SailNet Community banner
1 - 20 of 21 Posts

·
Registered
Joined
·
123 Posts
Discussion Starter · #1 ·
Greeting again everyone. I have a quick idea I wanted to pitch to the group. Our boat being a shoal draft Seaferer 34 has a reputation for being slightly tender (3'9" draft with C/B up, 4800 LB lead ballast). I have been doing some reading into this, the motion comfort ratio, and general sailboat design and am wondering if perhaps adding water tankage to the bilge would be a good solution to aid our vessels sailing characteristics and stability. I know that heeling effectively adds waterline length and aids in our speed but too much can also make for an uncomfortable passage and lead to premature reefing. Interestingly, in original literature for our boat the boat was outfitted with tankage in the bilge, which leads me to believe that perhaps she was engineered to have this added weight down low. Of course ours, being originally sold as a bare hull to the original owner, does not have this feature. So, aside from configuring our sail plan with added reef points and getting as much of our general stores down low, do you all see a large benefit from adding the water stores as well? I believe I can fit two flexible bladders on either side of the centerboard trunk (see our construction pictures) without taking anything away from the bilges deep sump where our bilge pumps are located. Projected weight added being between 500-650 LBS. Assume I will make those bladders stable and protected from rupturing in all conditions. I really love our boat and want to make her as seaworthy and capable as possible as both a coastal cruiser and open water vessel, although I do not think she is necessarily ever going to be a "safe" blue water boat. Thanks for the input. I would like to hear all angles on this if you all have the time.
 

·
Registered
Joined
·
969 Posts
Our 1961 Alden Challenger was designed with built in fuel tankage well below the sole and around the centerboard trunk(like what you're planning).

The 80 gallon tank is built into the fiberglass hull and has 4 large 1/4" steel plates to cap the tank area. A few boats had problems with leaking keel bolts. Some removed the tanks(they were so large because the boats came with Graymarine gasoline engines).

Even though the Challengers have bolted on long lead keels, Alden(when they were still designing boats) recommended added low ballast in converting the tanks. The steel plates were part of the reason but the fuel down low may have been considered in the boats stability(centerboarders need special thought to stability forces).

As well as the 80 gallon diesel, our boat has 2-40 gallon water tanks at sole height/below the waterline. A lot of weight down low that is helpful for stability.

In the end, even though any weight is detrimental to light air sailing performance, you need water! :) And that area is a great spot for fluid storage. Flexible tanks that fit nicely sound like a good idea to me.
 

·
Registered
Joined
·
678 Posts
I can't remember the numbers but I think they say every pound you take out of the rig adds 10 to the ballast so to speck. New rope rigging might be a easy way to start this project, as would well shaped sails. Bilge water tanks are always good but easier said than done.
 

·
Registered
Joined
·
123 Posts
Discussion Starter · #6 · (Edited)
Unfortunately, the rig is all but done, and all new, luckily we did not go up any wire sizes other than on the forestay. That said, we lack things like a radome or mast steps. Dyneema was a consideration but I just couldn't subscribe to it fully, I trust my stainless over all else. The reason I suggested the water tankage is mainly because we need it. We have a watermaker but I still would like to have surplus water for things like our shower and dishes, potable water will be separate from the bilge system if implemented.

I guess what I would really like to know is given our shallow draft are we really gaining any mechanical advantage over the force of the rig in keeping the boat righted by just adding weight without the leverage? When I built out centerboard I put as much lead in it as possible but that was really only to ensure it does not sweep up at speed. I suppose I could consult a naval architect but I wanted to ask here first. Has anyone experienced a cause and effect situation where they effected their boats heeling and to weather performance by adding weight to the bilge/ballast?
 

·
One of None
Hunter 34
Joined
·
9,026 Posts
I'm Guessing you have not really used the boat or even sailed it yet. Why not try to stop over thinking all this until you get her "out there" ?

What you were "told" doesn't mean squat, fear of heeling is real and imagined and will subside as you get used to the boat.
 

·
Registered
Joined
·
123 Posts
Discussion Starter · #8 ·
I don't consider this overthinking anything. You are correct in your assumption that we have not used the boat. we have been living aboard another vessel for the last few months and I can assure you I would not want to cut into a freshly laid sole to retrofit water tanks into my bilge while underway or living aboad. Supporting said tanks and running plumbing is exponentially easier at the current stage of our project. Hence my planning ahead on this particular topic. Sometimes it's nice to learn from other people's experiences instead of repeating the same old mistakes. Also, this has nothing to with fear; it has everything to do with vessel stability, functionality, and safety. Thanks for the input
 

·
Registered
Joined
·
846 Posts
Water tanks are for you water needs. They might add some weight below your water line if they are full, but fresh water is for consuming. You can never keep them full when you really need them. Adding some more weight to your keel or to your bilge is a better solution. The best solution is to buy a boat with required specs.
 

·
Registered
Joined
·
7,865 Posts
I agree water tanks aren't ballast just weight that is sometimes there.

I your boat matches the numbers here SEAFARER 34 CB sailboat specifications and details on sailboatdata.com I would not be concerned with stability. 34 ft with a 10ft beam and a 39% ballast ratio denotes stability to me. As far as qualified for offshore use I would say it is as long as items such as rigging and cabin closures are sufficient. Centerboard boats have an advantage in the rough stuff in any case as with the board up they are a lot less likely to trip over the keel in large seas the way a deep keel boat can.

Finisterre has similar numbers and she crossed a bit of open water in her time.
Sparkman & Stephens: Design 1054 - Finisterre
 

·
Registered
Joined
·
123 Posts
Discussion Starter · #11 ·
Mitiepo THANK YOU for your constructive response based on your experience in a similar vessel. Also thanks to other members who were patient and good enough to offer their advice based on the questions I am looking for answers on. I'm tempted to quit while I'm ahead on this one, ultimately since we need water and weight low down in the vessel I will pursue this idea come spring time. I spent a few hours last night researching this again and believe there is much to gained in this modification. If anyone else with knowledge on the subject wants to suggest stability enhancing mods for a shoal draft vessel I would welcome your input.
 

·
Registered
Joined
·
969 Posts
Mitiepo THANK YOU for your constructive response based on your experience in a similar vessel. Also thanks to other members who were patient and good enough to offer their advice based on the questions I am looking for answers on. I'm tempted to quit while I'm ahead on this one, ultimately since we need water and weight low down in the vessel I will pursue this idea come spring time. I spent a few hours last night researching this again and believe there is much to gained in this modification. If anyone else with knowledge on the subject wants to suggest stability enhancing mods for a shoal draft vessel I would welcome your input.
Another fun source is SailCalc. Compare your Seafarer to other similar boats you know. I think you'll find it's stability(according to this tool) is not something to worry much about.

Boats like ours with centerboards in long keels carry their ballast quite low in moderately beamy hulls. Your boat has a lower stability number(higher ultimate stability) than mine but they are both quite low numbers compared to most boats these days.

The lower you can locate your tankage(live weight), the better for stability.

Sail Calculator Pro v3.54 - 2800+ boats
 

·
Chastened
Joined
·
4,860 Posts
It's not simply a matter of "how much" ballast you're carrying, it's also "where".
I feel that fresh water tanks in the bilge will not provide the righting moment you desire, for the amount of weight you'd have to add.

The CB version already has 600# more ballast than the fin keel version, in the centerboard stub to aid in righting. Keep piling on the weight and the boat's light air performance is going to suffer (and it ain't really good in the first place)

You might investigate if it's possible to make a heavier centerboard. 250# down lower, has the same effect as 600# higher up. In the meantime, reef early and often.
 

·
Registered
Joined
·
123 Posts
Discussion Starter · #14 ·
Tom thanks very much for the calculator link, and what a gorgeous boat that Alden is. Bubblehead you make a very good point on where the weight is placed, leverage makes all the difference. I considered a steel CB but did not want to worry about the upkeep and corrosion issues. The current board is about 100# fiberglass and lead so that might count for something. You also make a good point on the trade off between adding weight and losing speed which is also a major consideration as we plan on sailing primarily regardless of wind or direction headed. I'll weigh our options carefully and thank you guys for the suggestions and excellent points.
 

·
Barquito
Joined
·
3,887 Posts
It seems to me that if you moved the water tanks from a position that is higher, to a position that is lower, you would be increasing the righting moment (when there is something in the tank). How much? I don't know. How difficult would it be? I don't know. I would guess that on my boat it would, also, reduce hobby-horsing moving the tank from the forepeak to the bilge
 

·
One of None
Hunter 34
Joined
·
9,026 Posts
Seems pretty seaworthy to my non expert eyes!

this person's blog has lots of photos! http://boat.bilyk.name/index.html



Install your tanks! You have my permission! :D Just please get her done and go sail her before you loose interest! What's it been now? almost 3 years? :eek:
 

·
Super Moderator
Joined
·
4,123 Posts
Barquito, I just plugged your vessel and mine ( Sabre 34 mkI ) into the calculator that Tom linked. Your motion comfort number is much better than mine and at 37.02 would seem quite good if that's a concern. Your SAD is 14 compared to 16 for my Sabre.
I really don't believe ballast should be a concern for you. You want to be able to sail in light air too.

I tend to take a reef " a little" early to reduce weather helm with little, if any, loss in SOG. So, I don't really consider that an issue.

If you want or need water for your cruising goals that's fine. But I don't know if you need to intentionally add more weight to alter the design.
 

·
Registered
Joined
·
7,865 Posts
In light air the enemy is wetted surface vs sail area. There are many very heavy boats that do very well in light air, and as heavy boat is helped by momentum which a lighter boat may lack.

But as I posted I wouldn't add extra ballast to the op's boat. If extra water tankage is desired great, but that is a different issue and cannot be counted as ballast.

My post (#10) did not refer to a boat I have experience with - I wish I had. Finisterre was a milestone design that won the Bermuda race 3 times under the ownership of Carleton Mitchell. She was a great cruiser as well as racer.

In Europe there are many cruising boats with centerboard configurations. Many do not have a long keel for ballast which is in the hull bottom, higher than your ballast. They have proven themselves very capable offshore. Garcia is one.
 

·
Barquito
Joined
·
3,887 Posts
Barquito, I just plugged your vessel and mine ( Sabre 34 mkI ) into the calculator that Tom linked. Your motion comfort number is much better than mine and at 37.02 would seem quite good if that's a concern. Your SAD is 14 compared to 16 for my Sabre.
I really don't believe ballast should be a concern for you. You want to be able to sail in light air too.

I tend to take a reef " a little" early to reduce weather helm with little, if any, loss in SOG. So, I don't really consider that an issue.

If you want or need water for your cruising goals that's fine. But I don't know if you need to intentionally add more weight to alter the design.
I think a may go with wine-bottle-ballast in the bilge. I wouldn't want to add weight anywhere unless it was needed (wine is needed).
 
1 - 20 of 21 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top