Skydiver 5 foot build

[RCnut]

Hi Guys, Been on and off on this for a while now but I'm determined to finish it now. Heres where I am with it now. I need to install the jets and then its a question of adding all the details. Anyone out there know about Graupner jets and what Motors work best with them. I have a pair of 700 bbs but rather go Brushless (Dark art lol) As the 700s take a lot of juice.

[Subculture]

Is this going to run on the surface, or be a true submarine? Difficult to recommend a motor- 700 size motors come in so many flavours. Easier to get an idea if you know the prop diameter and pitch, system voltage and what sort of performance you are looking for. I find Hobbyking is a great resource for cheap (but good) brushless motors of all shapes and sizes. I think brushless motors are much easier to match, as they're usually much better documented than many brushed motors.

[Subculture]

Looked up the spec of the jet drives- 40mm diameter props. Don't know about pitch, but have assumed 1.4 times diameter- I think these drives have quite a lot of pitch. That measn you only want fairly low revs. Assuming you're looking to run 3S lipo 11.1 volts then a couple of these would probably do the trick. Certainly more powerful than any speed 700 I know of.

http://www.hobbyking.com/hobbyking/store/__15199__HobbyKing_Donkey_ST3508_730kv_Brushless_Motor.html

[RCnut]

Thanks for that, This diver will probably be just a surface runner and if I can manage it able to sea skim with the aid of a massive jet drive.

[Subculture]

Getting it to move shouldn't be a problem- can get anything to shift with enough brute force and ignorance. Getting it to handle well should be interesting though....

[He Who Shall Not Be Named]

If you're not heart-felt, dead-set on the Groupner pump-jets, maybe a set of mine would suite you? I have various sizes.

David

[RCnut]

On my Smaller 3 footer I had two 28mm Kehere jets, the handling was fine, Apart from stopping lol. My main problem is that it being a Sci fi sub its design is not as a "normal" sub is. So I want to keep it un altered in the looks dept. And that to me poses more problems lol.

David, Forgive my lack of Knowledge but I have not seen your jets, Im assuming there on here somewhere. I will go have a look. Alternatives are allways a good thing.

[Anuci]

The concept of using bilge pumps to propel a 30lb Disney Nautilus has been fostered to great sucess by a friend of mine, as he has experimented their use in a 4ft and 7ft model.
This may be an alternative means of propulsion to consider in your model. With sufficient space for batteries these pumps can certainly push water with sufficient force to accomplish the task at hand. Just a thought!

http://www.amazon.com/Rule-27D-Marine-1100-GPH-12-Volt/dp/B000O8F6NE

Al,

[RCnut]

Heres where I am, I've decided to go with the Graupners for now (Well there bought and Paid for) and done some measuring and I can install the 700s I have. If the jets work I will replace them with Brushless motors, I've also extended the depth of the intakes just in case the positioning needs tweaking here and there. Due to the subs underbelly being concave there is the issue of the motors hitting the floor, I've shortend the shafts to bring the motors as far in as possible to aid clearence.

[greenman407]

So Im assuming that youll put the 700s in a water tight cylinder of some kind?

[RCnut]

I could do but as its going to be a surface runner for now there going to be out in the open, I did have them in watertight containers when I was using Kehere drives but I gave them to my mate who is doing a Static diving one. He has all the technostuff WTC allready made.

[Scott T]

What if you took one jet and split it between the above surface nozzles, then
took the other jet and port it out the bottom of the hull.
Then when going slow you could use either pump sigularly to propell the
boat. Then for afterburner performance you turn on both pumps.
Another thought is to have a hydro plane under the front section of the
ship to give you enough lift above the surface to fly along.

Scott T

[RCnut]

Hi Scott
Only problem there is that I'm not using vectored thrust steering on this so I need both jets to steer the thing. I did think of a hydroplane arrangment underneath along with a real big jet, this would have been equipped with trim tabs and the whole lot stabelised by gyros. My Overiding concern is "scale looks" I dont want anything to interfear with the original lines, A pain I know. I was considering a detachable jet unit that would do it and then take it off to display.

[RCnut]

I've Installed the jets, Hopefully will be ready for water test on Sunday.

[greenman407]

Mamas, looks real good. I know that this is only a test. As you already know youll need a whole lot more thrust than that to get her to sea skim. Your going to have to go BIG brushless, for sure.