MAD Dave Posted October 27, 2016 Share Posted October 27, 2016 I am considering converting my Sparrow Hawk to electric power. Is there anyone out there who has successfully done so and able to offer some practical advice please? Even a reasoned "Don't do it!" recommendation would be helpful! Many thanks! Quote Link to comment Share on other sites More sharing options...
MAD Dave Posted October 28, 2016 Author Share Posted October 28, 2016 No feedback so far regarding possible conversion of my Seagull Sparrow Hawk .61 1.6m ARTF to electric power..... Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 28, 2016 Share Posted October 28, 2016 Why no 4 stroke? Quote Link to comment Share on other sites More sharing options...
ARC Posted October 28, 2016 Share Posted October 28, 2016 Hi Dave, Ran mine on 6s and flew lovely , nice model and looks terrific on nice slow fly pasts. Batt hatch under cowl is a nice touch Andy Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted October 28, 2016 Share Posted October 28, 2016 Being able to fit an hatch for changing lipos is the biggest issue i reckon, other than that you just need to select a combo to fly it, give flying weight, what size prop ground clearance will allow and i'm sure someone will advise you. John Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted October 28, 2016 Share Posted October 28, 2016 SK3 various kv motors in the range and reviews worth looking at to give an idea on prop sizes and power achieved..5-7 cell lipos needed so you can get sizes and see if model will take them. John Quote Link to comment Share on other sites More sharing options...
Rich too Posted October 29, 2016 Share Posted October 29, 2016 Don't do it! As Jon mentioned, stick a nice f/s in there! But I'm a petrol head! Quote Link to comment Share on other sites More sharing options...
MAD Dave Posted August 4, 2017 Author Share Posted August 4, 2017 After a break of too many months, my attentions have returned to this project. Apologies in particular to Rich2 but the Sparrow Hawk now sports an electric motor. I am currently looking at which prop spec to go for. I can easily check maximum watt "consumption" of the motor v's prop dimensions under static (airframe) conditions to match motor power rating but, I am unsure what comparatively happens when the airframe gains speed and progresses to flight. For a given throttle setting, will the watts consumed increase, decrease or remain ~constant? Level steady flight assumed of course. Anyone any ideas? Quote Link to comment Share on other sites More sharing options...
Former Member Posted August 4, 2017 Share Posted August 4, 2017 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted August 4, 2017 Share Posted August 4, 2017 The power consumption will normally decrease once the model is moving forward Dave, but I've never monitored power in-flight to tell you by just how much. I would guess at well less than 10%. To be honest it's not something that's ever worried me. Quote Link to comment Share on other sites More sharing options...
MAD Dave Posted August 4, 2017 Author Share Posted August 4, 2017 Thank you Percy and Bob for your responses. The advice I have received is that, for this type of model, I should aim for 80 to 120 watts per pound. The Sparrow Hawk auw, including chosen motor, has worked out at 8.5 lb so we have the band required as 680 to 1020 watts. I opted for a 900 watt Overlander motor and am keen to see that power delivered to the prop. Using my watt-meter, I find that driving a 12x6 and 12x8, the declared power consumptions are ~700 and 800 watts respectively. I will try a small range of 13 inch props when they arrive. I should be able therefore to find a prop that causes the motor to reach its 900 watts potential under static conditions on max throttle but my initial enquiry is of course what happens after I let it go! Will the power delivered reduce; should I over-prop it for static conditions? Perhaps I am trying too hard but I have a desire to get matters as right as I can before I attempt a flight! Quote Link to comment Share on other sites More sharing options...
Gordon Tarling Posted August 4, 2017 Share Posted August 4, 2017 My advice would be to use a higher pitch prop. A 13 x 8 may work OK, but I think I'd try a 13 x 10 if it were my own model. I doubt you'll notice any reduction in takeoff performance and you can always throttle back if the model is too fast. Quote Link to comment Share on other sites More sharing options...
MAD Dave Posted August 25, 2017 Author Share Posted August 25, 2017 My "Electric Sparrowhawk" has now had its first outing. It flew well and the landing was good enough such that "I can use it again"! For anyone else interested in maybe undertaking a similar conversion, my final powertrain comprised :- Overlander - T4260/06 motor, 500kV, 900W. Overlander 60A ESC Batteries - 2x Zippy 5.8Ah 3S (ie 6S total). 13x8 APC E-prop. Static max power consumption was measured as ~850W. At the field, a few club members sucked their teeth a little, wondering whether the 900W motor would be adequate; flying weight being a few ounces under 9lb. As a possible surprise to the gathered throng, me included, the initial take off run was quite sprightly and several S&L-ish orbits of the field followed whilst assisted trimming etc ensued. The initial flight timed out at around a little over 6 minutes, post one overshoot, and a successful landing completed. Electricity consumption is always a concern on first flights, but I was latterly further surprised to observe that each 3S battery was indicated as having 80% capacity remaining! Maybe I have over-egged the battery size a little. Hopefully, the above information will be of use to someone contemplating either a similar conversion or fresh installation. Quote Link to comment Share on other sites More sharing options...
MAD Dave Posted August 25, 2017 Author Share Posted August 25, 2017 P.S. Now having a Sparrowhawk GRP cowl with (no longer required) cut-outs in it for a '61 ic, I contacted Seagull and enquired whether they would sell me a replacement. Good & bad news - Yes, but at 11usd for the item and 44usd postage! I may renew my association with home-brew GRP practices.....😏 Quote Link to comment Share on other sites More sharing options...
Braddock, VC Posted August 25, 2017 Share Posted August 25, 2017 Try jperkins distribution, they are the importers of seagull and may well have spares. Quote Link to comment Share on other sites More sharing options...
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