Official Luthiers Forum!

Greetings folks. I'm starting an LMI mat'ls package that will become an OM-28, hopefully.

I bought the "kit" in May, trying to get a leg up on inflation, knowing that it would be mid-summer before actually starting work due to other guitar projects currently in work.

When I put the sides in the LMI form (very disappointed there), the ends were really springing back despite having been held together by LMI's packaging (pretty good).

Additionally, and this is what's REALLY bothering me, both sides are cupped just enough to give me grave concern.

I wonder if there are any builders in the Nashville/Middle Tennessee area who'd be willing to let bring what I've got to them and seek their counsel.

I'd be grateful for y'all's input, of course.

(Note: I also posted this in the Kit 101 board. Admins, I hope that wasn't a felony.)

I'd be talking to LMI about the cupped sides TOMORROW. Kits are supposed to consist of buildable parts.

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Peter Havriluk

You bought it in May, about 3 months ago.
What temp/humidity has it been sitting in since then?

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Pictures would help.

A little springback is common and not the end of the world. How easily does it conform to the mold with finger pressure?

How is the fit of the waist area to the mold?

If the cupping is near the ends of the sides it could be remedied when they are cut to length and glued to the neck and tail blocks.

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Brian R, Wood Mechanic
N8ZED

Thank you for taking an interest, gentlemen...

Colin North, I keep the humidity in the shop between 40 and 50%, temp typically around 76-78.

rbuddy, I'd be glad to post a couple of pix if someone could point me to a "how to post pics" link.

The springback is rather dramatic in that the ends (5" or so) require palm pressure rather than finger pressure to fit back into the mold.

And they really try to straighten out when released.

My problem with that is that the pre-load on the neck and tail glue joints would be tremendous.

Thanks again for your comments/questions. I hope I've described the situation adequately.

Pete Havriluk, on it. Thanks.

Are you planning to build it with a mold or a workboard?

Whichever one you decide on, use it to get the sides in a close proximity to the final shape. If you are using a mold it is easy to put it in and carefully clamp the upper and lower bouts against the mold. With a workboard, you can screw blocks down in the waist, tailblock and neckblock areas, and in bout areas, and again carefully (as in don't crack the wood) clamp in place. If it feels like the would will break before it is in place then stop and call LMI.

Once it's in the mould you can evaluate the cupping and better determine if it is fixable.

Note, I just noticed you are using a mold. If you can fit the sides into it without breaking most likely it will be fine. In time it will conform to the mold. Cupping is something else.

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Joe Beaver
Maker of Sawdust

Good news !!! Natalie at LMI has graciously agreed to replace the sides free of charge.

Pete, I may not have pursued a replacement, especially at this late date, were it not for your suggestion. Thank you, Sir.

Thanks again, to all who've responded.

Joe Beaver, those sides have been in the mold since sometime in late May with no improvement in either the spring back or cupping.

Thanks for responding, however.










Edit: Added comment - BC

My sight-unseen opinion is that springback is a common characteristic and represents no problem, the kerfing and installing the top and back controls springback readily. While molds aren't sold with spreaders, they all need spreaders. I've never seen, in my limited experience, a side that didn't need a spreader to conform to the mold.

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Peter Havriluk

Pete, I agree, re spreaders and I've always used them, even with this "guitar." Spring back, however, is not the central issue with this set of sides - it's cupping.

Don't know how you cure cupping once the sides have been bent.

BTW, can anyone point me to a "how to" link for uploading pix?

I made a pair of guitars out of an African hardwood 'boire'. The sides of both cupped badly. I put in side stiffeners to pull as much out as they could, and then went on a blocksanding party. For one long time. At the time I didn't have a spindle sander. Got done, but I swore off that wood species. I didn't cure the cupping but I did level the sides.

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Peter Havriluk

The very first step in building a guitar is preparing a place to work that has strict humidity control in a suitable range. For most of us that range is 40 - 50% as measured with a calibrated hygrometer or a wet bulb test. This should come before kits, tools, etc. so that when we start receiving tone woods and such you have a place to keep them where they can stabilize, acclimate and not warp.

Welcome to the forum.

Easiest way to add pics is to use the TapaTalk app, pics are as easy as posting to FB…

Good to know - thanks, Pete.

Hesh, I did precisely that when I started building 3 years ago. I think I mentioned, earlier in this thread, that I keep humidity between 45 & 50 and temps run between 75-78 in the summer time.

Thanks for the welcome.


Edit: Corrected spelling error.

Thanks so much.

Folks, here's one image of the cupping.

WHEN YOU REMOVE a side from the form and hold a straight edge across, the wood is clearly cupped where, in this photo the square is held off the top edge of the material due to the cupping.

At any rate, you can see the cupping even in this pic.

Why on earth the post repeated the pic twice additionally is beyond me. My only defense is that I'm not 11.

Pictures are way too large. Purpose?

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Peter Havriluk

Tapatalk has a bug, at least it did, where the “resize” option you’re presented with does not take effect when posting multiple pictures at the same time. I’ve worked around it by choosing one pic at a time, choosing “small” to let it resize, then repeat for each picture. It’s a hassle but works.


Sent from my iPhone using Tapatalk Pro

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Insta - https://www.instagram.com/cbcguitars/
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Could you make your pics bigger Blind Mellon Luthier here has trouble seeing them . JUST KIDDING and sorry I did not see your earlier mention of RH, my bad. Hesh is becoming a dotard 65 in a month.

Don’t worry Hesh, we all know you are obligated to post warnings about setting up humidity control any time a new maker posts. You can’t act contrary to your programming.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

No worries