Stingray Build

[Subculture]

After testing the smaller stingray with a Graupner Mini jet and Seeing it go under water and then shoot up again I dont think the power loss was that bad (But im not an expert) Its about half the push, Then again Do I want to be doing Rate 6 under water, lol.

The point I was trying to get across is that for a boat with submerged propulsors you don't need the space hogging scoops used in waterjets. If you cut the front half off a waterjet you have a shrouded prop with some fixed pre-swirl stators. If you're running a boat on the surface with the impellors above the waterline, then clearly you have got to have scoops, else they will never get to see any water!

[He Who Shall Not Be Named]

As I understand it, A water jet works best when the jet is pushing against air, Not so efficent Under water. After testing the smaller stingray with a Graupner Mini jet and Seeing it go under water and then shoot up again I dont think the power loss was that bad (But im not an expert) Its about half the push, Then again Do I want to be doing Rate 6 under water, lol.

Right, The Graupner 40mm jet will not fit the Stingray and allow you to install a Big enough WTC. So I have gone with the Kehere 28mm jet. It will be powered By a brushless motor same as Skydiver. I'm Looking at this one as a kind of Test bed, when David has done his stuff I'll hopefully do another. I have thought of a way to make the ratemaster spin and I'm reasonably confident it will work. The jet has been installed in the conventional way as it was in a pretty poor state (Having been ripped out of another model, Skydiver) the other will be winging its way to the US in a couple of days. I will take pictures tommorow and post.

Standing by.

David

[RCnut]

Oh and the other reason I didnt want to use the 40mm one was that the intake would interfear with the big Stingray logo unerneath. Sad I know but hey!

[RCnut]

As I understand it, A water jet works best when the jet is pushing against air, Not so efficent Under water. After testing the smaller stingray with a Graupner Mini jet and Seeing it go under water and then shoot up again I dont think the power loss was that bad (But im not an expert) Its about half the push, Then again Do I want to be doing Rate 6 under water, lol.

Right, The Graupner 40mm jet will not fit the Stingray and allow you to install a Big enough WTC. So I have gone with the Kehere 28mm jet. It will be powered By a brushless motor same as Skydiver. I'm Looking at this one as a kind of Test bed, when David has done his stuff I'll hopefully do another. I have thought of a way to make the ratemaster spin and I'm reasonably confident it will work. The jet has been installed in the conventional way as it was in a pretty poor state (Having been ripped out of another model, Skydiver) the other will be winging its way to the US in a couple of days. I will take pictures tommorow and post.

[greenman407]

True, but as model builders, most of us will try anything at least once.

[Subculture]

Unless your skydiver requires the jets to sit above the waterline then I don't see the advantage in a waterjet over a normal ducted prop arrangement. After all waterjets are optimised for sucking up water and squirting it out the back into air. Something that doesn't happen very much on a sub!

[greenman407]

I checked out that site on the jet drives. The smallest one that they make is the 28mm which is made for a 700 size motor. All well and good but an effort will have to be made to waterproof the motor if its going to be made to submerge as these are made for ships and boats. For my 36" Skydiver, they would be way too big to fit inside its small confines.

[greenman407]

Thanks Subculture.

[Subculture]

Full details of the Kehrer range on their website- http://www.jet-drive.de/index.php?op...id=4&Itemid=17

[greenman407]

Mamas, can you give me some dimensions on the Kehere? Like overall length, battery voltage, motor size , etc.

[He Who Shall Not Be Named]

I understand -- we're both involved in some 'organic', on the fly engineering here. Fine, send both examples, but work up a hull foundation plate for each. We'll make something work here.

David

[RCnut]

This is not going to plan. 2 reasons. This Jet is way to long and will interfear with the Stingray logo underneath. The other reason is the flange that holds the impeller housings is a shade smaller then the ID of the Ratemaster. The other thing is its using way to much length and will compramise the size of any WTC that will go in there. I'm thinking its time to go the Kehere Jet way. There a bit smaller but will push just as hard. I'm going to send you an old kehere and the Graupner intake and see what you think. Here are some pics, the black jet is a Kehere.

[RCnut]

COULD YOU POSSIBLY MAKE THAT DRAWING ANY SMALLER!!!???.....

Perfect. Radius the corners a bit and we're in business.

Lol Its Only Window paint.

[He Who Shall Not Be Named]

Really rough sketch Open it up in paint and zoom in, lol.

COULD YOU POSSIBLY MAKE THAT DRAWING ANY SMALLER!!!???.....

Perfect. Radius the corners a bit and we're in business.

[He Who Shall Not Be Named]

I just had a thought, As my lay up thickness can vary, how about a custom made plate that I will lay in place and it would be embedded into the bottom hull. with indications for the screw fixings for the jet? I'll make it up tommorow and take some pics. If you like it then I will cast one up and send both items. In fact I will Do that and set the angle on the jet to make sure it all lines up. What do you think?

Perfect!

What are you .... some kind of Model Builder?!

David