ended up sanding the top completely bare with big sanding blocks and worked that area especially. It did go away and I didn't over-thin my top, luckily.

This is just my opinion on a similar effect I had. Not sure if it relates to yours. Others may have a more trained eye.
tippie53
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Re: Washboarding on Top

Post by tippie53 »

finish is about technique and product. Now if this is something that just showed up you may have humidit
if this is what you had from the start I bet and this sounds so counter to what we have been told
DO NOT SAND WITH THE GRAIN ON THE TOP.
Also how are you sanding

MY MO is simple I use a ROS and start with 120 180 STOP !
seal ( 2 coats ) finish on top


you will always have some grain movement because of RH changes but that is normal
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
SColumbusSt
Posts: 11
Joined: Thu Apr 22, 2021 3:52 pm

Re: Washboarding on Top

Post by SColumbusSt »

Thanks for the replies. John, the top was like this when I got it from stewmac as part of my kit. I noticed it and tried to sand it out with no luck. I used a sanding sponge as a backer and started with 150 grit and moved to 220 grit on the top per the stew mac instructions. I did not go crazy with the sanding because I was worried about thinning the top too much.

I've done the majority of the build over the winter and the Rh has been around 40. Just recently it has started to bump up but I am running a dehumidifier to keep it as close to 50 as possible.

What is a ROS?

Keith
tippie53
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Re: Washboarding on Top

Post by tippie53 »

ROS Randon Orbital Sander
sanding I like a firm block
I use plywood with foam pipe insulation
John Hall
Blues Creek Guitars Inc
Authorized CF Martin Repair Center
president of Association of Stringed Instrument Artisans
http://www.bluescreekguitars.com
jread
Posts: 560
Joined: Wed Feb 13, 2019 9:52 am
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Re: Washboarding on Top

Post by jread »

Thanks John H! I was afraid to mention that I found success by sanding cross grain on spruce with the rough grits. I was afraid you would all laugh at me.. :D This forum is really great.
SColumbusSt
Posts: 11
Joined: Thu Apr 22, 2021 3:52 pm

Re: Washboarding on Top

Post by SColumbusSt »

I think I figured out the source of the washboarding and wanted to share in case anyone else found themselves with this problem. As it symmetrically frames either side of the soundhole and is found nowhere else on the top my now guess is it was caused when I used a scraper to bring the rosette flush with the top. This was one of the first things I did on the build so probably why I thought the washboarding had always been there. By springing the scraper I dug into the top on either side at the corners of the scraper.

An ROS is in my future for my next build.

Keith
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