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Help needed with toy store foamie glider rc edf conversion

Old 11-03-2018, 03:39 PM
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Jimigunne
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Default Help needed with toy store foamie glider rc edf conversion

I am converting a foamie glider with 48in wingspan (swept) that hobby lobby sells--- i think wal mart, too--- to electric rc. Its for flying in a grass park. So no wheels, it will just belly in. With elev and rudder servos and flysky 6 ch receiver, it weighs 16 oz. I installed an edf motor on top of fuselage at about center of gravity so dont have to worry about prop damage. It's a qf2611-4500kv 64mm, 26.5 gram thrust edf on top with a 2200mah 3s lipo battery. The battery, edf and 35 amp esc weigh about 10.5 ounces. Well this proved to be WAY underpowered. When hand launched at full throttle it just dropped like a rock! I think even switching to an 1100 mah pak, it wont fly! I am trying to fly model with total weight of 26.5 oz with a 26 gram thrust edf? No wonder. Looked up the actual thrust spec after attempted hand launch, no wonder it didnt fly.
What edf and lipo batt do i need for goodhand launched performance?
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Old 11-03-2018, 07:18 PM
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solentlife
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A reasonable 64mm EDF should fly such a beast ... and you have 1:1 thrust ratio IF you are getting the 26oz from the EDF unit.

If its an AEO unit or similar ... then they are always extremely optimistic on their ratings.

Did you hand launch this glider before conversion ? Set all neutral ... then launch - see what she does (over soft tall grass of course) ...

26.5oz ... 740gr for me ! Is I think at the top weight range for such size .. but you should get some flight from it.

Don't forget though ... you have introduced thrust above the fuselage datum line ... this is probably causing her to pitch down.... we used to see this with pylon mounted props on flat field soarers when modified.
EDF route is the heaviest and worst form you could choose to be honest. More easy and lighter would be a pylon mounted prop ... eg 6x5 on a 2200kv - that would run on a small 1000 - 1300 LiPo ...

Do you have any link to the shop pictures of the glider and as modified by you ... that might help us ..

Nigel
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Old 11-03-2018, 08:21 PM
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quorneng
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I can only endorse what solentlife has said.
Even a small prop set up is at least twice as efficient as an EDF (same thrust for 1/2 the weight or twice the thrust for the same weight).
A 'big' prop set up is about 4 times better!

This is my 40" 'Lightweight Tractor'
Name:  NewFuseFin.JPG
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Ailerons and elevator only.
With a small 24 g (1oz) motor, a 7x4 prop and a 850 mAh 3s LiPo it weighs just under 10 oz ready to go.
Aerobatic it has unlimited vertical capability yet with a 'cruising' endurance of close to an hour.
First flew in 2015 and it is still on its original prop.

Your foamy glider would not be quite so light but with the same sort of motor set up it would still have a considerable performance.
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Old 11-04-2018, 02:31 AM
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Stick Dude
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Good looking bird! I like its simplicity!
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Old 11-04-2018, 10:33 AM
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Jimigunne
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Yea, i will switch from edf to prop. I already have a 1100 mah 3c lipo. What would be a good source for prop and 2200 kv motor? I am not familiar with that term datum line....is it the same as cg?
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Old 11-04-2018, 12:47 PM
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quorneng
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Its not so much the kV that controls things but the estimated weight of the plane.
Lets say you aim for 20 oz (1.25 lbs) all up.
As your plane is basically a glider 100W/lb should be a perfectly adequate power to weight ratio, particularly with an 'efficient' motor/prop set up.
A 125W motor can be pretty small and light.
https://hobbyking.com/en_us/d2822-14...___store=en_us
Hobbyking recommend an 7x3.5 prop for 3s. It will give at least 400g (14 oz) thrust with the prop mounted on the nose.
It will draw about 15A at full power so a 1100 mAh battery would not be stressed and it would also give you a considerable part throttle endurance.

Well that's the sort of thinking I would use if I was going to do it.
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Old 11-04-2018, 01:03 PM
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solentlife
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Originally Posted by Jimigunne View Post
Yea, i will switch from edf to prop. I already have a 1100 mah 3c lipo. What would be a good source for prop and 2200 kv motor? I am not familiar with that term datum line....is it the same as cg?
Hobby King or RC Timer are good sources if outside USA.

I suggested 2200kv motor because its a motor that can punch out good power but keeping prop small... 6x4 .. 6x5 on 3S...

https://hobbyking.com/en_us/d2826-6-...ner-motor.html

Another motor is the Floaterjet motor .. less KV - but excellent for this job ... again on a 6x4 or 7x3.5 .... I actually have twin Floaterjet motors on my TU144 cartoon jet ... its heavy - but she flies well...

https://hobbyking.com/en_us/floater-...2208-2150.html

My ASW28 ... 2m span and about similar weight at about 700gr all up - has a 32xx size motor but low KV and folding 10x6 prop ... on anything more than 60% throttle she climbs rapidly ... (fitted by manufacturer !)

Datum line is the line drawn horizontally along the fuselage that represents the level that flight forces balance out ...

Where the line vertically through CoG crosses the Datum line, is where the model actually pivots in pitch.
You can now see that placing motive thrust above causes the model to nose DOWN unless sufficient angle of motor is built in to compensate. If you view a motor pylon glider - you will see a significant angle is needed.

It is also why most aircraft have their engines mounted in line with fuselage ...

Nigel
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Old 11-04-2018, 06:07 PM
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Stick Dude
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And there we have it. In 1-1 scale aircraft I was schooled on different air foil plan views, chords, shapes and efficiency's. Long glider like wings only need a propulsion unit to get it in the air, then you switch it off, and let the long wings and ground thermals do its job. For full out jammin' and rockin' and rolling, pylon racer aircraft with my favorite air foil, the chocolate bar< Hershey's, cant be beat, but you do need power on for maximum effect. Below is one my pop's had in the 80' and yeup it had a V.W. engine to let it scream in the air!
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Old 11-05-2018, 09:03 AM
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Jimigunne
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Well i will fabricate a pylon from sheet aluminum. I guess the degrees of upward angle is just something that has to be guestimated. Of course i am switching to 1100 mah lipo 3s since that pack is around half the weight. Thanks for your help!
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Old 11-05-2018, 09:21 AM
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solentlife
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Originally Posted by Jimigunne View Post
Well i will fabricate a pylon from sheet aluminum. I guess the degrees of upward angle is just something that has to be guestimated. Of course i am switching to 1100 mah lipo 3s since that pack is around half the weight. Thanks for your help!
Google round for side views of such as Bixler ... Floaterjet ... any glider based model with pylon engine ...

Personally I would look at a rubber band mounted ply pylon ... not metal. The damage metal pylon would do instead of breaking in event of 'error' ??

Topics :

https://www.rcgroups.com/forums/show...r-thrust-angle

https://www.rcgroups.com/forums/show...wing-motor-pod

https://www.rcgroups.com/forums/show...ative-factor-s

https://www.rcgroups.com/forums/show...p-down-or-what

Worth looking through those threads ... they are discussion threads so give out various ideas and thoughts ...

Nigel
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