N1EDM

My Feedback: (2)

Hi,

Someone left this old beast at our field in rather poor condition. I put her back together and installed a Hacker electric motor in it. The maiden didn't go so well, so I thought I would ask for advice while I make repairs.

The wing has a 67" span and the fuse is about 38" long. She's a 3-channel bird with an undercambered airfoil for the wing (which was part of my downfall) and a flat-bottom airfoil for a lifting stab. I thought I would balance her at about 40% back from the LE but that appears to have not been enough.

My other mistake was trying to launch her on a windy day thinking that I could (ahem) handle her... well, nope. She was all over the sky and I had all I could do to get her back down on the ground with minimal damage. She was obviously tail heavy.

OK, so my questions are.... with a wing/stab setup like that, where should I have balanced her?

Also, does anyone recognize her??? From what little I could tell, that little lady did NOT want to come down. That undercambered airfoil was really doing its job!!! With the gusty breeze (yeah, I know, bad headwork) I had a tiger by the tail trying to get her on to the ground... I don't want to make that same mistake twice.

I have the feeling that once I solve these problems, she should be a very nice flying airplane.

Thanks,

Bob

bassindon2

I think that you would be wise to balance it on the main spare as a first attempt. I would think that might give you the results that you want.

Sorry but can't help with the identity.

billmod12

My Feedback: (1)

I am no authority but it sure looks like a Play Boy cabin. The ones I have flown definitely do not want to come down. They do have a tendency to reach for the sky and do not take over powering very well. I am sure that someone that knows the in and outs of converting these old free flights will come to your aid. Cheers! Bill

Lnewqban

Bob,

I believe that the model is a cabin Playboy; check the attached drawing.

I have found this old thread about another Playboy:

http://www.rcuniverse.com/forum/m_21..._1/key_/tm.htm

Best of luck!

Strat2003

My Feedback: (1)

Yep, it's a Cabin Playboy.
My Playboys are balanced at between 50% and 55% of the chord. They will handle power (I have an 80" one powered by a Jett .35) but they have a tendency to nose up strongly under power. You can fight that with downthrust and down elevator trim in the climb.

LesUyeda

Looks to me like that thing has a lifting horizontal stab. That changes everything you ever learned about CG.

Les

pimmnz

N1EDM, these things were designed for a fairly rapid climb, then a glide, all with no assistance from the owner. He just starts the thing, then throws it away. To survive, it has that high, polyhedral wing, large tailplane, and careful trimming to cope with the engine run, then the glide. The 'lifting tailplane' idea (all tailplanes lift!) was to help a contest rule that specified a wing area/engine size/fuel allotment to give better duration after the engine stops. Now both the climb and glide were SINGLE SPEED conditions, and were trimmed by having a rearward balance, and a spiral climb/turning glide. OK, now you introduce a rudder, elevator, and throttle controlled engine. These things will all VARY the speed, and this design won't like that at all, unless you do some mods. First, move the balance forward, so that the tailplane is MOSTLY providing a downward lift. This will help stabilise the pitch reaction to the varying speeds. Start about 30% balance. Then check the angular difference between the wing and the tailplane, and lift the tailplane leading edge to give you around 2 degrees difference, the wing being the greater angle. The other thing these things exhibit is very powerful yaw/roll couple, ie it responds real well to rudder, particularly under power, but then it might be pretty unresponsive on the glide, so you will need lots of rudder, but you must exercise care in the use of. Control the climb angle with the throttle, and the glide speed with the elevator, and be careful when launching. The glide speed will be SLOW, so that will restrict the wind speed you can fly in. A calm weather model it will be.
Evan, WB #12.

Bax

My Feedback: (11)

You will also need to adjust the engine's thrustline so that you minimize pitch change with throttle change. If you have the model trimmed for straight-and-level flight when you have the throttle set to "cruise" and it will pitch down strongly when you reduce the throttle to idle, you need more downthrust. You also need downthrust if the model will pitch up sharply with throttle application. Reduce downthrust if the model will pitch up when you reduce throttle.

With such a floater-type of airplane, with the deeply-cambered airfoil, you may want to put the wing's incidence closer to zero....it depends upon how you want it to fly. Trimming such a model is half the fun of owning one.

Remember, it was designed mainly to be a glider. That type of model would have an engine run of only a few seconds before the engine quit and it transitioned into a glide. You'll likely find that it will do best at very low power settings...or even with the engine shut off and the model doing its thing as a glider.

Strat2003

My Feedback: (1)

As Bax says, it depends on how you want to fly it.
If you want to fly it climb and glide in limited engine run events, the original setup will work pretty well. Downthrust and down elevator will work in the steep, short climb and the glide will be great with just a change in elevator trim. If you want to fly it as a conventional sport model the suggested changes will make it more familliar.