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Aug 13, 2019, 08:09 AM
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tchalfant's Avatar
The Gato is not a fair comparison to the Type VII. The Type VII is a tiny hull.
Here is one I am currently getting back to work. This one used Big Dave's WTC and was built over a decade or two ago. It is not pretty how this deck goes on (with several large screws - you can see in picture) will be wet testing this shortly.
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Aug 13, 2019, 12:17 PM
ir3
ir3
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Thread OP

Reshaping Submarine Hull


Right on, the Gato is a lot easier to install the WTC cylinder. For the Type VII, the last of the fixes to pull the hull together are now in. The fixed spacer aft does not come apart when the hull is widened to get the WTC in. In the fore section of the hull I put in two small drilled blocks and bent a piece of wire to span the blocks when the hull is pulled together. In this way, the hull can be widened in the fore section which is absolutely necessary for installing the Merriman WTC. Once the WTC is in, the hull is squeezed together and the wire clip is installed. The gaps between the hull and deck are now acceptable. This just about does it for getting the deck to sit right.

I am thinking about keeping the WTC permanently installed and only removed for maintenance. It is a PITA to get it in and out and get the dog bones in. There is a magnetic switch to turn the power ON/OFF but I may be thinking about a water proof mechanical switch. I think I purchased some about 10 years ago with the rubber boot over the switch handle to seal it. However, installing a charging plug/jack and keeping it water tight is another problem. Any one do this or have suggestions.

Till next time,

IR3
Aug 13, 2019, 03:38 PM
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Getting the dog bones is difficult. I use a little silicone to attach one end to the prop shaft to make it a little easier. The hull flexes to get the wtc in put it is not for the faint of heart. I went to the magnetic switch because the small toggle switches are very unreliable and can't truly handle the current. Might be possible to pop the end cap off to change the battery or partially pull the wtc out to change the battery. I have found it best to pull the wtc out after running the sub to get the humidity out anyway.
Aug 13, 2019, 03:46 PM
ir3
ir3
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Thread OP

Type VII


Good advice, I will keep the mag switch in place. And taking it out after a day's sailing to dry it out is best.
Aug 14, 2019, 01:23 AM
ir3
ir3
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Thread OP

Ballasting and Trim


I need a bit more help. Is there a good discussion on ballasting and trim to be found. I have the Cabal reports but they are not quit as clear as to step by step instructions They talk about a little bit of foam here or there to get the trim right but not the initial foam installation. Also, how much weight on the bottom of the boat and how much foam above and below the water line. Also, the cabal reports do not show where is the best place to install the float controlled snorkel valve. I understand the principle; once submerged start the pump to force out the water and get the boat to rise. At some point the sail and/or snorkel breaks the surface and air is pumped from the snorkel to help evacuate the water out of the ballast tank. Where in the conning tower/sail is the best position for this. Should I mount it at deck lever or higher up. There is no clear discussion about this that I can find.

As you can see I am at the novice level when it comes to trim.
Aug 14, 2019, 05:22 AM
Latitudes vs Attitudes
Bob Gaito's Avatar
Quote:
Originally Posted by ir3
purchased some about 10 years ago with the rubber boot over the switch handle to seal it. However, installing a charging plug/jack and keeping it water tight is another problem. Any one do this or have suggestions.

Till next time,

IR3
Don't worry about being watertight-just run the wires for the charging jack into the wet area and mount it in a convenient spot -the electricity is not a problem in the water-its the corrosion just epoxy the back end of the jack , add a little silicon grease in the front and a sealing plug -will keep that at bay.

And as far as your master switch goes, I use one of these switches that you mentioned-bear in mind that the only thing watertight about it is the cap-I mask off the threads and dip the back end in Flex-Seal. Now the whole switch is waterproof and also I mount it in the wet area-five for $7 and 6 amps @125volts.
Last edited by Bob Gaito; Aug 14, 2019 at 06:38 AM.
Aug 14, 2019, 08:22 AM
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tchalfant's Avatar
Iran, you live in Southern California? We have a group of guys that meet regularly at Yorba Linda Regional Park. We just had a meet and was helping a gentleman trim his Blueback.
I trim with submerged first approach. These subs are hard to get to proper waterline, although with the Sub-Driver it seems easier because of the volume in ballast tank. When you put the boat in the water it should settle upright (if not more weight may be needed). Flood the tank, you want it to settle in the water with just the top of the tower out of the water. It needs to be level. That is a duh statement I know, but some do not do that and rely on the leveler to keep it in a good position. I need to get ready for work, will type more later.
Aug 15, 2019, 08:06 AM
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tchalfant's Avatar
Sorry for the delay.
Do not put do-dads on like railings, scopes, and guns - too easy to break off (at least for me).
I start by putting in enough weight for it to sink. You have put in 10 ounces of lead in. Get a handful of rubber bands. These will hold weight and foam temporarily until you figure out locations and volume needed. Get some foam (closed cell type - if you not sure hat I mean, let me know). Tire weights will also be needed (visit local tire guys they might give you some).
So you put your sub in the water as it is and it flops on its side - more weight is needed. Place a rubber band about center where your ballast tank is. Add tire weight to the bottom of your sub being held in place by the rubber band. If you place it in the water and it somewhat stays upright, great. You want it to almost sink however we may ave to sink before we can float. Fill ballast tank to dive, how does it sit? Level? you are a genius, a god to all mankind. More than likely not. Move the weight forward a little or aft a little to see if it sits level. You might not be able to get it level, more weight might be needed (or foam).

Let me pause here and talk about distribution of weight (and foam). The bulk of your weight should be in center of your ballast tank. I say should, but it depends on the sub. Here is where it comes to a gray area. Think of a see-saw or maybe it is called a teeter-totter, it is the beam with a seat at each end. Children or an occasional adult sit at each end and alternate pushing up or down. What happens if a tiny child sits at one end and a gorilla sits at the other end? Aside from the screaming in the park by people around, the child does not get to play much because the child's feet never get to touch the ground. Now if you could move he gorilla closer to the center then the child gets more leverage and eventually is able to touch and to begin playing with the gorilla. Each being able to push off the ground and alternate trading off one goes up the other goes down.
You are doing this with your sub. Either with weight to pull down or foam to push up. Am I making sense?
Now a couple of rules,
1. Weight low as possible.
2. Foam high as possible.
3. Bulk of weight central allows the boat to pivot easier
4. Bulk of weight at extreme ends does the opposite

When I get to foam there are a couple of rules to that as well.

Back to weight, to get it level at this point in time may or may not be possible. You are just going to have to play, but any weight at the extreme ends should not be massive (exceptions are smaller boats when you do not want them bobbing in the water like a cork). This holds true to trimming. I can use a large piece weight centrally to effect trim (gorilla) or a small piece at the extreme end (child). More later, going in for shoulder surgery......
Last edited by tchalfant; Aug 15, 2019 at 08:13 AM.
Aug 15, 2019, 08:16 AM
Registered User
More on 2.
Foam high as possible but below the waterline or you will need more ballast tank volume to raise the foam up out of the water.
=============
Exception to the rule.

Snorkel foam is above the waterline to use the weight of the foam to open the snorkel valve.
Aug 15, 2019, 10:01 AM
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tchalfant's Avatar
Ralph. Foam is used above and below waterline depending on surface or submerged trim either way rule 2 stands. More on that later. The underlining rule we are working with is metacentric height.
Aug 16, 2019, 12:04 AM
ir3
ir3
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Thread OP

Getting Closer


Thanks for the input. I am close to getting the boat wet and the procedure will be of great help. With the Velcro strap in it makes it quit difficult to get the WTC to fit easily. I removed the fixed rear brace. This kept breaking apart when I spread the top of the hull to insert the WTC. I put a pin in its place. Now I can flex the sides of the hull and slide the WTC in without much effort. I also removed the Velcro strap and built a stop to prevent the WTC from floating up. That is also removable. The WTC sits on a locating pin in the bottom of the hull so I think it will be pretty secure. The snorkel float is in thanks to some pics from Nautilus Dry Docks.

Until next time,

IR3
Aug 16, 2019, 09:27 AM
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tchalfant's Avatar
The pin to hold the sides together is a great solution.
I am still pretty foggy so I won’t be typing much today.
Older subs (like WWII subs - like your Type VII) were designed as boats that dive. Modern submarines are designed to be underwater vehicles that can surface. So there is a force in the metacentric that switches. Overly simplified the forces of gravity push down on a regular boat are countered by the lift of water. A sub uses gravity, but now water’s lift is not an issue, it is buoyancy pulling the top portion up.......at least that is the way I look at it.
Here is a really good video that explains the dynamics beater.
Naval Arch 09 - Submarines Intact Stability (11 min 49 sec)
Last edited by tchalfant; Aug 16, 2019 at 11:12 AM.
Aug 16, 2019, 11:05 AM
Registered User
The sub-driver is a pretty tight fit so I don't think the strap is needed. The plate is a good idea anyway. Like your pin idea and especially like the linkage to the rudders. I don't get a lot of rudder movement with the Merriman gear linkage in either the type 7 or type 9.
Aug 16, 2019, 12:26 PM
Latitudes vs Attitudes
Bob Gaito's Avatar
Great Video Tom-I'll have to watch it a good three more times-at least Dr Alford was animated and interesting to listen to...it puts a cause to the effect..thanks.
Latest blog entry: Mark V Navy Seal SOC
Aug 16, 2019, 06:21 PM
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tchalfant's Avatar
Bob,
I am glad you liked it. The entire collection on ship engineering is really good!
I learned a ton from it.

Peace,
Tom


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