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Old 20-04-2016, 17:28   #1
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Hull designs .... questions

Hey i am new here . Have dreamed of sailing for a long long time. Goals are after i get enough experience and knowledge to do some ocean crossings and live a board . I have done a bit of research and i am sure there are threads addressing what i am asking . I think after reading some i would like to either go aluminum or steel probably leaning towards steel . Now i just want to know what would be the best hull design to look into, with the least 'thru hull' holes ? Also wanted to get some more reaction from something i read about the Break even boat size for steel boats when compared to the speed of a fiberglass boat?
Well i hope i don't sound to green here and draw criticism for my lack of knowledge . Have a great day and thanks for your replies.
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Old 20-04-2016, 17:58   #2
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Re: Hull designs .... questions

Well, welcome here. Don't worry, we've all been green before. So you are settling on steel? (I wonder if it was because you saw the movie "All is Lost?") I am not sure about the "break even" thing you are talking about, perhaps others know. I think there are some folks here with steel hull Roberts boats and others that will chime in. If you put "steel hull" in your thread title that might help. When you talk of the fewest through-hulls I am guessing you are thinking of designs that are designed to take a hit and keep on ticking, like those with through-hulls only in the mid section with bulkheads separating the bow and aft sections...? I suppose you could get by with only one for the engine water intake and leave the rest for buckets to be dumped overboard. As far as best hull design, that depends on you preferences for cruising: full keel or fin keel, skeg, spade or attached rudder, beamy or narrow... each has its assets and liabilities. Personally I'd go with a molded in fin keel and skeg hung rudder, and more on the narrower side, but I am from the old school...
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Old 20-04-2016, 18:19   #3
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pirate Re: Hull designs .... questions

My understanding is under 40 ft does not allow sufficient sail area to move the boat at hull speed.. to heavy.
I think a big 45ft Ovni style in steel would be a great boat.. I like chines..
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Old 20-04-2016, 18:49   #4
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Re: Hull designs .... questions

For offshore salt water sailing, I think I would strongly consider fibre glass, as both steel and aluminum have a tendency to corrode.

If you're doing a lot of coastal stuff, steel can be nice though, it's great for banging off reefs and rocks and whatever else it needs to bang off.

There are quality aluminum yachts, but they tend to be very expensive, and I have been more than a little uncomfortable on aluminum boats from time to time, they can be very hard riding in my opinion.


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Old 20-04-2016, 18:56   #5
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Re: Hull designs .... questions

Having looked at far too many boats across the web, i'm surprised the Amel cockpit style hasn't become popular. Instead a lot of two wheel designs with not so great protection. Ok if your racing, perhaps. Or centered pedestal and big wheel with with electronics on brackets or in the hull 5 feet away or stoop to see..
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Old 20-04-2016, 19:25   #6
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Re: Hull designs .... questions

Quote:
Originally Posted by PelagicSam View Post
Now i just want to know what would be the best hull design to look into, with the least 'thru hull' holes ?
That's a good goal.



It all depends on what systems you want.

The simpler the systems, the fewer the thru-hulls.

For instance, a typical plumbing set-up might have a sink with salt water intake and drainage; and a marine head with salt water intake and drainage. That's 4 below the waterline thru-hulls right there. These could easily be eliminated by replacing the marine head with a composting head, and replacing the normal sink with a dry sink (filled and emptied topsides, no plumbing).

You can have a 30' boat with 10 thru-hulls or a 50' boat with none. Consider the balance between convenience (additional systems) and risk (additional holes in the boat). It's all up to you.

Good luck on your journey!
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Old 20-04-2016, 20:03   #7
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Re: Hull designs .... questions

Why the concerns about thru hulls? Installed correctly & maintained properly,they are no more dangerous than other boat systems.

www.marinehowto.com

Cheers/ Len
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Old 20-04-2016, 20:57   #8
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Re: Hull designs .... questions

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Originally Posted by deblen View Post
Why the concerns about thru hulls? Installed correctly & maintained properly,they are no more dangerous than other boat systems.

www.marinehowto.com

Cheers/ Len
Failed/Open thru-hulls are the #2 cause of sinking while underway.

Quote:
(Boats That Sank While Underway)

Waves Over The Gunwales 30%

Leaks At Through-hulls/Hoses 18%


Leaks At Raw Water Cooling Systems/Exhaust 12%

Drain Plug Missing 12%

Navigational Error (Grounding) 10%

Boat Construction (Structural Failure) 6%

Leaks At Outdrive Boots 4%

Struck Submerged Object 4%

Other 4%
...and #1 cause of sinking at the dock/anchored.

Quote:
( Boats That Sank At The Dock)

Failure Of Through-hull Fittings Below The Waterline 50%

Rain and Snow (All Involved Self- bailing cockpits!) 32%

Failure of Through-hull Fittings Above The Waterline 9%

Improper Mooring Arrangements 8%

(Loss to Hurricanes Not Included)

Other 4%
...which means #1 cause overall, by far, since most sinkings happen at the dock/anchored.

http://www.boatus.com/procaptains/pd...TPAGEAug09.pdf

http://www.boatus.org/guide/boat_7.html
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Old 20-04-2016, 22:27   #9
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Re: Hull designs .... questions

P.S. Just for fun, a 2" hole (say from a failed black water outlet thru-hull) 2' below WL will allow ingress of over 6500 gallons per hour, which is several times more than the electric bilge pumps on most boats can handle. 6500 gallons of water weighs over 50,000lbs.
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Old 20-04-2016, 22:49   #10
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Re: Hull designs .... questions

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Originally Posted by Don C L View Post
So you are settling on steel? (I wonder if it was because you saw the movie "All is Lost?") I am not sure about the "break even" thing you are talking about, perhaps others know.
I don't know the technical details, but what he's talking about is that steel's strength to weight ratio is such (and the ratio of a boat's LOA to the weight of steel required to build it is such), that steel boats become more efficient (weight wise) as they get larger. This is why most sailboats are glass, and not a single oil tanker ever built is glass. In other words, there is a point (LOA-wise) at which steel becomes more efficient than glass, and below which it is less efficient, depending on a bunch of other variables in how it was constructed.

Some people will say that steel boats are impracticable (slow) until they get into the high 30s but there are in fact many successful steel designs down to 30' and below.

Apart from the obvious (strength), steel has a lot of advantages in terms of cost, ease of repair, and - yes - even ease of maintenance: IF the original coating is done properly, and IF the owner does proper routine maintenance. The horror stories of steel are from badly built boats or boats whose owners let things slide for far too long, allowing a small problem to become a big problem. If done well, steel can take less work to maintain than glass (e.g. no potted fittings will EVER leak).

I spent a ridiculous amount time/effort researching steel v glass, and I ultimately decided on steel.

OP, I would encourage you to keep looking further into steel.

It may or may not be best for your needs, but it's a most viable hull material in general.
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Old 20-04-2016, 23:23   #11
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Re: Hull designs .... questions

One good resource is the Metal Boat Society. Plus, there's a LOT of info; on, & via Dudley Dix's website. He's a (genius), who's done very, very well, designing in All materials.
And also, this book is excellent too (while a bit dated on cost #s, which are easy to convert) http://www.amazon.com/Steel-Away-Gui...rds=steel+away

It's not overly technical, but it covers 98% of what goes into a boat, including the specifics of where the $ goes. Into each & every system, plus the cost of the; hull, rigging, sails, electrical, & electronics, etc.
And it helps one to decide if a steel boat makes sense for them. Including covering 90-Something% of the questions which you posed.

My advce on choosing a boat, is to make up an itemized checklist, by system type, of what you want in a boat. And then prioritize it, & use it to compare perspective boats to.
You know; SADR, Ventillation, stowage capacity, etc., etc.

Plus, if you're serious about buying soon. Then put it all into a spread sheet, so that comparing boats (& what it'll honestly cost in order to get them cruise ready) will be a snap.

Also, the website www.Mahina.com is a great one too. As the owners teach sailing, & expeditioning, as well as professionally working with folks to help to put them into the right boats for their needs. And they have some good questionaires on the subject, plus some great boat recommendations as well.
A couple of others, which make you ask yourself some of the "hard" questions, which will ultimately lead you to a good boat, if truthfully answered are;
http://www.multihulldesigns.com/custom.htm
http://www.multihulldesigns.com/customprocess.htm

PS: This thread is a good one to read on choosing boats What's the best boat you've ever owned?
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Old 20-04-2016, 23:55   #12
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Re: Hull designs .... questions

Sadly, the metal society forum is all screwed up.

It was down for a while, now I think they're trying to migrate it to a new location.

Anyway, I second that as a great resource, if you can access it.
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Old 21-04-2016, 03:34   #13
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Re: Hull designs .... questions

Quote:
Originally Posted by KISS View Post
Failed/Open thru-hulls are the #2 cause of sinking while underway.

...and #1 cause of sinking at the dock/anchored.

...which means #1 cause overall, by far, since most sinkings happen at the dock/anchored.

http://www.boatus.com/procaptains/pd...TPAGEAug09.pdf

Boat US - Online Boating Safety Study Guide
Absolutely right.

We have to manage different risks -- sometimes small risks of very bad things happening. Sinking is one, gas explosions another good example.

Many people don't really understand how to think about such risks. They are relatively small risks, so often the approach is just not to think about it and convince yourself that "it can't happen to me".


One thing I hate about my boat is all the holes in the bottom. About 19 through hulls including 3 for transducers, two bolt holes for hull anode, and one shaft.

One way to reduce the holes is to use a sea chest, but I'm not entirely sure that replacing several small holes with one giant hole is really progress.

The only really good solution I've seen is Dashew's -- his sailing boats are separated into three watertight compartments, and there are no hole at all in the bottom in the main, central compartment.

That's the way my next boat will be set up. If the OP is building from scratch, I suggest he look at this (and many others) aspect of the Dashew designs.
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Old 21-04-2016, 04:03   #14
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Re: Hull designs .... questions

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One way to reduce the holes is to use a sea chest, but I'm not entirely sure that replacing several small holes with one giant hole is really progress.
Or you can (especially on metal boats) use standpipes, that extend above the waterline.
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Old 21-04-2016, 04:07   #15
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Re: Hull designs .... questions

Hi Sam

Welcome to the forum. Thru hulls can be minimised using a couple of sea chests, which is essentially a big thru hull with many hoses leading from it. However, there are some practical problems. You end up with a big hole and lot of hoses snaking around the interior. If one of these hoses is damaged the boat can still sink even if the hose rises above the waterline at some point (hoses with a syphon break are the exception). The risk of hose damage from chafe is increased by the long lengths required with a sea chest.

Aluminium boats often have metal standpipes on all thru hulls. These rise above the waterline. This means the seacock and hose connection is above the waterline. So failure of these two components will not sink the boat. Hose runs can be short and I think this is a good solution.

The rudder is also worth looking at. A cofferdam rising above the waterline is a great feature, but surprisingly it is rarely incorporated.

The other option is to divide the boat into watertight areas so if one (or even two) of the areas are breached the boat will still float. This also provides some protection from a hull breach following collision with say a container.

There is a lot of debate about the best construction material. My vote would be for aluminium, but it is also the most expensive.

Good luck in your search.
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