Written by Don Slusarczyk
EDF's and Lipo Batteries
As seen in the Winter 2019 issue of Park Pilot
The Freewing Lippisch P.15 (freewing-model.com) is one of the latest PNP (Plug-N-Play) 64 mm EDF (electric ducted-fan) airplanes to come on the market that is great for park flying. I have been flying mine stock with a 3S 1,200 mAh LiPo battery. The light power-to-weight ratio makes it a nice-flying model that launches easily and lands rather slowly. Although the stock 300-watt power system is enough power for most pilots, I wanted to try an upgrade to improve sound and performance. I decided to try the FMS (fmsmodel.com) 11-blade 3,150 Kv 64 mm EDF unit. With 11 rotor blades instead of five, the sound should greatly improve.
The 3,150 Kv unit is intended for a 4S LiPo battery pack and will put out approximately 600 watts—twice that of stock. The extra power means an ESC upgrade is also required because of the higher amps on 4S power. I went with a Hobbywing SkyWalker Series 40-amp ESC (hobbywing.com) because it fit snugly into the existing slot in the fuselage without modification. To start the upgrade process, you will need to remove the stock fan unit. Removing it can be troublesome because it is glued into the fuselage. After the access hatch is removed, you must grab onto the EDF housing then wiggle and pull it to get it out. I found it helpful to use an X-Acto blade and cut along the perimeter of the EDF housing, just barely going into the foam. The object is to cut loose any excess glue that might be present and weaken the existing glue joint. After the fan unit is out, you will have to make a modification to the fuselage and the access hatch. If you compare the two EDF housings, you will see that the FMS housing is longer, so some foam needs to be removed to allow it to fit.
There are several ways to do this. One is by using an X-Acto knife to dig out small bits of foam. Another way is to use a Dremel tool with a spherical ball bit to remove the foam. As you remove the foam, keep checking the fit of the FMS unit in the fuselage and the fit on the hatch. You do not want the access hatch to squeeze the EDF housing and cause it to hit the rotor blades when installed.
When you have a good fit, glue the new unit in the fuselage. I like to use low-temperature hot-melt glue for installing EDF units.
After the unit is installed, I suggest opening up the outlet diameter going out the back of the fuselage. The outlet diameter at the back of the aircraft is sized correctly for the stock 64 mm power system, but it is slightly small for the FMS fan unit. I added a triangular foam wedge to open the outlet a little to maximize the thrust. The wedge is from scrap Depron sheet, and the width of the triangle at the outlet is 15 mm. To install it, use a new single-edge razor blade and cut into the fuselage starting directly behind the EDF unit. Use a ruler to ensure that you have a straight cut then gently spread out the foam until it accepts the triangle wedge. You want the foam wedge to be flush and smooth inside the ducting. I used two layers of 6 mm Depron and glued it in with Foamtak (auralex.com). When it was dry, I trimmed away the excess foam on the outside of the fuselage. The FMS setup is heavier than the stock fan unit, so a LiPo battery pack that is too small will not allow it to balance. I was able to get mine to balance with 4S 1,800 to 2,200 mAh LiPos. Lower-capacity packs can be used as long as the weight of the pack is nearly 190 grams.
Next, you will want to turn down the rates in your radio. This upgrade will fly slightly faster, so you might find your airplane a little twitchy, especially in a roll, if you keep the rates set the same as the lower power setup. Static thrust will be much higher than before on 4S power. I launch the Lippisch P.15 at full throttle, with the nose up approximately 45°, and give it a firm push forward. This airplane tends to pitch down on launch, and it still does that with the extra power, so be ready for it. When it is in the air, you should notice a faster flying speed and a different jetlike whoosh sound! The additional weight of the EDF and LiPo was not noticeable in the air because of the extra power. Landing speed had increased slightly, but slowly feeding in up-elevator made grass landings uneventful. A 4S 2,200 mAh LiPo battery pack offers approximately 3 minutes of full-throttle flying, or as much as 5 minutes with mixed throttle.
The Freewing Lippisch P.15 (freewing-model.com) is one of the latest PNP (Plug-N-Play) 64 mm EDF (electric ducted-fan) airplanes to come on the market that is great for park flying. I have been flying mine stock with a 3S 1,200 mAh LiPo battery. The light power-to-weight ratio makes it a nice-flying model that launches easily and lands rather slowly. Although the stock 300-watt power system is enough power for most pilots, I wanted to try an upgrade to improve sound and performance. I decided to try the FMS (fmsmodel.com) 11-blade 3,150 Kv 64 mm EDF unit. With 11 rotor blades instead of five, the sound should greatly improve.
The stock fan unit (L) has a five-blade rotor, while the FMS unit has 11 blades, resulting in a more realistic jetlike sound.
The 3,150 Kv unit is intended for a 4S LiPo battery pack and will put out approximately 600 watts—twice that of stock. The extra power means an ESC upgrade is also required because of the higher amps on 4S power. I went with a Hobbywing SkyWalker Series 40-amp ESC (hobbywing.com) because it fit snugly into the existing slot in the fuselage without modification. To start the upgrade process, you will need to remove the stock fan unit. Removing it can be troublesome because it is glued into the fuselage. After the access hatch is removed, you must grab onto the EDF housing then wiggle and pull it to get it out. I found it helpful to use an X-Acto blade and cut along the perimeter of the EDF housing, just barely going into the foam. The object is to cut loose any excess glue that might be present and weaken the existing glue joint. After the fan unit is out, you will have to make a modification to the fuselage and the access hatch. If you compare the two EDF housings, you will see that the FMS housing is longer, so some foam needs to be removed to allow it to fit.
The FMS unit (L) is longer and heavier than the stock fan unit, but it puts out twice the watts.
There are several ways to do this. One is by using an X-Acto knife to dig out small bits of foam. Another way is to use a Dremel tool with a spherical ball bit to remove the foam. As you remove the foam, keep checking the fit of the FMS unit in the fuselage and the fit on the hatch. You do not want the access hatch to squeeze the EDF housing and cause it to hit the rotor blades when installed.
Some foam needs to be removed to allow the longer housing on the FMS unit to fit correctly into the fuselage.
When you have a good fit, glue the new unit in the fuselage. I like to use low-temperature hot-melt glue for installing EDF units.
Low-temperature hot-melt glue allows the EDF unit to be quickly installed.
After the unit is installed, I suggest opening up the outlet diameter going out the back of the fuselage. The outlet diameter at the back of the aircraft is sized correctly for the stock 64 mm power system, but it is slightly small for the FMS fan unit. I added a triangular foam wedge to open the outlet a little to maximize the thrust. The wedge is from scrap Depron sheet, and the width of the triangle at the outlet is 15 mm. To install it, use a new single-edge razor blade and cut into the fuselage starting directly behind the EDF unit. Use a ruler to ensure that you have a straight cut then gently spread out the foam until it accepts the triangle wedge. You want the foam wedge to be flush and smooth inside the ducting. I used two layers of 6 mm Depron and glued it in with Foamtak (auralex.com). When it was dry, I trimmed away the excess foam on the outside of the fuselage. The FMS setup is heavier than the stock fan unit, so a LiPo battery pack that is too small will not allow it to balance. I was able to get mine to balance with 4S 1,800 to 2,200 mAh LiPos. Lower-capacity packs can be used as long as the weight of the pack is nearly 190 grams.
A 4S 2,200 mAh LiPo battery requires no modifications to fit in the cockpit area.
Next, you will want to turn down the rates in your radio. This upgrade will fly slightly faster, so you might find your airplane a little twitchy, especially in a roll, if you keep the rates set the same as the lower power setup. Static thrust will be much higher than before on 4S power. I launch the Lippisch P.15 at full throttle, with the nose up approximately 45°, and give it a firm push forward. This airplane tends to pitch down on launch, and it still does that with the extra power, so be ready for it. When it is in the air, you should notice a faster flying speed and a different jetlike whoosh sound! The additional weight of the EDF and LiPo was not noticeable in the air because of the extra power. Landing speed had increased slightly, but slowly feeding in up-elevator made grass landings uneventful. A 4S 2,200 mAh LiPo battery pack offers approximately 3 minutes of full-throttle flying, or as much as 5 minutes with mixed throttle.
