Hey im building a kadet seniorita and was wanting to use the tailfeathers of another plane (mainly for looks). Only problem is, the tail that i want to use, is a bit smaller than the tail for the seniorita. i will try and post a pic, but i have to get it off RCU, cause my hard drive crashed. Will this affect the flight characteristics in a neg way, or will i not notice it? any input is greatly appreciated

Numbers would push this discussion forward.

I've got an old kadet seniorita that I aquired as a basket case. I fixed all of the "impovements" the previous owner did and put it back in the air. It is a great trainer.

My recomendation is to try to keep the area of your redesigned rudder and vertical stab close to the same area of the seniorita. Keep the same proportions of rudder to vertical stab also and things should be good. Using a smaller rudder and vertical results in dificult ground handeling. IE the J3 Cub.

Myself, I would leave it stock and save the creative work for a 4* later.

Don

Andrew,

If the difference is small, you probably don't have a problem. The common recomendation is for the horizontal stab to be about 20% of the area of the wing. If your choice is close to that, again, no problem. As the tail gets small, the plane will become more sensitive to CG position.

Have fun!

Bedford

It'd help to know if you plan to replace just the vertical "tailfeathers" or the horizontal or both.

If the percentage reduction is less than 10%, don't sweat it. For either or both together.

Compare the area of the original with the area of the replacement. Pictures won't help much unless they're the same scale and planform view.

k i got the pics off my build thread. it shows the drawings of both and i have them beside each other, so you can see the difference

The fin and rudder will be fine. The stabilizer and elevator is a bit smaller than it should be. If you're daring you can put it on and start with the CG located about 7 or 8% of the chord more forward than the original and test fly. If you run into troubles where it seems to want to fly differently at high speeds (likely seem like it wants to tuck into a dive when flown fast) compared to slow then it's too small and you're on the ragged edge. Putting the CG forward like this will let the model fly but you MAY need to help it recover at some points as noted. As long as you're OK with that level of flying then fine. If not then I'd build a new stabilizer from the original plan or use the other plan but "stretch" the stabilizer size using a photocopier enlargement to bring it up to where it's within 10% of the Kadet's original size if the looks are what you're after.

The Seniorita has a flat bottom with with lots of camber. That results in an airfoil with lots of pitching tendency. The large stock stab counterbalances this tendency. If the wing had a symetrical airfoil then you could get away with quite a small stabilizer much like you show.

No guesswork on the CG for the smaller tail. None at all.

Take the measurements of the airplane to geistware.com and plug them in. Simple as that.

When you reduce the tail volume (area:moment) it reduces the CG range. You have less room to move it fore/aft. And when it shifts, the efficiency of the tail changes more. As does the ability of the tail to restore pitch.