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Reservations about the Lafavre marimba design (Questions from Alan Short)

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-----Original Message-----
From: Alan Short
Sent: Wednesday, 27 February 2008 7:02 PM
Subject: Marimba plans
Hi Jim, and thank you for such a quick and informative reply. I'm going to have a go at these Lafavre marimba designs, and as I am a long standing tinkerer and timber joiner, should be able to knock out something reasonable. Any tips on tuning? I would also like your opinion regarding your reservations on the frame. I have built smaller simpler designs before and would like the challange of an instrument this size, so I will let you know how I went. Thanks again Jim, all the Best, Sincerely, Alan Short.

Hi Alan

I reckon as far as tuning is concerned, you probably have the info you need - its more about the equipment - if you want to tune upper partials or even high fundamentals you really need some form of stroboscopic tuning equipment - visit Peterson tuners on the web!

Frame - well there are lots of design issues. The quality of the manufacture is not in doubt - that looks great. It's a bit tricky to see from the photos because there is not a whole lot of detail, but first of all this looks like an instrument that does not come apart easily. An instrument of this size will certainly not fit through single doorways, or even some double doorways - especially if there is no room to swing on an angle. Disassembly is therefore critical. Even complete disassembly of this instrument looks tricky because of the fact that there are six bolts at each end that probably need spanners as well. The system is ok as far as it goes, but one crucial thing is that you have to remove probably all four horizontal struts to get it apart - at least a pair anyway - it's a bit hard to tell. A good design is one which lets you remove (or just slightly shift) a single strut which gives you the clearance you need to get the big end through a door on an angle. When you are doing three shows a day in different venues this is a real issue - I can tell you from experience. It seems removing the resonators would be quite a process as well - there is no need for all those crazy angles on an instrument that is not so low. There is nothing wrong with the old 180 degree bend at the bottom which means even weight distribution so the resonator banks can just slot in and hang.

This frame is also really heavy by the way!

There are no Diagonals!!! Sure the lower horizontal strut is quite wide but those joints will come under a lot of stress with no diagonals. Speaking of the joints - quite a few of the ones holding the ends to the horizontal sections are at some point held only by the end grain of the timber joining directly to something. It is never a good idea to rely on screwing into a timber end grain in joints that will be under tension like this - it works fine for a while, but over time the end grain is prone to softening - particularly in softer timbers!

I also have quite an issue with the extra diagonal pieces on the horizontal struts - these means that there is timber quite close to the bar under areas which are not the nodes - usually not a good idea. There is probably enough clearance for this to not be a problem, but why design it that way? - it's a potential problem, and I don't see why it's necessary...

The end sections look like they have no issues given their function with the rest of the frame.

Another miscellaneous thought - I have a marimba with bars finished with polyurethane - I wish they were not. I would never do it again. You cannot change it without having to completely re-tune the entire set of bars, and in the most difficult possible way. The coat looks great to start with, but over time a natural oiled finish is much easier to maintain, and can look just as sensational if you put the effort into sanding back the bar faces with fine enough grits.

Now all this - well I don't want it to sound like I'm being overly critical - the fact is that this is a tremendous job, and designing/building an instrument at all is quite a huge effort - especially building it to such an exceptional finish! Also putting it all up on the web is great - above the call of duty! My observations are just that - I have a number of years of experience both building and using marimbas and my observations are based on many of the issues I've seen crop up over the years. I don't know if this instrument is a first for this person, or close to it. It appears to me like it might be. It seems like they have gone to great lengths to research as much as possible and avoid hassles before construction but just lack a little practical experience. I have to say that I wish my first efforts were as considered, and well built! Hats off!

Hope this helps you...
Jim McCarthy

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Gidday Jim, Man I cannot thank you enough for the effort into your reply.
I'm sure you have saved me some time, timber and heartache. I take onboard your concerns regrding the stand, but my gigging days are long gone and the wife has banished all such things to the shed, so not alot of moving is predicted. When I played precussion I made alot of my own instruments, hence the rekindling of interest. (I'll tell you about making a steel drum in the suburbs one day!) Also for the summer months I make a hell of a lot of timber fly screen doors and I'm well set up for mortice and tennon joinery.

I did consider some form of metal tube frame, but size and weight is not really and issue, and I will modify and brace the stand to suit. My primary concern was the stand may have some bearing to sound which prompted my question. You advice is well received and in regard to the resonators, I'm glad to hear your thoughts on shape. I've finished cutting out a set of bars and am begining to rough tune, the overtones are amazing but a bitch to tune, I was also a day off urathane coating the bars, but now I'll try either lanolin or Organoil (Tung Oil), which I use on my doors. I regards to the plans, yes, I was surprised and impressed to find such detail, having once had similar plans for a 3 octave resonator sytle, which I unfortunately lost. While there is a great amount of detail regarding the bars and resonators, there was precious little on mounting the bars to the stand.

Whilst I hope you dont feel oblligated to answer my questions, your feedback is most appreciated, and if you have time I would love your opinion relating to how and what is used to mount the bars, are they in a string or individually mounted? Also I believe we have a far better variety of hardwood species than they have in the US, so this would leave me to believe there is scope to experiment with timber types. Currently I'm trying Ironbark and Messmate, with pretty good results. Have you any species you would recommend? Once again Jim, thanks for your advice, I hope I can return the favour one day, Cheers fornow, Alan

Hi again Alan - once again a delayed reply - sorry - my in tray is getting fuller than my out try despite my best efforts!!

Sounds like you are well set up, and building an instrument because you just want one for yourself.... well you will suffer less frustration, get more joy, and probably a better result - so I'm glad for you. I just can't tell you the pleasure I got from completing my first "serious" project so many years ago which was a contra-bass marimba. I built it simply because I wanted one and they didn't (still don't) exist with that range. I just recently sold the instrument which I hadn't seriously used in over ten years and always took up heaps of space in my home - this was some kind of testament to the sentimental value it had for me (and I still miss seeing it!)

I'm glad to hear you are going with a natural finish - I think you will be happier in the long run. As far as timber is concerned - well the frame doesn't really matter - the same principles as making your door would apply and I'm sure you know more about the properties of timbers than me. Ash is a popular one but for me as long as its not pine I tend to go for the durable but cheaper options. Good seasoned oak makes great main planks for the top parts of the end pieces which get a few knocks - if you can get/afford it. As far as the bars are concerned - well Honduras rosewood and more recently African padoak are the traditionally accepted timbers. Others can work ok - Brazilian rosewood I have heard can be ok but I'm not sure what genus that is - there are often a few variations between popular names and their official genus. Timbers are often misrepresented as I'm sure you are aware. For a full range marimba I would always go for Honduras rosewood given the chance (dalbergia stevensoni) It sounds good and works well across the whole range. African Padoak is ok. It sounds as good overall. In my opinion it is slightly better in the lower ranges but perhaps not quite as good up high. It is especially good for bass instruments - they are low so it sounds good and also because it is cheaper and easier to get hold of big planks. In the top octave + half of a concert instrument though the timber can occasionally sound say 5% worse - not a lot. The main issue is that the padoak is significantly lighter than the rosewood which means that the smaller bars can jump a bit when you play them hard and even displace the string.

On that topic - I have seen one guy who has developed a system of mounting bars on rubber pegs to a commercial/professional grade, but I'm not 100% convinced without the opportunity to try an instrument 1st hand. Pretty much all professional instruments use the tried and trusted method. Bars are drilled at the nodal points horizontally. A string runs through the holes. There is a small flat aluminium or steel peg between each bar with a rounded "open top hole" at the top for the string to rest in. There is usually a short length of thin wall soft rubber tube squeezed over each peg. This system keeps the bars from contacting each other and keeps them off the timber frame. The string is usually a 3-5mm plaited nylon cord but thin cotton "sash" cord can work. Softer but not as strong or easy to repair - the nylon can be melted back together if it breaks. The marimba you saw on the website uses aluminium flat bent at 90 degrees and fixed to the timber under the bar. I'm not too keen on that although its not terrible. I'm just not convinced that aluminium can undergo 90 degrees worth of bend and still be strong enough at the bend point - no matter how well its done. I also think it leaves the bar too high off the frame and if the bar does flex down to the horizontal support it will really clunk on the aluminium. Usually instruments use a thin strip of felt glued to the top of the timber support to temper this extreme case. The pegs are Aluminium flat which have a much thinner bit at the bottom to allow it to be inserted into a pre-drilled hole in the timber. A bit of epoxy in the hole and a tap with a hammer gets it all pretty secure. These string holders are in my opinion the single most difficult part of building a marimba. They are a bugger to manufacture and you need plenty of them! They will not be strong enough at the ends to hold the tension in the string where it turns the corners so you will need steel bolts or pegs at the end of each row of bars.

Hope this helps - feel free to keep asking if you run into problems, I'm always happy to help out.
Jim McCarthy

answers by Jim MCCarthy - 28/02/2008

For more help on instrument building you can email Jim.

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