Forum > Paddlewheels/Drive Systems

My first paddle steamer project - PS Waverley

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Peter Binns:
Although I have been making large scale RC model boats and ships of character and/or historical significance for the last ten years (see pics), I have never tackled a paddle steamer.  So, like probably dozens of other marine modellers before me, I have chosen to scratch build a 1:48 scale PS Waverley, but mine will be steam-powered.

Whilst I’m waiting for the ex-MMI plans to arrive (which I will scale up to 1:48 at the local architectural plan printers), more and more queries (some very basic) are coming into my head about the challenge before me. I’ve therefore registered with Paddleducks in the hope that some of you veteran paddlers will be able to answer some of my questions. Here goes:

1) At ‘service speed’ I understand that the paddle wheels of the actual vessel rotate at 52rpm. Will my model perform to scale speed if I gear down the steam drive to max 52rpm? If not, what rpm should I aim for? What compensation needs to be added to take account of the water resistance?

2) Finding paddle wheel kits of the correct size (ideally 115mm diameter x 70mm wide with 19mm paddle depth) seems increasingly difficult. The Graupner wheels appear to have been discontinued, but I am aware of the non-feathering styrene kits sold by Cayton Vintage Models, the brass kits from Mike Mayhew and those from Clyde Model Boats, although I can’t find any info on the latter two. Suggestions please!

3) I like to replicate the engineering as closely as possible, but is it worth going to the expense and complication of having feathering paddle wheels on a model of this size?

4) Where might I find a set of suitable bolt-on bearings for the paddle wheel shaft?

5) A wise gentleman at the International Model Boat Show last November advised me to always add extra hull depth below the waterline on paddle steamers to accommodate ballast and reduce their inherent instability. Do you agree, and if so, by how much on a model that will be about 1.5 metres in length?

No doubt there will be more questions as I get into the build, but I’ll be grateful for any advice from more experienced paddle enthusiasts. Thank you. :)

derekwarner_decoy:
Hullo & welcome to PD's Peter

Your post is very clear looking toward the end of the finished model, however there are many underlying paths that need your research prior to simply building a hull & hoping for the best

Are you familiar in wood working in building a plank on frame vessel some 1500 mm long?
Are you happy or competent in building a functioning steam plant and drive from a number of component sources?
So, for simplicity, I have copied your post to a Q&A format
As you progress, there will be many, many questions…do not fear as many have been down this watery path before
I hope these assist

Derek  :beer
___________________________________________________

Q1) - At ‘service speed’ I understand that the paddle wheels of the actual vessel rotate at 52rpm. Will my model perform to scale speed if I gear down the steam drive to max 52rpm? If not, what rpm should I aim for? What compensation needs to be added to take account of the water resistance?
A1) - to understand you must research as much as you can about model Waverley vessels, however a mathematical rule in scale = multiply the actual shaft speed by the square root of the scale for the models shaft rotation speed

Q2) Finding paddle wheel kits of the correct size (ideally 115mm diameter x 70mm wide with 19mm paddle depth) seems increasingly difficult. The Graupner wheels appear to have been discontinued, but I am aware of the non-feathering styrene kits sold by Cayton Vintage Models, the brass kits from Mike Mayhew and those from Clyde Model Boats, although I can’t find any info on the latter two. Suggestions please!
A2) - your research here will be invaluable……..our archives have a number of threads relating to the not so simple wheel builds

Q3) I like to replicate the engineering as closely as possible, but is it worth going to the expense and complication of having feathering paddle wheels on a model of this size?
A3) - if you intend your build to be a scale like build of Waverley, then feathering paddles would be used

Q4) Where might I find a set of suitable bolt-on bearings for the paddle wheel shaft?
A4) - the Small Parts & Bearings WEB site will confirm the availability of miniature plumber blocks complete with ZZ sealed stainless ball bearings

Q5) A wise gentleman at the International Model Boat Show last November advised me to always add extra hull depth below the waterline on paddle steamers to accommodate ballast and reduce their inherent instability. Do you agree, and if so, by how much on a model that will be about 1.5 metres in length?
A5) - the unit of measurement you are looking at is kilograms of weight of the hull + the sum of the weight of each & every subcomponent in your build…..this is the vessels displacement………your research will then alert you to the actual displacement of PS Waverley…….then compared to your planned 1:48 scale model……from there your choices will be clear…………………you will also learn about multiplying by the cube roof of the scale for such calculations ..............[although a little muddied]  :porkies

Peter Binns:
Dear Derek

Thank you for your welcome and for your comments on the initial questions I asked. Much appreciated. Can I respond as follows:

i) Yes, I am well-used to building large scale hulls plank (or in some cases plywood) on frame. In fact all my models so far were built plank on frame from scratch. It is a part of the process I enjoy and find the most satisfying. I will never buy pre-formed hulls!

ii) With regard to steam propulsion, I have no experience whatsoever, but I plan to invest in a ready-made Libra steam paddle plant from Clevedon Steam http://www.clevedonsteam.co.uk/products.html#Libra Paddle Plant Kit. However, I will have to learn how to couple it with the paddle wheels correctly etc.

iii) A1 - I've seen this mathematical rule elsewhere, but it seemed counter-intuitive for the scale rpm to be several times the rpm of the actual vessel's paddle wheels. This is what I found on another member's PD post:

'Standard practice is to multiply the rpm of the real ship by the square root of the scale to achieve a proper scale speed (i.e the speed at which the model will produce the same wave effect in miniature as does the real ship).

So for a model at 1:48 of, say, the current Waverley, the following would apply:

Maximum of Waverley's engine (in 1947) = 56rpm. Square root of 48 is 6.93. 
Model maximum rpm therefore 56 x 6.93 = 388 rpm.

Waverley's service speed rpm = 42.  Model equivalent is 291rpm.

These of course are rpm in the water.'

If this is correct then I will do what it says!

A2) I don't suppose I will uncover anything your members don't already know, but I will pursue Mike Mayhew and Clyde Model Boats for specific product details.

A3) Of course, I would prefer to be as true to life as possible, but I did read somewhere that in actual performance terms, feathering wheels would not make any difference on a model of this size. Open mind on this.

A4) Thanks for the advice.

A5) Ditto.

In the meantime I do hope others will chime in!

Peter Binns
Constantine Model Dockyard, Falmouth, Cornwall

Mike:


  Hi Peter.

  Welcome to the forum.

  Have a look at my Jeanie Deans. A sister ship. It is 1 48th scale and about 65 inches long.
  I made my hull an extra 3/4 inch deep. In your one the weight of the steam plant and ALL
  the fittings and allow 4 lbs for above deck fittings plus a good safety margin. You will need
  to work out weight of boat against weight of water displaced. Not easy. Keep all weight as
  low as possible.
  In a wind of 3mph or less mine goes well but more wind and it will start to lean a bit.
  You will need 1 inch extra or more. It will also start to make the ship heavy to move.

  I made my own paddle wheels, Quite easy. On this ship they are non feathering but are
  there for show. They make very little difference to a model ship speed.
  On my Dromedary build they are working ones. It does look good when on show.
  I have a geared motor giving about 400 rpm. I find 150 to 200 rpm looks good and a scale
  speed.
  But a lot will be on the shape and size of paddles.
 
  In my ship I used stainless steel bearings in brass holders for the paddle shaft. It does
  make them very free running. And 5mm stainless spindle.
  Any questions please ask.

  Looking forward to seeing pictures of your build.

  Mike.

Peter Binns:
Hi Mike

That's very helpful. Thank you. Just marshalling all the facts at present. Planning is everything. May be a little while before I lay a keel!

Regards

Peter

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