[PSUBS-MAILIST] Personal_Submersibles Digest, Vol 56, Issue 37
Tarek Harb via Personal_Submersibles
personal_submersibles at psubs.org
Mon Feb 19 09:35:36 EST 2018
Hi,
I am not sure why the graphs I made didn’t go through. Is there anything
special I need to do?
Tim asked:
1. " Does the buoyant force of the cockpit 950kg (2,090lb) include the
occupant who will displace the air in the cockpit with a mass similar to
his volume of water?"
2. "Do you have a buoyancy trimming system planned to add and vent air in
the trim tanks and cockpit as you descend and ascend in the water column?"
3. "What source of thrusters do you have in mind?"
Answers:
1. If I understood your questions correctly, my answer is yes. The Cockpit
Buoyant force will be 950 Kg Upwards including the occupants.
2. Indeed I do have a trim tanks aside from the main Ballast tanks. I
showed this in the graphs. I will send them again if I know how to add the
graphs 3. I already ordered a Brushless 1 HP DC motor from China. I will
oil fill it, and try it. If is work out, I will be putting 5 motors. Two
for up-down and three from left-right and forward movement.
Alan said:
1. Can you get out comfortably with scuba tanks!
2. Also as you go out the diver exit the sub becomes lighter to the extent
of the weight of yourself & your dive gear.
3. If you have problems with stability when diving you could always add
syntactic foam up high & more lead down low to counteract it.
4.Have you had a look at Cliff's R300 on the projects page, as the hull
seems a similar size.
Answers:)
1. The bottom hole will be enough to get out as the Scuba Tank will not be
inside the cockpit. I have been Scuba diving for over 25 years, so that
will not be a problem for me.
2. There is a mechanism to allow the cockpit to get heavier or lighter. This
can be done by adjusting the Hole where air can be vented out at the bottom
of the pit. A decrease of 10 cm in the height of the air filled pit, will
contribute to about 100 kg of extra weight.
3. I spent too much time doing the calculations for the Stability (Nice
Excel sheet), so I do hope I will not have any problems there.
4. I just took a quick look at Cliff's R300 sub. It seem to be 1-Atm sub,
but very interesting.
Thanks for all your feedback.
On Sun, Feb 18, 2018 at 1:41 AM, via Personal_Submersibles <
personal_submersibles at psubs.org> wrote:
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> 1. Re: Dry Ambient Sub (Alan via Personal_Submersibles)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 18 Feb 2018 07:41:18 +1300
> From: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
> To: Personal Submersibles General Discussion
> <personal_submersibles at psubs.org>
> Subject: Re: [PSUBS-MAILIST] Dry Ambient Sub
> Message-ID: <E0C40860-F6E0-4BF9-A12C-8621CC31E99A at yahoo.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi Tarek,
> no diagrams came out in my email.
> I would do a full size model of what you intend & get in &
> make sure the space works. Especially if you intend to have a
> diver exit in the bottom. Can you get out comfortably with scuba
> tanks! Also as you go out the diver exit the sub becomes lighter
> to the extent of the weight of yourself & your dive gear.
> Tim's ambient sports sub has a system for adjusting this loss of
> weight by letting in more water. I am not sure how this works but
> if you adopted it you would need to allow for a volume of water to
> come in to the bottom hatchway of the sub. And of course the oposite
> is true when you re-enter.
> If you have problems with stability when diving you could always add
> syntactic foam up high & more lead down low to counteract it.
> Have you had a look at Cliff's R300 on the projects page, as the hull
> seems a similar size.
> Cheers Alan
>
>
> Sent from my iPad
>
> > On 17/02/2018, at 11:41 PM, Tarek Harb via Personal_Submersibles <
> personal_submersibles at psubs.org> wrote:
> >
> > Dear guys,
> > I would like to share with you my initial plan for the Dry Ambient sub I
> am building. I would love to hear any suggestions or comments about my
> calculations.
> >
> > The Dimensions of the Dry Cock pit is: width = 0.7 m, Length = 1.6 m,
> and Height = 0.85 m.
> > This will give a total volume of: 0.952 m3. The Cock pit will produce
> an upward Buoyant force of about 950 kg (I do understand that kg is not a
> unit of force, but I do this for sake of clarity).
> >
> > The total Mass of the Sub is around 850 Kg. So in order to make sure
> that the sub dive, its weight (or mass) has to be heavier than the Buoyant
> force produced by the
> > Cock pit, so I will add about 100 kg of Lead to compensate.
> >
> > I did the calculations of the Center of Gravity and the Center of
> Buoyancy, from which I obtained the MetaCentric height.
> > this calculations indicated that the design will keep the sub at a
> stable condition on surface and while descending, which is very important
> and critical.
> > I can provide this calculations later on if anyone interested.
> >
> > Here is a rough diagram indicating the thoughts so far
> >
> > On surface
> >
> > <image005.png>
> > <image006.png>
> >
> >
> >
> >
> > <image011.png><image012.png><image018.png>
> > FB FB Water
> level
> > <image021.png>
> > <image024.png>
> > <image025.png>
> >
> >
> >
> >
> >
> >
> > Weight of all sub = 950 Kg
> >
> > 1= Cock Pit. Volume is 0.95 m3.
> > 2= Main Ballast Tanks. Volume is 0.95 m3, this will give an upward
> force of 950 kg assuming that the density of water is 1000 Kg/m3.
> > 3. Trim Ballast Tanks
> > FB= Buoyant force = both forces will add up to cancel the weight of the
> sub.
> > At this stage all the Ballast tanks are empty and full of air.
> > <image026.png>Descending
> > FB = Buoy Force from Cock Pit
> > <image027.png>
> > <image028.png>
> >
> >
> > <image021.png><image030.png><image032.png><image034.png>
> Water level
> >
> >
> > <image018.png>
> >
> > <image037.png>
> > <image038.png>
> >
> >
> >
> >
> >
> >
> > Weight = 950 Kg
> >
> > At this stage, the Buoyant Force from the Pit + the Buoyant force from
> the Trim Tanks will equate the downward weight of the sub.
> > The Main Ballast Tanks are full as the blue color indicates. Since they
> are full, they will not contribute to give upward force.
> >
> >
> > <image039.png>UnderWater
> > FB = Buoy Force from Cock Pit
> >
> > <image040.png> Water level
> >
> > <image042.png><image044.png><image046.png>
> >
> >
> > <image018.png>
> >
> > <image037.png>
> > <image038.png>
> >
> >
> >
> >
> >
> >
> > Weight = 950 Kg
> >
> > Underwater, the Buoyant Force from the pit will equate the downward
> weight of the sub, and it will maneuver using the Motors.
> >
> > At a final note, the cockpit will have an exit hole at the bottom.
> >
> > regards
> >
> >
> >
> >
> >
> > _______________________________________________
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> > Personal_Submersibles at psubs.org
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