looking for a fast 30-40mm jetdrive settup for an 800mm Vhull

[crazyprophead]

hi everyone, i have modelled some brushless 100kmh+ Vhulls and a rigger but i now want to try a jetdrive settup on a 800mm Vhull that will give me at least 70kmh.
does anyone know the limitations of model jetdrives and how fast they can push a boat before cavitating? And has anyone attemped a fast jetdrive settup?

any tips or suggestions will be greatly appriciated,
thankyou.

[mtbenjamin77]

I'm all ears on this one. I'd like to start a race class for jet drive boats. I think a cat with twin jets would be awesome

[Hor2012]

I'm all ears on this one. I'd like to start a race class for jet drive boats. I think a cat with twin jets would be awesome

2nd that

[crazyprophead]

Cool guys!! Yeah i think the biggest problem will be cavitation because it will be hard to get a good flow of water in the pump when the boat is up on plane, because im guessing the water will just like to skim over the intake hole when on plane

[borgie]

make a scoop on the jet intake yes it may cause a bit of drag but at least you wont get cavitation

[crazyprophead]

make a scoop on the jet intake yes it may cause a bit of drag but at least you wont get cavitation

thanks man! are u talking about a small scoop? Or a big scoop? this definetally wont be as effitient as a prop but oh well its a challange :) im thinking of building the jet miself using a 50mm prop or so turned down to 40mm

[borgie]

watch this it shows the guy building the jet http://www.youtube.com/watch?v=HROUtpIgYp8, a medium scoop

[srislash]

I have a scratch built flat bottom here with a 30mm Graupner jet in it. It has yet to see the water. But the jet will suck the hull down on the water.We know this from the drag boat racers.It also limits speed,but for a designed purpose they rock.
It is the one in my avatar behind the slash.

[rabosi]

KMB & Graupner make a 40mm jet drive also.

http://www.jet-drive.de/index.php?option=com_virtuemart&page=shop.browse&category_id=2&Itemid=17

http://www.cornwallmodelboats.co.uk/acatalog/graupner_2340.html

and then there is this behemoth http://www.hobbyking.com/hobbyking/s...e_X_Large.html

Good luck. I'm looking forward to seeing your build.

[sundog]

I have been 'experimenting' with a 40mm Powerjet drive from KMB for some time installed in an "Ed Hardy" version of the NDQ High Wind 29" mono. I removed the ugly (IMO) steering fins and made up several nozzles of my own design (trim-able, reversable, and back to the original design) in an effort to find the best configuration for running creeks and rivers here in the Ozarks. Jet drives are power hungry and require bigger motors and esc's. This mod would porpoise badly and I had to install trim tabs of my own design to tame it. I started with a KB45 motor (inefficient), then tried a Fiegao, a Castle 1515, and finally settled on a Turnigy T600/1400kv outrunner with a Castle 240 LV esc. I don't have a way to check the speed, but I estimate I'm getting better than 30mph on 4S. Soon I will try it on 5 and 6S to see how it does. I know I'll need to relocate the batteries to the port side as it was listing (like chinewalk) pretty bad with the big outrunner. But I don't doubt it will reach the speeds you're looking for with a couple more cells. Jet drives are not known for their speed (compared to prop drive) so it never interested me to see how fast I could get it. My main interest was to be able to use it in shallow water - this is where jet drives really hold their own.

[crazyprophead]

ahhhh thanks a lot guys for the imput! really appriciate it!! my questions have been answered now :) but im at uni at the moment and will have to wait for my holidays before i build, but i mostlikely will build it cos i love the way jetboats handle!!