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Old Yesterday, 11:03 PM
Registered User
Australia, QLD, Ipswich
Joined Sep 2008
1,239 Posts
Ok, what do you guys recommend as a good starting point? Manual states 3.75" - 4.75", currently i'm about 4.25", do you suggest going to 3.75" or further forward like 3.5"?

I can tell it's going to be a ball to fly once I get it sorted, I was just getting frustrated with it's weird trim behaviour, and my thougths had gone to thrust since the fuse got a little messed up and I wondered if I'd introduced a downward bend in the fuse.

On the positive, the 8s 2400mah on a Motrolfly 4315-367 using a Hobbywing Platinum Pro 70a HV ESC is a potent setup with a 15x8. Motor was coming down dead cool, I can only imagine how silly it will be on a 16" prop, it absolutley rockets out of hover currently.

No Bec on the ESC so i'm using a 700mah rx pack. I'm not sure how the weight compares to a 6s setup as I haven't weighed it but it's floaty as so i'm guessing it probably compares pretty close even with the extra glue from repairs.
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Old Today, 07:02 AM
They Call him Dead!
YellowJacketsRC's Avatar
United States, SC, Pawleys Island
Joined Jul 2003
6,600 Posts
I don't know about the fuse...but all things being equal your are tail heavy.

Just move the lipo forward a little at a time until the diving stops. It sounds like your pretty far back so try 1/4" at a time. It's just gonna take trial and error to get it right.

When it is right, you should be able to fly a 45* vertical line, roll inverted, and the plane should hold that line for 100' or so before it starts to fall off slightly toward the ground. When inverted level, you should have to put a SLIGHT amount of pressure on the elevator to keep it level.
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Old Today, 08:39 AM
This is NOT a TOY?
C_Watkins's Avatar
United States, GA, Atlanta
Joined Jul 2011
2,490 Posts
Quote:
Originally Posted by luke352 View Post
Ok, what do you guys recommend as a good starting point? Manual states 3.75" - 4.75", currently i'm about 4.25", do you suggest going to 3.75" or further forward like 3.5"?

I can tell it's going to be a ball to fly once I get it sorted, I was just getting frustrated with it's weird trim behaviour, and my thougths had gone to thrust since the fuse got a little messed up and I wondered if I'd introduced a downward bend in the fuse.
First, make sure you don't have any unintended mix active. ie... remove the prop, and work the throttle while watching the elevator.
I doubt it's that, but it's just something I always check when dealing with a perplexing issue

Since this is a post-crash-repair behavior though, it certainly is possible that it isn't perfectly straight and has too much down thrust now.

Try the CG at 3.75" and if it still exhibits the behavior you described, maybe try a couple washers under the bottom two motor bolts and see if it improves.

Of course, depending on the radio you fly, you could always just mix it out... but it's better to get it right if you can.
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Old Today, 08:58 AM
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Doc Austin's Avatar
USA, FL, Largo
Joined Dec 2005
16,421 Posts
Quote:
Originally Posted by luke352 View Post
See my comments in red.
That's some very bizarre behavior. Do you have a Robart incidence meter, or access to one?
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Old Today, 09:44 AM
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Sideslip's Avatar
United States, MI, Parchment
Joined May 2004
1,099 Posts
Quote:
Originally Posted by luke352 View Post
Here you go this is the amount of trim I have to fly level around 1/2 to 3/4 throttle. If I go to full throttle it stills tries to dive even with all that trim in, and obviously when I slow down it just tries to climb, likely because of all the up trim I have in.
Mine does essentially the same thing, only mine has never been crashed. I asked around and was told that it was a CG problem and not a thrust line issue.

I have sense been moving my battery forward a little bit at a time and it does help. I can't give you an exact CG position because I have not checked it lately. I'm sure it's 4.00" or less. When I first started flying mine with the battery all the way against the wing tube, it would actually climb hands off inverted. That's a pretty much dead give away that it's CG related and tail heavy.

Good luck,
Bert
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Old Today, 01:29 PM
No Static
United States, AZ, Gilbert
Joined Mar 2012
170 Posts
I am going with the torque motor and airboss esc with the 7245 servos. I like to keep it simple and noticed the airboss puts out 6v to the servos and the 7245 like to run at 7.4v. My normal solution would be to add a castle bec and program that at the 7.4v. Is there a better way? Are the 7245s happy at 6v and a non issue?
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Old Today, 01:49 PM
3D? I only got two thumbs!
United States, MA
Joined Jul 2012
1,018 Posts
Check out the specs:
http://hitecrcd.com/files/2013_HRU_ServoMat_2.pdf

At 6 volts the 7245s are slower and have less torque than the 5245s do on 6 volts. At 7.4 (or 8) volts they have more speed and torque than the 5245s do on 6. You really want hi voltage for hi voltage servos.
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Old Today, 02:07 PM
No Static
United States, AZ, Gilbert
Joined Mar 2012
170 Posts
Quote:
Originally Posted by AeroKen View Post
Check out the specs:
http://hitecrcd.com/files/2013_HRU_ServoMat_2.pdf

At 6 volts the 7245s are slower and have less torque than the 5245s do on 6 volts. At 7.4 (or 8) volts they have more speed and torque than the 5245s do on 6. You really want hi voltage for hi voltage servos.
That's what I was looking at. ..so run a separate flight pack or castle bec bumped to 7.4.v? This will be my first airboss esc. I would usually just use a castle esc and program that for the voltage needed. As far as I have read I don't see the airboss being programable.
Castle bec makes the most sense to me...just wondering if I should be thinking separate flight pack.
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Old Today, 02:11 PM
No Static
United States, AZ, Gilbert
Joined Mar 2012
170 Posts
Got my shipping notice.
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Old Today, 02:24 PM
3D? I only got two thumbs!
United States, MA
Joined Jul 2012
1,018 Posts
I'm putting together one of these with 7245s, I went with the castle bec pro. I like lots of margin for error I don't like the idea of having deal with yet another set of lipos. I also like the idea of a constant 8 volts throughout the flight.
But, as far as HV servos or 60" planes go, this is my first time for both so take my advice with a grain of salt.
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Old Today, 02:25 PM
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Doc Austin's Avatar
USA, FL, Largo
Joined Dec 2005
16,421 Posts
The 5245MGs still work wonderfully.

Honestly, I don't care what servos people use.. Really, why would I care? It's your plane, it's your money, and no one compensates me for force feeding people servos. I've turned down enough sponsorship from servo companies to sink a battleship, so I have no reason to care what people use as long as they like it.

What I hate is people saying the 5245MGs don't work and you need to spend $300 for servos. People on a budget see the competitor's Edge can use 225MG, so Extreme Flight loses the airframe and power system combo sale based off of false information. That, and I don't believe the customer gets as good of an airframe.

Certainly the 7245MH is a better, faster, more torguey, better centering servo, but it also costs a lot of money and they need 7.2-8 volts to work properly. The complexity of an external BEC greatly offends me because complicated fails faster than simple fails.

Really, run what you want and be happy. Just don't tell customers the recommended set up doesn't work because I will show you that it does.

Really, let's be fair here, OK? Do you see any stalling? Do you see any blowback? Do you see the plane jumping in and out of trim? Uhhh.............no, you don't. These servos work just fine for me. Granted, I promise to try the 7245MH, but for now the 5245MGs are just fine.


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Last edited by Doc Austin; Today at 02:31 PM.
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Old Today, 03:28 PM
Altitude is my friend...
Depronicus's Avatar
Southern California
Joined May 2009
1,378 Posts
Quote:
Originally Posted by Doc Austin View Post
...Do you see any stalling? Do you see any blowback? Do you see the plane jumping in and out of trim? Uhhh.............no, you don't....
Heck, I don't even see that with the 225MGs I've used all along on five-foot-wingspan planes, including my Laser 60, Edge 60, and dear departed Slick 59.

I bit the bullet and coughed up over three hundred big ones for 7245s on the MXS 64 I'm in the process of finishing up, just to see what digital high-voltage servos are really like. I sure hope they're worth it. I hope they live up to the hype. We'll see...
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