Adding Ballast

[donncha]

My father and I bought a 30ft Falmouth pilot about a year ago and have done a lot of work on her since, she is currently in the water on a swinging mooring. The idea of adding ballast comes from her tendency to roll quite a lot in any sort of sea. She does have quite a large cabin structure which doesn't do us any favors in terms of windage and height of main boom, but even so.

There are steel baffles in her bilges and a very solid floor. This may be an indication that there may have been ballast in her once upon a time. We don't have any drawings, but as far as I am aware the falmouth pilots were very similar to each other. She is long keeled and weighs 7 metric tonnes (according to the crane). She draws about 4ft of water but she floats bout 6 inches higher the her waterline.

My question is would adding ballast lower the center of gravity enough to give us a noticeable difference in stability, performance isn't as important to us in this context. I was thinking of adding a good few sandbags and see how she sails, if necessary casting some pigs of lead and stowing them properly for a more permanent solution.

Pictures here(all taken before all the work):
http://www.flickr.com/photos/donncha15/sets/72157603720357766/

 

[mormargh]

I will let you know shortly. I have a 30ft pilot cutter of (allegedly) six and a half tons and found her a bit livelier than expected in any dort of sea. As a result I have just put some lumps of ballast in here and there and will be moving it around to see if it makes any difference. Watch this space.

 

[JesseLoynes]

If you are adding ballast to alter the way she rolls, I assume that it will be most dependent on how far this ballast is from the axis of rotation. Have You got room to put the ballast deep down in the hull?

I've not played the ballast game myself yet, but it seems to be a very individual thing, depending on each hull shape, internal distribution of weight, rig and a personal feeling of how you'd like the boat to behave. Most advice seems to be: "try it"! Not hugely helpful I know, but possibly the best way forward. Just make sure that you spread the loading as much as possible and everything is secured against movement.

 

[cliffordpope]

I've done a lot of ballast calculating and moving on a smaller scale boat (21 feet) and it does make an enormous difference.
Ballast right down in the bilges will reduce rolling.
Think about longitudinal distribution. If you put it all in the centre she will pitch more. Even distribution is probably the best, in proportion to the section and displacement.
You can also use ballast to adjust the trim, fore and aft, as a result of sailing trials, so altering weather or lee helm tendencies.

You can of course calculate what weight you need to achieve a given additional draught - just draw a scale waterline cross-section on graph paper and count the squares to find the area, multiply by the required depth, to give water displacement = weight of ballast needed.

 

[chrishelen]

Why dont you try it and see?you can use bags of sand in those heavy polythene bags that dont leak(dont want sand in the bilge before anyone pipes up) and then move it about to best effect then once you have it right swop the bags for lead weights.you can make these yourself,but thats another story.i have used this method on a few boats and it works.hope this helps.

Chris.

 

[donncha]

Thanks for the replies, I do have easy access to the deepest part of the bilges so this would probably be to my benefit. I think I shall get a good few sand bags and just try it. I have heard that adding to much ballast can have adverse effects on the stability, as in, if she is a very "stiff" boat then as soon as she starts to roll there is a higher chance she will go over. Anyone heard this before?

 

[chrishelen]

What you need to do is get the centre of gravity as low as possible,in other words the lower in the boat the weight the better,thats why lots of boats mine included have most of the ballest in the keel,but i have a few lead weights in the bilges to help as i sail alone mostly.but some boats are more lively than others,its in the hull design.

 

[Tranona]

Looks like a Warrington Smyth design 9 tonner. If it is you should be able to get hold of the original drawings. Rodney was a well known and respected naval architect who ran Falmouth Boat Construction.

Does look a bit high in the water in the piccy.

Hope this helps

 

[dombuckley]

I went for a sail in my 6 tonner once without trimming ballast (approx 1/4 ton) on board; the difference was quite amazing - she didn't feel anywhere near as stable.

Draft should be about 4'8", so floating 6" above her marks is about right. You probably need about another 2 tons in her, as she would have had big steel water tanks in the bilge plus some pig iron trimming ballast.

When adding ballast, make sure all tanks are filled, and all cruising gear on board (personal gear, dinghy, sails, anchors and cables, etc) - this will set her down at least a full inch, and also goive an indication of whether she needs trimming also. Remember to leave her slightly light at the stern (about an inch or so) when nobody is onboard, so that she comes level when you have a full crew in the cockpit.

 

[fisherman]

Have you tried getting hold of lead lately? Price is through the roof. Maybe stainless steel punchings in plastic bottles, but all scrap is expensive, it's the Chinese pushing the price up. Double bag the sand, the plastic bags bio degrade.

 

[ctelfer38]

Where are your water tanks? Thought about moving them into the deep bilge you describe? - or adding to your water carrying capacity by adding new one's? Ok - when they are empty - you are where you are now; but that can be very useful for example when drying out against a wall etc. Just a thought - cheaper too!! /forums/images/graemlins/cool.gif

 

[donncha]

Water tank is a flexible 100 liter one at the moment. It's mounted on the starboard side just below the waterline, the diesel tank is on the port side. I would consider adding water tanks into the bilges if the sand bags work out. As far as the bags themselves go I have found these to do the job well in the past:
http://www.surplusandadventure.com/shopscr1462.html

Also thank you very much Tranona for pointing out that she is a Warrington Smyth, I looked around the net and I believe that you are absolutely correct.

 

[fisherman]

Been wondering where to get decent bags, thanks. Shame they don't mail the sand as well! The polyprop ones should be tough enough, I put a B&Q rubble bag outside so as not to soak up the muck

 

[cliffordpope]

When you have finished all your experimenting and determined precisely what weight you need and where, consider casting blocks of concrete.
These can be made to optimum shape for each location, and of a size you can easily lift.

It's a lot cheaper than lead.

 

[monkey_trousers]

if you're any where near the tyne I've got heaps surplus ballast - discovered about 2 ton of it boarded up in the forecabin! way up above the water line as well, so I'm going to ditch it. there's a variety of bits, railway lines in 1 foot lengths, sash weights that are about 2 foot long 3" in diameter and stupidly heavy and quite a few strange looking triangular pieces, 3" thick, each side of the triangle maybe 12" and jeez they're heavy I can only just lift one of them!, maybe something else of 'railway' provenance??

 

[donncha]

Thanks for the offer monkey_trousers but unfortunately I am in Dublin.

Thats a good idea regarding concrete Clifford_Pope, I shall look into it when we decide on the final specifications.

 

[monkey_trousers]

the offer stands for anyone else that needs any though

 

[graham]

The effect on stability will be greater than you might expect.As the boat sits deeper in the water the waterline beam will increase especially near the bow and stern.

. Im wondering about more ballast in my boat,I seem to need to reef earlier than similar boats .

One thing to be aware of is the stiffer the boat the more stress on the rig as the boat stands up to her canvas instead of heeling and spilling the wind.