RE: RC Shark
 

If you want water to enter the sub while the shark opens and closes its mouth, the amount of water getting in the sub at the time can perhaps affect the trim some what, remember, KISS! I don't think you should worry about it too much, with the mount closing and opening, maybe you could catch a fish or two![8D]

RE: RC Shark
 

Well, I was thinking that the mouth could just have a flat plate in the upper jaw so that water doesn't enter it. The plate would be hidden by the teeth so you wouldn't see it anyway, and painted a suitable colour to look like flesh...

RE: RC Shark
 

Well, I just got my copy of Marine Modelling International (the one with the R/C shark) and GOD-DAMN! This thing has a moving tail! It makes the great white in "Jaws: The Revenge" look even worse! :D

I'm away for a read....

RE: RC Shark
 

Can you describe the mechanism?

RE: RC Shark
 

Taken from the article:

"Thoughts turned to the actual tail drive which had to be articulated to give the required undulating motion, and this turned out to be quite simple and consists of 10 segments made from 25mm x 18mm x 38mm long rectangular Tufnol tube. The first segment is bolted to the aft bulkhead and each subsequent segment attached to the next by means of top and bottom brass plates screwed to one segment with a pivot pin in the next. The gap between the segments is minimal to limit the movement, and the last segment carries an M4 stud onto which is fixed the actual tail. The drive consists of a Como Drills 11:1 ratio gearbox which in turn drives a 6:1 worm reducer and on each end of the wormwheel shaft is a crank arm, each arm being set at 180 degrees to the other. Each arm has a crank lever which in turn drives a push rod passing through an O-ring gland attached on the aft bulkhead. This is attached to a piece of of picture wire which makes a nice stranded brass cable and this passes through guides on each segment to be finally attached to the last segment."

Because he didn't think the tail would be able to turn the shark, he fitted a water thruster with a flap that diverted thrust out through the gills in order to steer it. The bodywork is fibreglass, and the rear tail section is silicone rubber. The tail itself is a sandwich of brass and silicone. Apparently it works quite well, and with the water thruster disengaged, the tail actually powers the shark forward without a loss in speed!

RE: RC Shark
 

[sm=cool.gif]

RE: RC Shark
 

A bit too complicated for me! I'm letting the guy with the U-boat have a look at my shark stuff next week.

If I can, I'll scan the r/c shark photos from the mag and post them up.

RE: RC Shark
 

Haven't managed to scan the r/c shark photos yet, but I'll have a go soon.

Will be off to see the guy with the subs again tonight, who tells me he was at a big model boat show and saw... well, you can guess the rest!!

RE: RC Shark
 

I've been thinking about the great white model, and a bigger (better?) idea has surfaced!

I've been thinking of something along the lines of a 1/10th scale MEGALODON shark - that'd be 6.5ft long.

I've thought that, if I could use a ballast tank to regulate depth so as to make it neutrally bouyant, then use the fins (like the smaller one) to dive and surface the shark...?

What do you think??

RE: RC Shark
 

Good idea, you have to be aware that some ballast tanks allow you to dive the sub at a certain depth and "float" with a bit of the sub on the surface, a pump ballast tank is one example. This is a good starting point because if you have failures in your diving planes, the sub will still float up because it is slightly buoyant, just adds a bit of realism because you're diving vertically.

Some complicated ballasts like a gas powered one will aquire more experience. A very good choice will be a piston operated ballast tank because it acts like a sucker to suck water in and out, no gas required!

RE: RC Shark
 

Well, as most of the time people want to see the fin, I would imagine that the pump ballast tank would suit this particular shark....

Now, how to build it....?! :eek:

RE: RC Shark
 

The exact same case happened to me with my Kilo project, to make the ballast tank, if that's what you want to know, you have to include some sort of a pump, I used a fan style pump in mine, the fan which circulates water, is operated by a motor through a gear link and you'll also need a cutoff valve so that when you're not operating the pump, water doesn't go into the ballast tank. Some very good ballast tanks can be bought from OTW designs, a company located in the UK,

www.otwdesigns.com

remember: the motor has to be able to go both ways! In one direction and the other!

RE: RC Shark
 

I'll give that site a look later...

Back to the Great White, however, the sub-guy, Andrew, reckons the drawings are coming along OK. Now I just need to figure out where to put everything in order to A) balance it, and B) figure out how to operate the pectoral fins. I need to allow enough room for leverage of the arm within a watertight compartment inside the shark itself.

Funny that, because when I originally thought of doing this 2 years or so ago, this was exactly what I was envisaging having to do on the model (even though it didn't work out in the end :eek:)....

RE: RC Shark
 

balancing the sub is just like balancing objects on a scale itself, the ballast tank should be located in the center of floatation, to figure that out, put everything in the sub in their desired place (electronics, servos, receiver, battery, etc) drop the sub in the water, (make sure that your WTC is waterproof when you do this :D) use a stick or pencil to push the sub underwater to trim level and you'll probaly notice that one end of the sub will be heavier than the other.

Move the stick along the sub until you get to one place where the sub is properly balanced from both ends, mark it and this should be where the ballast tank should be. I got this trick from the Subconcepts page, quite useful! You can go on their website to check out a few tricks too. Just go to the Sub Guide at the top.

RE: RC Shark
 

Thanks for that tip - I'll use that for the big shark (if I ever build it!).

Mind you, would this hold true for a dynamic diver??

RE: RC Shark
 

I guess so, I mean, you have to make sure that it is positively bouyant and you can also use the diving planes to regulate depth, that's one less thing to worry about........

RE: RC Shark
 

I just updated my website on the Nautilus, I think you might manage to save an extra RC channel if you can figure out how to static dive in 3 chs, follow this link and you can find stuff about the model:

http://captainnemo12.tripod.com/nautilus.html

RE: RC Shark
 

Well, as I know squat about static diving just now, I'll stick to trying dynamic diving! :D

Just got a nice shiny new airbrush to paint the shark with (eventually!!)

RE: RC Shark
 

I know I've been saying and saying this, but I WILL get that shark article/photos scanned up! I haven't had much time recently, but I'll make time on Sunday to get it done!

RE: RC Shark
 

BTW, when I e-mailed Math Vos on questions about my shark sub, he said to put the heavy material as lower as possible inside the sub, to avoid the fin disturbing the rudder movement problem (thanks Bob for letting me know about this! ;)), I figured if it worked with Math's sub, it might work on mine to.

RE: RC Shark
 

I wouldn't have thought the fin would disturb the rudder, but if they say so....

I'll have those pictures tonight - these are long overdue!!

RE: RC Shark
 

Dennis The Menace:

FINALLY copied the shark pics!! Here he is, all 1410mm of him!

RE: RC Shark
 

sweet!!!!!!!!!!!!:D

RE: RC Shark
 

Right, the drawings are just about finished - I just need to do the plan-view for the layout of RC gear.

BTW, I was thinking a generic great white shark, although very cool, wasn't going to stand out, so I'm "Bruce-ifying" my model and turning it into the shark from Jaws instead! :D

RE: RC Shark
 

I've made a start on a website for my project. This page so far refers to shark models that I have found or been told about:
http://www.greatwhiteshark.4t.com/photo3.html