hunterisbest18
Senior Member
if my dad were to fly that it would be going in the window...lool
Scale Build-Off – RQ-7 Shadow
- Thread starter HilldaFlyer
- Start date
-
- Tags
- build fixed wing plane rq-7
ImJustWendy
Jackie of all trades, mis
Tail Feathers question.
If this has already been asked, then I apologize.
I'm building a bastardized 3-channel version of the RQ-7.
Stability and ease of flight is a priority as this will be a double duty, fun/trainer for my grandsons.
60" Armin wing 7.5" chord...why 7.5?
Lets just say I mis-measured when I layed out the first panel, so this is what it is...
15° dihedral to help with turning. even considered polyhedral.
This is my first attempt at using foam board construction techniques..going well so far but i kinda miss the old days of balsa.
I'm wanting to make this as quiet as I can, so am thinking EDF tucked inside the fuselage with top vent.
My worry has been having the motors thrust creating issues with the tail , so I decided on an inverted V hoping to alleviate this...?!?!
I'm kinda stuck right now trying to decide on the scale of the tail, size of the elevon control surfaces and length of the boom/oal of the plane.
I'd like to use some arrow shafts I already have that are cut to 28" length, could buy some carbon fiber tubes if it would be better?
Any advice, constructive criticism would be greatly appreciated.
If this has already been asked, then I apologize.
I'm building a bastardized 3-channel version of the RQ-7.
Stability and ease of flight is a priority as this will be a double duty, fun/trainer for my grandsons.
60" Armin wing 7.5" chord...why 7.5?
Lets just say I mis-measured when I layed out the first panel, so this is what it is...
15° dihedral to help with turning. even considered polyhedral.
This is my first attempt at using foam board construction techniques..going well so far but i kinda miss the old days of balsa.
I'm wanting to make this as quiet as I can, so am thinking EDF tucked inside the fuselage with top vent.
My worry has been having the motors thrust creating issues with the tail , so I decided on an inverted V hoping to alleviate this...?!?!
I'm kinda stuck right now trying to decide on the scale of the tail, size of the elevon control surfaces and length of the boom/oal of the plane.
I'd like to use some arrow shafts I already have that are cut to 28" length, could buy some carbon fiber tubes if it would be better?
Any advice, constructive criticism would be greatly appreciated.
Last edited:
Userofmuchtape&glue
Posted a thousand or more times
One thing, A EDF is not gonna be quiet! I don't think that would be the way to go, the flight times will be short and you wont have the low speed thrust you need. I reckon a low kv motor swinging a big prop is the way to go.
Sorry can't help you on your other queries!
Sorry can't help you on your other queries!
HilldaFlyer
Well-known member
Hi ImJustWendy!
Lots of good thoughts... First, I want you to know that if you met me you would know that I would never criticize or discourage anyone. I will, however, offer some advice and it is my intention to be helpful - so smile
. This may not be the best "trainer" plane since it likes to fly fast. But since your heart is already set, let's work through it. Increase the wing area to achieve slower flight (less wing loading)
EDF... Hmmm they offer more speed and lest torque, so it would be really hard to recover air speed after a mishap. They are loud as Userofmuchtape&glue has indicated. But they are cool. If you go this route, I'd recommend just leaving the nose of the the fuselage open for the intake. The flow of air around corners drastically reduces the flow. If you want quiet... then a big propeller spinning slowly is the key. But as you probably know, in a pusher configuration, the distance between the two tails will limit the propeller size.
The other piece of advice for a relatively new builder is something that I learned the hard way when I first started building. Build a plane to specifications... and then modify. If you modify the heck out of it off the bat and it doesn't fly, you have a handful of things that could be causing the lousy flight. It sounds like you are scaling this up a few sizes. I don't know if you are using my plans or someone else's. But the advice is still sound. Build to the plans, get the plane in the air and flying well - then modify to your heart's content changing one thing at a time.
Blowing air across the tail should not be a problem. As a matter of fact, I think it is good to keep the tail in the air flow because even at slow air speeds, blowing air across the tail control surfaces will give you control.
Now that I've reread your message a few times, it sound like you are scratch building a plane that has some structural similarities to the RQ-7, like the inverted "V" tail. I guess my advice is still good, but if you are not following any plans, then go for it. On the tail control surfaces, make them at least 1/3 the area of the tail to start with (or bigger). Don't monkey around with and EDF... it will be a total hassle for a beginner. Design the tail booms and put the largest propeller you can that fits between the booms. Then get a motor that drives that size prop with enough thrust to get the plane in the air.
For now, use the arrow shafts that you have. Make the tail boom as short as you can. With the motor behind the CG, all weight behind will have to be compensated by placing the battery forward. A really long tail will aggravate the balancing. The RQ-7 I built was to "scale" of the real deal... so that is why the tail is so long. It doesn't have to be that far away from the motor.
Ask more questions. Best of luck!
Lots of good thoughts... First, I want you to know that if you met me you would know that I would never criticize or discourage anyone. I will, however, offer some advice and it is my intention to be helpful - so smile
. This may not be the best "trainer" plane since it likes to fly fast. But since your heart is already set, let's work through it. Increase the wing area to achieve slower flight (less wing loading)EDF... Hmmm they offer more speed and lest torque, so it would be really hard to recover air speed after a mishap. They are loud as Userofmuchtape&glue has indicated. But they are cool. If you go this route, I'd recommend just leaving the nose of the the fuselage open for the intake. The flow of air around corners drastically reduces the flow. If you want quiet... then a big propeller spinning slowly is the key. But as you probably know, in a pusher configuration, the distance between the two tails will limit the propeller size.
The other piece of advice for a relatively new builder is something that I learned the hard way when I first started building. Build a plane to specifications... and then modify. If you modify the heck out of it off the bat and it doesn't fly, you have a handful of things that could be causing the lousy flight. It sounds like you are scaling this up a few sizes. I don't know if you are using my plans or someone else's. But the advice is still sound. Build to the plans, get the plane in the air and flying well - then modify to your heart's content changing one thing at a time.
Blowing air across the tail should not be a problem. As a matter of fact, I think it is good to keep the tail in the air flow because even at slow air speeds, blowing air across the tail control surfaces will give you control.
Now that I've reread your message a few times, it sound like you are scratch building a plane that has some structural similarities to the RQ-7, like the inverted "V" tail. I guess my advice is still good, but if you are not following any plans, then go for it. On the tail control surfaces, make them at least 1/3 the area of the tail to start with (or bigger). Don't monkey around with and EDF... it will be a total hassle for a beginner. Design the tail booms and put the largest propeller you can that fits between the booms. Then get a motor that drives that size prop with enough thrust to get the plane in the air.
For now, use the arrow shafts that you have. Make the tail boom as short as you can. With the motor behind the CG, all weight behind will have to be compensated by placing the battery forward. A really long tail will aggravate the balancing. The RQ-7 I built was to "scale" of the real deal... so that is why the tail is so long. It doesn't have to be that far away from the motor.
Ask more questions. Best of luck!
HilldaFlyer
Well-known member
Oh, Man! I thought I put them in this forum thread,,, but I couldn't find them
.They are in the build article.
