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Re: [PSUBS-MAILIST] Boucher, RPM - sub info.
Hi.
I agree with Ray on this one, for the data to be useful it must have
a known accuracy, also we should list acceptable methods of measuring
the data.
For the velocity example (I'm sure you mean speed, velocity is a vector,
speed and direction), should we accept reading from the speed sensor
on the sub? What about currents and water flow? What if the speed
sensor on the sub is in accurate? What if the speed reading is only
over a few seconds/minutes as opposed to 30 minutes I don't think it
will give an accurate (reality accurate, not data accurate) of the
submarines performance.
I think this project of forming a database of sub stats is brilliant,
and I can't wait to finish my first sub and entry some data. I take
my hat off to all involved with this. I'm also sad to see it empty,
maybe we could get volunteers to go a round and measure peoples subs?
(A slow but sure process).
Can people edit the data a later date? For example if they took all
the static measurements and entered then them, could they come back
and update the speed, power source lifetime and the other values
which cannot easily be measured.
Thanks,
Ian.
On Fri, 01 Oct 2004 18:34:55 -0400
Erik Muller <emuller@naic.edu> wrote:
> Hi Ray,
> I absolutely agree. We had all of these things (except for suggestions
> on how to measure the parameters) in the database.
> I have found the address again, here it is:
> http://www.restorides.com/cgi-bin/psub-report.cgi
>
> Just to address each of your points:
> I periodically pointed people to it, although I did not flood the list.
>
> The database is very simple to use, and very clear, especially in the
> context of the emails I sent out (there is no other way to get to the
> site except by me telling you the address!). No detailed instructions
> necessary.
>
> The amount of data to be entered was very small. A few fundamental
> numbers that many owners would probably know off the top of their head
> (for example, the length, the width, the displacment.. etc. etc.). There
> was no insistance to enter ALL parameters which were requested, only
> those known. The parameters were fundamental enough so that descriptions
> for each parameter would be unecessary. I don't believe that anyone on
> the list needs instructions on how to measure velocity, or a description
> of the units (both imperial and metric measuring systems were available).
>
> I was also aware that people might have slightly different definitions
> of what, say 'length' is. I am not going to impose a draconian
> definition of 'length' , I am happy with something like, 'the distance
> between two guys, one with his hand on the nose, one with his hand on
> the propeller', or some such thing. I made it clear that errors in the
> measurements were expected. I don't believe that it would ever be
> necessary to impose minimum error limits or strict definitions of
> parameters is necessary for an application such as this.
>
>
> Credits go to Wyatt Greenway (and his mum!) for this fabulous page..
> dissapointingly, no entries have been made..:(
>
> Anyhow, have a look at the page if you wish, enter some numbers if you
> have them! We gotta start somewhere!
>
> EM.
>
>
>
> Ray Keefer wrote:
>
> > Hi Erik,
> >
> > > that people are just not inclined to share that level of
> > > information
> >
> > Probably more like, they really don't know. It works well enough. Why
> > bother? The work to populate the data base will be a pain, for the
> > sub owner.
> >
> > For instance if a sub moves forward. Do they care to know if its top
> > speed is 3 knots or 4 knots. Just guessing isn't good enough for the
> > database. As a results they would have to figure out a method to get a
> > reasonable number, take a trip out to a body of water, and run the
> > test just to get this one data point.
> >
> > How about figuring out prop RPM? To be valid the test has to be in the
> > water over various hull speeds. Some have the expertise to figure out
> > a method to figure that. How about those who don't? What methods do
> > they use? Who will help them? Again the owner would bear the brunt of
> > the data collection hassles.
> >
> > Personally I think this project will take a lot more then just saying,
> > hey, please fill out my cool database. There need to be some bounds
> > and controls around the parameters. For instance:
> >
> > 1. Pointers to the database. Where it was?
> >
> > 2. Instructions on how to use the database.
> >
> > 3. For each paramter in the database a definition of what that value
> > is. The units used.
> >
> > 4. A short discription on how to come up with, figure out, or measure
> > a value. Take the above forward speed question. Someone may say hey, I
> > know the distance from this dock to that jetty over there is 3 miles
> > (Well that is what he heard, it is really 3.2 statute miles.). Using
> > his wrist watch for elasped time and it was close to 3:30PM (Really
> > 3:30:45PM).
> >
> > Better would be:
> > a. Use a GPS, take a fix and write down.
> > b. Either use a wrist watch and write down hours, minutes and seconds.
> > Or use a stopwatch.
> > c. Power to distant point for at least 30 minutes in as straight a
> > line as possible.
> > d. Take GPS fix, write down, calculate elasped distance.
> > e. Stop stopwatch and write down elasped time. Or if used wrist watch
> > then record hours, minutes, seconds and calculate elasped time.
> > f. Calculate speed:
> >
> > speed = elasped distance (in nautical miles) / elasped time (in hours)
> >
> > g. Repeat steps a-f by going in opposite direction.
> > h. Average both numbers to average out drift by currents.
> >
> > Regards,
> > Ray
> >
> > Erik Muller wrote:
> >
> >> Hi Folks,
> >> I think this is question is a validation for an on-site page which
> >> can disseminate information about the various parameters of peoples
> >> currently operating subs.
> >> I tried to implement such a thing a while ago, and the information
> >> page was designed by warrens brother. It works very well, though
> >> no-one seems particularly interested in contributing to it. I'm not
> >> sure if this means that absolutely noone has operating subs (which I
> >> know is not true), or that people are just not inclined to share that
> >> level of information.
> >>
> >> I personally would LOVE to know about the physical parameters of
> >> operating machines, though I suppose I am in a minority. Is this the
> >> case? Is there anyone else who is interested in discovering some
> >> empirical correlations with parameters like displacement, resistive
> >> cross section, thrust, velocity, power.. etc etc etc.?
> >>
> >> If so, is there space to make such an information page more
> >> immediately visible on psubs?
> >> EM.
> >>
> >>
> >> Brian Cox wrote:
> >>
> >>> Hi, I have a question for Gary Boucher if he is listening! On
> >>> your sub "Vindicator" I was wondering what RPM your propeller motor
> >>> runs at? I can't remember if you go direct electric propeller or if
> >>> you said that it is a hydrolic motor? Thanks
> >>>
> >>> Brian Cox
> >>
> >>
> >>
> >>
> >>
> >>
> >>
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