Nuclear vrs WWII sub design stability

[Timothy L]

Less than a newbie at the moment, so please forgive the ignorance behind my question. I have heard comments made that suggest World War II sub models might be much more stable and easier to operate than models based on modern nuclear subs. For example, would a 1/72 Revell Gato necessarily be any more stable than a 1/72 Virginia class sub model? If so, why? My thanks in advance for any replies.

[redboat219]

WW2 subs were basically submersible boats, more of a surface vessel. The shape of their bow are optimized for cutting throught waves. Remember reading somewhere that the assymetrical bow of the Gato o Type XXI would cause them rise up as they went faster. The modern boats with streamlined hulls are true submarines and much more stable.

[Timothy L]

Thank you.

[Albacore 569]

Both types of subs - surface optimized and underwater optimized will and both have the same dynamic stability if balanced and trimmed correctly. As all vessels everywhere do regardless of hull shape

The modern sub models, higher underwater speeds and their resulting shapes, more dynamic forces then come into play in both the real and the models. Aircraft like maneuvering is now possible.

Also, issues on some models of snap roll. But if the boat again is balanced and stable dynamically, easing off the speed or the turn rate will bring the model back to correct and be managed, as it is in the real boats. Science in action.

Both 'WW2' 'and 'Modern' types the stability should be the same, but because of the operational speeds possible or not possible inherent in each type, one is very stable 'as a tractor', and the other very stable as a 'sports car' dynamically. Snap rolls should occur in extreme maneuvers only hopefully.

Both types roll badly in heavy seas, just the nature of subs on the surface. Underwater, the differences are dramatic and fun. I doubt you will face such heavy seas issue with your models, if you are concerned about surface conditions. It you do, i'd be worried more about your radio transmitter then becoming a fatal lightening rod at that point. lol. As Merriman might say, pick a sub that gives you a hard on, and just build the damn thing, don't over think projecting ahead. The thinking will come building it
Fun!

[trout]

From an RC model perspective, I find modern subs to be much more responsive than WWII subs. As far as stable goes, I think I might need to understand more of what is meant, the Gato needs more weight and foot to get it to waterline and remain upright, but once properly trimmed it is as solid as a modern sub. Typically with the less freeboard a modern sub more stable on the surface, but again trimming is the key.

[Timothy L]

Thank you folks. You have answered my question quite well. I do appreciate your taking the time to clarify things..

[RCSubGuy]

In my experience, older boats with their control surfaces aft of the propellers, tend to be far more responsive than modern counterparts. With throttle, you get instantaneous and full force acting on the boat, whereas modern boats must rely on forward velocity through the water in order for the control surfaces to come into effect.

Absolutely, if you are running an old boat next to a modern one, you'll see about half the turning radius in the old boat, making them more advantageous in smaller bodies of water.

This is not a hard and fast rule, and there are exceptions (modern x-tail boats are a good example), but generally speaking, old boats are more responsive, new boats are faster.

[Timothy L]

That makes perfect sense - thanks Bob.

[Subculture]

A lot also depends on the subject.

Some WWII designs can get pretty close to modern boats, e.g. some midget subs and the Walther subs.

Sub designers knew what was required decades before the advent of nuclear propulsion, you only have to look at the clean lines of the Fenian Ram (circa 1881) and later Holland sub designs to see that.

[Schmitty1944]

A couple things I notice that are good and bad about old vs new Sub models:

WWII and older subs commonly have two counter rotating props placed lower on the hull which means no torque roll plus the ability to have separate control for added turning ability. Post war subs usually have one big prop right on the centre line behind the rudders and planes which means poor control at low speed and lots of torque roll at high throttle.

Old subs have a lot of freeboard when surfaced to scale which makes them harder to trim.

Post war boats with rudders above and below the waterline usually don't turn well on the surface since half of the rudder is not in the water.

Post war boats often have a rudder (or two with X-tails) that are placed very low and with no guard that makes them prone to damage if/when the models hits the bottom.

If you're interested in scale models I think the best thing is to just build what intrigues you the most for whatever reason. They all have pros and cons.

Jason

[trout]

Jason, I agree with you, build what you like.