Some random publications

All;

I have posted the text of a few papers/publications at ResearchGate that were not widely circulated otherwise.

1) A short article on sailing yacht watertight subdivision
2) Random notes on design and construction of military/paramilitary aluminum boats
3) A on the basics of propeller matching from an IBEX symposium
4) A short paper on an alternative approach to block construction and outfitting for developable surface (hard chine) boats.

Chris BARRY | Chair | Bachelor of Science | Research profile (researchgate.net)

 

Thank you very much Mr. Barry. Your paper about propeller matching will help my understanding of this matter. (I'm building a small cabin katamaran, designed to go slow with solar electric propulsion. So I've to look carefully to achieve most effective propulsion and to minimize propeller losses.)

 

For a slow vessel (and a sailing yacht if you can tip up the propulsor), please carefully consider a Kort nozzle. The information for evaluating/optimizing one is widely available in the literature, and the calculations are reasonably simple with Excel. Might improve the efficiency of the system by 20+% and allow comparable increase in range or reduction in battery draw.

 

Thank you. It is just the Kort nozzles which since years were receiving much of my attention. A few years ago I found and downloaded the paper "The Development and Application of High Efficiency Nozzles and Rudders" from Josip Gruzling. I read it several times. The typical "advanced profile" was not named in this paper - only a profile sketch was given.. Your paper points to GAW-1 of which I could locate the coordinates now. About four years ago I've written a VBA-excel folder to create files for the desription of the surface of propellers relating to different given parameters, blade sections derived from an air foil profile. Goal was to get a 3D printed prop series to test them. But unfortunately the SDL files weren't accepted by the slicer software of printers. Probably because of the pervasion of the blades into the hub.

 

You will probably need to slice off the propeller at what would normally be the maximum chord or thereabouts and fit that in the nozzle. There is no need to taper down the tip of the propeller in the nozzle unless you have cavitation or similar issues. Take a look at the KA 4-70 props that are part of the standard Kort nozzle system for the basic idea. Also go to the Nautican or Helices Rice website for some ideas on how these "speed nozzles" look in practice. You should also find the coefficient algorithm series for the standard 19A /KA 4-70 props and run your propulsion case(s) to see if it makes sense and optimize the diameter and RPM / gear ratio. Look at the tau factor; if it is less that 1, the nozzle is helping. Principles of Naval Architecture (SNAME) or Marine Propeller and Propulsion (Carlton) are the standard texts and you may be able to find PDFs of some of them or get them from a library.

 

Thank you. I'm working at it.

 

Joe Gruzling founded Nautican, which is still in business, though he passed away some years ago. The profile he uses is very much like the GAW-1, for much the same reason; stall resistance.

However, the first step is to optimize a propeller using the existing Kort data and see if you need the reduced tau forbyour service speed. I have been surprised this way more than once, but the idea is to use all of the constraints your system has and see if a nozzle makes some sense at all. It may be that a larger diameter open prop will be fine, for example. If it does but a Kort nozzle doesn't work to a high enough speed, then a speed nozzle may be useful.

Note that the xfoil program is an open source code for designing and evaluating sections and would be useful (or at least interesting) for this problem.