Revell Gato 1/72 - Newbie no more Part duex

[alad61]

Fair enough... "Assembler of kits I am then" ;)

Btw that a nice looking sub & certainly makes the skipjack enticing... but the tipping scales are leaning toward the Gato so Trout I will bookmark your thread as part of my reasearch data.

[trout]

David,

According to Merriam-Webster (not Merriman)

Build
transitive verb
1
: to form by ordering and uniting materials by gradual means into a composite whole : construct

2
: to cause to be constructed

3
: to develop according to a systematic plan, by a definite process, or on a particular base

4
: increase, enlarge



Here are examples used by Merriam-Webster:
Examples of BUILD

• The bridge was built in the 1890s.
• The planes were built in Germany.
• The organization helps build houses for poor families.
• A family of birds has built a nest on our roof.
• She started building a fire in the fireplace.
• He built a model airplane from a kit. (emphasis mine)

[He Who Shall Not Be Named]

Arrrgh!.........

[trout]

alad61, all of us are here to help!

Earlier I mentioned how easy it was to replace the pushrod seal and I wanted to show some of the steps. The seal that I am replacing is the one that is really tight - the rudder pushrod seal.

As David had mentioned, just push the seal out with a spare piece of rod. I had to push from both directions, but it comes loose.

I had soldered my threaded end for the Kli-cons (which I saw a posting by David you could just CA them in place) and needed to remove it.

Put a generous amout of RTV silicon on.

Push the seal in until it is flush or slightly out with the WTC end cap.

Clean up, let it set up, install pushrod, and pressure test your hull.



Now it is time to set up my sub for ballast and trimming. I wanted to be smart and pre-build my ballast so I could add as I needed.
I got some potters clay (the kind they put in a kiln) and built a simple wood frame with the edges at the height, short of the distance, to the bottom of the wtc. Rolled the clay into the frame and laid the ballast pattern on top, Using an xacto knife, cut around the pattern.

Removed all the areas that I wanted filled with lead. Anywhere there is clay, that was an area that water would come in from.

Melted the lead (time to insert disclaimer - lead is know to be dangerous to your health, use at your own risk - I am not recommending you use lead and will not be held liable for any injury or harm to yourself or others or to property damaged by molten lead, handling lead, and usage of lead) If you are worried use BBs or Zinc. Poured the lead into the mold and presto, I have ballast........or DO I?

It de-molded great, but I used a flat bottom mold and my hull is curved. Which if I thought about it first, I should have seen that. The outside edges meet the hull before the center of the ballast keeping it raised too high. I would have to further modify the casting to fit the hull and not inhibit the WTC from mounting properly.


Try number two.......
I laid a strip of clay in the hull pressing it into all the recesses.
Trimmed the edges to keep the mold height right and pushed out all the flood holes. Also cut out channels on each hole to allow a path for water to come in once the ballast is installed.

Then let the clay dry. Hoping it would not stick because if it can go wrong (I seem to attract the go wrong) it will. The clay came out, for the most part O.K. - a couple of narrow pieces broke off.
Then I purchased come craft plaster. This was not like standard plaster of paris, soft and gouges easily, it was more like the harder plaster used in special effects (a dental plaster or Die Plaster) or in jewelry (casting investment). Mixed the batch a little thicker and ladled it into the mold frame, then I placed the hardened clay pieces in. Made sure that they were oriented the correct way (keel facing down). Let it set until it firmed up. Using a putty knife carefully leveled everything to the top of the mold frame.

I had some left over plaster and two pieces of ballast castings. These two pieces were from the extreme bow end and extreme aft end. I laid these two into the leftover plaster. The instructions say it can be microwaved to speed the hardening process once the initial set occurred. Hmmmm, I’ll try that with the extra molded pieces (not the core pieces). About 40 seconds on defrost, I heard a pop and a raining sound....that is not good quickly went through my head. I stopped the microwave and opened the door. One corner of the mold blew out. The microwave door was plastered with, well, plaster. Being the quick thinker, I better clean this up before my wife discovers what I did.
The mold was still salvageable, but I think I will just let the molds dry on their own. The instructions said it can take 24 hours to fully cure. I do not have 24 hours.
Being too impatient I turned the oven on to 195 degrees fahrenheit and I placed the main mold in there. Once the oven reached 195, I turned off the oven, left the door closed, and worked on other things. I came back later and everything had hardened. The next question is how do I get the clay out....since it is potters clay, adding water will get the clay soft again. I placed the cooled mold into a bucket of water and let it sit for a while. When I came back to it, the clay had softened. Using a old toothbrush and a toothpick cleaned out the clay.



Then it was time to melt the lead. And I had a thought......Scary isn’t it? Why am I doing all this? I do not even know if I need all these and I am delaying the inevitable, getting the sub in water (and in the back of my head I can hear the voice of David saying "get her in the water doggone it" Well not the doggone it part). I have enough ballast from my first attempt to use. Then I can pour only the pieces I need. The master tub is too small (who designed these tubs?) and the guest one might work.
Did the pre-sail checklist. I filled the tub and put my Gato in. The excitement was high. My son came in and wanted to help. I set the sub gently into the water, holding it as water filled the free space, and let her go. She promptly, unceremoniously, flopped over on her side like a dead fish in an aquarium. I was not expecting that, but knew that is why I was making the ballast.
Released air out of her tank and lovingly held her upright, the aft end sank and the bow was high. Placing a piece of lead (from the first batch of ballast- 140grams) on the deck towards the bow, it began to level out, but it quickly was stopped by the curve of the tub. RATS...this tub will not work.
So, my son and I played (err - verified the procedure) with filling the tank using SNORT and emptying her and repeating the process. I will need to build a tank to trim the Gato. We also played with the propulsion. There is a TON of power in these props! I am so excited to get to the point of sea trials!
Once we were done playing/testing, checked the wtc and it was wet where it is supposed to be and dry where it is supposed to be dry! YESSSS!

[trout]

David,
To keep a stable sub, we are concerned about a decent metacentric distance. When trimming out the sub, would placing the weight at the extreme ends also help with stability. In my mind if all the weight is close to the center, it would seem to rock easier. Can you help explain the different thoughts on trimming a sub?
Peace,
Tom

[Reckless]

I asked the EXACT same question... thus was the reply

Naw. You're doing fine. No call for name-calling .... yet.

The vertical relationship of the fixed lead ballast weight and buoyant foam (center of gravity low, center of buoyancy high) produces the vertical forces that when displaced longitudinally or laterally (pitch and/or roll off-set from zero), translates to a torque in the appropriate direction and amplitude to force the boat back to a state of static stability (zero pitch and zero roll angle).

When the vertical weight line is shared by the vertical buoyancy line, the boat is statically stable. When these two lines are off-set longitudinally or laterally, or a combination of the two, then the boat is unstable and the two forces will work to right the boat, thus placing themselves once again along the same vertical path -- the state of static stability.

One job of the buoyant foam is to produce the additional buoyant force needed to cancel out the weight of the boat when the ballast tank is flooded. Neutral (an ideal, never achieved in the real world) buoyancy -- submerged trim -- is achieved when the boats overall weight is equal to the weight of the water it displaces.

Displacement of water (buoyant force) occurs only when an object is in the water. If foam is placed above the surfaced waterline (where it will no longer displace water), then that foam will no longer contribute its share of buoyancy to the boat. If you do put a lot of your foam above the waterline, then the ballast tank has to be increased in floodible capacity, that additional amount equal to the displacement of water lost when the foam is pushed up into the air. The more foam you keep below the surfaced waterline, the smaller your ballast tank can be and still do the job of getting the boats structure high enough so that the waterline falls at the scale location for the type model you're representing.

(R/C Models representing WW-2 submarines have notoriously high freeboards -- that's a lot of stuff to push up into the wild-blue! A big ass ballast tank is required, or you build all above waterline portions of the submarine as light as possible. Nothing looks more toy-like than a GATO sitting in surface trim, with decks nearly awash, because of an undersized ballast tank that is more hardware than floodible volume! That's the big reason I favor the gas or semi-aspirated ballast sub-system -- you get a great deal of floodible volume without giving up valuable real-estate to bags, solenoids, exotic pumps, jacking screws, pistons, Klystron relays, flux-capacitors, spin-dizzies, limit switches, speed controllers, water sensors, and other ballast sub-system support gizmo's).

Static stability about the pitch and roll axis is the job of the keel weight and foam. You play with the foam -- its amount, longitudinal and lateral placement -- to establish submerged near neutral buoyancy as well as the boats zero pitch and roll angle when at rest.

Always trim the boat first for submerged 'near neutral' trim. Once that's done, you then trim the boat for surfaced trim. You'll find the waterline too low initially (that's a good thing), and you start relocating some of the foam vertically, to a position above the submarines designed waterline. I'll yank you through the process when you get to it, non-Qual.

[trout]

Thanks Reckless, I think......So, that means yes it does help in stability? David, please help clarify for me!

The Gato will be trimmed!!!! I bought this until a more permanent solution is found, plus my son will enjoy it once it has served its purpose!

http://www.target.com/p/Intex-Blue-120in-Swim-Center/-/A-13800360?reco=Rec%7Cpdp%7C13800360%7CClickCP%7Citem_page.adjacency&lnk=Rec%7Cpdp%7CClickCP%7Citem_page.adjacency

[He Who Shall Not Be Named]

Thanks Reckless, I think......So, that means yes it does help in stability? David, please help clarify for me!

The Gato will be trimmed!!!! I bought this until a more permanent solution is found, plus my son will enjoy it once it has served its purpose!

http://www.target.com/p/Intex-Blue-1...page.adjacency

Yes.............

David

[trout]

I like simple answers like that! LOL! Thank you.
Next question. 140 grams (about 10 oz) does not seem like enough to keep her upright. would I distribute extra weight and use foam to get her to submerged trim?
Thank you again for all that you do David!

[He Who Shall Not Be Named]

Yes.........

David

[Reckless]

Thanks Reckless, I think......So, that means yes it does help in stability? David, please help clarify for me!

The Gato will be trimmed!!!! I bought this until a more permanent solution is found, plus my son will enjoy it once it has served its purpose!

http://www.target.com/p/Intex-Blue-1...page.adjacency

basically the short and dry of the whole technical explination Dave gave me is : the farther from center your foam is from your lead weight... the more it will want to rock and sway .....

[trout]

Thank you Reckless!

[trout]

Worked on some final trim issues and came up with a nifty way for quick disconnect of my bow dive planes. I had two issues with the bow plane pushrod. One it bowed and would lose the transfer of power and two how to connect them. The 1st idea was to use the magnets I got out of Apple laptop, but I found that they would slide or disconnect. Mainly because they are connecting on the horizontal plane allowing slippage to occur. Thought I would create a way to hold the magnets together using a clip, but that was just getting cumbersome and not keeping it simple. I placed this on the back burner for awhile but still kept mulling the problem over in my head. Came up with a way to connect them, again using magnets, and this time it stays put. Pictures will be coming. I also played with a quick disconnect for a snort system that I have. David has copies of the two different quick disconnects for his thoughts and feedback.

Tested the seals again for water tightness and all was good.

Inflated the mini-pool and filled it with water...in the garage..... and began testing....my son's Rain Gutter Boat for Cub Scouts. Yep, that was the priority. However, last night after Sam went to bed, I began the trimming of the Gato! With lots of rubber bands and just under 1 lb of lead I began the process. The first order was to stop the laying over and playing dead. I added most of the lead to stop that. Placing some in the front and majority in the middle. When I filled the ballast tank the Gato gracefully sunk - upright!. Good start, Then I added foam to either side in the middle and some in the stern. This lifted her up to decks awash. I placed the remaining weight on the deck and it got to the point where if I put the last chunk on, she would sink. Took it all out and the Gato is drying.

Questions.

I am going to have to shape the pieces to fit the contour of the hull. This will reduce the buoyancy. How do you figure out what to add to compensate? What is the best way to install foam?

The lead is affixed with RTV I am supposing.

Then I will repeat this process for more refining of the trim (this time I will take pictures).

Any suggestions?

There was some water in the battery compartment that must have come from the tire valve. I thought it was tight, but I have not put any silicon on it, and did not crank the stem down hard. should I? do you put silicon on the valve stem gasket?

[alad61]

Technically I'm still a newbie but with my seaview I used rtv to hold the lead and foam. I used lead sheet cut into strips ad because it's a little maleable I could gently press the strips to the contour of the hull bottom. For testing I used little blobs of blue-tac to hold them in place. I didn't add any foam till I was happy with the leads trim. I also kept the lead to a minimum around the cog then ballanced it out forward and aft from there. The foam is in small pieces as well, which was easier to handle and I reckon would help with any shape issues on your hull too.

[trout]

Alec,
Thank you. RTV it is! I am beginning to really like RTV - Sam's Rain Gutter Boat has RTV on it (holding sail and rudder in place).
I might have to roll out some lead into a ribbon.
Peace,
Tom