This is one of the best pieces of advice I was ever given. When building
a kit or ARF the instructions almost always state use 2-4 sheet metal
screws to attach the landing gear to the plywood doubler. All well and good
but I have found from experience that if you replace the sheet metal screws
with 2 nylon bolts ( like wing hold down bolts ) and you hit a bump/depression
/curb or other assorted obstacle you will not rip out the entire underside of
your plane ( i speak from experience ! ) all that will happen is the nylon
bolts will shear

A couple of tips re this technique - 1st drill out the plywood doubler to a slightly
smaller size than the bolts and then tap out the doubler to the correct bolt
size - makes them nice and snug. 2nd - always leave at least 3/4 in of bolt
protruding on the inside of the fuse as this gives you something to grip if
they do shear. 3rd - running a nut of the appropiate size up to the bold head
and slicing the excess material on the bolt to match the nut hex shape will
allow you to use a socket to attach and detach them ( much faster ) and
lastly to ensure they do shear when they hit something ( hey trust me it happens !)
it can be helpfull to take a drill bit aprox 1/3 the diameter of the nut and pre-drill
about 1/3 to 1/2 the length of the bolt - This also works great for wing hold down
bolts incidently ( a drill press is very useful for this )

This technique has saved my bacon more than once and while it may take a
little longer than screwing in 4 screws it is substantially shorter than a complete
rebuild of the underside of your plane

Hope this saves someone a rebuild - REBUILDING SUCKS !!

Christopher

Bingo, you nailed it. On the maiden of my Easy Sport, I had to make a landing in a less than perfect spot and the bottom of the fusilage got ripped out. I am a firm believer in using 1/4 x 20 nylon bolts for landing gear and tapping the doubler. It seems that three bolts hold quite well and will let go instead of the fusilage.

Good advise.

Ok, I'll just play Devil's Advocate here.

While many people use this system (and it is a good one) it does have one drawback.

Often in a rough landing, the landing gear can depart the plane long before anything would have broken. And often, as the gear tumble back (Or more accurately, as the plane slides on its belly over the tumbling gear) a good amount of damage can be done that would have been prevented had the gear remained attached.

So... Pick your poison.

1/4-20 is too big. It take a bit of force to break a nylon 1/4-20 bolt. I use a 10-24 nylon bolt on all my landing gear and hve never had them come off unless they needed to.

Another tip, mount the bolts as near to the outside of the fuse as possible. If you have the bolts farther inward, you put a high tensile load on the bolt due to the flat part of the gear on the fuse belly trying to bow downward on a hard landing which can strip the head right off a nylon bolt.

I'm on MinnFlyer's side of this one. I've splattered lots of planes and haven't ever had an LG part company. If you're talking strictly about ARF's then maybe the problem is the poor fit of the glue joints and not the landing gear?

Great advice from everybody but another thing is that if the bolt ends are slotted to take a screwdriver first and protrude into the fuse after insertion, if they do shear as described, it's easy to just screw the remaining bit of bolt out from the inside of the fuse and replace.