Beefy Bryn Flat-top

francis - Interesting, Francis. Not doubting your findings at all, but struggling to understand them!

How do the strings know what the back/sides are made of? My simple brain tells me that the same string at the same length should intonate in the same way wherever it is? What am I missing here?

Sorry Rob for this sidetrack!

Keith

Thanks Rob - yes, I get what you're saying, and I realised that, so I probably didn't phrase my query too well, being out of my depth here!

The amount of compensation at the saddle required for correct intonation might well vary by a fractional amount with differing scale lengths, string construction/gauge/tension, action etc, but that it should vary as much as Francis has found on some of his guitars is what puzzles me. What other factors might be coming into play here?

K

About 152 or 28 degrees, whichever way you look at it.  The height is also, of course, adjustable to some extend depending on the height of each removable sub-saddle:



All my secrets divulged in the name of luthiery!

Yep (and trying hard to rip the bridge off the soundboard).

Of course it is - silly me, just working out whether it's first or third angle projection certainly not orthographic...

I can understand that this may be a bridge-thread too far for some of you but I've started so I'll finish.  That's two cliches already.

It was too straight across the top, if you remember, and would need to be curved slightly to line up with the curvature of the fingerboard.  I drew some hatching on the offending area thus:



took my home-made 16-inch radius block in my hand:



and "went for it" as we say nowadays:



Checked the curve with my bit of curvy metal:



and then smoothed off all the curves to where they wanted to be (and got it down under 20g):



whilst cunningly keeping the fissure which is visible around the line of the top e-string.  It's not visible on the bottom and, since the whole thing will be glued and pinned down, I'll think I'll just leave it as it is and repair it if I need to - after all, this guitar is a bit of a test-bed if truth be told.  Now the top is not far off polished - I sanded it and polished it again this morning - so I thought it would be best to get at least some of the polish on the bridge before sticking it down.  Besides, I wanted to see what colour it would be with a bit of polish on it.  So here's the answer:



Yes, I know;  it is a bit acrid greenish but that might look okay in context.  You can't really tell until it's there in situ.  (I have the same problem with planning decorating schemes for bedrooms and sitting-rooms but that's by the by).  Anyway, the answer will have to wait till tomorrow because at the moment I don't want to disturb it since it is well and truly double-sided to a piece of plywood and the polish is way too soft to have cramps applying pressure to it.  Which thought brought me to the caul which I had, as yet, not made up.  So I made it up:





and now I'm just about ready to glue the bridge in place.  I know I will damage the polish to some extent with the cramping, but it's better to have something on it rather than try to start from scratch without touching the surrounding surface.

Well, there you are then;  there was a boredom warning at the outset so I only feel slightly guilty about this evening's offering.

Had to go to town (Cambridge) today - dentist and sourdough-starter amongst other things - so didn't get an awful lot done because I have to use the bus and it all takes a little while.  What I did do is again a little bridgey but we should be moving on to more exciting stuff soon.

Started by peeling the tape off the soundboard:



Now this may look like a nice clean job but, as others have probably discovered before me, the theoretical shape of the bridge is not absolutely precisely to within 0.5mm what you end up with especially when you have a funny curvy shape rather than lots of straight lines.  This means that my bridge doesn't exactly fit the footprint and needed a bit of modification and will need a bit of tidying up with polish after it's attached.  I have learned a lesson and will revert to scribing and scraping from now on.  Anyway, I taped my caul to the back of the soundboard



and cut a piece of oak slightly smaller than the bridge.  This I heated on both sides with an iron until it was jolly hot and then placed it between the bridge and the soundboard to warm things up ready for the hot hide glue:



Last time I used a hot air gun and managed to blast the finish off the soundboard and also warped the bridge itself with too much heat so at least I learned those lessons.  This time it resulted in a very calm and controlled warming up of the relevant surfaces ready to receive the glue:



As you will observe, I used 2 homemade - I believe the correct term is "shop-made" actually - long-reach cramps - they're elm if you're interested - to fix the bridge down.  This was a simple enough set-up to allow me to slide it around till I was happy with the positioning.  Let's hope it still looks good in the morning.  Next up is to make the fingerboard after I have put all the pegs through the bridge - but I can't see myself not trying a bit of tapping and voicing now that the braces have all been locked in by the bridge.  (I'll try to look thoughtful when I'm doing it).  It really is a finished soundboard that I'll be listening to so it should provide the best chance I've ever had to get it right.  Still not entirely confident that I know what "right" sounds like, however.