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Re: [PSUBS-MAILIST] Pod Vent Allignment



Yes Vance 3'' is my plan but I keep wondering why not centre the pods under the keel but on the other hand I plan to Fit saddle Mbt's but still want to maintain the rear thruster configuration in the plans which on the other hand could balance somewhat the manipulator which by the way I cant wait to develop but I must stay focused as I will have to go flying at the the end of October again and my time I have to work on my sub will be limited until the end of Jan .
All the best
GlenSa                                                  ----- Original Message -----
Sent: Saturday, September 26, 2009 11:02 PM
Subject: Re: [PSUBS-MAILIST] Pod Vent Allignment

Having said that, I reread and discover that 3" is your plan. This suggests your intention to place your passenger aft, yes?
Vance


-----Original Message-----
From: glen brown <glenbrown@vodamail.co.za>
To: personal_submersibles@psubs.org
Sent: Sat, Sep 26, 2009 3:04 pm
Subject: Re: [PSUBS-MAILIST] Pod Vent Allignment

Dan H
Thanks ,I am definately going to move my Bpods aft as you have pointed out I plan on fitting a manipulator obviously the drop weights and Bpods position plays a large roll in the balance of the sub if one were to look at an overview of the K350 the buoyancy created by the C.T seems to play the greatest roll if hypothetically were able to remove it and we had just the cylindrical hull it would be simple to work out .I think with your experience with the weights you are using for trimming and the fact as you say that at this stage I don't have accurate weights to make calculations with I think 3'' is conservative but if I look at the plans the thru hulls for the drop weights should miss the ribs nicely at 3"and the Bpods thru hulls could be moved no problem .I am going to use light weight thrusters but looking at the original thrusters and there positions  opposing each other I think they wont have had a great effect(i hope)
I value your input
All the best
GlenSA
----- Original Message -----
From: Dan H.
Sent: Saturday, September 26, 2009 4:19 PM
Subject: Re: [PSUBS-MAILIST] Pod Vent Allignment

Glen,
 
If you build as the plans call for, it will work out ok.  But is you want to improve on it a bit, you can move some weight aft. That doesn't mean you have to.  My pods and drop weight is as shown on the K-350 prints.  The over all weight is pretty low as the sub is designed, so shifting twenty pound ballast weights fore and aft in the hull doesn't make a really big difference in the pitch. 
 
What I've pointed out in past postings is that most of my weight is far aft.  I have about 350 pounds far aft and another 50 pounds in the front of the hull.  I can balance the sub ok as it is but if I have a 180 pound passenger that wants to lay on the deck with their face to the forward viewport, the sub is pitched nose down, even with all the forward weights removed.  If you ever think you'll be adding a retrieval arm to the front of your sub, then you really should move something else aft.
 
If I were to guess, and this is just a guess, I'd try to move the pods and drop weights aft by two of three inches.  It's not much but it's in the right direction. 
 
Doing the weight calculations is of course the proper way but I doubt you will have accurate weights in every part of your sub available to you right now.  Maybe if you just figured the weight of the sub as it's designed now, the loose weights I use, the weight and location of the battery pods and drop weights and figure how much of a difference moving the pods aft by three inches will need to be compensated for with the loose weights in the hull, that will give you enough information. 
 
Another thing to consider,  What are you using for thrusters?  I have heavy side and rear thrusters.  If your using light weight pressure compensated thrusters, you'll need to take that into consideration.  My aft thruster weighs approximately 80 pounds and my side thrusters are about fifty pounds each. 
 
Mine sub works fine, but looking back, I would have made a little change with weight distribution. 
 
If you do move things aft, look deeply at what things you have to consider with the through hulls so you don't find that you have a hull rib in the way.
 
Hope that makes the mud a bit more clear.
 
Dan H.
----- Original Message -----
From: glen brown
Sent: Saturday, September 26, 2009 2:45 AM
Subject: Re: [PSUBS-MAILIST] Pod Vent Allignment

Hi Vance
Is there some tool or form that I am overlooking on the Pubs site for calculating the G and datum .Any input will be most welcome.
All the best
GlenSA
----- Original Message -----
Sent: Friday, September 25, 2009 12:45 PM
Subject: Re: [PSUBS-MAILIST] Pod Vent Allignment

The drop weights are designed to offset the weight of a flooded pod. They will need to be in the same position relative to the pods as the drawing calls for, no matter where they are on the fore and aft line. As to centering the pods aft, have you done your weight and balance chart? That will give you all the answers you need about negative payload issues  and needs to be done in any case to figure what goes where, and for your own peace of mind. Figuring payload is relatively simple at this juncture, so now is the time.
Vance


-----Original Message-----
From: glen brown <glenbrown@vodamail.co.za>
To: personal_submersibles@psubs.org
Sent: Fri, Sep 25, 2009 4:56 am
Subject: Re: [PSUBS-MAILIST] Pod Vent Allignment

Hi All 
I am wanting to install my drop weight and battery thru hulls on my K350 and as Dan has observed moving the pods aft will probably help with the attitude problem.The question is does one also need to move the drop weights aft ? 
I was thinking after considering Dan's remarks on the weight distribution maybe to place the drop weights and battery pods centrally. 
 
Can I place lead in the battery pods ? 
All the best 
Glen South Africa 
----- Original Message ----- From: "James Frankland" <james@guernseysubmarine.com
To: <personal_submersibles@psubs.org
Sent: Thursday, June 04, 2009 11:49 AM 
Subject: Re: [PSUBS-MAILIST] Pod Vent Allignment 
 
Hello Dan. 
 
Sorry for my late reply to yours! I'm up to my neck in wretched work at the moment so i havent been checking my mail and have not yet alligned the pods. Hoping to complete this weekend. 
 
I'm glad you couldnt find the exact location of the pods either, i thought i was being stupid or missing something. 
 
Point taken with your sub being a little forward heavy. I have a heavy steel weld in ring to add to the forward endcap that will make up the dome asseumbly, but then the dome itself which will give me a little extra bouyancy up front. 
 
I think i'll move them back "a bit", but not to much. Its a bit of a guessing game. 
 
Many thanks for your advice. 
 
Regards 
James 
 
----- Original Message ----- 
From: Dan H. [mailto:Jumachine@comcast.net
To: personal_submersibles@psubs.org 
Sent: Sun, 31 May 2009 09:41:44 -0400 
Subject: Re: [PSUBS-MAILIST] Pod Vent Allignment 
 
James, 
 
Sorry for a late reply. If you haven't already located your pods, maybe 
this will be of some use. 
 
I remember have the same question when building my sub. The location isn't 
clearly indicated. If I remember correctly, I located my battery pods by 
scaling off the drawings. I know it's now a safe thing to do, but I did 
some calculations and it looked about right. 
 
Now that I'm using my sub, I can tell you that I have about four hundred 
pounds of ballast in the aft section of the hull and about a hundred up 
forward. When I take a passenger and they lay on the deck looking forward, 
I remove my forward weights but it usually isn't enough to get level. 
Depending on the passenger weight, I could have a 5 to 7 degree forward down 
angle. Five degrees isn't that noticeable, and when scanning the bottom, 
it actually helps so no big deal. 
 
If I were to do it again, I think I would move the battery pods aft a few 
inches, as long as it didn't interfere with the hull frames and you have 
clearance for welding. That way maybe I could have a bit more forward 
movable ballast. 
 
Hope this helps, 
Dan H. 
----- Original Message ----- From: "James Frankland" <james@guernseysubmarine.com
To: <personal_submersibles@psubs.org
Sent: Tuesday, May 26, 2009 7:14 AM 
Subject: [PSUBS-MAILIST] Pod Vent Allignment 
 
Hi All. 
 
Finally i am assembling my battery pods. Can someone help me with a 
problem. 
 
The plans show the position of the vents on the pods themselves, but i cant 
see where they go on the hull, lengthways down the hull. Not exactly 
anyway. 
 
Looks like the front vent ends up between hull frames 1 and 2. but where 
exactly? Smack in the middle? That would be 7 inches from the front of the 
uncapped hull tube. 
 
Or, does it line up so the uncapped pod lines up with the uncapped hull? 
 
Also, i am only putting in 1 vent at the front. The other is replaced with 
the electrical through hulls (Alec's design). I have modified the spacing 
of the through hulls so they fall exactly between frames. easier to weld if 
they are not to close to the frames. 
 
Do you understand what i mean? Picture is here of them just placed into 
position. The front vent is in the correct place as per the plans and the 
spacing would allow the vent to to in the middle of frames 1 and 2, the 
others fall in between the other frames. 
 
http://www.guernseysubmarine.com/index_files/Page20926.htm 
 
The questions are: 
 
1 Where exactly do the pods go in relation to the hull. 
 
2 Am i ok to change the spacing of the vent\through hulls to allow them to 
fall conveniently between frames? 
 
Thanks 
James 
 
 
 
 
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