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  #1  
Old 04-16-2015, 11:12 AM
AndyWW AndyWW is offline
 
Join Date: Jan 2015
Location: Englefield Green UK
Posts: 73
Default Edge Distance on HS Front Spar Doubler - RV-7

A month ago, I hit a snag on the front spar of the HS of my new-build 7, where the edge distance on the holes I drilled in the doubler HS-00001 from HS-710 was very marginal and the spar wasn't straight enough for my liking (see related thread http://www.vansairforce.com/communit...d.php?t=124011). After a long holiday, my re-ordered parts arrived 3 days ago and I've got to the stage where things went wrong last time (about to match-drill HS-00001 and HS-702). The instructions are a little unclear and look to me like they were probably modified rather than being completely re-written after the doubler was introduced last year to fix the cracking AD. I was about to dive in and try again, but then my wife suggested I post here to ask if anyone has any great suggestions or insights.

The basic issue is that when fixing the position of the doubler it is very hard to see in advance what the edge distance is going to be when the holes outboard of the bend lines are drilled into the "ears", and there is very little room for error. Tiny changes in orientation or positioning can make the edge distance insufficient, and there is inevitably some variation due to the extent to which edges have been smoothed etc. It is tempting to make the bends in HS-710 and HS-714 prior to match-drilling in order to have a better idea of the positioning, but even if I did this it would still be difficult to determine the edge distance before it was too late since the front spar HS-702 is between the 710 and the doubler.

The other, and perhaps related issue, is that the 2 clecos that hold the 710 or 714 to the spar are both close to its center, and they actually allow a fair bit of movement at the end of the spar. So I think that it might be possible to improve upon the suggested procedure of just setting the clecos and match-drilling. I'm certainly going to incorporate a measurement of spar straightness this time!

Any thoughts much appreciated. Part of the problem here is perhaps that this section of the instructions is new so there isn't much accumulated wisdom available yet.
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  #2  
Old 04-16-2015, 11:53 AM
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Raymo Raymo is offline
 
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Location: Richmond Hill, GA (KLHW)
Posts: 2,189
Default

Here is a great video of the installation on a -7.

When we did mine (with assistance from experienced builder), we marked where the center line would ideally be for the rivet row on the doubler. This allowed a visual from the other side of the spar to get as close to the equal on top and bottom rows of rivets.

http://www.bing.com/videos/search?q=...AD9986C477C491
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  #3  
Old 04-16-2015, 02:21 PM
RobinHou RobinHou is offline
 
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Location: Pasadena, California
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Great video; thanks for sharing.
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  #4  
Old 04-16-2015, 07:04 PM
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bddalm bddalm is offline
 
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Location: Peachtree City, Georgia
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Thanks for sharing, Raymond. AndyWW, hope the video is helpful. Try clamping the doublers in place then marking the existing holes on the doubler. Feel free to contact me through my website if you have any other questions.
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  #5  
Old 04-16-2015, 11:21 PM
tal454 tal454 is offline
 
Join Date: Feb 2015
Location: Sacramento, CA
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Are you referring to the holes being drilled WITH the ribs?

I just finished prep on all the HS parts and am ready to rivet them all together.

The only thing I can remember being slightly close to edge distance was the 4 holes that you drill after everything is assembled with the ribs. Sec D-D shows 7/16" from the top to the hole and the bottom 1/2". For these holes if you look closely at View A-A the top hole gets pretty close to min edge distance on the HS-710. Vans informed me its okay to get a little over edge distance on the ribs and other parts in this area but the 710 is structural so be sure not to get it too close. I just measured the measurements out that were on the plans and drilled slightly smaller distance than the 7/16" called for. All worked out well.

Hopefully thats helpful.
-Tim
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  #6  
Old 04-17-2015, 02:27 AM
AndyWW AndyWW is offline
 
Join Date: Jan 2015
Location: Englefield Green UK
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Thanks for the answers, especially the video - for those that haven't seen it already, it's well worth watching. It doesn't correspond exactly to my situation since to be totally clear, I'm talking about the initial step in the fresh construction of the HS front spar, using the new instructions which incorporate the doubler from the beginning. This is well before the holes for the ribs are drilled.

The problem I have is that if I go ahead with all new parts, there's only one hole in the spar to look through at the rivet lines on the doublers. The best thing I can think of so far is to use a rather elaborate measuring procedure to try to infer where the holes will come out for a given position of the doubler.

I could try a combination of new and old parts (I reordered HS-702, 710, 714 and 00001) but I haven't managed to think of a combination which wouldn't risk perpetuating at least some of the misalignment I had last time.

Does anyone know of any reason why I shouldn't taper and bend the 710 and 714 before drilling them to HS-702? That would make it easier to estimate where the holes outboard of the bend line are going to end up. Another way might be to use the old 710 and 714 to figure this out.

I'm curious how other people have done this step - there must be a few people by now who have created a new HS since the doubler was added?
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  #7  
Old 04-17-2015, 05:17 AM
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Z-EDD Z-EDD is offline
 
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Hi Andy

I have been racking my brains to remember this step, and it doesn't help at all that the instructions seem to make no more sense than they did a year ago, they really are appalling! But then I found this photo of the two angles drilled to the HS-702 channels, but without the 00001 doubler in place, and I think that may be the answer! The instructions start by telling you to cleco the 710 and 714 angles to the 702 channels. The very next step tells you to trim the spar channels, apparently with the angles still in place, a seemingly useless step! I think Vans have omitted to mention that while the angles are clecoed to the channels they should be match drilled (only inboard of the ribs mind you). This will then allow you to see the lines they tell you to draw on HS-00001 later on. Its difficult only having these pictures and a fading memory. With the raw parts in front of you does this make sense? or did you do this anyway and still have a problem?

One other thing I'd like to mention is that minimum edge distances are not always absolute and exemptions are common. As Tim mentioned above, I also had less than minimum edge distance on the rib flange but vans Ok'd it. Before the SB most guys got the edge distance issue on the nose rib flange, and it was usually ok. Given that the HS-00001 is a honking thick piece of metal with more than two dozen rivets through it, and was not even considered necessary in the original design, it is a classic candidate for an edge distance exemption, but only Vans can grant that.
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Last edited by Z-EDD : 04-17-2015 at 10:03 AM.
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  #8  
Old 04-17-2015, 02:32 PM
AndyWW AndyWW is offline
 
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Location: Englefield Green UK
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Hi Ed - Thanks very much for the very useful photos and insightful reply. I found what you said about the instructions quite intriguing - I'd also noticed that there seemed to be an odd cleco/un-cleco foxtrot going on, and I think your theory makes a lot of sense. I tried to follow the instructions even though they seemed strange, and it didn't end well. I am very tempted to try your method. Ultimately I think the most important issue is to get a straight spar and this seems like a good way to get it.

So the proposal is to insert an extra step in the instructions as follows:
1) Ignore the doubler to begin with and drill the holes inboard of the bend line from the 710 and 714 though the spar, making sure it is straight before drilling.
2) Use the newly drilled holes to make sure the doubler is positioned correctly, by sighting the previously drawn rivet lines through the holes.
3) This should solve (or at least mitigate) the edge distance problem on the doubler ears.

As you point out this is a perfect place to use the tolerance allowed on edge distance, and measuring the distance between the edges of the ears on the doublers, compared with the distance between the lines of holes on 710 and 714 suggests that some tolerance is guaranteed to be required. I just want to make sure it isn't asymmetric (on my first attempt the right side was ok but the left wasn't).

Can anyone think of any reason this isn't a big improvement on the current instructions?
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  #9  
Old 04-17-2015, 04:18 PM
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wirejock wirejock is offline
 
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Location: Estes Park, CO
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Default HS instructions

Andy
I built mine twice. The second time was to correct an egg shaped hole from the SB.
On the second pass with all new insides, I tried to document the process because the manual was difficult.
Check my blog, "empennage" page. Scroll to the bottom.
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  #10  
Old 04-19-2015, 03:06 PM
AndyWW AndyWW is offline
 
Join Date: Jan 2015
Location: Englefield Green UK
Posts: 73
Default Success!

Thanks to everyone for their tips. I drilled yesterday using Ed's suggestion and it seems to have turned out well. The key was to keep checking the mid-points of the spar ends against the long center line during the drilling process, since these can move around quite a bit when things are only clecoed near the center. The only issue I had was one hole in each spar that got slightly enlarged (0.137") due to being match drilled twice (once with HS-714 and once with the HS-00001 doubler). I can't check the edge distance on the doubler ears until they are drilled later on, but it looks very promising and much better than last time.
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