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Ballasting/trimming


MtB

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My boat is a bit low in the water at the back and a bit high at the front. There is no ballast in the stern to remove. 

 

If I add ballast to the front will this bing the back up slightly? Or will the bow simply sit a bit deeper? I can convince myself either way so would appreciate the thoughts of the team. 

 

 

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2 hours ago, nb Innisfree said:

It will seesaw around the centre of gravity. 

No, it'll seesaw around the centre of flotation, which is usually not the same place as the CoG. But this is only exactly true if you move a weight in the boat, if you add weight to one end the CoG shifts as well, so the seesaw point is somewhere between CoG and CoF.

Edited by IanD
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4 hours ago, Mike the Boilerman said:

My boat is a bit low in the water at the back and a bit high at the front. There is no ballast in the stern to remove. 

 

If I add ballast to the front will this bing the back up slightly? Or will the bow simply sit a bit deeper? I can convince myself either way so would appreciate the thoughts of the team. 

 

 

Why not get a few friends to stand on the bow and see what happens every boat is different

Edited by Halsey
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Exactly as Ex Brummie says, filling our tank from 1/4 to full (1000 litre tank) does exactly the same, maybe 6 inches down at front and about 2.5 up at the back. I use the rudder visible above the waterline as a quick measurement of tank water level.

 

...............Dave

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5 hours ago, Mike the Boilerman said:

My boat is a bit low in the water at the back and a bit high at the front. There is no ballast in the stern to remove.

 

There is though - it's called a K2, (or a Glennifer, or whatever).

Put in a nice sensible modern engine, and you probably will need ballast at the stern!

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9 hours ago, Ex Brummie said:

If I fill the water tank from 1/4 full, the stern rises 1 1/2" - 2", whilst the bow drops 3"- 4". The quantity of water is about 170 gallons.

That would be pretty much my experience with a 60' boat. For a more extreme outcome, to enable me to paint the stern bands and the rubbing strip above the uxter plate, I put a couple of IBCs on the tug deck and filled them with water, thereby raising the stern well clear of the water. So, yes, I think you could achieved your desired result Mr Boilerman.

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With Mike's boat I suspect you have a double whammy of a big heavy engine and a long swim which reduces buoyancy at the stern.  Boats with long swims are harder to trim because of the buoyancy issue and the lack of movable ballast.  I reckon by the time you have added enough ballast to get the trim right, the entire boat will be unreasonably low in the water. 

 

 

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Suggest you adopt the suck it & see policy put weight in the front end & observe result no Idea about now but in the days of a definitive channel  having the boat ballasted/loaded to be "down by the head"fore end lower by 1to2 inches improved steering & channel following counter just flat on standing still aids "chucking back"reversing with minimum cavitation& requires less time /throttle to suck down & motor away with min cavitation probably a no go now days with shorter than full length boats with a draft that will float on damp grass+the lack of dredging

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1 hour ago, X Alan W said:

Suggest you adopt the suck it & see policy

 

This is my only option really. It's just that acquiring say 3cwt of Avery weights at £25 each to try it is gonna cost £150, and quite a lot of effort getting them to the boat. 

 

Edited by Mike the Boilerman
Arithmetic!
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