Steam Thistle Cluaran

[RNoe]

Pete:
The new prop is not plated with anything. Just carefully polished after shaping.

I worked my way through 7 different grits of sanding pads using a 3" diameter sponge disc with velcro to the pads, turned by my battery powered 90 degree drill motor.
Many recharged batteries later, the final grit was 3,000, then car polishing compound, and finally hand-finished with Brasso. I might put a final coat of hard car polish on it, too. Why not... Quite a time consuming process, but well worth the efforts.

I just hope the prop performance is an improvement over the beastly prop presently on the boat.
RussN

[RNoe]

Progress report on replacing the old prop (15" x 21 pitch) with the newly completed one (16" x 24 pitch):
We got the boat in the water on August 3 for baseline performance tests with the original propeller. No pictures though. I was too busy.

Tested ground speed (using an iPhone GPS speed app) at 200, 300 and near 400 rpm. Made pairs of runs back and forth (inside the breakwater of the Hood River Marina, Oregon) to neutralize wind and water movements.
Got a maximum ground speed of 5 knots at 385 rpm and 80 psi boiler pressure Not bad for a 17 foot boat with ~ a 2 h.p. steam power plant, not at full pressure.
The safety valves are set for 100 and 105 psi. Saturated steam into the steeple compound engine, using condensate to lubricate the moving parts, just as designed 50+ years ago by Cliff Blackstaff.
So far, all works well.

Today I braved the heat here (104F) to work in my cool shop installing the new propeller. When the shop temperature > 80F I was done for the day.

Accomplished:
Easily removed the old prop.
Cleaned and lightly polished the bronze shaft taper.
R&Rd the shaft and nut threads. Happily I have a nearly new 1" x 8 tpi tap which cleaned the nut threads nicely. I hand filed the shaft threads to clean them up until the nut fit firmly and smoothly.
Test fit the new prop, making measurements for correct spacers.
Then I machined the required thicker washer, and a new thin locking hex nut which had been missing.
Fit the prop with the new parts and the key, and measured the slop from that old worn brass key. It needed to be replaced.
Began machining a new key using stainless steel. Then I was too uncomfortable to continue, so headed back into the cool of our house.

Why describe all this futzing around? Well, I had two friends tell me to "Just swap the two props at the marina, between tests."
Not that simple, guys.

To be continued, with a picture of the installed prop, and eventually more speed tests at the Marina.
RussN

[barts]

Nice work... the performance of the boat with the existing prop is nothing to complain about; here's hoping the new one is even better.

My (somewhat limited) experience with keyed tapers is that if the key shows wear, it's likely because the key was too tall and prevented the taper from making good contact all the way around, and instead was making line contact on the side opposite the key. The idea behind a tapered shaft w/ a key is that the taper transmits the torque via the high friction between the shaft and the hub; the key locks the joint but isn't the primary mechanism for transmitting torque. Prop shaft keyways are sometimes cut shallow, it seems.

You can check this by installing the prop w/o the key, torquing it and removing the nut and then measuring the amount of shaft that protrudes with the end of a dial caliper as a depth micrometer, and comparing that with the same measurement made with the key installed. If the key prevents the prop from ending up in the same position on the shaft, it's interfering somewhere.

- Bart

[RNoe]

Bart:
Agreed: The boat's present performance is nothing to dismiss.

Thanks for your lesson on fitting shaft keys. I will pay attention.
This is the first marine keyed shaft I have worked with, and there is always something to learn.
And I suspect the previous owner was inexperienced, based on other work done.
Knowledge is power.
RussN

[RNoe]

Patience required.
The new prop fitting is delayed by cherry harvesting, plus arranging for a new roof (next week), a solar panel system, and more.
Such is life.
RussN

[RNoe]

Finally (!!!) today I finished installing the new prop on Cluaran. This project only took 1 year from beginning searching for a classic prop casting,
then finishing it, and finally fitting it. Had to R&R the shaft threads and make a new key. It all went disturbingly well.
Next are more performance tests. Date unknown. Here's hoping...

Our new house roof is half done and the 32 solar panels get installed next.
No, I will NOT change the steam launch to electric...

No rest for the old and cranky...
RussN