Many of the vintage and classic designs have the undercart fixed to a ply bulkhead behind the tank.  From there the wires stick down through the bottom fuselage sheeting.  It is all lovely when first built, but after a couple of flights the flexing of the wires tears the balsa away from around them leaving plenty of access for the oil to start soaking into the raw wood.  Other than changing the design entirely (too late anyway if it is already built), does anyone know of a foolproof way of sealing those gaps to prevent oil ingress while still remaining true to the original plans?

Hi Charlie,

I plug the holes neatly with clear silicone caulking.  Tail wheel outlets, too.

I slide the tubing over the wire rather than splitting it.  another possibility, which I have not done, would be to make a plywood thing for the gear to exit through rather than balsa.  I have made that kind of gear removable.  Put the wire in a ply sandwitch and make a ply lined pocket for it.  Run a bolt through to hold it in place.  This is for having different gears for hard surface or grass.  It is a little heavier, but then I build tail heavy airplanes. 

   We generally only fly off grass around here (soccer/football fields and a couple of guys have their own circles).
Some times these grounds are a bit "unloved" during the off seasons for the sports and our models cop a hard time because of this.
   What we tend to do if we can afford the weight in the .35 and larger sized models is to use 5/32" wire instead of 1/8" for a bit more rigidity.
   This combined with soldering a small washer on to cover where the wire exits the bottom of the fuse.
   I generally rough up the back of the washer first so that some thin CA can be wicked in afterwards to give a good puchase onto the bottom sheeting.
   I have seen models with  hundreds of flights on them and there is not even a crack in the paint around the undercart legs let alone the ugly oil filled slots that occur when running 1/8" wire.
   This seems to be the best solution for us as we only ever fly off grass and don't require interchangeable landing gear.
Rob.