Using my handy string gauge calculator, I figure:
G - 13
C - 20
E - 16
A - 12
My little Indian Tabac ukes are soooo quiet, I'm contemplating switching out to steel strings. Currently I have those black GHS nylon ones on there, but I don't think upgrading to nylgut is going to make that much difference.
I haven't built any cigar box ukes but have restored a couple of soprano ukes and due to hand problems have gone through stages of changing my regular guitar strings from steel to ball end classical. On the ukes I wanted to play them using guitar chords and going from the elastic band like ones to hard tension classical (tuned DGBe and using the thicker guitar string meant for two strings up in the packet so uke D is the thick E guitar string etc) gave a much improved volume and I was able to lower the string action by a long way. It has lost some of the twang but I prefer the new classical sound. On my guitars going from steel to classical gave a slightly lower volume and a change in sound from a steel strung guitar to a classical - no surprise really, also it needed a slightly higher string action.
Strings are cheap so you could always give them a try and see if you like the new sound.
Another option if you want to keep the original sound is the "passive preamp" kit (a passive filter not a preamp) we discussed over in CBG electronics a while ago http://www.cigarboxnation.com/group/cbgwiringelectronics/forum/topi... (about half way down). These are quick to fit and need no soldering. I tend to buy from whoever has them listed for the lowest price on ebay (search "passive piezo" for most hits with the worldwide option) at the moment the cheapest is http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=1206809833... at $6.99 (£4.37 approx) including delivery. If you are willing to risk $6.99 to check one out you can set it up with the rod under the strings by the saddle with the amp external and plug it in without drilling any holes and if you don't like the sound your box is still unblemished.
I once built a tenor ukulele and used the bottom four strings from a guitar D G B E if you use them as you would on a guitar but tune them g c e a you end up with whats called a low g tuning which is very nice.
Small scale and steel strings will make for a stiffer action (IMHO) and make playing a bit harder.
Also, it'll take more tension to tune steel than nylon ..... so it could be disastrous on a regular uke build ... I wouldn't do it unless neckt-thru ( again, IMHO).
Diane, I've waited a couple of days to respond as I wanted to contemplate an intelligent answer to your query. First I assume these ukuleles are concert scale hence the findings from your calculator, I however don't agree with the results. For the sake of discussion I would discount the results and go with the light gauge on the strings. 10 for the G and 9 for the A and so forth. My reasoning is you will get to pitch with less tension, giving you more of the feel of a strummed ukulele. I'm not very confident in my reply as only once with an experimental soundboard did I have a muffled poorly projecting instrument. Even trying steel strings were no help. I assume you can not open the box now so thinning the soundboard is not possible. Although what I am suggesting might seem farfetched, is there a design area around the perimeter of the top you could clamp a metal strip to and with an Exacto knife weaken the top by slitting along the permeter, much like a violin top is done? The weaking action allows the top to vibrate more. Drastic I know. Also you might look into resonator uke strings as they possess the greatest tension of all. Good luck.
hi Diane, I would try Aquila's first, high tension, and louder. if you have a concert, or soprano put on tenor strings as the tension will be higher again. string wise just put on the high 3 of an acoustic set, and double (reuse) the high e string to get the re-entrant string. (so string wise it would be e,g,b,e). tune it like a uke and it should work well. (and you can add a bass 4 pole pickup too just for fun)
Don is right about thinning the top too. the other thing to try is ripping off the bracing (assuming you have it) or re adjusting (shaving) the braces if you feel this is too drastic.
best of luck and hope it turns out well