Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Submarines => Topic started by: unbuiltnautilus on November 24, 2011, 07:11:29 pm
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Never one to be building only one, two or three projects at any one time. Myself and John from the Portsmouth Model Boat Display Team have embarked on preliminary research into an RC Shark.
(http://s9.postimage.org/px1hi48uz/DSCF0021a.jpg) (http://postimage.org/image/px1hi48uz/)
(http://s12.postimage.org/6np90pnrd/sharktale.jpg) (http://postimage.org/image/6np90pnrd/)
(http://s7.postimage.org/xicx0yh3b/shark2.jpg) (http://postimage.org/image/xicx0yh3b/)
(http://s9.postimage.org/x5qwcmpqz/JAWS_16a.jpg) (http://postimage.org/image/x5qwcmpqz/)
The first image is a cardboard mock up I built about 5 years ago to check available space as well as practicalities relating to the flapping tail. The other sketches are preliminary internal arrangements. these keep changing and are currently out of date already.
We are mocking up drawings to full size while also researching 'shark skin'. Currently I am mucking about with polyurethane rubber two mix, which is looking promising, it sticks to itself, it can reproduce detail well, and it will last longer than either latex or foam latex...however, we need to brush it onto a model or into a mold and it will run off vertical surfaces, any suggestions for either a thickener or a similar material to aid us? We have been dealing with Tiranti's of Reading so far, however, they do not produce a thickener. I have tried an epoxy thickener, which consists of fibres, it works but ruins the inherent flexibility of the shark skin.
The cardboard mock up is 60" in length, John wants to boost that to 72"! My concern is we will have to stick wheels on the bottom %%
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Can you not brush it on using very thin coats, gradually building up a thicker layer?
You can thicken silicone rubber with a thixo additive. Tiranti do it.
Also worth looking at Smooth-on products. Not cheap, but good stuff and they do brushable rubber products e.g.
http://www.smooth-on.com/Silicone-Rubber-an/c2_1113_1135/index.html
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In your local hobbycraft they do thick liquid latex you paint on in layers. Never used it, but pretty sure it'd be suitable.
Andy :-)
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As the polyurethane rubber comes, it remains liquid for about 40 minutes before starting to thicken up, therefore, not suitable for brushing at present. I will look into the products suggested, also 4D Modelshop market something called Dragonskin, this may also be an option, cheers for the link :-))
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Liquid latex looses its elasticity after a few years and breaks down, rather like Mayhemers in fact..
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There's been a few swimming rc models built over the years including a few for the US Navy.
I have a program from the 1990's somewhere called robopike which also shows the original robotuna free swimming demonstrator the USN wanted to try as a silent spy vehicle
http://web.mit.edu/towtank/www/Tuna/tuna.html
http://www.necn.com/Boston/Business/Robotuna-to-be-used-for-military-intelligence/1217027539.html
http://web.mit.edu/towtank/www/Pike/pike.html
http://www.google.co.uk/search?q=robopike&oe=utf-8&rls=org.mozilla:en-GB:official&client=firefox-a&um=1&hl=en&biw=1024&bih=586&ie=UTF-8&tbm=isch&source=og&sa=N&tab=vi
Davie
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also 4D Modelshop market something called Dragonskin, this may also be an option, cheers for the link :-))
Dragonskin is a Smooth-on product. It's a seriously stretchy type of silicone rubber. Nick Burge did a swimming shark some years back (late 90's) nicknamed 'Dennis the Menace'. it was featured in Marine Modelling magazine, and you can see it alongside other creations in a video of his I converted to digital and bunged up on Vimeo.
http://vimeo.com/20679846
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I can definitely recommend the smooth-on brand, I use their mold max 305 with a Thi-vex (their brand name) thixotropic additive , once the additive is in it will stay exactly where you put it, perfect for trowelling or brushing into place and the 305 is very tough.
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Just got an Air Swimmers Shark for my son. It swims through the air by wagging its tail. The tail wagging motor is smaller than a pinky fingernail, and runs on one AAA cell. You operate it by pushing Left and Right buttons in a rhythm, and using more Right commands for a right turn, etc. It goes up or down via another button labeld Climb and Dive, that makes the onboard control module run fore and aft on a track under the shark balloon. Good lessons in buoyancy and center of gravity. $40 to $50 in the US. Check out the video.
http://airswimmers.com/
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You can buy it here for $29.99 USD today only (Thank you black friday)
http://www.thinkgeek.com/blackfriday/?icpg=Banner_BlackFriday_H2011 (http://www.thinkgeek.com/blackfriday/?icpg=Banner_BlackFriday_H2011)
I have two of these for work. They are fun.
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they made a lifesized rc dolphin or something on mythbusters, using furniture foam for the main body - didnt dive, but it worked....
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Simon the shark has already been built and ready for sea trials by a member of the Wicksteed Model Boat Club. It will sail along side its little friend Tubby the Tuna. Tubby swims underwater and can be made to porpoise if that is the term, swims along underwater and then jumps out. Both are scratch built, Simon is about 2'6" long and is very lifelike. Both were on display at Warwick on the WPMBC Club stand.
Paul.
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I met Simon and Tubby at Warwick, as well as their owner, had a very nice chat, us shark owners must stick together as you never know who is out there, lurking..."Farewell and adieu, to you, fair Spanish Lady...."
(http://s10.postimage.org/j3ti2lls5/IMG_8836.jpg) (http://postimage.org/image/j3ti2lls5/)
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I've seen a killer whale version and that thing could do all sorts and quick too. There's a vid of it somewhere, on the web site about the lido in london. This thing moves like arocket.
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That belongs to a Belgian modeller who came over for one of the events. He had a small shark too, but I didn't manage to get any shots of it running.
The whale had a steerable prop, which I think was a graupner hydrospeed unit.
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We are currently practicing on a squid, perfecting ( slowly ) the art of rubber molding. The good news is that a second set of squid tentacles came out of our silicone mold with no signs of the sticky problems associated with the first pour. This time, leaving the mixed PU rubber to sit in the mixing cup for five minutes before stirring again seemed to help. The shark will be a whole other problem :o
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Not done any rubber to rubber moulds. I wonder if they're would be any reaqction between the urethane and silicone?
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So far, using silicone molds and PU Rubber, no major problems. we used a Silicone release spray for the first mold, didnt re-spray for the second mold, which released just fine, and a third mold is setting as we speak, with no additional release spray applied. Silicone seems to stick to silicone but to nothing else, while we are demolding after a minimum of 24 hours rather than 4 to 6 hours as with the first shot. Its a bit of a learning curve!
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That belongs to a Belgian modeller who came over for one of the events. He had a small shark too, but I didn't manage to get any shots of it running.
The whale had a steerable prop, which I think was a graupner hydrospeed unit.
That's the one, it corkscrewed at high speed through the water like a missile and porpoised too. My hat off to their skills.
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I know the guy with the shark personally, he is called Raf,
Found a nice vid driving his shark,
http://youtu.be/LhgVIuaisQo
Also a vid which shows the orca killer whale,
http://youtu.be/m6CH8b9zx2E
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It seems like the shark's more difficult to control out of the two. Great work though. 8) Someone will be doing an Anaconda before long.
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My old shark from the eighties was prone to suffer similar, unexpected crash dives to the bottom of the pond, as are other shark models viewed on line. Is this an issue caused by the streamlined snout acting as a 'down planes' command, and has anyone any idea how to make a shark behave in a more controlled manner?
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Just a thought...but how about movable ballast? Might be worth looking into...
Rich
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If you're using a prop, make it tiltable. Works on the Disney Nautilus, which also tends to want to dive of it's own accord.
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Have considered some sort of 3D nozzle similar to those underwater Starships, only problem being the upper body gets in the way if you propel it midships or two fifths of the way from the back, which seems to be where I keep coming to in the designs. An earlier option had a Harrier Jump Jet style set up with a big impellor inside the mouth running to two outlet ducts port and starboard aft. These would have had a splitter plate between them for steering and ( recently modified to ) louvres for up and down control. This could be used alongside shifting ballast, possibly just to alter the 'at rest' trim of the model. Nose down being of more use underwater, while nose up more suited to eating Barbie and Ken on the surface.
Nice to hear Nautilus suffers from the same issue, cheers for letting me know that :((
Actually didn't Nick Burges shark use a similar splitter plate design via piping? Just round the other way..
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Nick's shark 'Dennis the Menace' was featured in an article in MMI magazine some years ago. It didn't have any control over pitch, the thrusters were used to steer the thing via the gills. There was a compressed air ballast system on-board to control depth. It went very slowly anyway, so presumably static forces were adequate to keep the boat level when underway.
With the Nautilus, the problem is intensified with speed. It's the upsweep of the forward rakers that causes the down force on the hull.
How about making a hammerhead shark. If the nose is rubber, you could twist the ends like forward hydrovanes.
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How about making a hammerhead shark. If the nose is rubber, you could twist the ends like forward hydrovanes.
They're not real Sharks though, God was having an 'off day' that day surely?
Like your logic :-))
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Reckon they'd seem real enough if one was nibbling at your pinkies!
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I can't remember the name of the vid but there's one of a diver with a shark that was very controlled and he had it swimming round him in circles, it wasn't doing the head banging stuff at all. i'll have a little nose about.
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There is this one. http://www.youtube.com/watch?v=Rfi7VIVN0dY&feature=related
Very agile and fast- fitted with rear vanes, cheating but good control. At the end of the day, a shark can bend it's body in a variety of ways that would be difficult to implement in model form.
There's a more cartoon-ish fish on this video. http://www.youtube.com/watch?v=DliEJ8AqcMY&feature=related
Just a warning to those of a sensitive disposition- there are swimmers in shot on these videos!
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oh no not swimmers
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Aka the menu. O0
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AKA...victims.
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Hi mate
Just seen your shark problems have you considered ballistics gel which is designed to mimic muscle. You make a plaster cast mould and pour stuff and wait for it to set
Glen
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I looked that up, says it based on gelatin- won't that go off over time, not to mention is it waterproof?
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Maybe Plastidip will work for your skin. You could spray that onto a Dacron sheet.
http://www.caswellplating.com/restoration-aids/plasti-dip/plasti-dip-spray-white-11-oz.html
It is also available in black
Dacron is a sheet that stretches on the bias, often used in membrane roof systems.
I noted that it was suggested to use a latex coating, but these water based materials absorb water in immersion. I think the Plastidip would be better.
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Sharks on hold over the summer, squid to be completed soon, but keep the good ideas coming, this is a bit of an 'out there' project and any input is greatly appreciated :-))