Fitting the step

I have pulled the WD-657 external steps out the third time and put them on my RV-7a, but I still cannot see how these are properly fitted.
I already have the holes cut in the outer skin, F-623, and F-625. The outer hole is a bit large (almost a 1/4" gap all around), while the hole through F-625 is tight (just to establish my baseline).
Two problems come up:
1) Looking at the gap at the bottom of the flange (of WD-657), there is a small gap (1/16") at the front portion, while there is a large gap starting at 1/4" at the rear portion. Part of that can be solved by bending that flange, but for the flange right next to the tube, no amount of bending will close that gap. The only way to close the gap near the tube is to rotate WD-657 around the vertical axis (by either extending the hole in F-625 forward or extending the hole in the outer fuselage skin backward). A lot of rotation and hole elongation would be required. That seems wrong.
2) The tube buts flat against the rib F-626. This adds to my problem, because it does not allow me to push WD-657 any deeper into the fuselage (and I think it needs to move at least 1/16 inboard, regardless of how I deal with my asymmetric gap). To solve this secondary issue, I can shorten the steel tube (irreversible and not very adjustable) or cut a hole into F-626.

How have others dealt with this situation?
Here is a picture of the gap between the flange of WD-657 and the fuselage side skin as seen from the below.

I can't remember if I cut a hole or cut off the tube. Mine is also a 9 and may be slightly different. The flange doesn't even come close to fitting when you first start. Here is what mine looked like before and after beating the flange into submission!

There may be some slight misalignment in the holes drilled through the interior baggage ribs. It shouldn't be a problem, this is a really difficult cut to make perfect. The Nylon blocks that come with the steps and the holes drilled into the skin will bear the bulk of the force, so do not worry about grinding the holes larger to make it fit. A dremel tool works great to make the room

i had the same gap

at the bottom that you are talking about. I didn't fill mine with anything, but i think i will on my next build. Its not a strength issue in any case...

You'll have to bend that flange around quite a bit to make it fit the curve of the skin, and some of it can't be bent enough - just trim it.



Here's the inside on my 9A.

Thank you very much for your feedback! That is all very helpful information.

Thinking more about it, I arrived at very similar conclusions:
1) one of my problems is that the fuselage is still upside down, so I get to stare at the worst fitting part, which will be invisible from the normal perspective.
2) the hole in the intermediate rib F-525 (which is perfectly tight right now) needs to be enlargened. This is not a structural support.
3) I will shorten the tube (a little bit at a time) and not cut a hole in the next rib. This leaves more freedom to adjust.

The pictures you posted all look very encouraging. I will report back with a better fit, but that may take a few days (or weeks) until the canoe is flipped.

same thing with my 7A

Funny...I was just asking about the same thing yesterday and how to fill the gap. Here is the post link..


http://www.vansairforce.com/community/showthread.php?t=80050

Step installation!!!!!!

....You can save yourself a great deal of frustration later if you address an issue with the step now, before you finish the installation. These steps virtually all crack and fail on the underside next to the weld at two to three hundred hours. Do a search on the forums for this problem and you will uncover a vast amount of information. I welded a 4130 doubler back-up patch on the problem area then took them to the heat theater, had then annealed and re-heat treated. I used countersunk Phillips screws to re-install so should I have another problem they can be removed easily. Also if you know the intended color of your plane is this area it is worth it to have the steps powder coated as this is a far more durable finish that will hold up to standing on it with no damage. Hope this can save you the frustration I went through. Regards all, Allan

What you are encountering seems to be a very common problem with these steps. Mine didn't fit right either. I'm wondering if beating on the flange too much weakens or stresses it enough to lead to future cracks, like some builders are experiencing. Rather than do that, I enlarged the holes in the skin and internal baggage area ribs to give enough "wiggle room" to allow the flange to sit flat on the fuselage skin. You can read much more and see a lot of pictures in my build log, starting here:

Installing the Steps

Here's what I started with:



More work was done a few days later, in this entry:

More work on the Steps

Here's the end result, after a lot of work: