Paddle tugs and towing competitions

[Tony Mattson]

Greetings PDers,

Since joining this group recently, I've picked some of the theory behind
paddle tugs and towing (one of many rich seams of gold in the message
archives!):

1. The turning moment is on the tug's paddle shaft axis rather than some
fuzzy point determined by a rudder (perhaps not such an advantage when
compared with modern kort nozzles)

2. The centre of effort is ahead of the tow hook pivot point (unlike a
propeller which is astern of the hook) so the danger of being capsized
by your tow is much reduced

3. The paddles being alongside the hulls reduce the stalling effect of a
propeller wash close to a large hull

4. Higher bollard pull for equivalent horsepower

etc., etc.

All of these factors seem to combine to make a compelling case for
favouring paddle tugs over screw driven tugs. Since these boats were
working boats, it'd be interesting to reflect this in scale model club
activities and so I'm wondering if any of you have put your paddle tugs
to the test in your club towing competitions?

If so can you perhaps describe the outcomes, any learnings, any
pitfalls, etc.?

Many thanks
Tony Mattson
Auckland, NZ

[Derek Warner]

All of these factors seem to combine to make a compelling case for
favouring paddle tugs over screw driven tugs. Since these boats were
working boats, it'd be interesting to reflect this in scale model club
activities and so I'm wondering if any of you have put your paddle tugs
to the test in your club towing competitions? - I think the group discussed
this a few years ago but we got lost in scale issues like - Bob builds a Schmitt
Rotterdam to fit on the back seat of the family car so it ends up as 1:96,
Harry builds a Paddler to fit on the back seat of the family car & may end
up as 1:24 - so here we have the Schmitt @ 20,000 scale shaft SHP and the paddler
@ 20 scale indicated HP etc

So if we hooked both up together & one vessel towed the other away we would end
up in a court of LAW with one side saying - but hold on!!!!!!!!!!! - to make
this even you must multiply the scale of your vessel by the cube root of the HP
& the divide by the relative water temperature of the day and add three green
banannas to BOOT in the final calculation etc etc
I think many PD's agreed with an old posting 'that all things being equal' ie., "basic hull shape size & power
transmitted [HP or KW], would result in a paddler towing the propeller propelled vessel backwards"

regards Derek

[Tony Mattson]

Hi Derek,

many thanks for your post. You've raised some interesting points
about screw versus paddle boats and the "all other things being
equal ..." argument.

What I was driving at wasn't so much the Rattler v. Alecto type of
comparison but more about group members' own towing experiences with
their models. Being new to Paddleboats I'm still finding my way
around the different capabilities of these boats so I'm really
interested to hear about experiences with scale paddle boats in club
towing competitions.

For example, one thing that concerns me a little about using a
paddler in a towing competition is the potential for 'girting' - I
think that's the term for when the tug changes direction relative to
the direction of the movement of the tow and is violently heeled
sideways when the tow comes across the beam of the tugboat.

I've seen this happen a few times with screw tugs at our club and I
suspect that model side-paddle tugs are more prone to capsize in this
sort of manoeuvre given their relative instability. Does this mean
that paddler skippers need to be more conservative than screw
skippers in making direction changes when you've got a 30kg club tow
attached?

***********************

By the way I read somewhere the British Marine Board of Trade ban on
independent paddle shafts came into play following one particular
ferry disaster where a paddle was accidentally thrown into reverse
and the ferry capsized with great loss of life. But for the life of
me I can't recall where I read this. Does any group member know any
more about the origins of the ruling, whether the story is fact or
fiction, name of the ferry, etc?

Cheers for now
Tony

[KC6OLD]

My understanding was that independent paddles were banned because a paddle
could, in a roll be lifted clear of the water, and with no load the engine could
run away and "blow up."
Dave


General manager & sump cleaner:
Foggy Bottom's Boatyard

[Derek Warner]

on Wednesday, October 29, 2003 8:32 AM, kiwikhephre [Tony] came back with a few notes
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>For example, one thing that concerns me a little about using a
>paddler in a towing competition is the potential for 'girting' - I
>think that's the term for when the tug changes direction relative to
>the direction of the movement of the tow and is violently heeled
>sideways when the tow comes across the beam of the tugboat
I have no experience here Tony with my PS Decoy being my first paddler & still a long way from
completion, however I have 20 years experience in watching tugs tow different vessels ranging from
100,000 tonne ore carriers to 4000 tonne RAN warships in enclosed waters and in every case the
tug movements were always carefully & slowly controlled & no movements are violent
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>I've seen this happen a few times with screw tugs at our club and I
>suspect that model side-paddle tugs are more prone to capsize in this
>sort of manoeuvre given their relative instability. Does this mean
>that paddler skippers need to be more conservative than screw
>skippers in making direction changes when you've got a 30kg club tow
>attached?
What do you KIWI people use speed boats for tugs??

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>By the way I read somewhere the British Marine Board of Trade ban on
>independent paddle shafts came into play following one particular
>ferry disaster where a paddle was accidentally thrown into reverse
>and the ferry capsized with great loss of life. But for the life of
>me I can't recall where I read this. Does any group member know any
>more about the origins of the ruling, whether the story is fact or
>fiction, name of the ferry, etc?
Our member 'Dave - chief engineer & sump clearner' has also come back with the out of water paddle
caused great engine over speed & distruction - details of the British B of T rulings do appear in our
archives, posted I think by PJ our founding moderator, and posssibly also by Stuart Badger - go back
to the PD site>Messages & type in a few search possibilities like 'dual paddle control' or 'independent
control' - I am sure either you will find somthing or another PD will provide the answers

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regards Derek