Re: Exosuit

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

Hi Phil and All,

Thanks for the precisions on Exosuit.

VISION DOME:
Concerning the 'vision dome', looking at the previous drawing that was on your 
site, the looking-down interest of this design appeared clearly (BTW my wife 
said 'Ho! They build submarine-pharaons?' as the lower part of the dome 
looked, for her, like a pharao's beard!).
Having seen movies of the Newtsuit in action, I understand very well your 
description of the field of view issue.
What surprised me was the apparent 90 degrees (or so) corners in this dome,
but you confirmed that the dome has a  tear-drop shaped
connection to the hull, the 'sides' being only dome guards + screens housings.
I also suppose, even if it's not clear in your mail that this connection is 
flat: the general shape of the connection (I'm not speaking about the possibly 
conical seat of the dome) is a tear drop on a plane (2-D).

However we still have a non-spherical (no portion of sphere) vision dome.
Why should a dome/viewport be cylindrical (like the cylindrical acrylic hull 
of the SMAL) or portion of a sphere? Because of pressure acting
the same way at every position of the viewport. OK.

But why should flat viewports be circular? I can think (NO BACKGROUND on that 
issue. Just thoughts) of three reasons:
	- Pressure may generate slight movement of the port in its seat. If the 
viewport is circular: no problem it can turn or move. If it's not, there will 
be creation of a 'hard point': complex forces acting on a small area of the 
port (possibly variating along the thickness of the viewport). With glass this 
directly leads to failure. Acrylic is much more elastic but this may however 
sum up in a fatigue process that may lead after some xxx dives to failure.
	- Even without speaking of the above problem, the rigidity of the support 
(sorry this doesn't sound really good to me but I hope you'll understand what 
I mean) of the viewport doesn't act in a single direction.
e.g. in a square viewport, the regions located in the corners are suported by 
2 sides of the squared seat. And I guess one should avoid complex phenomenon 
to appear around his sub as much as possible!
	- Joints problems. O-ring is easy. []-ring is less.

These issues, if real, also concern dome viewports.
I got the feeling that Exosuit's tear-drop dome is not so much affected by the 
two last points, but could be affected by the first: the dome can't move in 
its position.

So if you followed me down to here, here is my question:

Can someone confirm or infirm the fact that viewports move in their seat and 
that hard fix should be avoided? (I should 'get' Stachiw's 100$-book on 
viewport I know. But who wants to tell this to my wife?... ;-)  )


HULL:
Phil wrote:
> Your comment
>on the spacer scallops is correct. The radical shapes are possible because
>of the small diameters and are a matter of area versus thickness. The
>cut-aways are not cosmetic ( altho' I think they look pretty cool,
>personally!) they are to reduce the volume of the limb conduits between the
>rotary joints.

I also think they look great! And that would be enough for a motivation (if no 
safety drawbacks follow): why shouldn't art or esthetic aspirations be 
included in our sub designs?...
But the engineering consequence of this is even better: reduced in-air weight.

> Do your enquries mean that we finall have pictures of the Exo
>posted - istead that that old initial drawing I did a few yeats ago??
Yes. Not enough pictures but send me one Exosuit, I promiss I'll send you back 
detailed pictures of it for your site! And you don't need to send me the suit 
complete: I already have similar fins! ;-)


Regards to All,

Axel Iehle