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  #1  
Old 08-18-2021, 04:32 AM
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PaulvS PaulvS is offline
 
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Location: Western Australia
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Default A better way to enlarge main spar bolt holes for RV-6A gear leg mounts

This is for RV-6A builders who have yet to drill the steel weldment gear leg mounts in unison with the main wing spar (section 8 page 8-9 in the latest construction manual).

The instructions read "Now the real fun begins. Holes must be drilled through the mounting plates of the gear leg mount, using the pre-drilled holes in the spar as drill guides. If a 3/16" drill were initially used, side loads encountered while drilling could easily cause the holes in the aluminum spar to become oversize. So, drill guide bushings should be used in the spar holes to permit accurate drilling of the holes in the steel mount....Four holes in each of the mounts are to be enlarged to 1/4". These can be drilled at this time. First, drill 3/16" from the rear, forward through the steel plates. Then, from the front side which is more accessible, enlarge the holes to 1/4" diameter".

The problems that I encountered with the latter part of the instructions for enlarging the holes to 1/4" is that: (1) The gear mount tube obstructs access from the front for one of the holes and (2) it is difficult to drill a perpendicular 1/4" hole free-hand through a 3/16" pilot hole. I managed fine with enlarging seven holes, but the 8th is slightly enlongated (see att pic). Vans support says "build on" but I'm not very happy with the result.

If I was to do this enlarging to 1/4" a better way, it would be to drill the holes in the spar using a drill press. Ideally, this would be done before building the wings, but it could also be done before installing the wings in the fuselage. The fuselage bulkhead holes would still need to be enlarged after fitting the wings, but this would be relatively safe and easy as it is only .062 thick.

Please don't make the same mistake that I did.
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Last edited by PaulvS : 08-18-2021 at 04:37 AM.
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  #2  
Old 08-18-2021, 04:49 AM
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RV6_flyer RV6_flyer is offline
 
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You must have a really old RV-6(A) kit. The gear and mount are pre-drilled when you get the mount. Some time in the late 1990's before year 2000, the factory started shipping match drilled mounts and gear legs.
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  #3  
Old 08-18-2021, 05:02 AM
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PaulvS PaulvS is offline
 
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Quote:
Originally Posted by RV6_flyer View Post
You must have a really old RV-6(A) kit. The gear and mount are pre-drilled when you get the mount. Some time in the late 1990's before year 2000, the factory started shipping match drilled mounts and gear legs.
Yep it is a very old kit, mid 90's. The gear leg and mount are not pre-drilled, and the mount and the spar are not match drilled either. It's a good thing that the factory started doing this at some point, unfortunately (for me) it was after I started! There may well be no other kits still out there in this state.
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Last edited by PaulvS : 08-18-2021 at 06:24 AM.
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  #4  
Old 08-18-2021, 03:36 PM
WingsOnWheels WingsOnWheels is offline
 
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Quote:
Originally Posted by RV6_flyer View Post
You must have a really old RV-6(A) kit. The gear and mount are pre-drilled when you get the mount. Some time in the late 1990's before year 2000, the factory started shipping match drilled mounts and gear legs.
The 6A kits don't come with the gear towers predrilled, only the later kits, 7A, 9A etc. My finish kit was circa 2012, gear towers are drilled to the leg, but not to the spar. For the taildraggers, you are correct.

To drill mine I used a series of nested metal tubes as drill bushings, worked very well.
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  #5  
Old 08-18-2021, 04:27 PM
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PaulvS PaulvS is offline
 
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Default Drill bushings

Quote:
Originally Posted by WingsOnWheels View Post
The 6A kits don't come with the gear towers predrilled, only the later kits, 7A, 9A etc. My finish kit was circa 2012, gear towers are drilled to the leg, but not to the spar. For the taildraggers, you are correct.

To drill mine I used a series of nested metal tubes as drill bushings, worked very well.
How did you drill the enlarged 1/4" holes in the spar?

For the pilot holes in the weldment, I also used a drill bushing in the existing holes in the spar (with a piece of 3/16" choke cable sleeve, as per the construction manual) and that worked well. The difficulty I had was drilling the 1/4" holes through the actual spar and ensuring they were perpendicular, especially with the weldment in the way.
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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 : 08-18-2021 at 04:47 PM.
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  #6  
Old 08-19-2021, 06:27 AM
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It's been a long time, but as I recall, I used piloted bits for that operation and did all the drilling from the backside of the spar, including the final enlargement. And I'm not sure where I got the bits; a quick Internet search did not find them at the usual suppliers.
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