Help! F18 build
- Thread starter John 123
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John 123
Member
Thanks for the quick reply just ideas on how to strengthen the body of the plane and still keep room for air flow
Bo123
Elite member
Triangles.
John 123
Member
Started to cover the plane using parchment paper and glue
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leaded50
Legendary member
i suppose your idea is on the fuselage rear to front, not on the wing. Wing is easy reinforced with a CF rod/tube. On the fuselage.... a paintstick, CF rod/tube in center on top/ or bottom (or close too) would helped a lot. Even a buildt ridge on top. But dont forget, with the wing glued in that reinforce the fuselage much, specially when also have the LEX going forward that reinforce fuselage even more.
Bo123
Elite member
Leading edge extensions. Basically slats the extend the wing, and make it more lifty.
John 123
Member
Yes I understand. But to emplmemt them your get into a world of RC I don't know about about i just build them and hopefully fly them
John 123
Member
No but I seen it done Would be great to have the skills
Bo123
Elite member
John 123
Member
No but sure there is no harm in trying .I honestly don't know but if you have any ideas I'm open. Have you any experience with edfs would appreciate some help
John 123
Member
I have one question maybe you could answer it I have 2 70mm edfs identical. Can I run them off the one ESC the im using is a 60 A ESC and the battery im thinking of using is a 4S 1400 amp or do I have to go back to the drawing board 🤔
quorneng
Master member
john 123
The answer is NO!
The ESC 'reads' the individual pole position of a brushless motor as it passes each magnet to 'time' the next pulse to the next coil. At EDF rpm it is doing this hundreds of times a second. Two brushless motors on one ESC would confuse it completely so they would not run properly, if at all. Each brushless motor requires its own ESC.
To ensure you have the right battery size you really need to know what amps the EDF is drawing. The best way of doing this is to get yourself a Watt meter. It goes between the battery and EDF to measure accurately both the amps and the volts. From this you can work out if the battery is big enough for full power and how long it would be safe to fly for before the battery is discharged to the point of being permanently damaged.
Compared to props EDFs are pretty inefficient so the batteries have to work hard just to fly. Remember this is likely coupled with a 'jet' type airframe that is not the most aerodynamically efficient at model speeds.
So selecting the battery becomes a 'balancing act' to have it big enough to provide the power without being over stressed or being too heavy that over loads the plane!
The answer is NO!
The ESC 'reads' the individual pole position of a brushless motor as it passes each magnet to 'time' the next pulse to the next coil. At EDF rpm it is doing this hundreds of times a second. Two brushless motors on one ESC would confuse it completely so they would not run properly, if at all. Each brushless motor requires its own ESC.
To ensure you have the right battery size you really need to know what amps the EDF is drawing. The best way of doing this is to get yourself a Watt meter. It goes between the battery and EDF to measure accurately both the amps and the volts. From this you can work out if the battery is big enough for full power and how long it would be safe to fly for before the battery is discharged to the point of being permanently damaged.
Compared to props EDFs are pretty inefficient so the batteries have to work hard just to fly. Remember this is likely coupled with a 'jet' type airframe that is not the most aerodynamically efficient at model speeds.
So selecting the battery becomes a 'balancing act' to have it big enough to provide the power without being over stressed or being too heavy that over loads the plane!
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John 123
Member
Thanks very much this is the first time I got it explained to me like that cheers Looks like i need to invest more into the f18 . I will do what you say and hopefully get her airborne if not I have an 800kv brushless motor i could turn it into a prop pusher Thanks again for all your help if you have any more ideas please let me know Hope to keep in contact PS if you have built any jets with EDFs I would love to see them
quorneng
Master member
John 123
If you look in the 'EDF Power' section under 'Electric Aircraft' you will see examples of my latest 4 scale EDFs. They are all built of sheet foam and by most EDF standards are really light allowing the use of lower powered EDFs with relatively small batteries.
This my only plane that uses a true 70 mm EDF. It has a 2200mAh 3S LiPo
A single inlet with a long duct that divides into 6 individual exhausts.
Took a bit of experimentation to get it right. The sum of the areas of the exhausts matches the swept area of the 70 mm fan
It is perhaps worth remembering that an EDF is likely to be a much smaller diameter than a prop which means to generate anything like the same thrust it has to push the air out a good deal faster. Not only does this require more power to do but it also means the air inside is travelling much faster than the plane so the shape and smoothness of the duct is of considerable importance. The thrust is only generated at the point the air flow leaves the plane. Any obstruction or even a minor change of direction in the duct will tend to slow the air flow down before it even gets to the outside.
With an EDF the duct is everything both before and after the fan.
If you look in the 'EDF Power' section under 'Electric Aircraft' you will see examples of my latest 4 scale EDFs. They are all built of sheet foam and by most EDF standards are really light allowing the use of lower powered EDFs with relatively small batteries.
This my only plane that uses a true 70 mm EDF. It has a 2200mAh 3S LiPo
A single inlet with a long duct that divides into 6 individual exhausts.
Took a bit of experimentation to get it right. The sum of the areas of the exhausts matches the swept area of the 70 mm fan
It is perhaps worth remembering that an EDF is likely to be a much smaller diameter than a prop which means to generate anything like the same thrust it has to push the air out a good deal faster. Not only does this require more power to do but it also means the air inside is travelling much faster than the plane so the shape and smoothness of the duct is of considerable importance. The thrust is only generated at the point the air flow leaves the plane. Any obstruction or even a minor change of direction in the duct will tend to slow the air flow down before it even gets to the outside.
With an EDF the duct is everything both before and after the fan.
John 123
Member
You are clearly a very talented builder Would love to see more of your work. I think I've bitten off more than I can chew so I'm going to put a 800kv brushless motor on it and turn it into a prop pusher iv gone to far to stop now and I want to see it finished. But I still have the two EDFs I have the plans for a sabre so I might build it attest it only takes one EDF so I should be OK I hope . As soon as I start the build I'll post pictures and when I finish the F18 I'll post pictures aswell Thanks again for all your help hope to hear from you soon
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