Adding Ballast to stiffen Boat

Hi,
I purchased a 1986 Senator 35 Sundeck Trawler and we absolutely love everything about the boat except how lively she feels. When a sportfisherman goes by, the wake will rock the boat 20-30 degrees from side-to-side. Which is not only very uncomfortable, but down right dangerous at times.
I found an entry in the log book that in 2005 the PO had the cement and pig iron ballast removed and replaced with 20 Gallons of Chockfast Gray with Laminating Resin. I am sure the Chockfast and resin are not as heavy as the pig iron. The weight of Chockfast is 56lbs. per 5 gals. which means that 20 gallons only created 225 lbs. of ballast. I think this is why the boat is so lively. The PO is no longer available, so I contacted the company who did the work, but their files are gone and there is no record on exactly what was done and how they did it.
Does anyone have any experience with adding ballast to the keel to stiffen the boat?
My first thoughts, being an old sailor, is to add lead sausages to either side of the keel and then through bolt through the now resin filled keel. Creating a "bulb" keel similar to those on sailboats. If the sausages are tapered at the forward edges they might not create too much cavitation and that would keep the ballast as low as possible.
I am not sure how much weight to add, but I am thinking of about 500-1000 lbs. per side to give a total added ballast of 1000 to 2000 lbs.
I am concerned about if the boat would ride too low in the water and how it might handle.
I probably should consult with a naval architect for expert advice, but I thought I would throw to to the group for your thoughts.
Any other ideas?

Thanks,
Jeff Gardiner

That boat is probably a hard chine, semi displacement hull and those react to wakes with a sharper roll than a pure displacement hull that may roll farther but with a slower, easier motion.


Boats like this were built with ballast to trim the boat and not necessarily for stability. So I would consult with a naval architect to determine whether additional ballast will help.


David

Meanwhile, head into the wake and cut the throttle.

I think the best place for damping the rate of roll w ballast is under the deck far out by the cap rail. Or if there’s little flare near the chine.
Ballast in the keel or inside on top of the keel will be too close to CG on most trawlers.

jeffg said:

Hi,

I am not sure how much weight to add, but I am thinking of about 500-1000 lbs. per side to give a total added ballast of 1000 to 2000 lbs.
I am concerned about if the boat would ride too low in the water and how it might handle.
I probably should consult with a naval architect for expert advice, but I thought I would throw to to the group for your thoughts.
Any other ideas?

Thanks,
Jeff Gardiner

Click to expand...

Hi Jeff, The following post/threads are available to read and digest. I was not able to find my many post on the subject, however your inquiry mirrors my intitial inquiry to the forum a couple of years back. We are a 28 foot SD hull altho by hull design and formula we can not exceed hull speed of 7 knots so the title of SD is a streach, we are more full in the stern and react more towards FD in practice. Having said this, we had the same rolling effects you discribe, more total rolling than the 'Snap' effect a SD boat reflects. In the end we did the following. We added 1400, now 1500 lbs of 50# ingots along the engine stringers, and under the engine proper. We changed engines during the period adding 600# additional weight with the larger replacement engine. The effect is just totally outstanding!! You would not believe the stability of the boat in all quarters of sea action.
When it comes to finding lead ballast, read the thread below. You should be able to locate a junk metal yard. Junk lead when I was seeking, ran $1.20 (Seattle, WA.} I would suspect an additional charge to melt it down into ingot form. I was fortunate to find ingots already pored here in Ketchikan, which we agreed to add the cost of freight from Seattle to Ketchikan of $.20 cents per pound.
The last 100# ingots I added a barn yard gate handle to the two ingots. I located these in the aft cockpit area. When guest are on board and settled in I am able to adjust the trim by moving these two ingots to compensate.

Read 'Tad's' post within the offerings, he is the forum expert with sound advice.

Regards,
Al-Ketchikan

PS: We went from a 3 foot draft to 3.4 (sorry my error) draft following this ballast change.

http://www.trawlerforum.com/forums/s31/ballast-17766.html

http://www.trawlerforum.com/forums/s3/added-ballast-good-bad-24212.html

http://www.trawlerforum.com/forums/s32/$2-usd-per-pound-lead-36810.html

.

Don’t know how much naval architects charge nowadays, but I’d think it’s less than the cost of a ton of lead for some simple calcs.
I put a ton of lead in my hull, and moved it several times, the results being nil to negligible.
It would have been much less work to hire someone to tell me that!

Btw, I just stumbled onto your post, you might get much more response by posting under a more appropriate heading...

kapnd said:

Btw, I just stumbled onto your post, you might get much more response by posting under a more appropriate heading...

Click to expand...

Why?? The title couldn't be any more clear or direct.

I think the issue was he didn't post it in the "General Discussions" area.

Btw, Jeff I see you're from Needham. Where do you keep your boat? I'm in Marina Bay in Quincy.

The title of the forum that the OP posted in is “how to use the forum, site news, and account concerns”
One might note that there are several dozen forum titles, surely one could pick a heading that’s at least a little bit relevant to his query.
Just trying to help, I suppose the moderators will move it eventually.

Thread moved.

The boat is hard-chined with a fairly flat bottom, it really wants to follow the face of the wave (snap-roll) . It sounds like the boat has excellent low angle stability, so it will take considerable force to change the motion. Adding 2000 lbs of ballast probably won't do much, but it will do something. By adding the ballast down low you will increase stability, and thus the motion will get faster.


Rolling chocks, bilge keels, bat wings, or stabilizers of some sort will significantly change the motion (damp out rolling), but any of them is a big project.



I would be very reluctant to reduce high-angle stability by adding weight up high, but that would slow the motion. It will take about 1500 lbs to sink your boat 1". I would try putting the lead inside on top of the chockfast, see if it does anything noticeable. The lead needs to be secured so that it will never move, ever!

I am told, the greatest effect occurs when the ballast is located "high and wide" and secure it. Movable ballast will move at all the wrong times.

Tad, enlighten my ignorance, please, what is a chockfast?
Google shows it to be a bedding/damping compound, but your usage makes it sound like some part of a boat that I’ve never heard of.

enlighten my ignorance, please, what is a chockfast?

On larger boats where engine weights are many tons building engine mounts to hold it in alignment would take too long.

Instead the engine , tranny , shaft are jacked into place , a well built under each mount pad and Chockfast simply poured in.

When cured the engine is bolted down hard , done.

I have used the Orange on smaller items and it works Great!


Chockfast Gray | Chockfast

chockfast.com/products/two-component-epoxy-chocking.../chockfast-gray/

CHOCKFAST® Gray is a highly flowable, two-component, thin pour “chock” designed to maintain ... When used as a chocking compound for machinery, the CHOCKFAST® Gray provides ... Two-Componenct Epoxy Chocking Compounds.

Maybe your expecting too much out of a little boat? Better weather awareness and laydays may be the easiest cure.

Jeffg DALLIANCE I have the same boat 86 SENATOR SUNDECK i agree with the former head into the wake and reduce spead.

Jeff,

I couldn't tell you about the lead sausages, I'm the wrong kind of engineer.

But I do see a cheap way to test whether the added weight will make your boat sit too low in the water. Put 5 gal buckets of water on your decks to see. A gallon of water weighs 8.34 lb, so you would need 47 buckets to get about 2000 lb. Be sure to spread them out, and put them over hard points wherever possible so you don't overload any point on your deck. I wonder how many buckets you could scrounge, borrow from neighbors, rent, etc?

Worst case is buying 4 boxes of 12 buckets each from some place. Uline sells buckets for $4.60 or less apiece. That's about $225 if you have to every one of them.

probably cheaper to offer free beer to 10, 200 pound guys for an hour to come aboard.

Hi,
I am at the Metropolitan Yacht Club in Braitree on the Fore River just beyond the old shipyard.
Jeff

Interestingly I had chockfast put in certain places by my new stern tube 13 years ago. A feature of chalkfast that led to it’s use on Willy was the fact that it dosn’t shrink as it cures. So it didn’t break it’s bond to the hull, a box like shelf right under the starn tube and the tube. The “no shrink” feature is a wonderful feature of some structural applications. We’ve had no related problems.

Hi,
I don’t have an issue with the chockfast. As a matter of fact it is an excellent fill material and, as you said, it dose not shrink so it holds in place. My concern is that the weight of the chockfast is far less than concrete and pig iron. So, when they removed the cement and pig iron and filled the keel void with chockfast, they reduced the weight in the keel. I think is what is causing the “lively” behavior of the boat. My goal is to try to restore the weight lower on the keel to stiffen the boat.

Hi,


Some of the advice given in this thread reflects a certain confusion as to what your exact problem is, and I can't say I'm too sure of that myself. You say you want to stiffen the boat, yet you complain that she is too "lively", which is usually taken to mean that she reacts quickly to wave action. This in turn is usually due to a stiff gz curve and / or low moment of inertia.



To correct lively roll characteristics, bilge keels can work very well. What's your five degree roll period at rest?

psneeld said:

probably cheaper to offer free beer to 10, 200 pound guys for an hour to come aboard.

Click to expand...

And easier to move around too !!

Just a thought on this topic, maybe you can borrow or rent a bladder. Put it where you think you may want weight and pump it full of water. See how it reacts to the weight and then also drain it and move it fore or aft to find the sweet spot. No I don't have any experience with this or know if it would work, just throwing it out there.

Stabelize

Hi jeff
I have a 35ft steel displacement launch. I know how lively they can be to to point that my wife did not want to come aboard anymore. I took another route and installed passive stabelizer wings. Underway i have a roll reduction of 95% and at anchore about 50% with the roll stopping much faster. Even when takeing a beam wake of over 1m i still dont spill a drop of my coffee on the saloon table. Before the stabelizers she shook and rolled intolarably. Everything flying everywhere. Now she is a dream, i dropped only half a knot in speed for the luxary of a smooth ride. I have also discovered that most of the time i only need 1 wing down. 2 down are only needed on off shore trips in 2 to 3m seas. I designed and built the stabelizers myself at a cost of around $3000. Best money spent on my boat

Kiwi, what exactly is a stabilizer wing?

Hi
Its literally a fold down wing with a brace pole up againts the hull. Many comercial fishing trawlers use it here in NZ. I modled mine off a nieghbour in the boat yard with a few changes to suite my launch. Its basically a fold up steel wing on each side. Its princple works like a keel on a sailboat exept that they stick out the side generally at 45 degrees below horizontal hinged at the chine.

Google passive stabeliser wings ther is not much info out there but i never cruise without mine being deployed

The following comes from an article published by Bray Yacht Design
Generally, when people think of stability and ways to increase it they think of adding ballast.
Generally, this will help - but not in all cases. If ballast reduces the freeboard to the degree
that the deck edge enters the water at a much lower angle of heel, then the overall stability
is drastically reduced. Again, it is the relationship between the hull form and the overall center
of weight that tells the story. Removing top weight from as high up as possible will have a
greater effect than adding ballast low down.
Also, ballast will not do much to increase initial stability (stability at very low angles of
heel). It’s real forté is at higher angles of heel. Once the heel angle starts to reach or exceed 45 degrees ballast comes into its own. Although this may provide real peace of mind, it does little to improve a day to day comfort situation.
Source: http://www.brayyachtdesign.bc.ca/Stability.pdf

Here's a short article about different types of stabilization if anyone is interested:

https://www.marineinsight.com/naval-architecture/roll-stabilization-systems/

Tad Roberts said:

The boat is hard-chined with a fairly flat bottom, it really wants to follow the face of the wave (snap-roll) . It sounds like the boat has excellent low angle stability, so it will take considerable force to change the motion. Adding 2000 lbs of ballast probably won't do much, but it will do something. By adding the ballast down low you will increase stability, and thus the motion will get faster.


Rolling chocks, bilge keels, bat wings, or stabilizers of some sort will significantly change the motion (damp out rolling), but any of them is a big project.



I would be very reluctant to reduce high-angle stability by adding weight up high, but that would slow the motion. It will take about 1500 lbs to sink your boat 1". I would try putting the lead inside on top of the chockfast, see if it does anything noticeable. The lead needs to be secured so that it will never move, ever!

Click to expand...

How would you feel about sand bags being placed below deck? Do you think by moving them around, the motion could be better controlled, and then weight permanently installed in those areas?