[PSUBS-MAILIST] (no subject)
Alan James via Personal_Submersibles
personal_submersibles at psubs.org
Thu Aug 27 19:54:59 EDT 2015
As I have heard of a few instances where internal overpressure has blown the dome off,it seems wise to do as you say Alec. You would have more control near the surface toequalize pressures.Alan
From: Alec Smyth via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>
Sent: Friday, August 28, 2015 11:15 AM
Subject: Re: [PSUBS-MAILIST] (no subject)
Just two cents on this. I've actually changed my MO over time. Initially I liked diving heavy. It was an effortless way to descend, and I would get neutral with the VBT once at depth. If slightly heavy then you can use the thrusters to hover, but they will be pointing down and that ruins the visibility. I used to surface on air.
These days, I just weigh myself and passenger and I have a little table on my clipboard telling me how many buoys to load. Once you've figured the payload of the sub once, the method nails the buoyancy every time, and I mean to within 5 lbs or so. I both dive and surface on thrusters, although it is true I have to blow a little bubble in the MBTs on deep dives due to hull compression. I find thruster dives make for better control and use way less air. Thruster movement has less "momentum" than buoyancy driven motion, meaning that you can shut off the propulsive power instantly whereas, if your propulsion is coming from a tankload of air, it takes longer to vent or flood the tanks. Its also handy that the sub just hovers if you stop paying attention for any reason.
Best,
Alec
On Thu, Aug 27, 2015 at 4:13 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Alan,I agree, I need to dive slower, I have a video from yesterday with a very nice touch down. As a rule I have been going down fast and using the vertical thrusters as breaks. When I dive fast, there is a bit to much momentum built up, thats all. The video I posted shows what not to do :-)I did not put the brakes on. I will get my lead weight situation sorted out. Hank
On Thursday, August 27, 2015 1:14 PM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Hank,you said you know the bottom is soft & sink fast.I am a bit concerned as I have read of subs getting temporarily stuck in the mudon the bottom. Haven't heard of any getting permanently stuck but there is alwaysa first time. Have also heard of them picking up a lot of weight in the form of mud. Would be good if there was a quick easy lead transference system. Maybe Alec's buoy system is the simplest & easiest to use!Just clip on a number of buoys that account for the weight of the passenger.With lead it has to be placed low, so when doing dive ops it would need to goin through the hatch to the hull bottom. Alec's system has the buoys in a tube, but I am thinking that they could all haveshort cords on them, with clips to attach to various points on the top of the sub.Alan
Sent from my iPad
On 28/08/2015, at 2:27 am, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Sean,This is the big debate, VBT or no VBT. I used to like the idea of no VBT and that is the way the Nekton subs operate, just not sure eanymore. I have to admit, my regulator idea is riddled with potential problems. I am just being lazy, if I keep the sub with in 15 lbs (as per the operating manual) or less of buoyant with tanks flooded, and I pay attention, it is easy to operate. I can sink as slow as I want and hover at any depth if I take my time. I need to correct a bad habit that I have. I know the bottom is soft, so I sink fast. I need to practice what I preach and always sink as if there is a hard hazard below. Hank
On Thursday, August 27, 2015 7:26 AM, Sean T. Stevenson via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Hank, your best bet is to arrange your MBTs such thatrou they flood completely every time with no residual bubble(s), at which point you should have very slight positive buoyancy when correctly ballasted. Add a small VBT, either internally or externally in a hard tank (you could blow this with HP air instead of pumping, but would need to valve it to isolate it from ambient pressure changes), to compensate for minor crew weight differences, and compensate for the major ones by adding or removing lead.You want to avoid a situation where a depth change creates a buoyancy change, except in the sole case where you have blown your tanks to ascend.Sean
On August 27, 2015 7:13:27 AM MDT, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
| Alan,
It won't work unless there is a check valve between the second stage regulator and the ballast tank. Okay to complicated, bad idea.
Hank
From:
hank pronk via Personal_Submersibles ;
To:
Personal Submersibles General Discussion ;
Subject:
Re: [PSUBS-MAILIST] new video
Sent:
Thu, Aug 27, 2015 11:36:09 AM
| Alan,I am not sure if my idea will work . When I sink Gamma, there is an air bubble remaining in the ballast tank, the size is determined by the weight of the sub. If I have a first and second stage regulator feeding air to the ballast tank, the regulator will feed air into the ballast tank as I sink keeping the bubble the same size while I sink. Right now it is completely manual and takes practise but it works. I can use both systems ( manual or regulated) by simply turning the air supply on or off to the external regulators. With the regula! torsystem, I would not have to worry about keeping the sub at an ideal weight. Hank
On Thursday, August 27, 2015 12:03 AM, Alan via Personal_Submersibles wrote:
Thanks Hank,must be this one, the umbrella dive.https://m.youtube.com/watch?v=sflIEnkTth4Sent a reply to your post about using a second stage attached to yourballast tank, but it didn't come back to me.not sure how it would work!Alan
Sent from my iPad
On 27/08/2015, at 1:30 pm, hank pronk via Personal_Submersibles personal_submersibles at psubs.org> wrote:
made some dive
video's today, posted one on youtube under Hank Pronk
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From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>;
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org>;
Subject: Re: [PSUBS-MAILIST] new video
Sent: Thu, Aug 27, 2015 11:36:09 AM
| Alan,I am not sure if my idea will work . When I sink Gamma, there is an air bubble remaining in the ballast tank, the size is determined by the weight of the sub. If I have a first and second stage regulator feeding air to the ballast tank, the regulator will feed air into the ballast tank as I sink keeping the bubble the same size while I sink. Right now it is completely manual and takes practise but it works. I can use both systems ( manual or regulated) by simply turning the air supply on or off to the external regulators. With the regulator system, I would not have to worry about keeping the sub at an ideal weight. Hank
On Thursday, August 27, 2015 12:03 AM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
Thanks Hank,must be this one, the umbrella dive.https://m.youtube.com/watch?v=sflIEnkTth4Sent a reply to your post about using a second stage attached to yourballast tank, but it didn't come back to me.not sure how it would work!Alan
Sent from my iPad
On 27/08/2015, at 1:30 pm, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
made some dive video's today, posted one on youtube under Hank Pronk
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