jet engines

[GTR Dreamer]

hi, i know this doesent have much 2 do with cars, but engines none the less. i want to build a mini jet boat,(for 2 people). and i want to know what sort of engine layout they have. do they have the engine, then a jet unit? or just strait through 2 a propeller? any help appriciated. also do they have a gearbox.?

[johnnynumfiv]

http://travel.howstuffworks.com/turbine.htm

[GTR Dreamer]

thanks johny

[pcgms]

Hi GTR,
You might want to look at eBay listings for engine and parts prices. The prices my scare you a bit as they are not on everyone's "grocery" list. Also check out www.RCUniverse.com You can ask them about powertrain layouts, etc.
If I see anything else I'll pass it along.
John
"I chase my dreams today, for tomorrw may never come."

[Renesis]

stop

gtr if by jet boat you mean something like a jet ski, there really is no jet engine involved.
all it is is an enclosed propeller...
i took an engineering class at mit and i had to build a submarine prototype, and i decided to go the unusual way and build it with the propulsion method of a jet ski. it turned out kind of impressive...

think of your boat as a car, and with an enclosed propellor you have the advantage of placing the propellor, or propellors, in the center area of your boat- just like a mid-engined car..

if you were really going to build a jet boat, and it will be incredibly hard to accomplish in terms of engineering, but, heres how you could set it up:


------- --------------
\------------/
8 8 8
water in (props) water out
/-------------\
-------- --------------



think of those 8s as propellors.
water should enter an almost frictionless duct with a fairly large diameter, the water should be squeezed into one of several smaller ducts which house propellors. the exit ducts for water (can i call them exhausts?) have to be smaller in diameter than the first intaking duct. Physics states that the higher pressurized water in the first duct will squeeze into the exhaust duct, which is tighter, and will gain velocity

simple logic...

high pressure gains velocity from propellor-- gained velocity = gained energy

high pressure into smaller diameter pipeline causes naturally higher velocity- actually much higher


end result, if you can do this right, which i doubt any of us will (i hardly got it right in my case, enough to work, not enough to impress people), then you get a boat that is much faster, agile, useful, then using the conventional propellor in the back approach

hope this helps a wee bit...
(as for the thing about gears, i dont think boats have gears, rather they are kept in a high gear all the time)

[Renesis]

sorry, bad picture, lemme try again

-------\______________

intake water~ props~ exit water

______/----------------

[GTR Dreamer]

thanks renises.....extremely helpful.

[crisis]

If you are thinking turbo jet one must ask why? It would be useless for anything short of speed records. Heres a link if your interested. "Jet boats" as described previously are mearly large water pumps connected to combustion engines. The Hamilton Jet was a New Zealand invention which had the benifit of needing inches of water to proceed with no prop protruding under the boat.
http://foxxaero.homestead.com/newsplash.html