Not sure I'm in the right part of the forum for my questions/comments, but here goes:
The plane is a Thunder Tiger Lazy Tiger Cub, supposdly a low slow flyer which seemed fitting for my 71 year old reaction time. I've been flying either rc or full scale or in chopper aircrew since 1957 so I' not exactly a "newbie", but I'm looking for opinions.
The engine is a TT.36 Pro, the plane is about 5 lbs. not the 2.5 lbs. it was supposed to be, there is no logical reason for that, unless they thought one might use mini servos and a one cell reciever batterypack, in other words I don't think anything I did caused an unusual amount of added weight.

1) what problems can one expect if a plane is overpowered ?
2) what can one expect if plane is nose or tail heavy ?
3) what would cause a plane to "porpose" (spelled wrong probably), but at any speed the plane wants to climb or dive, correction for one creates to other.
4) what could one expect if the plane was too heavy ?

Any comment would certainly be appreciated, I am attempting to find a .25 size engine because the problem is definately worse at high speeds.

Thanks in advance for any feedback.
Dan

1) Torque roll and over stressing the airframe

2) Nose heavy-Doesn't fly well, Tail heavy-flys once.

3)Porpoising is related to a rearward CG, try moving it forward 1/8" at a time.

4) Higher wing loading will cause much faster landing and takeoff speeds.

1) excess stress on the planes structure if performing high G manouvers though I do not feel your engine significantly over powers that plane.

2) A nose heavy plane will tend to need to fly faster and land faster and the elevator and rudder would seem sluggish to react. Plane likely drops the nose when you throttle down. If it is tail heavy the tail will drop (nose rise) as you throttle down and the elevator and rudder will seem sensetive or twitchy. Landings are very hard due to the tail falling as you try to slow down.

3) This can be caused by balance as described above but may also be cause by engine thrust alignment. If the engine is pointed up to far from the designed thrust line the plane will climb under power and if the engines is pointed down to much it will lose altitude under increased throttle. In these situations fighting the engines thrust alinement with the elevator can cause a porposing effect.

4)Higher wing loading and faster landings.

The thundertiger page shows this plane to be 4lbs when complete.

Good luck, I hope this helps.

Do not change your engine. Check your center of gravity. You do not have to fly it with full throttle all the time. Buy a H-9 Toledo special it flies great!

Thank you all for your replies, in the for what it's worth category, the balance is dead on according to the assembly instructions as was the amount of engine down thrust. I have reduced the down thrust to 0 relative to the wing incidence and that did help VERY slightly.
I'm still unsure of which way to go with the CG, but I think I'll try moving it back a bit, I'd rather err on the nose heavy side than tail heavy, I like 1320Fastback's comment "nose heavy doesn't fly well, tail heavy flys once".
Again thanks for you info, I'll do something even if it's wrong.
Dan

No you want to move it forward, moving it back will make it tail heavy, I test flew a plane for some one once and Holy cow did that thing "porpose" (i don't know how to spell it either LOL) but I did get it on the ground, It was for a older gentleman that I consider a friend too and when I got it on the ground he came over and sai "boy I guess i should have checked the CG as I slapped me head. He was very tail heavy so try moving some weight a little forward to the nose and see if it improves a little.

Dauntae

I've always been glad the "plans" tell you where the CG should be and I've never had a problem staying within the specified range until this little bugger and I'm really glad 'cause now I'm really confused.
For the type of plane it is "supposed" to be it is necessary to keep up a lot of speed on landing or the prop will throw up a whole bunch of grass !!! From earlier info I'm "guessing" that MAY mean it's nose heavy even tho the balance point is dead on according to the plans.
After rereading, maybe I said it wrong in my earlier post. The fact it "porpoises" AND has a fast landing speed is what confuses me. Thanks for correcting me on which side of the CG I need to add an ounce or two to see what happens.

Dan
Note: I spelled porpoising like 1320Fastback and didn't get all the red squigly lines lines telling me it was misspelled, now squigly has 'em, I give up !!!!!!

I just use the spellchecker before I post and that clears up those tricky words

On to the CG issue.

Depending on the maker the manual could very well be WRONG! Nitroplanes.com has a few models out that if you were to follow the build manual you would be in for a quick flight resulting in lawn dartage.

How "level" does the horizontal stabilizer and fuselage (another tricky word) look when the plane is resting at CG?

The only info I can find is that the CG is from 3.5" to 3.75" back from the LE.

I think you two might be talking about two different kinds of porpoising! What Fastback is describing for a tail heavy plane is more from over sensitivity in the controls, which in turn causes some over correction with the sticks and will occur at a lower speed as well as at faster speeds. This will sometimes smooth out briefly during acceleration.
The porpoising from a nose heavy plane is smoother and more predictable and does require faster landing speed to overcome. Just my 2 cents

This was an ARF (ha ha) and it was put together with tender loving care 'cause I KNEW it was going to be fun. I was actually surprised at the minimal amount of positive incidence of the wing relative to the horizontal stab for this type of plane, but left it alone. I did at one point in time shim the leading edge of the wing up about an 1/8 inch, with no real big change in how it handled, altho it did seem to climb a bit more than before, and when it decided to go down it still went. After reading your post, I checked out the "levelness" of the stab with the wing AGAIN, and they are very close to 0 incidence, with the wing slightly more positive which seems normal to me. The other area I had corrected some time ago was some up thrust in the engine, I shimmed it to 0 relative to the bottom of the wing. I believe that along with throttle management made the most difference but IT STILL SUCKED!!!!
As far as the control surfaces, I've cut the elevator back from 3/4 inch throw (I like TIGHT loops) to 1/2 inch, plus I've got Expo. (won't even try to spell it) working for me too.
My manual also says balance at 3.5 to 3.75 from the L.E., I just use my fingers, but it's right in the middle of my fore and aft marks on the wings. I did add "some" weight when putting it together. There places that were in bad need of more glue, mostly I used CA to make it easier so it didn't add much. Also the push rods for the rudder and elevator were 3 sticks and 6 rods exactly like my Senior Telemaster which gave me fits due to elevator "flutter" so I modified the elevator by connecting the 2 halves with hard wood (MAYBE an ounce) and used Nyrod. The Nyrod was one of the first things I checked after the first flight thinking they might be flexing, NO WAY.
I really appreciate you guys trying to help and I believe you have, it'll be a few days, but I'm at the point I think it's basically balance, and I'm going to move the batteries forward (if I can) and if that doesn't work I'll move them back (if I can), and if I can't move the batteries I'll stick on a little weight and see what happens.
My Sr. Tele and Rascal are just fine so if I break this little sucker it won't be the end of the world.
Again I thank all of you for the info.

Dan

I was told when getting my private license years ago there are 3 things in aviation that are ABSOLUTELY WORTHLESS-

THE RUNWAY BEHIND YOU,THE AIR ABOVE YOU, AND THE GAS YOU LEFT ON THE GROUND.

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