Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[RichM]

Hi Guy's,
I'm just thinking out loud here and wanting thoughts, comments and points of view from other like minded model boaters.
I've got some lovely original plans, from a couple of model shipyards, that are more than workable and useful to make a couple of really nice modern trawlers that in the current UK fleet.
My questions are:

What scale do you like to work in best of all and why?
What scale is best for modern trawlers? (In respect of buying fittings parts, etc)
Size isnt really an issue (To a point!!!) for me as I have a large workshop and a large vehicle to transport within. Weight within reason isnt an issue either and me and my wife are both reasonably fit so we could 'lift' together.
I'm thing abount sizing the plans to 1/24th Scale, but it may be possible to got to 1/16th if others could steer me in the right direction, however, I'm just sounding others out really whilst im gathering my research materials together for starting a build of one of the trawlers very soon. It certainly wont be a quick build but by god will it be enjoyable and fufilling when its done.
The full sized ship is 34m Long, 10.5m Beam and 7.95m Draught. A Twin Rig Shelterdeck Trawler.
Cheers
Cheers

[steve mahoney]

What can you lift out of the water comfortably (with ballast and batteries)? Your wife might not always be so keen.

[tonyH]

If you know the displacement, then it'll be easier to help

[RichM]

If you know the displacement, then it'll be easier to help

Whats the easiest way to work that out Tony?

[Tug Fanatic]

I am sure that the mathematicians will come up with something more precise but I use block co-efficients.

The basic technique is that you take a known length, breadth & main hull underwater depth in centimetres and work out the volume in cubic centrimetres. As your hull isn't this nice block shape you multiply it by a factor to get the model volume weight. Somewhere around two thirds works well for tugs & trawlers which are basically pretty bulky hull shapes.

So if your planned model is say 100cm x 25cm x 8m (underwater) the block would be 20000cc  which multiplied by 0.66 gives 13333cc or 13.33 litres which weighs 13.33kg!

This obviously is only a guide number ball park estimate but has worked for me.

How many people do you want your 1/16th model to carry? 

[tonyH]

Or, the easy way is to start with the real ship so if, for example, the actual 34m vessel you're looking at weighs (displacement - often shown on the plans) 2000 tonnes (2,000,000 kilos), then the weight at 1/50 would be approximately 2,000,000 divided by 50x50x50 which comes to 16 kilos*.

In a similar manner at 1/16 it would weigh 2,000,000 divided by 16x16x16 which comes to just about 488 kilos or just about half a tonne.
I've found it to give a good starting point, especially if you're either building very large or very small; certainly enough to tell you if you can either move it or if it's going to float

Just one thing to note is that the displacement you're looking for is with all the stuff like fuel/cargo etc. on board so, the displacement when it goes to sea and not just for the bare boat.
Good Luck
* Not far away from Tug!

[Capt Podge]

It's not my thread but thanks for putting your answers up guys.


TonyH - I'll be using your method for future builds. 


Cheers,
Ray.

[Tug Fanatic]

.......................In a similar manner at 1/16 it would weigh 2,000,000 divided by 16x16x16 which comes to just about 488 kilos or just about half a tonne.........................

* Not far away from Tug!

I didn't know that we had a prototype weight!

My calculated method comes out at 454kg for the 1/16 model which is remarkably close. The same model at 1/24 (1.42 metres length) calculates at 137kg. Both sizes are way heavier than I would want. 

My models have tended to be freelance & the formula method lets you play with dimensions to get the answer that you want whilst TonyH method is great if you have the information.

[roycv]

Hi all, are the original numbers correct?  I multiplied 34 x 10.5 x 7.95m then used a factor of 0.6 for the block co-efficient and that comes out to about 1600 tons!
Surely a 100 foot trawler weighs in at about 60 tons or so.
Also accepting a model at 454 Kgrms is nearly half a ton!
Anybody agree with my numbers or is there a mistake there?
regards
Roy

[Tug Fanatic]

I agree your calculation & that 1600 tonnes sounds like a very big number for a 34m ship. A tugboat of that size would be around 800 tonnes.

Is the draught of 7.95 metres correct rather than being just a single point with the average hull draught being much less?

[tonyH]

I've no idea what the various displacement figures often given actually mean!

I've just looked at a figure of just under 3000 tonnes for a modern trawler about twice as long (Tait 229) but although it says "gross" does that include the permitted catch? It might be worth posting the question in Working Boats because that could affect where the line is. 

[RichM]

The vessel I want to build is the 'Aalskere' K373.
A modern Twin Rig Trawler from Orkney.

[roycv]

That vessel has a draft of 6 metres.
https://www.vesselfinder.com/vessels/details/9841562
For details
Roy

[tonyH]

AHA!  She's 11 metres and not 30+. Sad but true!!
Holy Miscalculations Batman!

[Tug Fanatic]

AHA!  She's 11 metres and not 30+. Sad but true!!
Holy Miscalculations Batman!

As I read her data she is 35m x 11m with a draught at the bow of 4.2m. I cannot read the stern depth markings on the pictures that I have found.

This is a picture of a model of the boat which gives a pretty good idea of the hull shape:
https://www.facebook.com/photo/?fbid=2508249055979290&set=pcb.2508250022645860

[tonyH]

Ah, misread the sizes, confusing the 11/34 as metres/ft for the length and totally ignored the beam
So Gross Tonnage 644 gives 370Kg at 1/12, 45Kg at 1/24 and 14Kg at 1/36 possibly, unless I've made another "*******"