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Old Oct 21, 2012, 11:59 PM
Lee
PERFECT LANDING !!!
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USA, UT, Orem
Joined Jul 2004
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If your hinges are too tight for the elevons to go down here are a couple of things you can try, first disconnect the linkages and iron the hinge and bevel edge on the elevon with a hot iron. Turn the temp up slowly until you get the desired results. Sometimes this will loosen up the hinge on the elevon. If this doesn't work take a new razor blade and cut the elevon off and re-hinge it just like you did the first time with a little more gap.

Most of the time when someone has a plane that isn't flying well it is a combination of being tail heavy and poor leverage on the linkages from servos that are too small or the way the push rods are connected to the servo arm and the horn on the elevon. I usually use bigger batteries rather than adding too much weight so at least the weight is doing something for me.
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Old Oct 22, 2012, 06:48 AM
wheeeeee!
elCapitan's Avatar
United States, UT, Provo
Joined Oct 2011
916 Posts
Well, it's not too difficult to pull the lam and tape off the elevons and re-do it. The only problem is the servo horns. You have to cut around them, and when you re-tape and re-laminate, you have to cut slits and go around them again, but I've done it before.

5 big fishing weights will obviously make the plane "feel" heavier in flight, but it shouldn't make the wing "fly like crap." Usually the Reaper handles weight pretty well. Did you figure out where, exactly, the plane balances, now that you've got that weight on there? What size battery did you use? Is there room to move it forward?

I'm just thinking this might be a couple hours away from a fix.
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Old Oct 22, 2012, 09:39 AM
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United States, MD, Kensington
Joined Dec 2008
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Quote:
Originally Posted by jhorton View Post
I have built two Grim Reapers and both of them fly like crap, my hinges are to tight and I have to add huge fishing weights to the front of the plane because I never get the gear in the right place. I want to make a Grim Reaper for night flying where the hinges allow the wing to go up and down and not just one direction.
Can you be more specific than "fly like crap"? That would make it easier to diagnose the problem. Obviously it's not going to be fun to fly if the elevons don't go down, but, with due respect, who would try to fly such a plane?

As far as balance, I doubt your ESC placement makes much of a difference, and modern receivers are so light they can't make a difference. I built my Reaper with the servos up against the spars. I used slightly lighter wing fins (important because they are way behind the CG) and it balances perfectly with a 2,200 LiPo (and that was in the days when CTH recommended extreme tape on the elevons). I think I would have used a larger battery before I added weight, might as well have the weight be useful. By the way, how much to those fishing weights weigh?

I know Lee says this over and over, but some of us really need to experience it before we believe: Set your elevon throw to 3/8" up and 3/8" down.
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Old Oct 22, 2012, 11:02 AM
Planes in flames,,,
jetpackninja's Avatar
Gravity Sucks
Joined Aug 2010
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jhorton-

Check Lee's post about working the hinges with a hot iron.
I've hinged a couple of these too tight myself, one if them is currently my best flying plane.
This is what I did to fix it.
Remove the rods from the elevon horn.
Flip the elevon back onto the top of the wing to work the bottom of the hinge.
Then hold the elevon as far down as it will go- hopefully when you hold it down it will go at least as far and hopefully a little farther than the recommended throw. while it is forced downward, work the iron on the the top of the hingeline. Keep going until you can freely move the elevon through the recommended throws easily.


A couple of other things to check:
CG- Please tell us how far back from the nose the CG is. Check by balancing the plane as if it were flying supported underneath the wing at two points. The pushpin method works great for this.

Servo arms- check that they are installed on the servo a click or two forward when the servos are actually at center. This will help you to have (more down than up) differential and will help with roll rates and help give a smoother roll.

More specifics about your setup and some pics may be helpful too...
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Old Oct 23, 2012, 11:32 AM
Will work for batteries..
sd2602's Avatar
USA, UT, Kaysville
Joined Feb 2005
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So does anyone else follow these general rules about using an external BEC?
- 4 or more servos use a BEC
- Any number of standard servos use a BEC
- Same goes if you use digital servos
- 4 cells or more use a BEC

I am planning on using a 4 cell lipo and the servos I have are full size digitals. The reason is that I wanted to use what I had instead of buying new stuff. Thanks!
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Old Oct 23, 2012, 01:26 PM
wheeeeee!
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United States, UT, Provo
Joined Oct 2011
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I personally have never delved into external BECs, even with a 4-cell batt on a wing with two standard servos. I'd be interested in an answer from someone that uses external BECs, to see if/why I'd be better off.
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Old Oct 23, 2012, 02:40 PM
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United States, MD, Kensington
Joined Dec 2008
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Presumably the issue is if the combined load of the servos exceeds the rated amperage of the BEC built into the ESC. My friend just built a Hercules (6 servos), so I was thinking about this. The problem is that you can't get specs for how much current a servo draws, probably because it's dependent on the load. My guess is that it would be pretty hard to set up a test, since you'd have to test in the air, so maybe nobody has done this. Without testing, I'm not even sure what the symptoms would be of an overloaded BEC. Also, I would guess the size of the servos wouldn't be anywhere near as significant as the size of the load (air force against the control surfaces). In fact, smaller servos might be less efficient.

To answer the OP, no, I don't follow those "rules", mostly because a) this is the first I've heard them, and 2) I tend to just do what Lee says, since he's probably built and flown 100 times more CTH planes than I have!
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Old Oct 23, 2012, 03:05 PM
Lee
PERFECT LANDING !!!
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USA, UT, Orem
Joined Jul 2004
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We use two servos with most flying wings. Standard servos use more power but we are only using two not four like most planes. On the Herc pullers I have 5 and 6 servos. I have two ESCs (one on each motor) that each have a 4A BECs built in and although I own external BECs I didn't use them with the two BECs on the motor ESCs added together I had lotsa power to spare. I have not had a problem with this set up. There are always exceptions with number of battery cells and high draw servos and others but on this size plane I don't think there is too much of a problem.
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Old Oct 23, 2012, 11:55 PM
Will work for batteries..
sd2602's Avatar
USA, UT, Kaysville
Joined Feb 2005
462 Posts
Thanks for the insight. I think for my reaper I am still going to use an external BEC. To me its cheap insurance!

I have for sure been bitten by the bug though! I want the hercules pusher to mount a go pro!

I am making progress, slowly but surely! I got one elevon attached tonight!
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Old Oct 24, 2012, 12:05 AM
Planes in flames,,,
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Quote:
Originally Posted by sd2602 View Post
I am making progress, slowly but surely! I got one elevon attached tonight!
You're gonna want two
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Old Oct 25, 2012, 10:51 AM
Chess club geek with wings
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United States, FL, Cape Coral
Joined Aug 2008
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Flight report

Here is a shot of my recently completed Reaper. I've put 8 packs thru it so far and I've got to say I love the way it flys! Last night the winds were 15 to 20 mph and it handled the conditions with no problems.

This plane flys as fast, it's as fast as my 340 watt Assassin

The motor and ESC come down just warm to the touch so I think the set up is properly matched. Also - it balanced perfectly with the below electronics.

The set up is:
NTM 3536 1800kv motor
7x6 Hobbyking prop - 877 watts @ 63 amps
Turnigy 4s 2.45 mAh battery
Align 75a ESC
HS82MG servos
4 strings of LED lights

Thanks for the great plane Lee!
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Old Oct 25, 2012, 12:00 PM
Will work for batteries..
sd2602's Avatar
USA, UT, Kaysville
Joined Feb 2005
462 Posts
Quote:
Originally Posted by blunight View Post
Here is a shot of my recently completed Reaper. I've put 8 packs thru it so far and I've got to say I love the way it flys! Last night the winds were 15 to 20 mph and it handled the conditions with no problems.

This plane flys as fast, it's as fast as my 340 watt Assassin

The motor and ESC come down just warm to the touch so I think the set up is properly matched. Also - it balanced perfectly with the below electronics.

The set up is:
NTM 3536 1800kv motor
7x6 Hobbyking prop - 877 watts @ 63 amps
Turnigy 4s 2.45 mAh battery
Align 75a ESC
HS82MG servos
4 strings of LED lights

Thanks for the great plane Lee!
Nice work! Looks great! I made more progress on mine last night, now both elevons are attached and laminated!
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Old Oct 25, 2012, 12:01 PM
Will work for batteries..
sd2602's Avatar
USA, UT, Kaysville
Joined Feb 2005
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Quote:
Originally Posted by jetpackninja View Post
You're gonna want two
I was thinking with only one i could save on some weight!
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Old Oct 25, 2012, 03:29 PM
Crash....Fix......repeat.
kokopropelli's Avatar
United States, UT, Eagle Mountain
Joined Jan 2012
451 Posts
Quote:
Originally Posted by blunight View Post
Here is a shot of my recently completed Reaper. I've put 8 packs thru it so far and I've got to say I love the way it flys! Last night the winds were 15 to 20 mph and it handled the conditions with no problems.

This plane flys as fast, it's as fast as my 340 watt Assassin

The motor and ESC come down just warm to the touch so I think the set up is properly matched. Also - it balanced perfectly with the below electronics.

The set up is:
NTM 3536 1800kv motor
7x6 Hobbyking prop - 877 watts @ 63 amps
Turnigy 4s 2.45 mAh battery
Align 75a ESC
HS82MG servos
4 strings of LED lights

Thanks for the great plane Lee!
Nice Reaper! hey...whats that white stuff on the ground? its not time for that stuff yet!!
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Old Oct 25, 2012, 03:59 PM
Will work for batteries..
sd2602's Avatar
USA, UT, Kaysville
Joined Feb 2005
462 Posts
Quote:
Originally Posted by geminiryan View Post
Nice Reaper! hey...whats that white stuff on the ground? its not time for that stuff yet!!
Sure it is! Let it snow let it snow! It never hurt anything! Woke up this morning to a couple inchecs and its been snowing throughout the day!
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