Thrust lines & ROG's

[Bud Shupe]

Howdy,
I have a Mini-Max that flew really great until an unfortunate incident with a steel storage container. It was rebuilt, however, with balsa. It is within grams of being the same weight ( a little heavy, due to reinforcement and epoxy). The front half of the fuse and the motor mount are all new. It flys beautifully, maybe better than before, but I have to hand- launch now and can't do ROG's.
I know the thrust line is different now but can't figure out which way to go. I think the motor actually may be to low on the fuse with respect to the leading edge and the prop- wash is all wrong.
Can anybody help?
Thanks,
Bud

[stegla]

The repair may have made the plane......
1) Nose heavy?
2) More downthrust than previously?

These plus any gain in weight could make your model reluctant to lift off.

Steve

[Vonbaron]

Bud, does the Mini Max run along the ground at about the same speed as before or does it seem more lethargic? Could be the extra weight. The triangle foam fuse is very light compared to balsa. If it's a weight problem try a GWS 8x6 prop instead of the stock one and add an extra cell.

If you think the incidence may have changed you could always try to shim up the LE of the wing and see what that does.

Too much downthrust on the motor could make things difficult for ROG too. It's really hard to tell without seeing it.

Is the Center Of Gravity still correct? A nose heavy plane may not ROG as well.

Prop on backwards? I'm just shooting in the dark here.

[Bud Shupe]

Hey VonBaron, Thanks for the tips. I'm going to experiment until I get it right. Like I said, it flys great, just no ROG's ( the prop COULDN'T be on backwards).
Sorry about your Mini-Max. I guess we all know how it turned out. Did you look at the cow-pies to see if any parts were left ?
Bud
p.s. Don't shoot in the dark. You could hit someone.

[Vonbaron]

Hehheh. I couldn't hit anyone if I shot in the day time.

I forgot, the Mini Max prop is flat on one side, unlike the GWS props. Do try a GWS 8x6 though. It helped mine.

The cow spat the parts out again. I made a new rear fuse from balsa and it flies fine.

Good luck.

[Gene Bond]

Sounds like a couple of mine, I have to get up to flying speed on the ground before they will take off. The problem is the angle of attack. With a tail dragger, the AOA is pretty high with the tail down. once it gets going, it lifts the tail and is flying, while contacting the front wheels. With a more level attitude, it requires more speed to get the lift, since the vectors are so flat, and you can't drop the tail to get a higher AOA.

Make any sense? Could this be it? If so, maybe longer fron gear, or shorter tail gear would solve it.

My BigBlu has to go about 100' before it will lift off, but hand launches easily. My Double Trouble need 20', and then will go vertical!