PatMc

I've demonstrated that it's the AoA not airspeed that's responsible for a stall by using a glider at a steep slope site. By taking the glider high & behind a ridge then diving - pulling out to fast flat flight & crossing the ridge dead into wind at about head height. Despite the fact that the glider is travelling much faster than it's normal trimmed speed & roughly flying S&L it will often stall as it meets the rising air from the slope. Ergo it's a high speed stall caused by a high AoA resulting from the angle of the local airstream.Edited By PatMc on 14/07/2009 18:55:23

The goods are often the same as sold by UK retailers with a different badge. Delivery is slower than most UK mail order but in my experience they seem are honest about stock levels & deliver within the period they specify.The way their postage is charged means it's usually best to consider making up the order to just within the charge band. If you can't or don't want to do that then it's worth considering a UK supplier.

Posted by Lee Bentley on 13/07/2009 19:22:05: Hi Timbo,   Thanks for input, I have a 14x8 prop on back order also a couple of 6S packs.   As a matter of interest, what are the rules when using a 3 blade prop. I have found a Graupner 3 blade but its a 12x8, can I use this instead of a 14x8 2 blade?      If it's to replace a 2 blade that is giving the correct speed then the same pitch should be used & the diameter reduced to give the same rpm but it will be less efficient. This site Martin Hepperle gives the way to calculate the equivalents. Using the formulae given - changing from 2 blade to 3 blade would be to multiply the original's dia by 0.904 & for a 2 blade to 4 blade multiply by 0.84.  So it's near enough to say that your  2B 14x8 should be replaced by a 3B 13x8. Of course as Martin Hepperle notes "these relations are valid only for propellers of the same family having similar blade shapes".  If a replacement prop gives the same rpm as the original the current draw & therefore watts will be the same.

Hi Lee, I have the instructions for the Hobbywing ESCs in pdf format. It's a scanned copy but reasonably readable. If you want a copy PM me with your email address - the file is just under 4MB.

I think you'd have to lower the thrust line quite a bit or dig out some foam from the top turtle deck to get the tank high enough.   Here's some  some sketches I did of mine that had an old Irvine 40 in it.   BTW I had no problems with an inverted motor but if you really don't like that a more practical alternative might be side mounted.  

With some ESCs you have to set the throttle range, the Hobbywing & various re-badged versions for example. Process is - switch on Tx move to full throttle > connect ESC wait about 2 seconds > "beep-beep" tone means throttle range high point has been recognized > move throttle stick to low - several "beeps" should be heard one for each cell in the battery > finaly a long "beep"  means the throttle low point has been confirmed. (For safety, this is best done with the prop removed first) AFAIK all Hobbywing from 40amp up ESCs  are rated up to 6s.   What brand is your ESC ?

Theoreticaly that motor will only do about 6720 rpm with no load & a fully charged 4s battery giving 4.2v per cell (16.8v). With a prop giving a 10C (40amps) load  your battery voltage will drop to about  14.2v -14.5v.  At best that's 580W & I estimate you could expect  no more than about 4200rpm. If you load to about the battery's max 15C the voltage would drop to around 12v - 12.5v & you'd get about 720W but not for very long. I agree with Bruce you will need 6s at least.   What size prop are you using & what's the volts & amps at full throttle ? Edited By Patrick McCauley on 12/07/2009 13:10:13