Skipjack 1/72

[Subculture]

Two levellers mounted at 30 degrees to the keel centreline. You need independent control of the vanes naturally, and mixing can be done in the TX or onboard. Norbert Bruggen does this on his Deepflight Aviator and Delphin models. If you have a look at page 12 of his downloadable build instructions for the Delphin you can see how the levellers are mounted.

http://modelluboot.de/Anleitungen/Anleitung_Delphin_4_10.pdf

[roedj]

Hello, 'snap-roll'.
And, Mark: you want to do stupid fast underwater turns, consider putting an angle-keeper -- sensing roll -- in the loop between stern planes and ADF2. You'll probably need a v-mixer to integrate the two sensors. Add a servo. One servo per plane so they can work as elevons. The German's have been doing this with their fast stuff for decades.

M

DM,

How exactly would that work?

To me, when the boat rolls over in a tight turn at speed you have transitioned from a cruciform type stern to an "X" tail stern. Are you saying that an ADF, if properly placed would sense this and "correct" the horizontal stabilizers to prevent the unwanted dive?

More explanation, please.

Dan

[He Who Shall Not Be Named]

Hello, 'snap-roll'.

A combination of turbulent water sheering off the hull and slamming into the outboard face of the sail and foil-roll. Foil-roll is the lateral force (lift) produced by the sail that acts to rotate the hull inboard of the turn owing to the positive angle of attack the sail takes to the relative water flow.

The faster you go the more progressive the foil roll, and you can anticipate it, which makes it easier to counter with rudder.

However, with flow separation off the hull which then hits the outboard side of the sail, that is something that will take you off guard. It's sudden and nasty.

In either case, the boat rolls into the turn, and the hard-over rudder now works as a stern plane to point the bow down. And down you go ... and it's hang onto your ass time. The only recovery is to go back-emergency, shift your rudder, full rise on the planes, hit the chicken-switch, and rattle your beads.

The real SKIPJACK's and the LA's had the performance to get into this particular bind. The other classes, not so much: the THRESHER and STURGEON class boats were slower, and the SEAWOLF and VIRGINIA class boats, though fast, are fly-by-wire and the computers won't let you get stupid at the dive-stand.

Know your speed-turn envelop! And that's what Mark is doing -- he's coming to terms with what he can, and can not do with his gray SKIPJACK. Thank God for transmitters that permit end-point adjustments.

And, Mark: you want to do stupid fast underwater turns, consider putting an angle-keeper -- sensing roll -- in the loop between stern planes and ADF2. You'll probably need a v-mixer to integrate the two sensors. Add a servo. One servo per plane so they can work as elevons. The German's have been doing this with their fast stuff for decades.

M

[greenman407]

By the way, shes running right in the ballpark where the Albacore runs. However Im taking the Albacore up a notch or two by changing to 550 motors instead of the 400s shes using now. If I wanted more reliable speed from the Scamper I would need to put more weight in her keel, as you can see her healing over on her side as you add throttle. But weight brings its own penaltys, so ill probably leave her as is. The Albacore on the other hand has counter-rotating props, which nullify the torque roll.
However, there is much to be said about reliability and control-ability. I dont always go crazy fast. The one thing that can be said about submarines. A fast submarine can go slow if you want it to, but a slow submarine cannot go fast. Id rather have an over-powered submarine that gives me more options as to how to run her that day, than to have a submarine that cant get out of its own way. For what its worth.

[greenman407]

As far as speed is concerned, you guys aint gonna believe this. That was only half throttle, if that. Before I put the scopes on, at depth, she went at least twice that fast for an instant, before I backed off, I was running out of room. In the future, as opportunity's present themselves, Ill push her harder. I lost her because I put her into a turn. Dont do that at speed. If you are going to go fast, do burst speed runs in a straight line.

[greenman407]

Yes, paints on the list as I work on the other four projects, each vying for there turn.

[HvyCGN9]

Thats one crazy video!! What throttle % was that at 110?? LOL

Cheers Bruce

PS Shouldn't she have some paint on by now??

[alad61]

Struth Mark that's running at some pace there. I love the rooster tail from the scopes when they broached. Seeing it disappear like that brought back horrible memories from a couple of years back where I didn't check my emergency gas and it was before David's sas. No amount of sweat, swearing, transmitter fiddling brought it back. It was a hard lesson learned. So now I don,t tend to go past 60% on the throttle and I triple check everything before I button a boat up. But I am very pleased your boat came back and want to play again.

[He Who Shall Not Be Named]

I still had an ACE in the hole. I hadnt used the SAS pump yet. THIS WAS IT!!! THE ACID TEST!!! COULD THE SAS LIVE UP TO ALL THE EXPECTATIONS, THE HOPES AND DREAMS AND ASPIRATIONS OF SO MANY??!!.............................after I engaged the SAS pump control lever..........................................it wasnt long before she came bobbing to the surface, as if to say.................lets do it AGAIN!

(wiping sweat from brow)

M

[crazygary]

Ahhh!!

Tranquility once again returns to the valley!!

Good call, boss!!

Way to go!

CG

[greenman407]

I still had an ACE in the hole. I hadnt used the SAS pump yet. THIS WAS IT!!! THE ACID TEST!!! COULD THE SAS LIVE UP TO ALL THE EXPECTATIONS, THE HOPES AND DREAMS AND ASPIRATIONS OF SO MANY??!!.............................after I engaged the SAS pump control lever..........................................it wasnt long before she came bobbing to the surface, as if to say.................lets do it AGAIN!

[crazygary]

Arrrgh!! Full blow! Full blow!!

Geez! I'd have had to change mah shorts after something like that!!

Pretty helpless feeling, huh!!??

CG

[greenman407]

This is the video where I lost her............................................for about a minute or so.

https://www.youtube.com/watch?v=3zWY1Vh3FEQ

https://vimeo.com/93651072

[crazygary]

Never a bad thing!!

Party on!!

CG

[greenman407]

Thanks Gary, he humors me.