Thrust angle edf?

[tomlogan1]

Playing with the idea of a twin edf. Very simple box fuselage with elevons for control surfaces. Have two 50 mm edfs and thought it might make a fun project.

Does an EDF have any thrust angle requirementes like a propeller? Thanks.

 

[JetCrafts]

no

 

[Pieliker96]

no

Reason being as the left-turning tendencies are greatly reduced due to the decreased disk/slipstream area and lower rotational inertia

 

[CappyAmeric]

The vertical thrust angle is important as well as the thrust moment. Generally, the thrust should be straight in line. Also, if the thrust moment is large (low underslung, or high top mounted) you may get undesirable pitch (up or down). My first EDF design was a modified FT Goblin with a 64mm EDF on top of the fuselage. There was insufficient up elevator for overcoming the pitch down moment caused by the EDF at half power or greater.

 

[L Edge]

Experiences with dual EDF's based on thrust angles to determine.

1. EDF transport when trimmed and flown level, if you change thrust and the plane climbs or dives, then you need to add up or down angle to the mount. You also should try this in a vertical axis. I ended up increasing the wing angle by 1 1/2 degrees to fly level when I changed power..
2. In order for my SR-71 to fly good, had yaw problems with motor setup. Since no two motor/esc/EDF's fan are the same(set up used 1 battery source) I had a crappy pair, so changed motor which solved yaw problem.
3. Designed and built my own A-10 and using 2 thrust vectoring nozzle that change exhaust nozzle angles so I could get it to fly level and straight when changing thrust.

What you should do is when your ready to fly yours, do a static test. Go in a closed area, hold your plane vertical, add throttle until it begins to hover, do a real quick, release grab and see it it tends to yaw, pitch quickly. If it doesn't go out and try it.

I designed and built an EDF trainer with one 64mm EDF mounted above and ended with 3 degrees up and one degree towards the right to make it fly real good.

So to answer your question, maybe.

Are you putting rudder or differential thrust for yaw conditions?

 

[tomlogan1]

Experiences with dual EDF's based on thrust angles to determine.

1. EDF transport when trimmed and flown level, if you change thrust and the plane climbs or dives, then you need to add up or down angle to the mount. You also should try this in a vertical axis. I ended up increasing the wing angle by 1 1/2 degrees to fly level when I changed power..
2. In order for my SR-71 to fly good, had yaw problems with motor setup. Since no two motor/esc/EDF's fan are the same(set up used 1 battery source) I had a crappy pair, so changed motor which solved yaw problem.
3. Designed and built my own A-10 and using 2 thrust vectoring nozzle that change exhaust nozzle angles so I could get it to fly level and straight when changing thrust.

What you should do is when your ready to fly yours, do a static test. Go in a closed area, hold your plane vertical, add throttle until it begins to hover, do a real quick, release grab and see it it tends to yaw, pitch quickly. If it doesn't go out and try it.

I designed and built an EDF trainer with one 64mm EDF mounted above and ended with 3 degrees up and one degree towards the right to make it fly real good.

So to answer your question, maybe.

Are you putting rudder or differential thrust for yaw conditions?

Experiences with dual EDF's based on thrust angles to determine.

1. EDF transport when trimmed and flown level, if you change thrust and the plane climbs or dives, then you need to add up or down angle to the mount. You also should try this in a vertical axis. I ended up increasing the wing angle by 1 1/2 degrees to fly level when I changed power..
2. In order for my SR-71 to fly good, had yaw problems with motor setup. Since no two motor/esc/EDF's fan are the same(set up used 1 battery source) I had a crappy pair, so changed motor which solved yaw problem.
3. Designed and built my own A-10 and using 2 thrust vectoring nozzle that change exhaust nozzle angles so I could get it to fly level and straight when changing thrust.

What you should do is when your ready to fly yours, do a static test. Go in a closed area, hold your plane vertical, add throttle until it begins to hover, do a real quick, release grab and see it it tends to yaw, pitch quickly. If it doesn't go out and try it.

I designed and built an EDF trainer with one 64mm EDF mounted above and ended with 3 degrees up and one degree towards the right to make it fly real good.

So to answer your question, maybe.

Are you putting rudder or differential thrust for yaw conditions?

I couldn't do something simple so I set it up for elevons. No rudder, no differential thrust although I have done that on a prop twin only used it for taxi purposes.

 

[L Edge]

I couldn't do something simple so I set it up for elevons. No rudder, no differential thrust although I have done that on a prop twin only used it for taxi purposes.

I hope you produce a video when you maiden it. It is good to see someone explore the unknown.

 

[tomlogan1]

I hope you produce a video when you maiden it. It is good to see someone explore the unknown.

My career as an aircraft engineer is in jeopardy.

First attempt normal overhand throw resulted in a nose dive into the turf.
Second attempt throwing at more of an extreme angle produced an identical crash.
Third attempt to launch like a flying wing, throwing straight up, sort of an underhand toss had a brief moment of level flight ( about 10 feet) and it too, ended up as a lawn dart.

I presume the angle of the jets was incorrect. I placed then parallel to the fuselage at about the mid wing position. I feel that the thrust produced is sufficient for flight, perhaps not a speed demon but capable of continuous flight.

Will repair and try different engine placement

placement.

 

[leaded50]

correct, you get athrust angle problem also with a EDF, as on a prop. Here you have it on top of fuselage.. that would try push nose down (if set straight level as wing incident)

 

[tomlogan1]

A friend just sent some pictures of an He 162. Similar engine placement albeit a single. Would having two engines require a different angle than a single?

Thanks.

 

[leaded50]

A friend just sent some pictures of an He 162. Similar engine placement albeit a single. Would having two engines require a different angle than a single?

Thanks.

two, or one doesnt matter, it will just give effect of strength on the pitch movement. angle them a touch down in front, and it will be better flying. Many have found such, by edf/props on top... and also difference in pitch up or down (pitch down by edfs on top.) by giving throttle or not. Just think of what line you have on the "exhaust/thrust" vs the fuselage.

 

[CappyAmeric]

The problem looks like thrust moment. It looks like you have at least a couple of inches of arm between the center of the motors and the center of the fuselage - which means the forward force is rotating down, forcing the nose down. To counter act that moment, try tilting the motors down in the front.

Another issue is the fact that this thrust moment is on a flying wing which will often have an insufficient vertical arm (elevator) to counter the thrust moment if it exists as it does in this case. Another thought is to mount the wing on a fuselage with a horizontal stabilizer and elevator.

 

[CappyAmeric]

I had almost the same experience with a single 64mm EDF mounted on a FT Goblin.

 

[L Edge]

You might want to look at this model as a flying wing. Got a few suggestions to use your 2 EDF's. Mount the EDF's way in the back low, mount the battery high in your present fuse forward so the summation of forces and moments are zero. Elevator should have some uptrim. Will work.

 

[tomlogan1]

You might want to look at this model as a flying wing. Got a few suggestions to use your 2 EDF's. Mount the EDF's way in the back low, mount the battery high in your present fuse forward so the summation of forces and moments are zero. Elevator should have some uptrim. Will work.

Tried to mount the EDF's back by the vertical stabilizer but it made the plane very tail heavy. I suppose I could add weight to the front and move the EDF's back as you suggest. Worst case is I ruined 2 sheets of foamboard. I'll live.

 

[L Edge]

Since this is an experiment, you will need to tinker first round, that is, just use EDF's( chop off exhaust tubes to reduce weight) and move aft. Balance by putting battery in nose. Cg, battery and thrust line must be right to prevent your nose down attitude that you had. So hot glue it back together, make the changes and try it.

I have a different way of reducing damage when launching an "experimental" (power on) to see if it is nose or tail heavy if you care to hear it..

 

[Bifi.baarlo]

Try to take of from the grass, I always do that with my own design edf builds because edf planes often need more speed and because of that handlaunching is always a risk, if the thrust angle isn't correct, it can't nosedive in the ground but simply doesn't take of.