1/96 th alfa

[Rick Teskey]

Good Day Eh!
I just put a 1/96th ssy alfa together.
All systems work but she turns like a slug.
I have plenty of throw on the rudders.
Anyone running one of these hull could you let me know what your turning radius is.
Thank you
Rick

[spongjim]

Rick are you talking on

Rick are you talking on surface or underwater? My Akula and seawolf take alot of room to turn them if surfaced.The Alfa I bought from Tim turns alittle better and turns great underwater. The Akula is a ssy and the Seawolf and Alfa are Thor hulls.
20 foot surfaced 12 to 14 underwater.I dont know if that helps any.


Jim

[navy2000]

Just like a real sub.

Just like a real sub. I was stationed on four subs during my time in the Navy. They all have a larger turning circle on the surface than they do submerged. The reason for this is that the upper rudder is not in the water far enough to get enough water flow over the surface to help the sub make a tighter turn. In fact, A real sub while submerged at high speeds has to put limit stops on by the flick of a switch to keep the rudder from turning to far. If the rudder turns to much at high speeds the sub could go into what is called a death roll which can not be recovered from once the sub reaches acertain amount of roll and angel.

Duane

[mylo]

A "death roll" .....I wonder

A "death roll" .....I wonder who the first captain was who discovered this situation ? What kind of submerged speed are we talking about in order to get into this "death roll" situation ? I'm assuming this is a concern to later model nuke boats and not WWII era subs. Having said that, are scale r/c subs subject to this "death roll" phenomenon, which I gather is a loss of bouyancy control due to severe roll/pitch angles.

.....just some questions that I thought of.

Mylo

[Wheelerdealer]

I think a "Death Roll"

I think a "Death Roll" is when a sub keels over too much during a hard full rudder sharp turn, that the rudder effectively becomes the dive planes (which is now commanding full dive), which sends the sub to the bottom pretty sharpish... Large sails (relative to the boat) on say the Skipjack can also act as a dive plane when the sub is at extreme angles.

[wayne frey]

Actually, I think "snap roll"

Actually, I think "snap roll" is the more correct term.
American boas like the Skipjack class with a larger sail tend to do this more.
Look at it. The sail on a Skipjack is shaped like a large rudder. In a hard turn, hydrodynamic forces come into play and cause snap roll. The scall boats behave just like the real ones.
Yet another thing that caught my interest early on about Russian boats, a different approach to sail design early on.
The Alfa does have that large turning radius on the surface. Everyone noticed that at subron 5 meets. The shortest? Jeff Porteous's Blueback,which can turn on a dime.
X tail boats, all things being equal, turn quicker than conventional. That is why I want to watch on of Sneill's 212s at the regatta next month.
I think Big Dave is coming with one.
It will be the boat to watch.
Rick, if you are coming, bring a flash drive, and see me.

[mylo]

Ahhh.... and so I understand.



Ahhh.... and so I understand.

A sub with a large/flat sail is cruising along submerged. Hard rudder (say to the left) input is made which starts to yaw the boat to the left. Because of this yaw (and relatively high speed), hydrodynamic forces (water pushing) push on the opposite side of the sail to the turn, which in effect, push the sub over in the direction of the turn, with the sail acting much like a lever. Now the sub is "rolled" to the left to the point where the rudder is acting like a dive plane.....and down she goes in a hell of a hurry with the real possibility of reaching hull crush depth before control of the situation can be re established.

....hence....

"Death Roll / snap roll"

I get it. *just talking out loud here*

...and our scale r/c subs will do the same thing, except, there is much less risk of death.

Mylo

[m. munger]

Rick:

Did you make the

Rick:

Did you make the bottom rudder "full-flying"? Just hack off the skeg and adhere it to the control surface. This will give you much more surface area. Center of gravity as far forward helps too, increasing the yaw moment (I believe that's the term).

As I recall mine turned submerged in about ten to twelve feet.

Any help?

Matt

[subdude]

Matt,

Sound advice. I did the

Matt,

Sound advice. I did the same with the lower rudder on mine after the first time in the pond. Made a HUGE difference!

Jim

[substuff]

hay there Ricky! how are

hay there Ricky! how are them stock appendages working for you?

what kind of movement are you getting from them? i don't have a set of mine on hand, but i think i can get mine to through somewere around 40 degrees to either side (might be more, not sure, I'd have to go dig out a set of castings)

if you want, you can email me at OdysseySlipways@aol.com if need be.

you could always turn it into a Russian X-sub and make it a X configuration

[petn7]

Rick,

What sized WTC are

Rick,

What sized WTC are you using in your 1/96 SSY Alfa?

[tmsmalley]

Jim

...The Alfa I bought from

Jim

...The Alfa I bought from Tim turns alittle better and turns great underwater.

That Alfa has full flying rudders I got from Mike's Subworks when I put the kit together. Not scale, but it sure makes it easier to run in a smaller swimming pool.