Two questions?

[David Holloway 1Participant @davidholloway1]

I have recently bought the plans for a model tugboat (Cullamix, Hobbystore MM256), and have a couple of questions (I am a novice boat modeller, far happier with a lathe …):

 i) This model is about a metre long – what size/type of steam engine should I use to power it?  Does anyone know of a suitable engine, or rather set of castings/drawings?

ii) The plans are for a ‘bread-and-butter’) style of build – I am having trouble getting my head around proceeding from the plans  to cutting and assembling the layers.  Is there a book for beginners that describes how to carry out such a construction, for the beginner? Or some handy tips?

Thank you for any help you may be able to give

David 

[Paul TParticipant @pault84577]

Hi David

Bloody hell what a pair of questions, firstly with regard to the steam engine for a ready to run example have a look at the cheddar range but if you want to have a good play on the lathe then have a look at stewart turner.

Bread and butter construction is fairly straight forward as it is just a layered build but if you are having problems then post the plan on the gallery section and we will be able to help further.

Hope this helps

Paul  

[David Holloway 1Participant @davidholloway1]

Paul,

I’m not too sure whether to take that as a compliment …

What I was really after was the size of engine, say single or 2-cylinder, maybe stroke S x Bore B … Is there some kind of formula involving hull size, speed, engine size, pressure, etc. etc. ??

Regarding building the layered hull … I am at a loss as to how to  start – on the plan I have a set of half-cross-sections – do I make a set of ‘templates’ from plywood or somesuch so that I can then shape the hull to size?  Any advice more than welcome!

Thanks in advance,

David

[Paul TParticipant @pault84577]

Hi David

With regard to the steam plant I would suggest that you contact a supplier and they will be able to give you far better advice than I can.

As for bread and butter construction try the link below.

http://home.att.net/~kopfj/Pubs/BreadnButter/BreadButter.html

Sorry can’t help further.

Paul

[David Holloway 1Participant @davidholloway1]

Paul,

 The reference looks great – I’ve had a quick scan through it and, apart from what are either technical terms or Americanisms, it looks very straightforward.

Thanks a lot – I’ll investigate further about the engine while building the hull.

David

[HS93Participant @hs9317166]

Bread and butter is not that ideal for for steam as the plant neds to be mounted as low as posable in the hull, and youneed as much space as posable inside to alow for working on the plant and for heat to disperse . timber is not that good these days for plank on frame unless you are prepaired to spend a lot of money . think about plank on frame,

as far as steam plants, talk to people who are using  steam befor you comit to buy , there is a lot of unsuitable plants about , and a lot of people who think any plant will do. but a good start is a Cheddar plant now back in production and sold again by Stuarts,(who designed it in the first place) not the cheapest but it wuill out last  a lot of the otheres and it a tried and tested simple to use and will push most medium sized boats and spares are available if you ever needed them

Peter

[Phil ButtonParticipant @philbutton47234]

As far as engines go, I design and build my own steam plant (following well-trodden paths I hasten to add!).  If you want to run the boat with radio control of the speed and/or reversing of the engine, you will need a minimum of a twin-cylinder engine with the two cranks at 90degrees in order to be fairly certain that it will restart if it should stop at small regulator openings – a single-cylinder engine cannot restart if it happens to stop at top or bottom dead centre.

I use a rule-of-thumb for engine sizing based on a formula in a reprint of a 1920 book called ‘Machinery for Model Steamers’ (still available – try Amazon.com), which states the cubic capacity of the cylinder(s) in cubic inches as (L x B x D)/a, where:

L = waterline length in inches

B = beam in inches

D = average draught in inches

a = is a constant that depends on the length as below

       Up to 30inches length, a = 3000

       30 – 36inches length, a = 2800

       36 – 42inches length, a = 2700

        42 – 48inches length, a = 2500

        48 – 54inches length, a = 2300

        54 – 60inches length, a = 2100

If you want to build your own engine and are good with a lathe and hand tools, there are a number of plans and casting sets available for steam engines – e.g. from Stuart Turner or Reeves.

You will then need a boiler to match the engine – but that’s another can of worms!

[Trevor LloydleeParticipant @trevorlloydlee64722]

hello Phil.

Your rule of thumb formula from the 1920s is interesting, but surely the steam pressure and whether the cylinders are single or double acting needs to be worked into the formula  somewhere.

Trev.

[Phil ButtonParticipant @philbutton47234]

I agree, but I have not yet found any useful formulae to use in design – if you have anything useful I would be most grateful.

I find that the 1920’s formula is good for a first approximation as it usually gives an angine size that is on the generous side.

[Trevor LloydleeParticipant @trevorlloydlee64722]

hello Phil,

I replied to your posting on this thread on 18 Feb. I know you replied because I read it once, but have struggled to get back to it.

Neither can I find any replies there may be waiting for me somewhere to other postings I have sent out, even though I have ticked the box "Email me when a response is made".

I am new to this group and struggling to fathom out how the forum works.

 Please contact me direct by e-mail

trevane3 ‘at ‘ wmconnect.com

Thanks.

Trevor.  

[David Holloway 1Participant @davidholloway1]

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