Hollows and rounds have no fences. They have no depth stops. They are difficult to steer and harder to correct. They have edges that take more skill to maintain than a straight edge.
I know what you're thinking. “I wish there was one wonderful thing that can take care of all three problems. I wish it only took one tool. And I wish that a video showing how to do it is easily accessible.”
Rabbets, Rabbets, Rabbets
-Hollows and rounds have no fences...Rabbets create a series of chutes on which the planes travel.
-Hollows and rounds have no depth stops...When laid out correctly you will plane until the rabbets are gone (or you're leaving plane tracks on both sides, but this occurs when cutting greater than 60 degrees of an arc so we'll get to that some other day.)
-Hollows and rounds take more time to sharpen than a normal straight edge... Rabbets remove most of the material.
These planes are difficult to steer. When they start heading in a certain direction it's difficult to change. If a plane has a single point for its sole to ride, the chance that you end up with the beginning of the molding equaling the end is slim. The chance of the beginning equaling the ending and equaling what you want? Good Luck!
These planes are steered by giving them two points to ride.
Let the rabbets and chamfers dictate the direction the planes are presented because it is easy to change these.
Let's look at some real life examples now.
Do you want an ovolo at 30 degrees? One hollow--one chamfer at 30 degrees
Do you want a cove at 30 degrees? one round--the tips of two rabbets at 30 degrees
Do you want an ogee at 30 degrees? one hollow and one round--one 30 degree chamfered rabbet for the hollow, the tips of two rabbets for the round, also at 30 degrees
Do you want an ogee at 45 degrees? Look at the differences in the rabbets below vs. above. Everything is laid out at 45 degrees here.
Do you want a reverse ogee at 30 degrees? Again, look at the different layout. Same tools, different results.
Do you see any features above you recognize in the previous two moldings at which we looked?
Additionally, look at how much material is being removed by the profiled planes in the perfect world of google sketchup. It's minimal.
Next week we'll look at how rabbets serve as a depth gauge.
One last thing: I am not the person to speak to regarding design. I am a copycat when it comes to my craft. This is the reason I bought my first antique planes--to copy. Anybody looking for elements regarding design should check out Lie-Nielsen's library. I've heard very good things about a few of their dvds, including those by Don McConnell, Larry Williams and George Walker. They are each extraordinarily knowledgable in the subject.
PS I wish I was in Warren, ME this weekend. Have you seen the line up at the Lie Nielsen Open House?