Horizontal Stab Mounting Issues (RV-7A)

UnPossible · #1 11-01-2009, 04:58 PM

Hey - I'm working on mounting the horizontal stab to my RV-7A QB and I'm running into a couple of issues.

1) I'm trying to level the fuselage and the tail. Not sure if this is critical but I figure it can't hurt. The first picture below is a level placed on the longerons in the cockpit area. As you can see, its pretty darn level.

The second picture is a level placed on the 1/8" spacers back on the tail. As you can see, its off a bit (0.3 degrees)

Should I mess around with a thicker shim on the one side to level this out - or is this close enough and nothing to worry about (or is there some design reason I'm not aware of for this difference?

2) When I place the Horizontal Stab on the shims and place the 3/16" spacer to set the incidence, the tail is not level w/ respect to the fuselage. If I increase the spacer to 9/32, the tail is level with the fuselage in the cabin area. I'm assuming that being level is more important than the spacer gap.... If not, please let me know.

Thanks,
Jason

Mel · #2 11-01-2009, 05:34 PM

First I would check that the level at the wing spar carry-through is level with the longerons. The tail should be leveled with respect to the wing. In other words, level the main spar carry-through and level the horizontal stabilizer with respect to that.

Kyle Boatright · #3 11-01-2009, 05:40 PM

Quote:

Originally Posted by Mel

First I would check that the level at the wing spar carry-through is level with the longerons. The tail should be leveled with respect to the wing. In other words, level the main spar carry-through and level the horizontal stabilizer with respect to that.

Bingo. Would a water level on the wing attach points be a good leveling solution?

Mel · #4 11-01-2009, 05:48 PM

Quote:

Originally Posted by Kyle Boatright

Bingo. Would a water level on the wing attach points be a good leveling solution?

Sure, that'll work. But wouldn't it be easier just to set the level on top of the main spar carry-through?

jsharkey · #5 11-01-2009, 05:51 PM

My RV6 has different thickness shims on either side to level the HS with the wing spar carry through bulkhead.

Jim Sharkey
RV6 - Phase 1

L.Adamson · #6 11-01-2009, 06:06 PM

Quote:

Originally Posted by jsharkey

My RV6 has different thickness shims on either side to level the HS with the wing spar carry through bulkhead.

Jim Sharkey
RV6 - Phase 1

Slightly different thickness in mine too. And everything lines up well..............as it's dang fast for a six!

Beats the 9's in fuel conservation too...

L.Adamson --- RV6A

UnPossible · #7 11-01-2009, 06:12 PM

Quote:

Originally Posted by Mel

First I would check that the level at the wing spar carry-through is level with the longerons. The tail should be leveled with respect to the wing. In other words, level the main spar carry-through and level the horizontal stabilizer with respect to that.

Mel - I just want to make sure I understand what you are saying... I placed a level on the main wing spar. (See pic below). When I leveled this out, the tail/horizontal stabilizer was also level... so I should be good to go if I'm understanding you correctly.

Anyone have any thoughts as to needing a 9/32 spacer under the rear spar of the HS stabilizer to get HS level with respect to the longerons in the cockpit area. Is there a better area to determine level front to back?

Thanks again,
Jason

Mel · #8 11-01-2009, 06:26 PM

Quote:

Originally Posted by UnPossible

Mel - I just want to make sure I understand what you are saying... I placed a level on the main wing spar. (See pic below). When I leveled this out, the tail/horizontal stabilizer was also level... so I should be good to go if I'm understanding you correctly.

Yep, You got it.

L.Adamson · #9 11-01-2009, 06:27 PM

Quote:

Originally Posted by UnPossible

Mel - I just want to make sure I understand what you are saying... I placed a level on the main wing spar. (See pic below). When I leveled this out, the tail/horizontal stabilizer was also level... so I should be good to go if I'm understanding you correctly.

Anyone have any thoughts as to needing a 9/32 spacer under the rear spar of the HS stabilizer to get HS level with respect to the longerons in the cockpit area. Is there a better area to determine level front to back?

Thanks again,
Jason

Since Mel is offline.... edit... Mel is again online

You can't count on the rear deck as being exactly level with the wings. The horizontal stab needs to be (now that you've seen that the fuse is level with the wings) ---- so shim to make it perfect. When you stand in front of the plane, you'll want to see the wings and horizontal exactly parallel.

L.Adamson

Mel · #10 11-01-2009, 06:28 PM

Quote:

Originally Posted by UnPossible

Anyone have any thoughts as to needing a 9/32 spacer under the rear spar of the HS stabilizer to get HS level with respect to the longerons in the cockpit area. Is there a better area to determine level front to back?

Just make sure to check EACH longeron in the cockpit area. If they are not exactly the same level, average them to set up the tail.