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Author Topic: PS Decoy, letter from Australia  (Read 1912 times)

Paulrjordan

  • Guest
PS Decoy, letter from Australia
« on: June 13, 2005, 06:26:16 AM »
I received a fascinating email today from Derek (Warner) our
recently joined member from Australia which deals with a number of
interesting construction issues which many of us have faced and ALL
WILL face if building an operating sidwheeler. I'm going to edit it
into topics which I hope to deal with on an ongoing basis. Please let
us hear ALL your comments..THIS IS THE TIME FOR YOU RC PADDLERS TO
INPUT!!

First off...Derek has corrected a typo in his original email which I
copied here last night. The model "PS DECOY" is not 113 mm, but
rather a scaled down 113 feet

The first issue which he deals with is a pet topic for ME to comment
on.

DIMENSIONS & STABILITY:
>"Decoy is approx 1200mm LOA x 350mm accross the paddle box's You may
>note in the .xls file that I have increased the assumed draft for
>both the dimensional stability and the fact that I needed certain
>dimensional minimums to enable installation of components"

This raises the interesting subject of having to artificially alter a
model paddlewheeler's dimensions (draft) to overcome flotation and
stability (C of G) issues. David (Powell) in Victoria recently put
his lovely almost completed "Talisman" side wheeler into the test tank
and discovered that fully loaded she sat far too low in the water
(well over the sponsons). Exactly the same thing happenned to our
VSCC Club member John Gough when he recently water tested his fully
finished "Bulldog" side paddler and had to make drastic weight
reductions and additional flotation under the sponsons to get the
model to ride at its correct waterline. I had realised this problem
when I acquired my "Director" Tug. Her C of G was so high she was
constantly in danger of turtling and had a horrible wobbling motion
that is characteristic of poorly trimmed side wheelers (even real
ones).

When Derek says he is going to "increase the ASSUMED DRAFT" he is
sending out a rather important design message.

PJ RULE 1 for RC paddlewheeler builders is BUILD THE HULL LIGHT
...especially on any paddler under 30". Even sternwheelers have this
issue with sometimes three (and more) stories of superstructure.
Far better to build too light than too heavy. Much easier to ADD
WEIGHT rather lose it (goes for humans too!!)This is VERY IMPORTANT
(Am I shouting loud enough???????)

PJ RULE 2 KEEP THE C of G LOW. Side paddlers have an exaggerated
beam over the boxes, so consequently any roll will be exaggerated.
People think side paddlers are more stable than conventional
vessels..I BEG TO DIFFER!!!! MANY side paddlers were lost at sea when
they turned over for a variety of reasons. Even the enormous Great
Eastern alarmed her passengers with her rolling tendencies. The
models are no different.

Let's never forget that , while a vessel can ride low in the water,
she can still be HIGHLY unstable because her C of G is to high. I
believe the C of G (roll axis) of a side paddler must be well below
her paddle axis. All engines, batteries, geaboxes must mounted as low
in the hull as possible.

PJ RULE 3 CONSIDER INCREASING ASSUMED DRAFT for additional flotation
and opportunity to lower C of G. Both David ("Talisman")and John
("Bulldog") were forced to do this externally AFTER they had built
their models when finding their vessels sat far too deep in the water.

PJ RULE 4 DO NOT BUILD THE SUPERSTRUCTURE TILL YOU HAVE WATER TESTED
THE HULL, MECHANICS and PADDLE SYSTEM. In this way you will be able
to see how much "bare hull" flotation you have, add weight to
calculate how much allowance you will have available for the
superstructure and everything else that rides ON and IN the boat. You
may also find that your engines are too heavy..or need extra
batteries. Do it BEFORE you build the superstructure. It will REALLY
save you so much potential heartache! I am replacing all the 1/8 ply
superstructure on my "Director" with styrene. Most of it's painted,
it's so easy to cut and glue and has correct wall thickness. (A
subject for another day ("STYRENE for OPERATING PADDLER MODELS")

PJ RULE 5 "TO FEATHER OR NOT TO FEATHER" okay..FEATHERING BLADES...
No way I'm dealing with that one right now....we all have real lives
to lead!! (and what about brass v styrene/wood paddle wheels??)

Derek also raised some other interesting issues in his email.

JAPANESE 12V DC MOTORS
"however have found that the Japanese seem a little smaller than the
rest. Due to the helical worm and wheel reduction design, the
nominal 1.0 Amp no load current draw remains near constant to say
1.1..."

hmm interesting!!!

SMOKE GENERATORS FANS
"... smoke generator in the previous Iron Prince was taken (robbed
from my daughters hair dryer) - yes 240 Vac but in series with the
heating elements I found 12 Vdc fan motor. sizing in PS Decoy
dictated something smaller so I have found all electronic shops sell
computer type fans, with the smallest being a 12 Vdc 40 x40 x 8 mm
brushless induction motor version available with a current draw of
0.08 Vdc

MAKING SMOKE
"BBQ lights & BBQ blocks <snip>, so with the occasional injection of
sump oil via a hobby 12 Vdc gear motor to a simple header in the fake
boiler is pretty simple - two BBQ lights & three BBQ blocks with 250
ml of sump oil will last for maybe one hour and will provide endless
clouds of smoke - point of interest - new hydraulic mineral oil ISO
68 = white smoke, used sump from diesel engines = greyish smoke, used
sump oil from petrol engines = black smoke" From the perspictive that
ships on the Australian waterways burnt wood and provided a greyish
smoke, I will still go for used sump oil from petrol engines = black
smoke which is more spectacular!

OMG!!! Hopefully all her fire monitors will be working!!!!!

TIN CANS
"excellent source of good construction material - same may apply to
the paddle box's in due course" David P..you listening??? your tin
can paddle "mudguards" on "Talisman".

Derek is also very inteested in DUAL ENGINE PADDLE WHEEL CONTROL
systems (OH BOY..don't we like THAT subject.. TREVOR B in the UK are
YOU listening?)

I remind you all that the drawings for my "Director" (which works SO
WELL) are in our files at (click on it)
http://groups.yahoo.com/group/Paddleducks/files/
and called 'PJ's Director something or other"

I should, however, tell you that Trevor (Bodiam) in England has
designed something FAR more "space age" .

So that's it....it's time to get on with work in the real world.

Have a GREAT DAY across the world...from Victoria BC.

Paul J

PS.. I ENCOURAGE YOU TO DISAGREE WITH ME ON ANY ISSUES I COVERED
TODAY!!

Paulrjordan

  • Guest
PS Decoy, letter from Australia
« Reply #1 on: June 13, 2005, 06:26:53 AM »
I got another thought provoking email from Derek in OZ yesterday..with
some insightful comments on my last post under this thread.

I kinda stuck my neck out a bit when I said...

> Let's never forget that , while a vessel can ride low in the water,
> she can still be HIGHLY unstable because her C of G is to high. I
> believe the C of G (roll axis) of a side paddler must be well below
> her paddle axis. All engines, batteries, geaboxes must mounted as
low in the hull as possible.
>
Derek had some very interesting anecdotes and ideas on that subject,
which caused me to rather rethink my comment, so I have asked him to
copy and post the email into the group here. Be on the lookout for
it!

PJ

Derek Warner

  • Guest
PS Decoy, letter from Australia
« Reply #2 on: June 13, 2005, 06:27:22 AM »
Hi all

I believe I have fixed the transmission clitch encountered yesterday and
have just received a return copy of my first communication back to myself as
a paddleduck

I am 50 miles south of Sydney (Australia) and thank you for being welcomed
into "paddleducks" - you may be suprised to learn how little or few marine
modelers (if not paddle modelers exist here) - currently by best checking -
just me as a paddler, so I was near ecstatic when I received PJ's first
e-mail this week

Don't want to confuse any issue here on stability etc, my experience with
the Iron Prince (of totally different proportions relative to her LOA, beam
and draft) to that of a paddle wheeler - in fact I should have clearly noted
that I had to increase the C of G with the Prince to "make her water manners
acceptable" etc

Accordingly I understand and agree in principal with PJ's comments below

With the new project PS Decoy, the total current draw should be in the order
of 1.1 > 1.3 Amps general running with the exception of the (two seconds
each ten minutes) to squirt the sump oil into the smoke boiler, an
additional 1.5 Amps (don't those little gear pump motors draw current on
viscous fuel)

Today we have the beauty of 12 V full sealed gel cells that can be
positioned thus to provide the lowest
C of G which is great, however my first 12V 7A/H gel cell (and I hope to fit
two x in Decoy) seems to loose charge without use - like overnight - and the
recharge @ 0.650 Ma takes say two hours? - which doesn't compute
mathematically to me

Are other padleducks using the same type of gel cells? - any problems? etc,
I would be most appreciative of feedback - like out her in OZ we may be the
last to know or be told etc

regards Derek

 

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