Stingray Build

[Subculture]

My thinking was to hollow out the piece I've filled out in black. Water would suck through into the ratemaster where the prop was located.

[RCnut]

Cool, Thats what I envisioned, the same PJ as used in the Skydiver, Just got a bit confused, (Sunday mode maybe) Oh the Motor is a Tornado Thumper V2 4250/06 800KV Motor, Im thinking that should give the sub enough go to go.

Mamas

[He Who Shall Not Be Named]

Think, RCnut, how you arranged your pump-jets in your magnificent SKY-DIVER model. That's what I'm advocating for your STINGRAY (though a single unit). Only difference between the standard arrangement is the inclusion of the Y-splitter, slide-valve adapter between the intake and the rotor sub-assembly. Primary suction is from the long hole in the bottom of the hull, secondary (ballast water de-watering mode) is with the slide-valve open and the PJ taking a suction on the internal water to get the model to surfaced trim.

What differentiates a proper pump-jet from a shrouded propeller (or, Kort nozzle) is that the PJ outputs a stream of water almost exclusively moving axially, with little or no radial flow; the more mass moving longitudinally, the higher the thrust.

David,

[RCnut]

As I understand it a shrouded prop has a tube type ring around it. With water being pulled thru the front. Question, where would the water be coming from to be pushed out. The ratemaster backs onto the "Transom" of Stingray and is sealed so the only way water gets to the prop is from the end of the Ratemaster. Having said that, the main hull of Stingray reduces quite a bit as it goes back to the transom so space there is not going to be used as the WTC would not fit anyway. Or have I got this wrapped around the wrong way?

[Subculture]

A water jet is a shrouded prop, agreed. Usually very high in pitch, and designed to pump out water into the air. They have a fancy intake swan neck to draw water up from underneath the boat and expel past the transom, you don't need any of that in a sub- takes up space, which is nearly always at a premium.

I agree the Stingray on Youtube is sluggish. Not sure what was used motor wise, I do know it used one of the Prop Shop 15 blade propulsors, the type fitted to Sheerline trafalgars which looks fancy, but they're not the best at providing thrust in model form.

A two or three blade prop is optimum, and the stingray is a pretty strealined shape so should fly along nicely with a suitable power train.

[RCnut]

OK, I read that 3 times, I think I'm with it. All sounds good. I'm a bit concerned about a shrouded prop...Isnt that what a water jet is. Ok its a bit more concentrated but i dont see where a prop inside the Ratemaster would get adaquate water from to pump out at any great speed. If its that same 36 inch stingray on you tube then I want a bit more speed. At least Rate 6.

[He Who Shall Not Be Named]

To expand on Andy's excellent suggestion: we de-water the hull using the propulsion pump-jet. This done by rigging the PJ with a special adapter section between its normal 'from sea' suction and rotor. Forming a Y selector valve. A slide-valve (between suction and rotor) girdles the inside of the pump-jet Y adapter. One leg of the adapter leads to a suction within the hull. The other leg is the 'from sea' PJ suction.

Slide-valve closed the pump-jet gets water exclusively from the 'from sea' intake on the bottom of the hull, like your SKY-DIVER. To dive, a vent valve (in the bridge floor) opens and water floods in through the pump-jet 'from sea' opening (rotor must be stopped), the hull floods and the boat assumes submerged trim; shut the slide-valve and you're on your way. To surface, the slide valve is open, the boat is broached to put the bridge into the air, the vent valve is opened and the PJ run, sucking water out of the hull, (you still have thrust, but reduced a bit) and the boat assumes surfaced trim at which point the slide-valve is shut and you're on your way.

A 14" long, 2.5" diameter SD is doable! After dry space contains the motor (which one?), ESC, control surface servos, receiver, V-tail mixer, ADF, and Lipo-Guard. Center space is the 'safety-tank' used only if the boat can't broach the bridge above the surface -- it'll use the SAS method. The forward dry space is for the battery and mission-switch.

How's all that sound, guy's?

David

[RCnut]

Is it that one on you tube thats in the swimming pool?

[Subculture]

If you're building it to submerge a water jet is pointless, you just want a shrouded prop. The ratemaster makes a very suitable shroud, if this has a two bladed prop with say three fixed stators in front (pre-swirl) that should counter the torque nicely. This will make things more compact.

A chap down in Portsmouth has a 36" converted kit. That has a hydroplane and rudder made from clear plastic all housed inside the ratemaster, works really well, and looks stock when you see it running in the water.

[RCnut]

Right, I have taken som measurments (really rough ones) And by my reckoning a 3.5 inch tube would have to be 12-13 inches long to sit in there(And that would poke out of the top were the cabin sits) At 2.5 inches you could fit a 14 inch one. This is taking into consideration the Jet drive which has to go in there, And it will only go so far into the front between the missile tubes. Also the WTC would have to accomodate the shaft angle of said jet drive. Its got to be straight. Typical me again folks. I think WTC will have to wait till the things in Kit parts in front of me with a healthy supply of Pipes lol.

[Subculture]

Dave is referring to Mike Caswell, his guvnor!

My money will be on a 3" cylinder about 16-17" long.

Regarding getting the surfaced waterline. How about putting a valve in the top of the hull, and using a snort pump to blow air into the boats free flood cavity. That would give you an enormous amount of bouyancy to play with. A smaller tank could be used to trim for diving.

I don't think getting the ratemaster to spin will be easy.

[RCnut]

Ok I'll have a look in the morning and take some measurments and try to estimate the inner hull dimensions etc. BTW which Mike?

[He Who Shall Not Be Named]

I'm game. Let me know the maximum lengths your hull will take for a 2.5", 3", and 3.5" outside diameter cylinder.

As with most SF submarines, the STINGRAY had an impossibly high freeboard in surface trim -- but one we can get close if you keep the above waterline portions as light as possible, and we put the SubDriver down as low as possible.

Assuming you are close to what we see in the Phil Rae plans, I can use that as reference. What's the overall length of your STINGRAY? Knowing that I'll copy that drawing to that size, then skull out the SubDriver length-diameter-ballast tank size. I assume your glass lay-up wall thickness will average out to 3/32"? Will the cockpit be free-flooding or dry? Let me know what PJ you'll be using so I can work out motor and gear-train to match.

That grinding noise you hear in back-ground is likely Mike grinding his teeth.

David

[RCnut]

Lol no one, We can do a barter type thing if you want, I'm wondering about the WTC, I think this model would suit one.

[He Who Shall Not Be Named]

OK! ... who do I have to kill to get a set of parts?

David