7 string, medium scale bass in the design process.

[Micah Covington]

I built a couple of basses years ago with the help from this forum. I hadn't really planned to do any more, though I have done setup and modification to other guitars I have owned since that time. This ended last week. I vacationed in Oregon and found an absolutely gorgeous piece of myrtle large enough for a 1 piece body blank. It's spalted in places and has a really good figure. It wasn't marked with a price, and it had some fairly large holes on one side which go almost all the way through the 2 inch thickness. Because this wood was "unuseable" I got it for $20. Playing around with it I lined up one of the holes with the control cavity and got the rest of the body shaped around the remaining holes.

I had been looking for a short scale, six string bass (Fender VI type). I was thinking of making one, but I like having a low b string as well. I was thinking about making a 7 string, medium scale bass with a 31 inch scale length. 31 inches is about halfway between my Ibanez Mikro and my Fender Jazz which are the two basses I play the most currently. It will be tuned B,E,A,D,G,B,E

I was thinking of putting the tuners in line with a reversed head stock so that the B string would use some of it's length getting to the tuner. This, combined with stringing the strings through the body, would hopefully allow me to use 34 inch scale length strings, as I imagine that low B strings are hard to find in short scale. I have started purchasing my strings individually as I like custom gauge sets more than what is typically available where I live.

Recent budget changes have forced me to redesign somewhat. I have an older Schecter Stilleto 4 string bass that is in horrible condition. It will be loaning it's EMG HZ humbuckers to this bass, probably through a volume knob and a varitone. I am unsure about the varitone. I like my guitar electronics as simple as possible, as basically, I find one sound I like and stick with it. My fender has all kinds of electronic modifications, I have left it set on 1 setting since about the day I finished it. The schecter may be loaning it's trussrod as well if I can find a way to remove it easily.

I will post pics of the wood I scrounged when I get home. I got the body blank, a myrtle neck blank/fingerboard blank, and some random small pieces of ebony for less than $50. The ebony will become the truss rod cover, the nut (planning on using a 0 fret), the bridge (Maybe, still working on this), and the knobs for the electronics.

Are there any special design considerations I should be aware of while designing a 7 string bass? The biggest downside that I can think of is that the body will need to be somewhat heavier to balance the extra weight of the neck (7 tuners and a wider neck). This will not be particularly fun with my current back issues.

I will probably need some help designing a bridge. I was thinking of anchoring the strings through the body and making individual ebony saddles which would be mounted directly on the body. These would not be glued on, but would be held down only by string preasure. This would allow me to adjust intonation; however, I think this would make adjusting for height a pain in the back side. Another option would be to carve a saddle similar to an acoustic guitar saddle and screw it into the body so you could adjust the height by lowering or raising the screws. The disadvantage here is that then you cant really adjust the intonation.

The myrtle wood neck, body, and fretboard are all a very light color, with intermintent spalting and an almost quilted figure in some areas. The truss rod cover, knobs, nut, and saddle will all be out of ebony which has not been stained and still has some lighter streaks in it. The ebony is very dark, but the pieces they had available where not readily suitable for wood working as they had not been surfaced in any dimensions. They were basically very rough offcuts from previous projects. I got them for $1 a piece.

String spacing will be interesting to lay out. I used to love as narrow a string spacing as possible. Now I prefer a little wider, but still fairly narrow spacing. Without drawing up plans I assume my nut will be approximately 2 inches wide. I want to keep it narrow not only for my playing comfort, but also to help with the weight.

I am considering designing this as a single cut away bass. Normally I do not like single cut aways on basses, but I think the additional wood at the body end would help to balance the larger neck.

Is there anything obvious that I am missing? Any advice y'all can give me? I will try to keep updates on this forum so you can see my progress. Thanks a lot.

[Micah Covington]

I'm having trouble posting pics.

[Peter Wilcox]

Have you read this? http://www.mimf.com/phpbb/viewtopic.php?f=19&t=1656

[Hans Bezemer]

Micah,

I'm just an amateur, so fwiw:
- I think your design sounds good.
- I use a .145 string for a appr. 30 inch scale (seven string!) guitar. I cut the string down to a bit longer then I need it and then unwind the outer string from the core. The core will go through the tuner. This works fine.
- Basses with 5 or more strings have two trussrods, or one trussrod and carbonfibre reinforcements. You can make a low-budget martinstyle trussrod with stuff from your local hardware store.
- I've experimented with a simple single loop low-z pick-up design. http://www.mimf.com/phpbb/viewtopic.php ... 118#p23047
This will give you a simple, low-budget, but good sounding alternative. There are two downsides: 1. I think this concept is patented in the US, so you can only use it for your own use. 2. you need a mic-to-line signal converter (appr. 20 dollars).

Good luck with your build and hopefully you can send some pictures.
Hans

[Micah Covington]

I've got two EMG HZ pickups from an old bass. They have blade magnets in them so they will work for any string spacing that fits within the length of the pickup. I've almost finished the body. I need to rout the neck pocket, and drill holes for the strap buttons and electronics. The control cavaty and the the pickup cavaties are routed.

One question. I removed wood for the pickups using a drill, chisels, and a router. One hole ended up a bit too wide. You cant see it from 4 feet at all, but any closer and it's pretty obvious. Any ideas on how to fix this? I was thinking of either filling it somehow or cutting it more and making it look intentional. Either way, I will probably paint or stain the inside of the pickup cavaties so that they wont show up very well. The other pickup fits just about perfect.

I still need to figure out what I am doing for a bridge. I have some ebony and brass pieces that I am trying to figure out how to make saddles out of. The easy way would be to do it like an acoustic guitar with no adjustment, but I would prefer not to do it this way.

I really need to start on the neck, but I am hesitant to do so. I'm finding that a table saw would be really helpful at this point, and I think it is next on my list of tool purchases. So far I've done the majority of the work with a jig saw, a band saw, a belt sander, a chisel, and a belt sander.

[Hans Bezemer]

Maybe you can glue in a shim in the pickup cavity, making the gap smaller.

I made some necks by rough cutting it with a jigsaw and then finishing it with a router.
For what do you wan't to use the table saw?

Please post some pictures of the progress

Good luck!

[Micah Covington]

Okay, I promise I will get pics up sometime in the near future. Is it okay if I just post links to my photobucket account?

Got a wild hair yesterday to try to make a headless bridge. I've been looking at a few different DIY designs. In it's most simplistic terms it seems that a headless bridge could basically be a screw or bolt with a hole in it, set vertically into the wood behind the saddle. Lock nuts or some other method of keeping the string tension from rotating the screw/bolt would need to be used.

I was looking at all kinds of hardware online yesterday trying to find something that would work. A threaded clevis pin would be awesome, unfortunately no one makes them that I can find. "Spade bolts" look like they would possibly work. They are just a bolt with a flat vertical extension off the head of the bolt. This extension has a hole in it. Wrap a string as tight as you could around the bolt, and thread through the hole. Tighten the bolt into recessed threads. Inexpensive workable headless bridge.

[Hans Bezemer]

Did you noticed the wingnut-bolt tuner option? http://cyberferal.com/UncleBob/design.html

[Micah Covington]

So are the strings just tied through the wing nut, and then tightened to pitch? I assume the ball ends are held at the neck end. Interesting. I wonder how stable the tuning would be with these. They are inexpensive enought that I could mock up a set and see how they work out. I may try this.

[Micah Covington]

Guitar as it currently is, though I have carved the top a little bit more since the pic.

[Hans Bezemer]

Micah,

I've tried this type of tuners and they hold up pretty well. But I don't like the look of it. There are some similar designs that look better, you might want to look around at this website: buildingtheergonomicguitar.com There you can find some diy headless tuners.
You can also consider to use regular tuners but mount them on your body. If you do a google search on "headless guitar with regular tuners", you'll get some examples.

Btw, that's a nice piece of wood you got there.

[Micah Covington]

I was looking on that website yesterday at some of the designs. I have a bunch of bass and guitar tuners on hand, so i may just end up mounting them on the body. The wood came from a scrap lumber pile at a myryle wood factory outlet in oregon. Because their were several large holes in the wood they marked for $35. I got it for $20 after complaining about working around the holes. I got a neck blank and fingerboard, as well as some ebony scraps for knobs, trussrod cover, etc. The wood is flamed and spalted in places.

[David King]

I would suggest you just spring for the ABM single string headless tuners. They aren't too expensive if you can order them direct or know someone with an allparts account.

[Micah Covington]

Update: Last night I did some chisel and scraper sharpening, and then some scraping on the body. I'm going to clean up the pickup routes a bit tonight. Everything is on hold while I wait for my new bandsaw blade to come in the mail. I have to resaw my neck blank to get my fingerboard. I'm actually pretty excited and nervous to do this. My previous instruments were either pre-fretted or fretless.

I found a source of router bits that are .6mm wide and fit into a 1/8th collet. I'm thinking of ordering some for my fretwork. Stewmac lists their frets as being .58 wide, so I figure the .6 will work just fine. I'm thinking of making some sort of overhead router sled to use for fret slotting. The router bits come in a 5 pack for just under $30, so i figure this is probably the least expensive way I can come up with a good fretting method. I already have the router. Otherwise I need to purchase a fret saw, and buy/build a jig for it. Does anyone else use a router/dremel/rotary tool for fret slots?

The body is almost finished except for final sanding. I need to finalize my plans. I'm waiting to do the neck pocket until I finish with my neck, as I want to ensure a proper fit.

I'm thinking of wiring my EMG HZ pickups into a blend pot with some Piezo disks. I probably will not put an on-board pre-amp in the bass, as I have a good foot pedal pre-amp and like to keep the controls on the guitar simple. I am also thinking about having the EMG's hooked to a blend pot as well.

[Micah Covington]

I was reading up on friction pegs and I came across the following statement.

"on bass guitars, where string tension is extremely high, larger, heavier-duty machine heads than those used on guitars are used."

I was under the impression that the treble strings have greater tension than the bass strings. This is confirmed (To me at least) by looking at string packages which list the tension of the strings. Is this true? Pretty sure that electric guitars have more tension on the neck than bass guitars.

[David King]

Micah,
Carbide router cutters in that size need a very precise spindle with 0 runout or they will just snap off. You'd have to test hundreds of dremel tools to find one with no runout.
Most routers ought to be able to work but the better brands will do better. You'll need at least 35-40,000 rpm and 5-10 passes to each fret. You might actually find a hand saw faster.

Bass strings run in the 40-50lb tension. Guitars strings are in the 15-20 LB range. D'Addario has a string tension calculator on their website.

You will probably not be impressed with "passive" piezo disc pickups.

[Hans Bezemer]

Micah,

How is your bass coming along?

[Alexander Higgins]

Amazing piece of wood! I'm curious why you didn't cut a neck pocket before contouring body. Wouldn't that have been easier?

[Micah Covington]

Okay, did some more work to this thing. I will post pics tonight when I get home from work. I am dropping the headless idea, as well as the 7 string bass idea. I'm making a bass vi type instrument since I have wanted one for about two decades now. To save time I ordered a premade guitar neck that isn't fretted. It's coming in the mail. I have almost finished the body. I carved the top more with a sanding wheel on an angle grinder. I need to smooth out the back side just a little bit more. I'm preparing to cut the neck slot and to do the fretting.

I love the wood figure. The back of the blank had a pretty soft rotten spot near all the spalting. When I started carving out for the controls large chunks of wood started to come out. As a result, the rear cover will end up being considerably larger than I had wanted it to be originally, but oh well. Also, I have mixed some two part epoxy and coated some of the softer areas of the body.

My research on Bass VI instruments has shown that a lot of people complain about the low E string not having enough tension, and they blame the scale length of the instrument for this. I believe that this is in error. I own a 28inch scale Ibanez Mikro bass with a low E string that is fine. The problem is not the scale length, it is the string gauge. To solve this, I plan on using 5 guitar tuning machines and 1 bass guitar tuning machine. I will have to drill out the bridge a bit to fit the larger low E string, but if I can fit a .105 or .100 in I think I wont have any problems with low string tension.

[Micah Covington]

Alexander,

It probably would have been easier. I would give you a reason why if I had one. Chalk it up to poor planning and a learning experience.