My blue board is home-made 60 x 60cm. 50mm aluminium angle welded to make a frame and perforated aluminium panel pop riveted on. Hinge mechanism of 20mm tube inside 30mm tube with nylon bushes. Held down by shock cord, raised by cycle gear cable and sleeving. Very bright scintillating light.
Passed 2 ES-TRIN surveys.
Blue boards made of steel can be obtained from SRF Shipbuilding, Harlingen. They are fully automatic, one switch controlling the position and the flashing light. They measure 30x30cm, ideal for a recreational barge, and, according to SRF, acceptable to surveyors. They can be either wheelhouse or pole mounted (preferable if your wheelhouse is either wooden or collapsible).
See attached photograph. Price is quoted as Euros 1,113.20 incl. VAT.
The latest (v5) of CEVNI has yet to be adopted by most countries, but it does still give the same circumspect definition of size at 3.03.3 which is explicitly applied to a board or flag. However at 6.04 (Meeting - Normal Rules) it only allows for a scintillating light with optional board day and night - i.e. there is no mention of a flag there. That is also where the 5cm white border is stated.
That Article also says (to paraphrase) that these sections are not applicable to small craft when meeting a normal vessel or other small craft - i.e they may not initiate a "blue board" scenario - but as Art 3.03.3 specifically defines acceptable size for them it is obviously assumed that a small craft may respond to the intentions of the normal vessel with a board of its own.
I realise I didn't describe the construction of the one I made for Friesland as you ask in your post, but it is not disimilar to yours - it is shown in use at the top of the link I gave. Mine too had to be 80cm x 80cm to avoid fouling on locksides. I put a lead weight in the angle at the bottom when activated; it is kept in the horizontal position by bungey cord and the weight allows the board to drop into position unaided when the cord is released. It has survived severe winds without damage when in either position as the cord allows a certain amount of movement. It is held on the corner of the wheelhouse roof by stainless bolts with wing-nuts, and the whole thing can be easily detached and put on the roof of the accommodation if necessary on Freycinet waterways with tunnels. I only bothered to do that if the board was on the non-towpath side of the tunnel.
The rules do say that the board should be activated from within the wheelhouse. Mine requires the operator to lean out to release the bungey and then again to refix it, but Peter Voormann accepted that as OK for the Community Certificate.
Blue Boards come within CEVNI at Art 3.03.3 which says they should be "large enough to be easily visible". It quantifies this by saying “this condition shall be considered to be satisfied in all cases if neither the length nor the width is less than 1m, or in the case of a small craft less than 0.60".
I’ve not looked to remind myself of the Article and exact wording but it also says they shall be blue with a 5cm? white border.
Despite having checked both the DBA website and ES-TRIN 2015 , I can't find anything specific re Blue Board dimensions or, more particularly, installation. In my case the dimensions are not a problem, my TRIWV certificate already specifies a 80 x 80cm Blue Board to starboard at the front top of the wheelhouse. For tunnels / bridges / locks etc., it is important to me that, when not in use i.e. lying flat, it does not protrude either above the existing wheelhouse roof profile or extend sideways from same. I would be interested to hear what methods other members have chosen to mount and actuate their Blue Board and flasher (and guess this could interest other members who wish to and/or are required to have a Blue Board).
Mine is a DIY 800 x 800mm frame made up of 24 x 24mm aluminium profile housing perforated aluminium panels, topped by a 24V flasher unit. I also have 3 x 1m lengths of 30mm dia. aluminium profile still to fit, that are intended for use as a mounting axis / rotating shaft. Any ideas incl. photos and sketches/diagrams if available would be most welcome.