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[justboatonic]

Any suggestions for doing this easily (if there is such a way!)

I've found I've had to add ballast to Drumbeat which was a surprise because she has two 6v SLA's on board! Also found that she had a slight list to port! Looking at the battery positions, they look to be on the centre line so I can only assume the list is due to the sea crane and diner in the deckhouse contributing to the weight on one side. Either that or its my lack of building skills!  ???

Im intending removing the SLA's and going to nimh so I'm going to need a LOT more lead in her!

Anyway, trial and error with strips of 6" lead from the local diy seem to have sorted it. Do any of the experts here have any suggestions how to make ballasting both to the water line stem to stern and port to starboard easier!?
Ta.

[Shipmate60]

justboatonic,
If the SLA batteries are on their side ensure that the terminals are not on the same side.
These batteries are lighter on "top" where there is an air space.
I usually start to think about ballasting when the unmovable running gear is fitted.
Just a rough ballast in the bath before the deck goes on to ensure I can get to the batteries.
As long as it isn't too bad you will know the rough area where the batteries will sit.
I make up wooden battery holders to keep batteries tight but don't glue in till at the pondside for trials.
I tack with superglue then when all is as I want when home mark the battery box, remove it quick clean up and epoxy it in.
Any port and stbd trim can be achieved with small amounts of lead.

Bob

[justboatonic]

Cheers Bob. I never knew that about SLA's! yes, they are on their sides since upright they would have been too high.

I made a couple of trays for the SLA's to sit in and also cut a couple of rubber bands in half and laid the two strips along each tray. The idea being the friction of the bands on the SLA battery sides would create some resistance and stop them moving abot. Seems to work.

Thanks for the tip about trial ballast. I'll have to remember that for future builds! 

[6705russell]

I must admit i have never used lead in any of my boats, i always used sand inside sandwich bags whichi find easier to move around the hull and manipulate to finely ballast my boats.

Russ

[Shipmate60]

6705russell,
The last model I ballasted was a 1/72 Type 21 Frigate.
She took 12 lbs plus 2 x 6 volt 10 Ah batteries. Lead was so much easier.
I usually ballast with batteries but couldnt with her as framing widths were wronf and had to gat ballast as low as possible.
She would have turned into a sand barge!!

Bob

[oldiron]

Any suggestions for doing this easily (if there is such a way!)

I've found I've had to add ballast to Drumbeat which was a surprise because she has two 6v SLA's on board! Also found that she had a slight list to port! Looking at the battery positions, they look to be on the centre line so I can only assume the list is due to the sea crane and diner in the deckhouse contributing to the weight on one side. Either that or its my lack of building skills!  ???

Im intending removing the SLA's and going to nimh so I'm going to need a LOT more lead in her!

Anyway, trial and error with strips of 6" lead from the local diy seem to have sorted it. Do any of the experts here have any suggestions how to make ballasting both to the water line stem to stern and port to starboard easier!?
Ta.

  In order to ballast my vessels, I assemble them until the bulk of the weight is in place, including batteries. I make a small rack to hold the batteries in position so they don't move when on the water and start creating a list problem. I mark the water line on the hull as per the drawings, then place the whole lot in the bath tub (with water). Then I place a level across the gunwals and proceed to pour in shotgun shot into areas I feel need the ballast to bring the hull down and level to the water line. When I'm satisfied, I mix fiberglass resin and pour it all over the ballast to seal it in place. Using this method I haven't had a bad one yet and they always sit on the water line .
oldiron

[Howard Q]

Hi to all.
Having just completed a large(ish) model, the need to ballast was a premium also the need to prevent a hernia was a priority. I used as suggested lead shot purchased from my local gunsmith, this was put into the self seal bags of differing sizes, then at the pond side the model was loaded with all the necessary batteries etc, the bags of ballast were placed at convenient points to bring her down to the waterline,the bags can be sealed with duck tape on return to home; making a neat but flexible package.
I appreciate this means that each sailing will be ballasted on site but you will have a dedicated set of weights to put on board, it seems to work quite well, it also leaves me to remove or launch the model without weight. Less damage to both parties.
Howard Q

[Warren E]

justboatonic,

When ballasting I try NOT to put the "weights" on the centre line.  I put them side by side but as far from the centre line as possible.  This is a little trickier to get the balance "just right" but it dampens the rocking of the boat from side to side, especially in wavy conditions.  Inertial physics supports this idea.

Warren Ervine, P.Eng.

[Damien]

justboatonic,

When ballasting I try NOT to put the "weights" on the centre line.  I put them side by side but as far from the centre line as possible.  This is a little trickier to get the balance "just right" but it dampens the rocking of the boat from side to side, especially in wavy conditions.  Inertial physics supports this idea.

Warren Ervine, P.Eng.

Perhaps i'm showing my ignorance of marine hull dynamics, wouldn't this interfere with the self righting characteristics of the hull

[DickyD]

Warren E is right. It works as he says.

[derekwarner]

This was discussed a few weeks ago......... Derek

http://www.modelboatmayhem.co.uk/forum/index.php?topic=25211.msg247786#msg247786

[shipwright65]

it is common practice to ballast a ship in this manner (weight on the sides away from the keel) when running light. slows the roll time down and makes for a comfortable passage. so no reason why it shouldnet work with models as well

[Ghost in the shell]

adding lead in the bottom to compensate for the difference in weight between the SLA and the ni-cad pack will probbably mean she is more stable.  I found that changing from a 12ah to a 4.5ah+lead plates in a sydney star improved her handling, also was able to drop the battery 10mm further down in the hull

[yorkiej]

it is common practice to ballast a ship in this manner (weight on the sides away from the keel) when running light. slows the roll time down and makes for a comfortable passage. so no reason why it shouldnet work with models as well

The above is very true, but it is the weight at a certain height above the keel which makes the difference between a stiff ship (or ship model) and a tender ship (or ship model). A ship with too much top weight will roll slowly and lean over in a wind, whereas a ship with too much bottom wieght will 'flick roll' (Fast roll) just like the little fat man in a budgie's cage. A look at the plans for a bulk (ore) carrier will show upper outer wing tanks (either side just under the deck) for water ballast. These are to raise the Centre of Gravity upwards to adjust between stiff and tender stability.
this link explains all.
http://www.towage-salvage.com/files/stab006.pdf
It looks a bit technical but if you pick the bones out of it you will see the point.
Hope this helps.
Cheers
John

[tobyker]

polar moments of inertia, and stuff.