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| "level" sanding on a concave surface http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10137&t=56796 |
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| Author: | Melt in the Sun [ Fri Sep 20, 2024 1:06 pm ] |
| Post subject: | "level" sanding on a concave surface |
Hi again, got another quick finish question. This mandolin was left too close to a fireplace for a few hours in 2004, and developed a crack on the backside of the scroll. It didn't change in many subsequent years, then probably 10 years ago I clumsily filled it with medium CYA. The finish is THICK poly. I'm fixing this thing up to sell it (value ~4-500) and am wondering how I might scrape/sand this level given that it's on a concave part of the body. Or, am I again in "don't bother, not worth it" territory? |
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| Author: | Kbore [ Fri Sep 20, 2024 2:39 pm ] |
| Post subject: | Re: "level" sanding on a concave surface |
I'm not a professional or even semi, but I've had really good outcomes fixing finish defects using this system: Tolecut Kit - 8-Cut, PSA Sanding Sheets for Nibs, Runs and Imperfections, SP9738, K800 - K3000, 6 Sheets + 2 Toleblocks https://a.co/d/4s6TDyE Hard to describe just how well this Tolecut system works for small finish repairs (I've done a LOT of finish repairs on my own builds). GluBoost Fill and Finish, applied with the end of a .011 guitar string, many iterations, with a scuff between to see the lay of land (high spots mostly). One thing the GLuBoost guy told me: light spritz of accelerator BEFORE and AFTER application of GLuBoost because GLuBoost has plasticizers in it that extend the cure time dramatically, without accelerator coming in from BOTH sides (top AND bottom). Experiment with adding small amount of black TransTint dye to the CA. Regular CA doesn't much like dye (dye causes it to start to cure) but GLuBoost seems to take it better without curing from the dye addition. Hopefully this will kick off some comments from more experienced members...... |
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| Author: | profchris [ Sat Sep 21, 2024 10:52 am ] |
| Post subject: | Re: "level" sanding on a concave surface |
I cut a wine cork in half lengthways as a sanding block for curves. I use the flat side too for small flat areas |
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| Author: | phavriluk [ Sat Sep 21, 2024 1:50 pm ] |
| Post subject: | Re: "level" sanding on a concave surface |
This is the sort of problem that gets all kinds of attention, a great deal of it contradictory. Here's my take: Leave it alone and sell it as-is. Nothing but a professional repair is going to do more than emphasize that the person doing the repair shouldn't have tried. |
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| Author: | Jim Watts [ Sat Sep 21, 2024 3:16 pm ] |
| Post subject: | Re: "level" sanding on a concave surface |
you can level it out with a curved scraper. Then polish. |
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| Author: | Barry Daniels [ Sat Sep 21, 2024 3:36 pm ] |
| Post subject: | Re: "level" sanding on a concave surface |
I use the Tolecut stuck on a fingertip to sand concave areas. You could also make a custom sanding caul by placing a piece of sandpaper in this area faceup and shaping a cork block (or wine cork) to fit. |
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| Author: | Melt in the Sun [ Mon Sep 23, 2024 11:42 am ] |
| Post subject: | Re: "level" sanding on a concave surface |
Sweet bunch of ideas - thanks all! |
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| Author: | Melt in the Sun [ Fri Oct 18, 2024 1:48 pm ] |
| Post subject: | Re: "level" sanding on a concave surface |
I dare say it looks better than it did. Should have put some lampblack in the CYA back in ~2015, because now I have a perfectly clear polished view of the filled crack! I found this really stressful - i started w/ 600 grit and worked up through the full set of micromesh pads, then Macguire's ultimate compound. I found it very difficult to remove the last grit's scratches when you have to kinda expand your sanded area with each pad, and the contours made it hard to do that predictably. It's only your first time once - I learned a bunch and appreciate the help offered from everyone. |
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| Author: | Kbore [ Fri Oct 18, 2024 4:09 pm ] |
| Post subject: | Re: "level" sanding on a concave surface |
That turned out nice. Thanks for posting the result. |
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