What if?

[redboat219]

What if you combine a skipjack type hull with a seawolf pumpjet, a cutdown or Alfa type sail, and maybe a X-tail, wonder how she would perform?

[Subculture]

Like a Dragonshark.

[He Who Shall Not Be Named]

What if you combine a skipjack type hull with a seawolf pumpet, a cutdown or Alfa type sail, and maybe a X-tail, wonder how she would perform?

Been done, kinda. It's called the ALBACORE, phase-4. Not a proper pump-jet, but did feature the bit more efficient counter-rotating propeller (which, like a pump-jet, works to recover much of the swirl energy lost with a single propeller).

My friend, Kevin Rimrodt, and I did a Y-tail conversion of a 1/96 SKIPJACK, as well as a radically new type of sail. That was about 20 years ago -- we've yet to get it into the water.

David,

[redboat219]

My friend, Kevin Rimrodt, and I did a Y-tail conversion of a 1/96 SKIPJACK, as well as a radically new type of sail. That was about 20 years ago -- we've yet to get it into the water.

David,

A Y-tailed Skipjack?
What was radical with sail you made?

[He Who Shall Not Be Named]

A Y-tailed Skipjack?
What was radical with sail you made?

Kevin came up with the idea that too limit vortex shedding contact with the sail (which occurs near the boundary layer) -- a component of 'snap role' -- he came up with a sail design where the masts and bridge were up high in a sort of 'gondola' which connected to the hull with a very narrow, and short of cord, connecting dorsal.

David,

[Nuke Power]

Lets see a picture david

[redboat219]

Guess what I found in my old e-mails. These were given to me by Greg Sharpe in 2005. It's his scratchbuilt Russian Beluga class SSK. He used a 1/96 Skipjack hull.

[redboat219]

Been done, kinda. It's called the ALBACORE, phase-4. Not a proper pump-jet, but did feature the bit more efficient counter-rotating propeller (which, like a pump-jet, works to recover much of the swirl energy lost with a single propeller).

David,

Can you show us how did you duplicate the counter-rotating propeller mechanism?

[He Who Shall Not Be Named]

Can you show us how did you duplicate the counter-rotating propeller mechanism?

Don't have any shots of that. One motor drove the inner shaft, a second motor drove the outer shaft through a gear drive. That simple -- two un-coupled motors, each driving one of the two concentric shafts. Dirt simple. And the propellers naturally load-match to produce a zero net torque on the vehicle. Slick.

David,

[redboat219]

KISS. BTW, was the inner shaft a direct drive or geared?

[He Who Shall Not Be Named]

KISS. BTW, was the inner shaft a direct drive or geared?

The inner shaft was direct drive, so was the outer -- in effect -- the two gears used to make up to the outer concentric shaft were of the same diameter.

David,

[redboat219]

How did the model perform with the contra-rotating set-up?

[He Who Shall Not Be Named]

How did the model perform with the contra-rotating set-up?

scary fast

[Nuke Power]

Did it out perform the skipjack?

[He Who Shall Not Be Named]

Did it out perform the skipjack?

When I tried to get up to SKIPJACK speed the ALBACORE got too squirly for me to drive. No, never sustained a SKIPJACK flank bell with the ALBACORE, but it had the ass to do it.