Tip: Instructions Error page 8.2

[FlyingArcher]

Thought this might help other 9/9A and 7/7A builders. My friend Bernard, who is now flying his -9A, warned me that when assembling the F-705 bulkhead it would be wise to trim the edges as required later because it's much easier now.

Well, in fact, the instructions try to tell you to do so, but point you to the wrong page

Trim the ends of the F-605B Center Section Bar as shown on the upper right of DWG 20

If you look where indicated, you'll see nothing related to this action. However, if you do so on DWG 38, you'll then see what the text tried to explain.
Hope this helps.

 

[mikehoover]

DO NOT TRIM!

If you are referring to DWG 38, SECTION G-G where the hatched area of the outboard ends of the F-705B Center Section Bar and F-605C Bar Doubler, I would highly recommend you DO NOT TRIM this until you fit your wings and find you actually need to trim them. Notice that there is no dimension or advice on how much to trim except the note "to eliminate interference with nose of flap assembly." So how much do you trim? And how will you know there is interference until you fit the wings and install the flaps? The critical point here is you run a risk of ending up with less than the required 5/8" edge distance for the bolt hole mentioned in Note 1 of that drawing - and THIS IS CRITICAL. I know of two folks so far who have had to removed the F-705 Center Section Bar and F-605C Bar Doublers and replace them because of the lack of edge distance. Fortunately, I was not one of them, but I have exactly 5/8" by pure luck on one of the bars because I trimmed before I fitted the wings. I found that I did not need to trim them at all. Hope this will save someone some grief.

 

[FlyingArcher]

Took advice from Vans

Here are Vans answers to my questions related to this topic:

Q1 - Am I right thinking the manual should point to DWG 38?

Yes

Q2 - Is it safe to trim these bars right now?

Yes, but keep it to a minimum to align the end of the bar with the angle of the wing rib.Remove nothing from the lower outboard corner.

And to answer one of Mike's remarks

Notice that there is no dimension or advice on how much to trim except the note "to eliminate interference with nose of flap assembly." So how much do you trim?

The drawing shows an angle, not a measurement, you're right. I simply used a protractor to transfer the angle made by the wing main spar with the F-904 center section. Based on some old geometry memories, I think this will make the F-705B edge parallel to the wing inboard rib. And of course I didn't touch the lower outboard corner as advised by Vans.

With that said, I'm not at the end of my build, so if this is a big mistake I'll only know later, but I suppose Vans would have really warned me if that's the case.
YMMV and builders can make an informed choice by now,