[PSUBS-MAILIST] R300 Dive report - Canyon Lake, Tx

Sun Sep 6 13:58:05 EDT 2015

Cliff,I think your done herding the cats, I think you have it!  No VBT and powerful thrusters.    I think if you want to go away from the VBT, powerful thrusters are the answer.   For what it is worth, that is my conclusion after 150 plus dives with no VBT.Hank 

     On Sunday, September 6, 2015 11:28 AM, Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Hugh, if I lived in New Zealand, I would accept my boat as is and go exploring.  With the lake visibility so pour in Texas, it is kind of hard to see anything.  
 In other words the VBT should be flooded to capacity to achieve neutral buoyancy just under the surface and then minimum air can be added at depth to compensate for crush/buoyancy-change.
I see the logic in this from an air consumption perspective but this would prevent you from going from a pilot and one passenger to pilot only without adding fixed ballast.  In this case, lets say that your VBT are at say 90% filled with water and boat is neutral and now you surface, blow MBT and 200 lb passenger exits the boat.  You could not take on enough water in VBT to compensate for the lost 200 lbs so you be forced to take on fixed ballast even with this big VBT system.  So let say instead you design fixed ballast to get you neutral with say 50% water in VBT.  With a big VBT, if  you dive the boat, and have to open VBT at depth, you have to add a whole lot of fairly high pressure air to use the tank as the low pressure air in the VBT would collapse.  One way to address this would be to have the big VBT and set the neutral point at say 50% then use a PD pump on the vent leg of the VBT to adjust water level.  The key would be to find a PD pump that marine grade that does not have a lot of slip.
I think designing a new psub is a lot like herding cats.
Cliff
On Sat, Sep 5, 2015 at 7:44 PM, Hugh Fulton via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Cliff,Forever the Engineer.  Why can’t you be satisfied with just accepting it the way it is and go and explore!Ok, I understand midlife crisis and all the rest. Yes, we are all the same.  Pot calling the Kettle black.  Thanks for the update. Some interesting points with the VBT.First I was horrified that I have fallen into all the same problems.  I was quite happy on having large VBT’s and now you have spoiled my day.  Then I thought the use of the VBT is in question.  ( I know Vance is going to pounce on me and correct it all )Should the boat not be weighted so the VBT is an extension of the MBT . In other words the VBT should be flooded to capacity to achieve neutral buoyancy just under the surface and then minimum air can be added at depth to compensate for crush/buoyancy-change.  Then at surface that air in the VBT can be used to expel the water.   As you have so timely pointed out that if there is any air volume in the VBT there is going to be a lot of air used just to neutralize the air space at depth.  It is a pain that what I had allowed for in VBT capacity was to prevent the pre-dive weigh-in and adjustable ballasts.  The other bone I have to pick with you is that I always read your blogs with great interest and then go out and buy bits as close to the same, only to find by your latest admission that you are just experimenting. It is like trying to herd cats.Regards,  Hugh   From: Personal_Submersibles [mailto:personal_submersibles-bounces at psubs.org] On Behalf Of Cliff Redus via Personal_Submersibles
Sent: Sunday, 6 September 2015 2:26 a.m.
To: Personal Submersibles General Discussion
Subject: Re: [PSUBS-MAILIST] R300 Dive report - Canyon Lake, Tx Why did you decide to remove the VBT?  Was it problems with the VBT system, need for the space, or...?To use a VBT or not, that is question.  In my case, I had a hard VBT, with a volume of approximately 1.1 cu ft.  Because of the size it could only generate about 70 lbs of differential displacement.  As such I still had to add and subtract ballast to accommodate a difference in pilot weights. I found that that my VBT had a hysteresis while operating and it was sluggish in establishing neutral buoyancy.  If I got the boat neutral near the surface, then if I used the VBT at depth, there was a sudden inrush of water that would have to be blown out to get back to neutral buoyancy at depth. Adding air at depth uses a lot air and my air capacity is limited.   I used electrically activated ball valves on the vent and flood ports of the VBT.  It would take about two seconds for these valves to fully open or close.  While the VBT system worked, all of these factors caused the VBT to be less responsive than I would have liked.  Last weekend was the first time to dive my boat without the VBT and just relying on adjusting ballast prior to diving to get neutral and then using the vertical thrusters for descending, ascending and depth control.  I found with two MK 101s, I had much better depth control and the system was more responsive (until the last dive in which they failed).  Two other reasons I switched are that I used much less air and it gives much needed storage room behind the pilot.  It also simplified diving in that to ascend all I do now is flood the MBT, trim the boat longitudinally with a trim system that moves a 100 lb weight forward or aft hydraulically and then use the vertical thrusters.  To ascend, it is even easier, as now, all I have to do is use the vertical thrusters. VBTs need to be located at the CG/CB of the boat.  For a small boat like mine, this is an awkward location blocking access aft of the VBT.  Yes you can split the VBT in two but this doubles the values, tanks and plumbing. Having said all that, fish have swim bladders so we know nature likes the VBT concept.  Maybe I just need a better design for the VBT system.I have always looked at my boat as a test bed.  I change things all the time.  I have never taken the boat out configured the same way.  I will run this way for a while and see if I continue to like it as much as I do now.   If not, I will try something different.Long answer to a short question.Cliff On Fri, Sep 4, 2015 at 10:00 PM, via Personal_Submersibles <personal_submersibles at psubs.org> wrote:Cliff,Why did you decide to remove the VBT?  Was it problems with the VBT system, need for the space, or...?Thanks,Jim In a message dated 9/2/2015 7:22:37 A.M. Central Daylight Time, personal_submersibles at psubs.org writes:
Alec, Agreed, I carry a bypass cable to power up my motor in case the controller quits.  Bypass switch is a must!Hank  On Wednesday, September 2, 2015 6:04 AM, Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote: Yes, same battery.

On Tuesday, September 1, 2015, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
That's real weird Cliff, especially the fact that 2 separate unitsare playing up. The only common denominator is the batteries I suppose.Are they both drawing from the same batteries?Alan From: Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org>
To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
Sent: Wednesday, September 2, 2015 2:21 PM
Subject: Re: [PSUBS-MAILIST] R300 Dive report - Canyon Lake, Tx They shut down at about 3 PM on Sunday.  I disassembled them today expecting them to be filled with water but they were dry.  I reassembled today. I charged the batteries up last night so they were full charged this morning.   When I powered the thrusters up today, the were at ambient temperature and the controllers had been sitting all night so they were cool.  The thrusters started up misbehaving like they did when they shut down, i.e., would not spin up.  After playing with them for about 10 minutes they both came back to life a few minutes apart.  They have been running fine ever since.  Cliff   On Tue, Sep 1, 2015 at 9:00 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote: Cliff, How much time lapsed before they fixed themselves?  maybe they needed encouragement to restart because they were just on cusp of being cooled enough.Hank  On Tuesday, September 1, 2015 7:39 PM, Private via Personal_Submersibles <personal_submersibles at psubs.org> wrote: Wonderful detailed report Cliff! My theory is a thermal shutdown of the controllers as Hank suggested. Although I have no documentation on their speed controllers, the fact it fixed itself suggests that. But then on the other hand why did it take all that switching on and off to reset? This reinforces my intention to put a speed controller override into the new boat. Best, Alec 
On Sep 1, 2015, at 5:40 PM, Cliff Redus via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
I took the R300 out this weekend.  This was the first time to have it back in water since the 2013 Psub convention in Islamorada.  The objective of the dive was to evaluate some fairly significant modifications. To improve low speed maneuverability and reduce noise, I junked the jet pump and ailerons and went to four fixed MK 101 thrusters. I also junked the VBT and just add ballast to get neutral. Also I added a Garmin AIRMAR DST800 Smart Sensor to measure altitude, speed and water temperature.  It worked great.  Installed a new LED 5k light, upgraded to a new HMI, and changed the foot and joystick controls.  I also rewired the main battery bank for 36VDC rather than 120VDC and installed four MK 101 motor controllers.  I modified the aft horizontal MK-101s by adding Kort nozzles and used air to pressure compensate.  I used the same pressure reducing regulator Hugh Fulton posted about awhile back that he is using on the QSub.    The changes decreased the weight of boat by 200 lbs while the displacement remained the same.   My son, wife, a diving friend and I took the boat to Canyon Lake in Texas this Sunday.  Visibility was less than 5 ft so could not see much.  My main interest at this point was just to get into water.  After launching the boat, I did some testing to get the base line ballast both mid-ship and in the stern correct so that I could get neutral and trim after flooding the MBT.  After establishing the fixed ballast, I took the boat out to test how the horizontal thrusters work for surface maneuvering.   I was very happy with way the horizontal thrusters performed. Surface maneuverability was excellent and these motors are supper quite.  I did find that you could cavitate the props on the surface if you hit it with too much power. As before the changes, when you get up to about 4 knots, the bow wave obscures the pilots vision.   Breaking is much improved and it is now possible to rotate on the surface or in the water column. I then took the boat out for the first submerged maneuvering.  The vertical thrusters were very effective for depth control, pitch and roll control.  I found that it was much easier to get to specific depth and hold this depth using the vertical thrusters than the old way I did it with the VBT.  They worked great.  While removing the VBT simplified dive operations, it did result in loss of freeboard of about 1 inch.  This is a downside of removing the VBT as the freeboard was already quite low.  I just have to be careful when opening the hatch.  I opened and closed that hatch throughout the day and only took splash one time when a boat came by I did not see. The new Garmin AIRMAR DST800 Smart Sensor worked great. With visibility less than 5 ft, being able to know the altitude was very helpful on dives. As usual, it got darker as you descend but knowing when the bottom was coming up was nice.   On the negative side, during the last dive of the day, the vertical thrusters failed while my son was on bottom in about 27 ft of water.  He had to surface using the MBT. Why these thrusters failed is a mystery.  It was at the end of the day and I had pushed the batteries pretty hard all day along but we still had plenty of battery voltage.   My sons second attempt to surface was to put some air in the forward MBT to lift the nose and then use the aft horizontal thrusters to power to the surface.  This failed as aft horizontal thrusters were not responsive.  After surfacing with the MBT, we discovered that tree limb about 1.5” diameter had lodged in the starboard horizontal thruster between the prop and the Kort nozzle.  This explains why we lost horizontal thrust but not vertical.  After getting the boat back on the trailer, I tested the vertical thrusters.  They would barely turn even when giving them full power.  My first guess was that the air pressure compensation system failed and the thrusters were full of water.  When I got the boat back to my workshop, I disassembled both vertical thrusters and discovered they were dry. After recharging the boat, I tried the vertical thrusters again and got the same slow speed operation.  After turning them off and on for about five minutes, the starboard vertical thruster stared working correctly.  I kept switching the port vertical thruster off and on and all of a sudden, it began working correctly.  When I had the motors apart, I put a multimeter on the wires going to the brushes and found it showing 35VDC.  At this point the control signal to these motors was 2.5V so voltage to the motors should have been zero.   My guess is that the MK motor controller is acting up.  But it is strange that both the vertical controllers would fail.  Also, if it were  bad motor controllers, then why did they both start working again.  This is still a head stumper for me.  Also towards the end of the day, the OTS underwater communication stared acting up.  Base and standby diver using an OTS Guardian full face mask could hear underwater transmissions from me but I could not receive either from the diver or from the base.  The underwater commns had been working great for the previous 7 hours.   I was also having trouble about this time with the VHF radio that Alec gave me.  Again I could not receive.  When I get a chance I am going to see if the connection to the antenna got disconnected. One of the nice new features of the new HMI besides being larger and having a higher resolution, was it has built in data logging.  So after the dive it was very nice to be able to download into Excel about 50 variables logged at a one minute interval. I was able to plot these and get a detailed picture of how all the ship systems were working during the day. If anyone has any thoughts on why the vertical MK 101 thruster motors failed, or have had any negative experience with the MK101 motor controllers, I would love to hear them.  When they are working, they are great. All in all, I was very happy with the changes but have a few kinks to work out before I take her out again.  Now if I could just find some clear water to dive in, I would be a happy camper! Cliff

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