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06-08-2012, 12:14 PM
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Join Date: Nov 2005
Location: Snohomish, Washington
Posts: 699
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Quote:
Originally Posted by cln1owner
Gil brings up and important point. The part is prebent from vans, however, and this was discussed in this thread, The bracket should sit behind the VS forward spar, not in front as depicted in this picture and the crack photo in question. If the bracket was attached on the front side of the forward spar, and the spar length after trimming was too long... the bracket would be under stress when bolted flat against the HS spar.
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Nate is correct here. I tried my bracket in front and behind the spar during assembly. When it was in front the upper bolts had to pull the bracket into the horizontal spar to close the gap. With the bracket in the rear per the plans it lays flat and tight against the spar. I could easily see this being the cause of the cracks forming on the top two bolts due to the bending load placed on the bracket through the bolt holes when installed in front of the VS spar.
__________________
Don Jones
Technical Support Manager
Dynon Avionics
CFI-IA, AGI, IGI
RV9-A
Last edited by Don Jones : 06-08-2012 at 12:16 PM.
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06-08-2012, 02:07 PM
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Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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Quote:
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Originally Posted by The bracket should sit [COLOR="Red"
behind[/color] the VS forward spar, not in front as depicted in this picture and the crack photo in question. If the bracket was attached on the front side of the forward spar, and the spar length after trimming was too long... the bracket would be under stress when bolted flat against the HS spar.
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Gil's instincts told him something was up and a good catch by Nate on what that something was. If I was a betting man, I would double down on this being the likely cause as Don also suggests.
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.
RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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06-08-2012, 03:01 PM
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Join Date: May 2005
Location: Canby, Oregon
Posts: 1,786
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Wait a minute....
Quote:
Originally Posted by Don Jones
Nate is correct here. I tried my bracket in front and behind the spar during assembly. When it was in front the upper bolts had to pull the bracket into the horizontal spar to close the gap. With the bracket in the rear per the plans it lays flat and tight against the spar. I could easily see this being the cause of the cracks forming on the top two bolts due to the bending load placed on the bracket through the bolt holes when installed in front of the VS spar.
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From the instruction on "Fitting The Vertical Stabilizer" page 8-17.
"If the read spar bends aft at the top when the front spar is clamped, the vertical spar may be mounted on the rear of the F-981 plate. If necessary, you can make a shim to put between the F-981 and the vertical stabilizer spar. If the rear spar bends forward, make a shim to go between the F-981 and the front spar of the vertical stabilizer."
Look like mount on the front or back depends on how your parts look after construction.
Kent
__________________
Kent Byerley
RV9A N94KJ - IO320, CS, tipup
AFS 3500, TT AP, FLYING....
Canby, Or
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06-08-2012, 03:02 PM
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Join Date: Jun 2009
Location: Arroyo Grande, CA
Posts: 227
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RV-6/6A instructions dated 9/10/01:
"Once the VS-603 rear spar has been drilled and bolted, the forward spar of the vertical stab, VS-402, must be aligned with and joined to the front spar of the horizontal stab, HS-602 with the joint plate F-681. At this point the tiny variations between individual aircraft become apparent and the fore/aft match of the spars is seldom perfect. If necessary, F-681 can be attached to the front of VS-402. If this does not solve the problem, use a piece of aluminum sheet, up to 1/8" thickness between the F-681 joint plate and either spar. Of course, longer fasteners must be used as well. If this does [sic] is still not sufficient, a new F-681 may be fabricated with the bend in a different location. Do not leave less than 2" above the bend. The portion below the bend must be sufficient to bolt to both HS-610 and HS-614. The combination of these adjustments should accomodate any reasonable mis-match."
I would have hoped that builders of the RV7/7A wouldn't have faced this type of "mis-match" problem. It is interesting that these instructions seem to indicate that Van does not take the whole "joint plate" very seriously.
__________________
Bob Marshall
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06-08-2012, 03:44 PM
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Join Date: Jan 2006
Location: Ehprata, WA
Posts: 318
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Quote:
Originally Posted by kentb
From the instruction on "Fitting The Vertical Stabilizer" page 8-17.
"If the read spar bends aft at the top when the front spar is clamped, the vertical spar may be mounted on the rear of the F-981 plate. If necessary, you can make a shim to put between the F-981 and the vertical stabilizer spar. If the rear spar bends forward, make a shim to go between the F-981 and the front spar of the vertical stabilizer."
Look like mount on the front or back depends on how your parts look after construction.
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Looks as though, either way, care must be taken so that the F-981 does not flex forward or backward when clamped in place.
__________________
Nate Benson
Ephrata, WA
RV9A/Slider N608MA
Flying
KitProject.com
"If you think you can do a thing, or think you can't do a thing, you're right." -- Henry Ford
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06-08-2012, 04:59 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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Not quite the same
Quote:
Originally Posted by Bob'sRV6A
"Once the VS-603 rear spar has been drilled and bolted, the forward spar of the vertical stab, VS-402, must be aligned with and joined to the front spar of the horizontal stab, HS-602 with the joint plate F-681. At this point the tiny variations between individual aircraft become apparent and the fore/aft match of the spars is seldom perfect. If necessary, F-681 can be attached to the front of VS-402. If this does not solve the problem, use a piece of aluminum sheet, up to 1/8" thickness between the F-681 joint plate and either spar. Of course, longer fasteners must be used as well. If this does [sic] is still not sufficient, a new F-681 may be fabricated with the bend in a different location. Do not leave less than 2" above the bend. The portion below the bend must be sufficient to bolt to both HS-610 and HS-614. The combination of these adjustments should accomodate any reasonable mis-match."
I would have hoped that builders of the RV7/7A wouldn't have faced this type of "mis-match" problem. It is interesting that these instructions seem to indicate that Van does not take the whole "joint plate" very seriously.
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The RV-6x assembly is a lot less critical since the part the connects the VS and HS spars does not have a tab on the bottom that is bolted to the deck.
This enables the bent part to be moved up and down somewhat to get alignment. I believe this was never a prepunched part on the -6s.
The RV-9 arrangement is much more critical for alignment due to the lower bolted tab. I guess vans slots were an attempt toease this problem a bit.
__________________
Gil Alexander
EAA Technical Counselor, Airframe Mechanic
Half completed RV-10 QB purchased
RV-6A N61GX - finally flying
Grumman Tiger N12GA - flying
La Cholla Airpark (57AZ) Tucson AZ
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06-08-2012, 05:12 PM
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Join Date: Jun 2009
Location: Arroyo Grande, CA
Posts: 227
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[quote=az_gila;667313]The RV-6x assembly is a lot less critical since the part the connects the VS and HS spars does not have a tab on the bottom that is bolted to the deck.
This enables the bent part to be moved up and down somewhat to get alignment. I believe this was never a prepunched part on the -6s.
QUOTE]
Thanks Gil, I will be doing the install in a few months and obviously didn't understand the diferences in the models.
__________________
Bob Marshall
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06-08-2012, 06:54 PM
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Join Date: Jul 2005
Location: Hubbard Oregon
Posts: 9,035
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Quote:
Originally Posted by bruceh
The elongated holes come that way from Van's.
Here's what mine looked like during the fitting to the fuselage.
I'm not sure why Van's does the elongation of the holes to this part, since you have to drill the forward spar in the VS to set the position and angle of the VS rear spar to be straight up and down. Makes me wonder if there should be washers under the bolt heads on the enlongated holes to provide better clamping pressure on the bracket.
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I have never seen cracks in this location before.
The reason for the elongated holes is to allow for an adjustment of stab incidence should anyone ever want to do so.
I thought that washers were specified under the bolt heads (anyone have plans handy?)
Looking closely at the crack photo, it looks to me like there is an imprint where a washer was installed previously (but maybe my imagination)
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06-08-2012, 07:43 PM
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Join Date: Dec 2010
Location: WASh, DC
Posts: 26
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Vertical Stab Attach Plate Crack
I talked to Van's again today and they say the washer with the bolt should be fine.
Also, I noticed when you look at the drawing you cannot see a washer with the bolt however, in the text of the drawing it specifically says to install a washer.
Today, I received a new F-981 in the mail. After etching priming, painting the part, takeoff the tail this weekend I can hopefully finish it next weekend. New job requires me to work out of town for the week.
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06-08-2012, 08:01 PM
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Join Date: Jan 2007
Location: Battleground
Posts: 4,348
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Great catch. I am sure all will be checking thier stabs for missing washers and cracks. Two other owners and nine or ten cI's and nobody saw this. Way to go.
__________________
Smart People do Stupid things all the time. I know, I've seen me do'em.
RV6 - Builder/Flying
Bucker Jungmann
Fiat G.46 -(restoration in progress, if I have enough life left in me)
RV1 - Proud Pilot.
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