Probably should have read up on this before I designed and built this, but I think all is not lost despite not having been prepared. Galvanising.
Three areas of concern in this thing:
- Seal welded overlapping surface in the hinge bars, though this is well under the 10,000 sq mm min for venting
- Sealed cross member section 35x35 box
- Area around welded in hinge bars, definitely has some hollow areas, but probably all drain very well naturally
- Two seal welded overlapping surfaces between box and hitch mounting plate, see next post (EDIT)
For the former, I just measured and this is the result: 40x40x16 bar with a trapezoid with 85mm sides, which would worst case be 85x85=7225 sq mm, but is much less. Thanks to wikipedia, I know that it's 40x85=3400 sq mm, a third of the threshold for venting.
https://en.wikipedia.org/wiki/Rhombus#Area
The sealed box needs to be unsealed 4x or more. 35x35 = diagnoal of 49.5mm, drain holes must be minimum of 1/4 of that, so drain holes must be 12.5mm or greater. I have a 15mm bit that exceeds that. Vent holes must be 10mm or greater. I'll talk to the galvanisers first and see what they have to say. 10mm will be my preference, but I'll accept larger if they want it.
For the latter, I'll need to show them and discuss.
Reference for all of this stuff, page 35 of
http://www.galvanizing.org.nz/docs/Desi ... nizing.pdf among others.
Hopefully it's not impossible to have galvanised! I'd even be up for replacing the box cross member with angle cross member to achieve this if required.
Anyway, as soon as the caravan is road legal, I'll take it somewhere, park it, put it on a block or two, and remove the A-frame from it to fix it up and get it treated.
