forestroke

I have a WM Ultimate 30 and it's quite a pretty plane. However, I think it is extremely tail heavy. Although I have balanced it as per the instructions (81mm from leading edge of top wing), it still flys what appears to be tail heavy.

First it is impossible to control when at full throttle, bird just doesn't feel like it's flying at all it just is up there doing funny stuff. I have absolutely no "feel" for the plane movements.

Second, even at one quarter throttle, the biplane maintains a full knife-edge indefinitely, it just won't come down.

Is this normal?

I have an O.S. 32sx with about 7 ounces of weight in the nose and turning a 9*7 APC prop. Battery already in front of firewall!

PLEASE HELP!!!

forestroke

I'm trying to fly tomorrow, so would appreciate it if someone could let me know!!!

daveopam

My Feedback: (9)

It does sound tail heavy. A good bipe will do great knife edge so I would not judge from that. Does it get worse as it burns fuel? This would also point to tail heavy. Bipes are also hard to balance. At least mine was. One of the wings is always in the way. Try a little lead in the nose. I hate to put lead in anything but at least you will know.

David

MinnFlyer

My Feedback: (4)

Remember, a few things:

All planes are different. Even two of the same kit.

The "CG" range is a starting recommendation by the MFGer.

It should fly like YOU want it to.

So....

The bottom line is: If YOU think it flys tail heavy, shift some weight forward.

forestroke

Thanks for the replies. I will put a little more weight in the front and see how she flies. If I'm already up to 8 oz, I think I will just slap in my 61 4-stroke instead, which will at least take care of 4-5oz.

Also, I was wondering, it seems that my bipe doesn't like to go fast... at full throttle, it is extremely uneasy... should bipes just fly relatively slower? is 9-7 to much pitch?

DBCherry

My Feedback: (4)

Biplanes have a lot more drag than a monoplane like most sport planes, and they will just naturally fly slower. Yes, I think a 9 X 7 is too much pitch. The prop is probably stalling, or at the very least, very inefficient.

I'd go with a 10 X 5 on that 32.

I'm even willing to bet that the change in performance will be dramatic. Try it before you cahnge engines.
Dennis-

forestroke

Thanks... man... i must have three dozen props now of differing sizes/shapes! But it's definitely easier than changing the engine and having strange holes in the cowl :-)

quint-rcu

My Feedback: (24)

My WM Ultimate 30 flew with a series of engines over a long life span - Saito .45, Saito .56 and Saito .72. They are a squirrelly' flier at most higher speeds and ailerons should use lots of expo on the TX. The model needs quite a bit of downthrust and right thrust to compensate from low to full power without excessive climbing and to roll axially to the right and left. The stock CG will work as well as a range 1/2" to either side. The plane needs some pilot skill as the CG is moved aft, but rewards it with crisp snaps and elevator response (expo there too). It should slow down well, but will be skitterish to ailerons if you don't mix in some rudder on landings. Great adrenaline boost for old guys...

quint

forestroke

thanks quint... sound advice! one thing, though, when you say expo, normally we mean negative, meaning that the first half of stick travel moves the surfaces less than the second half of stick travel. are you suggesting that kind of expo or the reverse?

Currently, I am running no expo. I ran with 60% then 30% expo initially but didn't like it.

quint-rcu

My Feedback: (24)

Negative expo is correct to soften the response around neutral. If my memory serves me right, I used 20% on the elevator and 30% on ailerons. Some may like more expo on ailerons, but that is the best feel for me.

quint

promag

I have one with OS 52 4strokes and flies very well.

Check alingment between wings

promag

I have one with OS 52 4strokes and flies very well.

Check alingment between wings

forestroke

Promag... i think what i may not know is how is it suppose to fly.

The 52 isn't any heavier than the 32sx with the amount of lead i've put in front.

The plane just doesn't want to come down. is this normal. If I go half throttle and above it just goes up, no matter what orientation it is in. it can knife edge and still be going up. It literally defies the laws of gravity... have i found the key to anti-gravity?

If that is what the bipe should fly like, then it's a winner and it's just me that needs to adapt to that flying style. Otherwise, I just have no clue what the hell is going on. :-)

Whaddiya think?

DBCherry

My Feedback: (4)

Fourstroke,
Have you flown it since you added weight? If it still climbs like it did, then there's a chance the wing (or horizontal stab) incidence may be off.
Dennis-

forestroke

Thanks Dennis... I will check the incidence tonight as I will likely fly tomorrow!!! TGIF!!! Woohaa!

DBCherry

My Feedback: (4)

You'll generally want the horizontal stab incidence at zero (based on the thrust line).

The lower and upper wings will vary from bipe to bipe though. I think you'll be okay with the bottom wing at zero and the top with a degree or two of positive incidence, but certainly won't guarantee that.

Check the incidences. If anything seems way out of whack from "0 - 0 - 0" then it could be a problem. (I've never seen/heard of incidence settings of more than a degree or two on a bipe.)
Dennis-