Working ship stabilisers

General Discussion and Questions regarding TF72 and Ship Modelling
Ticonderoga
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Working ship stabilisers

Postby Ticonderoga » 06 Aug 2010 12:16

Hi All,

I have commenced building a Slava in 1/72. Interestingly they are fitted with two sets of stabilisers. I would like to have the stabilisers working.

My current plan is to link the stabilisers to the tiller arms on the rudder such that as the rudder is moved, the stabilisers are moved "in opposition" to the induced roll.

I would be very interested ot hear of any suggestions (or horror stories :shock: ) that anyone might have re such an exercise. A little birdy has told me that a certian Mr. Slater has some practical experience...... :yes:

Regards,

Andrew
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SlatsSSN
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Fleet Base: Gulf Waters
My Ship Yard: Fleet - in service and under construction

Submarines:
HMS Talent S92 - Trafalgar Class SSN.
HMS Conqueror S48 -Churchill Class SSN (Falklands 1982).

Merchants:
MS Bremen -Expedition Cruise Ship Hapag-Lloyd Cruises.
MS Christina O.
MV Titan Uranus -Mixed Cargo.
SMIT Japan Harbour Tug - (James Slater).
Vivienne Venezia - Harbour Tug.

Warships: (Under construction) -
HMS Exeter D89 -Type 42 Batch 2 (Falklands 1982).
HMS Brilliant F90 - Type 22 Batch 1 (Falklands 1982).
HMS Apollo F70 (Batch 3 Gun - Leander class Frigate).
HMS Clyde P257 - Offshore Patrol Vessel (James Slater).
HMAS Melbourne -05 FFG (2018).
HMAS Anzac -150 FFH (2020).
Location: Adelaide

Re: Working ship stabilisers

Postby SlatsSSN » 06 Aug 2010 13:20

Ticonderoga wrote:Hi All,

I have commenced building a Slava in 1/72. Interestingly they are fitted with two sets of stabilisers. I would like to have the stabilisers working.

My current plan is to link the stabilisers to the tiller arms on the rudder such that as the rudder is moved, the stabilisers are moved "in opposition" to the induced roll.

I would be very interested ot hear of any suggestions (or horror stories :shock: ) that anyone might have re such an exercise. A little birdy has told me that a certian Mr. Slater has some practical experience...... :yes:

Regards,

Andrew


Hi Andrew,
yes I do have some experience with this.
So does Craig Taylor who has them in his FFG http://docs.google.com/viewer?a=v&pid=s ... TA2YzMyNjA

The very first ship I built in 1/72 - a concept of an Anzac modified frigate that never came to be in the real world had these fitted for a while.
I have done a couple of kit commission builds in other scales that the clients wanted this feature.

First - I don't know if Craig rigs the servo that controls his stabilisers back to the rudder inputs via a Y cable. But all my applications of working stabilisers were never mechanically or electronically linked to the rudder.

I used what we call in the RC sub world a sub leveller. This is an automatic pitch controller - its a device that is both a gryo and accelerometer in the same unit. In subs this is installed between the RX and the servo controlling the rear planes. It is necessary to control the unwanted and inevitable longitudinal pitch variations that a sub is subjected to. In subs you normally have this connected to a channel that links back to the TX, so that you can override on the TX the automatic pitch control and physically drive the rear planes. BUT you can have this operating with no TX input and just hang it off a 5 volt rail. This means you don't have to tie up a channel with the device if you just want it to work autonomously.

The application of an automatic pitch control course is perfectly matched to the autonomous stabilisers in targets.

The pitch control I used came from Jim Russell in QLD at MSSA - but there are heaps on the market.

Mechanics
You can use a single servo as per Craig's setup - the control horn ends turning in opposing directions are perfect for the aileron opposite effect of the stabilisers. You could even use two servos Y cabled together and orientated in a opposite directions to get the aileron opposite effect too.
Of course you will need some water proof seals the 1/8" ones here are adequate:
http://www.caswellplating.com/models/propeller.html

Electronics
If you go the two servo route (and you might want to if the target is big at the beam), you will need to see if the pitch controller could support two servos.
I have bench tested heaps of brands and they all seem to work, but I accept NO responsibility should you do so and have a system clag on you. Remember these units are designed for subs, and the cross over use here in the surface world is really an unintended use. That said one servo will work exactly as intended, 2 check first.

Practicality
the best stabiliser idea I have is don't even bother with getting them working!

If the target has stabilisers do fit scale ones (fixed in place)- they will along with blidge keels contribute to less role, but what you want to achieve is a RC ship that has the least tenancy to roll. (Keep the weight as low and close to COG and therefore the top weight as light as possible).

Over the last 15 years or so I have fitted working sets of stabilisers to models all at the behest of clients who wanted scale realism. The realism I must say is hard to notice in the water.

Bottom line is - working stabilisers IMO only marginally improves performance, and ironically it seems to work best (have the most visible impact) in ships that are very stable as opposed to unstable. You might get a wow from on lookers with the boat being man handled on the boat stand, but who will see the benefits of these things working away in the water? Remember the laws of similitude apply - you can have scale stabilisers but you don't operate in scale water. We operate in the top 6 inches of water which is remarkable different in its fluid dynamics to even 3 feet down. (Which as an aside is why submerged scale subs can achieve similar speeds to similar sized surface vessels but with only a fraction of the RPMs). Scale stabilisers work best on the lightest most stable platforms because they face less resistance against their intended effect.

Some people argue that in theory scale stabilisers should work just as well as rudders with the same total surface area. This is just dead wrong. A scale rudder positioned aft and amongst the prop wash means its a natural pivot inducement point - which is why both boats and planes in almost all situations have the rudder located aft. Stabilisers at or around your models COG and or COR (centre of rotation) mean the effect will be diminished by their physical location. You will note that few ships have stabilisers precisely at their mid point, most are bit aft of the midpoint - some with double units are fore and aft of the mid point. Ship designers tend to do so as they tend to put the COG / COR pretty much at midships. The problem with model boats is that COG /COR is heavily influenced by how the ship is built and its weight distribution. You only need to have a ship ballasted a tad bow light and this means that your COG / COR is further aft than the mid point. If your stabilisers are in that area these will have pretty much zero effect.

For an example of an extremely light but strong build using a styrene space frame for the superstructure - have a read of my article in the Model Boats Mag April 2009 Edt for some ideas http://www.modelboats.co.uk/news/article.asp?a=4852

MS Bremen
I do plan to fit retracting stabilisers but I don't plan in going the whole hog and making these pitch up an down. To do so, whilst a sizeable job, particularly for the uninitiated, is a fairly straight forward task for the RC submariner - essentially the whole unit is just like retracting working bow planes, but opposing the pitch on either side, and adding a sub leveller, that said I don't see the value in this engineering time and or cost.

Conclusion -
IMO and experience -Don't bother with them.
Make you vessel stable around COG and keep the COG as low as possible.

Hope this helps

Best
John
Last edited by SlatsSSN on 06 Aug 2010 20:38, edited 2 times in total.
He who dies with the most toys, just dies...you can't take it with you.
Ticonderoga
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Re: Working ship stabilisers

Postby Ticonderoga » 06 Aug 2010 14:21

Thanks John, certainly a lot of food for thought.

I hear exactly what you say about COG and inherent stability. I am building a 1/96 Ticonderoga cruiser and I am paranoid about top weight.

I am still keen to give the stabiliser task a go, after all the build is for my enjoyment as much as every one else (Sounds a bit selfish I gues)

Thank you for the heads up re the seals, I was wondering about that a little. As I get closer to the decision point i will certainly let you know how we go with the concept.


Thanks again,

Andrew
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SlatsSSN
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Submarines:
HMS Talent S92 - Trafalgar Class SSN.
HMS Conqueror S48 -Churchill Class SSN (Falklands 1982).

Merchants:
MS Bremen -Expedition Cruise Ship Hapag-Lloyd Cruises.
MS Christina O.
MV Titan Uranus -Mixed Cargo.
SMIT Japan Harbour Tug - (James Slater).
Vivienne Venezia - Harbour Tug.

Warships: (Under construction) -
HMS Exeter D89 -Type 42 Batch 2 (Falklands 1982).
HMS Brilliant F90 - Type 22 Batch 1 (Falklands 1982).
HMS Apollo F70 (Batch 3 Gun - Leander class Frigate).
HMS Clyde P257 - Offshore Patrol Vessel (James Slater).
HMAS Melbourne -05 FFG (2018).
HMAS Anzac -150 FFH (2020).
Location: Adelaide

Re: Working ship stabilisers

Postby SlatsSSN » 06 Aug 2010 14:29

My pleasure Andrew.
I have a smaller Tico 1/144 on order from China - see this link
http://www.tjmodels.com.cn/productshow.asp?id=66

That too will be interesting lesson in stability.

My view is that if you are fitting stabilisers to improve stability your better off improving stability through dropping top weight and lowering the COG.


J
He who dies with the most toys, just dies...you can't take it with you.
Ticonderoga
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Building HMS Charybdis (APS Kit 1/72)
Planning Peter the Great (Kirov 1/72) to be renamed Admiral Edwin
Location: Brisbane

Re: Working ship stabilisers

Postby Ticonderoga » 06 Aug 2010 14:37

John,

I have just read your article, I enjoyed it thanks.

A bit OT but, in the article you mention ply decks with a fiberglass resin coating. I am considering 2mm ply deck for the Slava, but just using sanding sealer, undercoat and final coat. Do you have a comment re this approach?

Regards,

Andrew
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SlatsSSN
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My Ship Yard: Fleet - in service and under construction

Submarines:
HMS Talent S92 - Trafalgar Class SSN.
HMS Conqueror S48 -Churchill Class SSN (Falklands 1982).

Merchants:
MS Bremen -Expedition Cruise Ship Hapag-Lloyd Cruises.
MS Christina O.
MV Titan Uranus -Mixed Cargo.
SMIT Japan Harbour Tug - (James Slater).
Vivienne Venezia - Harbour Tug.

Warships: (Under construction) -
HMS Exeter D89 -Type 42 Batch 2 (Falklands 1982).
HMS Brilliant F90 - Type 22 Batch 1 (Falklands 1982).
HMS Apollo F70 (Batch 3 Gun - Leander class Frigate).
HMS Clyde P257 - Offshore Patrol Vessel (James Slater).
HMAS Melbourne -05 FFG (2018).
HMAS Anzac -150 FFH (2020).
Location: Adelaide

Re: Working ship stabilisers

Postby SlatsSSN » 06 Aug 2010 14:45

I have never used sanding sealer - so don't know.

My SOP now is any deck that is affixed to a GRP hull has a resin coat to seal it. If its a polyester hull - I use polyester resin - Alan Pew does the same I think?

J
He who dies with the most toys, just dies...you can't take it with you.
Ticonderoga
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Building HMS Charybdis (APS Kit 1/72)
Planning Peter the Great (Kirov 1/72) to be renamed Admiral Edwin
Location: Brisbane

Re: Working ship stabilisers

Postby Ticonderoga » 06 Aug 2010 15:08

Cheers.

Am in the office, so got to do a bit of work before knock off :crs:

Have a good weekend.
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Re: Working ship stabilisers

Postby MikeJames » 06 Aug 2010 18:35

I have seen a 1:96 model of HMS Britannia which had mechanical stabilisers. I believe it was a Deans Marine kit with the stabs a design by the builder.

They were set up with a pendulum which as the ship heeled, shifted the pendulum, which was attached via pulleys to the stabs.The further the ship heeled, the further the pendulum rocked to that side, the further it pulled the cables attached to the stabs and the further the stabs angled in the water in the opposite direction to the heel.

I asked the owner about their effectiveness and his reply was that they had some effect, which was more noticeable at higher speeds, however their relatively small size (they were in scale) meant they were less effective than the real thing.

Image

Mike
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SlatsSSN
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Fleet Base: Gulf Waters
My Ship Yard: Fleet - in service and under construction

Submarines:
HMS Talent S92 - Trafalgar Class SSN.
HMS Conqueror S48 -Churchill Class SSN (Falklands 1982).

Merchants:
MS Bremen -Expedition Cruise Ship Hapag-Lloyd Cruises.
MS Christina O.
MV Titan Uranus -Mixed Cargo.
SMIT Japan Harbour Tug - (James Slater).
Vivienne Venezia - Harbour Tug.

Warships: (Under construction) -
HMS Exeter D89 -Type 42 Batch 2 (Falklands 1982).
HMS Brilliant F90 - Type 22 Batch 1 (Falklands 1982).
HMS Apollo F70 (Batch 3 Gun - Leander class Frigate).
HMS Clyde P257 - Offshore Patrol Vessel (James Slater).
HMAS Melbourne -05 FFG (2018).
HMAS Anzac -150 FFH (2020).
Location: Adelaide

Re: Working ship stabilisers

Postby SlatsSSN » 06 Aug 2010 20:28

Yeah thanks Mike very good to mention that.
Andy, Mike raises another method that should be discussed in terms of this issue -the pendulum. Not as accurate as the automatic pitch controller, but still if your interested does have some merit.

Advantages are cost and no electronics to worry about.

Disadvantages - difficult to get setup and perfectly dialed in. Main problem is the pendulum unfortunately suffers from mass momentum build up. "The more it swings - the more it swings" the more the stabilisers keep pitching back and forth, and in some sea states the swing back to the other side can be unwarranted and quite a violent shift. You also need to factor in, if a violent shift occurs of the pendulum the resulting horizontal ballast change could in fact counteract the intended effect of the stabiliser. Another issue is, is the pendulum big enough to drive the stab fins but not too big to cause unwarranted shifts.

Then you need to factor in the unintended pendulum movement in a high speed turn. I have a US friend who used the pendulum system for stabilisers and had a mechanical link to the rudder servo - where if the rudder went hard over a mechanical linkage would break the swing of the pendulum. Was quite ingenious but modern day automatic pitch controllers are much more effective and easy to set up - they suffer none of the over swing problems that is a potential PINTA of the pendulum.

All fun - but as per Mike's post not that effective this way either.

J
He who dies with the most toys, just dies...you can't take it with you.
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SlatsSSN
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Fleet Base: Gulf Waters
My Ship Yard: Fleet - in service and under construction

Submarines:
HMS Talent S92 - Trafalgar Class SSN.
HMS Conqueror S48 -Churchill Class SSN (Falklands 1982).

Merchants:
MS Bremen -Expedition Cruise Ship Hapag-Lloyd Cruises.
MS Christina O.
MV Titan Uranus -Mixed Cargo.
SMIT Japan Harbour Tug - (James Slater).
Vivienne Venezia - Harbour Tug.

Warships: (Under construction) -
HMS Exeter D89 -Type 42 Batch 2 (Falklands 1982).
HMS Brilliant F90 - Type 22 Batch 1 (Falklands 1982).
HMS Apollo F70 (Batch 3 Gun - Leander class Frigate).
HMS Clyde P257 - Offshore Patrol Vessel (James Slater).
HMAS Melbourne -05 FFG (2018).
HMAS Anzac -150 FFH (2020).
Location: Adelaide

Re: Working ship stabilisers

Postby SlatsSSN » 06 Aug 2010 22:15

I should also explain why If i was to ever install working stabilisers again,I'd go with an automatic pitch control (APC) from a sub.

Modern APCs with their accelerometer type of gyro circuitry actually start sensing movement instantly. In lay person terms its almost like a pitch predictor. If the APC merely adjusted for pitch movement after the movement occurred any RC sub with one on board would be porpoising along with rear plane movement to compensate after the effect and then opposing compensation would occur and so forth and so on.

As the APC senses pitch movement before it magnifies into a large effect requiring large correction, most modern day RC subs with these installed, providing the boat is well trimmed to begin with, run pretty much with perfect longitudinal balance at all depths, save for when a deliberate pitch override is put in by the operator or deliberate depth change.

The same applies for the use in stabilisers. What makes an APC "the" tool for the job is that it reacts very early (predicting in nano seconds) to any sensation of roll, so the stabiliser action (if it has any effect) is on the case as the roll happens, and not after. Mechanical measures can not behave in this fashion. Further the APC can be adjusted via trim pots for sensitive and neutral position. So its very easy cf mechanical linkages to set up.

Finally if you do use an APC from a sub the orientation of the APC for stabiliser use needs to be rotated 90 degrees. APCs in subs predict and deal with longitudinal pitch oscillations, in targets its horizontal roll, so you need to turn the APC on its axis 90 degrees. Another advantage of the APC over mechanical setup is you pretty much mount the APC unit anywhere - it does not need to be along the centre line or on the COR and most units are half the size of a match box. It does need to be mounted in a perfectly flat location with the boat fully laden / ballasted.

J
He who dies with the most toys, just dies...you can't take it with you.
Ticonderoga
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Building HMS Charybdis (APS Kit 1/72)
Planning Peter the Great (Kirov 1/72) to be renamed Admiral Edwin
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Re: Working ship stabilisers

Postby Ticonderoga » 09 Aug 2010 22:07

John and Mick,

Thanks for all the info and advice, I am really impressed.

I have started cutting wood and the keel has been laid. As I get to the stabilizing issues, I will keep everyone informed.


Thanks again.

Andrew
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MikeJames
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Re: Working ship stabilisers

Postby MikeJames » 10 Aug 2010 08:18

That wouldn't be the same Ticonderoga who has been participating in a discussion elsewhere regarding the shape of the stabs on the Slava class, would it?

Mike
Ticonderoga
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My Ship Yard: On hold USS Vincennes (1/96)
Arrived HMS Clyde (1/48)
Scratch Building Varyag (Slava 1/72)
Building HMS Charybdis (APS Kit 1/72)
Planning Peter the Great (Kirov 1/72) to be renamed Admiral Edwin
Location: Brisbane

Re: Working ship stabilisers

Postby Ticonderoga » 10 Aug 2010 13:37

Hi Mike,

I think I am that person :oops: The other discussion seemed to focus on wether the stabs were retractable or not as well. In my case I will not be attempting to retract the stabs.

It is interesting to note that the Slava stabs have trailing edge tabs as well. I will not be controlling these surfaces, but they will modeled in a fixed neutral position.

Andrew

PS the build has commenced, keel is on the build board and the first few frames are ready. - slow process. :mrgreen:
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SlatsSSN
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Posts: 1285
Joined: 21 Jan 2010 10:25
Fleet Base: Gulf Waters
My Ship Yard: Fleet - in service and under construction

Submarines:
HMS Talent S92 - Trafalgar Class SSN.
HMS Conqueror S48 -Churchill Class SSN (Falklands 1982).

Merchants:
MS Bremen -Expedition Cruise Ship Hapag-Lloyd Cruises.
MS Christina O.
MV Titan Uranus -Mixed Cargo.
SMIT Japan Harbour Tug - (James Slater).
Vivienne Venezia - Harbour Tug.

Warships: (Under construction) -
HMS Exeter D89 -Type 42 Batch 2 (Falklands 1982).
HMS Brilliant F90 - Type 22 Batch 1 (Falklands 1982).
HMS Apollo F70 (Batch 3 Gun - Leander class Frigate).
HMS Clyde P257 - Offshore Patrol Vessel (James Slater).
HMAS Melbourne -05 FFG (2018).
HMAS Anzac -150 FFH (2020).
Location: Adelaide

Re: Working ship stabilisers

Postby SlatsSSN » 11 Aug 2010 17:43

Ticonderoga wrote:Hi Mike,

I think I am that person :oops: The other discussion seemed to focus on whether the stabs were retractable or not as well. In my case I will not be attempting to retract the stabs.

It is interesting to note that the Slava stabs have trailing edge tabs as well. I will not be controlling these surfaces, but they will modeled in a fixed neutral position.

Andrew

PS the build has commenced, keel is on the build board and the first few frames are ready. - slow process. :mrgreen:


Andy - does this mean (especially after the Science has been extensive laid out here for you) you want to get them working? :? :gu:
-have just looked at the Dimensions of your Slava - in short with that much tonnage and size (in scale) there is simply no way that working model scale Stabilisers will work.

Its a fools errand - a complete waste of time. You'd need to overscale the stabs by a factor of couple of hundred percent at least to see any discernible effect. Your model - your money - your time, do as you wish, but you can't beat the laws of similitude.

By all means fit them in situ as fixed non movable ones but going the extra step for no visual effect and no improvement in stability is in short nuts - in fact you might find on such a big ship that its easier not to fit them at all for other reasons. With Giuseppe Garibaldi and Silver Cloud I deliberately did not even fit them as a fixed item. Why? Logistics: I found that it was easier around the confines of my transport options to not have them fitted. Handling a big hull is at best awkward its another thing in the way of hands that are loading picking it up etc.

The bottom line is Andy - Model Boaters (including myself with my very first ship), more often than not explore the option of working stabilisers as a remedy to a perceived (during building) or real stability problem. Lesser reasons tend to be realism. If your ship is unstable (like my first ship - which was just too heavy up top), working stabilisers won't help. Fix the issue - keep the COG low build it light up top.

How do you know if you ships got stability problems?
Geoff Eastwood in 1997 showed me this. A lesson learned and now employed in EVERYTHING I have built since.

1-Get the ship in the water or test tank if you have one - fully loaded.
2-Heal it over with your hand(s) to a major list (say 45 degrees).
3- Let it go.
4-Count how many times it rocks left through right in getting back to normal. If its more than 6 times before its nothing more than a gentle slight movement (i.e. back to "normal") your ship is unstable.

Best

J
He who dies with the most toys, just dies...you can't take it with you.

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