RV6 elevator trim

[PaulvS]

Hi Paul
The rear wing spar attachment to the fuselage seems to be centered with proper edge distance which is odd because you would expect the wing spar and fuselage spar to be misaligned by 0.6” as you calculated. I checked the other wing and it is also off by 1.3 deg. I’m not sure how it happened but 1.3 deg is significant but it might be something I have to accept. Increasing the AOI of the horizontal stab any more would put more stress on the rear spar of the stab. I probably will end up removing a washer just to insure there isn’t too much stress on the rear spar. And maybe I should add a thin washer on the lower bolt holes on the rear stab spar to further reduce stress, not sure.

Worse case I only use one washer and live with excessive trim.

Dwg 34 has the details of the HS and VS attachment and the spacer for the HS is not a washer(s), it is 2"x1" 2024-T3. This is obviously a critical location that should be secured with the correct hardware and bolt lengths.
The way to avoid stressing and flexing the vertical stabilizer rear spar is to re-fabricate the attachment plate that connects the VS to the HS. This is normally fitted after the VS and HS have been installed in their final positiions.

 

[FireMedic_2009]

I agree. I flew today and I only needed to trim half as much. I was thinking I would replace the washers with 1x2x1/8” plate to match the original one that was there to give it a better base. Yes, I did replace the bolts with longer ones.
Thanks

 

[amckeen]

I agree. I flew today and I only needed to trim half as much. I was thinking I would replace the washers with 1x2x1/8” plate to match the original one that was there to give it a better base. Yes, I did replace the bolts with longer ones.
Thanks

Use of washers to shim the horizontal stabilizer as described in manual section 15 is acceptable. The most common slow build RV6 can lack the precision of newer pre-punched kits. Builder made fuselage jigs and old style leveling without use of lasers and digital tools could lead to minor variations in precision. Wings were usually rigged during final assembly at an airport after the stabilizer was rigged in the shop. Getting the rear edge distances was more essential than a digitally accurate wing AOI. Homebuilt construction jigs and use of low tech measuring tools during construction can lead to some lack of precision in older constructed slow build kits that fly very nicely.

If the after test flight trim tab angle is less than 10 degrees up ask noted in manual section 15 then your stabilizer AOI appears acceptable.

 

[pylet2000]

I agree. I flew today and I only needed to trim half as much. I was thinking I would replace the washers with 1x2x1/8” plate to match the original one that was there to give it a better base. Yes, I did replace the bolts with longer ones.
Thanks

When you made the adjustment with the washers, did you have any issues with the fuselage to horizontal stab fairings fitting?

 

[Bicyclops]

You could gauge how much the vertical to horizontal mount has changed by removing the 4 bolts through the horizontal stab and seeing how much it covers the holes once it's relaxed and the vertical is straight. It might be possible to file and then ream the holes for AN4 bolts while maintaining edge distance. Don't go below 2x hole diameter. Large area washers can provide better support as shims also.

 

[FireMedic_2009]

When you made the adjustment with the washers, did you have any issues with the fuselage to horizontal stab fairings fitting?

Yes, definitely would need to be reworked