Otwin Rhythmus neck problems

[Dave Yelverton]

Just had in a guitar from a customer  who collects European archtop guitars built around the '60's.

The instrument is an Otwin Rhythmus archtop with neck problems which are I believe, common faults with this model.

The neck is beech with no truss rod. Unsurprisingly it has developed a considerable forward bow, giving a profile at the 9th fret of about .080" (2mm)

The neck also requires resetting, having pulled out of its dovetail at the lower end.

I'm assuming the neck removal will be by the normal methods. However, I have never removed an archtop neck. Does it differ from an acoustic dovetail or can it be removed by the same methods?

Once off  I intend to use heat to straighten the neck using a method shown on European Guitars Forum. This involves clamping the fingerboard to a steel  rectangular section bar heated by a fingerboard blanket. The customer is not keen to have a trussrod installed so I need to make sure that he gets a result which leaves him with the profile he wants when the strings are re-tensioned.

Will I need to induce a slight reverse bow to accomplish this? and what would be an appropriate temperature to set my blanket to ? (EGF never specified) I don't want to lift the fingerboard or damage the trim!

After re-setting the straightened neck, I expect that I will need to  need to remove the frets and level the fingerboard slightly followed by a re-fret.

I would greatly appreciate the accumulated wisdom of members of this forum. If anyone has experience of this model or similar European archtops (specifically I have in mind Graham Myers) could you let me know if there are any peculiarities I need to look out for

Oh, and last , but definitely not least.!...what would members regard as a fair price to charge for the work?

Regards

Dave

[Eric Steven Johansen]

Hey Dave, No experience with this maker but in similar situations I've had much better luck with removing the fretboard and installing graphite bar truss rods so nothing shows. Simply heating to straighten is not a permanent fix as the wood will return to the curve over time. Setting the neck straight with heat before installing the graphite is a good idea but you need something to make it permanent.

[Dave Yelverton]

Great idea Eric!...Don't know why that never occurred to me- must be the early onset Alzheimer's!

Cheers

Dave

[Kerry Krishna]

 Dave, the heat blanket thing will work , but in my experience, will need to be done several times. The 5 necks I have done this to, were all the same. I had to put a reverse bow in all the necks. You wait till the heat comes through the back of the neck before clamping it. I would do this work with the fretboard off, and it will go much easier. Don't be afraid to do it a few times. When it is finished will be the time to sand the surface flat, and route for two CF truss bars,, then reglue the board. Before the board comes off, take out the first and 16th fret, and drill a small hole through the bottom of the fret slot into the wood of the neck. With a couple of small pins you will have a perfect alignment when gluing the fretboard back on. This will kill  the slip/sliding effect  of wood glue wood sandwich.  The neck reset thing is another matter entirely. I would love to see several more pics, and the single one posted gives little info that this Forum can use to help you.  Please clean alllll that dust out, and do a few angles OK? It actually looks to me that the entire end block has slipped, and will not only need to be glued back in the original place, but will need to be worked on so it can't happen again in 30 years. I'll bet that you will be able to slip a putty knife between the back and the endblock...

[Dave Yelverton]

Hi Kerry- thanks for your reply. I was hoping to leave the fingerboard in place and just slip it, but probably with the old glue, that's going to be a non-starter!

I've attached some more photos of the joint. You'll have to forgive my non-existent photography skills- I hope that they will give you the info you need- otherwise let me know what shots you would prefer and I will try provide them.

I agree with you; it does look as though the block has shifted on the cutaway side. I can't insert a knife in the gap shown so I guess the glue joint there is still maintained but there's probably been some creep between the side of the block and the cutaway rib. It's a rather daunting prospect and I'd welcome any suggestions as to how to deal with it. It would possibly be easier if the block loosened up whilst steaming the dovetail.

With regard to removing the neck, will it be best to do that before removing the fingerboard?- and do I follow the usual procedure, i.e, drill at fret 15 to insert the needle?

My other main concern is the temperature to set my blanket for straightening the neck- I'm reluctant to go beyond 250 F as I don't want to char the wood!

Regards

Dave

                        

[Eric Steven Johansen]

Dave, I'm not so sure about the slippage of the block idea (observe the distance between the heelcap and binding as opposed to the separation at the cutaway) . It looks to me like the neck joint is not a dovetail but is instead a violin type neck joint were the entire neck heal shape is set into a matching mortise. Removal of the fretboard will reveal all of this to you. This type of joint is easy to remove and reset when the fretboard is not in the way. My guess is the separation of the side from the block is minimal and was caused by stress as the neck joint slid.

[Eric Steven Johansen]

Just noticed the nasty heel crack as well. You should be able to glue this tightly with the neck off the guitar.

[Eric Steven Johansen]

Oh and your photos are first rate..........

[William F.Eden]

I think Eric has this one well coverd .I just done one something like it only I put a trust rod in it.

The fee was 500. Bill.............

[Joshua Levin-Epstein]

Time for my 2 cents: I agree that it is a violin type mortise. The picture of the bass side shows a gap beneath the heel cap which I assume is the end of the mortise. You might remove the heel cap and try inserting steam from the back. You've said you'd prefer not to remove the fingerboard. In the interest of doing things twice (at least), why not get the neck off (with steam via the heel cap) then straighten the neck as much as possible with heat. I understand heat straightening works by softening the glue between the fingerboard and the neck. If the neck won't cooperate, then you can remove the fingerboard and reinforce the neck. By that time, the owner will probably come around to accepting a truss rod. Is there enough room under the fingerboard extension to put the adjusting end there?

But i'd be careful about that cracked heel. It looks like it wants to really complicate things once you start tugging the neck.

It's important to be optimistic about these things.

 

Joshua

[Kerry Krishna]

 Listen to all these folks! The fretboard needs to come off first for sure with this work. Doing the extra stuff here warrants a phone call to the owner too, advising him that the price just went up. In my shot, this would be over $500 for sure. Have you quoted him anything?

These are terrific pics too! 

[Eric Steven Johansen]

Going with Joshua on the opening at the bottom of the heel. I'd be inclined to inject some 50/50 warm water and vinegar into that location for a day or so before pulling the neck as well, to loosen up the glue, especially around that crack. I am still a strong proponent of the carbon fibre truss rod idea. You cant see it, it's strong as hell, and your problem is solved.

[Eric Steven Johansen]

And regarding pricing I'd have to go with Kerry. $500 +