A Rather Unique Incident.

falcon1970

traveling home from UCamp, I stopped at a rest stop on I-44 a few miles east of Springfield, MO.  After "resting" I noticed something hanging down from the back of my TAB400.  Turned out three of the four #10x3/4" hex-headed self-tapping screws had vibrated out and the aluminum strip holding the rear end of the Coro-plast belly pan was what was hanging down--held by the one remaining screw.  It had been dragging for awhile since two feet of the five foot strip had been ground away.  There were probably no sparks since the strip is aluminum, so I guess no one thought I was a moving bomb.  However, somewhere along I-44 there are (or, by now, were) three screws long enough to cause someone (or several someones) a tire problem.  If you found my screws I apologize but I really don't need them back.
I put this incident down to the generally poor condition of our interstate highways.  I usually take state roads and US highways just for the scenery.  I really haven't been on the Interstates for quite awhile.  I was surprised to discover how poorly (in general) they are maintained.  Driving on them is like driving on a washboard dirt road.

Ratkity

Wow! Are you getting the aluminum strip replaced?

falcon1970

No, I just used 1 1/4" fender washers around the screws when I reattached everything.

N7SHG_Ham

Did the screws come out or break? I ask because one of the screws on my new 400 was broken, over torqued at the factory, had quite a time drilling out and replacing. This self tapping screws have a lot of friction, seems difficult for them to back completely out?

falcon1970

They backed completely out.  The screw holes were completely clear.  I have noticed that there had been several attempts at installation in several locations.  That is, there were several holes in the plastic belly pan where an attempt had been made to install screws.  I have found it is better to predrill small guide holes when using self-tapping screws.  That rather defeats the idea of self-tapping screws, but it is easier to install the screws.  As a precaution in case the original holes had been stripped, I used one size larger screws.  That is I installed #10 screws in place of what I think were originally #8 screws.  I suppose it would be wise to work up enough enthusiasm to check all of the remaining screws.  Although it is tough on an old fat man to squirm around under the trailer I suspect there may be more loose screws--on the trailer and on me.

gspdx

I think I need to do a good inspection.  I have noticed the mine hangs done a little more than I like between the screws so maybe a few extra screws are in order.  I might even add some reinforcing strips.  Not sure at this point.

Certainly nothing wrong with drilling small pilot holes and adding some fender washers though.  

DigitalSorceress

Hmm I'm going to remember to keep an eye on those screws... surprised there's not some thread-lock on em

TerryV6

Glad you discovered that...  

My wife would have told me I had a screw loose....  

davel4wa

Tsk, tsk, poor manufacturing techniques at work here. The obvious reason for using these self drilling screws, probably sheet metal screws so not self tapping, is speed of assembly. If there were multiple attempts to insert those screws that may be frustrating the speed intent. They make a lot of trailers and quite possibly this particular assembly may be shared across multiple models. Although nuCamp is probably not all that interested in adding additional manufacturing steps it might actually serve them better in the speed arena if they predrilled both the aluminum trim piece and the mating frame piece. Adding a keying pin on one side or the other would insure that the alignment is consistent and installation is speedy. Just sayin'.

davel4wa

DigitalSorceress: Not too late. Remove the screws and add screwlock, although I'm not sure it would be too effective on sheet metal screws. Worth a try though.
On the other hand, since you don't need to be in a hurry, remove the screws, drill the frame holes out to an appropriate size and tap them. Now you can use machine screws with screwlock which will work just fine. Just be careful of whatever might be above the frame member, like a water/waste tank when drilling.

N7SHG_Ham

I am pretty sure the frame is pre-drilled, after drilling out and replacing one of these, I see no way the self tapping screws used could punch a hole through the frame? Also, the ones I checked on the front where I had to refasten the trim are pretty tight, I just don't see the ones on my unit backing out or need for thread locker.

davel4wa

Having been a recent owner of a class A motorhome from Winnebago I can confirm that even long time RV manufacturers do in fact use self drilling screws in metal that you would think would not be advisable. On a trip two years ago a carpeted kick panel above the foot space of the passenger seat fell out on my daughter's foot. One side of the panel had a piece of aluminum L into which the screw was fastened. That was fine. The other side, unfortunately, had the 1/8" steel dashboard support behind it. Now, working blind, the assembly tech put the screw into what is a really small tight target and the screw encountered the head of a bolt and promptly slipped to the right and entered the interior sidewall. That held it in place until sufficient vibration caused it to fall out.