Ballest for a Marben

[Al]

Northern Spy and other posters on this discussion, Here are photos of sister boat. The interior is similar, but different as most boat of the same are, This boat has 200 gallon fuel tank and a bigger H2O capacity than our 74 gallon fuel and 48 gallon H20.


http://www.yachtworld.com/core/listi...=1007&url=&imc

Are you guys able to view this site? It didn't turn blue.


A.M.Johnson-Ketchikan

[Northern Spy]

Yup that's the one. It's back up now. The dead aft shot lead me astray. Selective memory had me remembering Spy's bottom as it actually looks like similar deadrise. When I see the side pics, she's definitely full displacement.

I look forward to your test results. When I get home I'll take a look at my GM calculations. Mine was pretty snappy when relaunched and empty after repowering. After a few years of re provisioning (placing useless crap back in the lockers) her roll is more gentle.

I had also thought about putting some lead in the bilge (keel box) but I think she'd just get snappy again with the hard chines on my boat.

I used to have a few 2' chunks of railroad track epoxied on the stbd side for list correction. Took them out when I moved some tanks around. Wish I kept them around to play with now.

[rwidman]

Originally Posted by Aquabelle

...and then make any additional permanent ballast useful by providing it as an extra water tank (custom made to fit the size/shape available) rather than just as inert zinc or lead.

1) Water weighs the same as water. More than air, but not nearly as much as sand, zinc, or lead.

2) If the water is in a tank and intended for use (potable, washdown, etc.), then the ballast effect will vary with the amount left in the tank.

If it is determined somehow that the boat would benefit from added weight near the keel, lead would be the best choice. Zinc (because the OP can get it free) would be an OK choice. Or sandbags could be left in place.

[Al]

Maybe this episode will give you a clear picture. But before I start, think about this. the Marben you see in the photos has total 200 gallon fuel tank(s)vs our 74 gallon. that constitutes approximately 1500 # when full and that sits in the lower quarter of the boat, along with 30 gallons of H2o more than I carry or 240#. That is a huge difference in weight between the two boats. It stands to reason then that placing 3-350# of weight may affect but not to the degree it must affect this sister boat. I am going to guess that he is experiences less movement in similar sea conditions as our boat. Maybe not, just seems sensible.
Now- with the seating set up being a sofa to the port, and the passenger or first mate seat to the port, when you have a party of four, one, the male guest, usually the heavier situated, the boat will travel with about a 3 degree list to port, even with the wife sitting centerboard (little thing ) Then if I, the Master and Commander, choose to move about, the list can easly move to 5-6 degrees till I offset once again. I have found that if I shift the 6hp outboard from Port to Starboard along with the fuel supply, the list is reduced to almost nil (not including my moving about). So I have installed a outboard bracket on the railing on both sides of the boat, shifting the outboard as required to achieve the current required balance.
Again all of this conversation rotates around the issue of comfort, not safety.
This boat is not going away.

Regards,
A.M.Johnson
When I was a boy I was told that anybody could become President; I'm beginning to believe it.
~Clarence Darrow

[RickB]

Originally Posted by Northern Spy

When I get home I'll take a look at my GM calculations. Mine was pretty snappy when relaunched and empty after repowering. After a few years of re provisioning (placing useless crap back in the lockers) her roll is more gentle.

That is 180 degrees opposite of intact stability. A "too stable" vessel has a large GM and will roll quickly. Adding weight will lower G and unless there is a large change in draft, the GM will only increase and the boat will roll (snap)even faster.

I had also thought about putting some lead in the bilge (keel box) but I think she'd just get snappy again with the hard chines on my boat.

That is the way it works. Adding weight down low increases static stability but increases roll rate. If you want a slower roll, take weight out of the bilges or add it higher.

[Al]

Rick B- Well, in our case the boat is not 'Stiff', it rolls. A round bottom boat will roll, wood or plastic. Enjoy your comment as it relates to CG. Rolling was not the root cause of our original post yet is somewhat related.
I suspect that the designer, Ed Monk, a renown marine designer, configured the boat as close to CG rules as possible. As nothing of any magnitude, such as weight at a higher location on board, it could be as LL posted, a case of 2/1 length/beam results in a 'hobby horse' 'barrel rolling' trawler- resulting in recognizing that a pocket trawler is limited.
Ultimately, there is nothing so troubling that will result in not enjoying messing around in the boat!
Regards,
A.M.Johnson-ketchikan

[RickB]

Originally Posted by Al

I suspect that the designer, Ed Monk, a renown marine designer, configured the boat as close to CG rules as possible.

There are no CG rules for stability for uninspected recreational boats under 65 feet in length. There are capacity rules for boats under 20 feet but the CG could care less if a boat is stable or not unless it is an inspected vessel or is not in compliance with the power and loading limits of very small boats.

...it could be as LL posted, a case of 2/1 length/beam results in a 'hobby horse' 'barrel rolling' trawler ...

A 2:1 boat has higher initial stability than a long and lean vessel of the same draft.

The ratio itself isn't the problem, it is more related to the length of the waves the boat operates in. A short boat is closer to the length of the wave and of course it will pitch more as it won't bridge several waves ... put a 800 foot long containership in a long Pacific swell and it will pitch like a horse as well. Ever see a film of a destroyer in a storm? Those ships are around 10 or 12:1.

[markpierce]

Originally Posted by Boatgm

I agree with doing some testing, both roll period and incline.

Here, preparing for some kind of test.

[Al]

CG= Center of Gravity,

AMJ

[Al]

Home for the day, re-read Rick B post and want to make note of agreeing with the description of beam length offering.

In past local discussions of water conditions and our local fleet. The waters of S.E Alaska inside waters, offer a lot of 2 foot seas and the length of the troth is best crested with a boat in the 38-48 foot length as the boat will span two waves. Not so with our 27 foot boat, Rick is correct, we waller, rock and roll with each following swell. So Rick is correct as it applies to our local waters. Perhaps that explains that our commercial West Coast trollers U.S. and Canada, fall into that length class.
anyway, just wanted to make note and agree.
A.M.Johnson-Ketchikan

[Northern Spy]

Originally Posted by Northern Spy

When I get home I'll take a look at my GM calculations. Mine was pretty snappy when relaunched and empty after repowering. After a few years of re provisioning (placing useless crap back in the lockers) her roll is more gentle.

Originally Posted by RickB

That is 180 degrees opposite of intact stability. A "too stable" vessel has a large GM and will roll quickly. Adding weight will lower G and unless there is a large change in draft, the GM will only increase and the boat will roll (snap)even faster.

Originally Posted by Northern Spy

I had also thought about putting some lead in the bilge (keel box) but I think she'd just get snappy again with the hard chines on my boat.

Originally Posted by RickB

That is the way it works. Adding weight down low increases static stability but increases roll rate. If you want a slower roll, take weight out of the bilges or add it higher.

You're absolutely right, it was more likely the removal of railroad track down low and adding the weight back up high (kayaks on pilothouse roof, restepping the mast, building an overhead console) rather than the minor increase in draft that raised G, lowered GM, and lessened the righting arm.

[Al]

Mark, I see that you are online. Could you respond to me if the photo I am adding to the text comes through? Thanks, I have no sense on how to transfer photos from my phone to add as an attachment. I read the 'Newbie' column but I am just not up to speed and all of my Granddaughters are absent. Thanks, AMJ

I am posting this to reflect the size of our 27' Marben along side a 26 ' Tolly. gives a prespective in the recent discussions. One can see the difference. Again, we have a 3'6" draft.
AMJ

https://mail.google.com/mail/?hl=en&...a0095932e186cd

[Al]

Nope, I can see its not going to work. Thanks, AMJ

[Rambler]

Originally Posted by Al

I have no sense on how to transfer photos from my phone to add as an attachment. I read the 'Newbie' column but I am just not up to speed and all of my Granddaughters are absent. Thanks, AMJ

I see that you are as technological competent as I am. Might we be related?

I suspect this site help can't tell you how to get pics off your phone. That'd be on the phone help site though. Probably have to copy it or send it to a computer then take it from there and post it to this site.

[Nomad Willy]

Now that I've seen a pic of the Boat in question I'd recommend some ballast but a NA will probably be the only one that can tell you how much and where. I've seen Ballest recommended up under the decks at the gunwales to dampen roll on a light boat. We have 4,000lbs ballast in Willy as it came from Willard so have little idea what she would act like w/o it. Many boats have newer and much lighter engines than original and that could or should be taken into consideration as well.

I haven't read all the posts but I'd recommend finding out all that could be discovered about ballast as original equipment or as specified by the designer.

Beyond that one could/should spend some time on BoatDesign.net.

[Al]

Hi Eric, (It is Eric as I recall). See you are or were back in Thorne Bay with your advertisement for home sale. I trust you have dotted all the i's and crossed your t's.
Having K-Town as my life long home base, I have seen so many throw up their hands, or for any number of reasons, sell their home in South East Alaska and then, within two or three years, back swearing never to move South again as the (You fill in the blank) traffic, taxes,schools,crime, weather. all become factors that have them back into our part of the world.
Anyway, I know your model of Willard. I would think your draft is equal to our 3'6". Your center of Gravity will be lower just by the nature of deck levels in the two boats.
Our craft comes with 1500 # poured into the keel at construction. You indicate you have not read all the post. I believe you will agree, the sister boat to ours carries 200 gallons of fuel vs. our 75 gallons. Water on theirs is 85 gallon and on ours 48 gallons. Right there is a huge difference in full tank status. When you look at that difference in light of your indicating a 4000# ballast in the Willard, It would seem there is room for adding a couple hundred pounds in the bilge area.
We shall see, and will give a report.
Take care- Good luck on the home sale, It appears very well built and attractive to the eye.
See you in a couple of years (Maybe 8-)
A.M.Johnson-Ketchikan

[Al]

Greetings, Test,Test, attempting to post a photo. Seems a whole lot of letters and numbers!! The purpose is to reflect the height of our 27 foot Marben alongside a 28 foot Glasply and a 26 foot Tollycraft. in relationship to the ballast conversation.

Cheers- A.M.Johnson

https://mail-attachment.googleuserco...14140486964215

[Al]

Nope, o well, best to close the thread- Thanks to all
A.m.Johnson