Sanding blocks, usually with 5 flaws. This one tries to remedy them with simplicity.
Downloaded few models and was very disappointed that I would either have to fiddle around with hand screws and very carefully place paper in the block and pinch it together (1st flaw : Design slow to use, everybody knows that you need to replace paper quite frequently).
One other thing I was annoyed was that most models used very sharp edges, 90 degree or much more, that easily break the paper in actual use (2nd flaw: No heavy usage possible/much paper loss). This all and fact that most models use very much plastic all together and are very time consuming to print (3rd flaw: Material and time usage).
Oh yeah, and worst of all, I couldn't find any that were even remotely ergonomic to use (4th flaw). Here the "bow" act as a fairly natural curve to handle.
So because I was seriously disappointed to pretty much all models. Here's my quick personal giveaway for more sensible approach that isn't over engineered. Also trying to fix those 5 flaws generally seen in sanding block designs. I tried to figure out something suitable and looked at my computer's mouse and here the idea of ergonomic bow type came and design began with criteria's to try to avoid those mentioned errors.
Basically simple base and "bow" that you pinch the paper in place. Added that using slight pressure in sanding pinches paper more and more tighter. Also tried to make some radius to parts to prevent tearing of paper (5th flaw). One basic criteria was it would also be nice that you could sand some slight very dome shaped arcs, which this model also allow in some small extent, because if base flexes the bow part with pressure will compensate.
Also added marker in base plate to make cutting sanding paper to more suitable length. Oh yeah, this was also one criteria I was very annoyed by most models as paper would need to be within say 1cm tolerance. In this model length marked is only minimal. It really doesn't matter too much if you cut paper into quite much longer length. It would just get into your way if way too excessive.
So all-in-all this still bit of an work in progress or more precisely said this is my first take on this model, but it seems to work decently enough to share the design. Likely I will soon add models with more "pointy" head for those hard to reach spaces and wider models for bigger surfaces, improvement of tolerances. Also I'll likely improve model a bit to also allow sanding in slight sideways movement too.
Anyway, there it is, the initial mode of 25mm wide block. Try and tell me what you think about it.
edit2 Now with slightly altered 70mm wide block also. Sorry no pictures, but works at least same as narrower block. Triangulated base plate for lesser material usage and also thought in mind that special abrasive products such as Mirka Abranet materials could be used more efficiently, though I'll likely alter triangle shape layout to more better in future*
edit3 Designed more ergonomic and stiffer bow for 70mm wide body. NOTE: I HAVE NOT TESTED THIS MYSELF!
With mentioned settings this model was printed in less than hour. NOTE: I PRINTED MODEL THAT IT'S ON IT'S SIDE AT TABLE, BECAUSE THAT'LL ENSURE THE CONSISTENT "SPRING ON MODEL". It's possible that it would work base being flat at print table, but I ensured consistency with this.
Also note that because sides are thin, It's definitely good idea to use brim or skirt to ensure that parts stay in bed, unless your setup is absolutely perfect concerning bed adhesion.
Obviously settings mentioned are optional. Fiddling with material and settings you can make more rigid model or softer to allow more curvature in some rounded shape object sanding.
If using skirt/brim you obviously need to sand one edge of both parts.