honza992

Yeah, getting the ratios right is key, as is stirring...a lot. Epoxy has got lot's of advantages. It's got a long open time, so you've got lot's of time to set up clamping etc. it's incredibly strong, it doesn't creep, and it gap-fills better than wood glue. Also, it's not water-based meaning that I'm not introducing moisture and possible warping into my very thin piece of wood. The disadvantage is that if it doesn't cure properly....yer buggered. Up until now West Systems has been spot on.... I generally use Titebond for most things. But for critical joints and anything designed to never come apart, epoxy is great. It was suddenly colder last night, but this is Italy, it's not the arctic....Cold for us is anythng below 15C !! Fingers crossed tomorrow morning it will be rock hard and all my hair pulling will have been for nothing...

Ok this is a bit frightening. The epoxy hasn't completely hardened. It's hard but I can still push my finger nail into it. I've had failures before with epoxy, but never with West Systems and my way of measuring out exact amounts with syringes. Fingers crossed it just needs more time. This is why it's always good practice to keep the mixing pot so you can check it's completely hardened. We'll see how it is in a few more hours.

I've started on the bracing. The blanks I've got are very oversized, so by cutting some off at the line I can end up with a brace which is almost perfectly quarter sawn: Putting it onto the platform, I use a biro sticking through a Gibson selector switch washer to mark out the shape of the top onto the blank. You can chose either Rhythm or Treble depending on whether you want thundering lows or blistering highs.....It also means you can get a pretty much exact contour. Because the top is arched in both directions I mark both sides of the blank. With a spokeshave I then carve down to the line... ... My makeshift 'go-bar deck' is ugly but very effective. I find myself using it all the time either for gluing or just holding stuff down. Here I'm using it for both. The brace get's held in position on top of a piece of sandpaper (150G). You can adjust the go-bars very quickly so they apply just the right amount of pressure so the brace is held in place but you can still slide the sandpaper back and forth to get good fit. Finally the brace can be glued down in the same way. I use West System epoxy. I use the Ken Parker method (as usual). Which is wet the brace, put it onto the top, then remove it so you have an imprint: The idea is to let the epoxy soak into the wood as much as possible. I've got a silicone brush which I use to go back and add more epoxy to any parts that soaked it up. Finally, clamping in the go bar deck. One of the (many) good things about epoxy is that it needs very little clamping pressure, just enough to stop anything moving. Squeeze out I clean up with a cotton bud soaked in acetone. Tomorrow, brace number 2...

Sides are nearly finished. The final kerfing was glued in this afternoon....

Top carving continues. I've hummed and ha'd long and hard about final thicknesses. Ken parker thins his tops to between 2 and 3mm, he mentions D'Aquisto tops were 2.5mm to 4mm thick. Obviously those were guitars but the string tension is actually very similar. The arch is a bit flatter on mine and the wood is certainly cheaper...so plugging all those variables into the scientific calculator, my finger in the air came back with the following: 4mm around the bridge, 3.5mm around that thinning to 3.2mm at the periphery. I don't know if you can read any of these numbers, but here we are, getting close:

Post #2 in my world's uggliest jigs compilation.... I'm planning on thinning the top till it's quite flexible. Holding firmly without cracking it is therefore a problem. I've taken Ken Parker's beautiful work holding platform which takes several hours of video to explain, and made my own version which took about half an hour to make. It's basically a 6mm sheet of MDF, with a 15mm piece of ply with the shape of the guitar cut out. Some more scrap pieces of 4mm MDF on top of that cut to the shape of the top ensure that the top goes back in the same position. Because the top is still slightly oversized it can sit upside down on the rim. The thing is as it get's thinner an more fragile it really needs support from below. Sooooo......I then filled the space with 3.5-5.5mm polystyrene balls - the ones you use to fill bean bags and such like. So far it's worked really well. The balls are soft enough not to scratch or dent the top, but it seems for the moment to provide enough support. We'll see as the top get's thinner how it works out, but so far I love it!

I love building guitars. I hate building jigs. It's a personality defect I know, but I resent having to do it. So I thought I'd show you a couple of my fuuuugly jigs, that seem to work just well enough that probably I'll never upgrade them. First is the top thickness guage. The guage itself was a cheapo from Amazon. A piece of scrap clamped above the table, and a piece of threaded rod going through a hole in my table. A plastic knob thingamy stops the top from getting scratched. I then write in pencil on the top what the thickness is at each point. It's pretty much a consistent 5mm, so I'm going to go back to the drill press and do another series of holes at just over 4mm. Which strangely is what I thought I did last time, but there you go. That's why you measure twice..... I should also say that pretty much everything I'm doing with this build is copied directly from Ken Parker. He's done an incredible series of videos called Archtoppery, which if you are interested and have a spare 30 hours or so, they are amazing. He's hands down my favourite builder, an absolute genius. Here if anyone is interested: https://kenparkerarchtops.com/archtoppery

I'm working on the inside carve. At the moment I'm doing it all with a gouge. It's probably a bit small (Sweep 5, 18mm in case anyone is interested), but it's an utter utter joy. The grain is tricky. The middle section (marked in pencil) runs opposite to the areas either side. I wake up sweating in the middle of the night just thinking about tearout.....

OK, the carving of the top I'm calling finished. There's still a bit of refining to do, particularly on the cutaway, but I'll do that with sandpaper once the top is on. Turning over I use the drill press to mark a 4.25mm depth everywhere (4mm mdf and a 0.25mm feeler gauge). I use a simple wood dowel with a thin piece of cork on top. Without that the top will get dented from the force of the top being pushed against the dowel. I then drill several million holes to within 25mm of the side (note to self, template #8). Several million more to go tomorrow. I'm exhausted.....

OK round one of the carving is complete. I left it 1mm thicker everywhere on purpose in order to give me a chance to see how the carving was going without risking it getting too thin. Time to get serious. I routed the perimeter down to 4mm, it's final thickness. Time to crack out the gouge and mini plane again. I'm not finding it easy planing it without getting tearout. Wood is like cats fur, it want's to go in one direction. Get it it wrong and the blade can get out under the fibres and pull out a chunk. Carving it is like butter, till suddenly it isn't. It's also a second grade piece of wood, so there's lot's of grain runout, making tearout even more difficult. So far so good though....

Thanks Hellzero for those suggestions. I wondered if anyone had put the BP100s into a bass rather than double bass, there's my answer. I may well come back to you to explore this a bit more. But it's a non-permanent install, is that right? The trouble with the K&K is that it's permanent - they're superglued to the inside of the top. These are prototypes I'm building so it would be good to know I can chop and change the electronics around. Also, I may drop RMC a line and see what they would recommend for an archtop bass. Cheers!

Ok thanks Andy, good to know. Any instinct as to whether the Ghost saddle units are less susceptible to feedback than the more normal piezo strip that goes under the saddle?

Carving in progress. I'm not sure how it's going. It's definitely going to take some practice... 😬

Does anyone have any views on what piezo pickups I should use with this one? The last one has a K&K glued on the inside of the soundboard. I want to try something different to contrast. The obvious options are: Fishman Matrix piezo element under the saddle: https://www.thomann.de/it/fishman_matrix_infinity_vt_narrow.htm or https://graphtech.com/collections/ghost-pickup-systems-kits/products/ghost-bass-acousti-phonic-kit coupled with these elements which I could fit into a handmade bridge: Any one with any thoughts? I know Rob Allen uses a version of the Fishman matrix....The Ghost, I've no experience of....

Contours done, upside down on the router table. Next, carving..