I don't know what the weather has been like in your part of the world this last weekend but here in the Fens it has been blowing a hoolie. Where I have Naiad parked on the hardstanding is to the North of my workshop meaning that it blocks the prevailing Southerly winds. However, when the wind strength is hoolie or greater the turbulence generated by the workshop causes down drafts in the heater flue making the heater hard to light and difficult to keep alight.

Now there are special cowls that you can buy that act like a wind vane such that the open end of the cowl always points away from the wind but the smallest one of these is for a 5" flue and costs anywhere between £130 and £300! The flue on Naiad is only 1 3/8", so it wouldn't fit anyway.

Too big and too expensive so I made myself on out of a tin can and some plywood.

After I had put that on the flue, I could easily light the heater and it burned normally.

Rough and crude but functional.

A simple vane screwed on top.

The top of the existing cowl is rounded so the tin can spins fairly easily on the "point". The automatic vane doesn't turn in light winds, but then light winds don't cause the down draft problem.