Cupped board - use or not?

[hillbillybass]

Amateur builder looking for advice. I've just discovered that the Queensland Maple board I was planning on laminating for a double bass neck has some cupping. Do I plane it flat and use it, or rack it up as part of the learning curve, put it aside and look for another piece of wood for the neck?

Cheers and thanks,

Michael

[kiwigeo]

I've just made up a bunch of queensland maple steel string necks. None of the blanks were perfectly flat but a bit of work with a plane and they were soon good. Make up some winding sticks and get a bit of practise using same and then get busy with a plane and make some shavings

[hillbillybass]

Thanks Martin, much appreciated. Another amateur question - what are 'winding sticks' ?

Cheers,

Michael

[demonx]

Hard to tell from the photos but it looks like it's flat sawn and a bit thicker than inch board. I assume you're ripping it and turning the pieces to make the grain closer to the quarter for the neck you mentioned.

I think you'll find that if you rip the pieces as the board is now, the cupping will be very little, then dress the individual pieces for lamination. I wouldn't thickness the piece as it is as it's just waste.

[kiwigeo]

Thanks Martin, much appreciated. Another amateur question - what are 'winding sticks' ?

Cheers,

Michael

https://en.wikipedia.org/wiki/Winding_stick

You wood cupped....winding sticks used for twisted wood.

[hillbillybass]

Thanks Martin, I'll make up a set. Cheers.

[hillbillybass]

Thanks Allan, Yes the board is back sawn and 37mm thick. I wasn't planning on ripping, rather I was just going to cut two pieces from it and glue them together to get a thickness of around 65-70mm initially (I may have to glue extra to make up the ears of the scroll). So I'm aiming to get closer to 'quarter', but won't really get to full quartersawn.

Michael

[blackalex1952]

Can you dress the timber to get rid of any wind and cupping and still have the thickness you need? It appears that you need only dress and true one side of the board to get the join, then work the finished neck blank after that. Hand tools tell us more about the wood and the grain than power tools as we work...listening is an art... A centre strip will take care of thin material anyway...I would have the tendency for this job to put some nice contrasting veneers either side of the centre strip. You could ebonise some maple or other dense wood to make veneers. (vinegar and steel wool) Can you post a better image of the end grain please? (Dressed without saw marks)
My rough sketch shows a way of getting neck stability with quarter the sawn on the outside of the finished neck, the pencil lines indicate wood grain. Are you monitoring/contolling the Relative Humidity for this build?
You probably know a lot of the things people will tell you on this site, but it just occurred to me to make the following point. Always work to a centre line when building, for both body and neck. cheers! Ross

[hillbillybass]

Thanks Ross, I appreciate your feedback. I think I can dress one side of the timber flat to get rid of the cupping and retain enough thickness. The plan is indeed to only dress one side of the board, then cut and join. If I need to I'll add a centre veneer of blackwood or another wood. Thanks for the idea of contrasting veneers, that might be another possibility too. Epiphone used to do this on the necks of some of their plywood double basses.

I'm a fan using of handtools over power tools, although my skills need improvement. I'm learning as I go and I've given the end of the board a tidy up tonight to get a better picture of the endgrain. I'll need the full width of the board for the neck heel (and probably a bit more), so I've included a sketch of how I thought I might join the board. But I'm only a beginner, so very open to suggestions. Based on feedback so far I'll probably use hot hide glue for joining the boards.

I haven't been monitoring relative humidity, but I was planning on holding off on gluing things like ribs, etc, until the weather is warmer. Should I monitor humidity? What should I aim for? My shed is pretty cold and damp in winter (mountain air), but I may be able to bring parts of the build inside to do.

Thanks again.

Michael.

[blackalex1952]

Instruments should be built at a lower relative humidity (RH) than they will be at in normal use. This is generally considered to be 45% which I believe gives around 8% moisture content in the timber. Relative humidity is a term used to describe the amount of water that air can hold at a given temperature. As temperature drops, the RH increases until the dew point is arrived at which is when excess moisture in the air (the air being at 100% moisture content) condenses out. There are plenty of posts here on the subject if you search for them...but start with the Robert O'Brien one on RH. El cheapo RH indicators vary in accuracy, but if you search you will find how to calibrate an RH meter using a wet and dry bulb thermometer. I borrowed one from the local high school science lab then used an RH calculator which I googled. It is worth calibrating hygrometers at the RH which you want to measure the most accurately...in our case 45%. There are a few ways to control humidity. One is with a dehumidifier, but these use quite a bit of electricity. There is a domestic one which uses less power than the one I have, But I can't remember...bla bla, just do some research. The other way is to heat the air, so that the RH drops. But of course if you heat a room which is not well sealed, eventually the hot air will stabilise to the moisture content of the air outside.
One reason that low RH body assembly is essential is that instruments can be designed to absorb moisture and expand a little. But if they shrink..that is a recipe for disaster. As for necks, remember that the fingerboard is a much denser timber than the neck wood, so moisture absorbtion and the consequent wood movement is different for the two species. A simple, not so accurate hygrometer can be made by gluing two quite disimilar veneers together in a rectangular strip, mounting one end of the strip in a block of wood with a board at the back and different RH's marked on the board. The strip bends as the different woods absorb moisture at different rates.
https://www.youtube.com/watch?v=Y_jaWKEGhoc
https://www.youtube.com/watch?v=XhlyzoeA_7E

[blackalex1952]

Here is another offering...maybe surface the other face so that you get what I have tried to sketch..the heel will be as in the drawing, the neck profile will be closer to end grain all round after shaping.

[hillbillybass]

Thanks for the info on Relative humidity, Ross, I'll get reading. Thanks also for the sketch. Good point about the endgrain and neck profile. Cheers.

[blackalex1952]

Just had a look at my double bass here....the grain goes at roughly a 45 degree angle in the neck. Ii is European maple so a pretty stable timber. Just remember, I'm not a double bass builder....but from my experience, there are a lot of bull fiddles out there which have a repair where the neck has broken off at the top of the heel - always in the same place. I have repaired a couple myself over the years. A laminated two or three piece neck would help strength wise there in my opinion.
One other thing, the Wood Database is a good resource, there are others as well...http://www.wood-database.com/
The dried tangential and radial shrinkage data is good info for suitable luthierie timbers, along with all the other data there if you end up getting into it. Understanding Wood -Hoadley is a good technical book for understanding wood as well.

[simso]

Here is another offering...maybe surface the other face so that you get what I have tried to sketch..the heel will be as in the drawing, the neck profile will be closer to end grain all round after shaping.

That would be a nice strong neck

Steve

[curly]

G'day Michael . Bring the board up when you come to get the other bits . I can buzz it flat no worries , no cost . It'll take about 20 seconds on the big barker buzzer !
Thanks
Pete

[hillbillybass]

Pete, that would be awesome! Thank you, you've made my day!

[hillbillybass]

Thanks Curly Pete for flattening that Queensland Maple board for me today. Also for supplying the rest of the timbers for my bass build.

Thanks also to everyone for all the great feedback on how to go about this. Much appreciated.

I've got the boards inside (where the relative humidity is around 45-55 % when the central heating is on) & I'll get them ready to laminate with a redgum centre strip over the next week or so.

Cheers.

[kiwigeo]

.... I'll get them ready to laminate with a redgum centre strip over the next week or so.

Cheers.

Michael,

I did a classical guitar neck a few years back with a red gum centre strip. One thing I found was that when I was working the back of the neck with any sort of cutting or scraping tool the Fijian mahogany worked smoothly but the red gum got chewed out regardless of what direction I worked it.

[hillbillybass]

Ah. Thanks for the heads up Martin. Did you find a workable solution or did you have to go with something else?

Cheers,

Michael

[kiwigeo]

Ah. Thanks for the heads up Martin. Did you find a workable solution or did you have to go with something else?

Cheers,

Michael

I had to do alot of sanding in the end. Not sure if I'll use redgum again...

[curly]

That red gum was reliatively mellow . Still short fibred, interlocked and figured ! But reliatively mellow and even to work . I'd be confident personally so long as you've got good tools and they are sharp . I agree generally though , red gum can be pretty ornery!
Thanks
Pete
Curly timbers

[hillbillybass]

Thanks Pete, it's all great learning for me. Still going ahead with the redgum. If it doesn't work out I'll try something else. Cheers, Michael

[hillbillybass]

I went with redgum. Tricky to plane and dress, but not as bad as I thought it would be. Needed a fair bit of sanding though. Anyway the boards are glued.