UnPossible

UnPossible

Well Known Member
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.

t7lgs5.jpg


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)

zjawr6.jpg


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
 
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 said:
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.
Click to expand...

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

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
 
jsharkey said:
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
Click to expand...

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

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

L.Adamson --- RV6A
 
Mel said:
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.
Click to expand...

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.

330fxbb.jpg


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
 
UnPossible said:
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.
Click to expand...

Yep, You got it.
 
UnPossible said:
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.

330fxbb.jpg


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
Click to expand...

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
 
UnPossible said:
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?
Click to expand...

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.
 
Thanks all for the quick responses.... I really don't know if I'd have a chance of building a plane without VAF and all its helpful folks.... much appreciated.

Thanks,
Jason
 
Personally.....

...I didn't have a smart level and the old bubble level was all we used....couldn't detect .3 of one degree and I'd bet you wouldn't notice it standing in front of the airplane either.

Not making fun of your effort, just that there are quite a few RV's flying really well and really fast, before the advent of smart levels, with not so perfect wing/tail alignments and uneven elevators.:)

Remember, when you get to the point of having to drill your rear spars to the airplane, it's the one area that you need to be as accurate as possible to not have a rolling tendency built in.

Build on,
 
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