Grand Banks 46, bow heavy or stern light - or something else?

[Mayday]

Seeking wisdom. She’s a 2000 Grand Banks 46 Classic in excellent condition, but with a weight problem of sorts. Here’s the situation. The bottom paint at the bow waterline is maybe 1.5 inches above water surface. At the transom bottom paint is easily 5-6 inches. Amidship bottom paint is about 2 inches under surface. Obviously this is worrisome since blistering of the uncovered portion is a real possibility. Onboard twin Cat 3208TAs, 12 Kw Northern Lights, twin 375 gal. fuel tanks (located slightly aft of amidship behind the mains), ABT stabilizers 145 gal water tank aft and a 130 gal tank forward under forward cabin sole, bow thrusters, and on pulpit two anchors, one with about 200 feet of chain, the other 25 ft of chain and 100+ ft of nylon. She draws about 4.5 ft. Current she’s approx 50% full of fuel, 90% water. Question is why is she imbalanced and what to do about it. Thoughts??

 

[rslifkin]

First you need to figure out if she's actually out of trim or if the paint lines are just wrong or weird. Does water drain off the decks the way you'd expect, or does it pool forward in spots?

 

[Giggitoni]

I have a 1986 GB42. Therefore, not really an apple-to-apple comparison with yours. One difference I see between our boats is mine has both water tanks in the lazarette attached to the inside of the transom. My water tanks total 286 gallons or about 2,382 pounds. You have one aft 145 gallon water tank; about 1208 gallons.

I have noticed when the volume in my water tanks are low, the boat sits “bow heavy”, or stern light; about 2 inches down at the bow and 3 inches up in the stern.

The fuel tanks are about mid ships in our boat. Full fuel tanks “squats” the boat a few inches lower in the water. Not much change aft to forward.

Don’t really have any suggestions other than possibly remove the water from your forward tank and see how your boat sits in the water (with a full aft tank). Forward to aft and side to side weight changes make a large difference in attitude of my boat at rest.

 

[Xlantic]

You are talking about where the bottom paint is rather than the boot stripe. I assume there is a boot strip and below that is where the bottom paint begins.

If the bottom of the boot stripe is 1.5" above the water at the front and 5" to 6" in the back but 2" below the water in the middle the clearly the line is wrong.

In any case, the fact that she is low at the bow could be an imbalance of the water tanks. Are they both full?

 

[Frosty]

Here’s the situation.

The bottom paint at the bow waterline is maybe 1.5 inches above water surface.

Amidship bottom paint is about 2 inches under surface.

At the transom bottom paint is easily 5-6 inches.

I rearranged your sentences but changed no words. My question is this: At the transom you don't say whether the bottom paint is...

1) BELOW the waterline by 5-6" or ...

2)...whether it is SHOWING (above the waterline) 5-6". Huge difference.

Waterline always has to be perfectly straight, horizontally (as is the surface of the water).

So, regardless of what else may be going on, if #1 is what you meant, then the bottom paint line is whacky and not straight (we will assume your boat does not have a broken back).

If what you meant is #2, then you are bow heavy/stern light, most likely. That said, you might also see if you can determine if your bottom paint is painted to a the designed line or not (some boats have a score line or similar to show you where the builder intended the waterline to be).

 

[Mayday]

Xlantic, both water tanks are full and they drain simultaneously. Currently my fuel tanks are close to 50% full. I’m going to add another 25% to see if this affects how she lies. Thanks.

 

[Mayday]

Rslifkin, ur right to ask about water pooling. Yes, it does, on both port and starboard decks slightly aft of amidship. Also in the cockpit around the scuppers. Thanks for that.

 

[gsholz]

I'd try just using your water tank in the lazarette. Only fill tank in the bow when you are out for a week.
Another option is to move or add a few batteries for the house bank to the lazarette. Are your batteries in the factory locations?

 

[Comodave]

What about things like the shower drains? Do they drain properly? We had a 46’ trawler that had a cockpit that was maybe a design error. The water pooled in the wrong olaces and the shower didn’t drain. I added about 1300 pounds of lead trying to get it trimmed properly and never did. Assuming the bottom paint was done correctly then adding ballast may be the only way to trim it. However I doubt that a couple of batteries will do the trick. I would hire a naval architect to evaluate the boat.

 

[BrisHamish]

I have a slightly different GB46 (Europa versus the OP's Classic), so what I will post here please view in light of that.

First, I have no water pooling at any place on the decks / walkways of our 46 - all water drains aft.

Secondly, our 46 is decidedly 'stern heavy'. That is probably because I added a freezer and a hydraulic swim platform (both aft of the engine room). I have subsequently put the boat on a diet but, as with myself, the diet seems to work a little bit for a while and then the weight somehow comes back on...

Thirdly, our 46 has broadly similar weight engines / fuel tank locations to the OP's 46.

Fourthly, our 46 has the 'unusual' option of having three centreline fresh water tanks running forward of the engine room to up underneath the bed in the bow stateroom. So when we are full of fresh water (1300 litres total) the bow sits down better.

So what did I do with my pronounced 'bow up'? We put 500kg of lead ingots into the bow, the bow came down to where it should be (with the water tanks full), and the stern came up a bit.

Hamish.