Model Boat Mayhem - Forum

Please login or register.

Login with username, password and session length.
Pages: [1] 2   Go Down

Author Topic: SH....SH...SHARK!!!!  (Read 6683 times)

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
SH....SH...SHARK!!!!
« on: November 24, 2011, 07:11:29 PM »

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.







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 these keep changing and are currently out of date already.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 %%
Logged
Listen politely, nod approvingly, then do what you want, works for me!

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,888
  • Location: North London
    • Dive-in to Model submarines
Re: SH....SH...SHARK!!!!
« Reply #1 on: November 24, 2011, 07:23:16 PM »

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

andyn

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #2 on: November 24, 2011, 07:41:03 PM »

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 :-)
Logged

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
Re: SH....SH...SHARK!!!!
« Reply #3 on: November 24, 2011, 07:41:30 PM »

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 :-))
Logged
Listen politely, nod approvingly, then do what you want, works for me!

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
Re: SH....SH...SHARK!!!!
« Reply #4 on: November 24, 2011, 07:43:27 PM »

Liquid latex looses its elasticity after a few years and breaks down, rather like Mayhemers in fact..
Logged
Listen politely, nod approvingly, then do what you want, works for me!

DavieTait

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,113
  • Location: Fraserburgh
    • Trawlerphotos
Re: SH....SH...SHARK!!!!
« Reply #5 on: November 24, 2011, 07:59:40 PM »

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
Logged
Davie Tait,
Scotland
Site Admin www.trawlerphotos.co.uk

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,888
  • Location: North London
    • Dive-in to Model submarines
Re: SH....SH...SHARK!!!!
« Reply #6 on: November 24, 2011, 08:16:01 PM »

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

Jerry C

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 1,097
  • Location: Caernarfon, North Wales.
Re: SH....SH...SHARK!!!!
« Reply #7 on: November 24, 2011, 08:32:53 PM »

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.

CGAux26

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 570
  • Location: Deep in the heart of TEXAS (Tomball)
Re: SH....SH...SHARK!!!!
« Reply #8 on: November 24, 2011, 09:32:14 PM »

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/
Logged

salmon

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #9 on: November 25, 2011, 09:29:15 PM »

You can buy it here for $29.99 USD today only (Thank you black friday)
http://www.thinkgeek.com/blackfriday/?icpg=Banner_BlackFriday_H2011
I have two of these for work. They are fun.
Logged

Daemon

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #10 on: November 26, 2011, 12:07:08 PM »

they made a lifesized rc dolphin or something on mythbusters, using furniture foam for the main body - didnt dive, but it worked....
Logged

Chuffy

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #11 on: November 26, 2011, 02:02:01 PM »

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.
Logged

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
Re: SH....SH...SHARK!!!!
« Reply #12 on: November 26, 2011, 04:08:15 PM »

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...."

Logged
Listen politely, nod approvingly, then do what you want, works for me!

silent running556

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #13 on: January 19, 2012, 10:30:19 PM »

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.
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,888
  • Location: North London
    • Dive-in to Model submarines
Re: SH....SH...SHARK!!!!
« Reply #14 on: January 20, 2012, 09:30:53 AM »

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.

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
Re: SH....SH...SHARK!!!!
« Reply #15 on: January 20, 2012, 11:37:24 AM »

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
Logged
Listen politely, nod approvingly, then do what you want, works for me!

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,888
  • Location: North London
    • Dive-in to Model submarines
Re: SH....SH...SHARK!!!!
« Reply #16 on: January 20, 2012, 03:08:00 PM »

Not done any rubber to rubber moulds. I wonder if they're would be any reaqction between the urethane and silicone?

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
Re: SH....SH...SHARK!!!!
« Reply #17 on: January 20, 2012, 03:48:14 PM »

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!
Logged
Listen politely, nod approvingly, then do what you want, works for me!

silent running556

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #18 on: January 24, 2012, 09:34:51 PM »

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.
Logged

MFR

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #19 on: January 29, 2012, 08:39:38 PM »

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

Logged

silent running556

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #20 on: January 30, 2012, 06:59:45 PM »

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.
Logged

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
Re: SH....SH...SHARK!!!!
« Reply #21 on: January 31, 2012, 11:22:46 AM »

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?
Logged
Listen politely, nod approvingly, then do what you want, works for me!

Patrick Henry

  • Guest
Re: SH....SH...SHARK!!!!
« Reply #22 on: January 31, 2012, 11:44:48 AM »

Just a thought...but how about movable ballast? Might be worth looking into...


Rich
Logged

Subculture

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 3,888
  • Location: North London
    • Dive-in to Model submarines
Re: SH....SH...SHARK!!!!
« Reply #23 on: January 31, 2012, 01:28:17 PM »

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.

unbuiltnautilus

  • Portsmouth Model Boat Display Team
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,987
  • Location: Portsmouth, England, third rock from the Sun....
Re: SH....SH...SHARK!!!!
« Reply #24 on: January 31, 2012, 06:27:44 PM »

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..
Logged
Listen politely, nod approvingly, then do what you want, works for me!
Pages: [1] 2   Go Up