Re: Unmanned test dives (long one sorry!)

[Axel Iehle <ai@augusta.cma.fr>]

Well, I've always been thinking that when it would be time for the first test, 
I would lower the sub enclosed in a strong net, and in shallow waters, just in 
case ... you know... if I can save some of those expensive inox screws...

But in the worst case, if the real big thing occurs (BADABOOM, THOOMP, 
SLURP... or whatever it may sounds!): the sub implodes and directly goes DOWN, 
there is 
two possibilities: 
- either the boat/crane combination is strong enough to withhold the new 
weight (full weight of the dead horse, huu... I mean dead sub!). But to be 
realistic I'm not sure I'll have this right boat at that right time.
- or I must design a way to lower the sub safely from a small boat.
This means having, AT ANY INSTANT of the descent, either a float that will 
hold the sub at the depth where the lowering process has been stopped, or a 
security length of rope longer than the depth of water below, in order to let 
the sub reach the bottom (but that may not be the best choice).

First solution is easy, rent the big boat, nothing to plan in advance, except 
not to have your foot trapped in the rope when the sub fails.

Second solution is less trivial:
What you want is to lower a weight SLOWLY (as you want to check meanwhile that 
all is OK and you want to know at what depth problems occured if they occur) 
into water.
In normal conditions you can make the weight of the sub very small 
(for the test, positively or negatively buoyant sub can be made slightly 
negatively buoyant).
So in theory it could be possible to stand in an inflatable boat and lower the 
sub BY HAND! (Before being flammed: I didn't say you should do that! Don't do 
that! )
But if an abnormal condition occurs (read: "BOOOMM"), then instead of holding 
a rope with a 5kg weight attached, then it'll turn into a 1-3 tons weight! 
Which is quite different. 
You can choose to let the sub sink, but this may not be the best idea as 
hitting the bottom may damage the hull while you only had to make viewports 
slightly thicker.
So I would prefer a solution that could hold the weight. The float should not 
be the (small) boat where I am for evident safety reasons.
Also the 'system' should be set up directly in the harbour as the failure may 
occur during the transportation (speaking of a small surface boat, this means 
trailing the sub behind the boat) to the test site chosen.
I haven't the solution that pleases me but I'm turning around something that 
would be made of:
1 weight, say 100kg on the bottom
1 big inflatable buoy
rope 3 times the length needed:
                        
         Boat          buoy
~~~~~~~~\_____/|~~~~~~~[__]~~~~~~~~~sea level~~~~~~~~~~
               |        |
               |       /o\
               |      /  |
               |     /   |
          rope |    /   _#__
               |   /   (_°__)-x   <- this is the sub!
               |  /                 (it's enclosed in the net
               | /                  that's why you don't recognize it!)
               o/
              _|_
_____________[___]___________________bottom____________________
             Weight

If the sub fails, the weight goes up until the sub touches the bottom,
but the boat will only have to hold the 100kg of the weight.

If there's a way to block (I haven't found how yet, perhaps cliff-climbers use 
things like that?) the rope under the buoy when the sub sinks,
and if the volume of the buoy was superior to the dry weight of the sub,
then you can avoid the sub hitting the bottom.

Also this design can't save the sub on its way to the test site.

I don't have the perfect solution but two things are sure:
1- I'm learning how to draw using keyboard characters!
2- There will be noone in the water when I'll do the test. Useless and risky.



Regards to ALL,

Axel IEHLE
		"I want my husband to pay more attention to me.
		Do you have any parfume that smells like Psubs mailing list?"


PS: I had difficulties recently to follow the whole flow of incoming mails, I 
must admit I still have some unread.
My 2 centimes (1 centimes equals 1/6th of a cent!  ;-) ) ideas about what I've 
read is that:
- we all have different ideas of what Psubs should be, and this is a chance: 
nowhere else than in Psubs list can I get to know what do other people think 
about subs, even when I disagree with them I consider I learn. Perhaps do I 
learn more when I read people I disagree with! I don't feel injured by what 
other say (I mean not enough to become aggressive), as in the end I'll build 
the sub I want with my own ideas!
- In US, people are used to protect themselves from all what they do or say.
(urban legend running here of a lady who sued (prosecute?) a microwave oven 
manufacturer because she killed her cat in trying to dry it in the oven, while 
it was not notified on the oven you shouldn't do it).
 Here (Europe, France), I won't feel concerned if I say "you may not die if 
you stop breathing for 2 hours" and some fool actually die trying to test this.
I don't want to consider a priori that people I speak to are stupid. Ray 
already wrote a clear disclaim in the Psubs site I consider this should be 
sufficient.
Explaining things as clearly as possible and answering to ALL questions 
including basic ones is the key.
- Hi Rick, Hi Phil, Hi Gary, Hi Jon (Shawl), Hi Paolo!



___________________________________________________________________
Ray Keefer wrote:

> > How does someone dive their submersible, unmanned, for testing purposes?  
> 
> Better yet. If the hull crushes how do you get the remains to the surface?
> 
>