Model Boat Mayhem
Mess Deck: General Section => Tugs and Towing => Topic started by: john54 on July 18, 2008, 05:42:23 pm
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hi everyone
I have just got my first tug. Not really knowing much about them (used to fast electrics) I would like a little bit of a advice.
I have not had chance to try her in the Lake yet. But when I test floated her fully loaded with battery etc to get the ballast correct I had about 15% of the propeller out of the water are not too sure whether the back will dig in when she is underway or will I have to put more ballast in the stern as the lake is about 20 miles away I would much sooner make sure she is about right before I try her out any advice will be much appreciated.
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Forgot to say pen tip is waterline
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Looking at the picture I'd say that the waterline needs to be somewhere up near the leading edge of the rudder if not higher. Otherwise the prop will just throw a lot of water about and not do very much! Other people on here are tug experts and will be able to give you more precise advice.
Another possible option would be to use a smaller diameter prop!
Colin
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John,
You need much more weight in her. The water line should be very slightly above the top of the rudder. This may well make her look stern heavy so will need the bow section lowering as well. Try her in the bath, by applying known weights to the stern and bow until youare about right, This way you will know roughly how much weight to add and where..
Barry
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Or if you can add another battery, good ballast and of course increases the duration.
Bob
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Hi, I think you ideal water line would be with the water just at the rudder post penetration, another little tip would be to have it slightly bow up so that when under full power the tug wont bury her nose quite so much.
With your prop out of the water there would be lots of splash some movement and there comes a problem stopping ! full astern will LIFT the rear and that lessens the amount of prop in the water and so that will equal even poorer control.
Sorry to say this but you tug will need to be heavy and as said before removable ballast is some times best to allow ease of launch recovery but then fixed ballast is some times required in the vessels that have poor access
R
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I also agree that a little more weight would be appropriate. Here is a photo of my tug where I utilized the Billings 'Banckert' hull. Not only is there a large battery but lots of lead inside as well. You will note the water line by the stern of the vessel.
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Hi John
Perhaps you could let us know the name of your boat, and then someone could show a picture of theirs sailing. ;) . This would then give an idea of her water line.
Ken
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Shes named PLAUDIT ex port of London authority 35in x 8in g.r.p hull wooden deck wheelhouse ,Robbe 1000 ,65mm prop.
7a.h 12v s.l.a (on its side) forward of motor the only place it will fit
I could try fitting another one & put them both upright?
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There are a couple of pictures of the original vessel which show the waterline pretty clearly here: http://website.lineone.net/~alanann/plaudit.htm
Colin
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Shes LOW Not much freeboard :o
Will be stable though.
I dont know working on f/e makeing them lighter now having to add lb's of lead on this one ::)
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Think i am close on ballast now O0
She gos just over 8kg all up.
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Nice model, I remember the lighter tugs in the Thames and Medway areas, real hardworking workhorses .
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Tryed her this morning O0 Goes nice , Turns Very well , Stays cool , Looks Superb (well i think so anyway)
Just need something to tow now ;) Any ideas gents ? (cheap & easy!) if poss.
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Very nice John. O0
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John, excellent work. Looks great in the water.
Kim
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Thank you for the nice comments. I wish had done this earlier I found her very relaxing to operate no worries about speeding up and down the lake (@ 40ish m.p.h) worried stupid about radio glitches, Things blowing up etc. I'm extremely pleased with her she does not let in one drop of water the only pitfall is taking her in and out of the water especially when the level is low like it was this morning. All she needs now is a job to do ?
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Barges are very simple and quick to produce and ballast can be supplied with concrete!!
But obviously will be heavy to launch and recover!!
Bob
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I'm not familiar with the construction but in our club the barge ballast is water. Holes in the bottom of the barge let a certain amount of ballast water in which adds weight to the barge. The barge is light to transport but yes, a little heavy to drag out of the water if a straight lift is required until the water drains out. This might be discussed in more detail in another section. A barge sure adds more interest and fun if your running tugs.
Kim
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One problem with letting water flood into the barge is that it doesnt actually add weight by free flooding.
The effect in the water is nil.
I made up a barge overnight and half filed it with cement, it is still in use now, over 10 yrs since I made it!!
Bob
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Bob/John, in British Columbia we use 'heavy' water for ballast. Sorry, you probably new that was coming. Actually Bob, one of our club members barges when filled with water for ballast has a tremendous amount of drag. I probably shouldn't use the word 'weight' but 'drag' maybe? Just thought this method would make it easier for transport to and from the pond. At least we both agree that John has a very nice model on the front end of what ever he will be towing.
Kim
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By "drag" I think you mean "inertia". As an example, up in space an object is weightless as there is no gravity. But it still has mass and therefore force is needed to overcome its inertia and cause it to move. If you flood the barge down, you are towing the mass of the water that has entered the hull around the lake which is pretty much the same as saying its weight.
Colin