Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1] 2   Go Down

Author Topic: Why a Model Tug Towing loads so SMALL  (Read 7651 times)

chrise

  • Guest
Why a Model Tug Towing loads so SMALL
« on: May 21, 2009, 08:30:56 AM »

Which bit of calculating a model/full size towing/handling capability doesn't work & why?

If we take a typical tanker of 200,000 tonnes it can be handled in port by 3 tugs of 60 tonne bollard pull and is about 300 metres long.

Typically model towing tugs are 1/32 which gives a scale tow of 9.375metres or around 30 feet.

Typically a model towing tug has a bollard pull of 3kg (well mine does anyway) which is about 1/22400 of the real thing and scales to a tow of about 8.9 tonnes.

Typically a reasonable ship handling tug displaces around 300 tonnes or around 1/666 of the tonnage of the tow. Even if we assume a model weight of only 20lbs this gives a tow of around 6 tonnes.

So if we take the worst from the above we should be able to handle a 9 metre 6 tonne tow & be overpowered doing it. This is a vastly longer/heavier tow than anything that I have ever seen in model tug towing.

Why? If the answer is convenience then surely we are towing with models that are too large/powerful to be scale.

Please ease my feelings of cheating.
Logged

Capt Jack

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 221
  • Location: Southampton
Re: Why a Model Tug Towing loads so SMALL
« Reply #1 on: May 21, 2009, 09:02:26 AM »

Would you want to try and get a 9 metre tow into your sailing pond !!!!

But i do know what you mean, i have been allowed to push the large maned models that Warsash Collage use at Marchwood Lake, hard work but good fun and more inkeeping scale wise.
Logged

Martin [Admin]

  • Administrator
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 19,056
  • Location: Peterborough, UK
    • Model Boat Mayhem
Re: Why a Model Tug Towing loads so SMALL
« Reply #2 on: May 21, 2009, 09:05:04 AM »


 I can't get a "9 metre 6 tonne" tow in the back of my car?!....
Logged
"This is my firm opinion, but what do I know?!"    -   Mayhem FaceBook Group!

dreadnought72

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,865
  • Wood butcher with ten thumbs
  • Location: Airdrie, Scotland
Re: Why a Model Tug Towing loads so SMALL
« Reply #3 on: May 21, 2009, 09:30:19 AM »

I think your maths is spot-on. The model's bollard pull is on a (scale) par with the real thing, so the objects you're "tugging" correctly should be around the size you mention. Turning to real world experience, we know we can shove a 30' narrowboat with one hand, and I suspect three model tugs would have no problem (slowly) moving one of these around in calm conditions. But it wouldn't be very quick (just like the real thing) nor very exciting (ditto) compared to using smaller tows.

Maybe the question should be "can you make a nine metre tow that'll fit in a car?"

...I think you could, at a pinch. In a big car. Water-ballasted (nesting) boxes that could be bolted together pond-side might work. Or a bow/stern structure with some form of fabric covered spaceframe in-between?

Andy
Logged
Enjoying every minute sailing W9465 Mertensia

chrise

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #4 on: May 21, 2009, 09:46:30 AM »

Maybe we can't fit a nine metre tow into the car but a number of towing venues - eg Ellesmere Port - have plenty of tows that are about scale. It would be interesting to see a competiton that included them somehow.

I go back to what I said about should tow boats be smaller & less powerful than we are currrently using if we are saying the tow is fixed. Springer size & powered tugs (not necessarily Springer shapes) would be much more scale than those currently used by many.

I know about boys & the size of their toys arguments but I am hoping we can exclude that  & concentrate on a more authentic experience.
Logged

dreadnought72

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,865
  • Wood butcher with ten thumbs
  • Location: Airdrie, Scotland
Re: Why a Model Tug Towing loads so SMALL
« Reply #5 on: May 21, 2009, 03:02:26 PM »

There's a few scale effects that creep in as you go for smaller sizes, but I agree - it could broaden the appeal of tugging. Especially if you could bring many wee tugs to an event in a boot.

Andy
Logged
Enjoying every minute sailing W9465 Mertensia

ministeve

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 620
  • washing the decks!!!
  • Location: birkenhead wirral
Re: Why a Model Tug Towing loads so SMALL
« Reply #6 on: May 22, 2009, 10:15:20 PM »

we at e port have sailed a 30 foot ship if you remember the aircraft carrier HMS invincible owned by a fellow mayhemer also one of the wirral lads has the san George which is 32nd scale at 15 feet in 3 sections and takes around 35 5 litre water bottles
Logged

catengineman

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #7 on: May 22, 2009, 10:23:39 PM »

would this be that push capt jack?

<embed width="448" height="361" type="application/x-shockwave-flash" wmode="transparent" src="http://i85.photobucket.com/player.swf?file=http://vid85.photobucket.com/albums/k49/adonis_spanner/MarchwoodLake016.flv">

 :-))
Logged

Umi_Ryuzuki

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #8 on: May 22, 2009, 11:22:57 PM »

Mine, and Toesupwa's models have handled and pushed 900lb+ (408.23Kg) tows...

So that would be, what, about 180 tonnes?
I would love a go at Arrows Invincible...   8)
Logged

lighterman

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #9 on: May 23, 2009, 08:30:29 AM »

thats why i stick to lighterage tugs and build barges (lighters) to scale the last 4 i made with the tug and the tow ropes out made a nice long tow 2 ranks of 2 came in at 8' the other boat users tend to pack up and run when i show up at the pond with that lot! "oh god it's him again... filling the pond with a load.. mutter mutter" if i could find some working lightermen at 1/32 that could slack the tow ropes as i turn i would make up less room {-)
Logged

ray123

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 439
  • mary marie cygnus gm33
  • Location: southeast england
Re: Why a Model Tug Towing loads so SMALL
« Reply #10 on: May 23, 2009, 08:42:48 AM »

the same with my canadian logging tug  its 22inches long 1;24th scale   to to scale log boom's  they would be 52ft long  (to long for our home water's   regards ray
Logged

poll

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 945
  • Location: Pontefract, West Yorkshire.
Re: Why a Model Tug Towing loads so SMALL
« Reply #11 on: May 26, 2009, 06:59:57 PM »

Hi Chrise, There are clubs like E/port  Wirral  Balne Moor That do have competitions through out the year, that any one can come along and have a go.
I do take on board what you say, But how do we scale THE WIND? To have a large tug do's help a little.  The tow's are 350/400lbs in weight
Cheers

John      Balne Moor M.B.C.
 
Logged

ministeve

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 620
  • washing the decks!!!
  • Location: birkenhead wirral
Re: Why a Model Tug Towing loads so SMALL
« Reply #12 on: May 26, 2009, 09:00:56 PM »

[url]if his works the vid is at Ellesmere port at one of our tug towing events the tow has about 15 5ltr sand bottles in her and is great to tow
hope you like if you search for ministeve on youtube you will find all of the vids i have uploaded
http://www.youtube.com/watch?v=SAX710p_Qe8
Logged

catengineman

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #13 on: May 26, 2009, 09:21:19 PM »

Logged

andyn

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #14 on: May 26, 2009, 09:59:46 PM »

Towing load small my left .....

Logged

ministeve

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 620
  • washing the decks!!!
  • Location: birkenhead wirral
Re: Why a Model Tug Towing loads so SMALL
« Reply #15 on: May 27, 2009, 01:12:46 AM »

how did you do that cat  :embarrassed:
Logged

portside II

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,519
  • tugs at rest
  • Location: Howden.East Riding of Yorkshire.England Near the banks of the river Ouse
    • goole model boat club indi site
Re: Why a Model Tug Towing loads so SMALL
« Reply #16 on: May 27, 2009, 09:43:33 AM »

Steve , thats one of the questions that comes to mind when i see you and your tug in action  :-)) .
daz
Logged
I like to build my boats to play with, not to just look pretty,so they dont !

tigertiger

  • Global Moderator
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 7,021
  • Location: Kunming, city of eternal springtime, SW China.
Re: Why a Model Tug Towing loads so SMALL
« Reply #17 on: May 27, 2009, 09:59:04 AM »

Which bit of calculating a model/full size towing/handling capability doesn't work & why?

...we should be able to handle a 9 metre 6 tonne tow & be overpowered doing it. This is a vastly longer/heavier tow than anything that I have ever seen in model tug towing.

...Why?

If I understand the question.
Why can't my model pull 6 tonnes?
This could be because the scale effect of water molecules. The water density does not scale down, so it would be like a real ship (1:1 scale) sailing in oil or even treacle.


Is my assumption correct?
Logged
The only stupid question is the one I didn't ask

portside II

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,519
  • tugs at rest
  • Location: Howden.East Riding of Yorkshire.England Near the banks of the river Ouse
    • goole model boat club indi site
Re: Why a Model Tug Towing loads so SMALL
« Reply #18 on: May 27, 2009, 09:25:25 PM »

sounds good to me TT  :-)) .
daz
Logged
I like to build my boats to play with, not to just look pretty,so they dont !

catengineman

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #19 on: May 27, 2009, 10:02:43 PM »

Which bit of calculating a model/full size towing/handling capability doesn't work & why?

...we should be able to handle a 9 metre 6 tonne tow & be overpowered doing it. This is a vastly longer/heavier tow than anything that I have ever seen in model tug towing.

...Why?

If I understand the question.
Why can't my model pull 6 tonnes?
This could be because the scale effect of water molecules. The water density does not scale down, so it would be like a real ship (1:1 scale) sailing in oil or even treacle.


Is my assumption correct?

I am not sure on what you say is! MY twin VS powered Ventur tug berthed a vessel with a weight of 5.5 tonnes yes the dead weight of the vessel is five and a half tonne! and the model moved it side ways to what we can say was a scale speed (myself, capt jack, the owners and the crew)

http://s85.photobucket.com/albums/k49/adonis_spanner/?action=view&current=MarchwoodLake016.flv

Logged

Navy2000

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #20 on: May 28, 2009, 12:55:36 AM »

Here are a couple photos of my tug Goliath which is based on the Mr. Darby tug that psuhes a barge that weighs in at 840 pounds anad she has no problem with handeling this barge. The tug has a pull of 18.8 pounds on a fish scale.





Duane
Logged

chrise

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #21 on: May 28, 2009, 05:59:15 PM »

The replies are really interesting - thank you.   :-))

I love the YouTube video where the load is heavy enough not to care a d--n what the tug does. Towing around where I live seems to involve a load so small & light it leaps to follow the tug.

840lb tows, 15 x 5 litre sand bottles etc - magic to my ears.

Scaling effects are interesting & I would appreciate comment from anyone who knows about full sized towing. I hear what you say about wind & treacle but what size/power/weight ratios are actually scale in behaviour terms. I appreciate the difference between a loaded & an unloaded model tanker in a cross wind & I am sure a full size tug skipper does as well. But where does scale effect/difficulty lie?

I have pushed a 30ft yacht around & I must admit that it did not feel like what I expect a super tanker might feel like but I am not sure why. Of course I might be completely wrong about the feel of a real tug pushing a real tanker. The most real towing/pushing that I have done was on the tug course at Gloucester docks - which was a great day out incidentally!

Chris

I hope to be a Balne Moor in August for the MMM listed "tug-in"
Logged

Navy2000

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #22 on: May 28, 2009, 10:24:25 PM »

One thing that I have told others with tug boats if they are useing a plastic prop is to take it off and throw that away and go with a brass prop and towing power will come up some. The plastic prop will flex while it is being turned and has lots of water to push. Brass props will not do this.



Duane
Logged

ZZ56

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #23 on: May 28, 2009, 11:24:54 PM »

Which bit of calculating a model/full size towing/handling capability doesn't work & why?

...we should be able to handle a 9 metre 6 tonne tow & be overpowered doing it. This is a vastly longer/heavier tow than anything that I have ever seen in model tug towing.

...Why?

If I understand the question.
Why can't my model pull 6 tonnes?
This could be because the scale effect of water molecules. The water density does not scale down, so it would be like a real ship (1:1 scale) sailing in oil or even treacle.


Is my assumption correct?

According to some books i read, the viscosity difference is overcome by the propeller of the model spinning at higher RPMs for equivalent power output.

I think Chrise is asking why we don't see 1:32 scale ships being used more often, with the obvious answer that such a model would be too large to be practical.  Someone has to store, tow and launch it.  At a smaller scale like 1:96, there are fewer options for tug models and they become much smaller and fiddlier.
Logged

chrise

  • Guest
Re: Why a Model Tug Towing loads so SMALL
« Reply #24 on: May 29, 2009, 08:22:00 PM »

I was really overstating my point but I am always surprised that even in "championship" towing events the tugs always look so big & overpowered compared to the tow but then "scale" seems so important in other ways.

I was at a towing event a couple of years ago where a very small Springer(ish) type tug with a couple of the smaller Graupner z drives (I think) - from Southend MBC I seem to remember - managed to tow perfectly well but everyone else had models at least twice the size & probably ten times as powerful. This guys efforts seemed worthy of much greater admiration. Instead I seem to remember him being told that he wouldn't have managed to look as good had it been a bit windier.

I know 30ft tows, at most venues & for most of the time, are impractical but then a handicap based on bollard pull, or a better idea, might be interesting.

I will now stand back, duck, & see what happens!!!
Logged
Pages: [1] 2   Go Up