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Flap pushrods

rondawes

Well Known Member
I'm not the builder.

I decided to replace my stock flap pushrods with the hex ones from Vans. I ordered them and received them with a sticker that says VA-256.

I finally got round to installing them and noticed that they are longer than the ones I have now. So either:

A. I'm supposed to cut them down to the proper length for my plane, or

B. I was shipped the wrong part for my plane.

I'd appreciate enlightenment. Thanks.
 
I'm not the builder.

I decided to replace my stock flap pushrods with the hex ones from Vans. I ordered them and received them with a sticker that says VA-256.

I finally got round to installing them and noticed that they are longer than the ones I have now. So either:

A. I'm supposed to cut them down to the proper length for my plane, or

B. I was shipped the wrong part for my plane.

I'd appreciate enlightenment. Thanks.

The hex pushrods are a part from the 9 model which are a little longer than called out for the pushrods on the 7. Trim them down to the specified length per the 7 plans.
 
What is the reason for changing from the original push rods? Is there a problem with the design or the specification?
 
Was the part number you ordered different than the part you received? If so, send it back and get the correct one. If they have a one size fits all for this part, you may have to trim it to fit your airplane. If you do that, make sure the thread depth in the newly trimmed part is deep enough to accept the rod bearing. If you have to drill deeper, make sure you use the right drill size for the tap you are using - not sure if it’s 10-32 or 1/4-28. The drill size is smaller than the tap size - don’t have the chart with me, but easy to find out.

The hex rods are an improvement, not only in strength, but also in installation of the bearings and stop nuts.
 
Hex rod improvement ?

My 2009 3B kit had hex rods. My 1999 RV4 kit has round rods. What is the shortcoming of of the round rods if you follow air speed suggestions for flap deployment ? I can easily replace them, just wondering why bother.
 
The loads on the 9’s larger flaps necessitate the more robust hex rods.
The standard rods are fine but have less margin should a flap over speed occur.
The standard rods are also less forgiving of poor fabrication or wear from interference where they exit the fuselage. Some have failed resulting in a split flap condition.
 
When you shorten the new hex rods, take an equal amount from each side. This will prevent you from having all the excess taken off one side and being left with a shallow threaded hole on that end. Also check that the larger diameter doesn’t rub in the fuselage holes.
 
Ok, you did not build it, but you are the owner. So buy a set of planes to identify the correct numbers of each part.

If you order another part than in the plans, make them at least the same functional size, length in this case.

History: The 7 has a rigid AL tube, that you cut to length and cut a thread on each side. The problem with the strength was when the builder was cutting the thread not in a lathe ... freehand or however not aligned with the tube. Or the cutout in the fuselage was not enough big and during taxi on the bumpy field, the tube was quickly compromised. Then use the 9 flap rods, but you must shorten them. As others mentioned, equal on each end.
 
My 2009 3B kit had hex rods. My 1999 RV4 kit has round rods. What is the shortcoming of of the round rods if you follow air speed suggestions for flap deployment ? I can easily replace them, just wondering why bother.

Suggestions are just that. If one were to ignore the suggestions (perhaps on climb out) because of the ludicrous acceleration one enjoys with an RV, but one then wonders why normal cruise speed cannot be obtained on a particular day, the round rods might not have to be replaced, but the hex rods might be installed to future proof.

Not that I'd know. :rolleyes:
 
My 2009 3B kit had hex rods. My 1999 RV4 kit has round rods. What is the shortcoming of of the round rods if you follow air speed suggestions for flap deployment ? I can easily replace them, just wondering why bother.

There are no known shortcomings. The round rods have been tested in compression and found too far exceed the load that would ever be expected in flight plus a healthy margin.
I do not fully agree with the idea that the hex rod is easier to fabricate… If someone doesn’t have the skills to properly final drill and tap the round rod they don’t have the skills to properly tap the hex rod either.
Most things about building an air plane are new to the majority of builders. Properly learning the processes and procedures that are used, is part of the build process/experience.
 
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