Archtop Tailpiece issue

[ozziebluesman]

Hello to you all,

I need some advice.

I am having a problem getting the glue to hold the fulcrum block onto the ebony tailpiece. The block is 6mm square and I am gluing the 1/4 sawn face of the block onto the tailpiece. There is a small trench cut about 1.5 mm for the block to sit in. This is the second time the glue joint has given way under tension when I string up the guitar. The first time I used Titebond and the second time Ardeldite epoxy.

Here is a picicture of the tailpiece:

The only thing I can think of that might be the problem is the two gluing surfaces where too shinny and the glue had nothing to get its teeth into.

I would appreciate some advice.

Cheers

Alan

[Taffy Evans]

Hi Al, did you use the Super Stregnth Areldite? also you could try small dowels as well, possibly 3 of them. Good luck.

[kiwigeo]

Hi Al, did you use the Super Stregnth Areldite? also you could try small dowels as well, possibly 3 of them. Good luck.

You're dealing with predominantly shear stress here aren't you. The dowel pins sound like a good idea.

[Taffy Evans]

Also Al looking at the photo again, cut a wider block say 15mm, remove the timber on the outside of the two channels 15mm, glue the larger block inplace and then trim down the added timber to match the tailpiece behinde the block. Does that make sence???

[rocket]

Alan, it looks to me that the little fulcrum block is taking all the sheer load and if that is the case maybe the trench it sits in should be deeper, or that the chennels that the adjuster passes through should be deeper and therefor closer to the top face of the tailpiece so that the brass nuts of the adjuster are bearing on the same piece of timber that the strings are pulling on.
Cheers,,,
Rod.

[kiwigeo]

I love this sort of group problem solving....

[Dominic]

I had the same issue on my archtop. But it came off while strung up and i didn't notice until I changed strings. After trying twice I used some black epoxy with chopped up carbon fibre and left a little glue around the edges to create a ledge to help resist shear. Its a bit messy but you can't see it. I think this is just a poor design. The block is very small and the gluing surface is even small due to the slots and it has to resist a lot of force. I think I'll move to a taller tail nut thing on my current one so the tail piece is suspended completely off the top. Seems a much better idea and stops the top denting under the block.
Cheers
Dom

[rocket]

You might try making the tailpiece/fulcrum assembly from a single piece of material. Post subject: Re: Archtop Ebony TailpiecePosted: Tue Jul 05, 2011 2:59 pm . Cheers,,,
Rod.

[ozziebluesman]

Thanks everyone for your ideas.

I like Taffy's suggestion and will go that way with the three pins.

Rod: The piece of ebony I started out with was thick enough to make a fulcrum assembly from one piece but I made a mistake and had to go the 6mm block. Pity!

The past two hours I have inlayed three, 3mm brass pins and used the extra strength araldite and glued it back up again. We will see how it looks tomorrow.

Thanks again everyone

Cheers

Alan

[P Bill]

All good suggestions. Arildite isn't the best epoxy. Try " Boat Cote" , 24 hr set , cabosil thickened ( it's like thick jam). You'll find it , or an equivalent, wherever fiberglass is sold. Rough up the surfaces and press together by hand. It's important NOT to squeeze out all the epoxy. This stuff is gap filling and strong across the gap because of the cabisil , ground fiberglass.

[Dominic]

I think this is a much better way to do it. I also found that because of the geometry of the tail piece block and tail gut loop it is very difficult to keep the pivot block on the portion of the top supported by the tail block unless the tail block is quite deep. Under string tension it wants to pull forward. The shorter you make the loop in order to pull the whole thing back, the higher the angle it makes to the tail piece and the more downward pressure it puts on the pivot block. Apart from having a significant force pressing on the top and preventing it from vibrating in the that area it leaves a bad dent on the spruce. After a few years it would get quite bad I think.
Dom

dsc_0142 (Custom).jpg (51.47 KiB) Viewed 21615 times

[Dave Stewart]

Hi all
I'm new here & I hope you don't mind me buttin' in ....been a longtime lurker and, seeing this discussion (and being a somewhat opinionated SOB), decided to climb on board and offer my take.
Properly done, this should be a zero stress gluejoint. The tailpiece pushes down on the pivot, which pushes down on the top. BUT for this to happen, the tailgut cable must be fully enclosed within the tailpiece body. In this case, the cable holes (channels really) are half in the body (exerting no force) and half in the pivot (where the cables are exerting all the force to try to break the pivot off the tailpiece body). I hate to say, but I think this approach (no matter how it's glued) is doomed to fail, whether in static load or at the slightest upward impact on the tailpiece. Move the tailgut holes higher into the body (mine are about .140" above the underside surface), route the adjuster slots accordingly a bit deeper and glue the pivot on with anything....it'll be a permanently clamped joint. (I've even attached interchangeable pivots ...to guitars strung in the white ....with double-faced tape, to play with various breakover angles and finalize a design). Alternatively, I've recently been using a violin type "saddle" over which the gut seats, to eliminate the tailpiece pivot. Hope this helps

[kiwigeo]

Welcome to the forum Dave.

[jeffhigh]

Dom's arrangement looks really elegant, as well as being inherently stronger.

[ozziebluesman]

Ok, I think the problem is solved. It is not a great design but the brass pins should hold it together. The guitar is strung up again now so time will tell if it hangs on.

Here is a picture of the fix.


I'm with Jeff and like Dom's answer to the problem or make a one piece tailpiece.

Dave: Welcome to the forum and thanks for the explanation on the Archtop tailpiece.

Cheers

Alan

[ozziebluesman]

Plan B now, the joint gave way again. I have ordered a new ebony blank from Stew Mac and will make a new one piece ebony tailpiece.

Thanks again to all of you for your advice.

Cheers

Alan

[Taffy Evans]

Sorry to here that Al, the super strength Areldite I have used takes 3 days to cure, did you use the same stuff, blue and white tubes??? Just as a matter of interest, did you get the guitar tuned up to concert? and what's it sound like when the tailpeice whistles past your ear?

[ozziebluesman]

Taffy: Yes I used the super strength stuff, blue and white tube and the glue joint had cured for 12 hours. Maybe I didn't leave it long enough before putting the joint under preasure! Anyway, its a mess now and I'm annoyed with myself.

The first tailpiece held up for three days before it gave way. I am excited about the tone of the instrument. It has great sustain and the notes a fat! I just know this guitar is going to sound great. So I got yo play it for three days and couldn't believe how much sound was coming out of this instrument and I haven't even scraped the re-curve yet.

I think I was a little egar to hear this guitar and tripped myself up. Anyway, I will put some thought into the next tailpiece before jumping in.

Cheers

Alan

[kiwigeo]

what's it sound like when the tailpeice whistles past your ear?

Sharp

[Kim]

Plan B now, the joint gave way again. I have ordered a new ebony blank from Stew Mac and will make a new one piece ebony tailpiece.

Thanks again to all of you for your advice.

Cheers

Alan

Hey Alan, its a bugger when things put up too much of a fight but it does make it sweeter when you finally have things how you want them. In a big way the fact that you will now be making a new tailpiece is a good thing because you have learned a lot along the way 'and' you won't have any question mark hovering over you with this one when she's done...sort of like archie number 2 but it all came together on number one.

Cheers

Kim

[ozziebluesman]

Yes Kim it has been a great learning curve building the archie. The ebony piece that I started out with was thick enough to make a one piece tailpiece but I stuffed it up. So the fulcum block was second best method but it didn't work out. So starting out again is the go and I have the extra experience now to get it right. Thanks for your encouragement.

Cheers

Al

[ozziebluesman]

Snap would be a good word to describe the sound of the tailpiece flying. Lucky I was not too close when she blew.

Cheers

Al

[Dominic]

Bad news Alan, when I saw the pic with the pins I thought you had it beaten for sure. Although my tail strap went into open grooves like yours the body of the tail piece took all the strain. But i glued the ends in anyway with the epoxy carbon fibre mix. Perhaps a short-term option so you can tune it up and play it while you make the new one.
Cheers
Dom

[rocket]

This may be of interest to some, a while back i made a one piece tailpiece similar to the type we've been discussing here, i had it copied in alloy, i had several cast, polished and plated. A couple of pics to show you.
Cheers,,,
Rod

IMG_1296 (Custom).JPG (73.63 KiB) Viewed 21523 times

IMG_1297 (Custom).JPG (59.86 KiB) Viewed 21523 times

IMG_1298 (Custom).JPG (75 KiB) Viewed 21523 times

IMG_1305 (Custom).JPG (33.02 KiB) Viewed 21523 times

IMG_0456 (Custom).JPG (36.79 KiB) Viewed 21523 times

[Dave Stewart]

Nice, although in wood that one piece design invites potential failure in shear along the grain (above the pivot) that you don't have with the more traditional construction (where there's no shear, only compression). Also, not sure I want to see those adjusters so visable, rather than tucked away in their slots, but that's just me. But lots of ways to build a tailpiece.