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[raflaunches]

I would like to know how powerful a brushless motor and the size/diameter of a ducted fan would have to be to move a hull, 31inches long and 13inches wide but only sits in the water in about an inch, at a pretty decent speed. The project is in the theory stage at the moment but the boat in question will built to 1/12 scale, the real vessel ended in disaster with the front planing shoe collapsing. Don't want to give too much away at the moment but I am sure there are members who have an inkling which silver and red boat I am talking about!
Any ideas will be gratefully received.

[richald]

I would like to know how powerful a brushless motor and the size/diameter of a
ducted fan would have to be to move a hull, 31inches long and 13inches wide but only sits
in the water in about an inch, at a pretty decent speed.

Not sure as to how much thrust you would actually need to achieve the performance you are after
but a quick look on the HobbyKing website shows quite a wide range of EDF units w/r to size, thrust 
(and price!) some examples....

GWS EDF40 Power System      40mm dia., 87grams thrust, £5.40

EDF55 with 4300kv Motor Assembled     55mm dia., 400grams+ thrust, £10.79

9 Blade Alloy DPS 110mm EDF unit - 10s 4070watt 980KV     110mm dia., 7KG thrust (Yes! 7000grams), £159.77


Richard

[dreadnought72]

9 Blade Alloy DPS 110mm EDF unit - 10s 4070watt 980KV     110mm dia., 7KG thrust (Yes! 7000grams), £159.77

If the boat masses less than 7kg, that could be rather entertaining. 

Andy

[Circlip]

Gonna need a BIGrudder
 
 
   Regards  Ian.

[richald]

bit of an error on my part ....

the 110 mm unit is only 6kg of thrust but more expensive - £169.30

the big daddy is the 120mm unit ....

Alloy DPS-2 Series 120mm EDF unit with 4 Pole 980kv Motor - 5000watt (12s)    120mm dia., 7KG thrust, £159.77

Incidentally both units pull around 110 Amps at maximum power - the wiring would
have to be a bit beefy!

Richard

[raflaunches]

Thanks guys


This gives me something to think about, who knows there might be a red and silver streak at Wicksteed park in the next couple of years!

[andrewh]

Very INTERRRRRESTING
 
Don't forget, raflaunches that these quoted thrusts are STATIC thrust for ducted fans - it increases radically as the fan starts to move and I can't quirte remember then it peaks - I seem to remember its when the vehicle speed is 50% of the jet velocity.
 
There won't be much published data on boats use with d/f, but you could regard it as a staggeringly draggy plane and see what can be learned that way
Generally tiny diameter high-speed D/F s are used for high speed aircraft.  Trainers etc use relatively large fans running slower.
Many areomodellers use home-rolled fan ducts with cut-down aero props and achieve very good results
 
red and silver?
andrew
 

[raflaunches]

Thanks Andrew


more for everyone to ponder...
Red and silver with two outrigger/floats!!! And went like a flash when it worked!!! (unfortunately it went bang on its last run)


Regards


 Nick B

[Arrow5]

Daily Express , Scottish edition.

[bikerdude999]

Like this?


http://www.rcgroups.com/forums/showthread.php?t=1544559#post19957173

[tobyker]

John Cobb.

[raflaunches]

Tobyker has it in one. 





John Cobb's jet powered Water Speed Record challenger, 'Crusader'.


Let us hope when I build it works and doesn't end up like the original.

[Arrow5]

You missed post #8 then     I think the air intakes will have to be enlarged and a cheater intake in the cockpit if possible.

[essex2visuvesi]

I have a 90mm ducted fan unit with 3.5Kg thrust from an aborted aircraft project, plan is to put it in a shovelnose Hydro at some point.  Looking at modifying the Notre Dame plans on Astec models

[tobyker]

we didn't miss post No 8 - it was obviously a bit too subtle. Indeed I didn't see the significance of it until I thought of his name, and the name of the boat naturally followed - Ah SO!!