Cloth Reinforcement

[David Nelson]

Hello,

I've just been looking at the C.F.Martin & Co's various modern interpretations on their early D-18 model. As I'm sure most of you know the top/most expensive model is the D-18 Authentic 1937, then the D-18 Golden Era and then to the Vintage model and the Standard Series. I noticed that the Golden Era model is based on the instruments from1934 and has "select mahogany back & sides with cloth reinforcement strips".

Can anyone tell me about this cloth reinforement? Is the inside of the guitar covered ripped-up underwear????? Is it glued on? Or is it just a subtle thing that can't really be noticed unless unless you know it's there? As you may be able to figure, I ain't got a clue what this would look like and why cloth would be used to reinforce solid Mahogany? I would look myself but I don't have access to a D-18, new or vintage...............unfortunately.

Regards to forum,

David.

[Frank Ford]

It's a simple vintage detail, and unobtrusive. Over the years Martin has reinforced (or sometimes not) the sides of guitars with vertical strips of cloth - generally a good, but minor, structural thing.

Here's a view of the strips in a 1946 D-28:

[mike carne]

Solid sided guitars should be reinforced.Thin strips of wood are more usual (Gibson) but Martin sometimes use cloth,known as ribbons,I think.Why I don't know!

[Mike Kolb]

The cloth reinforcement (if it's actually intended as such) that I've never quite understood is the cloth that drapes the intersection of the x-brace on the top plate.... any ideas on the history of that one?

[Eddie Bax]

My understanding was that because Martin didn't cross-lap the x-brace, but merely butted two short lengths into the larger one, that this was meant to strengthen the joint. They don't STILL build them this way, do they?

[David Nelson]

Thanks chaps!

Yeah, now that you have opened my eyes (a picture is worth a thousand words???) I have seen this quite a few times but only done with wood, never cloth. They always just looked like little braces........" would sir like them scalloped or unscalloped?". I didn't realise that solid wood guitars should have the sides reinforcedas a default technique. Thanks Mike!
I presume it, the cloth that is, has to be lacquered or somehow stiffened, to be useful as a support? Could it be argued that maybe this feature goes in & out of fashion depending on how heavily, or lightly manufacturers are building instruments at a particular time? Do you see 1970's Martins with this feature in your repair-work Frank? I would guess not, but that is one for the experienced person to answer. I know it is a generalisation, but weren't they built relatively heavily back then??? Anyway, now I know. Thanks!

Regards

David.

[Ned Knepp]

I'm certainly no expert but I think the idea behind the cloth side braces is to tie the long grain of the sides together across the grain. This could help prevent / shorten potential cracks that may develop as the instrument ages. I believe the cloth is soaked in (hide?) glue before being applied.

I recently repaired a split in the side of a friends guitar which had no side bracing at all, cloth or wood. I won't mention the brand because it's actually a very nice guitar, just not "braced" on the sides. The split started where his EQ panel was installed on the upper bout and ran about 9 or 10 inches down the side.

My friend is sightless and admitted that he left the guitar in a "weird" place then accidentally kicked the side but I found that three of the four screw holes for mounting the EQ panel already had short splits running with the grain. He hadn't noticed them because the cracks weren't (yet) long enough for him to feel but I could see them peeking out from under the edge of the bezel. There was a plastic plate inside the guitar for the screws to bite into but since this was not actually attached directly to the side with an adhesive, there was no reinforcement to the end grain where the side was cut out . I think some reinforcement across the grain in this area and the addition of cross grain strips, as it is in the picture Mr. Ford posted, might have stopped the crack from running so long and may have prevented it completely.

To be fair to the manufacturer, the guitar is one of their lower end offerings, though still an excellent instrument, and my friend has owned it for several years with no trouble what so ever, not to mention the fact that "kicking" a guitar isn't recommended treatment.

There could be other reasons for cross grain reinforcement of the sides but this is the best one I can see.


I think the Idea behind the cloth reinforcement on the intersection of the X brace is to tie together two lengths of wood that have had their strength compromised when they were notched for the joint.

I've seen a guitar that uses a "bridge" of spruce over the top of the junction rather than cloth. This ties together the two sides (ends) of the brace that was notched to fit under the other. It seems to me like a pretty good way to do it since the edges of the notch leave end grain as a glue surface where the other brace fits into it. Essentially, the "bridge" strip duplicates what the back plate does for the brace on top of the joint ( in other words, the back of the instrument "bridges the cut in the brace on top of the joint). I don't know if this is as strong as the cloth reinforcement or not but it really leaves a clean look to the joint. Maybe someone else, with better qualification would know.

[Eddie Bax]

The glued on cloth strips are a half-hearted attempt to keep the sides from cracking. If you have any experience with dry-wall, you know that the mesh tape has absolutley no shear strength when compared to old-school paper tape. David Russell Young used solid pieces of wood for cross-grain reinforcement, which makes much more sense; it does have the downside of adding mass, however.

They're doing it with the Golden Eras, because that's how they did it in "The Golden Era". I don't think it helps a bit.

[Ray Hodgson]

Hey Guys,

Take a look at this and maybe it will answer some of your questions:

http://www.luthiersforum.com/forum/viewtopic.php?f=10102&t=13219"

Ray