There are no plans anywhere on how to build a tube style case.
This is the basic case:
Plumbing tubes for the butt, electrical tubes for the shaft. Sew a liner like a sock with open ends and thread it through the tubes and secure at both ends. Bond all the tubes together to form one unit and wrap your leather around it.
Close the loop. You can close the loop with a single seam that is either back to back - meaning that the back of the material is facing each other - this makes a teardrop shape and is easiest to do. This is what is used on the envelop style cases.
Or you can close the loop with a seam that is back to front and layered meaning that the back of the leather is facing the front of the leather on the other side. This type of seam is most commonly riveted, hand sewn, or laced. This is what is used on most tube style cases, Flowers, Justis, Murnak, JB Cases, etc...
Lastly you can close the seam by butting the ends of the leather end to end making a flat surface. Most commonly this is laced. This is not used so much on cue cases as it is very time consuming and difficult to lace properly in a confined area. You can find examples of it on JB Cases,
www.jbcases.com/doc.html www.jbcases.com/hotrod.html
We do a sort of puzzle type variation where the leather is skived so that the two ends interlock. This makes the seam lay down even on a curve.
There are several variations of these three ways to close a case but these are the most common.
Lastly you can close the loop by simply gluing the leather end to end and making a single line seam. This is found on GTF Cases, Fellini and so on. It's George does a sewn version of this that is like the teardrop above with a very close fitting.
Next you want to consider your cap and how you want to make it. There are three main ways to do this - the flap, the oversized cap and the flush cap. The flap is the easiest and found on most envelope cases. It's basically just a retainer to keep the cues in while not keeping derbis and moisture out. Very few people do a fitted flap that is flush to the case. Here is an example of a fitted flap that was developed based off of a fly fishing tool case that was done by Arne Mason,
www.jbcases.com/shorty.html
The oversized cap is essentially just that - a cap in the same shape as the body and made to fit over the end. This can be done in an infinite number of ways really and what is important here is how well it fits. Poorly done ones are very loose and well done ones have a nice and snug fit. It can be attached as a hanging cap or as a flip top. If one elects to put a handle on the top then you should be aware of the stress placed on the latch and fittings and build to alleviate that stress.
The flush cap is a flip top cap that is flush with the body. Most commonly this type of cap is secured with a zipper However it can be done like this
www.jbcases.com/zack.html
Handles can be secured to the body prior to closing the loop. You should build these to last forever as they are hard to fix if the attached parts should break. Handles should be extremely comfortable as when they are not they become very uncomfortable in a matter of seconds when carrying the case.
Balance - your handles will NOT be in the direct center of the case. Most people prefer to put their cues in bumper down which means that the majority of weight is at the bottom of the case. When your case is empty it should tip slightly forward so that when cues are in it then it will balance. Of course this can vary with particular designs but it's essentially true across the board.
Bottoms: Here you have two basic choices, use wood piece to nail to or hand sew the bottom closed with leather. Hand sewing is more time consuming and should last forever when you are done. Using a wood piece takes time to fit properly but can be very solid when done correctly.
The best advice I can give you is to experiment section by section. In my shop we do a lot of different methods and anytime we want to try something new we make a model of just that section and test it. In this way we don't build the whole case only to find out that our theory or measurements are off. Write down EVERYTHING and make patterns once you have it where you want it. This allows you build a library that you can access and modify anytime.
Now, the ways to build a cue case are virtually unlimited. My basic philosophy is to wrap layers of protection around the cue and make it easy to use. So I have a lot of ways to build cases that fail one or both of those tests. I have experimented with a lot of non-traditional methods that are cool and may make their way into our offerings. The thing to remember though is that people are creatures of habit and you will have a hard time "retraining" them to use a cue case in ways that are not easy and familiar.
That's all for now.