Try one of these with a standard servo and along double ended servo arm.
http://www.servocity.com/html/180o_servo_stretcher.html

A retract servo has no middle position it's designed to be either in or out.

Could the rope be for towing a dinghy or the like?

Barry......you are certainly correct in that Adelaide did or does tow a dingy/tinnie from the stern, although the rope coiled as shown in my image doesn't look long enough....
The are other images on the WEB.....& the stern appears to be tethered to other vessels from the same location
So keeping on track with the AA thread........WEB pages for the AA also show a similar rope coiled at the stern & fastened to the same rudder post fitting........Derek

gday derek,
i wopuld still have a look at servocity  ?? ,as there smallest travelling servo was 180 degrees , from memory ,they had up to 300 degree servos +you could doctor a servo , via gears ,to increase travel , similar to what graupner did in there thruster /rudders , servo imput 90 degrees ,rudder movement 200 degrees , via gears 1:2.
also you may have to only use a single pull to rudder post , to get enough travel .
to get enough rudder movement on a paddler is always a issue , mine steers Ok w 45/55 degree each side if centre , turns in about 3.5/4 boat length , but another adelaide in our club has a funny rudder set up , just to get enough rudder movement , im looking at useing a servo city servo in my next paddler , just to get enough travel .
food for thought
regards bill s

PD's........I posted the same question on Model Mayhem.....& one of the members came back with an ACTion P96 combination unit

It does appear to be near perfect for the intended [rudder] task & will not quite break the bank .......................

It may be worth considering for the AA build by echidna........Derek 
_____________________________________________________

Derek would one of these do the trick......

http://www.componentshop.co.uk/p96-servomorph.html


Dave

Hi PD's........echidna........I had previously mentioned...... "I am yet to find any welded scale link chain of approx. wire size of 1.3 mm diameter x 9 hoops per 25 mm length"
Well have found Grade 316L fusion welded link chain ...nominal 1.0 mm wire size & 9 hoops per inch  ...... & this is also pretty close to the scale sized chain for a 1:24  AA's rudder

I have extrapolated the load ratings for this chain to be ~~ 12 kg rated & an actual yield/burst of 70 Kg......which would be a factor of safety ~~6:1 on yield/burst....... for our model scales as noted....

When you have years of work & $ invested....the last thing you need is a snapped E-cheapo rudder chain with the vessel in the middle of the drink..............

Here is a dummy mock up of the chain on a plan view 1/2 axis of Adelaide............

Here is a link to the supplier.....Derek 
___________________________

-----Original Message-----
From: info@gemologica.com [mailto:info@gemologica.com]
Sent: Friday, 10 January 2014 8:56 AM
To: dlw@big.net
Subject: [ #HKP-43005-152]: G28 - Grade 316 S/S chain

Thanks for writing. The links in this are welded together. The actual wire is approximately 1MM thick.

Best Regards,
Judy
Customer Service
www.Gemologica.com

http://www.gemologica.com/images/g28_stainless_steel_chain_necklace_1.jpg

subject servo 180 deg. travel .
there is a new servo available in UK , need to look at glyn guests article in MB , in hes big gun monitor ,sorry , i lost my copy !!
there is a servo in UK w 180 degree travel ,for approx. UK$22-
sorry for lack of info
bill

Today I floated the hull of my Alexander Arbuthnot model in the bath. I used the handy method devised by Keith Harper. The unfinished hull was wrapped in thin plastic sandwich wrap.

The hull is of "bread and butter" construction, and made of radiata pine. Being bread and butter construction makes using sandwich wrap all the more appropriate.

Anyway, radiata pine has about one half the density of water, so a solid block of the stuff would float about half depth in water. My hull floated well up in the water, so Mrs Echidna supplied a jar of mayonnaise, a can of spaghetti sauce, and container of laundry detergent to load it down a bit. This cargo weighed 2.2 kgm in total. With it on board, the hull sat at what I thought was an appropriate depth, and exhibited good stability.

I read somewhere that, on the first trip of the A.A. she had a group of joy-trippers on board. There was no spark arrestor fitted, and burning cinders were raining down on the passengers. As they all moved to one side to escape the sparks, the boat listed, and "several hundred gallons of water" came over the side.

I am now confident that I can complete the boat without any fear of it being too heavy / not enough buoyancy.

 

A pic of my un-finished A.A. hull is attached.

Another pic of progress on my A.A. model.

I have just found out that my great-great grandfather and family arrived in Ipswich, Queensland, Australia on the paddle-steamer "Settler". This is the same "Settler" that started it's working life on the Murray River. Perhaps I should build a model of the Settler, but that will have to wait until the Alexander Arbuthnot is finished.

Some more pics of progress so far:

Here is a pic of the bottom of the A.A.

The planks are 3 inches thick, except for the central plank which is 4 inches thick.

This is not to be confused with the keel.

Here is a pic inside the hull of the A.A.

The keel and keelsons have been replaced this year with steel "I"-beams (they were timber before).

Note that the keel sits above the ribs.