150+ mph electrostreak hotliner on a budget

[Ryan O.]

I got this motor meant for RC cars but similar in spec to those on 80mm 6s edfs for a speed plane and have no idea what size and pitch prop to use on it.
https://www.amazon.com/dp/B09WK1HCH2/?tag=lstir-20
I couldn’t find any prop-kv charts for inrunners and there are no manufacturer recommendations for this or similar motors and I wasn’t able to get prop calc to work. My guess is anywhere from a 6x9 to a 9x9 apc, but I don’t want to spend a bunch on different props, so just a ballpark is helpful.

 

[Fidget]

I also couldn't find something similar in an existing plane, which is my usual trick. Based on this 1950kv motor, I think I would start with 5x5 3-bladed prop. I would try that and measure amps with a multimeter. If that's not pushing the amps too high, try a 4 blade or go up to 6 inch. Clamp it down well as you test; it will also be a vicious finger cutting machine.

 

[Ryan O.]

I also couldn't find something similar in an existing plane, which is my usual trick. Based on this 1950kv motor, I think I would start with 5x5 3-bladed prop. I would try that and measure amps with a multimeter. If that's not pushing the amps too high, try a 4 blade or go up to 6 inch. Clamp it down well as you test; it will also be a vicious finger cutting machine.

I’ll try a 6” 2 blade then since 3 blades isn’t great for speed and it’s close enough resistance wise.

 

[Quinnyperks]

ask @FAI-F1D, he's done that type of stuff before for his deamons I believe.

 

[Ryan O.]

Old motor out, new motor in. I’ll update when I do prop tests. I ordered a bunch of apc props: 6x4.5, 6x5, 6x6, 6x7, 7x5, and 7x6 if I remember correctly.

 

[FAI-F1D]

Try a 7x6 APC to get started. If it stays reasonably safe on temperature, you can explore higher pitch, but stay at 7" diameter. If it gets hot, drop down to a 6.5x6.5 APC. Bear in mind these are glow props so you'll need a reamer to open up the hub for your spinner. I recommend Graupner spinners if you can find them.

A few other notes: don't move away from APC glow props. They're efficient and able to withstand the extremely high rpms these motors produce. On 6s with a 6.5x6.5 you're going to be dancing around 25k rpm. Don't skimp on escs or connectors. These things can suck a ton of current, easy to punch through 200A so a good esc and careful throttle management are critical. This is where a safety note comes into play: DO NOT power your electronics off the motor power battery. Disconnect the red wire going from your esc to the receiver and get a small BEC that will allow you to power the receiver off a 2s lipo around 500mah. Failure to do this isn't merely risky, it's negligent. These things blow up ESCs on occasion and then you've got an uncontrollable missile going who knows where. The BEC gives you control to get it down. That said, at the first sight of smoke, land NOW before the fire shorts your signal lead to the esc and kills the BEC battery. Don't ask how I know that...

 

[Ryan O.]

Try a 7x6 APC to get started. If it stays reasonably safe on temperature, you can explore higher pitch, but stay at 7" diameter. If it gets hot, drop down to a 6.5x6.5 APC. Bear in mind these are glow props so you'll need a reamer to open up the hub for your spinner. I recommend Graupner spinners if you can find them.

A few other notes: don't move away from APC glow props. They're efficient and able to withstand the extremely high rpms these motors produce. On 6s with a 6.5x6.5 you're going to be dancing around 25k rpm. Don't skimp on escs or connectors. These things can suck a ton of current, easy to punch through 200A so a good esc and careful throttle management are critical. This is where a safety note comes into play: DO NOT power your electronics off the motor power battery. Disconnect the red wire going from your esc to the receiver and get a small BEC that will allow you to power the receiver off a 2s lipo around 500mah. Failure to do this isn't merely risky, it's negligent. These things blow up ESCs on occasion and then you've got an uncontrollable missile going who knows where. The BEC gives you control to get it down. That said, at the first sight of smoke, land NOW before the fire shorts your signal lead to the esc and kills the BEC battery. Don't ask how I know that...

I’ve got a 800mah LiFe pack for receiver power that I managed to jam in there already. My main concern is ESC cooling since the ESC is behind the 2 1000mah 6s batteries, the leads were pretty long and I needed the nose weight. The picture is from before I added the receiver pack since it was just one less wire to deal with during servo setup.

I’ve got a great planes aluminum spinner, but if it ends up being too heavy or too flimsy I’ll swap it out for a graupner like you recommended. I’ve done short a static test running a 6x6 prop and everything was room temperature, so after the first flight on the 6” I can likely move up to a 7” if cooling ends up being alright.
There’s already another club member with an electrostreak that goes 150 with a big outrunner and a 9” prop, and I’ve made the necessary structural modifications (reinforced v-stab, dual aileron servos, and cutting the ailerons short to prevent flutter at the tip from wingtip vortexes).

 

[Ryan O.]

Try a 7x6 APC to get started. If it stays reasonably safe on temperature, you can explore higher pitch, but stay at 7" diameter. If it gets hot, drop down to a 6.5x6.5 APC. Bear in mind these are glow props so you'll need a reamer to open up the hub for your spinner. I recommend Graupner spinners if you can find them.

A few other notes: don't move away from APC glow props. They're efficient and able to withstand the extremely high rpms these motors produce. On 6s with a 6.5x6.5 you're going to be dancing around 25k rpm. Don't skimp on escs or connectors. These things can suck a ton of current, easy to punch through 200A so a good esc and careful throttle management are critical. This is where a safety note comes into play: DO NOT power your electronics off the motor power battery. Disconnect the red wire going from your esc to the receiver and get a small BEC that will allow you to power the receiver off a 2s lipo around 500mah. Failure to do this isn't merely risky, it's negligent. These things blow up ESCs on occasion and then you've got an uncontrollable missile going who knows where. The BEC gives you control to get it down. That said, at the first sight of smoke, land NOW before the fire shorts your signal lead to the esc and kills the BEC battery. Don't ask how I know that...

Own other thing, would you recommend using a set screw or collet prop adapter?

 

[Ryan O.]

First, about the original topic of the thread, I decided to do the maiden on a 7x5 prop instead of a 6x6. After the short flight I definitely think I can go up to a 7x6 or even a 7x7.

The plane flew great, cruising at around 1/8 throttle. I had already done a brief half throttle pass at about 95 and early into the following 2/3 throttle pass the vertical stabilizer failed at about 105 mph. I had already done minor reinforcements but it obviously wasn’t enough. The new tail will likely be solid balsa with pins going through the fuselage.

The v-stab actually stayed attached to the plane by the pull-pull system linkages and the electrostreak just wobbled around the sky until it hit a tree. I tried to turn away but it wasn’t able to maneuver at all. The plane’s not really that damaged at the moment, the electronics even worked. Only visible damage, besides the vertical stabilizer, is a chip in the wingtip.

Google drive links to video, they may or may not work.
https://drive.google.com/file/d/1jxkjioZAx6zwh0Y_vfKJAnGtq4_GYUn6/view
https://drive.google.com/file/d/14q-Qudh1GycI7-7QLZygKUqgGc-NE-Ur/view

 

[JetCrafts]

First, about the original topic of the thread, I decided to do the maiden on a 7x5 prop instead of a 6x6. After the short flight I definitely think I can go up to a 7x6 or even a 7x7.
View attachment 230519
The plane flew great, cruising at around 1/8 throttle. I had already done a brief half throttle pass at about 95 and early into the following 2/3 throttle pass the vertical stabilizer failed at about 105 mph. I had already done minor reinforcements but it obviously wasn’t enough. The new tail will likely be solid balsa with pins going through the fuselage. View attachment 230511 View attachment 230512 View attachment 230513 The v-stab actually stayed attached to the plane by the pull-pull system linkages and the electrostreak just wobbled around the sky until it hit a tree. I tried to turn away but it wasn’t able to maneuver at all. The plane’s not really that damaged at the moment, the electronics even worked. Only visible damage, besides the vertical stabilizer, is a chip in the wingtip.
View attachment 230514
Google drive links to video, they may or may not work.
https://drive.google.com/file/d/1jxkjioZAx6zwh0Y_vfKJAnGtq4_GYUn6/view
https://drive.google.com/file/d/14q-Qudh1GycI7-7QLZygKUqgGc-NE-Ur/view

potato cannon , potato cannon in true ft fashion

 

[FAI-F1D]

Electrostreak? Dang, what a classic! Definitely gonna need some reinforcing...you're *slightly* outside the design operating range.

I'm not a big fan of set screws. They work their way loose at the worst possible time. I figure if a collet can handle 12kW on the GM F5B folders, it's clearly the way to go.

ESC should always be forward of the batteries, for at least 3 reasons:

1. Shorter wires between motor and esc means less inductive interference, less resistance heat, and better efficiency.
2. Better cooling. Make sure you have a good cooling inlet or two and a good sized exhaust outlet aft of the batteries. Batteries are disposable. If they overheat, get new ones. HRB, Pulse, and GNB all seem able to handle extreme heat repeatedly without dying. There are others as well but those are my favorites so far.
3. Keeps the explodey component away from the control center.

 

[Ryan O.]

Electrostreak? Dang, what a classic! Definitely gonna need some reinforcing...you're *slightly* outside the design operating range.

I'm not a big fan of set screws. They work their way loose at the worst possible time. I figure if a collet can handle 12kW on the GM F5B folders, it's clearly the way to go.

ESC should always be forward of the batteries, for at least 3 reasons:

1. Shorter wires between motor and esc means less inductive interference, less resistance heat, and better efficiency.
2. Better cooling. Make sure you have a good cooling inlet or two and a good sized exhaust outlet aft of the batteries. Batteries are disposable. If they overheat, get new ones. HRB, Pulse, and GNB all seem able to handle extreme heat repeatedly without dying. There are others as well but those are my favorites so far.
3. Keeps the explodey component away from the control center.

For going only twice the designed speed it handled it pretty well. I copied the modifications from another guy at the field with a 150mph electrostreak, mostly around the wing ailerons. Seeing as it didn’t disintegrate from the g forces when the tail detached I’d guess the rest of the airframe is strong enough. The wing fell out of the tree already, according to another club member who picked it off the ground it was perfectly fine besides a chip in the wingtip.

 

[Ryan O.]

I picked up the wing and it looks decent, probably a third a days’ work to repair the cosmetic damage. The fuselage did shift a little in the tree, so hopefully it falls soon.

 

[Ryan O.]

It only took a nearby tornado, but Electrostreak finally fell out of the tree. All the batteries are dead, but besides that everything can be repaired or still works.

 

[JetCrafts]

woooooooooooooooooo

 

[Ryan O.]

I started to fix the electrostreak today and in about an hour and a half I got the servos replaced, motor reinstalled, and fuselage rebuilt. All that’s left is redoing the covering, building a new v-stab out of solid balsa this time, and recovering the wing. After rebuilding everything I don’t see any visible warps from the crash.

 

[MrClean]

Been a while since I flew mine. Kinda always thought the tail was a wee bit too much "Gentle Lady" like to go too fast but it scooted right along on a 10 cell car pack. Wasn't till I started mixing flaperons that I could get the landing speed at that weight down to reasonable. And Javelin launches, well those were just a hoot but also not necesary with just 10 degrees of flaperons. Course once you loose your tail feathers, theres only flaperons to work with isn't there.
Ahhhhh, the good old days.

 

[Ryan O.]

Everything’s patched up, so once I can get some balsa for the tail it’ll be ready to fly. I will likely have to put some weight in the nose because the solid balsa tail will be heavier than the built up one.

 

[MrClean]

Are you SURE you need the Vertical? I hear they're over rated. AND if you don't have one, can't lose it in the trees!

 

[MrClean]

I'm often complimented on my myrth.

I get a lot of stuff thrown at me too.

Life is about balance. Smile and dodge.