Improving Trim By Moving The Batteries

G

ggray

New member
The recent post about trim tabs has me thinking again about moving the batteries forward to get the bow down...with less trim tab.

22 Cruiser with Honda 90, two batteries, one in each stern locker; trim tabs and Permatrim.

I haven't measured closely to make sure there is room under the vee berth, but if I could fit the two batteries there, I would be moving 85 pounds from the stern to the bow. There would be a lot of work to accomplish this, but I would think it would be quite effective in getting the bow down.

I would need to run heavier cables to the motor, and it would probably be best to use sealed batteries.

Is this a good idea? Would there be a problem at times with fuel tanks nearly empty? Has anyone done it?
 
Reasons it is not a good idea:
You are permanently transferring weight forward, and may risk bow steering and broaching if running down wind/seas.

Your cables for the battery should be 1/00 to 2/00 for that distance. Check out the weight and the cost.

Flooded lead acid batteries inside a cabin is not advisable. When charging the batteries give off Hydrogen gas, which is explosive.

Flooded lead acid batteries have acid, and if it spills it is very corrosive.
 
I have done this before with good results, albeit not on a CD 22. AGM batteries can be installed in enclosed spaces, in any position desired. (The nervous part of me had me vent my enclosure anyway). You need to carefully size the wire for the runs, and place additional breakers on the battery end of the runs.

This is NOT to say doing so would be a good idea on your boat, just that it can and is done routinely and safely. Your particular trim situation will dictate. I will say, however, that the CD22 was designed around the lighter Johnson 70 2-stroke, and that modern 4 stroke mains and kickers, together with dual batteries and larger fuel tanks, tend to make these boats quite stern-heavy.

Best of luck, Mike
 
The only reason I haven't done this yet is that I haven't had the time to work on the boat lately. My boat is very stern heavy. I'm going to use an agm in the vberth compartment just forward of the porta potty. I put larger trim tabs (12x12) on my boat and they are usually almost fully extended when running.
 
IMO, another thing to keep in mind is that the mountings for batteries in the bow probably need to be a bit sturdier than those for batteries in the stern. The bow is the moving part when the boat is in rough water, especially in a light hull like the C-Dory. These movements will impart accelerations to the batteries. Especially in those situations where the bow slams down. The relatively high inertias of heavy moving batteries can add higher loads to the mounts than what is experienced when the batteries are at the back of the boat.

Since forward mountings are not provided by the factory, make sure they are tough enough for your situation. Wouldn't want the batteries breaking loose and bouncing around.
 
IMO, another thing to keep in mind is that the mountings for batteries in the bow probably need to be a bit sturdier than those for batteries in the stern. The bow is the moving part when the boat is in rough water, especially in a light hull like the C-Dory. These movements will impart accelerations to the batteries. Especially in those situations where the bow slams down. The relatively high inertias of heavy moving batteries can add higher loads to the mounts than what is experienced when the batteries are at the back of the boat.

Since forward mountings are not provided by the factory, make sure they are tough enough for your situation. Wouldn't want the batteries breaking loose and bouncing around.
 
On my 22' I have a Honda 90, a Honda 9.9, two group 24 batteries, one on each side, add to that a two full tanks of gas and a 45 litre aux tank and then maybe more fuel and a cooler. I found that the boat was often rear heavy. My solution which killed two birds with one stone was to cut out the v-berth area and add hatches, which I filled with a lot of other stuff that cluttered up the cabin. The result with a heavier bow, is that the boat is more balanced with more weight up front. I have noticed a definite improvement in handling, especially when I get up on plane. Personally I would not move the batteries forward because of the many issues that others have mentioned in previous posts. I think that most boats that go out on extended cruises have lots of other stuff that could be moved forward instead.
 
I would say there probably isn't a more stern heavy boat out there at times than mine with shrimps pots, hundreds of feet of sinking line, 3 batteries, twin engines and often a kicked too, 30 gallons of extra fuel, 6 gallons of water, and a big cooler with ice all thrown in the back. There might even be a 30 pack of Coors back there.....lol....It trims out and it have never seemed to be much of an issue in my opinion. I've put around 2500 hours on the boat and I'd probably notice if it were a serious issue. The only real problem is wishing I had about 150 hp when it's loaded like this, because the boat only goes around 18-20 mph and when you're shrimping spot is 60-70 miles away, it's a very long ride.
 
OP said he would install " sealed" batteries. No need to discuss wet cells. OP said it would move about 85 #'s forward. How much weight does a anchor with chain add forward ? At least 85 #. Not enough to mention down seas running performance. How weight does an adult male sitting in the passenger front seat add to the forward ? More than 85#'s. Just use a large enough wire.
 
This is great! Wonderful comments that give me a lot to think about. Thanks!

Of course, the big variable is the weight of the fuel...or where it is. Ideally tankage would be centrally located so the state of being filled would not change the trim. But that's not what we have.

It may not be very practical, but the battery(ies) might represent a moveable weight that could be shifted according to fuel/passenger load, and conditions. Hmm....

Or move gear forward as has been suggested. But as we use the boat now, there is not much gear to be shifted. Perhaps we should not fully fill the fuel tanks as mentioned in the other post.

I'll consider moving just one battery to see what happens. I can look into how small an Odyssey battery would be that is capable of starting my motor. That could save a little weight back there. Not much, but it would be sealed, and may be easier to fit in the bow area if I decide to do that.

I do appreciate ALL comments that have been made.
 
Batteries weigh around 40 pounds each. Why don't you get 160 pound friend to sit where on the spot you want to move the batteries to and see if the difference in ride is worth the trouble. I doubt you will tell a difference. You could also remove 13 gallons of fuel (approx. 80 pounds), have an 80 pound child sit where the batteries would be and see if you notice a difference that way. Just some different ideas. I don't know if they would work. Good luck.
 
Or a bag or 2 of Dog food, a bucket of cat litter, or a gab of week killer or compost.

If you are just doing short day runs, you really don't need 80 gallons of fuel every time you leave the dock.

Harvey
SleepyC :moon

JC_Lately_SleepyC_Flat_Blue_070.thumb.jpg
 
Yes, I can try those things.

I don't have full tanks all the time, but when I fuel up, I top off. Perhaps I will back off that some.
 
ggray":2oy4eoui said:
Yes, I can try those things.

I don't have full tanks all the time, but when I fuel up, I top off. Perhaps I will back off that some.
Click to expand...

I cruise in the Northern VA area. For the most part I only use one tank, the port one to help counter my weight at the helm. Only when taking long trips do I fill both tanks.
 
My boat had a similar setup when I purchased it although the two batteries where in the bilge between the gas tanks (bad idea). I moved the starter battery to the starboard lazarette and the house battery to the space below the v-berth. I built a battery mount supported by vibration isolaters (see photo in my album). The batteries have separate isolation switches. The setup works well.
 
T.R. Bauer":q1ot8qkp said:
I would say there probably isn't a more stern heavy boat out there at times than mine with shrimps pots, hundreds of feet of sinking line, 3 batteries, twin engines and often a kicked too, 30 gallons of extra fuel, 6 gallons of water, and a big cooler with ice all thrown in the back. There might even be a 30 pack of Coors back there.....lol....It trims out and it have never seemed to be much of an issue in my opinion. I've put around 2500 hours on the boat and I'd probably notice if it were a serious issue. The only real problem is wishing I had about 150 hp when it's loaded like this, because the boat only goes around 18-20 mph and when you're shrimping spot is 60-70 miles away, it's a very long ride.
Click to expand...

This is exactly why I drink rum.
 
Do you really want the "Minimum" starting battery? I want a battery which will be reliable, even if it is cold or one has to crank the engine longer than usual for any one of a number of reasons. There is a reason that engine manufactures give a minimum of MCA (Marine Cranking Amps) The Honda 90 is in the 750 MCA range.

A #1 cable would be minimum. I would use a minimum of 1/0. there will be about a 30' run (up and back). #1 AWG tinned wire weight:.256 per foot= 7#, cost: Defender is $5.22 a foot x 30' = $156. Yes, you might get away with lesser quality and smaller cable in the short haul.

A fuse within 7" of the battery is necessary protect the wire, boat, engine and battery. There should also be a switch close to the battery. How about that bilge pump wire which comes off the battery?....or the terminal post you put aft? How are you going to handle the power to the console?

Playing the devil's advocate to give consideration of best practices.

Remember the more the weight of the battery, the more lead and greater the capacity. 40# is on the light side for a group 24. Most are at least 45# to 55#.
 
My wife likes to sleep in the front and so did my kids on long runs. That's way more weight that a battery or two. The boat really didn't seem much different - might have actually ridden better, but it did slow the boat down 2-3 mph. I don't think you're going to notice the huge difference I have inferred you think you're going to get by moving a battery. In crap seas, I insisted they move back to a seat....I suspect it matters, but it never has that much.
 
My situation in a CD 16 is much different, but might have some value as a weight shifting experient on a smaller scale. I did move batteries and fuel tank to improve balance. To really predict the effect of moving weight aboard would probably require a naval architect and even then you would have more numerical predictions rather than certainty of improvement. Part of the problem with experimenting with shifting weight on an existing boat is that it is difficult to model the exact final effect. You can put weight forward (bags of sand, etc.), but you will still have the batteries and fuel in their present locations. That is not the same as moving the present stern weight to mid ship. That is basically what I did.

I did my unscientific field trials by climbing as far forward as possible while someone else had the helm. That slowed the top end and I had my first real experience with bow steer when we hit a wake. I got bounced around side-to-side in the V berth. But it still seemed that shifting weight had the possibility of improvement. When sitting at the dock, my boat originally had the not uncommon C-Dory squat. I didn't have a permatrim at the time and didn't want trim tabs unless required and, it turns out, they are not.

I moved the batteries (start and house) under the passenger seat and the fuel tank just forward of that, resulting in a very slight bow down position at the dock. By the time I reach hull speed (probably about 4.5 knts), the hull is riding flat. With my "permatrim knockoff" OB fin, the boat trims nicely although I can force the bow down if I want. The stern is now lighter by 100# and the boat now carries a more weight than "stock" (an additional Group 24 and 17 gallons more fuel). That works out to adding an additional 186# to the boat, but the additional weight is very close to the center of the boat, i.e., closer to the center of floatation.

Had I left the batteries and fuel in the stern, I'm not sure if there is any amount of weight I could add to the bow to get the same results. If I had just moved the original weight out of the stern, I would have had a really zippy 16. But I wanted the extended cruising ability of an additional battery and more fuel. As such, I was basically forced to move batteries and fuel forward. And it worked out.
 
We just run with the tabs most to all the way down, and the motor tucked pretty low as well. In really heavy water, I've had to bring the tabs up to avoid having them get caught by stern seas. Bow steer is rare, but it can happen and I certainly would want a quick adjustment to make it go away. Very unpleasant and dangerous. We have a group 27 house and a group 24 starting battery in the area between the tanks. They sit just fine there. That's about the most stabile location on the entire boat.

When we bought the boat it was rigged with an anchor chain specifically for weight. Very annoying to handle and was too short. I replaced it with a long line (for our area - 150' is plenty) and a short chain.

Mike
 
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