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prkaye

Well Known Member
I'm going to make all my floors removeable (mainly because this avoids the need for another "pre-cover inspection" as required by Canadian rules). Next week I'm going to be assembling the center fuselage, with all those floor ribs. Question, do I need to put all the nutplates on the floor ribs now, or can that be done later, after it's assembled and I'm ready to put the floors in?
 
You can. But why would you want to? I did it AFTER the ribs were installed and the one problem I had was getting at the underside of the rib to debur. Minor thing, yes, but still frustrating.
 
prkaye said:
I'm going to make all my floors removeable (mainly because this avoids the need for another "pre-cover inspection" as required by Canadian rules). Next week I'm going to be assembling the center fuselage, with all those floor ribs. Question, do I need to put all the nutplates on the floor ribs now, or can that be done later, after it's assembled and I'm ready to put the floors in?
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Phil,

You can do it either way you want. I think you will find, however, that in the long run it will be a much easier and faster job to go ahead and install the nutplates on the individual ribs now while you are seated on a stool at the workbench as opposed to waiting until after the ribs are installed and then finding that access and installation convenience is significantly diminished by comparison.
 
Phil,
The fastest way is to IGNORE the instruction to rivet the floor ribs to the rear spar now. Leave everything clecoed. Once you have all your skins drilled and clecoed on, fit the floor skins with the fuselage upside down in the jig (or sawhorses). Once the floor skins are drilled and clecoed on, take EVERYTHING apart for deburring and dimpling.
Are you going to use #6 or #8 machine screws to hold down the floors??? The rest of my advice will vary depending on what size screws you use.
Regardless of screw size, you can drill and fit the nutplates to the floor ribs while the ribs are out and apart. After you drill, deburr, dimple, (Alodine if desired) & prime you floor ribs, you can install "most" of the nutplates before reassembly. This will take some head scratching prior to disassembly, because some of the nutplates must be left off for now. Premature installation will impede or prevent easy riveting of the ribs/skins during reassembly.
Charlie Kuss
 
Are you going to use #6 or #8 machine screws to hold down the floors???
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Was thinking #6 to save weight, but maybe #8 would be easier to work with, and the weight difference would be negligable? Recommendations?
 
Hey Phil. Why not just make a couple of access panels that are screwed down to the floor?

I put my strobe PSU underneath one, and the other is just for inspections. That way it's a few platenuts rather than dozens. Your MD-RA inspector can view your internal handiwork with an inspection mirror.

Platenuts and screws are unneeded weight if you never plan on removing the floor. A couple of well-designed panels will give you all of the access you need. When I added a flap limit switch, I drilled out some rib tooling holes for snap bushings using my right angle drill through one of the panels. No problem.

Vern
 
prkaye said:
For putting the nutplates on the floor ribs (to make the removeable floor)... there's one spot where the nutplate won't fit... one side of the nutplate overhangs the edge of the flange. What did you guys do about this?
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Phil - I bought some one leg dimpled nutplates to solve that exact problem. I think I have a few left over if you need them. I'm on the road right now - I should be back on Thursday.
 
prkaye said:
For putting the nutplates on the floor ribs (to make the removeable floor)... there's one spot where the nutplate won't fit... one side of the nutplate overhangs the edge of the flange. What did you guys do about this?
Photo attached...
[URL=http://img259.imageshack.us/my.php?image=nutplatewc4.jpg][/URL]
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Phil
Use a "one leg" nutplate for these areas. I had to use several of them. Are you planning on pan head screws or flat head screws for retaining the floor skins?
Per your earlier question, I asked the same thing of my local RV guru, Jody Edwards. Jody said that his experience (25 + years as an A&P/IA) he found that #4 & #6 screws sometimes would break when you attempted to remove them. He said this didn't happen with #8 or larger screws. I used #8 flush screws on all my flooring. In retrospect, flush screws offer no advantage along the left and right outer edges of the floor skins. These areas will never have seat cushions on them and your feet will never be placed in those areas.
I can send you photos of my floor skins with the nutplates attached if you desire. What model RV are you building?
Charlie Kuss
 
......there's one spot where the nutplate won't fit... one side of the nutplate overhangs the edge of the flange. What did you guys do about this?
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Nutplates come in many, many variations. In this situation, use a single leg nutplate also known in some circles as a "one lug anchor nut."

http://www.aircraftspruce.com/catalog/hapages/anchornuts.php


I used #6 and #8 truss type screws because they are easier to install and service. Besides, when the rear seat is in place, the only exposed screws are around the perimeter of the floor anyway.

 
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Weight is a big factor in the performance of these aircraft. Maintenance also plays a big factor in the continued safe operation in the life of an aircraft that could be measured in decades rather than years. Someone mentioned access panels and I agree completely. Yes we are supposed to check operational items under the floors at each annual. Ask yourself if it is more likely to be done if there are six screws to be removed or thirty five to be removed.
I often use self tapping screws to hold down floor panels that will not be removed on a regular basis, and nutplates on access panels. Self tapping metal screws get a bad wrap and should be considered by more builders. They are not particularly good where items have to be removed often, but in other cases they are a perfectly good alternative. We see them on old Cessna aircraft and they look bad as they are often loose or missing, but these aircraft are antiques and so in reality the screws have done a pretty good job. There is always the option of putting in a nut plate at a later date as well. I think that many builders get nut plate crazy and nutplates are not without their faults. When a screw head strips, and they often do, you now have to drill out the nutplate and replace it. Sometimes it is a location that allows this sometimes not. Think maintenance. Pop rivets are also a cheap and light option for those floor panels that will likely never have to be removed. If they do then the rivets can easily be drilled out.
Also, even though number six screws and nutplates are lighter than # 8 hardware, they also are not as strong and the heads tend to strip easier than a #8 screw. I try to use #8 hardware in the whole aircraft as it makes maintenance much easier and it also means one less size of screw to keep in inventory. I recently helped someone remove their cowling, on a ramp late in the day, he had three different size screws and we could not find all of them when it came time to put things back together. Fortunately another builder was there who had some extras of an odd size.
Think maintenance; you will not believe how fast your first annual inspection comes up and all those floors have to be removed.
 
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Why?

I agree with the access panel idea. I didn't do it after reviewing and evaluating others planes who have made removable rear floors. After doing so everyone of them has said that is was major waste of time, money and weight. Also, there is nothing under there that moves, rotates or controls anything. So, I would ask, why go to all of this work?

An access panel on each side is less work and could be beneficial. See Dan C's work.

A simpler solution would be to order the RV Flight bags that fit behind the seats and will hold everything you could possibily carry in the way of tools and emergency items with space left over. Also, they leave the main baggage area completely exposed for other stuff.

Just my thoughts to try to save you guys a lot of unneccessary work.
 
Part of the problem is canadian inspection regs which require the inspector be able to see everything... theoretically every rivet. Removeable floors allow him to do this after the plane is totally built, removing the need for a separate pre-cover inspection of the fuselage (and saving the builder the fee for this). By the time we make enough (and large enough) access panels to facalitate a view of everything, it may be just as good to make the floor removeable (and it may look cleaner than having access panels all over the place).
I counted about 100 extra nutplates and screws. I should put these on my digital scale to see how much extra weight it comes out to.
 
Years ago, I asked Van's if it was okay to make the floors removable and the terse answer was "Well, yea sure.......but it's going to take extra time."

"Extra time" in this situation is a concept that does not compute with me.

This topic may well fall under the "ongoing debate" category. Thankfully, whether to make floors removable or not is strictly the builder's option. All experimental builders enjoy the uncommon freedom to do things exactly the way they want to do satisfying their own goals that go beyond the expectations and opinions of others who may disagree.

I've never been polled about my preference so you can't count me among those who conclude it is a waste of time. In the -6A, I have a flap transducer, an AOA computer and an ELT....all mounted underneath the baggage floor. I could have spent as much or more time fabricating dedicated access panels for each accessory as I did just making the floor removable. In addition, I made all the fiberglass tips removable and that simple mod greatly eased pulling them a year later to bring home and paint at my leisure. As an added bonus, I unexpectedly discovered a sizeable hornet's nest or something like that fashioned from mud and firmly affixed to the structure under the left horizontal stab tip. Sure I could have drilled out a series of pop rivets to gain access but call me opinioned if I percieve such use of pop rivets in RV construction as a personally undesirable option.

Given the chance, as a past thread asked...what you would do differently? Well, as far as making the floors removable...I did it exactly the same way the second time around. Pop riveting the floor in the -8 was never seriously considered.

You never know what you might want to improve later. Already in the current project, I have removed the floor to improve wire routing, add a coax run, and add a custom modification to the rear seat joystick area. I'd like to know how those who advocate pop riveting the floor into place permanently would run additional wires. Simply snake them through the nearest lightening hole and let em flop around in perpetuity? Hmm.

In all the years I worked on combat planes, I never once seen ANY aircraft structure made permanently inaccessable. Old habits die hard. So while some of you may dismiss such work as extra weight, extra work, etc., count me among those happily populating the other camp, thank you very much. We all know the drill here...YMMV.
 
I am proposing access panels only for inspection reasons, not storage. Obviously if there are no moving parts then there is no need to remove the floor unless corrosion is suspected. I am talking about little inspection doors under the seat of a RV4 or a rocket, or two little doors in a RV7 rather than lifting up the entire floor panel. All you need to do is to be able to verify fasteners and give the rod ends a squirt of lubricant.
 
Nut Serts?

Why couldn't one use nut serts for this application. It doesn't seem to be structural and they are a lot lighter than nutplates. The hole size must be very accurate to ensure that they won't spin, but it seems the holes could be reamed to size. I have alot of #8 aluminum nut serts made for .015 to
.093 thickness that I'm planning to use unless someone talks me out of it.
 
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