My goal is to 3D print a 5 liter miniature barrel with a side stand, similar to this wooden one on Amazon. I want it to have a removable top so that a boxed wine bladder may be put inside, and there should be a hole on the top as well so that the spigot may stick out and be used. I have no experience with 3D modeling or printing, but I have access to a public 3D printer at my local library. I know you can print parts individually (ex. curved wood-colored sides with staves and holes to interlock and make up the body of the barrel, the metal-colored hoops to go around the barrel). I don't know what software to use, though. I was thinking of starting to learn Blender? Would that be effective for this project?
Your question begins in an inappropriate format for StackExchange, but you've ended it with one more appropriate by asking if Blender would work.
If you are willing to take the time to learn Blender, you are certain to discover that it will do as you require, and much much more. Your referenced model could be created using engineering-type design software such as Fusion 360 or SolidWorks or many of the free packages, but the free-form aspect is more suited to the flexibility of Blender.
Even though Blender is not an engineering-type program, it has internal support for precise modeling. Should you learn to use those features, you get the best of both types of software.
If you construct your model in the software in segments/pieces as you suggest, your result will have greater flexibility at the printing stage, specifically with respect to color and filament choices. Instead of wood-colored sides, you can use wood-simulated PLA filament! Depending on the printer at the library, you could also use filamet, a filament containing 88 percent metal for the hoops.
I use Blender for some aspects of modeling, often importing the STL into Meshmixer to address things I've not yet learned in Blender.
I hope your reference to 5 liter is the original size and that your model will be a miniature of it. A 3d printer with 5 liter capacity would be a wonderful asset at the public library!
I recently purchased a 3d printer and have found that freecad suited me really well http://www.freecadweb.org/ and its open source.
I believe its very similar to onshape in its a parametric modeller but runs locally rather that online.
Using the Parts view i have made most of my models using basic shapes and boolen subtractions.
You can check out Tinkercad. It is an easy to use, online editor.
Even though it is not as powerful as Blender or Rhino3d, for easy 3d models it is more than sufficient.
If you have any programming background at all, consider OpenScad. It is a functional type of programming language that lets you do a lot of things quite easily without art skills. OpenScad skills are useful for building customizable things on Thingiverse.
We get this question a lot in the facebook groups I manage.
The usual answers do not include blender as it has a stupid hard learning curve. That is overkill for what you are looking to do.
Look into 123d from autodesk. Free if you do not make money. I find this one to be the easiest.
Also there is Google sketchup, with SLT out plugin. I find this one is pretty sub par due to the fact it does not create printable models well (ie missing triangles so it wont create solids, hard to fix)
I think this one pops up. I haven't used it and I think it costs, but worth a mention.
I think Autodesk Meshmixer is the best, as you can easily make parts with boolean operations(if you're more of a cubic thinking guy) or drag-and-sculpt(if you're more of a freeform guy). (And thoses videos are old but still working).
If you want to get better reflexes in CAD engineering, I think Solidworks is the best (but really expensive if you aren't an enterprise), if you want to get better knowledge in 3D design and animations, maybe blender is good but surely not for CAD people neither for beginners in 3D (even if it's well-documented).
I'm no expert, but have done some research on this question and it seems to me that Fusion 360 is currently your best bet. It's designed to do exactly what you're planning, from start to finish. Design (Sculpting and precision modeling), Test (fitting/animation analysis), and Fabricate (CAM and 3D printing) all wrapped into one program that has a logical workflow, and is WAY easier to learn than Blender. It's free for hobbyists and startups making less than $100K/yr. There are a bunch of free tutorials online, professionally produced by Autodesk. By the time you get through those, you should be able to complete your project.
(Edit): I don't know anything about onshape.com. Like I said, I'm no expert.
I would highly recommend you checkout Onshape for your design.
It is the easiest to use, full featured, free 3D CAD program. It is made (and in active development) by the creators of Solidworks, the most widely used CAD program out there for good reason! And it runs in the cloud, so you don't need a high powered PC with an amazing graphics card, just a decent internet connection.
Onshape looks like it's going to be the future of mechanical CAD whereas other programs like 123d and Sketchup are simply lightweight versions of "real" CAD.
Unless you want to get highly involved in organic, complex shapes, I would avoid Blender, you will spend so much time learning it you could have whittled your barrel from a log instead.
To the people saying 123design. I can only say I have been a blender user way before 3D printing was a thing and just cant get around learning 123design. It just feels so limited as it only have a few tools. Yes blender might have a hard learning curve but it does pay off in the future as you wont be limited to 3D printing models and its crucial to make more complex models