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04-30-2014, 10:26 AM
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Join Date: Jan 2012
Location: up up and away
Posts: 312
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A spliced former - is this common in an RV-4?
It looks like the former is split and spliced back together. Is this a common thing that builders do to this airframe?

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04-30-2014, 10:56 AM
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Join Date: Dec 2004
Location: Gold Hill, NC25
Posts: 2,400
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No this is not common on the 4.
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Kahuna
6A, S8 ,
Gold Hill, NC25
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04-30-2014, 11:02 AM
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Join Date: Jun 2006
Location: Freericksburg, VA
Posts: 624
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Haven't seen that but what is fairly common is to see the top flange cut off the fuselage formers and a new and repositioned on riveted in its place. The fit between the fuselage formers and the top skin not being all that great in the early kits (and as far as I know the latest ones, either). The build manual actually called out that solution to the problem and had nice sketches drawn by Van hisself documenting the procedure.
That may have been what is going on here. The top of the former didn't align well with the top skin and the solution chosen was to split the former and move the top up and to splice the resulting joints.
The formers are basically just there to hold the skin in shape (well they do a bit more than that but for structural load calculations I'd assume they were ignored. The skin is sized to carry the shear and the longerons sized and spaced to carry the bending moments of the tail, IMHO. That is another way of saying that I don't think the modification in question is all that big a deal. Only question might be the number and spacing of rivets used to make the splice. You would want the strength of the combined rivets to be equal to the former metal strength in shear in both directions, etc.
A call to Van's might make one sleep better at night?.
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Richard Bibb
RV-4 N144KT
Fredericksburg, VA
KEZF
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04-30-2014, 11:32 AM
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Join Date: Aug 2012
Location: Lufkin Tx
Posts: 689
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Those of us that have done the fastback conversion have all the rear formers spliced. If it was a problem then it would have surfaced by now.
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Arlie Conner (A&P)
RV-4 (N124TT) Sold
RV-8 (N269CP) Sold
RV-4 (N684ML) completed 3-17-19
KOCH Nacogdoches
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04-30-2014, 11:45 AM
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Join Date: Jan 2012
Location: up up and away
Posts: 312
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Quote:
Originally Posted by acam37
Those of us that have done the fastback conversion have all the rear formers spliced. If it was a problem then it would have surfaced by now.
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Is it a similar splice, just using a flat plate? Do you have a picture you could share?
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04-30-2014, 11:50 AM
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VAF Moderator / Line Boy
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Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,256
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Common the RV-3....
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Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD - "Valkyrie"
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)
http://Ironflight.com
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04-30-2014, 12:05 PM
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been here awhile
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Join Date: Dec 2004
Location: North Alabama
Posts: 4,301
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Similar situation is required on many RV-6's. Here is how I spliced a bulkhead on N399SB fifteen years ago:

Last edited by Sam Buchanan : 04-30-2014 at 12:08 PM.
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04-30-2014, 12:17 PM
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Join Date: Jan 2005
Location: 57AZ - NW Tucson area
Posts: 10,011
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I bet it is common.
The formers were not sized well, so if the height was made to fit, the width would probably be wrong.
One fix was to reposition the formers fore and aft a bit to get the height correct, and then to adjust the overlap of the left and right halves of the formers to fit the width. However, if you followed the plans and riveted the halves together first, then the height needed to be fixed by a splice as shown.
There were several lists of variations of revised spacing of the formers floating around for the -4 and -6 fuselages to compensate. 
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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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04-30-2014, 01:37 PM
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Join Date: Feb 2007
Location: colorado
Posts: 873
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common
I haven't looked at a lot of -4s but I am sure it is common. Not sure I like how it was done but as previously mentioned, it is called out in the manual.
Mine has at least one bulkhead former spit and re joined at the top.
Chris M
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RV-4 "Mr. Twister"
Pitts S1S "Mexican Red" sold and missed
Mr. Twister Airshows
Rocky Mountain Renegades
the mission... have fun.
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04-30-2014, 01:57 PM
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Join Date: Jan 2005
Location: NC25
Posts: 3,508
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Quote:
Originally Posted by Sam Buchanan
Similar situation is required on many RV-6's. Here is how I spliced a bulkhead on N399SB fifteen years ago:

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Yes it is common in the 3, 4, and 6 airframe. The bulkheads would be cut and spliced to make the tail cone look nice, straight, and smooth. That was a faster way than moving the bulkhead forward and aft to get the same end results.
I did my -6 similar to the above more than 18-years ago.
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Gary A. Sobek
NC25 RV-6 Flying
3,400+ hours
Where is N157GS
Building RV-8 S/N: 80012
To most people, the sky is the limit.
To those who love aviation, the sky is home.
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