Building an OM from Grellier plan - Done!

[redir]

Oh hmmmm. I wonder if when I called the print shop there was a misunderstanding or something. Nonetheless the small plan works for me fine.

[Rudy4]

Originally Posted by redir

Oh hmmmm. I wonder if when I called the print shop there was a misunderstanding or something. Nonetheless the small plan works for me fine.

When I retired I did an internet-based side business selling full size CAD drawings for a few specialized instruments. I went to Kinko's and another "print shop" initially when testing out the process of getting my drawings printed.

Even though they both had plotters / printers large enough to do the work there was very seldom anyone there who knew how to operate the software that controlled the machines. The few times I did manage to get a knowledgeable employee the roughly 3' by 4' prints were still around $5 when getting a small bulk run done.

The answer for me was working with a local architectural / industrial print shop that had really nice German made machines and the owner knew how to run them.

He initially had me download and install a print driver for a specific machine in his shop and had me e-mail him the "print file" made from my CAD software, selecting his machine from my "available printers" list. That worked well, but the driver was updated several times in the first year, and that was a bit of a headache.

He then had me simply print the file as a pdf and e-mail it to him. He would then tweak the printed border size if necessary to match the border size listed in the drawing information box. He usually printed to within 1/16" border, and that worked really well for me.

Each copy ended up being around $1.25 each when getting 100 done at the same time.

This might end up saving someone a lot of time and effort if they want to have full size prints made. Kinko's and similar shops can be a bit of a roll of the dice.

[misterg]

Originally Posted by surveyor

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.

I would by lying if I said I wasn't slightly taken aback by how nice the wood looks, but at the moment this is a one-off thing (I don't *plan* on making any more...) so I just need to try and do it justice.

Originally Posted by surveyor

Remember, don't get in a hurry.

Oh, I need to get that up on the wall of my shed. I've fallen foul before where I get into the 'just one more thing...' mentality. My new motto was 'If it's all going well and you're making great progress... Then it's probably time to stop.'

Thank you,

Andy

[misterg]

Well, I've been tinkering around the edges - I took a perfectly good spruce plank and split it into what looked like kindling





Then spent some quality time planing it back square again and to the thicknesses needed for the bracing







I made a simple template jig to route the radius on them and reduce them to a little over their finished heights. I will wait for a spell of low humidity before glueing them to anything though.






I did pick up on the fact that the upper transverse brace (T1) has a different radius to all the others to get the right height for the fretboard extension. (It's slightly steeper than the back.)


Yesterday I got the top and back plates out for a closer look. I trimmed off a few mm from the backs to get rid of the worm holes and get the figure properly symmetrical.

I also managed to get them jointed and glued - It took me a while to get the joint line perfectly tight, but it made all the time spent tuning up the plane worthwhile when I eventually got the plates to meet without even a hint of light between them when held against a window pane. I thought that I had better glue them while the surfaces were fresh. (I clamped some blocks against the edges while the joint was raised on a batten, then pressed them flat to apply pressure which seemed to work very well.)




There's plenty of light showing here -







This is them after a quick going over with a scraper today, with my outline tentatively marked on them (if you can make it out) - I favour the higher placement of the two marked on the top as it makes the grain at the outside of the bouts more parallel to the guitar and avoids cutting the darker grain lines quite so abruptly.



Andy

[redir]

Looking good Andy. It's always best to glue freshly planned or sanded surfaces right away. It increases the surface tension of the glue joint making it stronger. Alan Carruth could expand on that if he comes into this thread.

I think it was David Russels book on guitar building where he said that he built a 'spring joint' when joining the top. The theory was that the joint aloud for expansion during the wet Spring months. It might be something that cabinet makers do to. They allow a little sliver of light dead center of the joint panels that tapers off to zero at each end. When clamped in a jig they push together.

Not sure that is accepted today in guitar making but I always found the idea interesting. I keep my shop at the proper %RH so when I join panels I go for zero light. IF there is a spot of light where the sound hole goes then that's ok.

Once you get the hang of it you can join a rough top in about 15 minutes.

[misterg]

I got the top, back and sides roughed out.

I've planed the sides down to 2.2mm (0.087") per the plan. I measured the thickness with a dial gauge mounted off the gantry of my CNC router. The numbers on the sides is their deviation from target in 0.01mm. I think they're reasonably uniform (worst is one side that has an edge that is 0.1mm under - nothing is significantly over thickness):





The plans give 2.5mm as the back thickness, but some areas were below this already. Thanks to Fathand's reassurance above, I had no qualms about evening everything out at a bit over 2.4mm.



I'm glad that the wood came already thickness sanded and I only had to remove a few tenths of a mm. The rosewood certainly takes the edge off a plane iron quickly (might be my cheap planes).

I've also had a play with the CNC to cut out a rosette design from ebony and maple offcuts:






I glued the segments up in a groove cut in a sacrificial piece of wood, faced them off and then cut through the OD and ID.





The idea would be to glue this side of the rosette into the soundboard with a line of BWB purfling either side.

I haven't committed to using it yet, but I think it will look OK. The pattern will go clockwise when it is flipped over.




I've had a go at a 'bending iron' too. It seems to get plenty hot enough, but I need to get some practice in with scrap wood, and then offcuts from the sides / back.





If anyone sees anything wrong, please sing out.

Thanks

Andy

[misterg]

Well, that was illuminating!

I spent the afternoon playing with my bending pipe.

I tried some thin spruce, and it didn't really want to play, but the offcuts of rosewood bent beautifully, even though they were 2.6mm thick.

I'd cut some strips from the excess material for the sides and managed to bend a couple of these into fairly convincing guitar shapes. They may well end up being laminated to use as solid linings for the back/side joint.




Just got to pluck up the courage to try the sides...

[Fathand]

Originally Posted by misterg

Just got to pluck up the courage to try the sides...

Looks like you got the process down. If it helps your confidence, I've heard that Indian Rosewood is the easiest wood to bend. If the unthinkable happens and you break or burn your sides, there are lots of Rosewood sides and backs on the market.

[Howard Klepper]

Originally Posted by surveyor

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.

I see this advice--to use a low grade set of wood on a first guitar--regularly here. I think it is bad advice. Basically it's saying you should plan on failure rather than planning on success. The OP is obviously an experienced wood worker, and many people build very nice first guitars. His back and sides are good, but short of great EIR, and equally good sets are easy to find. Very nice top; go ahead and use it! You never know which guitar will be your last.

I like to look at it this way: Which would you regret more: (1) if you used good wood and made guitar with some flaws and mistakes; or (2) if you used cheap wood with limited potential, and your workmanship turned out to be really good? I would rather have wasted some of the potential of good wood than be wondering what my guitar could have been if I hadn't used cheap wood.

[misterg]

Originally Posted by Fathand

Looks like you got the process down. If it helps your confidence, I've heard that Indian Rosewood is the easiest wood to bend.

Thank you, I can well believe it - the rosewood just seemed to turn to toffee when it got hot enough. I was surprised how long it stayed workable, too.

Anyway - humidity isn't playing ball here, and it's still too mild to put the house heating on, so I cobbled together an improvised wood store from a large cardboard box. It has a computer fan and a couple of power resistors inside (running off 12V) and keeps the humidity inside the box at around 50%. It's just big enough to get the top, back, brace wood and a few other bits inside.





(Incidentally, I can recommend the little thermopro TP357 humidity meter - it gives a graph on your phone over bluetooth.)

I'm still working up courage to try bending the sides, so I continued to work on the top instead:

I used my CNC router again to cut a recess for the rosette.



I hogged the bulk out with a conventional spiral flute bit, then used a down-cutting bit to gradually machine away the OD and ID. This shows the difference in the finish and amount of fuzz on the spruce (ID is down-cutting, OD is conventional):



I kept going until I could fit the rosette and purflling in. Having seen people struggle with the wood swelling during glue-up, I went an extra 0.1mm - in hindsight, I don't think it was necessary.



I glued everything in and clamped it up while still on the machine. After the glue had set for a few hours, I used the CNC to deck the rosette down to about 0.2mm proud of the top.



Next day I took it level with the top using a scraper



I then proceeded to thickness the top - the plates had been sanded with something of a wedge, and it took a while to get them to an even thickness. I was using a dial gauge to measure thickness again:



The shavings that came off the top were beautiful - thin enough to read through!





I was aiming for the 2.8mm on the plan, but there was still some unevenness when I got there. Working this out, and a bit of sanding took the general thickness down to about 2.7mm (0.106"). At 2.8mm, the top still had a noticeable tone when held at the nodal point and tapped, but this had pretty much gone at 2.7mm. I have heard someone use the word 'flooffy' in the connection with top thicknessing - I would say that this is the perfect description of what happened to my top. It still very much has the 'sheet metal' sound when you hold it by the edges of the lower bout and shake it.

This is how the thickness ended up (the pencil numbers are the thickness deviation from 2.7mm in 0.01mm units) - there are a couple of very thin areas in the upper bout (roughly 2.6mm / 0.102") but I think this is near to areas that are braced, so I'm not unduly worried about that - the lower bout thickness seems to have come out quite uniform.



I sanded it to 240 grit (front and back) and put it back on the CNC to cut out the sound hole.



It seems to have come out OK cosmetically.





It's back in its box now, stickered up while I agonise over whether I've gone too far thinning it out... (there'd be a smiley here, but I'm at my image quota for this post!)

[misterg]

Originally Posted by Howard Klepper

You never know which guitar will be your last.

I like to look at it this way: Which would you regret more: (1) if you used good wood and made guitar with some flaws and mistakes; or (2) if you used cheap wood with limited potential, and your workmanship turned out to be really good? I would rather have wasted some of the potential of good wood than be wondering what my guitar could have been if I hadn't used cheap wood.

Thank you - I'm not planning to become a guitar builder, so it made sense to me to get some reasonable wood and make the best job I can with it.

[misterg]

I've got the rough braces fitted to the back and top:

To mark the brace positions on the top I extended the outline of the braces on the paper plan so I could lay the top on the paper and transfer the positions of the brace ends onto the edge of the top (to save messing about with tracing paper or templates).



I followed the scheme from the Cumpiano book and glued the 'flat' braces on first. The sound hole braces are made from excess spruce from the top.
Then the tone bars and the other braces were glued on, one at a time, using a radiussed caul to clamp them. The top piece of the clamp has a slight convex curve to try and achieve reasonably even clamping pressure.



The transverse brace has a steeper radius than the other top braces, but the caul for the back radius was close enough to get it clamped up



I did mortice the ends of the finger braces and tone bars into the X braces, as it just seemed 'workmanlike' to do so.



The first X brace being glued on. (The clothes peg is holding together a small split in the end of the transverse brace that I have glued back.)



It occurred to me part way through this process that the top may end up Pringle shaped, and although it did go a bit weird part way through, when the final X brace was glued on, it came back to a nice, even shape.

I had saved a strip from the excess top material for the 'marriage strip' (?) on the back.





The masking tape was to avoid marking the back with the edge of the plane when profiling the strip. It turned out to be a mistake - the tape was sold to me as 'better' than blue tape - supposed to be low tack, but it left a horrible, gummy residue when it was peeled off that turned out to be really difficult to remove completely. (We live and learn...)

The back braces were glued in the same way as the front (with a different radiussed caul).



So then I had this:



Bridge plate being glued on



I have started profiling the braces to the shapes shown on the drawing - the vertical profile is there, or thereabouts (maybe 1mm high), but I've only started thinning the finger braces so far.



My plan is to continue to work away at this until the heights and cross sections match the plan - unless I get any guidance to the contrary!

[misterg]

I think I'm done shaping the back braces, but before I finish sand them, would anyone care to comment?

Am I on the right lines?







Thanks,

Andy

[misterg]

Before having a go at bending the sides, I wanted to make the head and tail blocks. Before I could do that, I needed to tie down the details of the neck joint.

The plans show a tapered dovetail, but I'm not going to do that. If I retain the rather slender heel shape, I think there needs to be *some* sort of a tenon so that there is enough wood left in the area (otherwise, I was quite attracted by the tenon-less bolt joint). I don't like the idea of drilling through the tenon for barrel nuts, and I don't think there's enough wood there to take an insert (unless I change the heel shape).

This is what I came up with:



It's a 16mm wide tenon with two M5 x 50 bolts threaded into a 10mm diameter brass dowel in the neck heel (in a hole drilled from the top of the neck).

Here are the details if anyone is interested:



I would intend to put belleville washers (or similar) under the bolt heads to maintain tension as the wood moves with the seasons (I don't know if this is common practice here, or not).

Anyway, with a plan in mind, at least, I could make the head and tail blocks.



I chose to cut the mortice in the head block before fitting it as I fancy my chances of getting it fitted squarely more than I fancy trying to rout it in-situ. If it goes awry, I can fill the mortice and re-cut it, so I won't be any worse off.

The head and tail blocks were matched to the contour of the mould



I then exercised my little Delta bandsaw to the max and cut down the mould halves to a more reasonable height:





So then, there was nothing for it but to have a go at bending the sides. I used a damp paper towel between the tube and the wood, and it seemed to go pretty well:





The clamps are only holding the sides tight to the mould while they dry - there's no real pressure on them.



Next morning, the sides came out of the mould halves without any spring back at all.





Although the sides looked OK, I could feel a couple of uneven spots when I ran my hand over them. I marked these up - for example there's a couple of flat spot at one edge of the side here...



... and I spent a little more time back on the bending iron trying to even these out. (I think, sucessfully, but time will tell...)

I then trimmed the sides to length and glued in the head and tail blocks



So that's where I am

[printer2]

Any reason for the size of the pictures? Takes forever to load the page and at times crashes my browser. I usually scale mine down to the size I want it to be in the post.