Jschulwdw

My Feedback: (3)

I seem to be struggling with balancing my US60 with an OS 61FX 2 stroke. The book says the CG is 4 1/8" behind the leading edge. This seemed far back to me since the wing spar is almost 1" forward of the CG. When I balance the plane on the Wing Spar i need to ad 3/4 oz to the tail. When I move the CG to 4 1/8" I need to add about 5 1/2 ounces to the tail.

My questions are:
1. Where is the CG on this model. Friends at the shop have all given their opinions but want I would like to know is where is the best CG location for a relative beginner. I can fly my Avistar with no problem but I am not an expert.

2. If I do go with where H9 says at 4 1/8" is it too much to add 5 1/2 ounces to the tail. Needless to say I am not using the most powerful engine for the plane.

Everyone’s help is greatly appreciated. I look forward to hearing the verdict.


Thanks,
Jeff

MikeL

My Feedback: (3)

No idea on the CG, but replacing the stock metal motor mount with a lighter one will shave weight and move the CG back.

vinnie

My Feedback: (1)

Jeff,
of the two choices opt for the forward CG with less weight. At the very least your chances of a second fight will increase significantly.

As you gain experience you can try different CG/weight combos to get the flight characteristics you want

Good Luck.

splitess

My Feedback: (2)

I've got an Ultra Stick 60 with a YS 91 on it. I had to cut a hole in bottom of the fuselage towards the rear of the plane and put a large battery pack in that location.

I recommend going by the book, it worked for me.

Secondly, you will really enjoy that plane. It is great to fly.

TerrellFlyer

The people I fly with are balancing by the book. I'm assuming the fuel tank is empty,might move the battery aft.

FlooredCOBRA

Before you start adding weight to compensate try different battery and receiver locations. Try to move them forward or rear depending on where it is needed. In the last scenario add the weight.

And like TerrellFlyer mentioned make sure you are balancing with an empty tank.

MikeL

My Feedback: (3)

With my US40, I've got the battery pack as far in the tail as it'll physically fit. I had to cut a hatch about 2 inches ahead of the fin to get it there. It's still not "snappy" enough for me.

ptgarcia

My Feedback: (36)

Balance according to the manual. Instead of adding weight try moving the battery/receiver as far aft as possible. On my US 60 I mounted the rudder and elevator servos in the tail and mounted a 1400mAh battery a few inches aft of the servo tray to acheive balance without adding any weight, and thats with an O.S. 91 Surpass, which I would suspect is a few ounces heavier than your 61FX 2-stroke. Good luck! By the way, you're going to love this plane! Later.

Goinstraightup

My Feedback: (26)

Just a quick thing to check: How far out is your engine sitting on your engine mount? Sounds like you need set it back as close to the firewall as possible. Try that and then see how your balance is.

FlooredCOBRA

You took the words right out of my mouth... fingers....or whatever.

P-51B

My Feedback: (5)

I added weight to the tail to get to the published balance point. I quickly learned that the published balance point is WRONG. Others in my area have agreed with theirs.

Play it on the safe side to start.

Also, reinforcing the landing gear area is highly recommended. Mine had very soft wood.

Jschulwdw

My Feedback: (3)

Thanks you everyone or all of your help.

Here is what I have done.

For the engine, I mounted it as close to the firewall as possible. I did this from the beginning since I knew it was going to be nose heavy.

I have mounted the receiver directly behind the servo and the battery behind that.

To get the plane to balance I added 3 ounces of weight to the tail. This is temporary as I plan to move the rudder and elev servos to the back.

The weather was good in Chicago this weekend so I took it out yesterday and today. I had my friend maiden it and it flew nicely. Then I took it up and had a bad servo glitch and almost planted it but I was able to recover. I handed the box to my friend and he brought it down but also had it glitch on him. The problem is in the receiver as I swapped it out last night and flew all day today. This plane is great. I had only flown the trainer for 2 days and was trying to do maneuvers that it wasn't designed for.

This goes to show you that anything can happen even after time is spent doing the basis like range checking. The receive is going back to Futaba as this wasn’t the first strange thing that it has done.

Thanks again for the help.

Jeff

strato911

For future reference, the normal CG for a straight winged, constant chord wing is approx 25% - 35% of the chord width from the leading edge.

http://www.uoguelph.ca/~antoon/hobby/pmdesign.htm

Tom02

My Feedback: (3)

I have the the US 60 w/ OS 91 fx, i'm told it weighs the same as the 61. I have an 1100 mah nimh in the tail as far back as I could plus about 3 ounces of lead. Originally plane had no lead, flew fine and great with the CG where the book said it should be. People at the club said that the plane is capable of hovering and basic 3D manuvers and to achieve this add lead to the tail until you just need the littlest amount of imput to fly the plane level while inverted. Plane does hover now, but needs a pump to do it b/c it will start to sag about 5 seconds into the hover. This is primarly b/c I build the tank on the CG. All servo placement is where Horizon reccomends. I have seen people at the field with this place with the reccomended saito 100 and they had both tail servos and the battery in the back of the plane. Don't forget though that it's always better to be noise heavy then tail heavy.