I have a DP Ultimate with a YS 120 swinging a 16x8 APC prop. I am just starting to try and fly 3D and don't think this is the correct prop for vertical. I can pull into a hover (still doing it at a couple of f*** up's high), but just don't have any ummph left to pull out of it. I have to let it fall out of the hover. I have read that a flatter pitch prop is needed for vertical. What size and pitch prop should I use to be able to pull out of the hover??

I appreciate any advice that anybody can give me on this one. Thanks in advance

If the 16X8 is swinging happily without begin any load to the engine, I would give the APC 18X6 a try!

I don't know about the YS 120, but this prop really made a difference with my Webra 120 (I was using a 16X8 before I tested this prop out)

I had a Webra 1.20 with a Perry carb and pump and it had about 400 more RPMs than my YS 120s-both swinging a 16/8 prop-I have had 2 YS 120s--and they were different. --The first had no trouble swinging a APC 16/8--but the second just would not really perform well until I tried an APC 15/8. If it is 3D stuff you want, I think you may see better results with the 15/8.

Thanks for the advice. Will be heading to the LHS in the next day or so and will pick up both props and see which one works best. I appreciate the help.

RCKen,
I have the same engine and I think a 17/6 is about the best you can do. If you go to a 18/6, you may not get the RPM that you are looking for.

In my opinion, APC 17x6 is the best prop for 120 sized aerobatic plane: it has good profile, perfect for YS 120 or larger other brand 4-strokes. Heck, my OS 108 swung the APC 17x6 at 9400 rpm. So your YS 120 ought to do that well. That's over 20 lb of thrust, a 2:1 thrust-to-weight ratio for your plane.

Since you guys mentioned the Webra 120 do you mind sharing what you feel the best prop for my setup? I am currently swinging a 16x8 on an 8lb GP Extra 300S .60. What's the best prop for my setup you think?

How's that for a thrust-to-weight ratio!

I never used anything but a APC 16/8 on my Webra. Got about 8800 RPMs (at sea level) if I remember correctly--again, it had a pump and Perry carb. HOWERER REMEMBER-- RPMS are relative to season and where you live so you can't always get an accurate comparison and this is true wheather it is a 2 or 4 stroke.

Let me ask you this question AJF--2. I am having problems with mine dying once I raise the nose. Someone mentioned I should get a Perry pump like you said. Why did you get the pump? Same problem?

The pump was on mine when I bought it. The larger Webra (and the Bully line of engines) have a reputation of being difficult-or not being "user friendly" might be a better way of saying it. Versane Products bought Perry at one time, but it seems that I remember sombody saying even that has changed lately. If I had it to do now, I think I would go with a Cline (or is it Kline) pressurised system. Remember these engines suck a lot of fuel at full throttle--one thing I would check is to make sure you have large fuel lines to the carb and even in the fuel tank to quench that big thirst. When running properly-that is a stump puller of an engine! I had it on an Ohio 72" Extra and it literally ripped the alirons right out of the wings.--then- I put it in a Goldberg Jungman and it caused a flutter problem that never existed with the YS 120 or a SuperTigre 90. It was at that point in my aviation career that I learned throttle management! Again-that is a strong engine!

AJF--2,
One of the things I learned with flutter is that it doesn't take long for it to destroy a plane. I usually go with less pitch and never give it a second thought! I know this is not the correct approach and that servo strength and control stiffness plays just as important or more part but it is easier to go with a lower pitch!

I have learned a lot about flutter--actually-more than I want to know. I know what you mean about less pitch. There is just something about a big engine screamin out 10K RPM that makes me cringe. These days I just try to be a little more subdued when using the left stick--use it as I need it kinda. Don't really remember the last time I did a full throttle dive or level flight for that matter.

I've never did a full throttle dive nor to I plan to do it! This is begging to lose your airplane from flutter...

Flutter is caused by overspeeding in most cases. Therefor throttle control will reduce most cases of flutter.

I am still amazed when I see instructors teaching people to fly with only the ailerons and elevator, only showing them the throttle on takeoff and landing and NEVER showing them how to use the rudder... They might as well be flying a 2 channel park flyer.

-- -Comom' now- -you never owned a Scat Cat(4), or Dart(2),or Cylpso, or Starfire(2),or Kaos, or Kougar, or Four Star, CG Extra (2) or Mid Star, Hobbico Extra(2)--maybe I better stop here--point is - there are "some planes" that beg to bore holes in the sky. Never lost any of these to flutter. And at one point that is what I lived for! However-times and people change. They are just not my thing anymore. Not that there is anything wrong with it--just enjoy a different style nowdays.