Mini Apprentice s centre of gravity

[mrmat01]

G'day all
I have been hanging around the sight for the last week & thought I should join.
I'm just getting back into the hobby after a short stint about 15 years ago. I have recently brought my self a Mini Apprentice & was wondering if the stated C.G in the manual of 75.0mm (approximately 2.95 inches) back from the front edge of the wing is correct?
Quote from manual
Centre of Gravity (CG) Verification
An aircraft with a correct CG has its weight balanced at a calculated point
where the entire airframe will balance when suspended at that point.
After installing the battery (in the recommended position) and before
powering on the ESC switch, verify the CG by supporting the aircraft 75.0mm
(approximately 2.95 inches) back from the front edge of the wing, as shown.

The reason I ask is I was at my model club today hoping I could get it up for its maiden flight. When I was getting it ready one of the more experienced pilots offered to help me with its Maiden.
We went through the pre-flight checks & then he checked the C.G & told me not to fly it was way to tail heavy:Whew:. He checked the C.G at the normal position 25% back from the leading edge of the wing.
& that on the apprentice is almost 22mm back from the leading edge of the wing. With the wing being 86mm 25% of that is 21.5mm:Thinking:. Not the 75mm stated in the manual. I spent all afternoon getting the C.G correct With a Great Planes C.G Machine as per the manual with the two types of battery's I'm going to use.
Only to be told it was way out:Confused:. I showed him the manual & he said it must of been a misprint. This gentleman is a very experienced pilot & model builder & I very much appreciated his help.
I'm feeling a little confused & lost as to what to do.:Confused::Scared::(
Can some one with experience with this model tell me if the manual is correct for the C.G please
Thanks in advance

[Hippie 64]

Mrmat01 first off Welcome to the Squawk !

Where did you locate the ESC because it sounds like something was placed too far back to cause the CG to be off . Hobby Zone has had that plane out for sometime so all the info should be correct . Not to say there may not have been changes but I would first look at where things are placed, the ESC and Rx . If you need to move the battery forward its ok to do so and get the right CG . A tail heavy plane is a crash about to happen more often than not . But you can fly and land a nose heavy plane even though you will be adding in elevator it will fly fine .

Start with the locations of other things and see if adding a little forward placement on the battery works . If its not much I wouldn't be concerned with it .

Keep us informed .....


Bryan

[xviper]

Are we talking about this Mini Apprentice S ................................... https://www.horizonhobby.com/product...-s-rtf-hbz3100 ????
You say your plane's wing is 86mm from front edge to back edge at the root. That means your whole wing is only about 3.4" total. That's a really skinny wing if you compare it to the regular Apprentice, which is only about 8" larger wingspan. Are you sure you are measuring it correctly? Please measure the wing distance from front to back edge at the wing root (immediately next to the fuselage) to be sure. I can't imagine your Mini Apprentice has a 3.4" wing when the regular Apprentice has about a 10" to 12" wing depth (likely much more).

[fhhuber]

https://www.horizonhobby.com/pdf/HBZ3100_Manual_EN.pdf

Page 11. The graphic shows appx 1/4 of the way back from leading edge.

Typical for that shape wing is 25% to 30% occasionally as far back as 35% when pushing the plane's aerobatic capabilities rather than using it as a trainer.

[xviper]

If he got the BNF, the ESC and RX are usually located in a fixed place when it comes out of the box, so the owner doesn't do anything in terms of "placing" it. What needs to be clarified is this statement ...............

With the wing being 86mm

This cannot possibly be correct. If 75mm is the recommended CG point, then the wing depth at the root is more like ~12". I'd like to know where he's measuring to get a wing depth of ~3.5".

[mrmat01]

Thanks for all your reply’s
I stuffed up what I should of wrote was 186mm & 25% of that is 46.5. This is what happens when you type after midnight AU time.
The plane is the RTF. The manual states on page 11 the C.G is at 75mm that is where I balanced the plane using a Great Planes C.G machine. The gentleman at my club checked the CG at the 25% point (with fingers) which is near where the servo wires go along the wing which is about 20mm forward of where the manual says at 75mm. This is why I’m confused I followed the manual & he said that this couldn’t possibly be correct. I balanced the plane as per manual if I balance the plane at the 25% point I would have to add alot of weight to the nose & this doesn’t seem right to me as it is a RTF trainer not a kit.

[xviper]

I've looked at a couple of YouTube vids of this plane and 186mm is more like it. This is a much smaller plane than the wingspan would indicate.That 1220mm wingspan seems off as well. Next to the guy in the video, it would make him 7+ feet tall. That being the case, then I would agree that 75mm is not correct either. It's odd that Eflite would be this off with their measurements. I would go with 25% of what the real measurement is and start with that.

[mburton47]

mrmat01: I don't have the mini apprentice but found this video which may help you if you haven't already seen it. Good luck...(https://www.youtube.com/watch?v=mAP-G5FsMFI)

[mrmat01]

Thanks guys I’ve whatched that guys whole series on the Mini Apprentice & numerous other vids & know one says anything about the factory C.G being wrong. I can’t really see that Hobbyzone & Horizon Hobby would get it so wrong. I’m waiting to hear back from Horizon Hobby. I would be really keen to hear from someone with experience with this plane
thanks guys all your help and comments are very much appreciated

[mrmat01]

Hi all
I have heard back from Horizon Hobby & this is what they had to say.

Admittedly that does seem a bit off by conventional standards. However this plane is anything but conventional as it is governed by an onboard gyro that will keep the plane under control even if its a little off on CG. Now we must clarify what we are saying... the CG mentioned in the manual is correct and we have literally thousands of these planes flying to date and no reported issues. We recommend using the recommended battery size and then go fly it. Maybe even video your first flight for verification. If there is a problem this email serves as your first contact about the issue and we will use it for reference if there is a problem.

It seem that the 75mm CG has something to do with the gyros they are willing to stand behind what is written in the manual so I’m just going to go with the factory CG & suck it & see. Thanks to all of you that replied & offers advice.
Cheers
Mat