Filling upper horn of hollow body with epoxy to relocate strap pin?

Discussion in 'Luthier's Corner' started by andruca, Jun 11, 2020.

  1. andruca


    Mar 31, 2004
    Madrid (Spain)
    Hi everybody. I recenty bought a MIK Warsick StarBass 5 and even tho' I LOVE thits tone and looks there's 2 things I'm fighting over. One (least grave) is the "Les Paul mark" it puts in my forearm (it ends up hurting if I play the bass for a couple hours). I've got some black corner protection foam coming my way for that, I think a little piece can work out sort of an "armrest", I'd attach it with 3M Traceless tape, vert strong and can be cleaned up easily when removed (I've used it to attach several foam ramps for many basses, comes out totally clean, easily).

    The other thing is it hangs horribly on a strap due to the neck side pin being located in the base of the neck joint; as the back of the body is arched the bass hangs facing down and I have to force it into vertical position by both twisting my left arm and forcing my pressure on the "Les Paul mark" zone of my right forearm. Could definitely be solved by relocating the pin to the upper horn (and I've read people telling it breathes new life into its standup playing comfort).

    Now, I know people do this usually by molding a piece of wood that'd fit in the horn then gluing it in place (usually gaining access thru' the neck pickup cavity). The Star Bass doesn't allow for such access (the central solid block encloses the pickups) so I've been thinking (and this is my thread question), would it be too crazy to just put the bass horns down and use a syringe and plastic tubing (thru' the upper f-hole) to simply FILL THAT UPPER HORN WITH EPOXY? (+ small chunks of wood or someting else as structural material -also not to add too much weight, epoxy's dense-). We're talking a volume of no more than a couple cu/in (about 30ml if it were all epoxy, probably less than half that with wood chunks). Thanks a lot for your help.
    Last edited: Jun 11, 2020
    Huw Phillips likes this.
  2. dwizum


    Dec 21, 2018
    Hard to say without knowing the mechanics of that specific instrument. Can you share a photo or two? What are the top/back/sides made from? How big is this horn you need to fill?

    Epoxy is roughly the same density as water, so if it took 4 fluid ounces to make a solid fill big enough to put a screw in, you're only adding 4 ounces in weight. Not bad. You could mix in some microballoons to make it a little lighter in weight, but with any additive like that you're also increasing viscosity and at some point it won't flow enough to do the sort of self-leveling you'd need for this.
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  3. andruca


    Mar 31, 2004
    Madrid (Spain)
    Thanks a lot for your answer. Here's a video about its construction. The horn is a pretty minimal horn really (you can see the whole bass at the end of the video). It's all laminated maple, 5mm thick according to my caliber. Total depth of body is 44mm at the horn and it's just 55mm long (from base of described inner "U" to the tip of the horn). I think flooding the first 30mm would be enough, would't it?
  4. andruca


    Mar 31, 2004
    Madrid (Spain)
    Also, here's a photo of my Star Bass.

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  5. Jazz Ad

    Jazz Ad Mi la ré sol

    With this kind of shape you can solve both problems by attaching the strap to the headstock rather than a button.
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  6. andruca


    Mar 31, 2004
    Madrid (Spain)
    BTW, I wasn't thinking of mixing any chunks with the epoxy, but throw them in there, then pour the epoxy over, but I'm not sure, they'll probably end up coming afloat before it cures.
  7. andruca


    Mar 31, 2004
    Madrid (Spain)
    Hummm, I'll give that a try, right now, thanks so much for your suggestion.
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  8. Jazz Ad

    Jazz Ad Mi la ré sol

    Use a shoestring or something alike as a hack to give it a try. Through the hole of the strap, between strings and headstock behind the nut then round and tie a knot.
    It balances differently from a regular button to button strap and usually works well on hollow bodies with short horns.
    andruca likes this.
  9. andruca


    Mar 31, 2004
    Madrid (Spain)
    Just tried this, I have a strap with such cord (from an acoustic guitar). I don't find it that comfortable. It leaves the bass in an oblique position, alla' Jack Cassady...


    ... not that it's something bad, I'm just not used to basses resting on me like that.

    Be aware this is no light bass. It weights 4.4kg according to specs, which is as much as my lightest Stingray5. The body's heavy enough for it not to neck dive, even when strapped to the base of the neck joint as is stock.
    PennyroyalWe likes this.
  10. Jazz Ad

    Jazz Ad Mi la ré sol

    It's worth a try. You also won't hurt your elbow in this position. If you don't like it, back to the drawing board.
    andruca likes this.
  11. andruca


    Mar 31, 2004
    Madrid (Spain)
    I'll definitely try that for some days and see if I adapt. This bass sounds so great I'm foreseeing using it A LOT. Thanks so much.
  12. Huw Phillips

    Huw Phillips Life is like TV if the channel sucks change it Supporting Member

    Jan 4, 2019
    Bass looks awesome congratulations, I would probably try to talk to Warwick first, if you do want to go for epoxy I would drill a small hole where you want to put the strap button and load the epoxy from there with the bass vertical tuners to the floor, load the epoxy, then put the button in and let it go off, loads of blue tape and planning, you need to be 100% on how it’s all going to work do a test with the epoxy and a screw in a piece of plywood the same dimension as the piece on the bass, think about it a lot prior to doing the work and try to foresee any problems
    Good luck
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  13. TraktorBass


    Mar 9, 2017
    @andruca: I had an Epiphone Jack Casady and suffered the same issues. Neck dive and the upper part of the body tending to tilt itself towards the floor. The Jack Casady and your Warwick are obviously not the same basses, but they are of similar construction and both have the strap button on the back of the neck.

    After some deliberation I ended up drilling a hole in the upper horn and placing a new strap button there. I did not reinforce the wood in the horn, and it ended up working out fine. Mind you, I am no Pete Townshend.

    Surprisingly, moving the strap did not help the dive, and (oddly) made the tilt even worse. Ended up selling the bass as it never felt right.

    Good luck!
  14. Jeff Hughes

    Jeff Hughes

    May 3, 2020
    Sometimes people put strap buttons on 335s on the upper horn. I have mostly seen them screw pointing towards the bridge if that makes sense. I imagine this bass has multiply maple and poplar sides and top. That is how a 335 is made at least.

    The screw will probably hold as long the pilot hole and screw are not too destructive. I have seen them underneath the horn too with the screw pointing towards the ceiling.

    The edge causing the arm pain is the worst. I had a Hofner that did that. On guitar you can get used to it, but on bass we tend to rest our arms there.

    The neck dive would probably be best solved by a different strap. Neck dive is the reason the upper horn on a pbass sticks out further than the bottom apparently. Strap button moves and weight is redistributed thus no neck dive.
    Last edited: Jun 11, 2020
    andruca likes this.
  15. Jon Lars

    Jon Lars

    Mar 16, 2011

    I would be very leery of pouring a puddle into the horn.

    Epoxy Chemistry - Understanding WEST SYSTEM Marine-Grade Epoxy

    "Exothermic heat is produced by the chemical reaction that cures epoxy. The amount of heat produced depends on the thickness or exposed surface area of mixed epoxy. In a thicker mass, more heat is retained, causing a faster reaction and more heat. The mixing container’s shape and the mixed quantity have a great effect on this exothermic reaction. A contained mass of curing epoxy (8 fl. oz. or more) in a plastic mixing cup can quickly generate enough heat to melt the cup and burn your skin"
  16. iiipopes

    iiipopes Supporting Member

    May 4, 2009
    Otherwise known in history as the "Hootenanny" position, as on Early Fender basses, and string ties on the neckstrap to tie them under the strings behind the nut for the folk guitar players.
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  17. Jeff Hughes

    Jeff Hughes

    May 3, 2020
    Take a little wooden wedge that will fit through the f hole and fish it through a pilot hole in the horn. Screw the strap button into the pilot hole on the horn while holding tension on the wedge. I think the screw would pull the wedge tight against the interior of the horn. This way the screw would have more wood to sit in. You could even pre glue a wedge into place.
  18. Plain Old Barry

    Plain Old Barry Supporting Member

    Mar 1, 2018
    I'm not a luthier, but I make and restore antique reproduction furniture, wooden airplanes and play bass.

    Can you install a plywood or solid stock backer where you want to relocate the pin? This would eliminate fully filling a potentially resonant area, curing heat issues, and weight from the epoxy.

    It could easily be located by coating with wood glue, a strip of CA around the edges to grab immediately, the simply drilling the screw hole.
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  19. Scoops

    Scoops Why do we use base 10 when we only have 8 fingers Supporting Member

    Oct 22, 2013
    Sugar Creek, Wisc
    I vaugley remember someone who posted with pics just as suggested, but I just can't seem to find the posting

    I would think this would be a good approach
  20. Ross W. Lovell

    Ross W. Lovell

    Oct 31, 2015

    You can heat epoxy two part once mixed to make them flow better but be advised heat usually accelerates the cure time.
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