Hi Vance. I have my two main thrusters mounted with prop "rings" that incorporate rudders into the design.
I have considered making the rings from fiberglass so a proper "Kort" nozzle shape could be used, but I started with just a stainless piece of pipe because it was laying there in the yard and was pretty easy to make.( and cheap ! )
Here's an older picture of them.
At this point the two side thrusters don't have any type of ring or nozzle so the "weed wedge " props will stay, maybe to cut through the kelp that will inevitably get up against them.
I'd like to get some brass props for the two rear main thrusters that have more of a fan blade shape to improve the thrust because of the prop rings. I've read that even just a simple ring improves the thrust, while the more highly engineered "Kort" nozzle is an improvement over the plain ring.
As for research.....well.....no. I haven't done any on that except to search out a couple of VERY expensive prop makers who would build what ever I wanted. Needless to say...That ain't gonna happen.
I wonder if I could make my own props from fiberglass? ( Like I need a new project.!! )
Still pluggin away at that thing. Was teaching my wife how to weld this morning....so the shop was plugged up with that stuff.
Better get back up there, she's got power tools running......I can hear them.......gotta go.
Frank D.