Nigel Davison Posted February 1, 2009 Share Posted February 1, 2009 I have a plan for a 36" sport electric model , because of my location and flying site i want to slow it down , anybody know if would be ok to extend the ailerons , currently the area is 288 and i want to add around 36sq in , i also intend to increase the control area of the flap . i think i can do all this and still retain its intended flying weight of around 20 oz . i intend to fit a brushless motor around 200w and 1000kv . because thats what i have . any comments on the aerodynamics would be appreciated . Quote Link to comment Share on other sites More sharing options...
David Perry Posted February 1, 2009 Share Posted February 1, 2009 The general method of adding area is to increase the span. When you say increase flap and aileron, presumably you mean chord? In which case the roll rate will go up but so will the forces on the servos. The flap area increase might be interesting - the drag could well go up more than lift so the lift flap becomes drag flap and the drag flap becomes brakes!! Worth a try though... Rather than add chord I would add span - bung another 3 inches a side (assuming a rough 6" chord, thats yer 36sq in). Also consider the section - you might find a "slower" section, depending of course on what you are starting with, although a thicker section would do the job whatever the starting point. That motor will seem to give you 200w a pound! phew...and you want slow?? Let us know how it goes...and how fast! D Quote Link to comment Share on other sites More sharing options...
Nigel Davison Posted February 1, 2009 Author Share Posted February 1, 2009 Thankyou david i was getting concerned that no-one was replying , it was just a thought i had this old plan and i guess from what you have said i really should start from scratch and find the right model for the motor etc. i do love to experiment though !!! Quote Link to comment Share on other sites More sharing options...
Jonathan Lewzey Posted February 1, 2009 Share Posted February 1, 2009 I think flaps would be too complex on a model of this scale. It would just increase the wing loading and make it stall at lower flight speeds. The answer is not to make the surfaces bigger or to alter the design, but to make it as light as possible so landings can be slowed up. Whether this is done by careful equipment selection (ie saving weight by not using a 200W motor), building as lightly as possible or selecting a different airframe more suitable to your motor and field requirements. My multiplex funjet uses a 350Watt brushless outrunner in a can for superb high speed performance, but due to its low weight and high wing area it can really be slowed down for landings and doesn't bite. As you've got an outrunner i can't recommend the funjet, but what about the Gemini, Parkmaster, most fliton aerobats around 1metre or the excellent PA Addiction Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 1, 2009 Share Posted February 1, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Nigel Davison Posted February 1, 2009 Author Share Posted February 1, 2009 thanks eric and all , i have found i have an old 400 motor which i will use with the plan i wanted to use and i'll see how that goes i think it should have enough power . on the other motor i will have a go at scaling up another plan i have that may be more suitable . i have read a bit and i guess i was being over cautious on the power side ie: i was aiming at the 100w per lb mark and wanted a little too much safety margin . thanks again , and timbo , sorry wont happen again . Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 1, 2009 Share Posted February 1, 2009 Nigel just to go back to your original post. As Eric says just increasing the area of the ailerons will only "slow the model down" if it increases the total wing area. Extra flap area will have the same effect but remember you will be adding all this area to the back edge of the wing which will make the plane act nose heavy. So unless you can move the CofG back a bit to compensate I doubt you will be able to actually fly slower. Now if you can increase the span to get the added area then the centre of pressure will stay more or less unchanged and the reduced wing loading will give slower flight speeds but beware, you cant just go on increasing the wing area without an appropriate increase in the tail surfaces. Getting all this to work properly is the fun part of experimenting so keep going. On a historical note Slingsby made a version of their Dart 15 full size glider (I flew one!) to which you could add 1 metre wing tip extensions (adding about 10% extra area). It did not do much for the roll rate (the ailerons were unchanged) but it did allow it fly safely a few knots slower. Quote Link to comment Share on other sites More sharing options...
Jonathan Lewzey Posted February 1, 2009 Share Posted February 1, 2009 brushed motors. If you can, get a cheap brushless outrunner. The larger prop you'll be able to spin will act as an airbrake on landing approaches. The power will also be much better without being OTT (200W one). Quote Link to comment Share on other sites More sharing options...
Matt Jones Posted February 1, 2009 Share Posted February 1, 2009 Two things I'd add: 1) A control surface with a large chord moving through a small deflection is more efficient than a narrower surface with a greater deflection. 2) A friend had a slope model with full span ailerons. Over the winter he refurbished it splitting the aileron in half and making the inner portion flaps. The roll rate using just the outer ailerons is faster and crisper than the full span set up. Just goes to show how much drag the inner portion contributes. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 1, 2009 Share Posted February 1, 2009 sorry for what ? Quote Link to comment Share on other sites More sharing options...
Former Member Posted February 2, 2009 Share Posted February 2, 2009 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted February 2, 2009 Share Posted February 2, 2009 Quote Link to comment Share on other sites More sharing options...
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