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  #21  
Old 05-07-2020, 12:53 PM
WingsOnWheels WingsOnWheels is offline
 
Join Date: Mar 2009
Location: Plano, TX
Posts: 2,128
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Quote:
Originally Posted by az_gila View Post
Yes, but if the sides are already drilled the other option available is to "adjust" the width of the bulkheads to fit with the longerons set straight with a string.
I was referring to his comment about the bulge in the side being and intentional part of the design. There are many little errors like this in the plans (or parts) that require some extra caution before poking holes.
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RV-6A #20603
Complete 5/10/19
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I donate every year on my B-Day (in Dec), but donated early in Sep'19.
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  #22  
Old 05-07-2020, 05:08 PM
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PaulvS PaulvS is offline
 
Join Date: Aug 2019
Location: Western Australia
Posts: 558
Default Bulkhead adjusted

So far I have adjusted the width of the baggage compartment bulkhead by removing the rivets that hold together the three piece bulkhead (F-606) and moved each side out by about 1/8". This has reduced the amount of bow out as checked with a long straight edge. The skins are not yet back on but the TC (who is a very experienced RV builder) had a look at it and thinks it should be OK now.

If I had tried to adjust the position of the other bulkheads to get the sides flat (before drilling holes in everything) I think it would have thrown out the straight line along the keel and the top deck. These lines are both dead straight right now on both the tops and the bottoms of the bulkheads. This is with the installed bulkhead locations and widths exactly as per the plans, including the revision on Dwg 24 that widened F-607 and F-608 by 0.25 (this change isn't immediately obvious on the drawing as the dimensions are unchanged, but the reference line was moved back by 0.125).

I did some simple maths on the slope of the sides by calculating rise/run for each bulkhead bay and it is not constant, so the sides are designed to be not flat, unless there are errors in the drawing that have never been corrected. Anyway I just have to work with the parts I have got, hopefully when I get the skins back on today there will be an acceptable fit.

Thanks again for the assistance, I'm glad there are still people around who know about the older models.
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Building RV-6A #22320 O-320 FP. Wings and tail complete, working on fuselage
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Last edited by PaulvS : 05-07-2020 at 06:09 PM. Reason: clarification
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  #23  
Old 05-08-2020, 08:44 AM
Coaltowngarage Coaltowngarage is offline
 
Join Date: Aug 2019
Location: Altoona,AL
Posts: 49
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Glad you are making progress. I definitely think there are some discrepancies in the plans and/or some of the parts that you just sort of have to field modify. With mine, I think it was bulkhead 11(2nd from last) was too narrow, causing an inward bow in that area, it couldn't be moved fore or aft because the distance was locked in by the tailwheel mount. The half bulkhead ahead of those I did have to move to prevent inward bow, and had to cut and lengthen bulkhead 8 to get the belly j stringers to make a straight line.
Its new to you and I, but its good knowing that there are many others who have gone before. Its speaking with some of them and helpful comments on VAF that really sets your mind at ease.
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  #24  
Old 05-12-2020, 08:54 PM
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PaulvS PaulvS is offline
 
Join Date: Aug 2019
Location: Western Australia
Posts: 558
Default Update

Good news; after widening bulkhead F-606 by 0.125 per side the aft skins fit properly and the rolled section that was causing a problem now sits flat over the belly skin and doesn't ripple up any more. It is surprising that such a small adjustment to one bulkhead has made such a bit difference.

For future reference here are some other gotchas that I encountered with the fuselage frame to date:
  1. The aft side skins F-673 came rolled but the roll was not enough at the rear, so I curved it further by clamping and holding the edge between timber boards and then curled them over, it took quite a bit of force to adjust - and not crease.
  2. Bulkhead F-606 needed to be tilted back by about 1/2 inch at the top so as to align with the elevator bell crank support F-628.
  3. F-604E is supposed to have the web bent and not cut all the way through. The flanges need to be cut. These details are not on Dwg 31.
  4. The J-stiffeners along the edge of F-673 needed to be re-positioned after fitting the skins so as to get adequate edge clearance for the rivets.
  5. The attach bars on F-611T are right up against the bulkhead flanges and there is not much space to drill and dimple for the skin rivets.
  6. It worked very well to drill the fuselage skins using small pilot holes drilled from the inside out. Initially I drilled 1/16 holes (all of them) in the bulkhead flanges and also 1/16 holes in the J-stiffeners at the intersections with the bulkheads. Then clamped on the skins and crawled under the fuselage frame to drill 1/16 holes from the inside out using 12" bit. Then crawled out and drilled #40 through the skin using the 1/16" hole, and cleco'd. There was a lot of crawling back and forth to do these one-by-one but it was worthwhile to avoid drilling into a void or a flute or too close to an edge.
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Paul vS (yes I'm also a Van)
Building RV-6A #22320 O-320 FP. Wings and tail complete, working on fuselage
Flying my Aeroprakt A-22 STOL and the aero club's RV-9A while I build

Last edited by PaulvS : 05-12-2020 at 09:17 PM.
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