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  #1  
Old 09-22-2023, 06:48 AM
misterg misterg is offline
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Default Building an OM from Grellier plan

Hi folks, my first post, so a bit of an introduction...

I've had a long standing hankering to build an acoustic guitar, and have finally decided to scratch that itch. I have scratch-built a couple of solid body electrics (Tele, Firebird and an electric uke), so I have some idea what I'm facing in respect of making a neck and fretwork, etc. However I'm completely inexperienced with thin wood!

I joined up here a month, or so, ago and have spent the intervening time looking through past build threads and requests for advice (similar to this one!) - you seem like a friendly and knowledgeable bunch

When I was looking for plans, I came across the drawings on C. Grellier's website - in particular the OM: (link to pdf). The plans are well drawn and seem to be self-consistent and the size of the guitar is right for me.

I've already bought the wood for the build: Rosewood back & sides, European spruce top, mahogany neck blank & end blocks, ebony fingerboard, rosewood bridge and miscellaneous bits of binding, lining and purfling:



I've also jumped the gun and made an outside mould:



So, before I butcher any wood:

I have seen that these plans have come up here previously and that there didn't seem to be any negative comments. A local place has printed the plans out at A0 and the drawing dimensions are spot-on.

So - Am I right to assume that this plans is OK?

Are there and changes or modifications that people would advise?

Known 'gotchas'?

Thank you for any pearls of wisdom that you can offer.

Andy

Last edited by misterg; 10-17-2023 at 05:32 PM.
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  #2  
Old 09-22-2023, 07:28 AM
Fathand Fathand is offline
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I built my first guitar from the Grellier L-00 plans and two 000s from the OM plans that I made adjustments to. They turned out well, sound great, play accurately.

I have read different opinions on the Grellier plans, some for, some against. My guitars turned out well. They are less overbuilt than some plans out there that you would pay for.

Here are some Martin dimensions if you want to compare anything.
http://martinrep.com/dimensions.html

Your mold looks nicely made but I am wondering if it might be too deep for the neck end of the body. Is it 4 " deep? I made mine 3 " deep which allows a bit to protrude for clamping in kerfed linings with binder clips.
https://www.flickr.com/photos/194462...7720296961058/

Good luck on your journey.
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Old 09-22-2023, 07:56 AM
DickHutchings DickHutchings is offline
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I have to agree with Fathand, your mold will get in the way of installing linings. Molds are usually only 3 layers/2 1/4" total. I suppose you can slip the body up to get the clamps on. It may work just fine but I've never seen one like this. Good luck with it.
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Old 09-22-2023, 08:01 AM
Rudy4 Rudy4 is offline
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Hi Andy,
Good to see you jumping into the fray.

I checked out a bunch of the available plans for acoustics when I decided to build my "ideal" guitar. The Grellier has generally good reviews, but it didn't meet my specifications so I did my own CAD plan for what I wanted. I posted the PDF of my plan HERE on the AGF for anyone to use.

The majority of free plans on the net will provide the basics of what you need, but the only way you really gain an intimate understanding of how the instrument works is by building a few times.

Fathand's comment on form depth is a good example. A new builder would think that you would want to fully support the sides, but that's not how it actually shakes out. Since you usually end up working on a protruding portion of the body, it ends up being counter-productive to have anything more than 3" of form depth. This is stuff you only find out by actually doing it.

You're off to a good start!
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Old 09-22-2023, 08:35 AM
redir redir is offline
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I've built about 10 OM's with the Grellier plan. I finally got around to laminating the sheet so it no longer gets dirty to where I have to print it again. It's a good plan.
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Old 09-22-2023, 10:34 AM
printer2 printer2 is offline
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Quote:
Originally Posted by redir View Post
I've built about 10 OM's with the Grellier plan. I finally got around to laminating the sheet so it no longer gets dirty to where I have to print it again. It's a good plan.
Did you alternate the layers when laminating them?




Nice looking wood.
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Old 09-22-2023, 10:36 AM
Fathand Fathand is offline
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Quote:
Originally Posted by redir View Post
I've built about 10 OM's with the Grellier plan. I finally got around to laminating the sheet so it no longer gets dirty to where I have to print it again. It's a good plan.
I spray glued the body of the plan to a sheet of masonite and cut it out into a template with holes for transferring brace positions to the front and back plates. Did the same with the side profile for routing out sides. I have templates for headstocks and fretboards. I don't look at the paper plan anymore.
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Old 09-22-2023, 02:00 PM
redir redir is offline
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Quote:
Originally Posted by printer2 View Post
Did you alternate the layers when laminating them?




Nice looking wood.
I'm not sure what you mean. But to clarify might help, I downloaded and printed the PDF on 11x8 standard paper and laminated that sheet.

Quote:
Originally Posted by Fathand View Post
I spray glued the body of the plan to a sheet of masonite and cut it out into a template with holes for transferring brace positions to the front and back plates. Did the same with the side profile for routing out sides. I have templates for headstocks and fretboards. I don't look at the paper plan anymore.
Nice. I looked into getting a full size print of the plan but the local shop wanted something like $200 bucks to do is so I said forget it.
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Old 09-22-2023, 02:25 PM
misterg misterg is offline
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Wow! Thank you all for the positive responses - I will go with the Grellier plans


Quote:
Originally Posted by Fathand View Post
[...] Your mold looks nicely made but I am wondering if it might be too deep for the neck end of the body. Is it 4 " deep?
Thank you to all who picked up on this - yes, the mould is ~3.5" (90mm) deep, and the neck end of the body is 80mm tall.

I had fallen for the exactly the thinking that Rudy4 stated: "A new builder would think that you would want to fully support the sides". The body height did figure in my thought process early on, and my original plan was to make two 'half height' mould halves that could be stacked to make a full height mould for side bending, but somehow that plan got lost in action - I blame the MDF dust.

I guess that in the the back of my mind, I thought that I would be able to slip the body through the mould to expose one side or the other. It isn't a big deal to cut it down if necessary, at least.

Quote:
Originally Posted by printer2 View Post
Nice looking wood.
I think so, too. It came from Keystone in the UK who offer a thickness sanding service that I took advantage of. The wood was the lowest grade on offer.

The sides look beautiful.



The back has some worm holes near the join line that I think I'll need to saw off; a bit of a knot / whorl going on and there are some residual saw marks. The back plates are at 2.6/2.7mm thick at the moment, so there's only a little bit to take off to get to the 2.5mm on the plan.









The European spruce top is generally lovely and looks very well quarter sawn. I don't think I'll be able to avoid the dark grain lines at the edges of the lower bout (the outlines drawn on the wood at the moment are from the supplier, and are a bit bigger than the OM), but I'm sure that will be the least of my worries.





I haven't dared do much with the thin wood since it arrived as it has been very wet/humid here for the last few weeks (70%RH indoors) so I've just stickered it and left it alone.

Thanks again for the warm welcome - Further questions will follow!

Last edited by misterg; 10-17-2023 at 05:39 PM.
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  #10  
Old 09-22-2023, 02:27 PM
misterg misterg is offline
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Quote:
Originally Posted by redir View Post
I looked into getting a full size print of the plan but the local shop wanted something like $200 bucks to do is so I said forget it.
I paid 10 ($12) for two copies at full size (A0)!

I intend to use one of the copies for cutting out to make templates, etc.

I also find it useful to have the dxf files of the plans that are available on the same site.
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  #11  
Old 09-22-2023, 04:04 PM
Fathand Fathand is offline
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Quote:
Originally Posted by redir View Post

Nice. I looked into getting a full size print of the plan but the local shop wanted something like $200 bucks to do is so I said forget it.
I paid $10 Canadian for a full size print. We have "Staples" in Canada, not sure if you have it. Must be other places. Kinkos?

I have also printed full size at home using "poster format" multiple 8x10 sheets with hash marks then join with tape, but then I usually only print the portion I need.
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  #12  
Old 09-22-2023, 04:13 PM
Fathand Fathand is offline
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I would consider 2.5 mm near the maximum for a rosewood back thickness. I wouldn't be shy about going down to 2.3mm .
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  #13  
Old 09-23-2023, 02:08 AM
misterg misterg is offline
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Quote:
Originally Posted by Fathand View Post
I would consider 2.5 mm near the maximum for a rosewood back thickness. I wouldn't be shy about going down to 2.3mm .
Thank you for the reassurance
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  #14  
Old 09-23-2023, 07:25 AM
printer2 printer2 is offline
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Quote:
Originally Posted by redir View Post
I'm not sure what you mean. But to clarify might help, I downloaded and printed the PDF on 11x8 standard paper and laminated that sheet.

Nice. I looked into getting a full size print of the plan but the local shop wanted something like $200 bucks to do is so I said forget it.
Sorry, meant to do a funny there, laminating the sheets together with two vertical and the middle one horizontal.
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  #15  
Old 09-23-2023, 08:20 AM
surveyor surveyor is offline
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I use the Grellier plans on my L-OO models and they seem fine. It looks like you have some pretty good quality wood there for a first build. Unless you are not going to build another, you might want to store that set and get some cheap stuff to begin with. That way if you make a goof, you haven't lost as much. I'm still making mistakes (smaller now) and I'm 30 instruments into it. Remember, don't get in a hurry.
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