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    Orca the final cast member
    33 Posts ยท 8 Followers ยท 28 Photos ยท 192 Likes
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    Commodore-H
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    โ€œTwenty five feet, three tons on himโ€
    Quote, Captain Quinn
    The sure way to succeed is, just try one more time
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    flaxbybuck
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    Let us know when you will be releasing the film. ๐Ÿ˜‰
    ChrisG
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    Not only a great model but the comprehensive details of the build has been very entertaining as well as amusing. I just hope that the RSPCS donโ€™t hear about one of their fish/animals being so cruelly mutilated.๐Ÿ˜‚๐Ÿ˜‚
    One thought I had was will the towing vessel be up to the job in bad weather or will the shark rebel and go its own way?
    Rogal thanks for the entertainment regards ChrisG
    Andi1
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    Looking good,
    jumpugly
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    Yessir...
    Rogal118
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    Made a start to get jaws sitting right in the water, decided to go for it and started by disemboweling him with the dremel. Then formed the lead sheet into 3 blocks and took the weight it read 1.8kg so I thought I would start at that weight rather than be under and have to add small extra pieces. The first task was to fit the lead blocks in the slot on the sharks belly, I stopped these falling out using cocktail sticks pushed into the foam each side of the slot. Doing this enabled me to right the body without the lead blocks falling out, he was then laid in the bath tub water. As can be seen in the accompanying photo he sank too low in the water, so I trimmed the lead blocks down a tried again, perfect just right, so back to the bench I packed the sides of the lead with foam to hold in place and placed a strip of wood over the slot then mixed filler and covered over. Then sanded the belly smooth and water tested again. Spot on, job well done, if I say so myself. Total finished weight 2.2kg he quite a heavy chunky guy, you would think he would sink to the bottom but floats very stably. Just the live test at the pond to go now, tomorrows out though as 20 mm of snow is forecast locally and I canโ€™t find my snow shoes. House bound then.
    Roger
    ChrisG
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    Not surprised your brain hurts! mine hurts and I am on the side-lines. ๐Ÿ˜‚๐Ÿ˜‚๐Ÿ˜‚ ChrisG
    RNinMunich
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    ๐Ÿ“ Orca the final cast member
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    Hi Rogal,
    We'll have a whip round to get you a bottle of Original Taste.๐Ÿ˜‰
    Can't recommend Diet Coke. Not much real difference in calories and various studies indicate adverse health effects from the synthetic sweeteners used.
    Apart from that it tastes bl***y awful and makes terrible Cuba Libre๐Ÿ˜

    "If I used the whole internal volume as a ballast tank I would loose the buoyancy of the foam, catch 22".
    The mass of the foam involved is negligible compared with 1.6kg.
    I don't think that would make a significant difference Rogal. Remember, it's the submerged volume that accounts for the displacement, and swim depth. So I don't think that Captain John Yossarian's psychological problems are applicable here๐Ÿ˜‰! (Yes I have seen the film and I have the original hardback book by Joseph Heller.)

    You have already proven that you need 1.6kg to get Jaws to float where you want it to.
    Add a few grams to compensate for the loss of the interior foam if you wish but I wouldn't bother. Mass involved is negligible compared with 1.6kg.
    More important is most likely the angle of incidence of Jaws' lateral fins.
    So I totally agree with Andi1, until you try towing Jaws to see if he swims, dives or porpoises you are working in the dark. A negative (downward) angle will force him under, a positive angle will force him to surface. Possibly causing him to leap above the surface (depending on the speed) and diving back down again, i.e. porpoising . Ditto repeato! Would be fun to watch though๐Ÿ˜€ But perhaps not what you are looking for. So aim for neutral incidence, i.e. horizontal.

    My recommendation would be to go with ca 1.6kg (140-145cc) lead within the body.
    Would either need 4 more slots like the one you have already made.
    Or one plug of 4cm diameter by 11.25cm length.
    Much easier to accommodate than 1600cc of water๐Ÿ‘
    Which would need a cylinder of about 10x20.5cm.
    In most boating lakes a false bulb under the ventral will be visible when near the shore and detract from the visual effect and swimming - added drag! Also when on display on shore. Aggro mounting and demounting! We don't want to give away our little secrets do we?๐Ÿ˜‰

    Your problem reminds me strongly of a similar snag I had with my 1/72nd scale dynamic diving Type 1A U-Boat, from Krick LoA 107cm.
    Built according to instructions she floated too high, despite two 6V 4Ah SLAs, dive planes were still above waterโ˜น๏ธ
    Just like you I draped weights over the hull 'til she floated right.
    Then milled hull compartments fore and aft to accommodate corresponding weights of lead.
    Hull construction was 'bread and butter', i.e. 4 planks of 2cm thickness.
    On sea trials the dive planes would still not push her under but just threw up huge 'moustaches' of water. Spectacular but not exactly true to original๐Ÿ˜
    I then did some research at the Deutsches Museum here in Munich, where U-1 is on display with the starboard hull plating removed to expose the interior, and bought a helpful book about U-Boat designs, with scale plans. This told me that the Krick dive planes were too small.
    So I made a new set. Still to be trialled as most unfortunately shortly thereafter U25 suffered a severe collision with the workshop floor๐Ÿ˜ฎ๐Ÿ˜  Subject for a future Blog๐Ÿ˜‰

    Bon chance mon ami๐Ÿคžlooking forward to your progress reports / trials videos๐Ÿ‘
    Schlaf gut!๐Ÿ˜ด
    Cheers, Doug๐Ÿ˜Ž
    Young at heart ๐Ÿ˜‰ Slightly older in other places.๐Ÿ˜Š Cheers Doug
    Rogal118
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    My brain hurts!, Iโ€™m going to bed early night.๐Ÿ’ค๐Ÿ’ค๐Ÿ’ค
    Roger
    RNinMunich
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    Hi Chris,
    I'm not a biologist, much less a marine biologist (my biology and chemistry teachers and I reached a mutual conclusion that it would be better if we amicably parted company and I devoted the thus freed up time to my strengths; physics and applied maths, with German and English Lit/Lang on the side.)
    So I don't know how fish and other aquatic creatures manage that. A question of scale and evolution I suspect. They are mostly more concerned with pressure equalisation I would think. Implosion at depth or explosion near the surface would be most unfortunate.๐Ÿ’ฅ

    No, I took the simple pragmatic engineer's view.
    As soon as I read Rogal's post it struck me that a mass of 1.6kg of water would occupy a volume of 1.6lt or 1600cc.
    This immediately called to mind my 1.5lt bottle of the said Coke on my bar (used for my Cuba Libre๐Ÿ˜‹๐Ÿ˜‹), which I measured. Length 10" (25.4cm), excluding tapered part of the neck, mean diameter 3.5" (radius 4.5cm).
    Volume of a cylinder is V=ฯ€rยฒh. Thus V=(22/7)x4.5ยฒx25.4cmยณ. =1615.87818cmยณ (cc).
    As near as dammit 1.6lt. The rest of the Coke is in the tapered neck of the bottle.

    The largest recorded white shark is 20.9' (6.4m) a female!
    Now I don't know how big Rogal's shark is but at 1/16th scale the big mamma would be about 40cm long. Alas I can find no data on the girth of such a monster munching machine.
    Interestingly the females are generally larger than the males. EEK๐Ÿ˜ฎ
    Male great whites on average measure 3.4 to 4.0 m (11 to 13 ft) in length, while females measure 4.6 to 4.9 m (15 to 16 ft).

    Comparing volumes of other potential ballast materials is a simple matter of dividing the volume of 1.6kg of water by the relative density of the other material; e.g. lead 11.34 g/cmยณ.
    Required volume thus being 1600/11.34=141cmยณ. much easier to fit to the model shark.

    Hope that clarifies my dumb engineer's thinking for you Chris.
    Cheers, Doug๐Ÿ˜Ž
    Young at heart ๐Ÿ˜‰ Slightly older in other places.๐Ÿ˜Š Cheers Doug
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