Not a dumb question.

Bearded iris rhizomes create offspring along their sides and the fan end can also grow outwards. So you are correct in planting with fans pointing outwards.

I wish I could say all rhizomes behave the same but they don't. Some cultivars make "nicer" circles than others. One pattern used is 3 rhizomes pointing outwards - a triangular shape.

As far as size of clump, that will depend upon the vigor of the cultivar, the soil, climate etc. Clumps that are 3 years old are usually ready for division (with the center becoming sparse). A trio of TB rhizomes may attain a clump diameter of 20" in 3 years. Impossible to guarantee.

Think of an iris rhizome as a short leg with foot attached.
The fan end would be the heel. Most iris have increases on the back of the heel and make growth away from the heel.

The foot and toe end can have increases that will grow away from the sides of the foot. Depends on many things what you will get. Planting with the heel out usually works the best.

Planting iris in a row all iris should face the same way. I should take my own advice as I am not too careful about that.

Mike G

Thanks much for the information. Will plant about 20 inch diameter circle with fans facing out and plan on dividing in 3-4 years.

The problem with fans pointing outward is that the center is bare.

I usually plent three in a "V", with two aimed outward and one towards the center of the "V". It will grow into the space the other two are leaving.