Build a Boat for The Great Loop?

[kmacdonald]

Originally Posted by ohdrinkboy

Samuel Seaward
1800-42
Cranes, dredgers, swing bridges and many other inventions
A pupil of Henry Maudslay
John Smeaton
1724-92
Civil engineer. Researched the mechanics of waterwheels and windmills. Lighthouse design e.g. Eddystone. Improved the Newcomen atmospheric steam engine
School/Apprenticeship. Worked as a mathematical-instrument maker.
George Stephenson
1781-1848
Railway engineer. Steam locomotives
Evening classes three nights a week paying 4 pence a week. Gained direct work experience in mining engineering /Apprenticeship
Robert Stephenson
1803-59
Mechanical and structural engineer. Steam locomotive design/bridges
Self-taught with help from his father George. Attended a village school and then his father sent him to a private school and then apprenticed at Killingworth Colliery which he did not complete but then gained valuable experience in railway engineering
Jedediah Strutt
1726-97
Knitting machines worked with Richard Arkwright
Self taught: started as a farmer
Thomas Telford
1757-1834
Civil engineer. Canal/road engineer e.g. Caledonian canal started in 1804. Innovative Aqueduct and bridge design and construction.
Attended a local parish school. Apprenticeship (Stonemason) Langholm and self taught.
Charles Tennant
1768-1838
Chemist and industrialist. Textiles/Dying
Studied at a local school then apprenticeship as a silk weaver
Richard Trevithick
1771-1833
Engineer and inventor. Steam engine (High-pressure steam engine 1800
Attended a local school but largely self taught and became a mining engineer
Jethro Tull
1674-1741
Agriculturalist. Seed drill (1701)/Introduction of improved farming methods
Oxford university
James Watt
1736-1819
Engineer and inventor. Steam engine design/Lunar Society
Taught by mother then some formal schooling-Greenock Grammar School and eventually gained experience as an instrument maker at Glasgow University. A mechanical genius who was very versatile.
Josiah Wedgewood
1730-95
Chemist specialising in pottery/Lunar Society
Self educated/Apprenticeship (Pottery/thrower) but because of ill health broke the indenture and experimented with decorations, clay types and furnace technology.
Joseph Whitworth
1803-87
Engineer and inventor. Machine tools/Screw threads. Planing machines, a power- driven self-acting machine and measuring machines. Established the Whitworth scholarships.
Attended his father’s school then as a boarder at a private school at Idle near Leeds but left at 14. Apprenticeship (Cotton spinning) and gained valuable work experience in Manchester and London engineering companies including the Maudslay workshops
John Wilkinson
1728-1808
Ironworker and inventor. Boring machine
Learnt working at his father’s side

Looks like you had to go way back. Anyone in the 20th or 21st century?

[Group9]

Originally Posted by Bash

If you feel the boat in the photo is of "modest dimensions," I need to know who manufactured those beers.

I didn't comment, because one look at that boat told me that whoever is wanting that boat built, probably wouldn't want to hear my idea of a good loop boat (unless it was for his dinghy).

[Bash]

Originally Posted by Group9

I didn't comment, because one look at that boat told me that whoever is wanting that boat built, probably wouldn't want to hear my idea of a good loop boat (unless it was for his dinghy).

Looping is not on my bucket list, but I'd sure want to do it in a power cat if it was. Probably something much smaller, however, like a Glacier Bay 2780 Hard Top. Something just big enough to accomodate a queen-sized bed.

[The Garbone]

Nordic tug would be fun.

[capngeo]

Originally Posted by kmacdonald

If your not an engineer or naval architect don't waste your time or the clients money.

Ah yes one of the "If you don't have the degree, you know nothing" guys!

Yes, I'm nothing but a humble retired fireman I couldn't possibly build a boat.... But please don't tell that to all the people running around in boats that I've built, re-built, lengthened, shortened, stiffened, straightened or salvaged please!

[capngeo]

Originally Posted by ewsponberg

Capngeo, I'm an "engineer type", so I'll offer my 2 cents worth. The boat in post #1 looks like one of the surface piercer cats from Gold Coast Yachts in St. Croix, USVI. They are good clients of mine. Those boats are built in composite and/or wood epoxy. You could likely do such a boat in aluminum, but it should be designed and engineered accordingly with proper design and drawings. That style of hull may also have copyright protections, so you should check with Gold Coast Yachts at least as a courtesy before going further. Gold Coast's website is: Gold Coast Yachts Custom Boat Builder ? Catamarans, Power Cats, Luxury Custom Yachts. Talk to the owners Roger Hatfield or Rich Difede.

The best aluminum to use is 5083 or, less commonly, 5086. You can buy some framing stock in these alloys, but typically, 6061 alloys are of more variety in shape and size and so 6061 is commonly used for framing stock, such as flat bars and angles. One always designs and engineers metal boats to the welded strength of the material--it's possible to figure out all the details and scantlings with proper engineering. The devil is in the details, which can all be figured out "on paper" beforehand.

You are going to have a huge problem with the folding bows--the loads on the joints--the connections, hinges, and controls--would be enormous and extremely difficult to engineer well for all anticipated conditions, and at the same type be totally internal to the hull so that they don't protrude outside the hull surface. The joints and controls will be heavy and costly--in my opinion, not worth the effort.

That's about 2 cents worth, but I am happy to contribute further if you have other questions.

Eric

Thanks Eric!
The metallurgy I have a good grip on, as I worked in a boatyard for years as a pup doing most of their welding and fabrication.

The stresses on the "hinge" would be large, and as I mentioned before, I tend to overbuild because I lack the engineering skill to make it "just" strong enough. My initial thoughts were to design an elongated leaf hinge similar to those used on sectional work barges, but rotated 90° to allow horizontal swing. Perhaps the answer is to allow it to swing UP which would keep the hinge and locking mechanism OUT of the water. I hadn't considered having the mechanism within the hull as I wasn't terribly concerned about a perfectly fair hull on a <12kt boat... but swinging up would solve both problems. Perhaps a small hydraulic cylinder on a bell crank above the hinge to actuate!

The boat in post #1 to the best of my knowledge was designed and built right here in Key West by the operator; he has several and I know quite a few artisans who helped in the builds.

As I mentioned, this is just a project for a buddy, from which I will likely only see my expenses covered, and the satisfaction of a nice build, well done..... BUT I have always wanted to do the loop! If all works out maybe I can talk him out of it for a second lap with me at the helm!

[kmacdonald]

Originally Posted by capngeo

Ah yes one of the "If you don't have the degree, you know nothing" guys!

Yes, I'm nothing but a humble retired fireman I couldn't possibly build a boat.... But please don't tell that to all the people running around in boats that I've built, re-built, lengthened, shortened, stiffened, straightened or salvaged please!

Don't worry, your secret is safe with me.

[valhalla360]

Keep the height off the water below 15' so you don't have to limit your cruising routes. What is the bridge deck clearance? It looks pretty high off the water.

I would keep the draft at 3' or less. You can make the trip with more but why limit yourself if you are building a boat specific to a route that is loaded with shallow water.

How will it handle with the bows folded in? There is a lot of close quarters manuvering on the loop where funky handling would be a pain. Also, I would plan at least a walkway of some sort to get to the bows in case, you have trouble with the folding mechanisim and the bows are the only way off.

How much living space will you wind up with? at 75% of a 60' boat, that's 45' and it looks like you will lose 10' on either end. That's not a lot of living space given the overall size.

[Andrew Troup]

Originally Posted by kmacdonald

Looks like you had to go way back. Anyone in the 20th or 21st century?

Well, me, for instance

[ParadiseParrot]

Marine engineering is a little more difficult than lets make a scale model from a picture of a ferry and weld her up. If building a boat instead of buying is your bag then buy the prints.
If doing the greatloop is your thing then buy anything that half ass floats and go. Its been done on shantyboats less the gulf coast parts. And get a kayak and and anchor. What do you need to pay for dockage for?

[capngeo]

Originally Posted by valhalla360

Keep the height off the water below 15' so you don't have to limit your cruising routes. What is the bridge deck clearance? It looks pretty high off the water.

I would keep the draft at 3' or less. You can make the trip with more but why limit yourself if you are building a boat specific to a route that is loaded with shallow water.

How will it handle with the bows folded in? There is a lot of close quarters manuvering on the loop where funky handling would be a pain. Also, I would plan at least a walkway of some sort to get to the bows in case, you have trouble with the folding mechanisim and the bows are the only way off.

How much living space will you wind up with? at 75% of a 60' boat, that's 45' and it looks like you will lose 10' on either end. That's not a lot of living space given the overall size.

I would like to keep the draft minimal, as after the loop, the vessel will be based here in KW. There is a lot of great skinny water cruising in the keys. Slow speed maneuvering would be no worse than any square barge. ~12x20 living space...

[Andrew Troup]

Something that occurs to me, capngeo: you mightn't need to make those hinges nearly as strong as you might think, even if you stick with the (to me, more satisfying) inward hinging setup.

What I'm thinking is this: thicken and gusset the outer 5" (say) of the two mating bulkheads, and strongly bolt the bows to the main hulls around that rim. Make the bolted connection strong enough to transfer all dynamic loads.

Make a floppy hinge, so it won't 'fight' with the bolt locations, but especially with maybe 6" of travel in the vertical direction -- for instance, with farm gate-style leaf hinges, you could space the gudgeons and pintles widely with extralong pins and double-ended pintle brackets

My thinking is that any difference in sinkage would thus be accommodated when you undo the last bolt, and the bows either pop up or sink down relative to the boat as both parts re-establish an attitude in respect of trim

(you'd have to have a crafty way of remating them level , of course, but at least then you have a visual indication of the mismatch ... also there would be challenges sealing the bottom bolts, particularly during the changeover, but I can think of a couple of possible remedies...)

What I'm saying (and unfortunately pushed for time, can't elaborate further) : if you bolt the bows on, the hinges would NOT need to handle the dynamic loads of travelling at speed and hitting waves; they just have to handle unfolding and folding in calm conditions.

As a thought experiment, they could just be loose lashings, in the crudest implementation. I'm thinking of dry-dock doors. They're not hinged at all: they lighten them by pumping out some water until they float up out of the tapered opening, then tow them out of the way.

Undoing and then doing up all those bolts might get a little 'old', though, if you had to do it every stop.... I guess an 18V battery drill with a socket would relieve some of the tedium...

[clockwork orange]

Many of the worlds best boat designers and builders of years gone by were "engineering" their boats without degrees, they just didn't know it at the time, and many of todays designers are not naval architect and don't need to be, they will job out the parts that need further engineering that may be required for whatever reason.
As far as the loop goes I also think a modest powercat would be ideal but I would be inclined to stick with something more conventional to get more usable space in a shorter package, Those Gold Coast yachts cats were designed to reduce pitch for a smoother ride at higher speeds while operating to a schedule in strong tradewind conditions which is not what you will encounter in the loop. I would look at Richard Woods 36ft design, It would probably have good resale when your friend is done also.

Steve.

[capngeo]

AT, I would think a loose fit would transmit a lot of noise as it worked.. Not good when anchoring at night. A rigid pin system as used in a sectional barge would be perfect.

[ewsponberg]

Originally Posted by capngeo

Thanks Eric!

The stresses on the "hinge" would be large, and as I mentioned before, I tend to overbuild because I lack the engineering skill to make it "just" strong enough. My initial thoughts were to design an elongated leaf hinge similar to those used on sectional work barges, but rotated 90° to allow horizontal swing. Perhaps the answer is to allow it to swing UP which would keep the hinge and locking mechanism OUT of the water. I hadn't considered having the mechanism within the hull as I wasn't terribly concerned about a perfectly fair hull on a <12kt boat... but swinging up would solve both problems. Perhaps a small hydraulic cylinder on a bell crank above the hinge to actuate!

The hinge on top would be preferable, in my opinion, and opposite that there has to be a heavy-duty positive latch mechanism. The latch and the movement of the bow opening and closing can both be hydraulically operated. The thing that you have to appreciate is that when the boat is running in normal closed configuration, the hydrostatic and dynamic forces on the hulls forward of the joint are going to be huge. Normally, the hull skin and its internal stiffening would handle the stresses. Now with the joint, you are breaking the skin and structure, so all those loads have to go through the hinge and the latch. You've got high loads pushing up on the hull (and down, for that matter as the bows pierce the waves) and a long moment arm forward of the joint (halfway between the joint and the bows, approximately). These have to resolve themselves into much higher loads on a relatively short moment arm (the distance between the hinge and the latch); the moments have to be equal and opposite. Plus, the hull sides experience high shear stresses running vertically up and down the hull at about ±45° to the hull axis, but the joint breaks their path. So there are all sorts of stresses that have to concentrate into relatively smaller parts. The hinge and latch parts have to be big enough to handle all these loads. That's why I say the idea, while commendable, will be difficult to engineer.

Another thing to consider is that the bulkheads at the joints are both going to be wet, open to the sea, and any parts and mechanisms penetrating the bulkheads will have to be made watertight in some way.

I'm just thinking out loud here, trying to point out the engineering obstacles that have to be overcome. I'm not saying it can't be done, but some real good thought should be applied to making the parts large enough and reliable enough to work.

I have another thought, however, that may obviate the need for foldable bows. The point of the original design as offered was a wave piercing hullform. The example boat has really long bows. The bows don't have to be that long--they can be much shorter and still accomplish the same thing--relatively low drag and easy motion. Many wave piercing catamarans have been built with accommodations nearly the full length of the wave piercing bows, so maybe this is a problem that does not have to be.

Eric