Advice on ballast

Ebornstein

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I need some advice on adding ballast to my Duffy 31. It is a bit bow heavy ( not sure why ) and I was think of adding some ballast to the stern. I think I need about 600lbs and was thinking of using lead bars.

Any thoughts would be appreciated.

Thanks
Eric
 

DBM

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Ebornstein

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DBMS,
She was built in 1998 by Atlantic. She does not have a windlass or any rode in the bow. She is kept in Lake Erie so I suspect the problem is there is less buyouncy in fresh water which causes her to sit on her lines funny.

I want to put a windlass on so it is only going to get worse. So I am going to need to do something.


Eric
 

jnoon

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DBMS,
She was built in 1998 by Atlantic. She does not have a windlass or any rode in the bow. She is kept in Lake Erie so I suspect the problem is there is less buyouncy in fresh water which causes her to sit on her lines funny.

I want to put a windlass on so it is only going to get worse. So I am going to need to do something.


Eric

I wouldn't think the freshwater would change the angle that the boat lays in the water. The reduced buoyancy should be consistent so that the entire boat may sit lower in the water, not just the bow. I agree with DBM, I would try to find the reason for the bow heavy attitude before adding the ballast.
 

Curmudgeon

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The difference fore and aft between the center of flotation and the center of gravity will cause a trim change along with sitting deeper due to freshwater allowance, but it would be minimal.
 

Ebornstein

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It's not really bad but I know it will be getting worse when I add the windlass. I have attached a picture of her sitting on her lines.

image.jpg
 

carey

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Great question!!! How do we determine proper distribution of weight? Is it just a matter of how she sits at the dock, or is it so hull specific that we must use moveable ballast and do speed trials until we come to the final determination? Is a Downeaster better off stern heavy? I would think so, but I am truly not a naval architect.
 

Ebornstein

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That's a good idea googinater I am not sure there is enough room in the stern for a tank. The fuel tanks run fore and aft one on each side. I might be able to get a bladder in there.
 

lobster783

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Just change the water line.:D Does is ride low when underway or just look bow heavy at the dock?
 

Ebornstein

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Now that's a great idea. You are right that I don't really need it. Usually fishing for walleye and steelhead. Not alot of need for live bait in the lake:sad:

I am ok using lead i have to figure out how to fasten it down so I can remove it later. I have heard of folks using steel shot I think.
 

carey

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No need to fasten it, as it won't likely move around. At least through the investigative phase.
 

Robert M

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I would recommend the drums also. I have the same hull my motor weighs aprox 1600lb and a 350lb gen on my deck. I believe we both have a built out down below, head , fridge , , besides a windless w/ 50' chain etc,
 
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Ebornstein

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Lobster783, I don't think she handles poorly under power but I am not sure if it could ride better. I get some standing water in the cockpit which I suspect is a result of her being bow heavy.

Carey
Right I would just lay them in there until I get the trim right.
 

Ebornstein

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Googinater thanks for the drum idea.

Robert M. The galley is up, no windlass (yet), just bunks and a head below. She is powered by a 200hp tamd 41 which weighs in at 1100lbs.

What year is yours? Does it sit on its lines properly?
 

carey

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I can't help but think that the lines are not a good reference, as they likely only relate to the original paint job, and not a scientific equation. Just a thought.
 

googinhater

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So your saying with the stanting water the deck crow pich is off not the wait you could re pitch the deck keep the wait off the boat in turn keeping the speed up fuel burn down but a go size project to do
 

Robert M

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Googinater thanks for the drum idea.

Robert M. The galley is up, no windlass (yet), just bunks and a head below. She is powered by a 200hp tamd 41 which weighs in at 1100lbs.

What year is yours? Does it sit on its lines properly?
Launched end of 2000
I have a cummins 6cta 430hp. Up front, there's a head with sink. Fridge , sink, windlass. I think she sits on her lines well , and the bow rides up , and is a dry boat. Two barrels on the back deck would be worth a try. You could mark them to keep track of optimal weight.
 
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