Alexander Engel TK-208 Russian TYPHOON Submarine build

[JWLaRue]

Ralph,

Are you trying to describe the relationship between the center of buoyancy and the center of gravity?

-Jeff

[Ralph --- SSBN 598]

U-571.
The group in Los Angeles is the group that meets at Yorba Park.
We gather about every other month with changes as needed to fit everyone's real life.
We agree on the next date before leaving the lake.
Next official gathering is January 12th 2019.
The date is posted below in the SubRonLA Topic. (Gates open at 7am and there is a $5 parking fee per car)

Note: There are some who meet more often at the park.
If you would like to be informed when that happens, let me know and I will forward the information when I get it.
----------------
Jeff, Yes Center of Gravity and Center of Buoyancy.

May they never cross vertically.
If needed, More weight and more foam (at and below the waterline)..

[JWLaRue]

Jeff, Yes Center of Gravity and Center of Buoyancy.

May they never cross vertically.
If needed, More weight and more foam (at and below the waterline)..

Correct....and you want the separation between the two to be as far apart as possible. The further apart, the more stability.

-Jeff

[u-571]

U-571.
The group in Los Angeles is the group that meets at Yorba Park.
We gather about every other month with changes as needed to fit everyone's real life.
We agree on the next date before leaving the lake.
Next official gathering is January 12th 2019.
The date is posted below in the SubRonLA Topic. (Gates open at 7am and there is a $5 parking fee per car)

Note: There are some who meet more often at the park.
If you would like to be informed when that happens, let me know and I will forward the information when I get it.
----------------
Jeff, Yes Center of Gravity and Center of Buoyancy.

May they never cross vertically.
If needed, More weight and more foam (at and below the waterline)..

excellent that's the place I was told to meet from other members but they would call it Yorba Linda Park its the same place excellent . LA Subrun

[u-571]

Help please

Engel's boats usually come with the correct amount of lead ballast.
Maybe a little more than needed but not much.

A suggestion:
If you received shot instead of bars, try using small ziplock bags and put small amounts of shot in several bags.
You can place them over the keel line and shape them to fit without lifting the wtc.
You can change the amount of shot in the bags to get near to the final weight.

Remember, you want the Center of Gravity on the surface high about the center of gravity submerged to keep the boat from rolling on to it's side during transition from surface to submerged and back.
If the two center of gravity locations cross the boat will roll.
Too much weight can be compensated with adding foam just below the waterline.

Using small bags allows you to mve them side to side and fore and aft to trim the boat.

Once you get it close, you can start fixing the shot 1 bag at a time to get the position set.

You can also, make long wooden forms to make bars that will fit.
Make the form and then wax it or place sandwich wrap plastic in so the weights do not bond to the form.
Mix up a little epoxy or some such glue/bonder and pour a little in to the form then add shot to make bards.
If you need more epoxy or glue, it's better to not have enough bonder and add more shot.

Not a good idea to bond all the shot in to 1 weight.
You may need to remove some later.

Hi Ralph, and Jeff,
Please explain or give me a example so I can picture it better in my mind trimming out the submarine, to get a clear view of what I need to do . You have me thinking but the difference between gravity, and center of buoyancy, is got me puzzled. I have never got that far, with my first submarine, I sold it to a new owner he trimmed it out. What do I do to get my gravity perfect then what do I do to get my buoyancy perfect plus they need to be far apart is better please explain .





correct me if im wrong first thing i was going to do is place the typhoon in the pool get the insides flooded then look at the stern, and bow, if one sticks up to much I was going to add weight until its perfectly level in the water .

second thing I would do is if it's sits to high above the water. I was going to add weight exactly in the middle, is this correct or way off.

[Ralph --- SSBN 598]

When you put a boat in the water, it settles down in the water creating a waterline.
To make the boat ride level, you need to position weight int he boat to move the bow and stern in opposite directions to get them at thelevel line (waterline) desired.
If the desired waterline is higher than you want, you add weight.
If the desired waterline is too low, you remove weight or add flotation. (foam below the waterline but near the waterline desired. (you do not want to have to lift foam out of the water. This increased the needed buoyancy)

Once you have the bow level end to end, you need to make sure the boat is level side to side.
You move weight side to side, towards the high side. (move it a little at a time.

This is to find surfaces Center of Gravity.

Next you add weight in the form of live ballast. (water is what we usually use)
You add enough live ballast to bring the boat down so there is only 1/4" to 1/2" above the surface of the water.
This is positive ballasted boat.
It will surface when the the boat is not moving and when moving the dive planes will force the boat under depending on speed. (submarines are not fast)

Once you get the boat down to submerge depth, you move the ballast forward or backwards to bring the boat to submerged level.
You also have to watch the side to side level.

You boat should be level on the surface and submerged.

As you transition from surfaced to submerged, the Center of gravity will move down and the Center of Buoyancy will move up.
Should these two centers meet or cross, the boat will roll on to it's side or may goes as far as capsizing.

This is where you need to add weight at the keel and foam at/below the waterline.
This will move the two centers farther apart and add stability.
================
reading

https://webapp1.dlib.indiana.edu/virtual_disk_library/index.cgi/4302894/FID1851/BOATCREW/files/ch09/ch9b.htm

Quick reference by a model builder.

https://www.rc-submarine.com/single-post/2016/05/23/Three-Simple-Rules-For-A-Perfectly-Trimmed-Sub-1

One other thing to keep in mind.
You can trim a boat out so it works perfectly and be light.
How every the lightly trimmed boat has to deal with the propulsion motor and propeller torque.

When you apply power to the motor, the propeller will dig in to the water and the boat will want to roll in the opposite direction.
More keel weight and more foam to off set the weight give the boat more stability against torque.

Once you start trimming your boat, this will start making sense.
=======
Basically you are trying to keep a teeter totter level in surface mode, submerged mode and in transition mode.
=======
Trim the boat to surface waterline first.
Here you can add weight and foam to get the boat level.
Then submerge the boat and see what happens.
If the boat is not level, move some keel ballast.
Try not to move weight to the extreme ends of the boat.
Move weight as near to the center of the boat.
Move small amounts of weight small distances.
------------
Last year I was trimming a boat and got in a hurry trying to get read for a gathering of boats at the lake.
The boat did not go.
On the way home, I was thinking about what I had been doing and realized I had been moving the ballast eights in the wrong direction.
I was moving weight from near center towards one end of the boat.
I should have been moving weight from the other end towards the center.

Got home and reset the ballast weight where it was and move weight from the other end and within minuted I had gotten level trim both surfaces and submerged.
I was over thinking it in my hast and forgot that moving from center to end exaggerates the weight leverage.
Moving weight towards the center, give more controllable leveling.

I hope I have not confused you more.
Jeff will be by and correct anything I may have got wrong. ( I do that on occasion, I get it backwards.)

[u-571]

Trimming a subamrine

Hi Ralph,

this is good information this is valuable information for others as well. Thank you for taking the time that was a lot of writing but makes perfect since to me . I understand you have 3 things you look for. one boat to be level in the water with water line in mind looking at bow and stern. Two must look at boat side to side center of gravity. I may have to move weight from one side to the other side small amounts. Three check to see how boat runs submerged if its off add weight to the center of boat keel or add foam also just below water line . This is to move the two center far apart from one another or it may roll.

[u-571]

Ralph,

Are you trying to describe the relationship between the center of buoyancy and the center of gravity?

-Jeff

Hi Jeff if there's anything you would like to add please do I like this information on sub trimming

[JWLaRue]

Trimming a model submarine is more art than science in the way the majority of folks do it. And there is more than one way to go about it. For example, Ralph stated that to start you want to get a proper surface trim. Others, myself included, start with a submerged trim. No matter which way you start the process you end up doing pretty much the same combination of actions, but in a different order. And either way you end up with a boat that is trimmed for surface and submerged use.

One thing I will point out from what Ralph said is around moving the weight once it's in the proper place for a surfaced trim. I wouldn't do that at all if possible. Instead, I'd be adding/moving foam around to achieve a proper submerged trim, with the foam being placed above the established surfaced waterline. Moving the weight for a submerged trim means that when the boat is then surfaced the weight is now in a different position from where you had placed it for a surfaced trim....meaning it's now in the wrong place. Since the foam is placed above the surfaced waterline, it has no/zero effect on a surfaced trim....so it's a win-win from a trimming perspective.

Okay, there is an exception to the foam being placed above the waterline: sometimes you need to counter the tendency of the surfaced boat to roll from side to side and adding weight won't correct it. In those cases, adding foam at and just below the waterline can work to provide roll stability. Ideally you want to boat to snap back to a vertical position if you roll it.

There is a wildcard in all of this: ballast tank placement can wreak havoc with the trim process. Ideally you want to place the center of the ballast tank directly over the center of gravity. This results in (essentially) no shift in the fore/aft trim of the boat between a full and empty tank. If you can do this, trimming should be easier to do. If you can't then you will need to use foam to counter the tendency of the boat to take on an up or down pitch orientation.

Over the past years there have been a number of articles/tips on trimming a sub in the SCR. The most recent example is one written by Bob Martin and can be fond in issue #108. Bob follows the "trim it surfaced first" philosophy and provides a clear explanation of how to follow that method.

-hope all this is making some sense and is helpful!

Jeff

[Ralph --- SSBN 598]

See, I knew Jeff would come in with more information.
Even thought Jeff and I may differ in our approach to trimming, (I am listening, Jeff) we get it done and I am sure there are other methods to accomplish good trim..

Jeff, I have a link above to Bob Martin's article found on his web page.

[u-571]

See, I knew Jeff would come in with more information.
Even thought Jeff and I may differ in our approach to trimming, (I am listening, Jeff) we get it done and I am sure there are other methods to accomplish good trim..

Jeff, I have a link above to Bob Martin's article found on his web page.

To Jeff, and Ralph,

Very good instructions you both are real good explaining the detail . I also noticed there's different technique but I can see it Leeds to the same result . Yes Bob Martin Article on trimming I have read it twice now good info as well . Both of your posts I think are excellent, for me, and others this thread will come real handy. As Jeff, had mentioned its an ART and science put together to make a good trimmed out boat .
thank you to the both of you I hope others feel free to comment .

[JWLaRue]

Jeff, I have a link above to Bob Martin's article found on his web page.

For some reason, it didn’t register with me that the link was to Bob’s site!

The write-up in SCR#108 is the same material. Bob submitted it so as to give it more visibility and to help fill the issue.

-Jeff

[u-571]

well I cut out the top to make a better clear viewing of all of the electronics. . I want to see what everything is doing. I notice many others do this method also, I'm jumping on board .

You will see there's a solid piece of metal that runs down the center on both sides I took that out. I will need to weigh that and replace that weight at the bottom of keel so everything balance out correctly towards Engels building instruction's
Jim

[u-571]

cutting out the acrylic for equipment housing



cutting out making 3 separate accessible areas to get to electronics in water tight compartment.

[u-571]

picture of viewing windows

I will be getting ready to place my stainless steel, machine screws, in for holding down the clear acrylic plates . I just purchased the Rubber o ring cord 10 feet, of it which will seal up everything water tight . back to work!