I am attempting to mount the vertical stab to the horizontal and the rear F712 and I can't seem to find where there is an actual measurement to go by on the front spar. I realize that there is a 1/4" joggle in the F718 and it must be ablsolutely vertical to the horizontal stab. but the height of the vertical is what I can't seem to find. I did use the print to locate the rear vertical stab spar on the F712 but that seems to lower the front almost too much when the rudder hinges are straight. Does anyone have a dimension or advice. Thanks.
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Vertical Stab Position
- Thread starter rcarson
- Start date
f1rocket
Well Known Member
It's critical that your vertical stabilizer is:
Whatever you do, I think it's critical that your hinges are aligned with one another. Otherwise, you'll have some binding in the rudder. Again I wouldn't get over critical here since the rudder is used so little on these airplanes.
Actually, the thing that drives most of us crazy is aligning the vertical stab with the centerline of the airframe and figuring out what offset (if any) is needed to get the ball centered in cruise. I move my vertical three times before I got it to fly without any residual rudder input. Most just stick a wedge on the rudder as a trim tab.
Don't be in a hurry to drill and mount the empennage until later in the process.
- horizontally aligned so that the ball is centered during normal flight
- perpendicular to the horizontal plane of the airframe
- Rudder hinges are aligned
Whatever you do, I think it's critical that your hinges are aligned with one another. Otherwise, you'll have some binding in the rudder. Again I wouldn't get over critical here since the rudder is used so little on these airplanes.
Actually, the thing that drives most of us crazy is aligning the vertical stab with the centerline of the airframe and figuring out what offset (if any) is needed to get the ball centered in cruise. I move my vertical three times before I got it to fly without any residual rudder input. Most just stick a wedge on the rudder as a trim tab.
Don't be in a hurry to drill and mount the empennage until later in the process.
Walt
Well Known Member
I installed both vert and horiz in the garage without the wings on, just make sure the fuselage is leveled in both directions, install the horiz and then the vert. The height of the front is establised by the certerline of the rudder hinges. I dropped a string with a plumb bob throught the attach holes, lined them up "perfectly" then drilled the front attach.
Maybe I was lucky but I ended up with a perfectly faired elev trim tab and no rudder trim wedge
Maybe I was lucky but I ended up with a perfectly faired elev trim tab and no rudder trim wedge
rzbill
Well Known Member
??
I don't understand the need to involve the wings in the empenage connection to the fuselage. I have attached mine following the plans and instructions.
1) H-Stab squared with firewall and level set with the spacers off the longerons per instructions. Stab will be level to wings unless the whole fuselage is twisted which (for mine) is not the case as shown by previous leveling of fuselage. I can't see how this could get off very far via the -7 construction techniques.
2) V-Stab rear spar set vertical off of H-Stab tips per instructions. Rear spar height is set per dimension on print. Front stab vertical position set by straight hinge line position per instructions. This is hard to do if you have not trimmed the front spar first per instructions. Instructions give three options for longitudinal position of front spar in relation to the jogged joining plate in order to get the hinge line straight.
3) I did fiddle with the lateral position of the V-Stab front spar before nailing it down. The instruction manual specifically says "1/4 inch offset of leading edge". It is not clear to me whether the intent was 1/4" at the front spar (due to the measured joggle amount in the plate) or instruction verbatem at the leading edge. I chose to measure and set the leading edge position. When I fly, I will find out. Maybe that plate will be replaced a couple of times as noted by F1Rocket.
I don't understand the need to involve the wings in the empenage connection to the fuselage. I have attached mine following the plans and instructions.
1) H-Stab squared with firewall and level set with the spacers off the longerons per instructions. Stab will be level to wings unless the whole fuselage is twisted which (for mine) is not the case as shown by previous leveling of fuselage. I can't see how this could get off very far via the -7 construction techniques.
2) V-Stab rear spar set vertical off of H-Stab tips per instructions. Rear spar height is set per dimension on print. Front stab vertical position set by straight hinge line position per instructions. This is hard to do if you have not trimmed the front spar first per instructions. Instructions give three options for longitudinal position of front spar in relation to the jogged joining plate in order to get the hinge line straight.
3) I did fiddle with the lateral position of the V-Stab front spar before nailing it down. The instruction manual specifically says "1/4 inch offset of leading edge". It is not clear to me whether the intent was 1/4" at the front spar (due to the measured joggle amount in the plate) or instruction verbatem at the leading edge. I chose to measure and set the leading edge position. When I fly, I will find out. Maybe that plate will be replaced a couple of times as noted by F1Rocket.
f1rocket
Well Known Member
My suggestions are based upon experience and are not absolute. Do what works for you. The only true horizontal level is determined by the wings. You can level to the firewall and fuselage stringers all day, but the wings are going to fly the way they fly.
Now, maybe my experience is based more on the construction of the older kits and doesn't apply to the pre-punch or quickbuild kits. I've always found some twist even in these kits and most RVs have some level of mis-rigging present. It all depends on how accurate you want to get it.
Now, maybe my experience is based more on the construction of the older kits and doesn't apply to the pre-punch or quickbuild kits. I've always found some twist even in these kits and most RVs have some level of mis-rigging present. It all depends on how accurate you want to get it.
Thanks for the info. It seems like I'm doing everything right but I would like to have a dimension to go by on the front spar as reference. To get the hinges perfect I had to raise the aft spar almost 1/4" which seems like a lot and the longerons not being visible from the rear makes it difficult to be sure you are in the right place. I did cut off the 5/8 on the front spar and shimmed it several ways but didn't make much difference. Could be I want it too close. In the position I now have it I am 1/16" off on the middle hinge. Not much but not right. Let me know if you can think of anything else. Thanks again.
