Seawind conversion
03-16-2007, 06:23 PM
#51
RE: Seawind conversion
Gentlemen,
I converted and flew a GP Seawind. The setup is as follows:
Weight -- 10 lbs -- all up including batteries, no landing gear. No nose weight required to get CG to 32 mm behind leading edge.
Motor -- AXI 4120/18
Batteries -- 6s1p 3200mah electrifly for propulsion, 700 mah nicad for receiver and servos
Prop -- APC 13x11 (flying at 6200 and 7700 ft.) Drop to 13x10 for sealevel flying
ESC -- Jetti Opto 70
Battery to esc wires -- 10 gauge copper with 250 uf capacitor at esc to chop voltage spikes
Max power > 1100 watts measured using Astro watt meter
To date all flying has been off of snow, I'll let you know what the water performance is like. However, takeoffs are relatively short at the 7700 ft base altitude and there is no tendency to dig a tip in when taxiing at low speed.
If you are really worried about voltage spikes, consider going to a high voltage system. If I were to start over, I would consider starting around a DeWalt 36v battery (actually a bunch of A123 Cells) to cut down on current load in the circuit.
I converted and flew a GP Seawind. The setup is as follows:
Weight -- 10 lbs -- all up including batteries, no landing gear. No nose weight required to get CG to 32 mm behind leading edge.
Motor -- AXI 4120/18
Batteries -- 6s1p 3200mah electrifly for propulsion, 700 mah nicad for receiver and servos
Prop -- APC 13x11 (flying at 6200 and 7700 ft.) Drop to 13x10 for sealevel flying
ESC -- Jetti Opto 70
Battery to esc wires -- 10 gauge copper with 250 uf capacitor at esc to chop voltage spikes
Max power > 1100 watts measured using Astro watt meter
To date all flying has been off of snow, I'll let you know what the water performance is like. However, takeoffs are relatively short at the 7700 ft base altitude and there is no tendency to dig a tip in when taxiing at low speed.
If you are really worried about voltage spikes, consider going to a high voltage system. If I were to start over, I would consider starting around a DeWalt 36v battery (actually a bunch of A123 Cells) to cut down on current load in the circuit.
02-09-2009, 02:15 AM
#53
RE: Seawind conversion
Gregg,
The space in the hull is big enough that there is plenty of circulation around the batteries to cool them. 5 minute flights barely warm up the batteries that I am using. The esc is a bigger problem; it is the component most likely to die if it gets wet. Putting it in a sealed plastic bag cuts down the cooling so I have elected to oversize my esc. I'm currently using a 77 amp esc. If I were starting from scratch, I would elect to go with a higher voltage, lower amp setup to minimize heating. Current thinking is to put the esc near the batteries and run long leads up to the motor.
Bob
The space in the hull is big enough that there is plenty of circulation around the batteries to cool them. 5 minute flights barely warm up the batteries that I am using. The esc is a bigger problem; it is the component most likely to die if it gets wet. Putting it in a sealed plastic bag cuts down the cooling so I have elected to oversize my esc. I'm currently using a 77 amp esc. If I were starting from scratch, I would elect to go with a higher voltage, lower amp setup to minimize heating. Current thinking is to put the esc near the batteries and run long leads up to the motor.
Bob
03-03-2009, 07:26 AM
#54
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RE: Seawind conversion
Hi guys well I finally got to take home my sea wind on Saturday night and spent the next few hours fitting the hinges to the flaps and ailerons. I found a picture of a full sized seawind that confirms my suspicions that the step is way too far forward and should be just infront of the C of G, this makes Great Planes out buy about 3", this in turn would cause the model to drag it's bum in the water and rotate prematurelty and richochet like a pig on landing unless dragged in on the stall.....all in all not pretty! I also noticed that the hull is rediculously thin around the step which is right where the most abuse takes place, to help overcome this and the dreaded splitting of the seams, I have laid some 3k carbon cloth about an inch up the side walls an accross the bottom of the hull. To overcome the dodgy step location I will be extending the step 3" rearward with blue foam and have laid carbon cloth an additional 1" behind the new step so as not to create a stress riser.
To help reduce the requirement of lead in the front I will be using closed loop on the rudder and be remotely driving the elevator with a pushrod and be mounting the servo in the engine pod.
I have also decided to use mechanicle retracts because there sitting on the shelf and heaps lighter than the robarts although they do look pretty trick, just not the price tag! I'll also be fitting nose doors so I can taxi into the water pull the gear up and take off and visa vera after landing..... it's going to be relatively easy to do and will really add to the scale appeal.
cheers Rossco.
To help reduce the requirement of lead in the front I will be using closed loop on the rudder and be remotely driving the elevator with a pushrod and be mounting the servo in the engine pod.
I have also decided to use mechanicle retracts because there sitting on the shelf and heaps lighter than the robarts although they do look pretty trick, just not the price tag! I'll also be fitting nose doors so I can taxi into the water pull the gear up and take off and visa vera after landing..... it's going to be relatively easy to do and will really add to the scale appeal.
cheers Rossco.
