Model Boat Mayhem
Technical, Techniques, Hints, and Tips => BRUSHLESS Motors and Speed Controllers => Topic started by: raflaunches on December 16, 2012, 05:59:50 pm
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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.
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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 (http://www.hobbyking.com/hobbyking/store/__10171__GWS_EDF40_Power_System.html) 40mm dia., 87grams thrust, £5.40
EDF55 with 4300kv Motor Assembled (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8834) 55mm dia., 400grams+ thrust, £10.79
9 Blade Alloy DPS 110mm EDF unit - 10s 4070watt 980KV (http://www.hobbyking.com/hobbyking/store/__28367__9_Blade_Alloy_DPS_110mm_EDF_unit_10s_4070watt_980KV.html) 110mm dia., 7KG thrust (Yes! 7000grams), £159.77
Richard
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9 Blade Alloy DPS 110mm EDF unit - 10s 4070watt 980KV (http://www.hobbyking.com/hobbyking/store/__28367__9_Blade_Alloy_DPS_110mm_EDF_unit_10s_4070watt_980KV.html) 110mm dia., 7KG thrust (Yes! 7000grams), £159.77
If the boat masses less than 7kg, that could be rather entertaining. %%
Andy
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Gonna need a BIGrudder O0
Regards Ian.
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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) (http://www.hobbyking.com/hobbyking/store/__21146__Alloy_DPS_2_Series_120mm_EDF_unit_with_4_Pole_980kv_Motor_5000watt_12s_.html) 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
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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!
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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
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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
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Daily Express , Scottish edition. %)
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Like this?
http://www.rcgroups.com/forums/showthread.php?t=1544559#post19957173
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John Cobb.
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Tobyker has it in one. :-))
(http://i47.tinypic.com/2s9zvhl.jpg)
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.
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You missed post #8 then %) I think the air intakes will have to be enlarged and a cheater intake in the cockpit if possible.
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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
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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!!