Creative and Unique Control Cavity Covers?

Discussion in 'Luthier's Corner' started by BassHappy, Jun 5, 2016.

  1. Bruce Johnson

    Bruce Johnson Gold Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier
    I would use metal for the cover, probably aluminum. There are lots of interesting and elegant ways that you can decorate aluminum. There's acid etching, like 40hz described, laser etching, waterjet cutting (for intricate grillwork), and all kinds of architectural finishes. You've seen James Trussart's instruments, right?

    The metal cover will be durable and light weight, and conductive if you want it to provide shielding too. If you want to use one of those laser cut wood pieces, I would epoxy it onto an aluminum plate, for the same reasons.
    BassHappy likes this.
  2. fhm555

    fhm555 So FOS my eyes are brown

    Feb 16, 2011
    While it is kinda sorta plastic, a sheet of carbon fiber is (relativly) inexpensive and looks very high speed when shaped into covers and brackets. It is also available in a lot of different colors and weave patterns so you could choose something that fits your color scheme with an open or multicolor weave.

    Also, materials aside, think about making a nice cover held in place with magnets only to wind up chipping up the body or cover or both, prying it up when it's battery time. To avoid that, think about doing something like a small flush fitting insert in the cover that was threaded for a small bolt to make removal simpler, or get really creative and come up with a tool unique to the cover like a tiny twist lock and key to pull the cover up with. The downside to the unique tool is what happens if the tool ever gets misplaced, but for an old machinist like myself, that kind of stuff really blows my dress up in a big way, even a metal lined coin slot so you could pop the cover with a dime or quarter would win you tons of wow factor points from folks who love unique solutions to common problems.
  3. Hey Ping

    Yeah, those are really nice. I always like the grain matched stuff as the best solution. I just realized that since the bodies are still clam shells and not glued together yet I still have the option of grain matching the mahogany! All I have to do is carefully cut the 4" hole in the back center of the body and then make a support ring on the inside. Hmmmmm, another option....

    I was successful in designing these basses without a cavity at all - but now that I have to have batteries I am re-thinking it. Would rather tuck the battery away behind a nice cover than have a nylon/plastic battery holder. But that is just me.
    Last edited: Jun 6, 2016
  4. Hey Bruce

    Thanks for weighing in! Yeah, epoxying to an aluminum cover is a good idea if I decide to go that route, but using aluminum is a good idea too. I just started wondering why control covers can be so ordinary when it seems like a decent opportunity for a little flair. I have seen tons of Trussart stuff, my client Marc Copely is an endorser, but I don't remember seeing any photos of the back covers. I will head over there now.
  5. Thanks fhm

    All really good ideas and a great reminder on the practical side about making it work easily and care-free. There is a lot to ponder and that is exactly what I am looking for. A unique solution to a common problem. I was even thinking of using a tiny hinge. Thanks!
    fhm555 likes this.
  6. Hey Means

    I am totally with you. That is a good idea to make them two ply. I think at this point, I would like to make kind of a signature plate and I haven't gone clear yet on exactly what the design needs to be. I am even thinking leather or snakeskin or even ostrich might be nice.


    As soon as I go clear on that I will have a better idea in which direction to head. I mean, doing a 4" circle is a piece of cake with the hole cutter at the shop where I work - whether aluminum or wood, but I really like Bruce's suggestion. I think maybe using wood or even leather and epoxying it to the aluminum would give you both shielding and strength. I am no scientist but it seems to me like that would also keep the wood in check against moving or warping - if I decide to go with wood. Now that I have realized that grain matching is also an option - I may go that rout. Pun intended...

    So, as always, it's a work in progress....But thanks to everyone for all the great suggestions.
    Last edited: Jun 6, 2016
  7. brianrost

    brianrost Gold Supporting Member

    Apr 26, 2000
    Boston, Taxachusetts
    Also my favorite, esp. when the wood is highly figured.

    Now do that with magnets instead of screws and it would be perfect :thumbsup:
    BassHappy likes this.
  8. Means2nEnd

    Means2nEnd Supporting Member

    BassHappy one of the ways I buy tops or for accents under figured tops is to buy acoustic back and side sets. There are a few great sellers on eBay where I have bought wenge and you get bookmatched set for a top or a nice layer under another top 3/16" to a 1/4" and then with the long sides that come with the set I glue them together and make my control cavity covers.

    Like this... Guitar Luthier Tonewood WENGE Acoustic BACKS SIDES SET

    I have bought like 5-6 sets from this guy some really cool stuff and some basic stuff like the wenge listing. It's perfect accents and all kinds of ideas. You glue two of those sides together wenge, bubinga, maple, rosewood whatever it's not going to move that I have ever experienced they are like iron with a finish on them.
    BassHappy likes this.
  9. I've always wondered about buying acoustic sets like that. How big are the backs usually? Is there a standard size?
  10. Hey Means

    Thanks for the tip! I am really into pinstripes and I have a good source for it. I buy "pinstripe" wood in 1/8" and 1/16" thicknesses quite often. I have maple, ash, walnut, mahogany, purple heart, cocobolo, and bocote right now - so I am good. I usually find that the acoustic sets have a really thin top, and I like to start with at least an inch of top wood because my basses are radically carved. I need the extra wood even though much of it turns to sawdust in the end. Most of the acoustic tops in the sets I have seen are 1/4" thick or thinner.

    Yeah, when I bought Wilma from Andrew Drake, the first thing I had him do was make a nice wenge control cavity cover to match the neck. The mahogany one wasn't grain matched so I didn't care for it.

    Wilma.png Wilma-1.png

    Thanks for the idea though, a really good one for sure if you are working with thinner drop tops.
  11. Means2nEnd

    Means2nEnd Supporting Member

    Yeh I don't use them for tops but in the sandwich... unless it's for something like purpleheart or ziricote where it would make the bass 200 lb but for the wenge between the red zebra and African mahogany on this body I made it work swell and cost about $30
    BassHappy likes this.
  12. AHA!

    I see what you did there!

    Very cool!
  13. PDX Rich

    PDX Rich

    Dec 19, 2014
    Portland, OR
    I am not a big fan of wooden knobs and pickup covers, but I do like the look of a matched wood cavity cover to a certain degree.
  14. Very nice. good idea, that I will probably liberate at some point down the road. I use a thin laminate often between the top and back, but there are times where a thicker laminate would be better.
  15. I guess I should clarify the pinstripe thing a little. I use really thin veneer to create the wooden "pinstripe" effect. Very similar to yours Means, but I use much thinner veneer.

    MaplePinstripe.jpg WalnutPinstripe.jpg 13339_lowerhornL.jpg
    Means2nEnd likes this.
  16. I do those thin laminates a lot as well, but I like the idea of a thick laminate, especially in cases where the wood I'm using isn't quite thick enough, always good to have options.
    BassHappy likes this.
  17. HaMMerHeD


    May 20, 2005
    I do a lot of pinstripes, but I just use veneers. They look thick when carved on a bias.

    These are 1/42" veneers.

    I used 1/8" padauk on this one:
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  18. Also, as an update, realizing that I could still grain match the control covers is pretty cool. I especially want to do that on the one with the flamed maple back, unless I come up with a "signature" cover that I would prefer. Since the clamshells are not glued together, it's a simple matter of an uber thin 4" diamond plug cutter. I can drill all the way though the back of the body and then fabricate a slightly smaller circular retaining ring to attach to the inside of the body, to provide the lip. Then the cover piece will drop right back in with the help of several small magnets. I have some ideas on an easy way to pull it out. One is to use one of these refrigerator type magnets on the underside of the circle - in the inside of the center - and use an even stronger magnet to pull the cover off.

    You can even get this fridge magnet stuff in thin circles of most any size:


    Something like this should do the trick to pull the cover off, it pulls up to 100 lbs. Just keep it in your guitar case so it goes where you go and you are all set. Please note that none of these five prototypes have magnetic pickups, they are all piezo only, so I don't think there will be any magnetic issues with the electronics. When you need to pull the cover off you let the super magnet do the trick:


    If anyone sees or knows why this may not work, please chime in. I am thinking I am on to something, at least I hope so. We will see if it actually can work.

    I think that a tasty design might be as good, if not better though than grain matching, especially to dress up the other mahogany backs. I would glue the leather to an aluminium plate and sandwich the fridge magnet in between. I would think leather might even be better for this purpose than wood. So I am keeping my options open. I am really attracted to the idea of leather covers, maybe something like these. It's so cool that most coasters are in the 4" diameter range. I may be able to find something uber cheap off the rack, but I would prefer to have my own similar design hand tooled, depending on the expense:




    We will see....

    Ultimately my own design with the help of a great laser leathercrafter might be just the ticket to dress up those mahogany backs!
    Last edited: Jun 9, 2016
  19. Bruce Johnson

    Bruce Johnson Gold Supporting Member Commercial User

    Feb 4, 2011
    Fillmore, CA
    Professional Luthier

    Here's another way to make an invisible latch/release for the cover: Rout the pocket for the round cavity so that there is a shelf around the outside edge that the cover will rest on, flush with the surface. But, make the shelf only go around about 220 degrees of the circle, a little more than half the way around. On the other 140 degrees, rout the pocket out to the OD of the cover; no shelf. Inset three small round rod magnets into the shelf, spaced around the 220 degrees. Make the cover from a disk of, say, 18 ga steel, with your leather or wood cap epoxied on to it.

    Now, when you place the cover down into the hole, it will stick down to the three magnets on the shelf. To release the cover, push down at the edge of the cover, over the center of that 140 degree arc where there is no shelf. You have to know where that spot is. When you push that spot down, the other side will tip up. Grab it and pull the cover off. Do you see how that works? Simple and reliable, no tools. And only you know the trick to removing it.
  20. Hey Bruce

    While your suggestion seems like a calculated and tried and true solution, I think I will stick with my own idea. This is how we learn. Not sure what your concern is with my idea - you didn't mention any criticisms - but I really don't think having a couple of $14 dollar super magnet tools on hand will be a big issue for me. Besides, with no mag pickups involved - I am just crazy enough to think my solution could work alright.

    Obviously, I am just a newbie - and a trial and error guy at this point, so we will see...

    But thanks so much for the ideas.
    Last edited: Jun 9, 2016