Sri Ayuthia/Dhonburi Build

Discussion in 'Warship Builds' started by Bob Pottle, Aug 26, 2008.

  1. Bob Pottle

    Bob Pottle Well-Known Member

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    After admiring the looks of these Siamese 'pocket heavy cruisers' for years I've decided to try to build one for R/C naval combat. They're rated as Class 1 Gunboats by the IRCWCC, and are Axis ships.

    These Japanese built ships were the largest in the Siamese Navy in the late 1930s, armed with four 8" guns in two turrets. Both were sunk in 1941 after an attack by a French cruiser squadron operating from Indochina (now Vietnam). Both were raised, Dhonburi sinking under tow to Japan for repairs. Sri Ayuthia was repaired in Japan and returned to Siam (now Thailand). It was sunk by shore batteries during the revolution in 1951.

    They were handsome vessels with the typical Japanese undulating deck lines and Japanese style 8" turrets. However they displaced less than 2500 tons standard. As models in 1/144 scale they are about 21" LOA x 5" beam. Displacement of the models with the extra 1 lb allowed under IRCWCC and MWC rules is about 3 lbs.

    A mold for the hulls was made several years ago and one light weight hull was made. It's been sitting in my basement for years while I wondered if I could build such a small armed combat model. After building the ~4.5 lb HMS Gorgon and HMCS Prince Robert, I think it can be done.

    Very small motors will be needed to keep the model at its slow Treaty Combat speed, and only a BC micropump will be small enough to fit. I'll use a small Rock the Boat regulator and 16gm CO2 cartridges, plus microservos.

    I made the hull deep enough so that at the max. allowed weight it floats within 1/8" of scale waterline. Photos of the build will be posted as it progresses.

    Bob
     
  2. Anachronus

    Anachronus Well-Known Member

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    Sounds like an interesting build.
     
  3. Gettysburg114th

    Gettysburg114th Well-Known Member

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    Are there any good links showing pictures of these ships?
     
  4. HMCS

    HMCS Active Member

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    Not sure of any links, but the class is listed in Conways with a side view line drawing.
     
  5. Gettysburg114th

    Gettysburg114th Well-Known Member

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    Thanks HMCS,
    I have to get out and get my own copies of Conways. They should have been in my book case years ago.
     
  6. HMCS

    HMCS Active Member

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    Here we go:

    [​IMG]
     
  7. CURT

    CURT Well-Known Member

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    OH I like the looks of this one. More please gimme more..
     
  8. klibben

    klibben Member

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    I've been thinking about building one of these for some time now, as I'm a fan of monitors and also the Axis.

    However, that is generally what they are described as.... monitors, not pocket heavy cruisers.
     
  9. HMCS

    HMCS Active Member

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    Curt that's the entire Conway's entry,it's a bit cut off but since Bob wrote exactly what they have for info I wasn't too worried about the text, just getting the picture big enough. Haven't tried doing a web search yet though.
     
  10. Jay Jennings

    Jay Jennings Well-Known Member

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    I was able to find these
    J

    [​IMG]

    [​IMG]

    [​IMG]

    Hope they help.
     
  11. Bob Pottle

    Bob Pottle Well-Known Member

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    Jay,
    The top photo is a memorial at the main Thai Naval base. It's the salvaged bow turret and bridge of the Dhonburi set on a mocked-up deck on the lawn.

    Bob
     
  12. Jay Jennings

    Jay Jennings Well-Known Member

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    Really? Crap, I had a larger, colour photo of the same thing, but that one I knew was a memorial. If I can salvage it from the trash can I will put it up too.
    J
     
  13. Jay Jennings

    Jay Jennings Well-Known Member

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    Here is the other picture. As you can see, there is more structure shown in the smaller picture, which is why I chosse it.
    J

    [​IMG]
     
  14. Bob Pottle

    Bob Pottle Well-Known Member

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    Jay,
    I found an entire web page in Thai with that photo and about a dozen more showing exterior and interior turret details.

    Had a closer look at the hull and mold last night and realized from the construction it must have been one of my early projects. The unfortunate thing is that the plans I'd bought were not great and the stern shape is way off. The small coloured plans you posted show a sharply tapered stern, which is a good match to the one stern photo found. The plans I used had a wide bluntly curved stern.

    I've sanded the stern area to reshape it as much as possible but the improvement is only slight. Oh well, I'm not about to make a new mold because of it. I'll put lots of gelcoat in the stern during lay-up so the hulls' sterns can be sanded a little sharper.

    I'm laying up one hull for me next week and will post photos.

    Bob
     
  15. Jay Jennings

    Jay Jennings Well-Known Member

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    I am happy the little one helped, I love those colour plans, they helped allot with the ISE.
    Did you get my e-mail wrt the Kent CA hull?
    J
     
  16. GregMcFadden

    GregMcFadden Facilitator RCWC Staff

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    Hey Bob, that looks like a slick little ship, what are you running for propulsion?

    thanks
    Greg
     
  17. Bob Pottle

    Bob Pottle Well-Known Member

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    Greg,
    I'm going to try 280s with 20mm 3 bladed props, but am a long way from trials. I'm laying up the hull tonight and tomorrow.

    Bob
     
  18. GregMcFadden

    GregMcFadden Facilitator RCWC Staff

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    Keep me posted.
     
  19. Bob Pottle

    Bob Pottle Well-Known Member

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    The Sri Ayuhia hull lay-up will be finished tonight. Over the last 3 days I've been gradually building up a thick layer of gelcoat in the stern, so it can be sanded to a more sharply tapered shape. (The plans used for the plug had the wrong stern shape.)

    The fiberglass will be laid tonight and there should be some photos to post Saturday. There's one more hull to make - it'll be going to Florida.

    Bob
     
  20. Bob Pottle

    Bob Pottle Well-Known Member

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    After an unsuccessful attempt to remove the Sri Syuthia hull from the one-piece mold, a slot was cut in the stern of the mold and a wedge tapped in, freeing the hull on Saturday. The thick gelcoat applied in the stern area allowed it to be sanded down to the correct, more tapered shape.

    Because the deep displacement was uncertain the hull had been made 3/4" deeper than scale. After much searching I've been unable to find any deep displacement except that given by George Goff: 2604 tons.

    With that displacement and the extra 1.0 lb allowed for Class 1-2 warships the maximum model weight is 2.95 lbs. After a test float at that weight, and allowing for the minimum 1/2" freeboard the hull can be trimmed down by 1/4" along the deck edge. (The scale freeboard aft would be only 7/16", which is 'illegal'.) I'll take only 3/16" off the deck edge to allow a margin of error.

    The model will have the undulating deck edge typical of Japanese built warships - the deck dips down almost 1/4" between the bridge and the bow. The turtleback forecastle deck will be a challenge.

    Being such a short model the solid areas at bow and stern had to be reduced to only 13/16" each to get enough ribs. The model will have 7 x 3/16" ribs, with 2" windows between them.

    Photos will be posted when the hull has been trimmed down. The mold is being waxed today for a second hull that will be shipped to Florida.

    Bob