Re: [PSUBS-MAILIST] sub figures info.

[MerlinSub@t-online.de (Carsten Standfuss)]

Hi all, 
some expierence with speed trials: 

In former times on our yard we did it this way : 

Run between two buoys which were in the river on a exact known distance
of about 1852 meter (1sm). Second run in the opposite direction. 
Run 1 + run 2  divided by 2 to get a medium speed to compensate currents
and wind. Important is to hold the course straight. On a sunny windless
day. And the run  has to start many hundreds meter before you get in the
testdistance. So the boat has his maximum speed on the first bouy
allreday reached.  

Today on smaller boats we use GPS - Run the river in one direction until
the speed on the GPS stays constant for a minute. Needs about 1-3
minutes.  Then run in the opposite direction. 

Process two is much quicker and easier. Need that the GPS is prepared
that way that the speed-calculation time between two points is set to a
minimum on the gps setup. 

For a speed test on a submerged boot it will be maybe the best to tow a
small bouy (PET-bottle) behind the boat - and a small motorboat with a
GPS on boad on the surface. 

For Sgt.Peppers I can give the guys only exact figures for length and
displacement. I never meassure the speed or the rpms.. 

Very important to know is how the guys  calculate the given dive-deep. 
I mean you can give the dive deep of a sub with 300 feet or with 450
depents on the security factors choosen.. better will be to give the
calculate collapse deep. A given work deep withhout the saftey factors
or without given collapse deep says.. - nothing.

Some figures on the Busby and other books are wrong.. 

In some source you find a small sub with  2 knots on other sources with
3 knots. If you find this figures like 2, 3 or 4 knots - be careful,
that are often only a estimate figure. More accurate are maybe if you
find figures like 1,74 or 3,66 knots.. 

Another problem is the given horsepowers on motors - special on petrol
and diesels. Its not a secret here that the same motorboot here run 20
knots with a 140 hp US Petrolengine and later after a refit the same 
speed with a 120 hp european engine.. 

Any speed to horspower figures are useless if you not know how many
horsepowers the engine really has. Secondhand motors for example will
never have the nominal horsepower given by the factory. 

The Diesel on the Euronaut has nominal 190 horsepowers - but has
allready some thousand hours runtime.. 

Should I give you later the figure that the boat runs 9 knots with 190
Horsepowers ?  If later somebody use this figures  to build his own boat
and he use a new engine - Than maybe he will be very happy that his boat
runs faster..
Even new (ship) diesel can have 5% + - more or less horsepower..  
so a 100 horspower motor can have 95 or 105 horepowser. 
We build here a serie of 15 boats over four years - all the same hull
and displacemnet. Some of them run 17.5 knots other 18.6 knots.. We
never figure out why.. 

The datasheet-table makes only sence if the way the datas are made are
clear on the description.. 

I for example gets in trouble if I use figures displacemnt figures from
other submarine given in galleons.. I have to look first : Is this a
british build Sub or a US brand.. Big trouble if the sub is danish or
dutch build - the owners use normaly metric - if he give galleons.. did
the owner use the US or the GB system for the figures.. ? ;-)

Some of the Psubers use roadmiles instead of nauticalmiles.. etc.etc.. 

A good chooise is to put all the figures of the differnt subs in a
graphic table. In curves like Displacement and horsepower and speed. 
If you do this that way and you use more say 10 confirmed sources it
will be easiy vissible if somebody was a little to optimistic with his
given figures.. Or you see that a boat runs on the figures only 2 knots
instead of 3,5 it should. And later you find a nice new picture of this
boat - and they had added two manipulators - six underwaterlights and
two mirrors.. smile.. 
 
regards Carsten


Ray Keefer schrieb:
> 
> 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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