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Is a lap harp a good idea for me?

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Home Forums Harps and Accessories Is a lap harp a good idea for me?

Viewing 9 posts - 76 through 84 (of 84 total)
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  • #199935
    Elettaria
    Member

    The angle seems to be about 50 degrees in the cardboard mock-up.

    #199936
    Elettaria
    Member

    I seem to be confusing people with the respective relationships here, as two people so far have thought it’s my partner building me a harp!

    My partner is called R.  He plays the dulcimer.  He has no clue how to build a harp, though he’s cheering me on.

    My friend is called S.  They are a designer (yep, that’s their correct pronoun, their gender is non-binary).  Hopefully they will be building and decorating the cardboard harp, and also making one for their partner E.

    E is disabled like me, and they are a good folk musician and singer who is hoping to play the harp, so they’ll be helping out from the musicianship side of things, though not with any in-depth knowledge of harps just yet.

    #199937
    Allison Stevick
    Participant

    I’m not the one to answer if bridge pins are truly necessary, but I do know that the Waring with a straight neck (I know, not as attractive as a curve) uses a straight piece of wood glued to the neck in place of bridge pins. So it’s not that there’s nothing, it’s just that it’s one thin piece of wood instead of 19 more pins.

    I like the shape of your model!

    #199938
    Biagio
    Participant

    :Harumph” said the professor LOL  How can I put this and still avoid eye-rolling?

    Well. I can’t so once more dear friends into the breech (as King Harry said just before getting his head chopped off):

    Here’s the deal…a vibrating string sounds best when it is at about 1.5 steps below it’s ultimate tensile strength (breaking point).  Which translates to around 90% of tensile strength. Different compositions have different properties. Wonder why gut strung concert harps and brass strung clasrseachs break a lot of string in the treble?

    Now you know.

    Those strings are short and thin.  To sound good they must be pretty close to ultimate tensile strength.  We can get away with bigger and badder strings lower down but when doing a design we want to keep how the strings FEEL fairly consistent.

    I trust that I make myself obscure.

    B

     

     

    #199939
    Elettaria
    Member

    Yep, still lost.  Intrigued, but lost.  Or rather, I have some idea of what you are talking about, but no idea how to translate it to the design of a cardboard harp.

    Allison – I just looked again at the photos of the Waring harps and there it is, that little wooden bridge.  Thanks for pointing it out.  It’s not in the book on how to make them, which is lacking in a lot of details anyway.  So I’d need bridge pins instead, then?  The slightly larger Spanish version doesn’t seem to have anything like that.

    Here is a sketch on graph paper at a scale of one little square = 1cm.  (I will cope with inches in quilt planning, but there is a point where they become ridiculous, especially in a country which uses metric.)  There is a gentle curve to the pillar as well as to the arm, with both becoming broader at the join.  (My partner was someone alarmed to hear that if you are a harp, your neck is also your arm and ends in a knee joint.)  Does it look reasonable?  I’ve pencilled in 21 strings at an attempted distance of 13.8mm or thereabouts, although I can’t really do that accurately on such a small sketch.  I’m not getting the lengths doubling at the octaves.

    #199940
    Elettaria
    Member

    Sorry, I was talking nonsense.  The string angle for that sketch is 39 degrees.  Looking at the Salvi Juno 25, which goes down to a low E and uses nylgut throughout, is making me realise that now I’ve curved the pillar, I could change the string angle to get them right up into that corner, and get longer strings.  Should I do that?  The angle will be more obtuse, of course.

    #199953
    Biagio
    Participant

    OK, let’s try to look at this intuitively and ignore little details like pi and the gravity constant; the spreadsheet I gave you does all the computation so you just need to consider the Length for any note (frequency), the string diameter and composition  (more or less equivalent to the Mass).  Here is the Taylor formula again, what is it saying?

    Tension=Mass(2xLengthxFrequency)squared

    Pretty simple if you are a geek like me, maybe not for normal people but intuitively it says that for any string (roll of drums):

    1) If you increase the Mass, either with a larger diameter or a heavier material (gut, fluorocarbon, steel, whatever) or both at once you increase Tension

    2) Holding Mass constant, increasing Length increases Tension

    3) Holding Mass and Length constant, tuning to a higher note (Frequency) increase Tension

    or go in the other direction and decrease Mass, Length and/or Frequency to lower Tension.  We will assume that for any given string the Frequency (note) is fixed (4th octave C for example).  We can start out flying blind or we can use a string design from someone else (yours truly) and tweak it to our desire.

    From here you are on your own, tweak-wise.  Want lower tension? Make the vibrating length shorter. If that did not do the trick, use a smaller diameter.  Or use a lighter material (replace gut with nylon).  And so on.  In general we want things to end up like this:

    String diameter increases from treble to bass

    Tension increases from treble to bass

    Tension divided by length decrease from treble to bass

    Percent of tensile strength (breaking point) between about 70% and 30%

    There are no big jumps in tension

    Those are all parameters built into the spreadsheet and you can check them visually against the charts that are also built in.

    When we plot the result we want to see a nice smooth curve to the pins (or pegs if we leave bridge pins off).  That’s where it all gets annoying: we might come up with a perfectly beautiful design in terms of those parameters, and then see that the result has pins (or pegs) out of line with each other.  We can ignore that or we can make some adjustments in length or string diameter (usually pretty small ones) and see how that looks, tension-wise.

    It is best probably to start with an existing design and just play around until you get a feel for what is going on.  Ignore all that stuff about pi and the gravity constant that Rick discusses – the spreadsheet does those computations for you.

    Biagio

     

    • This reply was modified 7 years, 2 months ago by Biagio.
    #201210
    Elettaria
    Member

    Current sketch 23.02.17

    I finally got back to harp-planning!  We are looking at modifying the Waring, and here is the latest sketch at half-size (one small square = 2mm, one large square = 1cm).  There’s the wooden string rib on top of the soundbox.  No levers or bridge pins, as advised by James Skeen, since he reckons they just mess up the sound on a harp this size.  How does it look?  73cm (27.75″) at its tallest, 22 strings, 14mm string spacing, small enough for me to play in bed, cardboard soundbox as per the Waring harp (though perhaps 1/4″ deeper), and I’m going to have a good chat with Aquila about nylgut vs nylon strings.

    What range do you reckon would be best?  I rather fancy E to E, because E minor suits my voice and it gives you the dominant note for A minor too, but I know G to G is a lot more common.  F to F is probably less useful, since F minor is a long way off being practical in an unlevered harp.  Extra strings are more useful and nicer sounding in the bass than in the treble, but the important thing is getting strings that sound the best on the harp.

    #201366
    Elettaria
    Member

    Since then, Biagio has kindly sent me harp stringing charts and a huge amount of advice, and we are making excellent progress.  We worked out that we can get 23 strings in there, running from F at the bottom to G at the top.  At some point I will figure out how to get the sketch in here, but it’s currently at 76cm/30″ tall.  According to my cardboard mock-up, that should be OK, what with the fairly slim soundbox.

    After looking at the domestic hardwoods available from my friend’s local timber merchant, we have settled on (European) beech.  Apparently it’s as hard as maple, nicely close-grained, and only suffering from little usage because it’s rather bland to look at.  But we don’t need to worry about the grain as we’re painting it.  We were thinking of getting 9mm beech, laser cutting it (which saves a lot of labour and produces nicely sealed edges), and laminating it, doing two layers for the big string rib and three for the neck and pillar.  This is the same thickness for the string rib as in the original Waring design, but 50% thicker for the pillar and neck, which it will no doubt need with four more strings and consistently longer string lengths.  Although Owen from Teifi mentioned in Facebook Messenger that they actually use beech plywood for their student harps, as it’s really strong and allows them to keep the weight down, so I may do a bit more looking into that.  I have been trying to work out what the weight will be like.

    Other issue: stringing material.  A couple of people have recommended nylgut.  It looks like harp nylgut is only available from Aquila in Italy, who have a 50 euro minimum order.  That makes it impractical for getting individual replacement strings, and they don’t seem to be easy to get in touch with, either.  They also sell silkgut, practically the same thing from what I’ve heard, in the UK, but I’m waiting to find out if all gauges of that are available in all three colours, since their stringing chart isn’t the same as the one Biagio has me using.

    Reading through old posts here, some people love nylgut/silkgut, some hate it, the only lever harps it’s used on are the Salvi Juno range and those apparently have Issues (more about construction, from what I’ve heard).  So I’m not sure what to go with.  When I had a relatively low-tension fluorocarbon harp, the Camac Hermine, I found the top few strings pingy  and the bottom couple of KF strings were too loose.

    What I want in strings for this harp:

    * nice warm tone, though obviously without getting muddy

    * affordable, this is meant to be a budget harp

    * available in the UK, or else in Europe if there is quick, cheap postage for small quantities

    * less bothered about volume.  If this is a quiet but nice sounding harp, that’s fine with me.

     

    Ideas, O helpful people?

Viewing 9 posts - 76 through 84 (of 84 total)
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