RVG8tor

RVG8tor

Well Known Member
I know the RV-8A will have need for trim since the CG changes with the back seat filled. I fit my trim tab push rod the other day after talking to builder support at Van's. It was in that discussion that I learned that with the electric trim you do not get as much travel as with manual trim. Gus thought I would get approximately 50 degrees of travel and to bias this to nose up trim (tab trailing edge down) So this is what I did, I discovered that approximately 50 degrees of travel is really 45 degrees with my set up.

I biased mine so I get 29 degrees nose up trim and about 16 nose down. My question is should I keep this until I fly or should I adjust it to give me a bit more nose down trim? Some information might help, I am a big 260lbs, I have the battery just behind the firewall, a full IFR panel but not extreme. Engine is an IO-360 but I have the WW prop to lighten things up some as well as magnesium wheels. My guess is I will be flying with a forward CG but Scott at Van's does not think I will have any CG issues, the Vans' RV-8A has the 200hp with the battery on the firewall and he said they don't have issues. I think the gear being under the spar helps offset the nose gear CG effect.

Looking forward to hearing what you guys flying feel about your trim tab settings.

Cheers
 
Hi Mike
I have an 8A with electric trim and have never run out of travel. Solo on short final I have a little more than half travel nose up dialed in. At the other extreme, big pax at cruise speed, I'll have about the same nose down set.

Have you done your W&B numbers yet? I'm about an inch from the fwd limit with no baggage. For first flight I had everything neutral, no bias, and after a few flights wound up adjusting about 5 deg nose up bias.

For takeoff solo, I put about 5 deg. nose up and with a pax neutral.

Paul Danclovic
Jamestown NC
RV-8A N181SB
 
I tried to build light: 1090 lbs empty. I also have a whirlwind prop and the battery behind the firewall. I weigh about 180. I run out of nose up trim on final when solo. I have not biased my trim tab, and did not know it was acceptable to do so. I will bias mine now that I know that.

I would suggest starting with yours where it is.
 
What Guy said. My plane has the battery in back and a WW prop and weighs 1095 empty. When solo I run out of nose up trim on final. I've never run out of nose down trim.
 
RVG8tor said:
I know the RV-8A will have need for trim since the CG changes with the back seat filled. I fit my trim tab push rod the other day after talking to builder support at Van's. It was in that discussion that I learned that with the electric trim you do not get as much travel as with manual trim. Gus thought I would get approximately 50 degrees of travel and to bias this to nose up trim (tab trailing edge down) So this is what I did, I discovered that approximately 50 degrees of travel is really 45 degrees with my set up.

I biased mine so I get 29 degrees nose up trim and about 16 nose down. My question is should I keep this until I fly or should I adjust it to give me a bit more nose down trim? Some information might help, I am a big 260lbs, I have the battery just behind the firewall, a full IFR panel but not extreme. Engine is an IO-360 but I have the WW prop to lighten things up some as well as magnesium wheels. My guess is I will be flying with a forward CG but Scott at Van's does not think I will have any CG issues, the Vans' RV-8A has the 200hp with the battery on the firewall and he said they don't have issues. I think the gear being under the spar helps offset the nose gear CG effect.

Looking forward to hearing what you guys flying feel about your trim tab settings.

Cheers
Click to expand...
I'd say you've got it about right.

Surprise! Even a light 8, with a Whirlwind prop, is nose heavy solo with the battery mounted up front. There is No way a 200 hp 8A with the battery mounted on the firewall is not nose heavy.
 
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Position for first flight

Could use your help for setting the position of my tab for first flight.

Just did weight and balance, pretty light at 1062 lbf and 79.92" empty. When I did the Skyview calibration I just picked zero angle relative to the the elevator as mid position.

What distance above or below the elevator is your tab for take off?
 
Ballast

One of the requirements when you do paperwork for the airworthiness inspection is a first flight weight and balance. I chose to add 40 lbs of rear seat ballast for the first flight. This will probably help you if you do something similar. I would use enough ballast to place your CG in mid range and go from there.

Five gallons of water in plastic containers is my plan.

Don
 
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