What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

-7 Horizontal Stabilizer Mounting

mfleming

Well Known Member
Patron
Note: -7 quick build fuselage, Synergy Air mentored stabilizer.

Today I trial fitted the horizontal stabilizer to the fuselage and something is very wrong :eek:

I started by drawing a centerline on the aft deck and then marking the F-710C spacer / F-710B angle on the top of the deck for reference.

As soon as I placed the stabilizer in position I could see the forward spar was way to far aft. 29/64" too far. That's over 7/16" of an inch too far aft.

I measured all the bits on the aft deck and they seem to be in all the correct places.

The horizontal stabilizer is more troubling. The forward spar seems to be too far aft. Neither Van's or I can figure out what mistake would end up with a misplaced spar...everything looks good compared to the plans except the spar is too far aft :confused: :confused:

stab.jpg


There must be a mistake somewhere but darned if I can see where it is. We even entertained the idea that the stabilizer is not a -7...not sure how to tell.

Has anyone ever heard of such a thing??
 
Last edited:
Being almost 1/2? out of alignment is a lot. Can you share some pictures and details of the rear spar and of the F-711 bulkhead assembly?
 
Have you fitted or installed the F-710 bulkhead yet?

Yes the F-711 bulkhead is already installed...it's a QB fuse. And I already installed the F-712 bulkhead...it's a -7 so the tail wheel weldment is now in.
 
Excellent application of "measure twice, drill once (or zero)"

I'm interested in what's not happy; mine lined up quite nicely when I drilled the tail (though, I measured about 10,000 times to be sure....). Mine is a slow build.
 
Maybe a stupid question

When you mounted the horizontal stabilizer was the aft spar behind F-711C bars? I could see the forward spar sitting too far forward if the aft spar was in front of the F-711C bars. That flange would account for most of the space.

Check to make sure the F-711C bars are installed on the forward side of the F-712 bulkhead? Not likely to be the problem.

Your line appears to be in the correct location, based on the photo.
 
More photos:

Here's another angle with the stabilizer in position and sitting short of the line.

stab2.jpg


--------------------------------------------------------------------------------------

Looking at the aft deck...All measurements look good here.

stab4.jpg


--------------------------------------------------------------------------------------

F-711 bulkhead from the outside.

stab10.jpg


------------------------------------------------------------------------------------

F-711 bulkhead from the inside...alls good as as I can tell.

stab11.jpg


------------------------------------------------------------------------------------

The rear stabilizer spar.

stab5.jpg
 
When you mounted the horizontal stabilizer was the aft spar behind F-711C bars? I could see the forward spar sitting too far forward if the aft spar was in front of the F-711C bars. That flange would account for most of the space.

Check to make sure the F-711C bars are installed on the forward side of the F-712 bulkhead? Not likely to be the problem.

Your line appears to be in the correct location, based on the photo.

Yes on both accounts.

I'm totally perplexed and am expecting to have a head slapper when the answer arrises :eek:
 
Last edited:
Check that the distance from the front of the HS rear spar to the back of the HS front spar is 12 and 3/16 inch. If it is then your HS is correct. I think check this first, and then double check that you have actually drawn those lines in the correct place. On mine the distance from your front line ( forward part of the angle (F710B) on the F710 bulkhead) to the centre of the first rivet on the aft deck in front of your line is 5/8 inch, measured parallel to the F710B angle.
Hope it all makes sense, and helps
Regards
Arie
 
Last edited:
weird

is it possible the HS was built with RV-7 spars and RV-8 skins/ribs? It looks like you have the RV-7 spar because its wide enough for the 7 fuselage, but the distance between fwd and aft spars does seem like its short based on eyeballing rivets in aft deck to rivets on HS
 
is it possible the HS was built with RV-7 spars and RV-8 skins/ribs? It looks like you have the RV-7 spar because its wide enough for the 7 fuselage, but the distance between fwd and aft spars does seem like its short based on eyeballing rivets in aft deck to rivets on HS

The RV7 and RV8 uses the same ribs and skins, so they are common to both models.
 
Is that bulkhead installed with the flange oriented correctly?
Having it turned backwards could cause that
 
From the rivet locations it looks like the F-710B angle is not in the right place, but from the pictures I can?t tell why or how that?s possible. Does there appear to be anything unusual about the F-710 rib? The pre-punched holes in the aft deck should be in the middle of the flange of F-710B. During assembly that angle is match drilled in place.
 
From the rivet locations it looks like the F-710B angle is not in the right place, but from the pictures I can?t tell why or how that?s possible. Does there appear to be anything unusual about the F-710 rib? The pre-punched holes in the aft deck should be in the middle of the flange of F-710B. During assembly that angle is match drilled in place.

If you look at the plans the rivets on the aft deck is not in the middle of the F710B angle, it is more aft, towards the vertical flange of the F710B angle.
 
Agree with others, it looks close actually and the aft pieces can move slightly. I might make an edge checker with a couple of strips of "scrap" to hit the lower cross bar and upper at the same time - a "U" shape if that visual translates. Then you can see where the fasteners will go. If a second tool is made flat, you could use it for hole location confirmation. It is always good to know where the hole ends up on the backside.
 
Measurements

Everything looks correct and since it is prepunched, one would assume very close to correct.
Don't me offended but is it possible the line drawn on the aft deck is not the center of the angle brace underneath?
Occam's Razor. The simplest solution is usually the correct one.
 
Check that the distance from the front of the HS rear spar to the back of the HS front spar is 12 and 3/16 inch. If it is then your HS is correct. I think check this first, and then double check that you have actually drawn those lines in the correct place. On mine the distance from your front line ( forward part of the angle (F710B) on the F710 bulkhead) to the centre of the first rivet on the aft deck in front of your line is 5/8 inch, measured parallel to the F710B angle.
Hope it all makes sense, and helps
Regards
Arie

I just check...it's exactly 12 3/16" although my plans show 12 9/32".
 
From the rivet locations it looks like the F-710B angle is not in the right place, but from the pictures I can?t tell why or how that?s possible. Does there appear to be anything unusual about the F-710 rib? The pre-punched holes in the aft deck should be in the middle of the flange of F-710B. During assembly that angle is match drilled in place.

Everything looks in OK except those four top rivets look too far aft.

If you look at the plans the rivets on the aft deck is not in the middle of the F710B angle, it is more aft, towards the vertical flange of the F710B angle.

Yes, I agree the rivets seem too far aft. they are almost against the radius of the F-710B angle, you can see that on the interior photo of the F-710 bulkhead posted earlier...but there doesn't seem to be anything out of place on the F-710 bulkhead.

Everything looks correct and since it is prepunched, one would assume very close to correct.
Don't me offended but is it possible the line drawn on the aft deck is not the center of the angle brace underneath?
Occam's Razor. The simplest solution is usually the correct one.

No offense taken :) I was sure that it must be a error on my part when I first discovered this but I'm really baffled now.

Here's the way I determined the location of the F-710B angle.

stab12.jpg


stab13.jpg


All this is positioned by fixed predrilled parts. there must be some non -7 parts in the mix is all I can think of :eek:
 
Michael, what is your distance from the vertical bars on the F711 to the front of the F710B angle. It should be 13 1/32inch, i am not saying mine are correct, but the front of my HS line up perfectly with the F710B.
Regards.
Arie
 
Last edited:
710B and 710C

Tough to tell because of the angle of view, but it appears to me that the 710B and C are not positioned far enough aft. Perhaps the F-710 bulkhead is bowed forward?

Also, my plans show the distance from the forward edge of the HS rear spar to the aft edge of the HS-710 and HS-714 spice angles to be 12 3/16" - so you are right on with this measurement.

Best regards,

Merrill
 
Angle dimension

Is the angle the correct dimension material?
It looks right but if they made it from the wrong stuff, the flange may be too narrow.
Just a thought.
 
Is the angle the correct dimension material?
It looks right but if they made it from the wrong stuff, the flange may be too narrow.
Just a thought.

My thoughts exactly...but I measured the F-710B angle and it's the proper 1" X 1".
 
I just got off the phone with Van's and They are perplexed why the F-710B angle is too far aft. Everyones curiosity is up at Van's, they are pulling a -7 fuse down to take a closer look and will get back to me.

They also had me set up the stabilizer with better clamps and add the 3/16" spacers under the rear spar. This has brought the distance down to about ?" too far aft.

Although Van's doesn't know why (yet) everything is off, they said there's a couple fixes. Depending on if I can get an acceptable edge distance on both the F-710B angle and the HS-714 angles, I can split the difference and proceed to drill the stab in place. Otherwise if I can't get the edge distance they want me to drill off the deck and move the F-710B angle around to get things to line up.

Being that this is a QB fuse, I'm not keen on doing that and risking screwing up those AN4 rivets on my dime.
 
Horizontal stabilizer mounting

You are more than welcome to give me a call to discuss this issue if you have not figured it out yet. I'm sure we can work through it together.

Ryan A. Marshall
Synergy Air
541-844-6120
 
Synergy Air Rocks

Ryan Marshall from Synergy Air is the man!

After Ryan suggested I give him a call, I did and he figured out what was wrong in pretty quick order.

So the forward spar of the horizontal stabilizer is biased rearward by a little less the ⅛". This of course doesn't help my problem.

But the big issue was that the F-711C vertical bars were not square to the aft deck. In fact they were leaning aft by a hefty amount. Ryan said he always takes great care when installing the bars to get them perpendicular to the deck before riveting.

Well after a little tweaking, my F-11C bars are now square and the error is down to less than 3/16". I can make that work.

Wow :p what a head scratcher. Tomorrow the horizontal stabilizer goes on :D
 
Just a question, how did you tweak the F711C bars to be perpendicular to the aft deck?
 
Just a question, how did you tweak the F711C bars to be perpendicular to the aft deck?

Using a 24" crescent wrench with padded jaws. Slid the jaws down the F-711C vertical bars until near the deck. Using another wrench on the 24" wrench, I carefully straightened the F-711Cs.
 
Back
Top