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Jul 11, 2019, 11:26 AM
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Abdullah Radwan's Avatar
No. I've contacted them by phone. They have a website but 10x3.8 doesn't exist there.

It looks like 9" prop is lost. I couldn't find it.

I can't get a 3S battery. It doesn't exist anywhere in Egypt. Actually, it draws almost the same amperage with 8x3.8 as 2S with 10x3.8 (11A for 3S vs 13A for 2S).
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Jul 11, 2019, 11:51 AM
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Quote:
Originally Posted by Abdullah Radwan
No. I've contacted them by phone. They have a website but 10x3.8 doesn't exist there.

It looks like 9" prop is lost. I couldn't find it.

I can't get a 3S battery. It doesn't exist anywhere in Egypt. Actually, it draws almost the same amperage with 8x3.8 as 2S with 10x3.8 (11A for 3S vs 13A for 2S).
How about this battery from this store in Cairo :
https://store.fut-electronics.com/co...v-2200-mah-35c
Jul 11, 2019, 12:54 PM
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Abdullah Radwan's Avatar
Quote:
Originally Posted by balsa or carbon
How about this battery from this store in Cairo :
https://store.fut-electronics.com/co...v-2200-mah-35c
This is actually the store where I purchased the 2S battery, and it has 10x3.8 prop.

I can't purchase it. It's very expensive for me.

I have 2 options for now:

Scale the plane down to work with 360g thrust provided by the 8x3.8 prop. I'll have more flight time, but higher stall speeds due to higher wing loading.

Use 10x3.8 prop with the standard size. I'll have half flight time when comparing with 8x3.8 but lower stall speed.

Which one is better?
Jul 11, 2019, 01:00 PM
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Quote:
Originally Posted by Abdullah Radwan
This is actually the store where I purchased the 2S battery, and it has 10x3.8 prop.

I can't purchase it. It's very expensive for me.

I have 2 options for now:

Scale the plane down to work with 360g thrust provided by the 8x3.8 prop. I'll have more flight time, but higher stall speeds due to higher wing loading.

Use 10x3.8 prop with the standard size. I'll have half flight time when comparing with 8x3.8 but lower stall speed.

Which one is better?
For learning to fly in a limited space , slower flight would be better ( learn to walk before you learn to run ) .
Jul 11, 2019, 01:21 PM
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Abdullah Radwan's Avatar
Ok. I'll build standard size Increased Wing Area Super Easy with 10x3.8 propeller. Thank you for your help.
Jul 11, 2019, 02:31 PM
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Quote:
Originally Posted by Abdullah Radwan
Ok. I'll build standard size Increased Wing Area Super Easy with 10x3.8 propeller. Thank you for your help.
Glad to help !

If you are planning to operate both elevators with one servo , a V pushrod works well ↓
And a quick easy way to strengthen the fuselage-to-wing joint is a fillet ↓
Jul 11, 2019, 04:05 PM
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Abdullah Radwan's Avatar
Thanks. I'll make a Y pushrod instead, as this is what I can make with materials I have (safety pins and wooden dowels).
A fillet strip is a good idea. I'll make it if I have some space after cutting the main parts.
Jul 11, 2019, 04:52 PM
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Quote:
Originally Posted by Abdullah Radwan
Thanks. I'll make a Y pushrod instead, as this is what I can make with materials I have (safety pins and wooden dowels).
A fillet strip is a good idea. I'll make it if I have some space after cutting the main parts.
OK , the fillet strip doesn't have to be all one piece ..... it can be several pieces joined end to end .
Jul 13, 2019, 12:38 AM
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Abdullah Radwan's Avatar
I've calculated the thrust again (Sorry ) for my motor (I was using another similar motor, but today I found values for my motor) and discovered that I'll have 470g thrust for 2S and 10x4.7 prop (I asked the store and they have it). That's low for IWA-SE. It'll work for 80% scaled SE (Not IWA) which will weight ~400g. The wing loading should be ~ 5.3 oz/sq.ft and the stall speed is ~17 km/h.

If I purchased 3S battery, it'll give ~620g thrust with an 8x3.8 prop. But I can't find cheap 3S anywhere. I'll contact the store to ask if they have their 1000mAh 3S battery back in stock.

EDIT: The wing loading is ~10.58 oz/sq.ft. The stall speed is ~26 km/h. The wrong values above were calculated for a constant chord wing.
Last edited by Abdullah Radwan; Jul 13, 2019 at 01:02 AM.
Jul 13, 2019, 01:37 AM
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Quote:
Originally Posted by Abdullah Radwan
I've calculated the thrust again (Sorry ) for my motor (I was using another similar motor, but today I found values for my motor) and discovered that I'll have 470g thrust for 2S and 10x4.7 prop (I asked the store and they have it). That's low for IWA-SE. It'll work for 80% scaled SE (Not IWA) which will weight ~400g. The wing loading should be ~ 5.3 oz/sq.ft and the stall speed is ~17 km/h.

If I purchased 3S battery, it'll give ~620g thrust with an 8x3.8 prop. But I can't find cheap 3S anywhere. I'll contact the store to ask if they have their 1000mAh 3S battery back in stock.

EDIT: The wing loading is ~10.58 oz/sq.ft. The stall speed is ~26 km/h. The wrong values above were calculated for a constant chord wing.
Here are a couple of crazy ideas :

Do you just have one 2S battery ? If you have two identical 2S batteries , you can connect them in series to make 4S . And you can cut an 8 inch prop down to 7 inch , just make sure you balance the prop after cutting it down .


Or you could make a 12v hot wire cutter to slice the heavy skins off of your foam board .
Jul 13, 2019, 02:02 AM
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Here's something you can try : build an SE airframe , and before you put any electronics on it .... do a few glide tests to see how it glides . You will need to balance it with some weight on the nose (battery?) , and position the elevators up about 1/4 inch for reflex .
If it has a nice glide , install a rudder servo for the rudder so you can make a gentle turn when it glides ...... and an elevator servo for the elevators so you can smooth out the landing . Then if everything goes well so far , install the motor/prop and go for it !
Jul 13, 2019, 11:04 AM
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Quote:
Originally Posted by Abdullah Radwan

If I purchased 3S battery, it'll give ~620g thrust with an 8x3.8 prop. But I can't find cheap 3S anywhere. I'll contact the store to ask if they have their 1000mAh 3S battery back in stock.
The store's website shows a 1S 1000mAh battery in stock . If that is accurate and it has the same C rating as your 2S battery , you could connect them in series to make a 3S battery .
https://store.fut-electronics.com/co...-3-7v-1000-mah
Last edited by balsa or carbon; Jul 13, 2019 at 11:09 AM.
Jul 13, 2019, 01:02 PM
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I've just purchased APC 10x4.7 prop from that store. It should give ~530g of thrust. Using a 90% scaled normal SE gives a weight ~450g. The stall speed is ~20 km/h. The wing loading is ~9.42 oz./sq.ft. The thrust to weight ratio is ~1.2.

The problem with connecting in series is charging. I don't have a single cell charger, and it doesn't come with JST-XH connector. So it's almost impossible to balance all cells.
Another major factor is that with 3S I'll overload the propeller. The maximum recommended RPM for an 8x3.8 prop is 8125 RPM, whereas with 3S it'll run with 9900 RPM.
Jul 13, 2019, 01:58 PM
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Quote:
Originally Posted by Abdullah Radwan
I've just purchased APC 10x4.7 prop from that store. It should give ~530g of thrust. Using a 90% scaled normal SE gives a weight ~450g. The stall speed is ~20 km/h. The wing loading is ~9.42 oz./sq.ft. The thrust to weight ratio is ~1.2.

The problem with connecting in series is charging. I don't have a single cell charger, and it doesn't come with JST-XH connector. So it's almost impossible to balance all cells.
Another major factor is that with 3S I'll overload the propeller. The maximum recommended RPM for an 8x3.8 prop is 8125 RPM, whereas with 3S it'll run with 9900 RPM.
OK , hopefully that will all work .

Have you begun the airframe construction yet ?

A 1S battery doesn't need balance charging because it only has one cell . Multiple cell batteries ( 2S , 3S , 4S , etc ) need balance charging to make sure each cell gets an equal charge ( 4.2v fully charged ) .
Jul 13, 2019, 03:03 PM
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A fellow in Bulgaria just built & flew a Super Easy , here is his post ( in another forum ) :

https://www.rcgroups.com/forums/show...5&postcount=48



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