ahicks

My Feedback: (2)

The 20" will act as an air brake as well. They don't "coast" like an 18". Seen most easily on speeds on short final and any kind of down line when flying.

gagallagher04401

My Feedback: (20)

Not sure if I understand this staement?

What size spinner typically for a plane of this size?

Thanks
George

kmeyers

Well the pitch @ rpm = an air driven speed. If that speed is faster than the plane is currently traveling the plane accelerates. If slower it acts as a brake. When acting as a brake the effect is greater as the diameter increases.

What ever size spinner looks the best.

gagallagher04401

My Feedback: (20)

Thanks!

Another question, I have been balancing the prop (Wooden Top flite 18x8) How "perfect" does it need to be? I would call mine "close" not perfect. When It had nothing added toit it, it was WAY off, now it is "close" Is that good enough? Just having trouble getting it "perfect" I would think perfect would not matter because as it gets chipped, dinged up etc... it will no longer be "perfect anyway.

Thanks
George

ec121

My Feedback: (2)

I h ad a Quadra 40 with an 18x6 on a 72in. Stik Biplane. It wasn't enough prop. It would fly the plane, but an 18x10 worked better. I had ground clearance problems with the tail dragger, so a larger prop wouldn't work. I ended up with a 3-bladed prop. Measure from the prop shaft to the ground with the fuse level then figure the prop diameter you can use with adequate ground clearance.

ahicks

My Feedback: (2)

You could look at it this way too. All else being equal, that 20" prop is punching a bigger hole in the air - creating way more drag at idle/reduced power. It's fair to think of it as a solid disc actually. Also, going from an 18" prop to a 20" prop will generally call for a reduction in pitch (to keep comparison fair). The flatter blade/reduction in pitch will also act as a brake. The only downside to the move would be a reduction in speed - and generally anyone flying a sport, 3D, or aerobatic plane generally doesn't care about top end too much. Guys with big control surfaces need to avoid it actually. 6" of pitch is generally plenty!

gagallagher04401

My Feedback: (20)

Yeah people have mentioned giong with a bigger prop 20x6, 18x10. Plane has a 18x8 on it. I have no idea how to choose a prop for it. Engine is a CCRC 40cc engine.

IT will fly with my 18x8 right?

Thanks
George

frieshoo

My Feedback: (20)

18x8 should be fine. My buddy has a ccrc 40 and he has a 20x8 PT carbon fiber prop turning about 7500rpms. Your 18x8 should turn about 7000rpm or so, new. It will get stronger as it gets more run time.

gagallagher04401

My Feedback: (20)

Thanks!

Another question, I have been balancing the prop (Wooden Top flite 18x8) How "perfect" does it need to be? I would call mine "close" not perfect. When It had nothing added toit it, it was WAY off, now it is "close" Is that good enough? Just having trouble getting it "perfect" I would think perfect would not matter because as it gets chipped, dinged up etc... it will no longer be "perfect anyway.

Thanks
George

frieshoo

My Feedback: (20)

Get the 'tip' balance as close as possible. 'tip' balance has the the blade tips at the 3 o'clock and 9 o'clock position. If this is close, you will be fine.

Do you have a good balancer?

gagallagher04401

My Feedback: (20)

Thanks alot, so I am good then, I was worried I had to get it dead perfect.

The balancer I have is not the best but it works, they call it a finger tip balancer, but I use two tall glasses to balance it on, works pretty good.

Thanks again!

George

BarracudaHockey

My Feedback: (11)

If you're that worried, get a Vess balance ring.