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Old Sep 30, 2009, 09:43 AM
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Scratch Shallow Draft Buoy Tender

The CCGS Dumit (Doo-Mitt) is designed for work on the canadian arctics Mackenzie River System. drafting only 5.5' in order to operatin the the extremely dangerous rapids and very shallow Mackenzie River Delta.
The ship can attain a speed of 13 knots and can crash stop in her own length of roughly 150'

The Model will be constructed out of balsa and fiberglass for the hull and styrene plastic for the superstructure. I was originally going to attempt to build her out of only styrene, but didnt have the experience to make such a unique hull from the stuff.

It will be powered by the motors from the "wright Flyer" model with the associated esc, It will have the option of having a very limited functional frane on her fore deck, probably slewing and topping. here are some pictures to start with

G-O
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Old Sep 30, 2009, 11:41 AM
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Bozeman, Montana, United States
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Neat boat. If it were not for the ice, she could use a paddle wheel in the stern for really shallow ops.
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Old Sep 30, 2009, 02:08 PM
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she actually has propellers in tunnels higher than the keel, when the ships not moving, you can open access ports and reach down to the struts, the propellers actually break the surface until it flushes out all the air! Paddle wheeler would be chewed alive in the currents of that river...
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Old Sep 30, 2009, 03:36 PM
Age quod agis
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Great build subject choice.

Interesting having props in tunnels like a jet boat.

How are you going to do your props? Scale as the real ship is, or standard rc style with exposed props?
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Old Sep 30, 2009, 03:55 PM
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I am going to get some 1/2" brass props from Harbour hobbies and hope that they will come close to fitting... i may have to file or dremel them smaller, but I'm hoping they are atleast really close...

i want to have it close to to scale, I'm not incredibly skilled at detailed, but i like making it engineering-wise close to scale.
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Old Sep 30, 2009, 05:00 PM
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Before the Columbia river was dammed and turned into a series of pools, operations were as wild as anything on the McKenzie. Sternwheelers negotiated extreme sections. In some places, the current and rapids were so bad that the boats were warped upstream by their capstans during runnoff. Never understimate the power of a river in flood, no large boat can cope on it's own. Yet paddlers could make it up the river, even in these conditions, via ropes. Part of the function of the rope was to control sheering in confused waters, to keep the boat from swerving broadside to the flow due to cross currents; this will be a problem for any big boat (or canoe or kayak, though they are not usually trying to go upstream :-). Downstream ops were dependent on the skill of the pilot/skipper in steering through the rapids; this is the same no matter what the propulsive device. Operations on Missouri and other US rivers were tough before the Army Corps pooled them, though the Columbia was probably worse. Paddlers were used by choice, long after props were perfected.

For shallow ops, paddlewheels are superior to screws. Paddle wheel boats traversed US Western rivers with low water - big boats could opperate on 3' of water, though 4' was prefered. The extra foot under the hull reduced drag substantially, it was not needed for the paddle. Paddles are less susceptable to damage from rocks and trees than props; run a tree or boulder through your tunnel and you will be totally disabled, walk a paddle over the same tree or rock, and you will break a few buckets, but you will still be able to operate. Something to think about when you are operating on the McKenzie during flood :-/ And if your tunnel is screened or barricaded against trash, then you have lost a lot of power right there; talk to a military chopper pilot about the power-eating screens over his jet engines (but better that than ingesting a rocket or grenade).

Tunnel props are very inefficient, chosen these days for reasons of style and prop-tradition. The inefficiency can be deduced, for the non-engineering background individual, from the lack of tunnels on other craft. Or, blow up a balloon through a straw and compare the effort to that of blowing up a balloon the normal way - tubes eat up energy. The "style" comes from the fact that living naval architects don't have the paddler experience, they go with "modern" methods (and politicians who fund govt. boats are all about modern and style). In fact, up to 500hp, paddles are more efficient than props.

The reason paddles are no longer used is a) cheaply available hp (above 500) has increased as diesels became more reliable and powerful b) it is very hard to up the power of a paddlewheel hull w/o extensive rebuilding (need bigger paddle, thus the support arms need changing, aft buoyancy may need adjustment, etc.). So, as trade developed and longer tows were becoming economic, towboat operators discovered that they could refurbish existing prop boats (add hp) more cheaply than existing paddle boats. Plus, pools have different requirements than wild rivers, so the paddler has faded away. But it is still the best tool for some tasks :-).
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Old Sep 30, 2009, 08:14 PM
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I do understand the love of paddlewheels but with same size engine plant in just about every category (especially resistance to surface debris damage) a well installed screw propeller will win hands downs.
http://en.wikipedia.org/wiki/HMS_Rattler_%281843%29
Foo
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Old Oct 01, 2009, 12:33 AM
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Foo: Not according to naval architect Alan Bates, my source for the 500hp statement: "The western rivers steamboat cyclopedium", pg 92.

The famous Rattler experiment, often cited, was fixed/deficient. Unfortunately I can't remember the details, but by modern experimental standards it was a fraud. For instance, measuring hp was, and still is, not as straightforward as people think, especially for steam. There are a plethora of systems that must perform to deliver power, via steam, to a paddlewheel. The Rattler was new, it's opponents were not; I leave it to the reader to decide if any of the 2 years of tests were "fair". Thus comparing 2 ships is not straightforward, and thus is not necessarily accurate.

It may be possible to bench measure brake hp of an engine, but "there's many a slip twixt the cup and the lip" when it comes to measuring/calculating actual delivered hp. I know aviation best, so here's an example: no WW1 replica plane will work with a modern engine of the same hp as the original. The modern engine develops hp at high rpm, the old engines developed hp at low rpm. Low rpm props are more efficient than high. So, putting a modern engine on a replica will not, even with modern props, produce the same performance as the old engines with the old props.

The Royal navies' Victorian engineers were sharp cookies. No doubt they did their best. But the paddlewheel's other op deficiencies (listed in your Wicki article) were the reason they were dropped for naval vessels. But for wild rivers, they would still be the better choice. Just as props are the better choice for tamed rivers (pools of constant depth and no debris).

As far as damage resistance goes, lose 1 blade of a prop and you are near-dead in the water (the vibration of the unbalanced screw will tear out the shaft bearings at anything over Dead Slow, and you will sink). Lose a few wooden buckets from the paddle, however, and you continue on at near top speed. Which propulsive device would you like if under fire at the time? :-) Props suck surface debris into themselves all the time. Floating lines wrap and foul the blades (tugs and ski boats), logs get chopped, seaweed immobilizes, etc. A paddle can swallow all that and laugh, or at least *grin*.

For many modern technologies, the old ways were better. Technology does not always "advance". For instance, over a short distance, you can outrun a car. And you can certainly outmaneuver a car on foot. Horses will go thru terrain where wheeled and tracked vehicles will bog down. Biplanes are stronger and stiffer than monoplanes (truss vs cantilever beam). Carbon fiber and big engines and style are the reasons airshow pilots have turned to monoplanes. But watch John Mohr fly his 60year old Stearman biplane - it can do more aerobatics than I, an aerobatic Stearman pilot, ever expected :-). And carbon fiber and the binding agents wear out, wing structure becomes suspect. Greg Poe, airshow pilot, had to replace his carbon fiber plane. Look at the *multiple* Airbus composite construction tail failures (only the ones that result in fatal crashes make the news, eg Oct. 2000); if it were not for politics, the Airbus would not have retained it's US airworthiness certificate, in my opinion.
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Old Oct 01, 2009, 12:41 AM
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Oh, I like this project already!

Tell us about the Wright Flyer motors and esc. Can you buy the power package without having to wreck the plane to slavage the motors? (I was getting real good at wrecking my plane... )

I assume the esc is fwd only? How will you tackle reverse (if at all.)

Last question before you proceed with the build: are you going to use uj's or tubing to connect motors to shafts?

Excellent looking start!
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Old Oct 01, 2009, 01:14 AM
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Wow...not to hijack Guards' thread more than necessary but I second Brooks' posts. Paddlewheels are very efficient and tunneled props are very inefficient...both have their place and were/are used for specific reasons. Two examples...first, Crowley's tunneled tug (tow) boats. They are used for shallow rivers but do not make efficient use of their horsepower...I've worked side by side with their Pt. Thompson (a tunneled boat) on a boat of less hp and the Pt. Thompson is quite gutless...but works well for its intent. Second, the sternwheeler Portland worked doing ship assist in the Columbia River until 1980-81! I work with some old-timers who worked on the sternwheeler and they say she had amazing power. She was replaced with a 3600 HP tractor tug also called the Portland. To me, that says a lot...sternwheeler replaced with a z-drive.
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Old Oct 01, 2009, 09:14 AM
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LOL
the never ending debate... It was up for grabs whether the paddle wheeler or the propeller was the better propulsion method. it came down to a tug of war believe it or not, of two sister ships, each had identical hull forms and identical steam power plants. the exceptions being one was a side wheeler and the other driven by a propeller. the propeller boat won and thus industry has continued on with the propeller.
never thought i would use that little piece of college education haha

I still have to disagree on a paddle wheeler on the Mackenzie however, there are full blown rapids that these ships have to manouver through, i've been there, and the manouverability of having four rudders directly behind the twin propellers in their tunnels is tested to its limits! lifting a buoy in 12 mile an hour current is not something i would want to do with a single paddle wheel behind me! of course this is mostly opinion based and only a little education based.....

Tugboat Andy- the motors and esc come seperate if you want to order them, however they were on clearance from great hobbies in PEI, so i dont know if you can still get them, but they were available individually. as for reverse, thats a no go. this one will be pretty simple, put it in the pond and let er rip! If i ever get more ambitious, i guess i could cannibalise a HD servo for the electronics. and the couplings and stern tubs are stull up for "tender" i havent found that stuff yet and dont have experience working with such small equipment, i saw a thread somehwere on here that was using model train couplings for small stuff like this. might be an option if i can find a supplier here in canada...

G-O
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Old Oct 28, 2009, 07:42 AM
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A little progress

Heres a couple of shots of her at present. Started shaping the propeller tunnels and ordered the propellers. had some 0.5x0.5's but they were TOO small. didn't think i could do that! I have a small brass crane pedestal that i made for this one last summer, so i just have to install that now, and if the weight allws it i can have a semi functioning crane over the buoy deck!

Regards
G-O
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Old Nov 07, 2009, 09:24 PM
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oops!

Made some progress today, sanded the hull a little more and was ready to start willing the hulls, and accidentally forgot the hardener in the filler! so now i have a very gummy hull! not sure how to clean all of that off, but i guess it will harden when i put more on top of what i couldnt scrape off that has hardener in it...

I purchased some more hardware and have the steering gear mostly worked out. this little ship has four rudders on its stern, so that presents a little bit of a challenge! fortunatly they all hang off the transom. the new propellers came in, they are .6" diameter, pretty small four blade props. but will look awesome. I started putting the crane together as well. it is coming along nicely, i have the main deck and upper deck laid out with pieces of styrene to glue the bulkheads to. and have been making steady progress there.
all in all, its coming slow but steady!
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Old Nov 07, 2009, 09:31 PM
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Not a skilled builder you say?... C'mon here i am a crane operator and cant cut styrene straight enough to pass ..You build them for fun and it looks awesome ..


Your build looks great ...
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Old Nov 08, 2009, 12:20 PM
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Fortunatly pictures don't tell the whole story! thanks to Umi's little tutorial on brass soldering, my joints are getting nicer, but still not perfect! I am trying to figure out how to make this one have limited motion, topping, and slewing. we'll see how ambitios i get, as far as the hoist goes, i've run out of functions on this ones controller, and servo's for that matter.

G-O
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