Floating pontoon

[[70521]]

Why? what statutory powers do they have?

They have a huge amount of power that influences those with statutory powers.

 

[fisherman]

I already have 8 barrels for this build is it not advisable to use that many can I have to much buoyancy...?

all it means is the barrels will be higher in the water, there is 200kg of buoyancy in a barrel, that load would just submerge it. Draw a schematic or scale drawing of walkway length vs rise and fall, to get an idea of the range of angles you will have to walk on.

 

[Quandary]

They have a huge amount of power that influences those with statutory powers.

I think the problem is the way they tend to wield their 'influence' and spend their cash, you only need to read islanderand sailor Ian Mitchell's 'Isles of the West' to appreciate the malign selfish influence their money gives them to control struggling island communities.
I like wild birds but abhor the RSPB.

 

[Quandary]

I have just had a quick look at the tides in my area it looks to be around a 2.7m range
So at low tide to bridge the muddy bank the walkway will need to be around 5m long ?
I'm still in the planning stage at the moment so any advice is much appreciated

With a 3m, drop your 5m. long walkway is going to be very steep and is going to roll right across the pontoon as it goes up and down unless your restraining structure is parallel to it so that the walkway and restraining struts move out horizontally together. Your walkway can be made to span by using a light latticed structure forming the sides rather than heavy beams. ( timber to carry domestic type loads over 5m. span would be something like 400 mm. deep) But if you build it as a latticed guardrail it can be made from 4"x2" if the joins are bolted.
Anything that is formed from triangles with fixed corners is much stiffer than four sided shapes.

What I would do
Construct gangway as above and secure to a cast pile on the bank as far out and as low as possible at one end, A -B; another pile at the same height with a beam at the other end. C-D; This beam would be two struts forming a horizontal triangle with its base as the side of the pontoon and ties across at intermediate points. It does not need to be symetrical as long as it is triangular, An 8 mm steel wire from A to D and another from C to B to restrain the pontoon against the current.
The pontoon would be a cellular raft with a float in each of the cells, a strong spine down the middle or the inside to give it stiffness, again this could be triangulated rather than solid. Constructed ashore and floated into position.
Does your pontoon have to come ashore in winter?

 

[fisherman]

that's why I said Youngman board, but they are expensive, £200 for 6m. Home made can be stiffened with a centre drop strut and wires in tension with bottle screws underneath.... or diagonal struts in compression on top which is easier with wood

 

[fisherman]

dealing with the rise and fall, consider mooring it like any boat. stakes on the bank for and aft, breast ropes for and aft, springs also. If the gangway is set ashore between the stakes at the same height the whole lot will go up and down in unison, the gangway could be fixed with hinges on the pontoon. But, if you went for a single hull just to hold up the outside end of the gangway, the g/w can be bolted to the pontoon, which will simply roll as the g/w angle changes.
PS, I would moor the boat independently as well as to the pontoon.