Weight relationship fore to aft

A

AKMel

New member
In a previous thread it was suggested I add a second battery. I did a search and there seem to be a lot of advice threads about technical aspects, cable size, etc. But none about weight relationship fore to aft.
Nor did I see any followup as to how those who moved a battery forward liked the ride change.

My question is: What proportion of weight should be forward?

Our 22 cruiser: Plans are to use the boat for multi-day cruising.
--No refer
--No windlass (might add one in the future if I get tired of using a buoy buddy.)
--Has nav, radar (w/arch mounted rear of cabin), and VHF.
--Has shore power and battery charger
--Has sink w/20 gal tank.
--One new looking group 24 wet cell battery in the starboard lazarette. No evidence there was ever a second battery, but switch for 1/2/both/off is present.
--115 Yamaha (377 lbs). Will add a 92lb kicker as a get-home backup.

With a second battery I estimate I will have 900 lbs in the stern.

Offsetting that amidships will be about 50 lbs of water under the rear dinette seat, 30 lb of eats, two people in the cabin (wife won’t say what she weighs). Add misc of another 50lb. (total approx 500lb amidships).

Well forward will be bedding and 17lb anchor and 20-30lb of chain and line.

Changing one battery forward doesn’t seem like a lot. But installation under the sink will be easier than installing in the busy lazarette.
What is your experience? Should I place the second battery under the sink?
Thanks, Mel
 
C-Dory's are sensitive to lateral weight imbalance too. On most boats there the starboard side tends to be heavier due to more stuff there. Adding a battery under the sink is not going to help that situation.

A better bet would be under the v-berth on the port side.

Also, batteries housed inside the cabin should be of the sealed type.
 
I'm not the technical guy here, but I think you're over-analyzing this. In the overall scheme, is moving 50lbs forward worth the time and effort?

I stand by, ready to be corrected
 
Mel: If you're gonna go through the hassle of moving one battery then you might as well move them both. You'll need to convert to the AGM type for safety reasons but the added bonus of that is that the AGMs weigh less. There is a Brat on here called Aurelia (Greg) who has done it and can offer some great insight.

Ferg: For our 25's I agree with you. Moving a little weight here and there won't do diddly squat. Lol. But for 22's , 19s and 16's then it's definitely worth the effort. My 19 and 16 were very sensitive. Moving the location of 2 batteries is almost like moving the location of a small person!
 
With respect to transferring weight on a boat,I think that the net effect of moving a 50# battery from the stern to the bow is 100#.
In so doing, you have relieved the stern of 50# of weight, and loaded the bow with 50#, so the net effect is 100# in the bow. Like having that small person walk from the stern to the bow.

andy
 
South of Heaven":27y1wd0e said:
Mel: If you're gonna go through the hassle of moving one battery then you might as well move them both. You'll need to convert to the AGM type for safety reasons but the added bonus of that is that the AGMs weigh less.
Click to expand...

I just replaced my automotive style wet cell batteries with 4 AGM's, and based on my back pain, both the AGM and wet cell weighed much the same :sad
 
island andy":bxveedzi said:
With respect to transferring weight on a boat,I think that the net effect of moving a 50# battery from the stern to the bow is 100#.
In so doing, you have relieved the stern of 50# of weight, and loaded the bow with 50#, so the net effect is 100# in the bow. Like having that small person walk from the stern to the bow.

andy
Click to expand...

Not quite. To get the equivalent effect you'd need to put 100# in the front to get the same effect but only if you left the original weight in it's original place. In adding the additional 100# you are changing the total weight which means the 50# you move has less of an effect.

You are also assuming that the weight you move from the back to the front is equidistant from the balance point (between the center of pressure and the current CG) at whatever speed you are cruising at. As speed increases the center of pressure moves aft (but the CG doesn't change).

So at cruising speed you might not have to move the weight as far forward to balance the boat as when it is sitting still. By the same token, balancing the boat at the dock, may result in a boat that is bow heavy when on plane.

If it were me and I was serious about doing something like this, I would remove the battery from the back and place it in the various locations I thought I might want to put it (without cabling it up) and go cruising for a bit to see which location works out the best from a weight and balance perspective.
 
It is a ton of work to move it to the bow area...I just did it and it involved much more work than you would think...plus even with me doing all the work it was an expensive modification...

Joel
SEA3PO
 
Thanx guys. Per Ferg perhaps I am over analyzing. In my search of the site it seemed there were a number of posts about moving batteries, which I took as a sign those owners think they have too much weight aft. There seems to be a lot of attention paid to the work involved but i found little about the performance results.

I think you may have misunderstood my question. Perhaps I didn’t present it well. I was asking whether anyone has worked out a proportioning ratio fore to aft. For instance, cabin load should be X % of stern weight (I’m thinking for average situations. I realize sea, fuel, passenger, and other load conditions vary, and we have trim tabs for minor adjustment). Perhaps no one has ever tried to work out a simple ratio before. It shouldn’t be hard to come up with one.

If you like the ride of your 22 cruiser, let's say with 3/4 load of fuel, when under way approximately:
How much weight is in the stern?
How much weight is in the cabin?

Or, for those who really want to simplify the question, were you happier with the ride and other factors when you moved batteries forward?

60 lbs doesn’t seem like much. When I do the math, with a full load, our cabin load is 56% of our stern weight. If I move the batteries forward to the cabin, that changes to 65%, which seems like quite a difference.

Yes trial and error will work. Wish I could easily do that. Unfortunately the boat is on the edge of the California desert for a few more weeks. I’m trying to get the boat outfitted right before I permanently take it to our remote location in Alaska. Resources and parts are readily available down south, and less expensive too. Thanks again. Mel
 
On our CD 22, in the balancing of weight between bow & stern it takes extreme weight to the stern before it can't be compensated for by trim tabs or permatrims or both with very little actual hazard caused if not balanced. On the other hand being overbalanced to the bow can be much more difficult to counteract & a extreme hazard in rough sea conditions. During our Alaska extended cruises we have varied in the very stern of the cockpit without making other adjustments for it, other than trim tabs & permitrims as much as 500 lbs in fuel weight without being concerned with the boat handling.

Jay
 
Hunkydory":21kan8ey said:
On our CD 22, in the balancing of weight between bow & stern it takes extreme weight to the stern before it can't be compensated for by trim tabs or permatrims or both with very little actual hazard caused if not balanced. On the other hand being overbalanced to the bow can be much more difficult to counteract & a extreme hazard in rough sea conditions. During our Alaska extended cruises we have varied in the very stern of the cockpit without making other adjustments for it, other than trim tabs & permitrims as much as 500 lbs in fuel weight without being concerned with the boat handling.

Jay
Click to expand...

Great safety point Jay!!! Better to have more stern weight than risk bow-steer dangers in big seas. I'm going to go with your advise.
 
Jay is correct... also, you are going to find that your AGM batteries are heavier than your lead/acid batteries...I went from 80# to just over 100#...I did size up to the next larger batteries though... to counteract the amperage loss in the long cables...which I sized up 2 sizes....

I think I probably did it more because I can't keep my hands off of any project I find...than need...it's the old shop teacher thing....

Joel
SEA3PO
 
AKMel":qf5fj406 said:
Hunkydory":qf5fj406 said:
On our CD 22, in the balancing of weight between bow & stern it takes extreme weight to the stern before it can't be compensated for by trim tabs or permatrims or both with very little actual hazard caused if not balanced. On the other hand being overbalanced to the bow can be much more difficult to counteract & a extreme hazard in rough sea conditions. During our Alaska extended cruises we have varied in the very stern of the cockpit without making other adjustments for it, other than trim tabs & permatrims as much as 500 lbs in fuel weight without being concerned with the boat handling.

Jay
Click to expand...

Great safety point Jay!!! Better to have more stern weight than risk bow-steer dangers in big seas. I'm going to go with your advise.
Click to expand...

Jay beat me to it, but he makes a very important point. Weight aft is easily negated with the trim tabs, and in rough sea conditions, (especially following seas) you do not want a heavy bow.

With that reasoning, my stern is intentionally loaded. I have 2 group 29 batteries, on in each lazerette, my inflatable is carried over the cockpit and the rack it sits on is stainless pipe (not tubing) for strength and stability. I don't carry a big cooler or have a fridge, but for summer forays, I have carried about 50 pounds of food supply under the table.

My one experience with bow steering was in 6-8 foot following seas with my dingy uninflated and rolled and on the cabin roof. None since moving it aft on the rack.

Put your second battery in the other laz, or move them both down and into the center between the tanks if you just feel you need to move something :wink:

Harvey
SleepyC :moon

1_10_2012_from_Canon_961.highlight.jpg
 
I think Harvey has the best solution....move them down...between the tanks..that would center the load plus it is a ton easier///

Joel
SEA3PO
 
I like that wink SleepyC. No I don't feel the need to move a battery. I want to leave the engine battery in the starboard lazarette. It's busy in there but everything works.
I only have one battery presently, and your earlier advice was to add another. Since we are remote, and there have been days when I only see one other boat, I need to do that. Redundancy is good up there. The question I face is where to put the second battery. I have two bilge pumps between the tanks already. Unfortunately no room for a battery box between them. I think I can fit a small generator in the space forward of the pumps for a nice fit. I desire low placement for center of gravity, but that might not be necessary on a dory where the floor is the hull. I will go with wet cell for now to match the other battery. I just want to do it right so I don't have to do it twice. Right now I am back to thinking starboard lazarette next to the engine battery. I haven't read any top-heavy complaints about that, and it frees up other space on a 22. Plus lateral weight will be offset by the 92lb kicker to port. I can move generator and ice chest if I feel the need to balance.
Thanks again guys. You are a wealth of experience for this newbie to C-dory.
 
My two cents- I purchased a Lithium Ion jump starter battery that will actually turn over a pickup truck diesel engine (Duramax/Powerstroke). Its the size of a cigar box and weighsut close to a carton of eggs. I take it on the boat when traveling and keep in the pickup when not boating.

Not cheap at around $125 but what is peace of mind worth?
 
We have a 19 so the heavy stern is noticed more than with the 22. We put two 70lb batteries under the berth along with about 100lbs of additional stored items plus carry another 45lbs at the bow when we have our trolling motor mounted.

Even with that nearly 300 additional lbs forward and the fact that our 70lb daughter nearly always rides up in the berth when under way, we still feel like the bow is much lighter and more bouyant feeling than the bow of our 25 ever felt. No handling issues and much improved visibility forward while at planing speeds. The boat just rides much flatter than it did before and the tabs and permatrim give the range of adjustment one would expect instead of always being nearly maxed out.

Greg
 
AKMel":2nnyz5wp said:
BTDT: Not a bad idea. I like creativity. Any idea on the life expectancy of the lithium ion pack?
Click to expand...

Good question. My lithium ion power tool batteries have been holding up well as has my iPhone and iPad batteries, so I'm assuming much the same results, but you know what "assume" can mean. You can also use it to run laptops, smart phones, ipads, etc.

The Microgravity 10 is made in the USA, and Hulltruth has a number of threads on them. Consumer Reports rated them #1, and I see my #10 model is now $200.

edit- If you have a shorted battery on your boat I suspect you could melt the small jumper cables, and even if the motor started I suspect it would die again shortly. If the start battery is hot to the touch you need to remove it from the system.
 
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