DKM Tirpitz Refit

Discussion in 'Warship Builds' started by JustinScott, Mar 23, 2008.

  1. JustinScott

    JustinScott Well-Known Member

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    Well, Greg's Tirpitz is officially off the market! ......Because I BOUGHT IT! :)

    I have loved this ship since I first saw photos of it; the time & effort spent on making that deck & CNC modeling the superstructure is truly amazing. I simply don't have that kind of dedication. I am in awe of what you have accomplished, Greg.

    Over the next few months I will en devour to work to the same high standards and continue what Greg started. I wanted to take a moment to tell Greg that I respect the work he has done and say that any changes that I inevitably make to his original design are in no way a reflection on him or his master-craftsman-like skill.

    Without futher ado; the Tirpitz:


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  2. Powder Monkey

    Powder Monkey Active Member

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  3. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    Greg DOES tend to set the standard for cool stuff... :)
     
  4. GregMcFadden

    GregMcFadden Facilitator RCWC Staff

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    I look forwards to seeing her on the water :)

    -Greg
     
  5. froggyfrenchman

    froggyfrenchman Well-Known Member

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    I am not sure that you two know just how lucky you are.
    It is not often that someone is willing (or to be more precise ABLE), to part with a project that they have invested so much time and effort in, and have someone else finish it.
    The day that that beautiful ship hits the water will be a great day indeed. Not only for the one that gets it finished, but also for the one that got it started.
    And also for those of us here on the site that have been following the project, because of this site.
    Well done indeed..
    Mikey
     
  6. GregMcFadden

    GregMcFadden Facilitator RCWC Staff

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    Well, she did see some time on the water at least. But I realized that with my current commitments I needed the space, time, and money to finish development on the twin and tripple canister cannons (they are getting close) and then work on my design for a high efficiency pump.
     
  7. rowboat captain

    rowboat captain Member

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    bring it to nats this year and help us clear the lake of the allied infestation. :)
     
  8. JustinScott

    JustinScott Well-Known Member

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    Step 1: The Water Channel

    I've learned (the hard way) that the first thing a ship needs is a proper water channel. A good water channel makes it easy for water to get to the pump, and hard for it to leave. Several ways I know to accomplish this are:

    1.) Use vertical side walls to make a channel, instead of a V pattern. This helps prevent sloshing, not only for improved ship balance... but also so there is always water primed in the pump.
    2.) Use "waterfalls" or cross section-steps through out the boat (lowest section is always the pump pool) This again is to keep the water primed in the pump and to keep water from sloshing fore&aft(& sinking the bow during hard reverse).

    As you can see the Tirpitz does not have much as far as water channeling as is. The water can traverse the ship fore-aft (which is good) but there is nothing really to limit it or keep the pump primed. Another consideration is battery placement; if the water channel is placed below the batteries, the center of the ship is that much higher.

    The inside of the Tirpitz:


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  9. JustinScott

    JustinScott Well-Known Member

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    Step 1 Design: (Group suggestions requested)

    Channel Design: (Goin' round the Batteries)

    I like the usage of tubes because it keeps the batteries as low as possible to the keel. However, the one time I've used this solution, I had less than stellar results. Has anyone else used this solution, what were your reactions?

    What about twin water channels? Going around the batteries? I would think this could amplify the water slosh(as the water weight would never be balanced in the two channels) & cause the ship to tip even more easily.

    Left to myself, I would lift the batts 1/2" so the single centered water channel could do it's job.

    Opinions?
     
  10. Tugboat

    Tugboat Facilitator RCWC Staff Admiral (Supporter)

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    I'd leave a 1/4" to a 1/2" of room under the batteries. If that much added to the metacentric height causes problems, you've got too many holes in ya anyway. ;)
     
  11. GregMcFadden

    GregMcFadden Facilitator RCWC Staff

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    you will find that if you are using 6v 12ah cells, standing up in her, with connectors, they fill the whole hull bottom to underside of deck. Make certain you have the batteries on hand and know how they fit before you do anything permanent. Good luck! what was in there was a compromise between component space requirements and water flow. I look forwards to seeing her ready to battle.
     
  12. Powder Monkey

    Powder Monkey Active Member

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    Now I’m just a newbie but logically I agree I would run a channel under the battery keep the water channeled in center but logic has sunk many a boat I'm sure [;)]
     
    Julian Barbera likes this.
  13. DeletedUser

    DeletedUser Guest

    dude that ship looks nice so far i mean
     
  14. JustinScott

    JustinScott Well-Known Member

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    So it's been a week+, so I thought I'd catch everyone up on my progress. A lot of build threads show a lot of pics in various stages of completion... I think I will try to capture some of what I am thinking as I build too. Perhaps, someone can catch me before I make a stupid mistake... Perhaps it will save someone in the future from making a stupid mistake... who knows, but it seems worthwhile either way.


    Several Decisions I've made:

    Power:

    1.) I've decided to once again go with a 12V system.
    Why? Visit this site

    My decision on how many batteries was based on New Jersey & Alsace's power consumption. They both had ~220W*Hrs w/ 3x active motors; each time I wanted a bit more out of them. I chose their 550 motors based on what was cheap, or lying around... & I guarantee they were amp-thirsty motors. The Tirpitz has 2x active motors and I have selected a smaller more conservative motor (more later), so immediately I save some power.

    Further considerations for the 6V vs 12V system:
    ----> 1x 12V,18Ah = 216W*Hrs => $35 ~ $49
    ----> 3x 6V, 12Ah = 216W*Hrs => $42 ~ $49

    ----> 1x 12V,18Ah = 15 lbs
    ----> 3x 6V, 12Ah = 3x5 lbs = 15 lbs

    Space Configurations:
    12V Battery:
    ----> 7.1" beam, 6.5" long, 3" high (There is still more space, so if weight allows... more can be added)
    6V Battery:
    ----> 5.95" beam, 11.13" long, 1.97" high
    -OR-> 5.91" beam, 5.95" long, 3.71" high (not possible w/ .5" water channel)


    Motor:

    Yes I'm one of those crazy ESC-lovers; but this time I chose to keep it simple as far as ESCs are concerned... No fancy water cooled esc box like in the NJ. Just one standard waterproof mTroniks Marine40. Max Current of (go figure) 40A.

    So one of my highest conserns when choosing a motor is when it draws stall current; I want to give the ESC at least a fighting chance to survive. Additionally, wouldn't it be wonderful if the ESC could actually sustain full stall current of the motor? First off, the 40A protect fuse would not blow; so even though the ship is physically disabled... is isn't electrically. I could sit there and slam the drive back and forth & not worry. Would I ultimately be freed? Donno yet! :) Probably if the motor was simply stalled because it hit a rock or a stick... which is how I burnt an NJ ESC. (hmmph, still mad about that)

    I chose the Mabuchi RS-540 motor. It is the first time I'll be using a 540 speed motor, but being that I didn't even know the speed or torque of my last two ships... I might as well start low & upgrade if need be.
    Visit this site

    Note the stall current: 37.0A ;)

    Max efficency: 15080 RPM, 3/5 load, @ 5.93A... So 15K RPM is the target motor side rpm of the transmission @ BC's standard 2.5:1 ratio... So prop speed of 6000. Can't remember the final speed on the Iowa, or if I even calc'd it. Just have to play it by ear.



    Why a brushed motor instead of Greg's brushless designs?

    90% because of the transmission. Greg, I know you believe the belt would work just fine... But after my r/c cars, I'm just too leery of belt drives; too many broken belts from debris. I guess I could have made a hood for it, but BC trannys are turn-key...

    Additionally, my research into brushless suggests that they are great for high RPM (does not matter for us) & highly efficient @ low torque.... but as soon as torque is increased from low to mid, the gains they get from zro brush-losses become insignificant overall. Which makes them great for planes & to some extent race cars & race boats...

    What it came down to is: Are the potential benefits worth the potential issues. I finally concluded "not at this time".
     
  15. JustinScott

    JustinScott Well-Known Member

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    Water channel implementation & design:


    I decided to use the Treaty guy's water channel design mostly because it looks great and it seems simple. It also seems semi-permanent, so I want to do some 'scale tests' on it first... more to come as I learn.
    Visit this site

    The design seems to be centered around the idea of creating "skeletons and anchors". You need a skeleton to define where the cement should and should not be. And you need anchors to attach the ship's guts.

    From these pix, you can see my basic water channel skeleton & where each of my defined components will need anchors. (The motor will be replaced with the real motor/tranny once delivered next week.) The cross-members are my 'waterfalls' which define a change in water channel height, the pump sits in the lowest section of the water channel, a rectangle approximately 2.5" x 4".

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  16. djranier

    djranier Well-Known Member

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    Just make sure that it has no leaks, the concrete patch material will flow right out. Seal all the wood to the hull before you pour it in, to ensure that its not going to get underneath the wood frame, and leak into the water channel.
     
  17. Mark

    Mark Active Member

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    justin, the mtronics will be fine to run the ship, some things you should keep in mind are: put a fuse between each motor anf esc, that way if one bindes and blows its fuse you will still have the other. the other thing is if you are using a gear box one the motors you'll have nearly no reverse, mtronics escs reverse is not full power! I can tell you this from my experiance during Yamatos sea trials, I was using direct drive to the props and @ full speed throwing the motors in reverse it took longer than I expected to stop, just a word of caution.
     
  18. Powder Monkey

    Powder Monkey Active Member

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    Nice work Justin[^] A little off topic maybe (smack me here)[B)] but I noticed you use both deans and Power Pole what if any do you prefer
     
  19. JustinScott

    JustinScott Well-Known Member

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    This is a very very good point. I will 'glass the whole thing right before I 'concrete patch' it. Now... the finished concrete will wind up like concrete, or rubber?


    Really???? Oh, that's a problem. Did you perform initial setup procedures? AKA, theses things have to be programmed where their 100% is... Sure the ESC's brain wasn't just out of wack?


    Ummm... I can't remeber which is which any more. I use the ones on the battery. They seem to work just fine, and I will continue to use them. The one on the pump was put there by Greg. I will probably replace it as I'm wiring the ship. :)
     
  20. Mark

    Mark Active Member

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    oh yes, I programmed the breaking and reverse (you can't change the power of reverse, just the time delay). so what I would recomend (this is what I'll be doing) is go direct drive and control your ship speed @ the transmitter (after you get the speed dialed in just mark the point on the transmitter so that you don't exceed your rated speed. this also will give you the ability to get out of trouble if need be, ie.. a motor boat comming your way) you should still have plenty of torque @ the props before you start to blow fuses