Hi,

the flying season restarts tomorrow after the off-season (monsoon). Since our field is likely to be unprepared, I am taking out a old hack: a Phoenix Tiger 40 with its old 55ax. I did the following things today

1) checked lateral balance and CG: The airplane had a bird hit a long time back (two years back). I never balanced it after the repair but it never flew the same again and I quickly moved on to other airplanes. During this off-season, I had checked the lateral balance and found that the undamaged wing required nearly 35g (1.25oz) for balance. I added the same in lead weights to the wing tip under the covering. I checked again today and it is in balance

By the way, the tailplane and rudder are no longer in alignment with the wing after that bird-hit. I have flown the airplane quite a bit after that however with no problems, only a little correction required at the top in a loop.

2) Checked CG: Same time I had checked lateral balance, I had found that the CG is not proper (80mm from LE). It took 125g (4.4oz) to the nose and an aliminium spinner to get the balance with the tank empty. I rechecked it today. (Cant move the battery around, there isint any space in the fuse)

3) Battery: My old 2500mAh NiMh takes something like 330mAh in the charge and discharge cycle on the Triton2! So I put in the 3200mAh LiFe that I got in the off-season (and again checked the CG with that)

4) Prop: I have never balanced a prop before. During the off-season I got a prop balancer and I found the 12x8 MAS prop I had installed was out of balance (with the ceiling fans switched off of-course), So I took off a few flakes of material off the tip of the heavy side and tried again till it sat just balanced. Once almost balanced, I rounded the tip with a sand paper to match the shape of the other side and checked the balance again

Now when I ran the engine, there was a lot of vibration at absolute idle. When I add a few clicks of throttle, the engine stops shaking but the spinner tip continues to vibrate a bit. Engine is still untuned (having washed it during the off season) and running at 3 turns of HS needle.

The model will be out of trim. That I will get my instructor once again to check at the field

Haning done all the above, two things I wanted to ask:

1) Did I miss anything?

2) Should I worry about the prop-spinner balance?

Ameyam

1) I believe you did all you should. I would verify all linkages as well.

2) You could balance the prop; however, I suspect a bent engine's shaft due to the bird collision, since the spinner doesn't turn round.

If you do a search you will find the question on prop balancing in a number of threads, the question come up about every month. What you will find is some people like myself balance every prop they use and others never bother. Some only balance props after a certain size. I never bother to balance a spinner and others wouldn't dream of ever installing a spinner unless it is balanced. Spinners are in the center of mass and don't effect anything very much but the prop will. You will have to decide for yourself if it's worth the couple of minutes it takes to balance a prop. I don't smoke in my house but I do in my shop so when I have some new props I go out and have a smoke and balance them, maybe it's just something for me to do while I'm killing myself???

No Lnewqban, thats not the case. I didnt hit the bird with the nose, I entered a bird bank and realised that I could hit one so I banked out immediately. As I was flying out I glanced a bird's right wind with my left wing. The bird (a Hawk) dived but was OK. The turtle deck on my airplane on my wing was broken

I did the fuse in a different accident subsequently. I took off in a cross wind and rolled immediately. Went to full right aileron and rudder but couldnt correct and the airplane cartwheeled at very low speed. Broke the plastic spinner, the fuse behind the wing and the tail just infront of the stabiliser. The tail took the biggest impcat of the cartwheel since the nose landed mainly on the front gear. Since then, I have flown this same engine on a GP reactor 46 with the stock spinner without any issues.

Was wondering whether I should put back a plastic spinner. I have a couple of GP spinners with aluminium backplates that I have reserved for my more prized models and I always found them to be absolutely balanced when operating

Ameyam

Ok, I took out the aluminum spinner and put in an old cheap Dubro 2" spinner. Its in no better balance as compared to the metal one but there are likely to be a number of landings in the tall grass tomorrow (that is the recommended landing method for trainees and those who cant perfectly line up the runway yet, we are flying of a horse racing track and it is only that wide) and I dont want any hard hits transfering on the crank again.

The dubro spinner is a bit lighter than the metal one. Hence with the thing absolutely level with the metal, it becomes slightly tail heavy with the plastic one. However, that is without fuel. Once I put in the full tank, it will become nose heavy again. That means that the airplane will be almost CG neutral all the time. Any suggestions?

Ameyam

That means after about 10 minutes it will be tail heavy. Add a little lead to the nose to CG it without fuel. Sometimes the spinner back plate will get a warp/bend from tightening the prop on or from getting hit on the nose. I have put these on a piece of wood and using a big socket I can give them a hard whack with a hammer and get them straight again. Sometimes it works, sometimes it doesn't.

GrayBeard,

Actually, its only marginally tail heavy without fuel i.e. when held upside down at the CG, the tail sits slightly lower than the nose but it doesnt actively drop. I used the rubberised rounded end of a chicken and booster with rubber cap fitted to hold it up. I have already added so much weight to the nose (see the first post), I am concerned regarding wing loading. This airplane isin't like the CG Tiger 40-that one has a cord of 12.4" and a span of 61". This has a cord of 10.5" and a span of 59" so its started off with higher loading and now we have repairs, heavier LiFe battery and more counter weight in it already. What do you think?

Ameyam

If the tail is dropping you are not at the center of gravity. Get the fixed horizontal tail surfaces horizontal.I guarantee your C.G. is aft of where you are placing the balance pivots if the tail drops at all - that is how you tell it's pivoting at the C.G.! It will NOTpivot!</p>

Ok, in the morning, I will add a dead AA cell to the area just below the tank to get the CG.

By the way, was my prop balancing technique correct?

Ameyam