Rudder Stab
 

Hi there. I am building a Sig Kougar and come to find out
my rudder stab is tilted just slighty. will this effect anything?
I would say it's off about a 1/16 to a 1/4 or so.. :(
Its almost done and look's very nice.. I now wish I didn't
take a NAP while the Stab was drying *LOL* I was wonder what this can do to flight when I am ready to try it out..
looking at it from the rear strieght on, it leans a tad to the right
thanks..
Jeff

Rudder Stab
 

This is not good, your plane will corkscrew through loops just to name ONE of the problems. IMHO, cut it off and re-glue it.

Note* Next time, after the epoxy is on and everything is straight, lock down the ends with some CA and accelerator to keep the alignment while you nap :)

Rudder Stab
 

:eek: Darn.. Thats what I didn't want to hear! Oh Well
I guess I will CUT it off.. Whats the best way of doing that
without wrecking it? before I start that project..
thanks
Jeff

Rudder Stab
 

Hi Cougar,
you can add flying wires to pull the stab over,or shrink the covering with your iron,also sometimes pulling the stab over and adding tristock at the base as fillets will line it up, or saw it off with a hacksaw blade or similar device.

good luck, John.

Rudder Stab
 

As long as you are happy with how it looks I'd fly it first before you cut. Cutting will probably add weight and/or weaken the tail. If it is only 1/8" out then most pilots would probably not notice.
Leonard

Tilted Fin
 

I would fly it first to see what the effect is before desiding what to do. After you get the plane thoroughly trimmed out you can choose between living with the effect of fin tilt (if any) and redoing the fin alignment. If you do deside to cut the fin off, a razor saw will leave a smoother and narrower kerf than a hacksaw.

Rudder Stab
 

Unless you have a very small plane, I don't think 1/4 inch at the top will make much difference. I would not worry about it. If you do have problems, add flying wires to hold it straight.

Rudder Stab
 

Thanks Guys I will fly it first then! You folks are wonderful!
Its not off very much at all, very slight tilt..
Jeff

Rear view, Take a look
 

Here is a Picture of the rear view.. Umm looks better
in the pic. *LOL* Plane is almost done this is only my 3rd
plane I have built.. I have better luck building modle helis! hehe
:D ( NOTICE the Trim On the WALL next to the Cub Wing)
that will show you how far off it is
Jeff

Another View
 

one more pic..
I still have to add just a little more blue
trim on the wing. and maybe somthing under the
wing for noticing top and botton when flying I guess.

Rudder Stab
 

I tried an image program on your picture that has the ability to measure angles. I tried the TE of the stab, but from the image, the TE is not straight. I tried the difference in the angles of the top edge of each wing, and then differenced that to the angle of the vertical stab.

From what I can discern, the stab is 0.72 degrees to the right.

In my opinion, you will never be able to tell in flight that the vertical stab is off by ~ 1 degree.

Fly it first, and then judge for yourself. You've already done the finish work, so the amount of work is no more or less if you fly the plane first.

Rudder Stab
 

Soar Head
Wow. Thanks! thats kewl that you could
tell that from the pic..
agian THANKS!
Jeff

Rudder Stab
 

Correction.

I redid my angle measurements twice, based on the angle of the vertical stabs and the angle measured off of the LE of each wing.

One measurement showed the stab is leaning 1.7 degrees to the right. The other measurement set showed 1.9 degrees to the right.

These are basically twice my previous estimate.

The force the rudder generates is normal to the angle of the vertical stab. Ideally it should generate all moments at 90 from vertical. If your stab leans approx 2 deg. to the right, then it will generate a small moment in the vertical direction.

It is possible this force may be discernible by you. Flight testing will tell for sure.

Rudder Stab
 

Soar Head.. So this shouldn't make me crash
right off take off will it?
I should be able to get air born?
then see how it handles?
thanks for all your doing.
Jeff

Rudder Stab
 

>So this shouldn't make me crash
>right off take off will it?

Don't worry, it won't do that! The best way to see if there is any noticable effectl is to choose a calm day, trim the a/c to fly straight and level hands off, then apply full rudder. Note if there is any pitching up or down (this is quite normal). Now set it up straight and level again now apply full rudder in the opposite direction. Any difference in pitching is probably (although not necessarily)due to the non-vertical fin.
regards,
Leonard

Rudder Stab
 

LeonardN
Thank you Sir!
Jeff

Rudder Stab
 

To my understanding, that leaning stab will cause a diving condition to the right and climbing to the left. One or two degrees probably won't make it unflyable but you should be careful.

Fin Tilt
 

A fin tilt of two degrees will only produce an unwanted vertical force about 3.5% as large as the horizontal force produced by the rudder. Such a small force will hardly be noticable even with large rudder deflections and will be zero if the rudder is not deflected.

Rudder Stab
 

Now I really have to get this thing air born to let you folks know!!~S~

Rudder Stab
 

That fin is perfect.

Rudder Stab
 

I have seen a lot worse then that on some of my students planes and they flew fine. A little trim to compensate is all that was needed, now go and fly and goof no more!!!!! ;)

vertical stabilizer OFF
 

I'm building a Genesis Cap 232 in 25% where the FG fuse stab is off too, a total of .200 over the length of the vertical stabilizer ( 12"). I was told that this is normal to offset engine torque and will help in certain flight conditions. I am very skeptical?!?!

Rudder Stab
 

A rudder that is aligned to the centerline may not be aligned to the local flow at the tail because propwash introduces a spiral component to the flow around the fuselage. Not only that, but, the torque produced by the engine causes a roll reaction which must be compensated to trim for straight and level flight. This compensation can be acomplished in a number of ways, including offsetting the fin, the rudder or the ailerons. Many fullsize aircraft use an offset fin for torque roll compensation.

Yep
 

True, Ollie.

The vertical fin on Raytheon's King Air has a 1 degree left twist in it. (a right rudder effect)

Rudder Stab
 

Now Im not sure on the size of your plane, but i have a kadet
senior with quite a bit of tilt to the horz. stab. It flies great , but one flight problem it has is that it makes its own slight turn--could be me--lol. But I really dont think you need to worry about it. Ive built and see worse fly.