Sometimes the cabin was full of Elmos lightning es.
That might be fun but you can totally forget any avionics working 
Is it just a matter of most IFR operations in something like a Bellanca or composite homebuilt not bring in weather conditions of concern? I find that a little hard to believe.
It’s a very good question. But as with so much in aviation I wonder if there is a lot of risk compensation taking place. Would somebody be flying a wooden plane, with (a bit of an assumption here but you get my drift) hardly any avionics inside, in hard IFR conditions?
We all know how much GA activity reduces in IFR weather. Here in the UK, in OVC005 it is probably 1% of what it would be in CAVOK or even OVC020, and all of that 1% will be hard IFR aircraft, or some nutters scud running at 400ft.
It is possible to get a lightning strike in VMC, obviously, but you will hardly be unaware of the proximity of the object it’s going to come out of 
I suppose an even older wooden example would be WWII e.g. Mosquitoes.
I find the idea of a direct lightning strike in a carbon-sparred or wooden aircraft a bit alarming – presumably fire/structural damage would be more likely than in a stressed-skin aircraft.
All wooden aircraft have all the metal parts bonded together with metal braid apart from the Lightning issues it is essential if you want the ADF to work.
GRP aircraft use the same principle but usualy use aluminium strips to bond the metal parts together.
Would somebody be flying a wooden plane, with (a bit of an assumption here but you get my drift) hardly any avionics inside, in hard IFR conditions?
Given that Bellanca Vikings were equipped with ‘State of the Art’ IFR avionics when they were new, I would say the say the answer is yes, they were and sometimes still are flown in hard IFR conditions. Have modern avionics increased the propensity of (some) pilots to fly in hard IFR over the last few decades? I don’t think so, even while getting your drift in relation to current IFR practice in Europe
(I should clarify that a Bellanca has a 100% wood wing and horizontal tail, and a steel tube fuselage. So it’s not entirely wooden plane)
I’m not an electrical engineer. With that in mind what is the technical objective of bonding, and how must it in basic principle be implemented to make a non-metallic aircraft equivalent to a metallic aircraft in terms of resistance to the threat posed by lightning?
AC 43-13 have two references that may shed some light
Aircraft lightning protection handbook and in particular Determination of Electrical Properties of Grounding, Bonding and Fastening Techniques for Composite Materials
Fascinating docs there… 503 and 85 pages
But a typical non-certified homebuilt doesn’t do any of that. There is no metal other than structural. They are just fibreglass-skinned aircraft.
What screws up VHF comms, and presumably GPS too, is the EM radiation from corona and arcing, which is what you get when flying in IMC, when water droplets hit the airframe, and as they run off the rear end, they leave behind some electrons (or maybe the other way round) i.e. static charge. This charge then causes two problems:
The end result is noise on the radio and/or an apparent reduction in the radio range.
If the airframe is all plastic then where the charge flows will be unpredictable. Fundamentally the charge will distribute inversely with the dielectric constant (relative permittivity?) of the material, which means air gaps will have the highest voltage gradient (volts/metre) across them and that is where arcing will start, when the air breaks down. The wet surface will also be conductive so to some extent you get shielding from that but eventually the stuff has to escape somewhere. There may be some “street knowledge” on where a VHF antenna can be mounted so it still works.
Thanks for the info and technical explanation. I’m sure I can dazzle Lancair 4 owning friends with sophisticated knowledge after I study the links. They guys I mention are currently putting in a competely new and high spec panel in their plane, in anticipation of more IMC flying.
Once upon a time in a previous life I had to worry about flow induced static electricity caused by liquid flow though pipes. It’s a good way to cause an explosion when dealing with combustible fluids.
I must say this seems strange then. Cirrus and Diamond have done what it takes to prevent this stuff, while none of the experimental aircraft seems to have done this. One can only conclude that plastic experimentals without the needed protection behaves unfavorable in IMC. But, experimentals are experimentals, the builder is in charge, and any serious builder will read AC 43-13 and similar things and find out how to properly build the aircraft for IMC conditions.
Suddenly remembered there is a German document that is considered to be “the bible” about composite building techniques. Maybe that also has some info about this? I don’t remember the name of that document, but I have browsed through it once, and it is on the internet somewhere.
I know that my Falco was built for IFR flight in the USA and it doesn’t have any bonding straps anywhere that I have seen.
