Author Topic: Ballasting  (Read 2862 times)

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freightliner009

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Ballasting
« on: February 05, 2014, 13:25:08 »
I'd be interested to hear from anyone on how much ballast they used in their tugs. Obviously every boat is different.
I have this job to do on an all wood 1:24 scale tug, I'm looking at 12V batteries at the moment, this one http://www.componentshop.co.uk/12v-9-0ah-sealed-lead-acid-battery.html weighs in at 2.6Kg. I sure hope this isn't going to be too heavy.

Is the notification of replies not working? I always tick the box but seldom get any notifications even though there are responses.

Andy
Proud  father of a new Hobby Engine 1/35 scale Southampton tug and 1/24 scale hand crafted Zeeland tug

Model Tug Man

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Re: Ballasting
« Reply #1 on: February 06, 2014, 07:54:13 »
Best way to determine ballast required is the bathtub test. My current project is 5' so the tub is out. I purchased a kiddie pool and will use it to test when the time comes. The placement of the ballast is important as well as how much. I have several different size and weight of lead weights to augment my batteries. I am using SLA batteries and keep them low in the hull. I am expecting the finished model, fully ballasted, to weigh in around 70 pounds. All of this will be removable since my gimpy backside will not be lugging 70 lbs to the pond. A small amount of weight higher up will dampen out some of the motion and make your tug look a little more realistic in the waves but be careful with this. You don't want to compromise stability either. Once you have your batteries and weights set in the hull make sure she will right herself from a significant roll and doesn't go on over. If you are using your tug for towing comp Umi suggests having the weight as close to the pivot point as possible to facilitate turning.
VGJQ

west coast tug

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Re: Ballasting
« Reply #2 on: February 06, 2014, 10:05:21 »
I gave up on the tub long ago.
Try some 2 X 12" and 2 bar clamps out side on the grass or drive way with some poly wrap for a liner it might leak but you just let it rip when your done the grass will like it.
You only have to make it about 4" bigger than the hull.
Another idea is find out who's got a kiddy pool on the block.
Gary

gribeauval

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Re: Ballasting
« Reply #3 on: February 06, 2014, 10:56:11 »
What you need is a very understanding wife!!

I got permission to build a permanent test tank at the bottom of the garden.

Mike

des

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Re: Ballasting
« Reply #4 on: February 06, 2014, 15:11:24 »
I agree - the bathtub test is the only way to do it - whether you use a bath or swimming pool doesn't matter - the test is the same.

You should previously have some idea of where you want the boat's waterline to end up at.  When you put the boat in the water, with the battery and all heavy stuff installed, see where the boat actually sits.  Then apply ballast to get it down to where you want it to be.

MTM has it right - the location for the ballast is just as important as how much.  It should be located as low down in the hull as you can get it, for stability.  Placement fore and aft is a little more fiddly, as the boat probably will need more ballast at one end than the other;  placing the ballast near the centre of buoyancy will tend to bring the hull down more or less evenly, while placing it near the pivot point will make the boat more "lively" when steering (not necessarily an entirely good thing).

Sheet lead is often used for ballast, simply glued in place where you need it.  Lead shot is also good, as it can be poured into place, brushed around until you are satisfied, then fixed in place with a good dose of spray glue.

Des.

mike_victoriabc

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Re: Ballasting
« Reply #5 on: February 06, 2014, 16:43:09 »
If using lead shot - consider placing the shot in ziplock bags (double bag perhaps) rather than glueing it in place.
I have a large hull that someone filled with lead ballast and it's too heavy to easily shift about. Previous owner tried to drill out the lead and thank goodness stopped before drilling through the hull!
Sheet stock or bags might be a better way to go. Just a thought.

tbone

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Re: Ballasting
« Reply #6 on: February 09, 2014, 23:56:41 »
I read an idea somewhere of putting wax paper into the hull, pouring lead shot in and once ballasted out epoxy was poured over it; the end result was a formed weight that fit perfectly into the hull.

On a different note, I have access to a large lead block but don't have any idea of how to cut or turn it into usable pieces.

Calimero

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Re: Ballasting
« Reply #7 on: February 10, 2014, 04:14:17 »
I'm at the same stage. I need to ballast my small springer tug. The first "bath trials" show that I'll need approximately 2kg of ballast (4lb+) to get it to "sit right".

I was a little surprised at first that it would require so much ballast, but at the same time the internal volume of the hull is actually quite large, hence the "huge" amount of ballast needed.

I'll use the hull as a "work barge" for all sorts of projects: camera boat with a gimbal, underwater camera, ... I want to be able to move (and remove !) ballast inside the hull so that I can level the boat with whatever equipment it is fitted. I've looked into steel shot from a local diving shop, but it's not working out as I hoped.

I'm waiting for small pure lead ingots. Each will be around 350g (3/4 pound). The inside of the hull is covered with hook&loop (Velcro) so that I can relocate everything (battery, ballast, electronics ...).

Mike's idea (ziplock) sounds interesting too.

freightliner009

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Re: Ballasting
« Reply #8 on: February 10, 2014, 10:59:37 »
Calimero,

Have you got an image of your Springer tug?

For my hand made Zeeland I hope it isn't too much more as I have a limited space (the only space) for the battery and electronics. The old guy that built it seemed to know what he was doing so I'm hoping the accessible part is big enough to hold everything necessary as the rest of the hull is all sectioned off with the exception of the small rudder area.
Proud  father of a new Hobby Engine 1/35 scale Southampton tug and 1/24 scale hand crafted Zeeland tug

PHILNZ

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Re: Ballasting
« Reply #9 on: February 10, 2014, 20:33:19 »
Tbone as for your lead block delimmea . set the block up on bricks with one corner pointing down then blow torch it . set a moulds or a tin up under it to catch the melted lead, you can adjust the flow with taking the heat away.
Worth a try i reckon.

des

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Re: Ballasting
« Reply #10 on: February 10, 2014, 21:50:50 »
In Tasmania, just south of Hobart, is an old colonial building known as the Shot Tower.  Apparently they used to melt lead at the top of the tower, and let the molten lead drip into a water bath at the bottom.  This method resulted in almost spherical balls of lead shot, for use in the muskets of that time.  Similar method, but smaller scale, should give acceptable results for model tug ballast.

Des.

Calimero

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Re: Ballasting
« Reply #11 on: February 11, 2014, 14:14:07 »
Quote from: freightliner009
Calimero,

Have you got an image of your Springer tug?

I just started a new topic for my springer tug build

See post #2 or the build log entry on my site.