Nose down trim in cruise

[caapt]

I finally put two plus two together and realized that my near full nose down trim in cruise was the cause of my slow cruise speed. Cg does not appear to be the problem. Low speed, below say 120 ias, seems fine. But 130-145 results in nose down trim near the limit. It seems to me my horiz stab is not producing enough lift at high speed cruise.
Any one else have this problem?

[Carl Froehlich]

Originally Posted by caapt

SNIP….It seems to me my horiz stab is not producing enough lift at high speed cruise.

This does sound like a rigging issue. I don’t remember for the RV-14. Is there a spacer under the HS forward spar? From you post it seems the HS is providing too much down force. A spacer under the HS forward spar will mitigate that.

But - before you experiment with spacers and changing the HS angle of attack, verify you have it per plans.

Carl

[gotyoke]

Holy moly this sounds scary to me, as a non-expert only 20% through my build. Are you saying you cannot do, say, 75% power no hands without climbing? Or are you saying the fastest level cruise speed is 130-145?

[Bavafa]

The HS of the 14 comes with pre-drilled holes and there isn't much room, if any, for adjustments of incident setting like other RV models such as RV6 or 7. So, it is hard to imagine that the incident is not set correctly.

Have you checked to see how many degree of deflection you get from your trim tab? The older kit had a shorter connecting rod for the servo and VANS has updated that part with slightly longer part which gives more nose down deflection.
Also, it would be good to double check your W&B. Some simple items such as if you don't have the canopy fully closed or seat belts where they need to be, all those could affect your W&B, though probably not to the point that gives you such nose up attitude.

The suggestion to double check the rigging is a very good one as some thing seem to be very off.

[caapt]

I am using the longer arm on the trim tab. I can trim it hands off at 150 rich of peak. But the trim tab is very close to the limit. The real issue is the drag from a deflected elevator and trim tab. This doesn’t seem to be a cg issue. Also, I checked, the HS is right side up
Thanks for the help

[BobTurner]

Originally Posted by caapt

I finally put two plus two together and realized that my near full nose down trim in cruise was the cause of my slow cruise speed. Cg does not appear to be the problem. Low speed, below say 120 ias, seems fine. But 130-145 results in nose down trim near the limit. It seems to me my horiz stab is not producing enough lift at high speed cruise.
Any one else have this problem?

I suggest that you have no trim problem. Your horizontal stabilizer flies ‘upside down’, eg, it develops downward lift. The faster you go, the more downward lift, the more nose down trim you need. Look at the tab. It moves down below the stabilizer more than above it. On the ground, move the trim to the previous cruise position. Go back and look. The tab should be pretty close to level with the stabilizer (depending on cg). As to cruise: more info, please. kIAS, KTAS? What density altitude? Try to compare to Vans’ numbers?

[blaplante]

Also not sure about the 14, but this could be a side effect of wing angle to the fuselage. Is that pre-drilled on the newer planes, or something you have to measure, jig and drill like on the 6 and earlier?

[Untainted123]

Originally Posted by blaplante

Also not sure about the 14, but this could be a side effect of wing angle to the fuselage. Is that pre-drilled on the newer planes, or something you have to measure, jig and drill like on the 6 and earlier?

I believe this is in the plans as 25-02, and appears to come predrilled (referred to as the “F-01405B Bulkhead Bar Assemblies“), on both the spar the bulkhead bar sides.

[Mike S]

Do the flaps reflex up like the RV 10??

If so, are they coming up far enough?

[RViator60]

These are typical cruise conditions for me. On this flight, my gross weight was 1871 and CG was 84.96.