Those of you in the Chesapeake will be seeing this vessel often.

http://home.maine.rr.com/rlma/index.html#RachelCarson

I'll be spending most of October on sea trials and the delivery.

--
Roger Long

"Roger Long" wrote in news:gam781$gof$1
@registered.motzarella.org:

Those of you in the Chesapeake will be seeing this vessel often.

http://home.maine.rr.com/rlma/index.html#RachelCarson

I'll be spending most of October on sea trials and the delivery.


Nice boat! It looks like there are "fins" pointing down near the stern.
What do they do for her? Do they interfere with underway steering trying
to hold her in line?

"Larry" wrote

Nice boat! It looks like there are "fins" pointing down near the stern.
What do they do for her? Do they interfere with underway steering trying
to hold her in line?


She's a water jet boat so she doesn't have the usual rudders, props, struts,
and shafts to serve as the feathers on the back of the arrow. They will
also trap water under the stern when moving slowly on scientific station and
damp rolling. Many jet boats have them but they are usually smaller. We
made them as large as we thought we could get away with to maximize roll
damping. If they are too large, cutting them down won't be a huge job.

--
Roger Long

On Sep 15, 11:19*am, "Roger Long" wrote:
... *If they are too large, cutting them down won't be a huge job. ...

I suppose if they were too large that could result in rail walking or
something. As they are large and far outboard it seems possible that
you might get high speed instability as a result of ventilation (kind
of like what happens on a hydroplane with asymmetric venting). But,
I'm guessing that despite the jets that you aren't looking at 60 knots
or even 40 knots so probably not... What other potential problems are
you thinking about -- or are you just going to see what the sea trials
reveal?

Oh yeah, congratulations! The launch is the happiest news I've heard
in a fortnight.

-- Tom.

"Roger Long" wrote in message
...
Those of you in the Chesapeake will be seeing this vessel often.

http://home.maine.rr.com/rlma/index.html#RachelCarson

I'll be spending most of October on sea trials and the delivery.

--
Roger Long




Way to go Roger... I hope all goes well!


--
"j" ganz @@
www.sailnow.com

Roger Long wrote:
Those of you in the Chesapeake will be seeing this vessel often.

http://home.maine.rr.com/rlma/index.html#RachelCarson

I'll be spending most of October on sea trials and the delivery.

Good work there. Do those jets chop up more wildlife than conventional
wheels / rudders?

"Roger Long" wrote in
:

She's a water jet boat


Wow! Where you YOU when Sea Ray was designing my Sea Rayder jetboat!
Those fins could have kept it from spinning around when you pulled the
power. Sea Ray had no answer for this dangerous phenomenon...at least
one they'd admit to, of course.

If you pulled the power off the Sea Rayder F16XR2's 175hp Sport Jet,
with just the right-hand driver in the seat, the boat did a very
dangerous port turn, quite violently with no control, of course, as
there was no thrust.

I corrected the problem with 65# of sand bags stuffed up under the port
gunwale to correct the hull trim. Trimmed out for the single passenger,
she'd track straight and true with no power. I figured this was safer
than turning uncontrollably to port into someone's dock...or worse yet,
their yacht!

A nice secondary phenomenon I certainly enjoyed was that when a bikini-
clad honey came aboard that wanted to go to the beach, after my "trim
installation", to keep the boat in balance, she sat in the CENTER seat,
under my left arm for stability and safety.....instead of WAY OVER THERE
in the port rear seat! It was a much nicer arrangement, even without
the safety aspect...(c; Lightly rubbing her ear seemed to make the boat
faster. No theory on why....

Another 90# of sandbag ballast was installed in the very tip of the bow,
held in place with a 2x6 beam inside the forward lazerette seat. This
"damper" was very successful at stopping this light craft from jumping
up and down every time it hit a ripple, much less a wave. It also did a
wonderful job helping the boat up on plane at much lower speeds and
power as the passengers always sat in the rear seats underway with the
stuff, engine, etc., in the trunk.

Other exact-same Sea Rayders were always amazed that I could jump out of
the water and pass them equally loaded. I told the young ones it was a
special high performance tuning computer that turned my 175 into a Black
Max super engine. It wasn't....it was SANDBAGS...(c;

Sure wish I had thought about adding some stabilizing fins when I had
it. Sure wish the idiots at SEA RAY had thought about it!

Thanks for the information. The little jetboat was fine as long as you
had THRUST. It was helpless without it....and a bit
dangerous.....especially when the 3/8" fuel supply hose fell off the
5/16" hose barb, dropping the open hose into the bilge because the 3"
diameter hose clamps did nothing to stop it....flooding the hull with
enough gas that the engine INSIDE this explosive mixture would RUN on
these fumes...roughly. My phone call to Sea Ray wasn't very pleasant
and unsuitable for repeating in mixed company.

Nothing sparked before I figured out what had happened. We needn't
discuss where I pumped out the flooded bilge. THE BILGE PUMP DIDN'T
MAKE IT EXPLODE, which amazed me. Rule uses mercury
switches...explosion proof.

Sea Ray....built to the highest AYBC standards....sure....

On Mon, 15 Sep 2008 13:50:04 -0400, "Roger Long"
wrote:

Those of you in the Chesapeake will be seeing this vessel often.

http://home.maine.rr.com/rlma/index.html#RachelCarson

I'll be spending most of October on sea trials and the delivery.

Nice.

How much power? Expected cruising speed ?

wrote

I suppose if they were too large that could result in rail walking or
something. As they are large and far outboard it seems possible that
you might get high speed instability as a result of ventilation (kind
of like what happens on a hydroplane with asymmetric venting). But,
I'm guessing that despite the jets that you aren't looking at 60 knots
or even 40 knots so probably not... What other potential problems are
you thinking about -- or are you just going to see what the sea trials
reveal?

There are several aspects to this hull design that make it unsuitable for
more than 25 - 30 knots. It's primarily optimized for slow speed comfort
and maneuvering at the expense of a few percent of top end speed. The only
problem anticipated with the fins is excessive roll out in high speed turns.
Turning at high speed isn't really necessary for this boat. The speed is
for straight line transits between study area. I think it highly unlikely
that we'll have to cut down the fins.

Oh yeah, congratulations! The launch is the happiest news I've heard in a
fortnight.

Is everything OK? I appreciate the sentiment but I'd hope you'd had better
new than that recently.

-- Tom.

"Wayne.B" wrote


How much power? Expected cruising speed ?


Thanks.

Lots (I've forgotten the exact figures which are in my office. Around 1600
HP)

18-20 knots cruising. Low 20's top.

--
Roger Long