qd25

Hi Guys i really love this plane it looks like it's doing 100mph when it's standing still [sm=wink_smile.gif] i want to do an electric one are there any forums on them
Thanks

supersparky

My Feedback: (21)

This plane does 140 I know because I've seen it. A friends airplane, very clean set up macs pipe fully enclosed 55 ax on 15% cool power 9x9 apc full throtal pass after 100-150 ft dive @30-45 degree angle with a light tail wind we saw 141.7 an radar. Yes I know thats a little bit cheating and ground speed not air speed but we were still getting 125-130mph up wind passes.

r-c-guy

My Feedback: (37)

I have one with an eflite 60 outrunner, 13x13 apc, and 8 cells which was radar times at 139 upwind. No other mods....

z06kal

139? No way. Not on a 400kv motor on 8S not enough watts to push a 13x13 to 140mph pitch speed. At best it is about 118mph pitch speed with a few percent slip after that maybe 115mph level. I run the APC pattern 13x13 (which is now a discontinued pattern prop and the only 13x13 APC) on 12 cells on a 300kv motor and it is barely in the 130's pitch speed speed wise. It tachs 11,100 which is mid 130's pitch speed. I pull 70 amps at 12S voltage and about 2500 watts. This pushes my minnow to about 122mph level on the prospeed CR1K radar gun.

JEFFRO503

My Feedback: (9)

Guys....I'm glad i stumbled across this thread! It seems i have a similar project that i'm trying to figure out what Motor/ESC and batteries to run in it. I have a Cermark alley cat ( 63" wingspan) and it's supposed to come in around 6.5 - 7lbs. I have a Jett .90 for it right now , but am going to sell it , and go electric. I have spoken to Dub Jett , and he said i would be aiming at being able to spin a 11X7 to 12X6 prop at about 14,000 on the ground , since the motor will unload in the air.

What kind of an electric setup should i be looking for to move a 7lb aircraft ( the Alley cat). Dub also said i could reach speeds of around 130 -150 on down lines if i have the motor tuned properly. I'm just looking for ideas on what could pull my Alley cat arounbd like that on an electric setup.

combatpigg

My Feedback: (3)

A 6 pitch prop needs to turn 18,000 to give you 100 mph pitch speed. By the time you add for unloading and subtract for drag, it is a wash. The rpm / prop numbers you were given sound way too conservative to acheive those speeds. To come close to 140 mph with a 6 pitch prop the engine has to turn about 25,000 rpm.

JEFFRO503

My Feedback: (9)

Just so i know....what is the equation everyone uses to figure out how fast a plane with go , a certain pitch prop. I know some of the little Jett .50 pylon birds are getting about 160mph ( or faster) but their motors are turning around 19,000 - 20,000 rpm........so how does that work?

Also.....what about using something like a high KV Scorpion motor.....something like one of the big heli motors that are in the 1,500 - 2,000 KV range....or possibly something a little more? Like i said , i'm just trying to figure out how to get my Allet can up to those speeds. Crap , i'd be happy with 120-130mph if i could get it.

combatpigg

My Feedback: (3)

The long handed version is what I use, but the multiplied steps can be combined to reduce steps.

6" pitch x 18,000 rpm =108,000 inches per minute

108,000 x 60 = 6,480,000 inches per hour

6,480,000 / 12 = 540,000 feet per hour

540,000 / 5280 = 102 mph

chalmrast

My Feedback: (1)

I have no doubt the gasser in the video in the first post is going claimed speed based on how it looks compared to my Kyosho Kelly.

I am running the Kelly on a 6S setup with a 12x12 prop. The motor is Scorpion 4025-10. ScorpionCalc shows a pitch speed of 110mph. I don't have a tach to check but ScorpionCalc is usually pretty close with my readings for amps & watts.

I have dopplered my plane (admittedly not the best audio samples) at 105-110 and that seems right based on the setup.

The only electric I've seen surpass 140 in this type ARF is a Kelly setup on 12S using a Neu high-kV motor.


[youtube]http://www.youtube.com/watch?v=8fQKu3fgux4[/youtube]

2000redrocket

wow. i think my h9 pts p51@ 117 on gps on the flat is fast. now i need to play with props. how many rpms does a engine usually pick up level in the air from still on the ground. my tower hobbies .61 sounds like it is screaming with a 11x7. i have a 11x8 to try next.
i could not believe the difference when i put it in. i am going to get the th.75 next for our enforcer. i may transplant my th.61 from the stang to the enforcer to see if it is better than the thunder tiger .91. it went the same speed with a old .61 and a 11x6 pusher as with the new .91