Trung

Hello everyone, well finally I've finished my first kit. The plane came out quite tail heavy... probably because I replaced the tail wheel and added extra rudder. The plane balances about 1" behind the plan's CG. I found out how much weight was needed to correct the CG, it came out to about 9-10 oz of weight mounted on the nose! WOW there isnt even enough room to fit that much weight. My tank compartment is sealed so can't put anything in there [:@] ... there so much room under that tank. Well anyways, how far back from the plan's cg can my cg be without affecting flight characteristics too much. Yeah and the plane already weighs 5.5 lbs, would be nice if it wouldnt weight any heavier. Any suggestion is appreciated guys. Thanks
Trung

voyager_663rd

Before adding dead weight: Try moving the engine out further on the mounts for starters. Can the battery be moved forward more than you have ?

Trung

well I could move the engine but then I might need a new engine mount cuz everythin is pretty much built and it will only make a 1/2" difference. The battery and reciever are suposed to be an inch or so behind the CG according to the plan but I have pushed them all the way forward about 2 inches infront of the CG and still I needed quite a bit of weights.

submikester

My Feedback: (6)

What engine are you using that is so light?

rspiegel

My Feedback: (6)

Were is the cg at most people fly it behind the recomended. Mine was way back there. add weight and start removing it some..

Gray Beard

My Feedback: (-1)

About 1/4 inch is about the max on that little plane. Remove the engine and just wire it forward and see how much that helps. Maybe add A heavy spinner. I had the World Models little extra and 1/8th either way was A big difference on the way it flew. I used A strip of lead and mounted it on the motor mount with screws, it worked out OK.

Trung

I put an OS AX 46 on it, and the engine position is already about 1/2" farther forward than the plan. Im going to move it as far forward as possible and see what happens. but then it doesnt look too good with the engine stickin out that far [&o].

ukrconsul

My Feedback: (1)

I just maddened SE this weekend with CG around 1 inch back from where it has to be according to plans, so what? I didn’t notice any of bad tendencies.
Look, when you take off you have 10-12oz of fuel in your tank, when you land – plane weights the same less. Your CG moves back a lot during the flight.
If you want to experiment do not rebuild your plane. Just attach some extra weight under the nose (tank) from the outside by Velcro, for an example. Mine weights 6 lb and flies extremely well with Saito 82 (500g with muffler) and 1100 mah battery, it is a kit and almost no epoxy was used.
So, hang some weight from the outside temporary and try to fly it. It will fly with 1 lb additional weight no problem.

Trung

I thought 1" back was too much, but if you flew fine so I wont worry so much. Now that my engine is moved forward a little, this helped balanced tha plane out alot better. I only need about 100 grams of weights. I also pulled the tank out and shoved the battery into the lil compartment under the tank. With no additional weights the plane balances 1/2" back from the plan's cg. Ill try it with the weight to get a feel of the plane then ill remove them and see whathappens.

litebipe

ukrconsul: How did you end up with the CG 1" back using that engine? I'm building a SE with a Saito .72 and I figured these relatively large engines would generally make the plane nose heavy. Plus, with the carb in the rear of the engine, they kind of hang off the edge of the engine mounts, moving the CG even further up.

I moved the firewall back 1" last night during construction to move the cylinder and spinner back plate in line with what they show on the plans. Hopefully I didn't get myself into trouble.

ukrconsul

My Feedback: (1)

I don’t know, surprised by myself. 82 weights the same as 72 (500g with mufflers). I have enlarged rudder a little bit, used 10 or 12 oz du-bro tank (don’t remember now, it is fixed permanently inside) four 56g digital servos and one jr 517, 1100 mah near tank (over gear plate). I don’t have pants and have two 2.5” du-bro light wheels. Stock landing gear, I didn’t move firewall (I don’t care about so called "esthetics" that bothers others, I think plane looks OK) and my engine ends 0,4” in front of firewall. And I don’t think 82 is too much for the plane.
Probably, it is not 1 inch now as I added big aluminum spinner (2,5”) in front.
O yea, I have a toy pilot - small sea lion figure from my two months baby son bath toys kit.

daven

My Feedback: (1)

I flew mine considerably tail heavy, but don't remember the exact number although I am sure it was well over 1/2" beyond the recommended C.G.

I'd add the weight to the nose some how, and remove it after you get it trimmed and the throws set properly. I think you will find that the tail heaviness is a good thing, as it flies much better tail heavy once you have it trimmed out.

litebipe

ukrconsul: what did you cover it with? was there room to move the battery forward below the tank if necessary?

Can you move the sea lion forward?

Oh, what prop are you using? Any problems with ground clearance using the stock LG?

kregan

My plane balanced perfectly on the 3-1/2" CG with a Ervine .53 2 stroke,
great plains aluminum spinner, apc 12x4 prop, 10 oz. dubro tank, pull pull
rudder and elevator, replaced the flying rods with wire, and a sullivan tail
wheel. Battery was right over the gear.

Now after flying I have been moving the CG back.... the battery is now
behind the radio/servo tray... had to make an access panel in the bottom
of the fuse. It now balances at 4-1/4".

Will this thing ever flat spin???

It will knife edge all day long with the stock rudder, but it pulls toward the
landing gear, needs a little up elevator, I will mix that out with the 9C as
soon as I figure out how!

Trung

I still dunno why my plane is so tail heavy... maybe too much glue. Now that I looked at my CA bottle, theres about 3oz of glue in the tail area. Now that I moved the engine about an inch forward and added like 3oz of weight to the nose...it balances at about 4" from the LE.

ukrconsul

My Feedback: (1)

Litebipe
I have no problem with my plane so I do not have to move battery somewhere else.
It is covered in oracover. I have mounted landing gear with three rubber dampers (for engine mounting) and I have 13x6 MA prop. 2.5" wheels by now but mowing to 3" (high grass).