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Re: [PSUBS-MAILIST] Boucher, RPM - sub info.

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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