Ballst

[The Dogs Pollacks Brother]

A poser for all you displacement hulls out there!

The old Colvic has a fair bit of ballast in her....bags of builders sand, iron ingots and old chain to be precise.......but the position of some of it has got me thinking.
The ingots are in the center of the hull in forward position and there is some very heavy chain at the stern,again in the center of the hull. The engine is mounted between these two areas btw. These seem, in theory at least, to be in the ideal place,i.e,center of gravity if you like.
The bags of sand are placed on the hull near the edges...2 at the stern end, one port,one starboard and one mid-ships to port (the batteries are mid-ships to starboard to balance it up)

My question is, will the sand bags act in such a way as to give a see-saw effect in a beam sea? Should all the ballast be as central as possible?

The bilge keel of the Colvic is fairly deep near the stern then gradualy gets shallower as it runs forward......is an option to pour the sand into the keel or is that a big no no for whatever reason? its about 3 inches wide and 12 to 14 inches deep at its deepest. Its usualy full of nasty old bilge water and lost tools ect and I recon I could easily loose the sand in there.

Also, how do I know if the boat even needs ballast? It was there from purchase and the previous owner said he felt he needed it for the Bristol Channel....where I don't fish!

Any ideas or experience greatly recieved guys
TIA
Jeff...TDPB

 

[Searush]

Weight at the ends does tend to encourage see-sawing, but I doubt that the amount you are talking about will be that noticeable. Yes, you can pour the sand into the keel where the weight will be more effective, but the sand will then be permamently wet, won't it?

OK so that increases its weight, but will the permanently damp sand have any detrimental effect on the surfaces it is against? Is there any iron or steel there that will rust & expand or just rust away?

What will happen to the displaced bilge water? Can it be pumped out easily? Can you create a sump for the strum box? Will it just slosh about in the lower lockers ruining anything stored in them, might it appear over the top of your flooring?

Just a few of the issues that I would want to consider before changing what exists.

 

[The Dogs Pollacks Brother]

Good points well made Searush........any **** in the bilge water currently stays where it is but if it does slop about the hull it may well block the bilge pumps? Thanks for the input and in the meantime I may just take the sand bags out all together and try the boat then.....at worse all I have to do is put them back in!
Thanks
Jeff

 

[rob2]

The general principle of placing internal ballast is that weight added around the keel will have little effect on the turning moment, whereas ballast at the ends will make turning more sluggish. Colvics are fairly heavy boats to start with, so I'm guessing that the previous owner was happy to go out in quite heavy conditions for his fishing and added the ballast to dampen her motion. I guess the ballast at the stern is to keep her bow up out of the waves.

The only way to find out how much effect all this is having is to take it out and see how she handles. The bag of sand to port, balancing the batteries may need to be replaced with something else to maintain her balance, but try to thing of something which has a purpose rather than dead weight.

I used to sail on a Trapper that carried a spare for every system. When the owner stripped it all out to race, the boat was a different creature - much faster in light airs, but not quite as comfortable in rough conditions.

Rob.

 

[The Dogs Pollacks Brother]

Rob.....my thoughts were like yours. The colvic with its engine and gearbox is a heavy boat anyways so I may well try her without the bags at least.
The ingots are another concern the more I think about it....it appears at first glance to be a lot of weight in one place and I am not sure what, if anything, they are placed on. I will need to remove a few and investigate further I think.

In reality, could I expect any more speed from the old girl with less ballast?
or am I being too optomistic with the hull and a 1.5 BMC chugging away!

 

[Searush]

Thinking on; "Bristol Channel Conditions" probably refers to the big tides & shallow water - which implies nasty (read lively!) wind over tide conditions. If you are mostly pottering around Dale then you are less likely to meet such conditions - err, apart from the shallow water that is!

 

[rob2]

Lightening the load will make the boat slightly faster in calm conditions, if the prop pitch allows you more revs than you're getting now and she should accelerate better, but you may not notice the difference in practical terms. As conditions worsen, there's a balance between the extra weight helping her punch through waves and what speed allows you to maintain control, so we're back to trial and error!

Rob.