Rubber boots for the control arms and some vaseline on the rubber O rings for extra seal. Guaranteed not to leak.
Crazy Ivan wrote:OK, let's see now:Could you please explain why you made the following statement:
"It is not advisable to try to couple the bow and stern planes together to run them both from a single channel."
Short answer: My own experiences and the sage advice of those who came before me. Longwinded technical dissertation: Well, let me see if I can articulate this clearly. As I previously posted, the bow and stern planes act in distinctly different ways, at least on the military subs we typically model, be they of the Seawolf, Gato or U-Boat type. There is a reason for this, and it starts with the center of gravity and its location.
Any forces applied to a submerged hull by the rudder or dive planes will cause it to rotate around the center of gravity. If the center is too far forward, there is extreme stability and the turning response becomes very sluggish due to an effect known as weathercocking. Too far back and the hull becomes dynamically unstable, making control difficult. Anyone who has built and flown model rockets will recall the importance of properly locating the center of gravity relative to the center of dynamic pressure.
The balance between stability and control response is generally achieved in model subs by locating the center of gravity somewhat forward of the middle of the boat, maybe in the area of around a third or more of the way back from the bow, depending on the boat. This means that the the bow planes are relatively close to the center of gravity, so they "tend to change the vertical position of the submarine on an even keel. There is a certain rotational moment, but it is counteracted to a great extent by the longer after body which acts somewhat as a stabilizing rudder, resisting angular displacement." (All quotations are from The Fleet Type Submarine training manual)
The stern planes, on the other hand, will have a relatively large rotational moment arm which will result in a change of pitch, and "their effect is much greater than that of the bow planes." In addition, when the submarine "is inclined, the hull presents planing surfaces. The resultant upward or downward thrust is added to that of the diving planes." The upshot of all this is that, in our scale, when the stern planes are used to angle the boat for diving or surfacing, the effect of the bow planes is probably negligible. The bow planes may as well be fixed in position, avoiding all the extra linkage. A lot of boats run successfully this way (although sometimes at the risk of finding your tail in the air, with the prop sucking wind because you gave her too much throttle, too soon, with too much down angle on the sternplanes!). It's happened to my Akula and other boats I've seen at the subregattas.
So then why can't the bow and stern planes be coupled together? Won't the boat still dive and surface? Absolutely! Steve's Type XXIII is a case in point. Knock yourself out. But after the novelty of going up and down wears off, it becomes a matter of control... very precise control. Many of us derive great satisfaction when we can get our boats to run steady at periscope depth, particularly with hands-off on the joy stick. If the bow planes are to be used at all, de-coupling the functions of the bow and stern planes enhances the likelyhood of success, with the boat running on an even keel.
There is one circumstance where hooking the two together might be beneficial, and that is the case of a boat like the Seaview. Dave Merriman has noted that the bow planes in this case (NOT the Sail Planes!) are far enough ahead of the center of gravity that they would impart a rotational force that would enhance the effect of the otherwise poorly performing stern planes. Maybe this is also the case with Steve's little Type XXIII, depending on how far back he located his COG. The Trumpeter Seawolf that started this discussion, at 29 inches long by 4.5 inches beam, I would expect to fall more in line with the conditions stated above.
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