Paddleducks
Large Paddler Builds => Paddlewheels (Large) => Topic started by: Eddy Matthews on November 21, 2006, 08:07:35 AM
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I was always lead to believe wheels made the boat more stable on the side...I don't know if this is only rumour though.
Exactly the oppossite Sean! The paddlewheels etc add no extra floatation, only a large amount of weight hanging on each side.... Try sitting two people in the centre of your boat - Nice and stable yes? Now move the two people so that one is sitting on each side of the boat - Nowhere near as stable then is it?
This is exactly what happens when you add paddlewheels, sponsons and paddleboxes... You DECREASE the boats stability!
Ask anyone who has modelled a sidewheeler, and most of them at one time or another will have made a model which was totally unstable, or at the very least tended to dig a paddle into the water on a turn - Even when you straighten the boat up the paddlewheel stays dug in and the boat runs with a frightening list to one side or the other!
Yet another thing to think about!
One final point - my posts are intended purely to HELP with your builds, not to put you off in any way. Yes small paddlers can be made to work, but they need careful planning and a lot of thought to be successful. Trial and error is okay to a point, but the basics must be right (or nearly right) in the first place or you are doomed to failure. Hopefully if some of the major pitfalls are pointed out you can avoid some of the issues that many of us modellers have experienced!
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And the pitfalls that we discover we can write about and stop other paddler builders making the same mistake!
Attached is a photo to show the effects of bad and prove that even the big boats can do it. It's dark because of the sailpast buts it's PS Alexander Arbuthnot with everyone standing on the side of the boat that already has a room full of tools on the side....
Don't worry Eddy I'm not taking your posts as being disheartening! This advice is needed...especially for first timers like myself. And if advice isn't taken...well just take a look at Lady Rae! Michael...a photo perhaps?
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Without any proof, I don't think that the proposals for Grebe or SJ will make either unstable, and certainly not in the calm waters in which they will be used.
Sean's photo of AA listing are interesting, but presumably well within stability limits (the thumbnail is black, but clicking to bring up the photo in full reveals the image).
A Sydney twin-deck screw ferry did capsize when everybody rushed to one side during a regatta or watching something famous. IIRC the era was the 1930s, and the vessel was one of the R fleet (Rodney? Radar?).
PS Ruby was a lean greyhound. There are published references to crew members rolling barrels of water from side to side to enhance stability around curves. The current restoration has put only the wheelhouse back on the third deck, and not the cabins or music room. AFAIK this is to provide stability to meet modern survey requirements.
The small PV Eliza something has two decks on a short hull. It wears outrigger floats (like training wheels on a child's bicycle) to enhance stability.
We may laugh at PV Lady Rae being overbodied, but is it unstable?
I often ponder that PV Shiralee looks top heavy (two decks on a short hull), but that doesn'ty prove that it is top heavy. I was cruising alongside for half an hour in July, it it wasn't listing. I did draw a design at the time which recessed the lower deck into the hull.
Photos of all of these vessels will appear in the discussion thread in this forum in due course.
Regards,
Roderick B Smith
Rail News Victoria Editor.
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Lady Rae rocks from side to side and sits in a list and now has outrigger pontoons to support her I believe...unstable I believe.
Consider PS Ellen. There were reports after lengthening that upon turning a bend she would list so much that the skipper could get a cup of water from the river (of course the river was obviously cleaner back then!) I've seen photos of Ellen...I can understand where these stories come from...her size is impressive but definately wasted.
Many steam launches carry their boiler in the front of the boat...does this assist stability...I would assume so...but I would also assume then that the quite a few people are required to sit in the stern of the vessel to balance it out...my thoughts on launches.
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Also the PS Marion, I have cruised on it several times now, and it as nearly always on a list to left (unless you were lodged on a sandbar at Goolwa like we were and getting towed off by the Oscar W). Always there is one paddle deeper than the other... But I wouldnt call the Marion unstable.. It would catch a lot of that howling wind down the long wide straights of the Murray in SA and it has proved stable.
Sean, that is a great photo of the AA on its classic list, I also have a few of it on a list!!
Do paddles ALWAYS decrease the stability of a vessel? Or just sometimes?
With the SJ Hull being nearly (half as wide as she is long) 6' wide and only being 14' long, it is a stable boat, and was used to row out to ships back in the 20's on the rough Southern Sea at Portland...
And paddles are the same both sides, so on flat water does it decreased the stability or is only when the boat is getting pitched around on small waves and one side goes up with a wave and the other down that the boat goes over or under???
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paddler's have a decrease in stability when they broad side caused by
too sharper turn under power or wind shear.
it's just the method of the beast it can't be helped when one paddle enter's the water with more float than the other unless it's a stern wheeler.
that's where the experiance's of the crew and captain are needed,it's more common with flat hull paddle steamer's than hulls with multi chine hulls,the shape of the hull help's increase or decrease the problem.
cheers Anthony
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Like Etona she has a round hull and tosses and turns in the wind like mad. I've heard stories of her on Lake Alexandrina tossing and turning like mad!
So in this way I'd say the hull shape contributes to this...random anecdote probably but I thought it was fitting!
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Hi PD's & a quote from Eddy a few days back
"Ask anyone who has modelled a sidewheeler, and most of them at one time or another will have made a model which was totally unstable, or at the very least tended to dig a paddle into the water on a turn - Even when you straighten the boat up the paddlewheel stays dug in and the boat runs with a frightening list to one side or the other!"
The understanding behind this is pretty simple :hammer when we think about it
Both paddles on the common shaft are in fact acting as 1/2 style gyroscopes... which have kinetic, and hence potential energy
So if one paddle DIGS in & under [water], the resultant is that this gyroscopic energy in the opposing paddle is transmitted through the paddle shaft to attempt to accelerate the wheel that is [under water] & hence increase the immersion of that wheel.......
All very important points in understanding the design of paddlers be they any scale.......Derek :)
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Sorry Derek, dont have a full understanding of that :oops: :oops: :oops: !!
Does that mean that if one of the paddles is under the water more the other will try and make it go faster and digging it in more??
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Hi PD's & yes James.....
1) if one paddle is [greatly loaded or immersed]...[lower than], the opposing paddle will attempt to free wheel & hence the kinetic {rotational} energy is transmitted via or to the fixed paddle shaft
2) So if we think of the paddle wheel that is [greatly loaded or immersed]..., the resultant is an 'increase in rotational moment' in the opposite wheel in the attempt to 'consume' the increased kinetic energy with the water & hence to dig in even further
3) Now a secondary argument could be considered here in that both wheels are on the common shaft & the above could not happen as any attempt to overspeed by the inboard wheel would be negated by the outboard wheel
4) This is not spectulation as points 1) & 2) are fact & hence the importance of consideration of design elements prior to building in any scale - Derek :)
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Thankyou Derek!! That is now at my level of understanding, just another newbie learning along the way :D :D :D :D :D
Would it be a better idea to have independant paddles as to avoid this happening and doing some damage?
I have been thinking of that for a couple of hours now..
Cheers
:beer
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Hi,
I think, a paddler is not unstable, if it has a big boiler and a fine and heavy steam engine in its hull!
But, if you fit a light Diesel engine with hydraulics instead of a steam engine, maybe!
Andy
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hi everyone
I'm new and I have no experience with paddlers, but when I read this stability thread so I have one question,
are there some mathematical basics for calculating the stability??????
Jost
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Hi PD's....& to answer the question from Jost... :thinking....yes when Noah built his vessel I think :whistle he probably would have consulted with one of the local Naval Architects
These people were really only mathematical number crunchers...however the real issue for model applications is we cannot scale water pressure/surface tension/wind....... as our mother nature :respect still controls this
So if you build a model with a high surface profile @ any scale .... :hammer....& a light breeze of 10 Km passes...your vessel is subjected not to the scale of the breeze but to the third power & hence high windage ....which causes all of the problems
Good reading here is ...researching a thread by 'bundywrap'........
To understand basic hull stability....try a GOOGLE search on 'metacentric point of balance'........'of vessels' ....ten years worth of good reading......Derek :beer
http://www.onemetre.net/Design/Balance/MetaCent.htm
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perhaps it would help to lower the center of gravity if the wheels were placed lower on the gunwales, not on level with them? In looking through the forums I saw some pics of some boats like this. One was the swiss boat and a couple of the small english boats. I like the way it looked and would like to copy the design for my boat but I am afraid the shorter height would mean smaller paddle wheels and thus less effeciancy/power (larger wheels better efficency). I notice a couple of the boats had wheels with 2 foot diameters and that seemed a bit small to me.... Does anyone have any ideas/suggestions? I just finished working the bugs out of my hull and have the material to start work on my paddle wheels/propulsion system. Thanks!
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Glyn Lancaster Jones of the Traditional Boat Shop in Wales, designer and builder of the Swiss paddle wheeler and of "Minette" see Jersey Lily argues that the sponsons for his paddle wheelers, ie the timber framing supports for the wheels do actually add a significant amount of additional buoyancy. Glyn's designs have small diameter wheels with the shafts passing though the side planks rather sitting at the deck level. The comment was made to me via an email because as an Aussie I was a bit concerned by the rather narrow hulls in Glyn's little paddle wheelers (4'6"). Of course his hulls are kept narrow to work the UK canals which is not an issue for us boaties down-under.
Rob
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I would love to know how Mr Lancaster Jones manages to come to that conclusion.... The sponsons do not (or should not) touch the water, so all they add is extra weight to each side of the hull, and cannot possibly add to the vessels stability or bouyancy. The exact oppossite is true, they ADD to the vessels displacement, therefore decreasing bouyancy, and their position and weight can only DECREASE the vessels stability. It's the laws of physics....
For someone who claims to be a boat designer I'm amazed at his statement!
Regards
Eddy
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maybe he maens "emergency" buoyancy, you know like marine foam in case he sinks? :squareone
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Hi PD's.....I can only think there may be some misunderstanding of the authors comments or works......does anyone have a copy to scan & post here? ....as one page would not breach any Copyright.........
Getting closer to our big OZ day :vacation ..............Derek.......:beer.....
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....I am afraid the shorter height would mean smaller paddle wheels and thus less effeciancy/power.... Does anyone have any ideas/suggestions?
How about if you make feathering wheels? having the floats enter the water at a relatively upright angle should enable the use of a smaller wheel, more deeply immersed.
Placing a 'simple' paddlewheel deeper in the water causes the fixed floats to push water down as they enter and lift it as they leave giving no extra motive force but causing the engine to work harder...
P V Tamati (?) in New Zealand appears to have quite small wheels (apparently based on those fitted to Maid of the Loch)
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I think this discussion is working at cross purposes. Not all boats are equal and my understanding is that some of the smaller paddle wheelers do indeed obtain some reserve buoyancy advantage from their sponsons in much the same way as the floats on a sailing trimaran do skim or kiss the water under certain conditions.
This is what I understand is happening in the small paddle wheelers designed by Glyn Lancaster-Jones. In fact the "Minette" at 20' long and 4'6" beam (see Jersey Lily in the link below) is a very narrow hull. However the wheels at 28" diameter locate the drive shaft at about 14" up from the bottom of the hull. Glyn actually constructs the sponsons of full section timbers with positive buoyancy acting like "training wheels" and are designed to limit the amount of list of the hull. I have a quote somewhere from Glyn on this subject and I will add it later if anybody is interested.
Another example is the little saloon paddle wheeler "Firecrest" (see also link below): 15'3" loa and a very modest 4' hull beam with 24" diameter wheels. This time the drive shaft is only 12" up from the bottom and with 9" draft the bottom of the sponsons are just skimming the tops of the waves. In this design the sponsons are actually boxes deep enough to use as additional storage with the top of the sponson boxes actually at deck level.
However Eddie I readily admit that a larger paddle wheeler with steel wheels hanging over the side of the hull with the drive shaft at gunwale level or above, would certainly offer no stability advantage by such a rig.
I have actually been sent a photo copy of the article"Firecrest is a trailable paddle steamer" reprinted from an old copy of "live Steam" magazine. An interesting little boat with some very clever features.
http://www.steamboat.org.uk/register/html/jers0289.htm for "Jersey Lilie/Minette".
http://www.steamboat.org.uk/register/html/fire0210.htm for "Firecrest"
Both links have photos of sponsons just skimming the water.
Hope this helps.
Rob
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I have now found the quote from Glyn Lancaster-Jones on the stability of the "Minette" design and the advantages of the sponsons:
“The stability of a side wheeler is tremendous, as there is enough buoyancy in the sponson structure and deck to make it very difficult to dunk them, let alone push one of them right under. I have stood on them, and they barely touch the surface. They are a plywood deck on a frame with support brackets underneath. Those fore and aft of the paddle wheel are taken right through the hull skin and attached to full or partial bulkheads. The paddle beam as it is called spanning these two is made very strong to protect the wheel from damage and to mount the "star-centre" for the feathering mechanism. Where possible I make the upper part of the paddle-box removable.â€
These comments are not for all paddle wheelers and were sent to me last year via email in relationship to the question of the stability of the small side paddle wheelers. Hence I am giving you a copy of a personal email which I trust Glyn approves.
Rob
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I noticed a lot of the smaller wheels were feathered and I thought about doing the same...problem is I don't know how they work :thinking I've seen pictures of them and from what I can gather, the floats pivot, I can see they pivot when the wheel comes around and the blades fall forward to act like a plow on the water, but after they leave the water on the back side of the wheel what do they do? And why do they do it?
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....I am afraid the shorter height would mean smaller paddle wheels and thus less effeciancy/power.... Does anyone have any ideas/suggestions?
How about if you make feathering wheels? having the floats enter the water at a relatively upright angle should enable the use of a smaller wheel, more deeply immersed.
Placing a 'simple' paddlewheel deeper in the water causes the fixed floats to push water down as they enter and lift it as they leave giving no extra motive force but causing the engine to work harder...
P V Tamati (?) in New Zealand appears to have quite small wheels (apparently based on those fitted to Maid of the Loch)
I decided that I was not going to run the axle thru the hall as I had originally planned so my Paddle wheel will be 27" in diameter. (Anything bigger would look odd) with that plan the paddles would be dipping into the water about 6 or so inches. that seemed to me to be a reasonable depth because we are going for shallow to reduce the strain on the engine? any ideas very welcome :beer
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My experience is only with the small paddlers: but the blades need to be fully immersed at the bottom of the stroke. In most small paddle wheelers this means that they sit pretty much in line with the bottom of the hull and say with 6" draft the blades are about 6" deep. Obviously this is not true for the larger hulls.
The most common feathering wheels are known as Morgan Wheels. Google has many links on this subject and the one below is one of the clearest:
http://nautarch.tamu.edu/PROJECTS/denbigh/WHEEL.HTM
My next paddler will be electric powered and somewhere between 17' and 20' feet long and at this stage I do not intend to fit feathering wheels. I'm not sure they are worth the extra effort and expense, but others may disagree. Certainly many of the UK builders of small paddle wheelers like them. I will follow Glyn Lancaster-Jones advice and construct the wheels and sponsons in such a way that I can retrofit the Morgan type wheels if I feel the hull needs this modification.
Hope this helps.
We are all learners.
Rob
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Hey Rob, thanks for the link! when I make my paddles they are going to be immersed the 6' thing kinda worries me though, not sure if 6' is adequete to propel the boat. when I first started this project, I ran across the "paddellac." you can google it, they have a few videos on youtube.com. (they also have a website which unfortunately I can't view anymore because of a filter at work, darn!) :whistle I wrote to the guys that built it and they said their floats are about 12" in the water at the bottom stroke. that seemed a bit deep to me.......from what I've read so far it seems that shallow and wide are better than narrow and deep. But I'm still learning lol. :weight
Your boat sounds like it'll be pretty cool, Electric huh? I like the idea. don'r know if you've seen it already but they have a sternwheeler called the "New Era." it's electric and has solar panels. It would be nice to cruise around without hearing a bunch of engine noise. I'd try it too but the currents around here are pretty decent and I have visions of a dead battery and being carried out into the Atlantic lol Which is also the reason I want to get my paddle wheels right :) What type of hull do you plan to use?
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Size of blades or paddle is determined by a number of factors as is the design of props.You can seek the advice of a professional in the field (especially for traditional props), or you follow the advice of the designer or builder. Both the links above for "Jersey Lily" and "Firecrest" detail the size of the blades. The 6" deep blades I will be using are designed around a specific boat.
I am following the advice of Glyn Lancaster-Jones for my boat which will be based on the "Minette" and "Firecrest" designs. Yes I have seen the details of the "New era". I posted details at the end of last year. I'm a member of the Electric Boat Assoc. UK.
My little paddle wheeler will use an existing motor, controller and batteries from another project. Our rivers here are very gentle with tidal races only a few knots so good planning or just drop anchor when tides are on the peak. My first electric boat used a large trolling motor and we never looked like being washed out to sea!
But range must be calculated. I'm going for about 5 hours max cruising, but with solar panels on the roof that will be extended. That's another subject.
Rob
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I looked at Jersy lily and Firecrest and I know that the blades are 6" deep but the issue I'm faceing now is how wide the blades need to be I was thinking maybe 12 inches wide but I'm wondering if I could go narrower. My boat's hull from what I've seen most closy resembles the L'il Sipp. It's double ended and about 14' long with a 5' beam. My engine is half the size of Li'l Sipp though.
5 hours sounds like a good max cruising, that's pretty good for a day out on the water or out fishing. How big will the electric motor be? That's pretty nice that you don't have to worry about the tides too much. I thought about the dropping anchor idea but around here in warm weather if you stand still, you'd get eaten alive by mesquitos and Greenheads (large biting flys that swarm around the marshes. and when they bite they pretty much take a chunk out of your skin). :sobbing
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If you think of paddle wheels in the same way as you think of boat props. If you look at a small outboard of say 2hp and then compare the prop size to say a 50hp motor. The greater the engine power then there is the ability to take a larger bight out of the water with a larger prop.
I seem to remember seeing somewhere in the PD site some calculations for wheel design but there are two other ways to go.
First work with a builder who has actually built a paddle wheeler that works. Or look at sites where there are details of wheel and blade sizes on boats that are working. But note also the revs and the power output of the engine. The link below is to another small paddle wheeler "Firecrest" but have a look through that site of steamers (not too many paddle wheelers) just work through the alphabetical list and you see what size blades others are using. In some cases you can follow up and actually contact the builder. I posted a inquiry through the Steamboat site and got a reply from a fellow Aussie who sent me a photocopy of two old magazine articles by the builder/designer of the little "Firecrest" paddle wheeler.
www.steamboat.org.uk/register/html/fire0210.htm
The second approach is have a go. Give it your best shot and experiment. Trial and error works. You might get it right first time if you have done your homework. If not keep trying until you get it right.
I already have a 750watt permanent magnet electric motor running on 36volts with the necessary PWM controller etc. I will be using a 25:1 reduction in two stages to get the revs down to a cruising speed of 80rpm. I have decided that a little boat of about 15 feet will do me at this stage. When I get into the building stage I will post photos as I go. The wheels on "Firecrest" are 6 inches deep and 9 inches wide and 8 floats.
Rob
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9" sounds about right for my floats, I was reading some old PaddleDuck posts and came across the rule of 3rds how the float with should be about a 3rd of the diameter of the wheel. I think I'll go with 10" wide floats on my boat which is a little bigger than a 3rd (my diameter being 27") so we will see how it works out. Now I just have to go get the materials and wait for it to warm up a bit :whistle(it's been snowing here the past few days). Thanks for the info, I really appreciate it :beer. I just bought a digital camera at Circuit City on sale (going out of business, guess the economic crisis has a slight silver lineing :gift.) So hopefully I'll be able to post some pictures soon.
15 feet sounds like a good size, I know with my 14 footer it's pretty easy to trailer, but it's still big enough to stretch out a bit and carry a few friends to for company. I'm looking forward to seeing your pictures. Have you found a hull for your boat yet?
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Re: hull I plan to use for small paddle wheeler.
At this stage it will be either a re-worked "Firecrest". I have drawn up the offset tables for this little 15 foot design but with a wider beam (we don't have to negotiate locks and canals down-under). This will need checking with full size lofting prior to building.
Or a re-worked "Lily" a 20 footer which I will shorten to suit. Glyn Lancaster Jones the designer has offered to send me some working drawings.
The final product may well a combination of the two designs to suit. No rush as it is summer here 30C during the day. Have to slip and tidy up my houseboat, finish off an outrigger canoe I am building, build a new workshop then get on to the little paddle wheeler. So much for retirement.
Rob
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Let me return to the very beginning of this thread:
I was always lead to believe wheels made the boat more stable on the side...I don't know if this is only rumour though.
Exactly the oppossite Sean! The paddlewheels etc add no extra floatation, (...)
Well, if so, how do you then explain that THIS works:
http://www.metacafe.com/watch/1264237/jeep_vs_snowmobile_race_over_water/ (http://www.metacafe.com/watch/1264237/jeep_vs_snowmobile_race_over_water/)
:o
This vehicle does not even have a hull for any floatation, it does get its stability entirely by its paddlewheels. They obviously don't have the tendency to dig into the water, in contrary, they seem to create an upward force the deeper they are immersed.
So why should a paddler with a hull behave much different... ???
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Let me return to the very beginning of this thread:
I was always lead to believe wheels made the boat more stable on the side...I don't know if this is only rumour though.
Exactly the oppossite Sean! The paddlewheels etc add no extra floatation, (...)
Well, if so, how do you then explain that THIS works:
http://www.metacafe.com/watch/1264237/jeep_vs_snowmobile_race_over_water/ (http://www.metacafe.com/watch/1264237/jeep_vs_snowmobile_race_over_water/)
:o
This vehicle does not even have a hull for any floatation, it does get its stability entirely by its paddlewheels. They obviously don't have the tendency to dig into the water, in contrary, they seem to create an upward force the deeper they are immersed.
So why should a paddler with a hull behave much different... ???
Have you ever skipped a stone across water? That is how the ones in the video work there is NO stability from the paddlewheels, and if they dig in too deep they sink.
http://www.youtube.com/watch?v=PQRyWnr44Sg
Regards,
Gerald
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looked to me that those vehicles work in a similar way to that a waterskier does (or maybe a hydrofoil) I notice they build up a lot of speed on land before entering the water but what would happen if they stopped before reaching the other side?????
As for the idea of sponsons adding stability, I expect what was meant was that should the boat be caused to tilt to one side or other, the sponson acts like another hull preventing the boat from rolling any further...