Are there any circumstances where bow planes should be linked to stern?

[Slats]

Are there any circumstances where bow planes should be linked to stern planes?

I understand that bow or forward sail planes are for slight changes in depth and rear planes are used for pitch, was therefore wondering is there any circumstances in which you should link the two sets of planes (bow or sail with stern)? I have seen a few guys using this setup.

David Batagol's Collins class setup uses this arrangement. The sail planes are much further back than that of say a US nuke. (The conning tower whilst still forward is further back towards mid ships).



J

[He Who Shall Not Be Named]

Coupling stern planes to sail or bow planes typically works best only for a specific depth, speed and hull angle of attack (bubble). Any other speed-depth-pitch angle of attack combination and you start loosing it, and your commands quickly turn into 'pilot induced oscillations'.

'Surface capture' effect at the air-water interface plain (you know, where dry turns to wet ... the waters surface) is akin to the Venturi effect; where the distance between two object (waters surface and upper surfaces of the submarine) and a fluid moving between them produces a 'sucking' force that pulls the two surfaces together) A submarine at periscope depth has a lot of deck area working with the waters surface to suck the boat up and broach. Stand just one watch at the Dive trying to grab some snorkel air in a state-3 sea and you'll know all you need to know about surface capture.

The faster you go, the greater the velocity of the fluid over your deck and waters surface, the more your boat wants to broach. Coupled planes here don't serve you at all -- you want dive on the stern planes and dive on the sail/bow planes, coupling them works against you here. But at a slower speed, you hit the 'sweet spot' where the coupled control surfaces work fine together to maintain depth (though you might be at a less than zero bubble to do it).

Coupled stern and bow planes only work well in all speed-depth-pitch angle of attack situations when the planes are so far removed from the c.g. that they act to mainly effect the pitch angle of the boat, not the depth. But doing it this way deprives you of the ability to fine-tune your depth; the entire planing area of the hull, sail, and appendages are lifting surfaces -- you're flying the submarine in pitch dynamically. Hello, Mr. Holland, say Hi to Simon for us.

Sail planes are the worst to couple to the stern planes -- if the boat's center of pressure is too close to the center of lift of the sailplanes, then at a high angle of attack the c.p. may sneak forward enough to get ahead of the lifting force of the sailplanes and you get into the 'Chinese planes' effect where up is down and down is up. Happens in a submerged boat when you try to drive the damned thing too slow submerged ... a good ship's control party can adjust, new hands will get screwed up in no time flat. A situation where static stabilizing forces overcome control surface dynamic forces. To overcome Chinese planes, you need confident, independent control of those control surfaces.

Only couple the bow and stern planes if the bow planes are at the pointy front end of the boat.

Think: SEAVIEW.

David,

[Slats]

Thanks

next question - I have got some friends over here who swear by just letting the stern planes passively connect to a leveller off a 5 volt rail (no TX input), and only have TX input on the sail or bow planes - your thoughts David on this?

J

[He Who Shall Not Be Named]

Thanks

next question - I have got some friends over here who swear by just letting the stern planes passively connect to a leveller off a 5 volt rail (no TX input), and only have TX input on the sail or bow planes - your thoughts David on this?

J

In my cheap-******* days, when I only used a four-channel r/c system, that's just what I did. Sure, works fine. Good arrangement. But having active control of the stern planes lets you drive crazy when the mood hits you.

Nowadays I put the stern planes on channel-6, the rotary knob on the transmitters upper left hand position. I use it to 'trim' the boat about the pitch access and only touch it when I make a speed and/or depth change to the boat. Other than that, depth control is achieved with bow/sailplanes.

At cruising height, most pilots do the flying with the trim wheels. And that's the way we should be driving our subs once their at patrol/periscope depth and things are dialed in.

David,

[Slats]

thanks - appreciate it.

J

[KevinMc]

FWIW I use a similar configuration to what David describes on my KILO but with one additional twist - I also have a switchable mix that I can cut in and out so that when I drive the bow planes to dive or suface that command can also be mixed in to the stern planes. With the mix engaged I can rapidly achieve more radical depth changes, but for fine depth control I leave the mix disengaged and drive from the bow planes alone.

YMMV.

[He Who Shall Not Be Named]

FWIW I use a similar configuration to what David describes on my KILO but with one additional twist - I also have a switchable mix that I can cut in and out so that when I drive the bow planes to dive or suface that command can also be mixed in to the stern planes. With the mix engaged I can rapidly achieve more radical depth changes, but for fine depth control I leave the mix disengaged and drive from the bow planes alone.

YMMV.

Do you sleep with that transmitter?!....

David,

[Slats]

what does FWIW and YMMV mean?
J

[Albion]

They are FLA's

four Letter acronyms

For What its Worth
Your milleage may vary

IMHO

[Slats]

Thanks - my education expands again
J

[KevinMc]

Do you sleep with that transmitter?!....

David,

Don't be rediculous David, I would never sleep with my Tracker while I've got Futaba 9Z in the house! :wink:

[He Who Shall Not Be Named]

Don't be rediculous David, I would never sleep with my Tracker while I've got Futaba 9Z in the house! :wink:

Ah ... a multi-species relationship. You Canadians never cease to amaze and bewilder.

Perv!

David,

[Subculture]

Do you count 14mz's to go to sleep at night?

[Slats]

Andy your a sick man - I like it.