Stumax Aircraft - SM89-45 EDF System

SM89-40 EDF System

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The SM89-40 EDF System is an all new 89mm diameter EDF system which is designed to give maximum performance but at a more economical price compared to the original SM89-45. The rotor is a 1 piece injection moulding, made from long glass fibre reinforced Nylon, which means it's stiff and super tough. The aluminium motor tube is machined to suit 39mm motors (HET) or 40mm motors (TP Power, Neu, Leomotion etc). Please specify what motor you will be using. For power levels up to 3000W the HET 700-60 series motors are an excellent choice, as are TP Power 4030 series motors. Above 3000W we recommend the HET 700-68 series motors or TP Power 4040 series. The shroud is made from solid carbon fibre which provides a super stiff base in which to mount the glass fibre reinforced injection moulded 8 bladed stator assembly which is bonded to the motor tube with aerospace grade methyl-methacrylate adhesive. Carbon fibre mounting tabs are bonded to the outside of the shroud to provide a convenient mounting solution. The unit is extremely light at only 140g. Compared to the original SM89-45, the new SM89-40 rotor blades are slightly narrower, which means it requires less torque from the motor at the same rpm. This allows the use of a shorter, lighter motor. Combine this with the unit weight of only 140g and it's possible to build a very light and super efficient unit.

When deciding between the SM89-40 and SM89-45, putting cost and weight aside, the SM89-45 has slightly superior dynamic performance at very high power levels and is more suited to very high power levels up to 5kW. At lower power levels there's not much difference and the SM89-40 would be the first choice. Note that the performance figures below are for HET motors, plug and play units are now fitted with the equivalent TP Power motor.

Performance:

With an HET 700-68-1125kV motor:

12S 5000mAh lipos: 4200W
10S 5000mAh lipos: 2500W

With an HET 700-60-1400kV motor:

10S 5000mAh lipos: 4200W (too much for this motor!)
9S 5000mAh lipos: 3500W (pushing this motor hard)
8S 5000mAh lipos: 2600W

Note that these figures are taken on a test stand with a radiussed inlet lip and open exhaust. Your figures will be close but not exactly the same as a lot depends on the voltage your lipos deliver under load, the air temperature, humidity, altitude as well as inlet duct design and exhaust duct diameter. To get an idea of how other motors may work, use ecalc (www.ecalc.ch) and use a 6.12" x 6" prop (Pconst = 1.2), 0m altitude and adjust the lipo size so that you get around 3.6V/cell under full load.