Thread: Mini Jumbo build number 1

Go for it! There is sooo much to learn about this art.

Rather than buying a back and side set we decided to use some timber that we had on hand and cut it to size ourselves. We found this piece under the workshop thinking it was beefwood, but after running a blade down the edge discovered it was rosewood. (I think it's actually rose mahogany - not a true rosewood)20130601_153125.jpgWe cut it down to sections that we could cut back sets, side sets and necks as it had a big crack in the middle that had to be worked around. after a bit of effort we ended up with a nice bookmatched back set.20130601_162735.jpg. Unfortunately I discovered that the thickness planer was a bit too harsh and the 1st one shattered at 6mm thick. I put a bit of turps on it to show up the colour anyway, I might get a headstock veneer out of this yet.20130601_172126.jpg

I assume you will be heading for 2mm for the back? Hand planes are a lot more reliable for the stuff lufiers do. Or drum sanders. Fancy figured stocks, gotta love em, gently....

yep, learnt the hard way on that one. managed to cut another off the same slab so still had a nice bookmatched back, and yes, this time used hand plane and drum sander. I've taken the back down to 3mm and then used the router to cut a channel for the back strip. Had another setback here as well when I tried to tap a tight fitting strip into place and split the back. I quickly glued and clamped it to try to save it but there is a big split right in the middle - The lessons are coming thick and fast. from phone oct 2013 049.jpg . Sides are also done and we planed these down by hand and then finished on the drum sander. These are down to 1.3mm from memory. I don't have a side bender yet - have been looking at various DIY designs and may end up just buying one as we plan on doing a few more after this one. 012.jpg Being such a newby I'm still amazed at how much ends up on the floor. very satisfying work using the hand plane and looking forward to trying to bend these although not looking forward to cutting new ones if they break. Speaking of breaks, after we discovered that the back was unsalvageable we tried to cut another set from the same block, but found that the cracks through it would make that impossible so we ended up searching for another piece of the same timber. Eventually found a very straight grained piece with no cracks, knots or any blemishes. It's not as pretty but at least it will match the sides. speaking of lessons, this set was cut and taken down to 3mm and then jointed in a quarter of the time it took to do the first one.211013 033.jpg apparently I didn't take a photo until we had inlayed the back strip. The strip is sassafrass with timber purfling that was purchased. I'd be interested to know if anyone else makes this themselves or just buys it. The stuff I got is a bit inconsistent in that it varies in width and sometimes delaminates but this has come up very nice I think. Very happy with the figure in the sassafrass as initially it looked like a bit of mdf. This timber stuff never ceases to amaze me.

Ok, when we initially decided to build this I had intended to use something like hoop pine, given it was an experiment of sorts. But after looking at the back and sides we were I wanted to do them justice so I went ahead and bought a spruce soundboard. This was run through the drum sanded to bring it down to 3mm before cutting the rosette channel. I ended up using a circle cutter in the drill press and then hand chiselled it. This wasn't ideal and next time I'll use a router. Actually this process gave me some grief! I had purchased a rosewood and abalone rosette inlay off ebay - looked nice and at the price I couldn't justify trying to make one and cut abalone to size. So using this as a guide I set the hole cutter up to score the inner and outer circumference of the channel. It was too tight so I adjusted the cutter and re did it, but of course this time I made it just a fraction too big. I decided to glue it in and see if the gap could be filled later... but no, it looked like crap. To fix it I carefully cut around the inside and outside edge of the rosette and then using a split piece of purfling added a white and half thickness black ring. from phone oct 2013 055.jpg. Happy with the result I took to levelling the rosette flush with the soundboard. This is where my ebay bargain turned out to be a mistake as the abalone was so thin it started to disappear. I ended up taking it all off and had to continue sanding it back to remove the glue shadow. Here's a close up of where the black and white didn't go deep enough into the groove and disappeared with sanding. I hadn't intended on adding a pick guard but it will hide this if it stands out too much211013 024.jpg.

Quiet day at work today so more pics and progress... Once the rosette was finished I used the bandsaw to roughout the shape and then used a table router with guide bit to trim it back to the template shape. 211013 020.jpg211013 023.jpg Next I set about making the bracing. I ended up using sassafrass again for the bracing as we have a lot of it and it's nice to work with. My fear here is that I may have been a bit enthusiastic with the scalloping - there's not much meat to them now that I see them glued on to the board. I also shaped them before gluing - I had a fear of putting a chisel through the back of the soundboard. After trying a few techniques I ended up cutting the curves with a scroll saw and tidied then up on the sander to get the final shape and then took any edges off with a quick sand. This worked out well and using a go-stick board we made the gluing up was remarkably simple. The x brace still needs some finishing.211013 027.jpg211013 029.jpg211013 028.jpg I'm really interested to see what anyone thinks about the bracing - I've seen many comments about beginners overbracing their soundboards but I think I may have gone the other way.

a couple more pics and this brings the progress up to date - this one started in July and so far I think we've only managed to coordinate 5 days in the workshop so progress is slow. Still hoping to have this ready by Christmas and factoring in 8-9 full days working on it. I might be kidding myself?? Here's the neck blank and then with the headstock cut and joined on the angle. Getting the 18 degree cut was difficult as nothing in the workshop would do that type of angle. Any tips here would be appreciated.20130601_161639.jpg here it is clamped up 015.jpg We cut our own binding and glued the BWB purfling to one side. After mucking around for while with this trying to clamp it all into place, we discovered a neat trick. Using masking tape, sticky side up we put the sassafras binding down first then glued the strip of BWB to one edge - the masking tape held it in place perfectly and then another piece of tape over to top made it really easy to work with. once it was dried the tape came off and the glue joint was perfect. Here's the end result from phone oct 2013 057.jpgfrom phone oct 2013 059.jpg. So like I said up the top this project was started in July. We initially started talking about doing it back at Christmas time 2012 and it took us 6 months to get into the workshop. In all Id say 60 hours workshop time so far and that also includes making the go-stick board, cam clamps, dowel clamps for the workboard, a thickness guage, soundboard template and what seems like hours pondering how to do each task. So far I've learnt a lot, but so much more still to do and I'm sure there'll be a few more mistakes along the way. Next job is to brace the back and trim it to shape, then onto the neck. Headstock has to be shaped, heel block added and truss rod channel cut. Then onto shaping the heel and tapering the neck. With any luck I might get that done this weekend.

I found a few more pics on my phone... this one is the rosette channel before cleaning it up. will not be using a chisel for this next time from phone oct 2013 051.jpg as it's too easy to screw it up and I had a lot of trouble getting the bottom flat and consistent. Next one is the new back set after they were glued. As you can see it doesn't have the same figure of the original but it infinitely easier to work with.from phone oct 2013 056.jpgNext up is the back strip channel after it had been routed. This went well second time around - made the channel a fraction bigger and made sure the strip fitted into the gap without too much effort. The hardest thing here was the BWB strips varied in width by nearly 1mm from one end to the other. a bit of work sanding them back to fit the channel and all was good. The results were in an earlier post and I'm more than happy with how it came out.copied from phone 240913 011.jpg. Next one here is the soundboard in the drum sander. This spruce is an interesting timber - the dust that came out of the sander had a really strange consistency, almost sticky. I had to make sure the dust extractor was working properly and had to give everything a good clean down with the air gun afterwards. copied from phone 240913 012.jpg

Originally Posted by JSmyth

I'm really interested to see what anyone thinks about the bracing - I've seen many comments about beginners overbracing their soundboards but I think I may have gone the other way.

Looking at the photos, your X brace and tone bars look a tad on the wide side. What width are they? Beginners often overbrace as theres an ever present fear of the top caving in through lack of bracing. You soon get to know how heavy to go with the bracing as you work the top. I flex and tap the top frequently to gauge stiffness.

Originally Posted by JSmyth

I also shaped them before gluing - I had a fear of putting a chisel through the back of the soundboard. After trying a few techniques I ended up cutting the curves with a scroll saw and tidied then up on the sander to get the final shape and then took any edges off with a quick sand.

While scalloping braces I lay metal rulers each side of the brace to protect the soundboard. I also wrap masking tape around the corners of the blade.....it's these that will dig into the top.

hey thanks for the feedback. I can't remember the exact measurements but pretty sure that I cut some sass down to 9mm x 12mm and used this. The book I'm using gave me the measurements, but having said that they also use spruce or WRC - I'd imagine the sass is a much stronger timber. I should also add that the x brace is still to be shaped - I've cut them to the depth I want but still need to narrow the tops to a peak the same as the rest of them. I like the idea of the rulers - not sure if my mate who owns the gear would be too impressed though, but I reckon that tape on the corners of the chisel is the way to go. Now... given they are all now glued to the soundboard, would you recommend going to sharper peaks by thinning the bulk - obviously the gluing surface will have to remain as is. I've also seen a bracing design that had the centres of the braces cut with a groove. I'd imagine this would reduce the weight but maintain the lateral rigidity of the piece - much like a steel "I" beam. When it comes to overbracing, what is the downside? Is it a less responsive guitar that requires more string attack or does it reduce the tone spectrum?

Originally Posted by JSmyth

Now... given they are all now glued to the soundboard, would you recommend going to sharper peaks by thinning the bulk - obviously the gluing surface will have to remain as is. I've also seen a bracing design that had the centres of the braces cut with a groove. I'd imagine this would reduce the weight but maintain the lateral rigidity of the piece - much like a steel "I" beam. When it comes to overbracing, what is the downside? Is it a less responsive guitar that requires more string attack or does it reduce the tone spectrum?

You should be aiming to take some meat off the sides of the braces while maintaining the height. I do this using a small plane and/or a paring chisel and finish off with sanding sticks. Watch out for any runout in your braces which may cause tearing out when working in one direction with a chisel.

Forget about cutting grooves in your braces......fancy alternative bracing can wait until later builds. If you want to go for an I girder model then laminated bracing with carbon fibre tow under and on top of the brace is my preference.

The primary function of bracing is structural...its there to stop the top crumpling under string tension. At the same time the bracing must also not make the top so rigid that it can no longer vibrate freely. To me overbraced guitars generally sound dull or dead and tonally "muddy".

Thanks for the advice - really appreciate it. I think I might use a file or sanding block and tape the soundboard - the sassafras seems fairly brittle when a chisel goes near it and I'd hate to split it. I'll get onto this next time I'm in the workshop and will post some pics. So the next thing is the tap tone. what am I looking for here? (I know this is a topic that has stirred up a lot of opinion before) Do I hold the edge and give it a rap or do I hold the x brace. I assume I'm looking for some sort of resonance or sustain in the sound. The plain, unbraced Sitka has a sound of it's own - even in handling it. If I run my finger over the end grain for instance it almost sounds like a rasp being run across it - ok some exaggeration here, but you know what I mean...

Originally Posted by JSmyth

The sassafras seems fairly brittle when a chisel goes near it and I'd hate to split it. I'll get onto this next time I'm in the workshop and will post some pics. So the next thing is the tap tone. what am I looking for here? (I know this is a topic that has stirred up a lot of opinion before) Do I hold the edge and give it a rap or do I hold the x brace. I assume I'm looking for some sort of resonance or sustain in the sound. The plain, unbraced Sitka has a sound of it's own - even in handling it. If I run my finger over the end grain for instance it almost sounds like a rasp being run across it - ok some exaggeration here, but you know what I mean...

1. Sassafras wouldn't be my choice of brace wood. Under a sitka top I usually use sitka bracing...light and stiff and with good straight grain and no runout there are less issues carving and shaping it.
2. Tap tones. You can take different approaches to tap tuning a top. For me I follow both a qualitative and quantitative approach. With the quantitative approach....I'm listening to mainly the resonance and responsiveness of the top. Im trying to gauge whether or not Ive reached the point where Ive reached minimum thickness but the top is still stiff. The trick is to hold the top between your thumb and fore finger at a point where the top is not vibrating. You find this by trial and error....once youve found the right spot youll notice a marked change in resonance and sustain as you tap the top with a knuckle...or in my case I use a hammer made from an eraser and a length of dowel.

The quantitative approach - I follow the Gore/Gilet school of building of late so before I start work on a top Ive measured the physical properties of the top and calculated a target thickness. I take the tap tuning concept to the next level and actually feed the tap tones into a spectrum analyser on my laptop. This gives me a quantitative measure of how the top is vibrating. I also employ Chladni testing which involves visualising how the top is vibrating by exciting it at different frequencies via a speaker driven by tone generator/amp. I use poppy seed on the top to show up the parts of the top that are and aren't vibrating (nodes and antinodes).