The C-Brats Forum Index
HomeForumsMy TopicsCalendarEvent SignupsMemberlistOur C-DorysThe Brat MapPhotos

Weight relationship fore to aft
Goto page 1, 2  Next
 
Post new topic   Reply to topic    The C-Brats Forum Index -> General Technical Discussions
View previous topic :: View next topic  
Author Message
AKMel



Joined: 13 Jan 2017
Posts: 47
City/Region: Gustavus
State or Province: AK
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: C-esta
PostPosted: Thu Mar 02, 2017 8:11 pm    Post subject: Weight relationship fore to aft Reply with quote

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
Back to top
View user's profile Send private message Send e-mail
ssobol



Joined: 27 Oct 2012
Posts: 3361
City/Region: SW Michigan
State or Province: MI
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: SoBELLE
Photos: SoBelle
PostPosted: Thu Mar 02, 2017 8:43 pm    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
Ferg



Joined: 18 Jun 2015
Posts: 187
City/Region: Oak Island
State or Province: NC
C-Dory Year: 2008
C-Dory Model: 25 Cruiser
Vessel Name: Here & Now
Photos: Here & Now
PostPosted: Thu Mar 02, 2017 8:46 pm    Post subject: Reply with quote

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
Back to top
View user's profile Send private message Send e-mail
South of Heaven



Joined: 15 Aug 2015
Posts: 1459
City/Region: Sharon
State or Province: MA
Photos: Blue Water
PostPosted: Thu Mar 02, 2017 11:33 pm    Post subject: Reply with quote

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!

_________________
<><><> Jason <><><>

2005 Silverton 35 Motoryacht (Twin 385 Crusaders) (SOLD 6/20)

2000 Camano 31 Troll (Volvo TAMD41p) (SOLD 2/19)

2007 C Dory 25' Cruiser (200 hp Suzuki, sold 7/17)

2003 C Dory 19' Angler (80 hp Yamaha, sold 7/16)

1995 C Dory 16' Angler (40 hp Yamaha, sold 2/16)
Back to top
View user's profile Send private message Send e-mail
island andy



Joined: 28 Jan 2016
Posts: 38
City/Region: rochester hills
State or Province: MI
C-Dory Year: 2007
C-Dory Model: 22 Cruiser
PostPosted: Fri Mar 03, 2017 8:40 am    Post subject: Reply with quote

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

_________________
andrew g wilson jr
Back to top
View user's profile Send private message Send e-mail
BTDT



Joined: 07 Jan 2011
Posts: 322
City/Region: Grand Lake Oklahoma
State or Province: OK
C-Dory Year: 2007
C-Dory Model: 255 Tomcat
Vessel Name: C- Lark Wine Down
Photos: C-Lark
PostPosted: Fri Mar 03, 2017 8:55 am    Post subject: Reply with quote

South of Heaven wrote:
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.


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

_________________
John & Vicki Clark
C-Lark Wine Down
Tomcat 255
Back to top
View user's profile Send private message
ssobol



Joined: 27 Oct 2012
Posts: 3361
City/Region: SW Michigan
State or Province: MI
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: SoBELLE
Photos: SoBelle
PostPosted: Fri Mar 03, 2017 9:42 am    Post subject: Reply with quote

island andy wrote:
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


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.
Back to top
View user's profile Send private message
SEA3PO



Joined: 02 Nov 2003
Posts: 1835
City/Region: Chester
State or Province: CA
C-Dory Year: 2003
C-Dory Model: 22 Cruiser
Vessel Name: SEA3PO
Photos: SEA3PO
PostPosted: Fri Mar 03, 2017 10:41 am    Post subject: Reply with quote

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
Back to top
View user's profile Send private message Send e-mail
AKMel



Joined: 13 Jan 2017
Posts: 47
City/Region: Gustavus
State or Province: AK
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: C-esta
PostPosted: Fri Mar 03, 2017 11:26 am    Post subject: Reply with quote

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


Last edited by AKMel on Fri Mar 03, 2017 11:31 am; edited 1 time in total
Back to top
View user's profile Send private message Send e-mail
Hunkydory



Joined: 28 Mar 2005
Posts: 2652
City/Region: Cokeville, Wyoming
State or Province: WY
C-Dory Year: 2000
C-Dory Model: 22 Cruiser
Vessel Name: Hunkydory
Photos: Hunkydory-Jay-and-Jolee
PostPosted: Fri Mar 03, 2017 11:30 am    Post subject: Reply with quote

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

_________________
Jay and Jolee 2000 22 CD cruiser Hunkydory
I will not waste my days in trying to prolong them------Jack London
https://share.delorme.com/JuliusByers
Back to top
View user's profile Send private message Send e-mail
AKMel



Joined: 13 Jan 2017
Posts: 47
City/Region: Gustavus
State or Province: AK
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: C-esta
PostPosted: Fri Mar 03, 2017 11:34 am    Post subject: Reply with quote

Hunkydory wrote:
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


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.
Back to top
View user's profile Send private message Send e-mail
SEA3PO



Joined: 02 Nov 2003
Posts: 1835
City/Region: Chester
State or Province: CA
C-Dory Year: 2003
C-Dory Model: 22 Cruiser
Vessel Name: SEA3PO
Photos: SEA3PO
PostPosted: Fri Mar 03, 2017 1:18 pm    Post subject: Reply with quote

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


Last edited by SEA3PO on Fri Mar 03, 2017 1:20 pm; edited 1 time in total
Back to top
View user's profile Send private message Send e-mail
hardee



Joined: 30 Oct 2006
Posts: 12632
City/Region: Sequim
State or Province: WA
C-Dory Year: 2005
C-Dory Model: 22 Cruiser
Vessel Name: Sleepy-C
Photos: SleepyC
PostPosted: Fri Mar 03, 2017 1:18 pm    Post subject: Reply with quote

AKMel wrote:
Hunkydory wrote:
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


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 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


_________________
Though in our sleep we are not conscious of our activity or surroundings, we should not, in our wakefulness, be unconscious of our sleep.
Back to top
View user's profile Send private message
SEA3PO



Joined: 02 Nov 2003
Posts: 1835
City/Region: Chester
State or Province: CA
C-Dory Year: 2003
C-Dory Model: 22 Cruiser
Vessel Name: SEA3PO
Photos: SEA3PO
PostPosted: Fri Mar 03, 2017 1:24 pm    Post subject: Reply with quote

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
Back to top
View user's profile Send private message Send e-mail
AKMel



Joined: 13 Jan 2017
Posts: 47
City/Region: Gustavus
State or Province: AK
C-Dory Year: 2008
C-Dory Model: 22 Cruiser
Vessel Name: C-esta
PostPosted: Fri Mar 03, 2017 3:15 pm    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic    The C-Brats Forum Index -> General Technical Discussions All times are GMT - 5 Hours
Goto page 1, 2  Next
Page 1 of 2

 
     Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum



Page generation time: 0.1068s (PHP: 79% - SQL: 21%) - SQL queries: 34 - GZIP disabled - Debug on