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

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

  1. Copperhead

    Copperhead Still creakin' around. Supporting Member

    Jul 29, 2018
    Welcome to the world of long scale hollow body basses, no disrespect intended.
    J_Bass and andruca like this.
  2. alarius


    Feb 20, 2018
  3. sharpiemarker


    Feb 15, 2013
    You will have to search for it. A few months ago someone here moved the strap button on an epi jack casady. I remember them adding some wood to reinforce then horn before drilling into it. They posted very detailed pictures and described the process. Way next level but I think that will work better then just epoxy
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  4. Dan_reeves


    Jun 14, 2013

    You can barely see the button placement on this Fret Wire kit I built. I put the strap button on the horn because I liked it there better. I mixed some epoxy and pushed some through the hole with toothpicks. Then before screwing in the button, I coated the screw very liberally before screwing it in. The I let it dry with the headstock pointed at the floor. This was 6 months ago and still going strong. I don’t like the back strap button on ES335 style guitars or basses.

    PS I know the strings look weird...I was working on nut slots at the time I took this picture
  5. James Collins

    James Collins

    Mar 25, 2017
    Augusta, GA
    I might try to come up with a way to replace the screw with a nut/washer/bolt set. You would only have to do it once, even if it was annoying and more time consuming to do than it seemed it should be.
    andruca likes this.
  6. JeezyMcNuggles


    Feb 23, 2018
    Santa Maria, CA
    I suck, but nobody really notices
    Just hit it with a dot of "plastic wood", and some nail polish to match the finish.
    andruca likes this.
  7. gebass6

    gebass6 We're not all trying to play the same music. Supporting Member

    Well,for that "Les Paul"mark........... wrist.jpg
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  8. andruca


    Mar 31, 2004
    Madrid (Spain)
    Thanx everybody for your ideas. Being that the f-hole is the only access point to the interior of the hollow wings the block thing is a little complicated. I could do layers, but then again, I'm not skilled enough and don't even have a camera probe or anything to not only look inside but also maneuver in there.

    The strap attached to the headstock is uncomfortable to me, more so given that I use the bass pretty low. Still have it like that right now but it won't stay there, feels like it's about to slip out of my shoulder any time.

    What I'm probably trying is @Huh Philips' suggestion: a hole in the laminated ring where the pin will be placed, then make "threading" to the laminate with button's screw, take screw it out, mask it properly, inject epoxy in (I was doing the math wrong yesterday, about 4-5ml will do), then screw pin back in and let it cure. Easiest cleanest way.

    I'll update when I get busy on it. Thanks a lot for your help.
    Jughead6 and Huw Phillips like this.
  9. Isaac J

    Isaac J

    Dec 26, 2016
    I've never tried this, but have you considered using a wall plug?
    - As in, drill the hole on the horn wide, insert a wall plug and screw into that? My thinking is, if it works for hanging heavy furniture off (brittle) plasterboard, it could well work for your problem!
    Good luck in your mods!
    andruca likes this.
  10. andruca


    Mar 31, 2004
    Madrid (Spain)
    Someone suggested that in prior posts. Thing is I don't want the thin laminated maple wall to do all the work, therefore the whole idea of "solidifying" the tip of that horn, so that it holds the whole length of the screw (or at least more than those 5-6mm of laminate I have, some 10mm extra should work). I'm starting to work on it right now. I'll probably have it done in a couple hours.
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  11. A bunch of us have done precisely this to our Jack Casady basses. I injected 24mL of epoxy and installed Schaller S-Locks. Don't worry, it works just fine. Just make sure to mask off the area so you don't get epoxy on the finish of your lovely Warwick!
  12. Moving the strap button to the horn will certainly help, but I am not entirely sure it will cure the problem as that's still a pretty low position: it aligns with... what, the 15-16th fret or so? Neck dive is my largest 'pet peeve' and I've tried moving strap buttons to different locations on a few basses and I never found a fully satisfactory solution when the horn was so low.

    Before doing that, I would try attaching the strap to the horn with some suitable tape or something that won't mark the bass, and see how it feels. It would be a shame to do what you're proposing and finding that it doesn't help enough. It will help some, but I'm pretty sure it would not be enough *for my liking*, of course other people have different tolerances to this issue.

    edit: I just saw on another post that yours does not neck dive... ah well :D ignore me then
    Last edited: Jun 12, 2020
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  13. braud357


    Jul 1, 2010
    Gonzales, LA
    Be careful when filling with a lot of epoxy - I recently used some to fill a battery route under the pickguard on a jazz bass, and it took forever to dry completely ! I stood the bass up after a couple of days dry time (5 minute epoxy) and some of it ran down the front of the bass. Made a mess, but thankfully the polyurethane resisted and it cleaned up with a lot of elbow grease.
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  14. iiipopes

    iiipopes Supporting Member

    May 4, 2009
    I don't know if this would solve the neck dive, but another accepted position for a neck strap button is on the underside of the heel of the neck, otherwise known as the "Taylor" position, as the standard place for the neck strap button as developed and applied by Taylor Guitars. It has the advantage is that it naturally pulls the body of the bass up and towards the body, doesn't need any filler wood, and is relatively discreet in appearance. Just get it up into the meat of the heel, not on the lower part of the heel as some pictures show:

    andruca likes this.
  15. andruca


    Mar 31, 2004
    Madrid (Spain)
    SO... it just took little time and effort. First of all let me show you a shot of how it used to be.


    First I placed the pin in the position I wanted it to be and marked just a dot using a nail, then drilled it with a 1.5mm bit.


    I put the screw in so that it "threaded" the laminate. Then I masked the whole horn with some paper tape, just to play safe in case of any accidental dripping. Then placed the bass upside down (horns facing the floor). Prepared some 2 part epoxy (not your usual molding epoxy but plain 2 component epoxy glue I had home), sucked 5ml into a syringe and proceded to inject it (no needle, just the tip of the syringe). There's no photos of the injecting process as I was all alone. I had a piece of tape ready, which I applied once I had emptied those 5ml so it didn't all come pouring down thru the screw hole. Then I screwed the strap pin in tight and let it rest like that cure (cures in 10min according to instructions, left it for half an hour).



    Waited for it to cure, took out all the masking tape, and voilá...


    After an hour I tried hanging it and IT MAKES A WORLD OF DIFFERENCE in regards to the facing down issue. No more left hand twisting pressure needed. It in turn also alleviates my right (plucking) forearm troubles against the square angle binding.

    This is the best picture I could take inside there (mobile + little mirror, all thru' the f-hole, which is some 10" away (closest part of the f) from the horn really. The clear part you see in the center is the "pool" epoxy formed in the tip of the horn. You can also see the tip of the pin screw coming out a couple mm. Totally cured, no drips (photo was taken laying down about an hour after pouring).


    Now, some concept I maybe wasn't 100% clear from the beginning. Some of you have mentioned neck dive. THIS BASS DIDN'T NECK DIVE BEFORE (with the pin on the neck joint), or might I say it JUST BARELY DIDN'T. I mean, it stayed more or less horizontal, just acceptable. Now, after the "upgrade", this seems to also have improved, it stays where I want it with more "authority". I'll check that extensively tomorrow tho', as max strength is reached past 24 hours, no need to force it right now.

    Thanks everybody for the ideas. Hope not to disappoint those of you suggesting more skilled woodworking solutions, I appreciate your input 200% and certainly learned from it, just am not skilled enough to do such stuff, and access thru just the f-hole adds an intricacy to such solutions that puts it all way out of my technical reach. This still looks and feels damm strong tho' (no surprise, epoxy is TOUGH).

  16. nice work!
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  17. andruca


    Mar 31, 2004
    Madrid (Spain)
    I have a little experience with epoxy laminating longskate decks (not same application, I know). This usually could be that:

    1) there's some kind of moisture involved that keeps epoxy from curing
    2) the mix proportions aren't right (migh never cure)
    3) mix wasn't stirred long/homogeneous enough, so there's traces of resin that don't have hardener to cure with

    Also there's types of epoxy (usually the ones used for being used as a lacquer for floors or furniture) that are more fluid and won't cure when applied too thick (i.e., won't work to make a shape pouring it in a mould).
    TrustRod likes this.
  18. J_Bass


    Feb 7, 2008
    Porto, Portugal
    No doubt.

    I had a beautiful Starbass II, sounded great.

    But that issue made me sell the bass. I just couldn't play it comfortably.

    I believe yours is a 32" scale, but mine was 34". I finally sold the bass, couldn't play it standing up.
    andruca likes this.
  19. Gilmourisgod


    Jun 23, 2014
    Cape Cod MA
    Well done, sometimes the simple solution is the one that works. That epoxy should cure at least as hard as the wood. It should last a good long while. In your shoes I probably would have used the wood wedge technique, because there is no simple thing I can't make harder.
    andruca likes this.
  20. mdogs

    mdogs Supporting Member

    Apr 13, 2010
    Constant state of flux

    Yup, I did this exact process to an Epi JC and it worked like a charm. I got the trick I think from some Gibson forum where people had been doing it to their 335's (et al) for years. Solved neck dive and kept the bass from wanting to roll forward. Such an easy thing to to do, the mfg's could solve a lot of angst with these type instruments if they did this at the factory!
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