Prostheta Posted March 24, 2016 Author Report Share Posted March 24, 2016 By hand and eye....! I did a 45° chamfer to remove stock initially and set a consistent side line. The chamfering is shifting unlike SGs which are constant angle. Glad you like the bass! Quote Link to comment Share on other sites More sharing options...
Andyjr1515 Posted March 24, 2016 Report Share Posted March 24, 2016 It's lovely. I love the carve. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted March 24, 2016 Author Report Share Posted March 24, 2016 I take no credit for it whatsoever. The design is 100% Carl Thompson's: What I did find a pleasant challenge was the curled scroll. The point spirals upwards. Very subtle. Quote Link to comment Share on other sites More sharing options...
KnightroExpress Posted March 24, 2016 Report Share Posted March 24, 2016 The day I got to play a Carl Thompson bass was the day I realized that instruments could be functional art. I consider that moment to be the defining start of my lutherie journey. To say Carl Thompson is a big inspiration to me would be an equally big understatement. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted March 24, 2016 Author Report Share Posted March 24, 2016 Good for you! Carl is such a humble guy. He deserves far more credit than he gets, however that's never bothered him much. Carl seems disappointed in people that take credit for his work and ideas. Surprisingly, there are some VERY well-known names on that list of people.... Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 Time to bring this one up to date a little, if only in terms of thought processes and plans. The next job for the body is of course the bevelling. I knew that would be a hugely important thing to get right since SGs are defined by that. The question has always been, "how to mark out the bevels?". As I understand it, their angle is constant or at least, has been over the various iterations of the SG. Short of doing this work using a pin router or a spindle moulder. I figured that this should be an exercise in simplicity rather than manufacturing. I could do the latter, but it seems a bit daft given that I'm only making the one. Total overkill, and it isn't like I'd be learning anything new (I did this kind of work for a long time). So, simplicity is the order of the day. A constant angle means that the distance that the top bevel markings are laid out as should simply be a ratio when transferred to the sides. If I work out the angle I want to use, I can work out that top/side (actually, "adjacent/opposite" in trig.) ratio and make myself a temporary right-angle rule in CAD. This can also be made specifically to take into account the body thickness so that I can mark out both sides at once for the symmetrical bevelling.... Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 My first thoughts go to identifying the deepest bevels, since we don't want the body ending up too thin/sharp at these points. These should serve as a reasonable way to figure out the angle. Applying that to the rest of the contour should produce a good result. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 The largest dimension seems to be around here. Let's call that 21mm. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 The exact body thickness is 36,5mm so we can divide that up nicely. Using this reference photo of an Angus Young sig.... ....note how the approximate area identified correlates with the thinnest part of the outer edge. I'm happy to go with that. I see minor variation, however it'll be of nearly zero consequence. Since Gibson never used a consistent approach to bevelling, I started from approximate round numbers to see which eyeballs well: 1 Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 I've seen 30° quoted a couple times around the net and it certainly looks less severe than 35° and more effective than 25°. A lot of the differences can be modified in/out using the softening over the sharp edges. A slightly larger roundover makes a big visual difference. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 If you draw these things out in CAD, there's no real maths involved really. Just basic geometry. ....alternatively, you can work out a perpendicular distance from the top to the bottom of a bevel with a bit of trig. Assuming a distance of 1cm from the edge to the marked line on the top produces us a simple length ratio relationship from the top to the side.... SOHCAHTOA tan (angle) = opposite/adjacent opposite = adjacent * tan (angle) opposite = 1 * tan (30) = 0,577 So whatever the distance is from the edge to the marking on the top, multiply it by 0,577 to find the "drop" at the side. Simples. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 I specifically dimensioned the 30° bevelling ruler so that it matches the body thickness and has symmetrical markings for both sides. The markings were made fractional, since the human eye is better at dividing distances in two. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 I have an entire box full of scrap pieces and sticks that I collect, which have been thicknessed, squared and cut straight at the ends. They come in useful for all kinds of things when you need precise yet quick jigs. Chop a stick in two. Flip the small piece 180° so that the right-angled end is facing inwards and add a bit of glue (Titebond I in a small chilli sauce bottle I saved - very handy). Clamp it from the sides to keep it flat and inwards to make a good join. This makes me a perfect right angled ruler....I'll get back to this when its dried.... Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 A very slight recess was added into the internal corner with a triangle file so that the rule can reference the flat surfaces better. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 A glue stick gets the scale pasted onto both sides.... From hereonout, it's a case of transferring marks and "joining the dots". For the convex surfaces, this is no problem. In the waist however, the thickness of the rule means it is impossible to align it perpendicular to the outer edge. This is no huge problem since the bevel rate of change is fairly linear at this point. The outer dots line up satisfactorily. Most of the dots were placed fairly closely, however this wasn't that important. Interpolating them using a straight-edged piece of spring steel (my INCRA T-rule's scale) produces an excellent line to work towards with a rasp.... Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 To be continued..... Quote Link to comment Share on other sites More sharing options...
psikoT Posted July 5, 2016 Report Share Posted July 5, 2016 shit, I can not give more likes today... Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 That's the weirdest compliment ever. Thanks. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 Okay, it's just far too warm today in the workshop. 25°C/53%. No thanks. I left it at this for today. All shaped with my trusty Liogier rasp. Like I've always said about that tool, you can work right up to your lines without worrying. There are a couple of areas where I didn't get right up to the line, however that's far from being an issue of course. I'd estimate that as being about 20-25mins of work with the body chucked up in the leg vise. That worked out really nicely, however the rasp being stitched for right-handed use meant a few changes in work direction to get the most efficient cut. 2 Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 The bevels will be easy to clean up with a flexible sanding block. At this stage they're super rough, having come pretty much straight off the rasp with a few fuzzies knocked off with 60 grit. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 "All you need is love", sang Lennon. This is not true. It turns out that I needed a cup of coffee and to put my feet up. I might leave it at that for today. 1 Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 In some ways, I think that 30° is slightly much. If I ever repeat this project, I'd like to try something between 25-30°. It's certainly not super thin at the edges (unlike say, original 60s SGs) or making me regret going 30°, however I think slighter bevelling and softer roundovers are on my mind. Maybe a 40mm thick body would support 30° better. Still, it's all going swimmingly. It was worthwhile spending time mulling over how to layout and implement the bevels. That rasp makes it a breeze. I need more of them. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 I just kept going back to it. At this rate, I might have it done this year. 1 Quote Link to comment Share on other sites More sharing options...
psikoT Posted July 5, 2016 Report Share Posted July 5, 2016 That bevel reminds me my last build, but I had a different angle all around the perimeter. It was the hell to get a fluid constant plane without hitting the contour limits. Also was specially hard to make a true flat bevel, so take it with calm, it looks easier than it is. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted July 5, 2016 Author Report Share Posted July 5, 2016 I've actually not found it difficult. Like I mentioned, being able to work up to the lines without worrying about it blowing out or anything is useful. Khaya, Mahogany and other African "Mahoganies" tend to be cottony and soft, so aside from the end grain retaining scratches, it's easy to work with. Always a pleasure to go back to carving and shaping Mahogany. The trick is in knowing how to keep the tool moving in a way that helps to maintain straighter lines rather than rounding them out or taking it off course. I could do with a smaller half-round rasp I think. The cabinet maker's rasp is a little big for the cutaways.... Quote Link to comment Share on other sites More sharing options...
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