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
) that anyone might have re such an exercise. A little birdy has told me that a certian Mr. Slater has some practical experience......
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