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[derekwarner]

The propellers appear to be soldered, so as JimG questions ...'would it be possible?' to increase the pitch of the blades


Propellers for steam often have a ratio approaching 1.5 pitch to diameter...the propellers fitted to the vessel appear to be in the order of 0.7 pitch to diameter


Constructing a simple wooden jig to hold or clamp 'a single blade', then used in conjunction with a fixture [bench vice] could provide a relatively uniform adjustment to the pitch of each blade


An increase in pitch would place a greater load on the engines, reducing the engines speed, increasing thrust and running time


Derek

[DBS88]

It would be interesting to know what the pitch of these props actually is; is there a way to find it out?
As it happens I have a four inch, four bladed Prop Shop, prop so have taken some photos of it besides HMS Darings 3 Blade props, this may or may not help the discussion about the pitch of the current props. How does its pitch of the 4 inch prop compare with the current 3 1/2 inch props?

[DocMartin]

How To Measure Propeller Pitch

http://www.ricepropulsion.com/TNLS/Manual_Pitch.htm

[ballastanksian]

She looks fab on the water! Small scale steam does seem to be a great challenge that exercises the hobby, A chap wrote a series of articles in Model Boats back in the day where he built a metal model of Dreadnought and then installed dental drill air motors to use as steam turbines! I recall these having promise, but lacking power due again to lack of steam flow/pressure. I don't know how he got on as the articles were written about eight years ago.

[Geoff]

I have all these articles and it was a very interesting and valiant attempt and an interesting concept using dental drills. I seem to recall whilst he got it working the steam consumption was high and he had to start them with a drill as they were not self starting. I suspect the internals of a dental turbine are very different from a steam turbine.


Back to the TBD - if you have a prop shop prop would it be possible to fit it on one side and see if produces more or less thrust/speed. It would then give a direct comparison under identical circumstances which may provide some guidance. If its on the port side and the model turns to starboard then it would suggest more thrust.


A friend of mine commented that the "Sun" engines are best suited for high speed so a smaller prop and higher revolutions may give a better result, trouble is if you go that route the steam consumption will be higher. I always think of a boiler as having so many "bites" of steam so if you use them slowly you get duration, if you use them fast you get speed but less duration!


I look forward to the next instalment with interest. Very well done indeed.


Cheers


Geoff