Thor

[mike farrellParticipant @mikefarrell21522]

Another nice project which I think you will be justly proud of . When you finally finish the project I would like to buy a copy .I have found a way of downloading your plans ,its simple let my daughter do all the internet plans .Michael

[Paul TParticipant @pault84577]

Hi Mike

Thank you for your kind comments, at the moment I am still playing around with the design (as can be seen from the cardboard mockup) but I should bottom it soon and hopefully be able to produce an understandable set of plans.

I would be more than happy to send you a set as soon as these plans become available.

All the best

Paul

[Paul TParticipant @pault84577]

Hull layout

Lots of heavy equipment (9kg so far) so it wont need much extra ballast.

Paul

[Paul TParticipant @pault84577]

I spent a very fruitful hour at Ellesmere Port show watching the model tugs working and seeing how they react under different conditions and then mooching around the club stands looking at tug hull shapes and tow hitches.

As a result of my happy day in the sun I have changed the underwater profile to Thors bow to reduce resistance and provide more lift.

Paul

[Paul TParticipant @pault84577]

This drawing shows the changes to the bow and underwater profile.

The bridge superstructure and propeller sizes have also changed.

Paul

[Bob Abell 2Participant @bobabell2]

Paul…….Can you do a 3D model of your latest design, similar to the last example?

So we can appreciate the new shape

It looks excellent

Bob

[Paul TParticipant @pault84577]

Just for Bob

The bow is now vertical and the chine has been extended up to the new bow, two mini keels have been added to each side of the flat bottom to protect the bases of the pumps, propeller size is now 75mm and the Samson post is yellow.

Paul

[Paul TParticipant @pault84577]

Some progress photos

Sorry about the state of the card as its been cut and carved about but you can get an idea of the general idea.

Close up of the revised bow.

A general view of the bow showing how it has been squared off above the waterline.

A long view of the stern showing the locations of the kortz nozzles

Paul

[ashley needhamParticipant @ashleyneedham69188]

Paul. Forgive me to dare to assume you have not thought of it  etc etc BUT ….the rear end seems very blunt underwater and appears to be impeding reverse water flow or ..?

Ashley

Edited By ashley needham on 04/03/2014 16:14:21

[Paul TParticipant @pault84577]

Ashley

Thank you for the interest.

The only reason for this tug to use reverse is to stop the forward movement, if its towing in reverse then the operator is doing it wrong.

As the original concept was to create a boat capable of winning towing and steering events it might help to understand the design better if you think of Thor as a 3ft tug rather than a model of a larger ship.

Paul

[Colin BishopModerator @colinbishop34627]

Paul,

I think Ashley has a point but it's not just about going astern. Ideally you need a smooth water flow ahead of the stern to deliver water to the prop. Looking at your photos it would seem that the props will cause a low pressure area in front of them which will need to be filled by water rising vertically from under the keel. I suspect that you may find you get a lot of thrashing about in that area which could cut down on forward propulsion as the props are having to do extra work to suck the water in round right angle bends before they can expel it.

Colin

[Bob Abell 2Participant @bobabell2]

Excuse me, kind Sir…….Our steering comps are full of reversing exercises and most boats don`t like it!

Might it be another good idea to make your tugboat, good to steer in reverse?

Steering comps are not my cup of tea….btw

Bob

[Paul TParticipant @pault84577]

Colin

The underwater stern is a design compromise between the need for a wide hull and allowing adequate water flow to the propellers, the pictures don't really show the complexity of the hull at this point.

There should be sufficient water flow around the rear of the hull to feed both props without creating negative pressure areas.

Additional water also flows under the hull

But given the concern expressed by Ashley and yourself I will have a look at reshaping this area without compromising the equipment space.

Bob

Good point about reversing during steering events, Thor has a very flat / low stern which might swamp during excessive reversing.

 

Paul

Edited By Paul T on 04/03/2014 18:21:40

[Colin BishopModerator @colinbishop34627]

Paul,

As always, the proof of the pudding is in the eating. Your current design will probably be OK at low revs but I suspect there might be problems when the throttle is opened up a bit as the props will be starved of water.

If you could bring the lower strake of the hull aft inboard then the supply of water to the prop is likely to be considerably increased.

Colin

[Dave MilbournParticipant @davemilbourn48782]

My take on this is that if that shape were the most efficient one then all full-size tugs and ORSVs would be made that way. They aren't. In fact all have hulls which turn upwards (to put it crudely) ahead of the Korts. I also recall some serious steering problems with a model of a canal narrow boat which were caused by a flat vertical hull just ahead of the prop. All in all it doesn't look like a good idea.
I would seriously consider some re-thinking this area of the model if I were you, Paul.

Dave M

[Paul TParticipant @pault84577]

Hi Colin

Unfortunately, as with everything in life, a solution creates another problem and bringing in the lower strakes are no different.

Any changes in this area will impinge within the motor compartment which, as you can imagine, is full of big electric motors and outlet pipes for the thrusters. Looking at the existing design I have 8mm of leeway to adjust the strakes but I will have a look at moving the motors forward and freeing up some more space.

Hi Dave

I take the point but in my defence I have spent some time in forming the shapes on this hull to maximise its ability to pull heavy loads at comparatively low speeds.

 

Paul

Edited By Paul T on 04/03/2014 19:10:23

[Dave MilbournParticipant @davemilbourn48782]

I take the point but in my defence I have spent some time in forming the shapes on this hull to maximise its ability to pull heavy loads at comparatively low speeds.

As, I would suspect, did the designers of Aziz, Fairmount Alpine etc etc. That said, m'duck, the proof of the pulling will be in the reaching (Close, Beam and Broad).

DM (I'll get me coat…..)

[ashley needhamParticipant @ashleyneedham69188]

Paul. Sorry to have raised this hornets nest. I am only a seat of the pants designer, but is there leeway to move the props BACK a bit?? this would obviously create more hull-prop clearance, just a thought.

A small shelf at the rear disguised as a bumper would stop water rising over the stern somewhat when reversing and look the part, would not have to be particularly deep, just enough to break up the water.

I can understand the "stop only" requirement for towing as obviously it is a bit difficult to reverse a barge using the tow rope!

Ashley

[Paul TParticipant @pault84577]

Ashley

Don't worry about it as I wanted to start a healthy debate and all of the comments are gratefully received. The whole purpose of showing Thor on the forum is to demonstrate the different processes that are gone through when creating a design.

Your comment about stopping water rising over the stern reminded me of something I witnessed at Ellesmere Port.

I took some photos of model tugs coming out to push a narrow boat and amongst them was this little Tid

As you can see here the operator has engaged power and the little Tid is pushing hard

Still pushing hard with plenty of freeboard

But as the narrow boat turned it started to push the little Tid backwards and worse still the stern is going down and the boat is starting to swamp.

So a lesson is learned and I am going to increase the height of the freeboard on Thor

Another problem that this little Tid had was rolling in a light swell.

Obviously the roll is simply due to the small size of the model but it has given me food for thought about increasing the size / mass of Thor.

Paul

[Bob Abell 2Participant @bobabell2]

Nice action pictures, Paul

Plenty of food for thought

Bob

[ashley needhamParticipant @ashleyneedham69188]

Paul. Thor is much wider and squarer than the Tid, so in the same situation I would not have thought that Thor would give cause for concern like the Tid, whose owner must have been having a….moment.

Thor has two props so will not pivot about the single one, like the Tid either as thats what also may have been an issue.

How about making a slight rearwards rake to the stern, so that it will tend to lift rather than build up a wall of water?? Having the rear deck area fully watertight will also stop rear flooding being an issue, along perhaps with generous freeing ports, without increasing freeboard.

How about ALSO an internal water tube stabilising thingy/tank wotsit ?.

Ashley

[Paul TParticipant @pault84577]

Ashley

In its current guise Thor has a larger underwater mass than the same scale size of Tid and shouldn't roll as much but I am playing around with the rear of the hull to increase the sub surface water flow and giving the freeboard some thought.

There isn't any room for any internal stabilising tanks as the base of the hull is fully covered with equipment but I am fairly confident about stability as the mass of the equipment is now weighing in at 10kg.

Paul

[Bob Abell 2Participant @bobabell2]

Can I make an outrageous suggestion and throw a spanner in the works?

Would there be any mileage in a paddle tug?

A paddler with independent paddles can turn on a sixpence!

Add a GE prop and it could do a Square Dance!

It would make an interesting model to play with on the water, with plenty of stick juggling

Perhaps not…..Pity

Bob

[Paul TParticipant @pault84577]

Bob

You are the undisputed master of the paddle boat and so if you think that the idea has merit then why not design and build one?

We could have a tug of war at Haydock.

Paul

[Paul TParticipant @pault84577]

Changes to the stern

Plenty of room for water flow and the underwater angled profile will prevent the stern from submerging whilst going astern

[Author]

Posts