glowfuel

Need further help,

With power off, what will truely cause this sailplane to pitch (porpoise) up then down?
Kind of funny, because the CG is set on the main spar.

Would not do it all the time, possibly nose heavy?

Seems to be much much worse when landing and going slow.


Also, need to find a more powerful 7 cell, brushed motor for it. Any suggenstions?As an FYI need a motor with a longer shaft.


Thanks in advance.

rscarawa

I left some motor recommendations in the other thread.

As the plane becomes nose heavy, it tends to porpoise. You should never totally get rid of this (atleast in a Spectra/Spirit) as this tendency allow you to trim the plane for speed. But as you make the plane more tail heavy and start feeding in down trim, the time and distance between crests increases for a given speed. As the plane finds it preferred speed and pitch for a trim setting, the oscilations will reduce and eventually stop until the plane is upset again. This can happen by wondering into a thermal or touching the elevator.

When determining a balance point, some people use the dive test to determine this. Search around online for this test and using it only as a starting point. You can fine tune from this point.

This is a personal thing, but when l flying a straight line, use the elevator only to keep a constant pitch. This pitch should be one that allows the plane to fly at the speed you desire. Then trim the plane to hold that pitch. When possible, try to avoid using the elevator when thermal searching since you are using the plane to feel the air. You need to know the difference between a thermal upsetting the plane and stick induced motions.

pcsketch

As to your looking for more power:

I belonged to a small group of 2 meter electric flyers. We go into a search for 'more' power; gearboxes, folding props, 8-9 cell pack and 'hotter' motors. Spent lots of time and money on better wire connectors, matched cells, pulse charge chargers. Our $150 investments grew to more like $300.

Competion got hot. All up and last down. Real hot pilots.

Then a new flyer joined us. Stock Electra (yep, back in the 90's) direct drive 8X4 prop and a stock 6 cell car pack. Waxed our asses! Was the first to find lift and got to be normal for him to be last down.

Why? He spent his time learning how to find thermals, and work the last bit of lift.

If you want a faster climb and lighter weight go spend your money. If you want to become a hot thermal pilot. Go Fly.

Thermal experience: Electra, Spirit, Spectra, Gental Lady (converted electric), Bir of time (converted to electric), and every 'gassy' I've owned has thermaled to!

Bill Drummond
Salem Oregon where you fly between the rain.

aeajr

My Feedback: (2)

Sounds like it is nose heavy. When it is nose heavy you will tend to trim in more up to keep the plane flying level when it is gliding. As it picks up speed it will climb, stall and drop, pick up speed, climb, stall and drop.

Try moving CG back.

As I recall, my Spirit has the CG behind the spar, 3 1/4" behind the leading edge. What does the Spectra manual tell you to do. I believe the Spectra balances the same way. Spectra is a Spirit with a motor.