DARoberts

I have built a .40 size long-ez which does not get off the ground. It has a Turnigy 5055 400 kv motor , a 4s 5000 maH battery, and a 11X7 prop. Can anyone have any suggestions to make this plane fly?

Thanks

D Roberts

Villa

Is the elevator on the canard wing? If yes, then please note that the elevator must go down for an up elevator command. On my Canard, a LOT of up elevator is required to rotate for take off.

JohnBuckner

My Feedback: (1)

Dittoos to what Villa said. I helped a fellow who showed up with one some years ago and it was a ripsnorting ground hugger. I noticed the elevator was backwards but he still argued about it but eventually he reversed the servo and the airplane was finally able to fly.

John

jbdismukes

My Feedback: (2)

Also, because there is no propwash flowing over the elevator, the control results only from airflow as the plane accelerates. Therefore, you need lots of runway to get up enough groundspeedto achieve rotation, especially if you're on grass.

DARoberts

The canard points down when it gets the up signal as opposed an elevator which points up and I was using an asphalt runway so I don't think that is the reason. I looked up the specs for the motor and it calls for a 13X8 prop so I think that it may just be underpropped. I replaced the wheels with larger ones and installed a 12X8 prop. that I have, but have not tried it yet. What do you think about a 3-bladed 12X8?

DR

JohnBuckner

My Feedback: (1)

This is not making much sense. If it truly is a forty sized airplane then calling for a 13x8 is completely out of the practical ballpark for a forty. I understand that you are attempting a coversion to electric. However if you are using an 11x7 and expect to go to a 12x8 worse 13X8 or even adding a third blade then that is going to be a liability on your electrical system.

I will defer prop suggestions to those electric enthusiast in the know. I do know that the Kit built Vari Eazy I test flew for the gentleman I Mentioned in my first post was some Kit that I do not recall and it called for a sixty one or more. This was around fifteen years ago and it had a .75 Super Tiger and needed all of it.

I hope this is not your first electric airplane. Its been my experiance choosing an unusual configuration to learn to do conversions on is a really bad idea.

John

Villa

Check the CG using an on line Canard CG calculator. Also, I have seen Canards with pusher props that could hardly get off the ground and were found to have the prop installed backwards. Sometimes this is hard to spot, since the plane will accelerated in what may appear to be normal, but will be putting out only about 75% thrust. Carefully look at the prop as it is mounted and view it as a wing that happens to be rotating. On the prop, the blunt side of the "wing" is the leading edge, the sharp end of the "wing" is the trailing edge, and the "top of the wing" must be in the direction the plane is traveling.

scooterinvegas

My Feedback: (1)

Just punched some numbers into my calculator and it looks like the 11x7 / 400Kv / 4 cell is only giving 25-30 oz of thrust @ 37-40 mph.

Need more RPM. Bigger battery & prop. 13 x 8 prop on 6 cells

DARoberts

The motor specification calls for the 13X8 prop.  It also said that the motor thrust is compatible to a .46 to .60  and should fly a 7 to 8 lb plane so i thought it would work on a 40 size plane.  I am not using a pusher prop, I just reversed the motor so Villa may be correct.  I put bigger wheels on it to increase the clearance and it will take a 12 inch prop fine but have not tested that yet.  If anyone has any suggestions for a motor-battery setup I would be interested in hearing from you.  If worse comes to worse, it won't be too difficult to put a glow engine in it.

Thanks for the suggestions.

D Roberts

JohnBuckner

My Feedback: (1)

Bingo! and better not use some 46 better make it a minimum of a 61 but even that will not pull a 13x8. Do research props though as suitable pusher prop selection will be limited.

John

Villa

Hi DARoberts
Please read this and my last post very carefully. You stated you are not using a pusher prop and that you just reversed the motor rotation. Stop right there. Now take the prop off and, turn it over, and re-mounted it so the mounting surface is now reversed. You do not need a pusher prop if you can reversed the direction the device rotates, and also reverse the prop mounting. Please read my last post until you can "see" the leading edge of the prop, the trailing edge of the prop, and the "top" surface of the prop. This can be a little complicated, but once you do understand it, you will have something useful forever, and you may be able to help others. Your plane may now take off, but I have no suggestion on prop size. I used to take off my Pusher/Puller twin engine with two .28 Magnum engines, using only one engine. I learned how to take off an underpowered plane.

DARoberts

Thanks, Villa,  I will check all of this out before I install a 4-stroke .52 in it.

D Roberts

Galand

I just bought one and want to convert to electric.
How did this test go?