Para drogues in large seas

<tsmwebb@> wrote

> I admit I didn't give much thought to my reply which...

Perfectly OK, this is a newsgroup after all:)

> I still think that getting accurate wave measurements using your system
> will be hard.

It's actually fairly easy, if you have nothing else to do. It's more
practical for a researcher sailing as a guest on a vessel than as a
navigation tool.
The frame of reference is the average tops of the waves and you seek the
lowest height of eye that brings you to that reference over a representative
sample of waves. It's quite independent of the ship's frame of reference
aside from correction for any heel. Ships will usually be upright in the
trough so this correction gets lost in the noise of variation.

I'm not surprised that there is a range of correction for apparent height
ranging from 1/3 to 1/2. After all, what is wave height, Average?,
Significant?, Mean? It's a correction to a typical observed estimate which
is as highly variable as the waves. Just the fact that it has become more
widely discussed in the past couple of decades could bring the correction
down because of wider awarness by observers that the appearance is
deceiving.

Fresh water waves are different because of the lower density and other
factors. I don't know how the "square" waves typical of the lakes would
effect observations.

--
Roger Long

On Oct 23, 12:19 pm, "Roger Long" <stri...@maine.> wrote:
....
> Fresh water waves are different because of the lower density and other
> factors. ...

They claim that their results were consistent with a study they cite
using ocean data. But, the work is pretty old and as I recall we
though nomograms were pretty high powered computing devices back in
'76. I was a pretty active Lake Ontario sailor back then and my
feeling is the waves were fairly similar to waves in large shallow
ocean areas but not a perfect analogue. Anyway, I'll give your method
a try next time I'm out playing supercargo. Thanks.

-- Tom.

On Oct 23, 12:19 pm, "Roger Long" <stri...@maine.> wrote:
....
> Fresh water waves are different because of the lower density and other
> factors. ...

They claim that their results were consistent with a study they cite
using ocean data. But, the work is pretty old and as I recall we
though nomograms were pretty high powered computing devices back in
'76. I was a pretty active Lake Ontario sailor back then and my
feeling is the waves were fairly similar to waves in large shallow
ocean areas but not a perfect analogue. Anyway, I'll give your method
a try next time I'm out playing supercargo. Thanks.

-- Tom.

On Oct 24, 7:21 am, "Roger Long" <stri...@maine.> wrote:

> Speaking of attachment points, boy do I have them! The cleats on my boat
> are pretty wimpy but I have the continuous aluminum toe rails drilled for
> blocks. These are through bolted through the three quarter inch thick hull
> deck joint about every six inches ......

> Roger Long

Hello Roger:

I am about to remove my purdy teak toe rail and replace with some
fabed 3/8" Al stock just for the same reasons/use you mentioned above.
Is a foto of your toe rail online someplace?

Of special interest Id like to know how, or if, you attached your
stanchions. Im hoping to get rid of the bazillion deck penetrations
created by my guardrail stanchion attachments. ALso plan on removing
sheet fairlead tracks attafched to deck and attach blocks on the toe
rail
Bob
..

On Oct 24, 2:43 am, Skip Gundlach <SkipGundl...@> wrote:
>... Leaving yours intact for the good ideas presented, ...

My apologies, Google seems to have send the post out multiple times,
too.

> Just wondering - have you read the Pardey book? ...

No, but I read an article they made from it.

> ... So, like so many of the things I've not yet practiced (gimme a break -
> I've been at this all of 15 weeks, now, including the downtime
> addressing various system failures - we left St. Pete July 11), this
> will be something we'll work up to in more benign weather than it
> would usually warrant. ...

Of course, some kind of practice or testing is a good idea. I'd love
to run a 5 minute mile and I've read some training books by great
athletes but having practiced a bit I have a pretty good idea of where
my ability ends and fantasy begins. Likewise, the Pardeys have a lot
of talent and a lot of training and not everyone will be able to do
things the way they do. Mind you, if I were starting from scratch I
would put this kind of stuff towards the bottom of the list of stuff
to work on because the probability of getting into the kind of weather
that demands these kinds of tactics is tiny.

-- Tom.