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Bass design question

Discussion in 'Setup & Repair [DB]' started by Chasarms, Jul 19, 2005.

  1. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA
    I have settled on a plan for a bass. I will be using the Tarr model bass from the selection of plans produced in conjunction with the Chandler book. I have started the layout of the MDF mold and after drawing it out and seeing it in life size, (as well as looking at the plan itself) I don't really care for the shape. I want to modify it slightly.

    So, if you look at the two illustrations below, (from the actual plans) you see that I the original has higher, more squared shoulders and my modified shape calls for steeper shoulder with a more feminine look.

    To me the aesthetic difference is huge, but I don't want to kill the design for the sake of looks.

    So, when I tweaked this in photoshop, I just stretched the top to steepen the shoulders. It reality I would have the option of stretching the plan or simply cutting the shoulders in for a overall smaller upper bout.

    For those willing to answer, I ask:

    What are pros and cons of each approach?

    Specifically, would either approach compromise the general design to the extent that it might be structurally questionable without other significant mods. I certainly don't want to stray from the general model so much that I have to significantly modify the existing supports, bass bar, FF hole placement, etc. If so, I'd rather just build the Chandler Tarr model as is.

    Attached Files:

  2. I see more differences than just the narrowing and the upper bout stretch. From a design point of view the most important one I see is that it appears that the bridge position is shifted somewhat to a relatively lower position on the belly. If you change this relationship, you may need to also alter the string length or neck length to maintain an E flat neck or D neck design. I don't think structurally the two designs are much different though. The ribs might be a little stiffer in your redesign because the degree of arc is overal a little less;- from the point of view of structural integrity, I see no disadvantage in that.

    You could adjust the bridge position and f holes back up, or if you want it to be where you have it now, you could measure the string length from the bridge to the anticipated neck heel position and calculate a new string length and neck length that is consistent with your new body shape.
  3. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA

    I don't want to deal with all of that. If I end up with a BSO, it want it to be because I can't build, not because it was destined to fail in the first place. Not that I couldn't calculate out all the changes, but I really want it take out as much of the guesswork as I can.

    It looks like the best solution may be to simply cut the shoulders in to soften the lines. It would result in less overall air space in the cavity, but it looks like (by penciling on the the smaller copies of the plan) that I can cut the shoulders in without changing the position of of the blocks or the dimensions of the spine of the bass.
  4. arnoldschnitzer

    arnoldschnitzer AES Fine Instruments

    Feb 16, 2002
    Brewster, NY, USA
    I agree. But you may want to rethink the bass bar position as shown. The bar needs to cross several grains of topwood, and your drawing shows it nearly parallel to the center line. If it runs parallel to the topwood grains, you'll have a bass bar crack in no time. Chandler's book has some good stuff in it, but don't assume his way is the "right" way.
  5. 1st Bass

    1st Bass

    May 26, 2005
    Forest Grove, OR
    There's about 1" of slant there, as far as I can see--or a little more. That would cross eight or ten grains, at least, if he has coarse-grained wood-- how many would you suggest? (And actually, usually the fine grain is at the center of the bookmatch, so I'll bet he's crossing three times that many.)

    How do you determine the correct slope of the bassbar? do you use the same formula as for a cello? Or something else entirely?

    Several times I have read a post saying approximately what you have said about Chandler's book, and plans-- but where can we find good information with which to correct them? There does not seem to be an abundance of written material on bass-building.

    This is something I have been trying to find out for a long time.
  6. It does get tricky when you start changing things around. Pretty much the reason I have a bass on the drawing board and not under construction, despite all the encouragement I've been getting here to "get on with it". I'm using 4 string plans to build a 5-string. At least now I have a working 5-string to study.

    If you reduce the volume on the upper bout, you could probably make it up somewhere else in the outline, or by increasing the rib depth very slightly overall. I think that is easier to do and less consequential than changing the relative position of the bridge. I don't know if you can do it in photoshop, but in TurboCAD it is possible to accurately determine the volume within a 3-D drawing and evaluate those types of changes to some predictable degree. That is an easier program to use than AutoCAD, less expensive also. I'm just getting the hang of it, but it really feels like a real design tool. And you can carve the bass virtually before you start cutting up the wood. If you make any big changes, it could help you see most of the implications ahead of time. It is a professional grade design/drafting program and takes some time to learn to use, but all of that time is time saved in the long run.

    Also, I just looked at the H.S. Wake book's plans and the upper bout on that design is more tapered than the original plan from Chandler. You could probably use those plans without changing anything and get a similar shape. Wake built many violin family instruments professionally. The site by Bob Hitchings shows a DB he built by Wake's plan following it closely and has many construction photos.
  7. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA

    Thank you Arnold. I am making no assumptions. Right now, my idea is to document the process using some personal webspace that I have. As things progress, I hope to gather as much help as I can from the TB group.

    It is going to take a while. If it takes you guys 600 hours, I am guessing it will take me three or four times that. My goal over the next month or two is to complete the form and begin addressing the needs to make a rib bender, etc. Once I get the form shaped and assembled, I'll probably launch the site.

    End of 2006 is pretty optimistic for a playable bass, but I will keep every one up to date.
  8. Chas, just a bit of advice, don't get into analysis paralysis :) . It sounds like you got things figured out though. Keep us posted and if there is anything I can do to help you, PM me.
  10. Chasarms

    Chasarms Casual Observer

    May 24, 2001
    Bettendorf, IA USA

    Thanks for the link and advise on the Cole bass. It is almost identical to the drawing I outlined and modified from the Tarr plans. This is the closest thing I have seen to what I want to end up with.

    I really would like to end up with a D neck, only because my Shen is a D. My Shen also has a 105 cm mensure, so that would be a nice touch as well.

    I also like how the ribs narrow gently and softly to the neck block rather than a more pronounced break angle often seen on flatbacks.

    I will definitely spend some additional time with these photos as the bass shapes up.
  11. Briggs worked with Tarr until pretty late. This bass would have been built one year after W. Tarr died. There are some basses labeled "Briggs & Tarr" which I have read are Briggs and Shelley Tarr. To me the Attrib. Briggs on the CB site looks more Tarr-like than Cole-like, as does the Briggs on the Knooren site which was built in the late 1880's while Briggs was in the Tarr shop. The only thing is the double purffled back which is like the Cole. Seems like W. Tarrs and Briggs look a certain way, and Coles, Tarrs made by Cole?, and basses by J. Tarr look another way. There was probably a lot of incestuous building among the various shops in the North based on all the similarities. Cole was definitely competing with Tarr for business from the middle 1800's on, since he set out on his own fairly early.

  12. Damon Rondeau

    Damon Rondeau Journeyman Clam Artist Supporting Member

    Nov 19, 2002
    Winnipeg, baby
    They also made lawnmower engines.
  13. Doesn't Clapton play a Briggs & Strat?
  14. Kenny Boy...did you see that Bernadel that they said they found in a castle wrapped in it's original papers???
    On the Knooren site.
    Do you know anything about that...tell me..I'll be in the bathroom!
  15. Tbeers


    Mar 27, 2005
    Chicago, IL
    A D neck is a crutch, in my opinion. One of the easiest basses I ever played had almost an Eb neck. Besides, what kind of self-respecting bassist finds D by sliding his thumb down until it won't move anymore? If you're relying on the neck as a point of reference, how will you ever succeed in thumb position? Ah well I could rant forever, this is just one of those things that has been pounded into my head in classical lessons.

    The bottom line, though: this is your first bass, you have many other more important things to worry about.
  16. Umm....Yeah. I think most do, or they find Eb or what ever happens to be there. Cellists do it, violin players do it too. Everyone uses physical points of reference. The ear and practice are ultimately what determines the exact placement of course but in a FFF Symphony situation where you can't hear jack sh%t over the brass, it's comforting to know you are basically in the right place. The Eb neck is an arcane holdover from the days of gut frets. Most modern makers, German and Eastern European included, that know what the Heck they're doing use the D neck. It's the standard. Deal with it.

    Jon Neuman
  17. T, this isn't his first bass;- it is the first one he's building. :smug: He wants to build it right, that is, with a specific note reference at the neck heel. It's not about playing, it's about building. Good builders build in reference points, quite invisibly sometimes whether better players need them or not. On my bass, the finish starts at the scroll end just where half position thumb would be. At the other end, the finish starts right where the thumb would be for the "D" position. One can feel these points very easily. I appreciate what you are saying, but from a builder's standpoint, you want to do it correctly.
    Yeah, but that arcane holdever makes a great jazz bass to use with horns that are usually in E-flat, B-flat, F, etc. At least you have a solid reference at the neck heel for those notes. If you holdover an arcane feature long enough it will find a new function. Perhaps that's why a lot of "Bohemian" jazz basses like my circa 1989 plywood Lidl have an E-flat neck.
  18. That's an added bonus for Jazz that I hadn't really considered. Actually with gut strings, back in the day, the longer string length probably also allowed a better response from the bass, but with a D neck, to find Eb, all you have to do is find D with the first finger and finger Eb with the second. With my thumb at the heel, I can reliably find all notes from D through octave G. The brain remembers the space between the thumb and the first finger particularly well, so you find the D position and then stretch to find the others. The difficulty with the Eb neck is that it's hard to find D with out back stretching. The D feels like it is out in space somewhere. Even so, after about 15 minutes I can play just as in tune on an Eb bass as a D neck one but I have to keep reminding myself. To me, placing the crook of the neck at exactly one third the string length (D) is most logical.

  19. I think with the E-flat/ D thing all of it is really what you get used to first. I had no trouble finding D on the E-flat neck because at the time I had no basis for comparison;- I had formed only one muscle memory pattern for that note, but I also developed one for the E-flat at the heel. It was too easy to jump to the top of an arpegio in B-flat and E-flat to not just go for it. Well now with the D neck I have had to totally retool stuff like "A Night in Tunisia". Perhaps at some point I will be able to go back and forth without a problem, but it is somewhere down the road.