Posts: 603
Joined: 8/12/2006 From: Fort Wayne,
IN, USA Status: offline
Hey guys, here is a couple of pics of mikes plane in electric form.
It has 6 A123's in it with a 2500 KV motor. It has an eflight 60 amp switching amp, and HS-65MG servos. Im going to move the tails out one rib, and mount them straight up as well. I have to figure out the fuse cooling, but as it turned out, I didn't have to build up the middle section so its going to come out flush with the wing, so it will have a flat hatch across the middle. If I had to do over again, I would widen the middle section 1/2 inch.
I will be running a 5.75x6 graupner speed cut down carbon prop, and trim it for load to burst around 75 amps. it should run pretty fast. I have used this power system with a 6x4 prop and it makes 80 ounzes of thrust in that config at 73 amps and 14 volts...about 1000 watts, so not too bad from 2300 mah batteries. With this config, it should fly 12 min with about 1/2 throttle and 10 speed passes.
My figures still come out with about 80 ounces of thrust but a higher prop speed at 30,000 rpm.....hopefully shooting for 150mph, but not sure....
< Message edited by gooseF22 -- 2/7/2008 3:59:25 AM >
Posts: 1339
Joined: 1/10/2002 From: Tulsa, OK, USA Status: offline
Those batteries look like a tight fit. The width of the center section was designed with a tuned muffler in mind. I guess you have considered turning the batteries the other way and extending them out to the 2nd rib? It looks like you should be able to build it very flat and clean. This should be a very affordable speed electric and I hope it works out well.
How did you come up with 80 oz of thrust? ThrustHP (for what it's worth) came up with less.
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Joined: 8/12/2006 From: Fort Wayne,
IN, USA Status: offline
quote:
ORIGINAL: Mike Connor
Those batteries look like a tight fit. The width of the center section was designed with a tuned muffler in mind. I guess you have considered turning the batteries the other way and extending them out to the 2nd rib? It looks like you should be able to build it very flat and clean. This should be a very affordable speed electric and I hope it works out well.
How did you come up with 80 oz of thrust? ThrustHP (for what it's worth) came up with less.
Using medusa's motorcalc. I backdoored my readings and made it work.
The A123's in 6S provide about 14.5 volts at 73 amps loaded measured from my last setup. put a 6 inch prop. the 123's provide as much current flow as a 6000mah battery.
At the speeds the diameter is very critical, a .25 inch difference can be amazing.
Everything will fit just fine, and I wanted to keep the wieght towards the center for crisp control since Im using 28 oz servos. I think it will work out good. If I cannot make the A123's work, I will have to build a 4s2P 4000 Kokam pack for it. The spar is right where the batteries need to mount, so I had to split the pack.
For the first time, I am having trouble welding one of the battery tabs back.....argh.....
Posts: 603
Joined: 8/12/2006 From: Fort Wayne,
IN, USA Status: offline
Mike I got things laid out today. I popped a tab off the battery by accident and I dont have a spot welder, so I have to make up a new 3pack...., Chad over at Sin City will reweld it later.
I got the 60 amp controller in there just by drilling a couple of holes.
The servo tops/arms will just stick up above the hatch.
The tails are going to be mounted further apart like an F-15. and Straight up. I want min turbulence in the back because of the teeny prop.
I used HS-65MG's with 28 oz torque and they will have good mechanical advantage. What did you use on low and high rates?
the plane balanced about .25 inch infront of the spar so far, it tends to be a touch nose heavy. I cannot move the batts very much. so I will have to weight it if necessary.
I will cowl in the motor and cut a cooling hole on top and carve out the top of the bulkhead former behind motor for cooling
I will cut an oval exit hole around the servo arms and it will double as exhaust in low pressure. I will maybe need a spoiler just in front, we will see...if so, a sanded piece of triangle stock
I dont have a band/jig saw, so the wingtips will be last.
we will likely put a thin carbon skid rail on the belly over the covering
I allowed for adding rudder later under outer skin
gettin there!! d
< Message edited by gooseF22 -- 2/8/2008 6:26:14 AM >
Posts: 1339
Joined: 1/10/2002 From: Tulsa, OK, USA Status: offline
The vertical fins should work fine mounted anywhere. There is a template on my site if you want to put them on the wing tips but your plans should look good. Rudders on winglets would be a pain. Reshaping the current fins is also OK but do not take off more the 10% of the area.
Elevon low rates is 1/4" and high rates is 3/8" with generous expo. high rates can be touchy at speed. Elevator low rates 3/8" and high rates is 5/8" with some expo. I would start with 1/2" elevator since yours will be a tad nose heavy. I would approach speed slowly to make sure your servos are strong enough. you will probably be fine using mechanical advantage with the short travel.
There are a few electric Demons on the works but you may be the first in the air. I like your affordable package and can't wait for a test flight.
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Joined: 8/12/2006 From: Fort Wayne,
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Thanks Im counting on the fact that the lack of pulsing of air requires less servo torque. so far that has been the case. the MG's seem pretty good for holding.
thanks. Im just going slowly due to my airline travel. Once I go to dayton next week and drop it off with my buddy builder, it will go faster.
Posts: 1339
Joined: 1/10/2002 From: Tulsa, OK, USA Status: offline
quote:
ORIGINAL: gooseF22
Im counting on the fact that the lack of pulsing of air requires less servo torque. so far that has been the case. the MG's seem pretty good for holding.
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