Thread: Busted Old Höfner Mandolin

Originally Posted by FlyBri

Please stay tuned for photos of my progress and tonnes of stupid wood n00b questions.

Here's the second round of pics, showing the process of re-breaking the neck. I used masking tape, latex masking fluid and plastic shopping bags in order to protect the bulk of the mando while I applied warm water and heat in various fashions. I found that the easiest way of keeping the join warm and wet was to place a damp sponge onto the join, wrapping the whole thing in Glad Wrap, and placing it under a low wattage desk lamp.

The glue that had been used for the original repair did not budge from the heat and moisture, and my first stroke of luck came when I was able to separate the main part of the neck from the heel. You can see in photos 15 & 16 that the original repair had offset the neck about 2-3mm in the direction of the headstock, thereby effectively lengthening the scale. The repair was also slightly skewed.

Working from the body end of the heel, I used a fine(-ish) saw to begin to cut through the glue line. Once I had cut as far as I dared (I did not want any of the cut to protrude from the mortise), I was able to prise the join apart using a sharpened painter's spatula. Once again, the unidentified glue was not moving, so when the re-break occurred, it was wood and not the glue that broke. I convinced the small shards of timber to come out after a drenching with acetone.

The 18th photo shows all the various bits of the separated neck. The black markings on both sides of the break are high spots that I had identified using home-made carbon paper. The better part of a day was spent carving out high points so that the break would sit flush once again.

More to come.

Thanks.

Fly.

intresting looking little thing isnt it.....

should come up good

Originally Posted by Andrew_B

intresting looking little thing isnt it.....

should come up good

Thanks Andrew!

It is interesting looking, and I hope that it comes up good - this may or may not be determined by the bits of wisdom I manage to get from you guys...

Thanks.

Fly.

PS: Still trying to get my posts to show up. When I do, I'll post some more photos of my progress.

i didnt see that second post before.... lol

will you be doweling the heel/neck joint?
or do you have some other way you are going to do it?

i think i saw a mandolin neck repair on fret.com....

the shape is really cool... its like a pear... if only i could play mandolin

The neck joint looks like a very basic dovetail. Is the heel block a stacked assembly or is the neck and heel one unit?

Picture resoulton isnt too hot but looking at the fretboard extension over the upper bout of the instrument and where the heel has failed it looks suspiciously like root cause of failure might have been during clamping up of the neck joint.

A Mandolin has a fair bit of tension going on as there are eight steel strings to support. Ive not seen a neck extension glued to a soundboard so suspect that it was the stacked heel on the neck that gave way. Looks like it to me anyway.

Nice looking mando Fly. Were the cross posts from the Mandozine forum?

Originally Posted by Andrew_B

will you be doweling the heel/neck joint?
or do you have some other way you are going to do it?

Gday Andrew!

It has been suggested by a Canberran luthier that doweling is in order here:

Originally Posted by Graham McDonald on another Forum

The important thing is getting the main part of the neck and the heel solidly glued together before gluing it back to the body. I would be thinking about a dowel drilled up though the bottom of the heel after you have glued it together.

Now I have to decide what to use for the dowel: in my research on the topic, it would appear that often the 'dowel' is simply a small metal rod (a nail?), but I had been thinking of a traditional wooden dowel. Either way, I reckon a pre-drilled dowel(s) will help me locate the neck and the heel during gluing: when I tried to glue the heel to the neck yesterday, I found that the two flat surfaces wanted to slide against each other, preventing me from aligning the bits of timber properly.

Originally Posted by kiwigeo

The neck joint looks like a very basic dovetail. Is the heel block a stacked assembly or is the neck and heel one unit?

Gday KiwiG!

I'm not even sure that the neck joint is a dovetail at all - the only thing holding the neck/heel into the body was a lot of glue. The neck/heel was originally a 2 piece assembly (I've added a detail photo, where [A] is the original join and [b] is the break).

Originally Posted by Sebastiaan56

A Mandolin has a fair bit of tension going on as there are eight steel strings to support. Ive not seen a neck extension glued to a soundboard so suspect that it was the stacked heel on the neck that gave way. Looks like it to me anyway.

Gday Sebastiaan!

From what I can gather, the 'stacked heel' had been intact until I pulled it apart. I believe that the break was independent of any joins. Either way, once I get it glued together and doweled, that neck/heel join may never come apart again...

Thanks for the considered replies folks!

Fly.

FlyBri the dowel joint that Graham McDonald is talking about would be something like that described in Irving Sloanes book on steel guitar making. Its an old book but still available.

From your photos it looks like theres a slight bevel on the neck tenon. Does the tenon fit straight into the mortise or do you have to fit in in from the top of the instrument?

Originally Posted by kiwigeo

From your photos it looks like theres a slight bevel on the neck tenon. Does the tenon fit straight into the mortise or do you have to fit in in from the top of the instrument?

Gday Kiwi!

Now that you mention it, there is the very slightest bit of 'dovetailing' going on there - in order to get the tenon into the mortise, I have to raise it by 2-3mm from its seated height, then drop it into its final position. Thanks for pointing this out, as it gives me a little bit more faith in the strength and structural quality of that join!

Thanks.

Fly.

PS: I have heard back from Mr McDonald, and his suggestion is to use 6mm hardwood for the doweling (as I had planned). Off to the hardware...

one dowel or two?

Sloane from memory uses two dowels.....they run down the side of the mortise/tenon. The holes for same are drilled after neck is fitted.

Gday folks!

I am relieved to announce that the neck is now 100% intact.

Please find attached progress photos up to this point. The last 3 pics show the completed neck assembly. In the end, I chose to use two dowels: one perpendicular to the fretboard and one at an angle (drilled through the top of the first dowel). Pic 29 shows the rough orientation of the dowels to the fretboard and fretboard extension. Pic 30 shows the tops of the bamboo skewers I used to help locate the heel during gluing, as well as the tip(s) of the dowels. (The base of the heel is a little messy, but nobody except you and I and thousands of Internet wood junkies will ever know...)

Thanks team!

Fly.

Not exactly what I had in mind with the skewers. I thought you were aiming to reinforce the M and T joint. I got your intentions wrong by the look of things.

Cheers Martin

Originally Posted by kiwigeo

...I got your intentions wrong by the look of things.

Gday Martin!

Not to worry - I obviously haven't explained myself as well as I could have.

The skewers were merely a means by which I could locate the 2 parts of the neck for gluing: previous attempts at gluing found the flat surfaces sliding across on another. Once the glue had dried, I drilled and placed two 6mm dowels in the positions indicated.

As for the mortise and tenon: I am not overly concerned about the structural strength of that join at the moment. When I acquired the Mando, that join was intact and sound, and it took me hours (literally) to get the heel of the neck out of the body. Also, as you rightly pointed out earlier, there is the slightest bit of dovetailing going on there (moreso at the narrow end of the heel where it is probably needed most). That said, I would be interested in hearing more about the doweling you have mentioned.

Thanks again!

Fly.