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Author Topic: Loyal Class Tracking  (Read 3273 times)

CGAux26

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Loyal Class Tracking
« on: August 24, 2011, 12:56:46 AM »

I have had my Loyal Volunteer finished and in service for 5 months now.  When running forward with the rudder amidships, it does not track straight.  I have put in a new digital rudder servo, and fiddled with the rudder centering on the TX numerous times.  This happens at any speed.  The boat has Model Slipways' standard rudder, and a Prop Shop 4 blade, 2.2 inch diameter wheel.  The rear of the prop is within 1/8" of the rudder, so there is considerable prop walk in reverse.

How do I make it track straight? 
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derekwarner

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Re: Loyal Class Tracking
« Reply #1 on: August 24, 2011, 03:31:50 AM »

One simple test CGAux26 .......

1. take an old plastic CD case
2. cut two images of the rudder to the same profile aft of the pintail shaft.... >>:-( but say twice as long as the current rudder length
3. make a sandwich with the actual rudder in the middle & superglue the three plates together
4. return the vessel to the water & see if the near doubling of the rudder surface area has eliminated the steering drift
5. we also note that your current rudder is balanced [ as small % of area FWD of the pintail] but this should actually aide when turning

Good luck :-))........Derek
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Derek Warner

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www.ils.org.au

CGAux26

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Re: Loyal Class Tracking
« Reply #2 on: August 24, 2011, 03:37:02 AM »

I will give it a try.  And yes, the balanced rudder makes the boat turn very tight.
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ray123

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Re: Loyal Class Tracking
« Reply #3 on: August 24, 2011, 07:23:32 AM »

another thing   is the model  trimed ok  if it is down at the bow this realy has a big effect 'make's  it wonder'   regards ray
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farrow

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Re: Loyal Class Tracking
« Reply #4 on: August 24, 2011, 05:20:29 PM »

You know, no single screw vessel in real life steers straight with the wheel amidships, they usually require about 3 degrees of port wheel on for a standard right hand throw prop to counteract paddle wheel affect. Also these boats always ran with a big by the stern which greatly aids steering and turning. When they went astern they had a strong bias to port.
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CGAux26

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Re: Loyal Class Tracking
« Reply #5 on: August 24, 2011, 05:29:02 PM »

What do you mean by "by the stern?"  And yes, my model has the ruder trimmed a bit left when in neutral, to overcome the prop walk.  It's a left-hand prop.

I once had a single screw 32' sportfisherman that would track straight.  But it had a full length deep keel and a barn door rudder.  Loyal has neither.
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Shipmate60

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Re: Loyal Class Tracking
« Reply #6 on: August 24, 2011, 06:50:28 PM »

"By the stern" means that the stern is deeper than the bow so she is trimmed slightly "bows up"

Bob
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Shipmate60

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Re: Loyal Class Tracking
« Reply #7 on: August 24, 2011, 06:55:15 PM »

Back to the original question.
The hull above and below the water is subjected to different forces generated by wind, tide (even in a pond) and propwash, so very few models will track straight.
It is usual to apply a little trim to allow for this, and trim every visit to the water.
Large multi shaft vessels are not so noticeable but still require some trimming.

Bob
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farrow

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Re: Loyal Class Tracking
« Reply #8 on: August 24, 2011, 11:47:58 PM »

Hi Bob, nice to see you on line, I was going to say that the real RMAS Arrochar, 265ft in length, always trimmed half to one metre by the stern, four blade screw with 3000hp driving her, never steered in a straight line with out using the wheel and always at least 3 degrees of port wheel on. Thank goodness she had automatic steering, but as Bob has just said there are so many different affects on a vessel, which vary all the time, no vessel will even in best trim steer absolutely perfect unlike road vehicles which incidently you should always keep your hands on the steering wheel there as well.
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CGAux26

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Re: Loyal Class Tracking
« Reply #9 on: August 25, 2011, 12:19:25 AM »

Thanks, guys.  I am aware of the outside forces on a boat, but I would like to make my Volunteer track as straight as possible.  It wanders even with no wind or waves on the pond.  There is one regatta I go to where the navigation course is judged on how many "strokes" of the TX levers one makes, so every time I give the rudder a little kick, that's 2 strokes.  I will try moving the ballast aft to make her down by the stern and see if that helps.

Dave
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CGAux26

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Re: Loyal Class Tracking
« Reply #10 on: August 29, 2011, 04:03:52 AM »

I shifted ballast slightly, and moved the CG aft about 5/8".  That's all I could get without doing some more extreme changes.  Today I ran the boat and it seems to track better.  It is "by the stern" just enough I can see the difference.  Thanks again for the help, guys.    :-))
Dave
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Shipmate60

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Re: Loyal Class Tracking
« Reply #11 on: August 29, 2011, 09:55:51 AM »

Glad to help.
Great looking model too.

Bob
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farrow

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Re: Loyal Class Tracking
« Reply #12 on: September 03, 2011, 09:41:41 PM »

Hi, if that is your model, well I must say she looks great, but unlike the real ones she is not nearly enough by the stern in trim.
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farrow

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Re: Loyal Class Tracking
« Reply #13 on: September 03, 2011, 09:44:54 PM »

Have posted a pic which shows thier typical trim.
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CGAux26

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Re: Loyal Class Tracking
« Reply #14 on: September 03, 2011, 09:49:13 PM »

Dodes, while you were writing I was shifting ballast aft again.  Tomorrow I will run the boat again and see if the tracking improves some more.  Maybe I will try her on towing my LPG barge, too.
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farrow

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Re: Loyal Class Tracking
« Reply #15 on: September 04, 2011, 12:04:39 PM »

Hi mate, I used to pilot them regularly between Greenock and the Kyle Loch Alsh ports in my youth, then I remember that the bottom of the transom was just under the waterline and the bow was always well up. Because the boats where supposed to take cargo or up to 175 passengers accordding to thier MoD status, when they where loaded thier tippiing point was under the bridge. But I never saw them used to capacity, except on fleet reviews etc when they serviced the anchored vessels and took sight see'ers around the fleet. As for towing the Felsted at Chatham was known to occaisionally tow camel salvage cassions between Dover and Chatham and they where a heavy tow even for a dog class tug, otherwise although they had a tow hook aft they did little towing, although once Bill Hannah in Devonport used one to lift of the C851 a 750t capacity oil barge off a jetty into the Hamoase and rebirth it with so that a vessel could be undrydocked (then that was mainly for a gesture I believe).
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CGAux26

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Re: Loyal Class Tracking
« Reply #16 on: September 05, 2011, 04:36:20 AM »

The run today proved Dodes idea of making her more by the stern.  She now has her tail (transom) in the water.  With no wind on our lake the boat would run 100 yards or more straight with no correction.  Problem solved.  Thanks again.
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farrow

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Re: Loyal Class Tracking
« Reply #17 on: September 05, 2011, 06:00:06 PM »

Hi, glad to be of help, looking at your pic she does look more like the originals.
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