Anhedral effects on an X-tail

[wayne frey]

I pose a question.
If an X-tail submarine has increased manuvering due to the effects an X-tail has over a conventional stern plane setup, would anhedral (or downward angled fixed planes on some of the 688s, for example) planes on the same boat cancel or fight the increased effects the X-tail brings to the table?
On a similar line of thinking, what about some type of abbreviated anhedral stubs closer to the bow on an X-tail boat. How would that effect things?

[Guest]

I'm no expect, so this

I'm no expect, so this is a stab in the dark, perhaps they're there to counter too much sail induced roll?

Andy

[wayne frey]

That is what the anhedrals

That is what the anhedrals do, yes,resist roll. They are also on the Seawolf.
My question is more along the lines of, I do not recall seeing an X-tail boat,which can,by design, respond much quicker than the conventional tail setup, with anhedrals.
I ask over a project I am deliberating. So, there is not a known submarine out there I can think of with both features. Just checking to see if there is a reason,.Possibly the anhedrals would negate some of the X-tail advantage. Or, would it be a good add to the design?
The second part of the question would be anheadral "stubs" somewhere near the forward third of the hull. Would there be an advantage to that? It sounds plausable, and possibly a better fit to an X-tail boat?
The boat in question does have bow planes.
This should be an interesting debate of ideas and theorys in our group.
I would like to see some X-tail drivers chime in here on their thoughts also.

[Guest]

Perhaps that is because working

Perhaps that is because working X-tail boats either don't have a sail design which introduces a lot of roll (212?) or they just don't go fast enough for it to ever become a handling problem.

Another possibility would be that x-tails tend to be electronically mixed, there fore it may be easier to compensate for roll with the extra control surface area you get with an x-tail.

Andy

[wayne frey]

The Albacore in the 4th

The Albacore in the 4th design had an X-tail, with a conventional sail.
I understand snap roll was enough of a problem that a rudder on the back of the sail was tried to offset the roll of the hull on hard high-speed turns.
If you mixed the controls electronically enough to dampen what an X-tail can do for the performance, what would be the point??
I want to take full advantage of the X-tail performance. I just want to know, would anhedrals dampen the action of the X-tail?
That, and the second thought of an anhedral stubs near the front. My thought on that is the hull would try to remain stable (???), as the stern pivoted more sharply with the new configuration in the stern. Just a thought..... Maybe anhedral stubs close to the bow have been used on a submarine somewhere out there??? Anyone know?
However, I do not remember this ever coming up. It is an interesting proposal, and worthy of thoughts from out there. Surely, someone has tried this before.
I have some time to decide, but I do have almost everything laid out in front of me. If it is a bad idea, I will leave it off.

[greenman407]

I have a x-tail Albacore

I have a x-tail Albacore with a 3" Dave Merriman WTC. This thing really rips! It has way more power than any christian man should desire. Oh Well! Seriously it turns on a dime and it really moves. The only negative that I can see is that it moves up and down in the water at periscope depth about two inches at high speed as if the APC is not quite able to keep it under complete control. In this case I think that perhaps a set of bow planes would help out. What would happen if at full speed I threw it into a hard turn? I dont quite know , Ive never had the guts to try it! Perhaps in the near future I will gather the courage to try it. It will probably head straight for the bottom. What a depressing thought!

[pirate]

I don't think anherdal fins

I don't think anherdal fins on the stern would hurt the performance at all, just minimize roll. The cloeser to the tail the better. But putting them on the bow would be like adding little sails up there, probably increasing roll. since the pivot axis would be behind them I would think they'd act like big plows on the front, catching the force of the water into their sides.

[redboat219]

Re: Anhedral effects on an X-tail

what about some type of abbreviated anhedral stubs closer to the bow on an X-tail boat. How would that effect things?

Then you sub would look like a hydrofoil.
Would'nt this set up cause your bow to pitch up?

[wayne frey]

I would think there is

I would think there is no "lift" from bow mounted anhedrals. Both sides of the fin are shaped the same, so no "lift" would occur. Not unless they were mounted incorrectly (not straight).
After posting, I also thought about if it would make a difference to mount them at the center of gravity, instead of forward third.
Guys, I don't know, but I am enjoying the discussion and theory.
The Albacore driver is right. The story of the real boat said the X-tail made a big difference.
Thanks Pete, for jumping in. You may well be right, although it seems like they would dampen a turn? But, then again, in a hard turn, the inside anhedral would be in the middle of more lateral forces than forward??? At a 45 degree angle of the stabilizer, it would seem that it may not effect the dynamics much. The outside anhedral (relative to the turn), may have a little more force working on it.
But, I am not too sure about any of this.
Thought I would wake your brains

[Guest]

The Albacore in the 4th

The Albacore in the 4th design had an X-tail, with a conventional sail.
I understand snap roll was enough of a problem that a rudder on the back of the sail was tried to offset the roll of the hull on hard high-speed turns.
If you mixed the controls electronically enough to dampen what an X-tail can do for the performance, what would be the point??

The dorsal rudder was there from the original Phase I, it was deactivated in Phase II, owing to the realisation that gentler control methods were sufficient to reduce snap-roll to a minimum. The dorsal rudder was enlarged and reactivated for phase III when the X-tail was introduced. The Albacore wasn't fitted with computer control of the stern control surfaces, so I presume (perhaps incorrectly) that the vanes were mixed mechanically. This would have inhibited any fancy mixing.

It's reported that although the x-tail halved the Albacore's turning circle, it did introduce additional handling anomalies.

More on this here-

http://books.google.co.uk/books?id=OJLi ... t#PPA59,M1

[wayne frey]

Andy,
A good link.Thanks!


Andy,
A good link.Thanks!
Interesting they tried polymer spraying of the hull. The Russians did the same with the Beluga, with some success. Like the Albacore, the Russians found in testing the "body of revolution" teardrop shape was the biggest advantage.
I have decided to forgo the anhedral thoughts. But it was interesting to look at.