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RE: [PSUBS-MAILIST] Viewports

 
 When I have troubles like bubbles on my glass, I ask my self, what would Scooby do. ; )'
 
This reminded me of an older post in this forums archive I saved, called "Bubbles on  Dome" Below I've pasted the old post. They are talking about using a product like Rain-X to make the acrylic more hydrophilic. Perhaps polycarbonate would have less trouble in this regard.  I know I had this same problem with any aquarium that had been dry for a awhile. It didn't make a difference of whether they where glass or acrylic, fresh or saltwater tanks. I just had to get in there a wipe the bubbles off. Perhaps you can install windshield washers on the inside surface of the flooded acrylic fairing or never let those windows become dry. ; )
 

Re: [PSUBS-MAILIST] bubbles on dome

Alan,


A quick google search indicates that acrylic can be either hydrophilic (
i.e., strong affinity for water) or hydrophobic (affinity for oils) .  My
guess is that yours is hydrophobic.  You can tell by placing a drop of water
on the viewport and observing if it wants to bead up ( hydrophobic) or smear
out (hydrophilic). If its hydrophobic, then small micro imperfections in the
acrylic viewport will contain very small air bubble that act as nucleation
points for larger air bubbles.   If this is so, (just a guess) then, you
might be able to use a product sold to make rain water sheet on windshields.
This makes the surface, at least for a while, more hydrophilic. Auto supply
stores carry this type of product.  Just a thought.

Cliff



----- Original Message -----
From: "Alan Winick" <subguy33@yahoo.com>
To: <personal_submersibles@psubs.org>
Sent: Thursday, September 26, 2002 5:23 PM
Subject: [PSUBS-MAILIST] bubbles on dome


> OK guys, here's another one to chew on.
>
> I use double bow domes on Explorer. The inner dome is
> flanged to the pressure hull. Covering it is a 3/8"
> free-flooding dome. It's good for impact/scratch
> protection and also protects the inner dome from
> fingerprints and oils from the public when the sub is
> on exhibit.
>
> Anyway, I use Novus plexiglas cleaner/polish to
> maintain both domes. When I submerge, though, a
> stubborn layer of air bubbles adheres to the inner
> dome. Can't reach them to wipe off! Any ideas on how
> to prevent this? I thought of using some sort of
> surfactant, but don't want to damage the acrylic.
>
> Alan "
End Quote

Regards,
Brent Hartwig


From: bottomgun@mindspring.com
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] viewports
Date: Sun, 26 Aug 2007 15:30:44 -0400

Frank,

A compounded curve or “V” deflector should be optically clear when submerged in water.  One issue to consider is air bubbles that get stuck to the surface while submerging.  The outside can be wiped by a diver but the inside surface bubbles will be a distraction.  I have seen several submersibles with a deflector fitted including a K-350.

R/Jay

 

Jay K. Jeffries

Andros Is., Bahamas


A skimmer afloat is but a submarine, so poorly built it will not plunge…

 

 

Re: [PSUBS-MAILIST] viewports‎
From: owner-personal_submersibles@psubs.org on behalf of ShellyDalg@aol.com
Sent: Sun 8/26/07 11:36 AM
Reply-to: personal_submersibles@psubs.org
To: personal_submersibles@psubs.org
Thanks Jon. Pretty much what I had figured. Otherwise, lots of guys would have big magnifying lenses on their front ports. As I said, the port in the aquarium looks neat to the average tourist, but really distorts the view into the tank.
Another question, I want to put a '' V '' shape plexi cover in front of my main ( front ) port, to deflect water while at the surface and moving.
There will be water between the '' V '' and the flat port when submerged.
 I'm hoping that looking through the sides of the ''V'' at an angle won't distort the view, like looking through a window from the side at a 45 degree angle. This may also offer some protection from scratches on the main port. The two halves would need to be easily removable for cleaning the port and inside of the ''V''.
Either way, it doesn't affect the design of the front ballast tank to which it would be attached.
Frank D.
 

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jay K. Jeffries
Sent: Sunday, August 26, 2007 2:33 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] viewports

 

Frank & Jon,

See Stachiw’s book…it discusses virtual images due to domed ports and also how to redirect images with add on pieces of acrylic.  Remember that water and acrylic have about the same optical density so normal lens calculations would not be used…only the lens side in the air media would effect the travel of light.

 

This would be a lot of work for little gain.

R/Jay

 

Jay K. Jeffries

Andros Is., Bahamas


A skimmer afloat is but a submarine, so poorly built it will not plunge…

 

 

 

From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org] On Behalf Of Jon Wallace
Sent: Sunday, August 26, 2007 12:58 PM
To: personal_submersibles@psubs.org
Subject: RE: [PSUBS-MAILIST] viewports

 

Hi Frank,

 

I was pretty heavy into amateur astronomy in my life prior to submersibles, so have some knowledge on this.  First, the port would act like a lens only if it were shaped like a lens.  A bit thicker in the middle would not necessarily make it a lens.  It would depend upon the amount of curve and the shape of the curve.  Lenses (good ones) are specific geometric shapes such as parabola, hyperbola, etc.  If these shapes are not within specific tolerances, you get chromatic aberration, spherical aberration, and a buch of other nastyness that makes looking through them worthless. 

 

A plane disc viewport that was a little thicker in the middle would not be described as a stronger port as far as ASME PVHO is concerned.  While the port does not have to be scientifically flat (same thickness from edge to edge), you have to use the thinnest thickness to calculate the depth rating of the port, since that is it's weakest point.

 

If the shape was such that the port acted as a lens, and assuming the shape was good enough that various aberrations were not present, then yes you would have to be at the focal point in order to see anything clearly.  This is most likely not going to be a comfortable viewing angle.  It's not like the lens is going to project a bigger image of the world into the interior of the sub.  If the port were 16 inches in diameter for example, it might be like looking through an 8 inch viewport.  You will have to be some distance back, and your field of vision will significantly decrease because of that.  Unless the port is a perfect lens, as you view things further at the edges, the distortion gets worse.

 

The port would not bring more light into the sub, it would simply focus it into a smaller area.  That smaller area would be brighter since the light rays woud be concentrated, however you are sacrificing field of view for brightness.

 

Jon

 

-----Original Message-----
From: owner-personal_submersibles@psubs.org [mailto:owner-personal_submersibles@psubs.org]On Behalf Of ShellyDalg@aol.com
Sent: Sunday, August 26, 2007 12:29 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] viewports

I was welding on my hatch yesterday, and an idea came to me.

If a flat disc type view port was shaped thicker in the middle, like a lens, would it act like a magnifying glass?

What kind of distortion would be created?

How severe would that distortion be or would it  be like a car side mirror where " objects are not as near as they appear"?

Would the shape add any strength to the plexi?

Would there be a "focal point" where you had to be a certain distance from the inside surface to minimize the distortion?

Would the shape bring more light into the sub? ( like a magnifying glass )

Would the slight convex shape help with passing water over the surface?

If you were using a camera or flood light from the inside, what would that shape do to the image captured by the camera, or the light shining out from the light?

I might try a little experiment if I can find a lens that I had laying around somewhere.

There is a dome viewport in the Monterey Bay Aquarium but the distortion is pretty severe unless you have your head right inside it ( about 36 inch diameter )

I didn't take the orange sub for a ride at the convention, and I wonder what it looks like when you're in it and submerged. With your head inside the dome hatch, is the view distorted? The dome is mostly uniform in thickness, so I'm guessing it doesn't add much distortion.

Anybody have any thoughts on this? Frank D.