a few questions

[ironmatar]

really i have a lot of questions answerd around here by the many threads
however iv come up against a couple of questions monohull/vs trimiran
and single or multi masted [3] cutter rigging and capable of 120,000-130,000# cargo

[alan white]

Any trimaran of that enormous size would require a budget that would build a far superior monohull. Out and out speed isn't average speed----- and the monohull is probably faster on average. Yet it would cost much less to build and own.
As far as rigs go, a multi-mast rig is going to be more reliable and handy than a single mast rig, though a single mast would be faster, as it catches a faster wind.

Alan

[ironmatar]

well i dident consider cost really as the materials would be the same either way.
in this case the cargo space dictates to the base boat length and width somewhat 15x55x9 footprint for 2 truckloads<approx>cargo.
the idea to use a tri came from the apathy i have for hanging some great mucking bub keel everyone is hanging on monohulls these days some 10-15' below the waterline just begging to be smashed/ripped off and or flat tangeld up in submerged junk

[alan white]

No worries regarding submerged objects if the ship is big enough to carry 130k lbs cargo. At first I thought you meant 13k-14k of cargo. But if the mono depth is to be 10-15 ft, then maybe you do mean 130k-140k.
Confused.

[ironmatar]

well base masters lic is 100T 200k steel boat 70-80 maby 90k /carrying cap 110-130k and a base waterline hull length 5-1 19x95' expected draft 9-13' 3 decks lower deck cargo deck and topdeck w aft pilothouse w cutter rigging.
silica concrete wash coating for steel and doug fir decking /interior steyr monoblock desils and levi surface htdrive and 360 deg thrusters for and aft..
a lot of people have do nothing boats that are unable to make their owners any return. big boats other than racers should be functional

i relly figured a monohull was best but after reading the latest about the idec wave pericing tri going circumnav in 57 days i thought id ask around here about it.

yes it hauls but id like it to haul as fast as reasonable possabale. id like to be able to get 12-15 knots out of it.

[alan white]

Others would know more than me. I would assume any boat carrying a reasonable cargo would be fastest as a monohull. Sailing, you wouldn't get a multi of any cargo-carrying capacity to take advantage of wave-piercing. All that hull skin, designed to go fast, would therefore just be more of a dog at displacement speeds.
The 100 ft mono should approach 14 kts under optimum conditions, but under poor conditions like 5 kts breeze it will still move along nicely, leaving an equal displacement (and length) multi far behind.
In a sailing cargo boat, minimum wetted surface is what you want, I would think.

Alan

[Tad]

A pair of vee bottom hulls in a catamaran config. will provide stability without ballast. Shallow draft too. Rig could be in one or both hulls.

[brian eiland]

How about something along these lines?

New Greenpeace Motorsail Vessel
http://boatdesign.net/forums/showpost.php?p=161178&postcount=52

[ironmatar]

i really prefer a single mast or 3 masts its a matter of numerology and the rightness of a thing
given what iv been reading about aft mast rigs why tilt the mast at all brian why not use a forward mounted boom of desired length and rig it so it it holds the top spread the same distance apart at the desired point in relation to raking the entire mast forward and elimitaing rigging problems by tilting the entire mast?

[Tad]

ironmater,

If you would like clear and thoughtful answers to your questions, you really need to take time to state your ideas clearly so that they can be understood by others. I realize punctuation and capitalization are not cool, but the above posting is pure gibberish to me.

If you wish to be taken seriously please revise the above.

[water addict]

any significant cargo weight, and a monohull is better.

Multis are only good if they can be lightweight, or if you have some stability driven issue. If carrying capacity is a concern, multihull will be pathetically slow compared to a monohull.

[Tad]

[QUOTE=water addict;191450] or if you have some stability driven issue. [QUOTE]

That was the original request......how to eliminate the ballast keel.

The unballasted monohull option would be something along the lines of a scow schooner, some big ones were 85' by 36'. That’s not exactly a speed boat either. :D

Personally I believe draft could or should be a large issue for small freighters. With shallow draft or drying out ability, plus the ability to self load/unload, a small freighter can directly service areas ignored by larger vessels.

The waterline will have to be 80' to manage 12 knots economically. Standard containers are roughly 8' wide. Leaving aside the whole tonnage issue. (yes, I know that's not possible IRL) Will two hulls approximately 80' by 10' with a total beam of say 30', be faster, slower, or otherwise, than a barge 80' by 34'?

I believe a multihull might offer some other advantages as well as shallow draft, beached stability would be one, the possibility of the bow ramp for driving vehicles directly aboard, large deck area to deal with light cargos, etc.

[ironmatar]

i had envisioned a longship hull shape with the keel doubleing as the weight instead of having a great long fin or pole with bulb on it and a big cutter staysail rigging on 3 masts w a aft pilothouse. The folding crane tucks away in a compartment just aft of the second mast and the main cargo hatch is between the foot of the pilothouse and the crane compartment on deck. i specfied a 5x1 boat at the waterline in order to get some better preformance out of it 19x95' and probably 27x135 overall <bowsprit/aft jib spar>
but perhaps a diffrent hull shape might be better.

[water addict]

Tad,
I didn't see that ballast elimination was the crux of the original post- did I miss it?

ironmatar,
Much depends on the cargo. What do you envision the route and cargo to be? Definition of some basics is really important.

[ironmatar]

cargo anything you want to load in it

route where ever you want to take it.

:]

[Tad]

Water,

It seems I'm as reading deficient as everyone else....:D It's post #3 where the elimination of the ballast keel is suggested.

Ironmater,

Yes, you can have all inside ballast and little or no outside keel, but the boat will not sail to windward without something (keel, centerboard, daggerboard, bilge keels, etc) to counter the sail force. Various scenarios can be trialed in a VPP (velocity prediction program) program called PC Sail. Create a hull and rig and try different keels. Or create a rig and keel and try different hulls, or create a keel and hull and compare rigs.

[brian eiland]

My original posting here on the subject of supply vessels for Cuba has been reposted as a new subject thread here (http://www.boatdesign.net/forums/showthread.php?p=191774)

I felt it might be a 'stand alone topic' of its own

[ironmatar]

thanks for the program suggestion and yes i admit my posts are sometimes hard to read ,
as for the keel, i just have a issue with something that just begs to get hung up on everybody and his brothers uncles flotsam out there and at the depth of most bulb type affairs not a simple job to just cut something loose even with scuba gear.