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Old 03-18-2014, 02:34 AM   #1
Dave180
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Default Ace Guppy

I was looking for a light quick building airplane and decided to try this even though it's for a beginner. Very easy to build and cheap. Mods will be front motor instead of power pod and fully functional tail instead of rudder only. The kit version was foam wing but the free online plan version is balsa. The Guppy fuse looks more like a Polywog so I trimmed some of the fat off the bottom and then added more material towards to back for servos. I'll build two wings for this. I'll try the original and see if even works, then later I'll shrink the wing on my super decathlon and put it on. Should weigh between 6.5-7.5 oz depending on battery size.
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Old 03-18-2014, 12:09 PM   #2
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Interesting,I'm watching this one.What's the wingspan on it?

Robin
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Old 03-18-2014, 04:11 PM   #3
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The wingspan printed out at 35.5" even though the plans say 34". Fuse length is 22.5"
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Old 03-22-2014, 07:37 AM   #4
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The fish is done. Weighs 5.7oz with no battery. I didn't use 1/16" for the tail. Too thin for me. I used 1/8" sanded down to 3/32. with real hinges. Its a pretty neat little airplane. Still need to test the motor.
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Old 03-22-2014, 09:56 AM   #5
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Very Very Nice Plane and Build I get to do the Maiden Flight on it LOL


I may be getting Older, But I Refuse to grow Up I am Having to much Fun to Grow Up LOL
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Old 03-24-2014, 08:29 PM   #6
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Thanks. I did fly it today. It stalls way too easy. I'll try some tip washout if the microlite covering can do that. Maybe 1/4"? The motor is under specs! It's pretty wimpy. It barely climbs. Prop is 6x3 gws only pulling around 3amps, 4oz of thrust.
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Old 03-24-2014, 09:19 PM   #7
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Originally Posted by Dave180 View Post
Thanks. I did fly it today. It stalls way too easy. I'll try some tip washout if the microlite covering can do that. Maybe 1/4"? The motor is under specs! It's pretty wimpy. It barely climbs. Prop is 6x3 gws only pulling around 3amps, 4oz of thrust.
I think with a more powerful Motor that the tip stall will go away, here is a Powerful 1800kv Micro motor that will do the job, its only about $6.95, use a 25 amp ESC and a 7x6 APC prop and a 1500mah 3 cell 25C lipo.

Here is a video of the power this 1800kv micro motor has with a 7x6 apc prop on 3 cells, this motor is capable of drawing 20+ amps, it has thick windings, I pull 20= amps all the time with them, they love it



https://www.hobbyking.com/hobbyking/...cro_Motor.html

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Old 03-24-2014, 09:29 PM   #8
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Its suppose to be a glider though. I have an 800 2s battery. So just looking for the most economy setup.
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Old 03-24-2014, 09:34 PM   #9
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Originally Posted by Dave180 View Post
Its suppose to be a glider though. I have an 800 2s battery. So just looking for the most economy setup.
You Dont have to use all the power, but its there if you need it throw a 3 cell in it best to power your Planes with a 1 to 1 power ratio to get you out of trouble if needed, 2 to 1 is even better under powered plane cause more problems, if it gets caught in a thermal or wind gust, you can power out of it. rather than loosing it.

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Old 03-24-2014, 10:36 PM   #10
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Well... tip stall is going to be related to airspeed and AOA. If it has the issue then it will have that issue any time you are entering a stall.
More power will only help stay at an airspeed above minimum to avoid stall. It won't affect the "character" of the stall when it happens.

Washout will affect how the aircraft behaves when it stalls. The basic idea being to have the tips at a lower AOA, thus stalling later than the wing root and helping any stall to be more likely to maintain the commanded heading, especially if straight ahead.

**********

A powered sailplane should generally have enough power to climb rapidly for fast ascent, shut-down (or reduce) power and then enjoy the extended glide capability. If its struggling to climb... its no fun.

Having more power available is not contrary to the desired performance of a powered sailplane. Many contest setups have ability to climb vertically at the max airspeed the wings can withstand.

*********

Power also has little to do with ability to exit a thermal or deal with wind gusts. I have flown sailplanes that have little of either capability such as the Gentle Lady... and I have flown 18 oz, 46 inch span "Ridge Racers", capable of in excess of 150 mph as pure sailplanes. The ridge racers obviously had no issues with gusts or diving vertically to get out of a thermal.
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Old 03-24-2014, 11:52 PM   #11
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Thanks. Good to know. I'll try the wing tip washout so at least maybe it won't barrel roll into the ground on landing.
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Old 03-25-2014, 12:10 AM   #12
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It sounds like to me that you are just Flying a little above the Stall Speed of your plane, it will barely climb, wash out may help to make it fly at a little slower speed before it tip stalls, but Really, You need more Power not Washout, your plane should briskly climb not barely climb, Give it more power, thats the answer to your problems. Hope that helps, Chellie

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Old 03-25-2014, 12:32 AM   #13
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Right. Its a park flyer. I'm trying to make a slow stick out of it.
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Old 03-28-2014, 04:30 AM   #14
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This motor is 2x the power of the smaller one, they claim. Its twice as heavy though. The advertised weight of .6oz was really .8oz with wires. It's a power-up 250 sport 2300kv.
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Old 03-29-2014, 03:24 AM   #15
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Let me show you something stupid about the new motor I just got. They machined just about all the area off the "tube" that slides in the mount and just left 1mm on each side for fit. Sure its better for the set screw and it won't pull out but it has excessive side play. Stupid!!!! I will be adding glue to the inside of the tube and try to get a tighter fit. Note how the silver motor didn't do that.
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Old 03-29-2014, 05:09 AM   #16
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The Ca glue seemed to work for right now. A very tight fit. Got threadlock on the set screws. Hope it works.
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Old 03-29-2014, 11:31 AM   #17
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I'm with Chellie ... maybe not so far as 1:1 ... 2:1 .... but certainly I hate marginal power.

The model in photo has medium aspect ratio tail and wing ... OP says a Glider with power ........ that means you cannot fly it as a pure power model nose up at level. She needs nose down slightly as in gliding. To keep speed up, airflow smooth over surfaces etc. (Assuming a normal incidence of wing / tail).

Second as aspect ratio increases ... ie span increases and chord less - the tips have more effect and wash-out gets more important.

A 35.5" span model on a 6x3 prop ? Only a floater in my book at that size would be on such low thrust prop.

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Old 03-29-2014, 01:46 PM   #18
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Thanks for commenting. The original prop was a 4x2.5 on the plans. I have a 7x3.5 I might cut down later. Not too many size choices on the lightweight GWS props. It's ok if its just a floater but it seemed to glide ok. It was kind of too calm last time. Wind kept shifting. I'll post a video later when it's worthy. I can always change the wing if this one's a lemon.
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Old 03-30-2014, 04:03 AM   #19
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Motor works as advertised in the specs. So thats good. 9-10oz thrust at 7 amps for 8oz plane. I was figuring maybe I'll get 20min flights if I pulse and glide.
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Old 03-31-2014, 04:00 AM   #20
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I'm a great believer in Pitch factor ...

KV x Pitch.

It has no technical Theory base ... but purely a factor I devised for my own use to decide on motor / prop combo for models. I do not use less than 3S packs so - if a 2S - then the factor needs to be pitch x 1.333

My J3 Cub uses a 7x5 on a 1350kv motor :
5 x 1350 = 6750 for 3S,

If I was to use 2S = (5 x 1.333) x 1350 = 8998

My Mig 3 uses a 10x6 on a 1000kv motor :
6 x 1000 = 6000 for 3S

If I was to use 2S = (6 x 1.333) x 1000 = 7998

This gives me good sunday sport flying with cruise throttle of 60 - 70%.

Diameter is based on type of model and drag profile. I decide on Pitch and then diameter is chosen based on 'eye-ball look' and other similar models.

Very unscientific, but it works.

My reasoning is : Thrust is fine but it only provides acceleration similar to HP / Torque of a car. Pitch gives speed similar to final drive ratio of a car.

Now Dave you have a 6x3 on a 2300kv motor with 2S ...

3 x 2300 = 6900 ... a good Pitch factor on 3S

but my system says you need a prop that is 1.333x the pitch if you want to use 2S ... so 3 x 1.333 = 4.

So try a 6x4 prop. Or stick a 3S pack in.

For those skeptics ..... take a look at your successful models and do the maths ... I bet a good sunday sport model is sitting around the 6000 - 7000 Pitch factor on 3S and 8000 - 9000 Pitch factor on 2S ...

If you are into SPEED - then the factor rises dramatically into the 15000+ region ... but that indicates an extreme amp load situation.

Dave - you quote 3A on 4oz thrust ... if that is on a 2300kv motor - then to me that indicates a very low power motor not capable of rpm sufficient to give enough output.
A 35" span floater model ... I would be looking for a figure of sub 10A ... a prop of 7" diameter ... if you want thrust, sunday sport flying. A higher pitch 6" prop if you want to give it some speed.

My thoughts.

Nigel

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Old 03-31-2014, 05:32 AM   #21
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The 3A on 4oz thrust was a 2000kv motor I removed. (18mm diameter). I have a 6x4 apc prop but the hub doesn't fit on the prop saver. The whole reason why I picked that motor in the first place was because of this plane which is basically the same plane and uses the dime size motor:
http://www.mountainmodels.com/produc...roducts_id=718

But obviously my plane is heavier and it doesn't work.
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Old 03-31-2014, 06:29 AM   #22
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If the APC prop is anything like the HK APC style ones I use ... they come with two set's of adaptor rings on the plastic mould. One set has greater OUTER diameter than the others - as one set is for back hub and other for front of hub use ... so you should be able to fit to a prop saver ...

It took me a while to realise this !!

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Old 03-31-2014, 06:42 AM   #23
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My apc props only have 2 choices for rings. HK apc props looks like it has 6 choices. That sucks.
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Old 03-31-2014, 06:54 AM   #24
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Originally Posted by Dave180 View Post
My apc props only have 2 choices for rings. HK apc props looks like it has 6 choices. That sucks.
But HK's are very brittle so they don't like catching anything !!

Nigel

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Old 04-02-2014, 03:38 AM   #25
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I now have a 6x3.5 cut down from the 7" gws prop. The blades are stiffer then the 6x3 which is very flimsy. Slightly wider too.
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