Simple ballsating

Hi I am designing a boat . A simple boat , but it will need ballast . Now rather that go through all the trouble of figuring out what I need , I would just like to use beach stones . I think this would keep it simple . Any suggestions ?
regards frank

 

Inside loose ballast is not that simple. If it comes loose it can either capsize you or damage the boat. Also, if the boat does roll over, it will fall on you. Look at some old designs that use stone ballast, and they will give you a good idea. However, it takes experience to pack the stones so they don't move or damge the hull.

 

You must mean a sailboat. Beach stones have been used for centuries, even millenium, and you can do that. I'm sure they're used today somewhere.
Ideally, the stones would be secured below the floorboards, since they can cause problems if you heel enough to shift them.
Smaller stones in an aggregate (small nested within large to maximize space-filling) can be made into a concrete by adding portland cement.
As a solid concrete ballast, it can now be molded into a keel and be much more effective. The addition of cement changes everything. From cement and aggregate to cement and iron is the next step. More density. Still very simple.

 

Cheap and simple are not the same.

 

i once saw a hillyard with tarred bilge filled with concrete nice and cheap but no bilge and nowhere to put tanks, also higher c of g

 

Even if you used iron punchings and lots of stone aggregate in the concrete mix, you'll be luck yo get 150 to 160 pounds per cubic foot of ballast. This is a disgustingly low figure for ballast. You really want your ballast in the 400 pound and up range (per cu. ft.) for ballast. Other wise it'll occupy the whole bilge and your CG will be considerably higher then necessary.

 

It depends on the boat design. An old-style rounded hull with a relatively deep full-length keel might accommodate loose stone ballast because the narrow bottom will keep it deep and together, always provided it never capsizes!

However, you wrote 'simple" and that might mean flat-bottomed, which will allow the ballast to move easily and keep it high which is bad for stability.

There are other considerations also: will the ballast need removal for transporting the boat for example. If we knew what size and kind of boat and what usage you had planned it would help the good folk on the forum to advise you better.

Why are you designing it yourself if you lack knowledge? The cost of a professional design is usually negligible compared with the cost of material and the effort of building a boat.

 

It's true that a concrete-based ballast is not that dense (150 lbs per cu ft).
However, water ballast is only 62-64 lbs per cu ft, and water is an effective means to ballast and right a vessel. The hull and rig design must contribute to the types of ballast one might use.
Not all sailboats are performance oriented, but practically any ballast can be used to make some sort of reasonable sailer. A lot of boats have been built with cement and boiler punchings, under 250 lbs per cu ft likely, and they've crossed oceans.
By most modern standards of performance, lead ballasts are considered the most effective due to lead's great density of over 700 lbs cu ft. Lead allows a reduced draft and less wetted surface along with extreme longevity and an abilty to carry more sail. Yet, there is an argument for cheaper ballast materials in more moderate performance boats. It used to be done all the time, and usually for reasons of cost.

 

I'm not saying it can't be done, but I do think it presents more problems then it solves, particularly if the engineering aspects aren't the strong suit of the designer.

In other words, based on the post, Frank is going to make a shape, guess at it's displacement, then toss stones in the bilge, weighing it down until it behaves properly (I'll assume). Very experienced builders have done this countless times, typically never venturing very far from what they know will work. I'm questioning if Frank is skilled enough for an endeavor such as this and have a reasonable expectation of success.