CFD from Solid Models

[LarryMcI]

Thanks to all for your thoughtful input.

I have optimized hull-fullness forward while using a common-mold approach (one mold that can be used to make both the left- and right-side panels) to reduce mold expenses. We will be cutting-away 2700 lbs of the hand-laid hulls and adding two 722 pound Extensions. LOA is increased by 19% but LWL increase is greater due to the plumb stems. Hull-slamming-conditions bouyancy calculations show a substantial improvement. Less effective-rocker was achieved by extending the keel/chines horizontally from the splice station. That station is 6" forward of the existing main (2") structural bulkhead. Anything further aft would require significant re-wiring/plumbing of the ship's electricat/fuel/H2O systems.

CFD turbulence/drag analysis is forthcoming. I agree with baeckmo that our slenderness ratio should preclude hugely adverse problems associated with the non-tangent interfaces between the new Extensions and the existing hulls, but it never hurts to quantify the proposed modifications. If the numbers come back scarey-bad, then we'll consider fairing options.

Attached is a ghost-view of the new vessel's bow with carbon fiber, honeycomb-cored, bulkheads and hat-section skin stiffeners applied. By the time all tabbing and reenforcements are applied, I expect the net change in weight to be Zero. Not bad for an 8' LOA increase, huh?

We're awaiting bids for CNC and fabrication work. Updates will follow.

Regards,

Larry McInerney

[yipster]

Originally Posted by baeckmo

The real problem is how to add volume along the wl forward, plus creating reserve buoyancy/flare up front. You may add considerable flare to the inner sides of the bows, without too much disturbance to the eye, though.

i like the cat and i've been thinking bout this too..
project cheers later added bow plates against the diving
but think big build on strakes may work as well
and may be more pleasing to the eye as baeckmo mentioned
there's also the inertia pitch, a low moment of inertia will pitch less but more quickly
a boat with a high moment of inertia will pitch slowly but more deeply

[LarryMcI]

Modifications are complete and initial sea-trial results exceeded expectations. After cutting-off portions of the original hulls and foredeck span, then installing the (2) hull-extensions ... the net weight changed by 0 (zero) pounds! Top speed increased by 2 knots. Cruising speed (2250 RPM) increased by 1.5 knots and average fuel consumption has reduced by ~10%. Everyone is happy!

More pictures of the modifications are available here:

http://www.tortugasfishing.com/ljmod2.html

Many thanks, again, to everyone for their advise and encouragement.

Larry

[yipster]

and even the yard must be happy having a longer boat
must have been some work but great job, thanks for sharing
apart from better perf and handling, boat now looks a lot nicer too

[DGreenwood]

Gotta say that is a transformation for textbooks. The visual improvement is substantial and it sounds like a real success in the performance dept. These grafts are often less than appealing but this one looks great.

Congratulations and Bravo!