RV4 HS incidence

[RyanB]

Hi everyone

I am fitting an O360 and a Hartzell blended aerofoil prop in my RV4. With the extra weight up front does anyone have any ideas as to wether or not the tailplane incidence called out for in the plan is sufficient or did you lift the trailing edge of the HS to counter the extra weight?

Thank you so much

[Skysailor]

My RV4 also has an O-360 with constant speed prop. I actually had to shim the leading edge up .032 from the plans shim on the main spar of the stabilizer. The plane will be very fast. The additional shimming allows the elevators to be faired at cruise speed. I recommend you do not finalize and paint your tail to fuselage fairing until you fly for this reason.

[DeeCee 57]

good advice from Skysailor.

the tailplane incidence called out for in the plan

Well, it's been a long time I built the -4, but I recall the manual stating a max value that could be set down to 0° angle depending wether you'd want stability or speed... is it still so?

[RyanB]

Hi Guys

Thank you for the valuable info. I will recheck the plans and instructions again, but will initially stick to the plans and adjust during phase 1.

Much appreciated

[Skysailor]

I would suggest you pre-drill some shims of various thickness. This way, you can simply remove the horizontal spar bolts and insert a shim without having to take apart the entire tail to get the spacing of the holes exactly correct. Very easy to do now without the vertical in the way. Any of the shims you make which you do not need are simply very small scrap. The shims I mention are in addition to the one called out in the plans.

[Christopher Murphy]

I added .125 on my HS but If you have drilled your verticle stab rear spar and the front spar raising the HS front spar will impart a bending load on the rear VS
spar. I ended up re drilling the forward VS spar. While re drilling forward Vs spar I moved the leading edge 3/8 left and it had basically no effect on longitudinal trim.

Just my experience...

Cm

[BruceW]

Im still wondering what incident occurred to your HS ???

[larryj]

I'm working on a Rocket so there are slight differences to the -4 but the principles stay the same. I'm using the standard -4 tail and word from Harmon is to add a 3/16" shim under the forward spar. Word from Team Rocket is to set the HS incidence to the same as the wing.
I'd like to hear data in terms of incidence angle because adding shims doesn't define anything aerodynamically.

I'm also interested in hearing about VS alignment. I've changed my thrust-line to zero yaw and am planning to zero the VS as well; then trim for cruise with the Gear Leg Fairings.

Does anyone have any experience with these sorts of approaches ??
And I hope this only expands the OP's question and isn't a hijack.