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[TurboTyne]

 Hello
I am hoping to get some advice regarding my dream of building a model of the WW1 R-class destroyer HMS Rigorous.


I have obtained the plans for this ship from the NMM and am now puzzling over what scale to build it at. My first question concerns the displacement to be expected for a model hull. I gather that theoretically, the displacement of a model equals the displacement of the prototype divided by the scale factor cubed. The prototype had a displacement  of 890 – 1222 tons. If the above rule is correct, then, assuming a displacement of 1073 tons,  models built to scales of 1:48, 1:60 and 1:72 would have displacements of 21.7, 11.1 and 6.4 lbs respectively.  So I am wondering, are the results of this calculation realistic and reliable in practice? i.e. do they form a useful approximate guide to what I should expect in a model?


The M and R-class ships had similar hulls and these were very narrow in proportion to their length. Thus, for the same three scales the lengths and, beams of the hulls would be 69 X 6.7 ins, 55 X 5.4 ins and 46 X 4.4 ins.  Of course internal space will be less than this.


I hope to fit steam propulsion so I am inclined to go for the 1:48 scale because of the greater displacement and greater internal space.  However, I am a bit worried that with a water-line length of 69 ins, I would end up with something conspicuously big and also awkward to handle. I have little experience with sailing model boats, so any advice will be most welcome.


One further question concerns the propulsion. The original ship had 2 screws driven by separate sets of turbines. However, I will undoubtedly need to drive both from the same engine. Would the fact that both propellers will always turn at equal speeds adversely affect manoeuvrability to any great extent?



Thanks for looking at this.
Regards, Mike
 

[Robert Davies]

A further consideration or two (or three!)

1. A length of hull over 53" may be tricky to fit in a typical car (I just measured my backseat!) - make sure what you choose can be transported to the lake!
2. If you run in freshwater your displacement figures may be a bit off - or is it when in saltwater? (I can never remember!)
3. Water doesn't really scale too well. Bearing that in mind, running both shafts at the same speed should be fine, but you may need to increase the size of the rudder arrangement anyway, or have a 'display' rudder - and a larger 'running' rudder - which may just be a sleeve over the display rudder.

A WWI R Class  eh? I feel a thumbing through Jane's Fighting Ships coming on!

-Rob

[Plastic - RIP]

 Hi – my view may differ from others on here – personally, I’d look at the steam plant that you intend to use as this will be the limiting factor for size & weight.
If you have identified your hulls and worked out your approximate displacements, then if you add the weight of the hull, the steam plant, your radio gear & batteries, add some weight for your superstructure & fittings (which will be dependant on your preferred materials and construction methods) then the scale to use may become self-evident.

I would always go bigger if possible because you can use additional lead ballast in the bottom of the hull to deal with any stability and waterline issues.
As mentioned above, the question of size will also be determined by the size of car you have to transport the model around.

In my experience, both props acting as one won’t be too much of a problem unless you want to do tight courses at regattas. The length of the hull will always make a boat that is slightly unresponsive to rudder.
You could cheat a bit and fit a bow-thruster to aid handling, but I get the impression that you’re into accurate scale modelling.
 

[TurboTyne]

Thanks for all those 3 points Rob - especially point 2. I had completely forgotten about Plimsoll lines. I just checked this out and it seems that when loaded to the same depth, the weight is about 2.5% less when in fresh water compared to in sea-water at the same temperature.

I must measure my car - although 20 lbs would not be too much for the roof rack maybe?

Thanks, Mike

[John W E]

hi there Mike
 
Looking at your profile I noticed that you are a fellow Geordie - I live 9 mile away from your goodself in Sand-dancers country.  I am sure you are aware that there are 4 good clubs in the vicinity of the North East - Heaton; Tynemouth; South Shields and Saltwell Park; oh and I forgot about Roker one.... so thats 5.     
 
Heaton and South Shields Clubs are heavily into Steam - as well as yachts; South Shields Club on a Sunday morning have a club - if you ask for either John Neilson or Bob Kirtley - they will be able to guide you through all of your questions regarding stability and building single engine driven twin screws; as they both build steam driven models.   Bob will no doubt try and turn you towards flash steam; high speed records or straight running.   John has built a very similar model to the one you are building - although it is semi scaled, it looks the part and goes well.
 
aye
 
John

[Robert Davies]

20lbs may be ok with adequate restraints - It would make a heck of a torpedo in an emergency stop otherwise!

Try and make as much of the weight in the hull demountable, so that the actual weight up there on the rack may only be 10 -> 12lbs. When you put the ship in the water, then you can re-add the ballast, and ancillary weight. It makes transport so much easier!

The other factor to consider, is that having weight high up on a car is inefficient and adversely affects handling, much more than when that weight is closer to the C-of-G (both static and dynamic).

[Shipmate60]

If using a steam plant take into consideration the weight of the water in the boiler which in that hull I would assume is above the waterline.


Bob

[TurboTyne]

If you have identified your hulls and worked out your approximate displacements, then if you add the weight of the hull, the steam plant, your radio gear & batteries, add some weight for your superstructure & fittings (which will be dependant on your preferred materials and construction methods) then the scale to use may become self-evident.


You could cheat a bit and fit a bow-thruster to aid handling, but I get the impression that you’re into accurate scale modelling.

Thanks for those comments Plastic.
Re: the steam plant, I'm making this myself, so weight is somewhat adjustable within limits of course. But the radio gear is an unknown quantity for me.

Hmm bow thruster is definitely out for me. I'm not too bothered about great performance - main things are that it is reasonably true to scale, floats the right way up and goes at a realsitic looking speed, bearing in mind the R-class ships could do 36 Knots.
Thanks, Mike

[hmsantrim]

Hi Mike.
 commercial fittings are available at  1/72 and 1/48 scales.  Could always try and pick up a cheap trailer on Flea bay for the 1/48 model.
 frank 

[TurboTyne]

hi there Mike
 
Looking at your profile I noticed that you are a fellow Geordie - I live 9 mile away from your goodself in Sand-dancers country.  I am sure you are aware that there are 4 good clubs in the vicinity of the North East - Heaton; Tynemouth; South Shields and Saltwell Park; oh and I forgot about Roker one.... so thats 5.     
 
Heaton and South Shields Clubs are heavily into Steam - as well as yachts; South Shields Club on a Sunday morning have a club - if you ask for either John Neilson or Bob Kirtley - they will be able to guide you through all of your questions regarding stability and building single engine driven twin screws; as they both build steam driven models.   Bob will no doubt try and turn you towards flash steam; high speed records or straight running.   John has built a very similar model to the one you are building - although it is semi scaled, it looks the part and goes well.
 
aye
 
John

Thanks for that suggestion John. (Sorry to dissappoint but I'm not really a Geordie - but incomer from the South). I am a stones throw from the Heaton club.  I was wondering if there are any steam people there. I really should get in touch with them. Actually my steam plant will (hopefully) be flash steam - but electronically controlled rather that flat out racing - along the lines of Flashtwo's Vital Byte. Trouble is my electronics stuff adds to the weight.
Regards,  Mike

[TurboTyne]

If using a steam plant take into consideration the weight of the water in the boiler which in that hull I would assume is above the waterline.


Bob

Thanks Bob. Actually I hope to use my horizontally coiled flash-type boiler, so this should help keep the weight low down - but these ships were not very deep unfortunately. I've read that sometimes people add extra depth to their hulls to help with these issues but I would prefer to keep to scale if possible.
Thanks,, Mike

[TailUK]

Hi Mike.
 commercial fittings are available at  1/72 and 1/48 scales.  Could always try and pick up a cheap trailer on Flea bay for the 1/48 model.
 frank

Have a look at Steve Pickering's website "Chylds Hall Model Shipyard"  he does a lot of bits in 1/48th scale for WWI warships.
http://www.chyldshallmodelshipyard.com/

[hmsantrim]

HMS Rigorous is a Glasgow boat with three chins will you have smoke coming out them all
frank
http://www.clydesite.co.uk/clydebuilt/viewship.asp?id=2008

[TurboTyne]

HMS Rigorous is a Glasgow boat with three chins will you have smoke coming out them all
frank
http://www.clydesite.co.uk/clydebuilt/viewship.asp?id=2008

Hi Frank
Don't know how the internals will pan out yet. Be good to use all three stacks.
But how much smoke actually came from oil-fired boilers? Wasn't it normal to avoid smoke production as much as possible?  Trouble is, since a condenser is not going to be feasible, it will probably be white steam that comes out rather than smoke. Still, if I get a boat made at all I'll be pleased.
A trailers a good idea but I only need a trolley since I guess I could push it to the pond from home.
Mike

[TurboTyne]

Have a look at Steve Pickering's website "Chylds Hall Model Shipyard"  he does a lot of bits in 1/48th scale for WWI warships.
http://www.chyldshallmodelshipyard.com/

They look like a very useful array of fittings. Hmmm, I only hope I eventually get to the stage when I actually need bits like that.

Thanks,  Mike

[dreadnought72]

^ I saw three of these vessels at the weekend in Glasgow. Narrow hulls, but practical. Surely "as big as possible" is the watchword for a steam version?

As for fitting in a car, I can get my 87+" Dreadnought in a Nissan Note, without sweary words and with a whole inch or two left over.



 

Andy

[onora]

In 1/48 scale it's about 5.5ft  give or take

[TurboTyne]

O.K. the comments so far confirm my inclination to 1:48 scale, (especially the photo of Andy's Dreadnought in a Note).

Thanks very much for all the replies.

But what about my first question - is the estimate of the displacement at 21.7 lbs a reliable, although approximate, guide for planning weight of hull, machinery, superstructure etc?   

Regards,  Mike

[Plastic - RIP]

If you have a copy of the plans at your chosen scale, you can approximate the total expected weight by working out a simplified volume up to the waterline of each compartment created by the bulkheads into a series of separate square boxes and triangular boxes (with a bit of give & take here and there).
If your boat is round under the water, substitute cylinders and cones for boxes.

If you work out the total volume by adding them all together in litres, then that approximates to kilos.

It's not super-accurate but you'll be in the close ball park.

[dreadnought72]

But what about my first question - is the estimate of the displacement at 21.7 lbs a reliable, although approximate, guide for planning weight of hull, machinery, superstructure etc?

Hi Mike - yes, it is: though to allow a certain "wriggle room" for ballasting I'd be aiming at maybe 75% of that for the all-up build.

Meanwhile, Plastic's suggestion is worth doing, since by estimating the hull volume bulkhead-by-bulkhead you'd be able to roughly calculate out where the centre of bouyancy lies along the keel. That would probably be the ideal point for your boiler: as water is boiled off you'd only get a change in waterline.

Andy

[derekwarner]

Mike...........

1. you had previously stated a typical weight of 890 – 1222 tons
2. so let say 1000 tonnes...[assuming displacement tonnes]
3. the answer to understand scale reduction is tonnes divided by the cube root of the scale 
4. so 1000 divided by 48......divided by 48.... divided by 48 = 9.04 kg

This estimate is based upon the nominal 1000 tonnes.....but clearly confirms your 21.7 lbs is in the ballpark........ 

Sorry  to mince units of measure...........Derek

PS... the methodology offered by plastic is also the most intelligent estimation/calculation method when the final answer or result was unknown....

[TurboTyne]

Thanks a lot for all the further responses.

So for the immediate future, I know I should think about an all in weight of no more than about 17 lbs. but I will, in any case, get the plans out, turn on Excel and follow Plastic's suggestion.

I guess that, at the same time, I could roughly calculate the surface area of the hull and use that to estimate the weight of the empty hull.

Thanks again, 
Mike

[tonyH]

Hi Mike, you'll find that the 17lbs goes very quickly when steam is involved!
 
One thing you'll also need to consider is where the weight is located. Generally, where the boiler is and this is normally controlled where the stack is.
 
Tony

[TurboTyne]

Hi Mike, you'll find that the 17lbs goes very quickly when steam is involved!
 
One thing you'll also need to consider is where the weight is located. Generally, where the boiler is and this is normally controlled where the stack is.
 
Tony

Hi Tony
Thanks for that comment. Yes, I'm beginning to realise that even at 1:48 scale, I shall have to compromise on the complexity of the steam plant that I install. But I really hope to be able to keep with using an electrically pumped paraffin burner (see thread in Steam R&D) since that gives great control and will allow fuel to be stored anywhere - e.g. low down and in the  same location as the war-tanks of the original ship.

Hopefuly the fact that the R-class had three stacks will allow a bit of flexibility in positioning the boiler. It will all be a very slow development process.

Regards  Mike

[dodes]

Ref her displacement, unlike the Merchant Navy, the Royal Navy quoted displacement is her actual weight displacement in water, standard which is no fuel or ordinance and full load which is every item of store. The merchant navy is a measurement of internal cubic capacity and varies according to what type of vessel and classification society.