I was at a EAA 105 meeting years ago (the RV club) and someone brought up the subject about wooden box spars and the need for vent holes in closed off wooden structures. The purpose being is to prevent dry rot not for pressure relief. If you were going to strap a rocket to the belly and fly to space you might need vent holes so the shear web wouldn't burst. What was discussed at that meeting was moisture accumulating in closed off wooden sections and over time causing dry rot. I took the time to carefully coat all the inside surfaces with spar varnish and not get any of the glue surfaces with that varnish before assembling my spars. If I was doing it again I'd just coat the entire inside of the shear webbing with epoxy and staple it together. I think a 1/8" hole in the shear web of each closed off section wouldn't hurt though. I didn't drill my spars either and since 1980 all is well.
Joe Beyer Pdx >I presume you are referring to pressure relief holes.That is one of those >issues which has been discussed many times on the KR Net and can easily be >found by searching the archives. But, to answer your question, this is also >a personal preference option. If you feel better having the relief holes >then drill one in each chamber or through each vertical rib inside the spar >as you build it. To our knowledge there has never been a spar "Explode" or >delaminate due to pressure from altitude. I opted not to install them in my >spar and I have not fallen out of the sky. YET!!! >Mark Jones (N886MJ) >Wales, WI USA
