Old Banjo Mandolin. - skin tension

[Pete Doc]

A while ago I bought an old banjo mando. Documents in the case indicate that it dates from the early fifties or even earlier. Not a quality instrument but looked like it could be fun. The seller said that it had been unused and sitting in its case for thirty -odd years. the strings were still in tension, the bridge had distorted and broken and the skin had deep dents in it.
So, I've pulled it apart, polished up all the components, dampened the head and gently re-tensioned it. It dried out nice and flat and looking nice from the clean.
I found a new bridge online and planed it down to the same height as the original bridge. But when I started stringing it up the new bridge bent and the skin sagged down by maybe a quarter inch or so. not good!
My question (at last) is, How do I get the head to the correct tightness without destroying the original velum? the head is five and a half inches in diameter, tapping on it produces a note of E2 as far as I can measure with my tuner. I can knock up a new bridge no problem but I don't want to fit it until I have a better idea of the correct skin tension.
For a cheap old instrument it has scrubbed up pretty nicely. I imagine it should be a raucous little beast. I'm looking forward to playing it.
Suggestions would be greatl appreciated.
Good on you all.
Peter
P.s. I'm in Australia

[John Flynn]

I bought an old 1920's tenor banjo with a skin head a while ago. I had the same issue. I just tightened it up in a crisscross pattern until the head seemed evenly tensioned all over, based on how hard it was to turn the adjusters and pressing my thumb into the head near each adjuster. That just worked OK. Eventually, the head split.

The best investment I made was to just get rid of the old head and get a Remo Fiberskyn head. It was not all that expensive, it looks like a skin head and it sounds a whole lot better. I also invested in a Drum Dial to get the head tension to the recommended level and even all the way around.

You can probably get better advice on banjohangout.org I got a lot of help from that forum when I was going through that.

[Pete Doc]

Thank you John, I have been looking at the Banjo site, a lot of folks are offering a lot of different advice. I will keep researching until I get my bridge shaped up. in the interests of maintaining as much of the original as possible I have decided to include the notched fret wire from the old bridge. I'm gathering that it is a "suck it and see" sort of process. I am currently grinding down a 3/8 socket spanner to gt a firm grip on the tension nuts. I will tighten it up a 1/4 turn every other day and see what happens.
Good on you
Peter

[pops1]

Tighten up one, then the opposite one, the next from the first, then that opposite one and go around a little at a time. The head should be tight enough that it doesn't sag much under the bridge when tuned up.

[Richard500]

The one I have has a larger head. One issue is that 8 high-tension strings is a lot of downpressure at the bridge, so it is helpful to change the ‘breakover’ angle to shallower. Banjo things usually allow the neck angle to be changed at the tail end of the stick or rod. In my case, that involved adding a little adjustment gizmo. Then, the tailpiece on a banjo is adjustable in height with respect to the rim, so with those two things, you can set up a nice low action and a lower breakover angle so that the head isn’t under so much pressure. The final thing I did, which wasn’t recommended by anyone, was to drop the tuning to mandola, keeping the same strings, which improved the sound a great deal- to my ears. My theory is that there are no acoustic resonances or cavities involved so really no particular tuning range.
About the bridge: there are usual heights for banjos, somewhere around 5/8-3/4” if I remember, and the bridges are very lightweight. I made a couple because mine was missing; just being careful about sharp edges on that skin, and having multiple feet.

[pops1]

Another thing I always do on banjo mandolins is string them as a banjo. That's what they are after all. I use two sets of tenor banjo strings with a .028 for the G string. You don't need heavy mandolin strings for these, no banjo has heavy strings. It will lower the tension overall and not put as much down pressure on the bridge. It sounds much better, by the way, too.

[Pete Doc]

Thank you all for your advice, it is much appreciated. Re the break angle; when I first examined it, a straight edge laid along the fretboard actually came in contact with the velum. I have re-set the neck to give about 2mm clearance at the 12th fret with a 13mm high bridge.I am going to use a dummy bridge to get a good setup before carving a new bridge using the original fretwire top. During that process I will tighten the velum aiming for minimal depression. (mm, been fighting depression most of my life)
Regarding strings, I will start out with D'Addario's and see how they sound. (There is actually an ancient set in the case.) If it is too raucous to my ears I will fit a set of Aquila reds. I have them on my Fender. Easy on the fingers and easy on the ear.
When I learn how to post photos on this forum I will show you all the finished project.
Good on you all
Peter

[John Bertotti]

You are going got get several answers for tightening. I tune up drums the John Good way from DW. Watch a couple of his tuning vids he makes it look easy what you'll be interested in he doesn't use tuners dials or anything, of course, it's a drum. In your case it's the pattern he follows that I pay attention to.

[Pete Doc]

Good on you John. I'll chase up those Vids. I have had to dive into a few rabbitholes to get this relic playable. Cutting nut slots will be the next adventure. I'm moderate comfortable with that but I'll need a set of feeler gauges and a new caliper before I start.
Thanks again to all.

[steve in tampa]

I had the same issue and replaced the head. Sounded better and stayed in tune.

[Pete Doc]

Thanks Steve. The 'sensible' side of me would agree but I tend to get less sensible as the years pass. At 75 I've become a little adverse to throwing things away just because they're a bit old. This instrument may well be as old as me. I am trying to maintain as much of the original as possible even to the point of re-using the notched piece of fretwire on the bridge. The original head is pretty cool with hair follicles still evident. There's life in the old dog yet!
Good on you
Peter

[Pete Doc]

Just re-reading the posts Pops. The original strings are still in the cardboard case that came with the instrument. I should have taken note of them previously.
FYI they are G - .039 nickle wound, D - .025 Nickel wound, A - .014 plain steel, E - .011 plain steel. Reading what You and Richard have said I'm thinking that even lighter may be the way to go.
Good on you
Peter

[pops1]

My set is a 10 1/2, 12, 20, 28. so yes I would go lighter.