Stumax Aircraft - SM89-45 EDF System

SM89-45 MkII EDF System

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The SM89-45 MkII EDF System has the same rotor as the original SM89-45 but with a new, lighter and stiffer shroud 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 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 4000W the TP Power 4040 series motors are an excellent choice, as are HET 700-68 series. Above 4000W we recommend the HET 700-83 series motors or TP Power 4050 series. The unit is extremely light at only 150g. Compared to the new SM89-40, the new SM89-45 MkII rotor blades are slightly wider, which means it requires more torque from the motor at the same rpm. This requires the use of a longer, heavier motor. The SM89-45 MkII now has a very lightweight carbon fibre shroud and the motor tube is now shorter and lighter. This reduces the unit weight to only 150g so 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 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:

10S 5000mAh lipos: 3600W
8S 5000mAh lipos: 2400W

With an HET 700-68-1400kV motor:

8S 5000mAh lipos: 3400W

With an HET 700-83-1080kV motor:

12S 5000mAh lipos: 5000W

With an HET 700-83-975kV motor:

12S 6000mAh lipos: 4400W (6.0kg thrust)

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 6.8" x 6" prop (Pconst = 1.2), 0m altitude and adjust the lipo size so that you get around 3.6V/cell under full load.