avon wood floor

[markg]

we took the inflatable up to trefor above pwyhelli (sp) today, water was pretty flat, its a biggish one at 16ft and we have a mariner 30hp on it, on approaching planeing speed the inflatable keel started to push the wooden floorboard up, the board started to make cracking sounds, so i backed off the throttle, i had some bother with the valve holes in the floor for the inflatable keel being in the wrong place, i am thinking a previous owner has replaced the floor and made a mess of it, the ply floor is only 10-12mm ply
what is the usual thickness and grade of ply that avon use? i am also thinking of reinforcing the replacement floor with some 40mm ally box section riveted into the topsides just under each tube and one over the keel to add stiffness
any thoughts?

[m chappelow]

Hi mark,some boats do flex and crack a bit when at speed and in lumpy seas or when surfing down a wave and the bow tends to start stuffing but a lot depends on how many boards the floor is made up from ,thats why most work boats or lifeboats have a one piece main board with a small seperate front board ,all the 15 or 16 ft sibs i have owned have had one piece main board of usually about 1 inches or 25mm thick ply and it makes a huge difference, down side is if you have the boat on a trailer its fine other than that the board will have to go on a roof rack if you transport the boat by car unless its a stretch limo , but from your incident with the hole not matching the valve its looking like they are not the original boards . if you are going to make a new one piece board i would take the measurments from the boat and not the old boards and remember to round off or bevell the edges ,at least you will get the valve hole in the middle ,regards mart.

[markg]

thanks martin, i cut a new hole for the keel valve in the front board to centre the keel, the main deck board is 1 piece and is 10ft by 4ft and 15mm thick, i dont think its rigid enough, i thought about bonding 3 pieces of box section ally to the main board to stiffen it, i was going to put 1 either side of the inflatable keel underneath the main floor and 1 directly above the keel on the topside of the deck, but reading your reply makes me think i really should start with a thicker and stronger main board and maybe reinforce it also.
its already on a trailer, i built one for it last week, first trip out was a 2.5 hour tow each way, it did tow well and we had no problems with the trailer, its probably a bit stronger than it needs to be but i have visons of a 5.4 searider sitting on it so built it accordingly,
its probably the only sib trailer with brakes and a 4 ton safety wire
does the air pressure of the inflatable keel make much difference and how would i go about makeing a new floor fit properly i am thinking cardboard templates with tubes inflated but keel deflated would be a good starting point
thanks for your help, mark.

[chris123]

Assuming it is a leisure Avon not a commercial Avon, that definitely does not sound like the original floorboards.

There may be exceptions, but AFAIK the standard leisure Avon floorboard arrangement for many years consisted off:

1. A plywood 'plank' approx 150mm x 20mm near the front of the boat, permanently attached to the boat.

2. A triangular (or for the pedantic trapezoidal) floorboard (with hole for keel valve) in front of this plank (approx 10mm thick on my Avon with a 10mm stiffener strip along the aft edge).

3. A set of square floorboards (3, possibly 4 dependent on boat length) between the fixed plank and the transom. Theses are thin (approx 6mm thick) with a stiffener all around the edge (approx 25mm thick and 40mm wide).

4. The set of square floorboards have a cutout on either side to take an aluminium and wood triangular section bracing piece.

The fit of the floor is pretty essential to the performance of a SIB - the RNLI use bottle screws to tension the floorboards, on my Avon SIB I need to use a bolster chisel to lever the aft floorboards into place behind the fixed plank.

I think it will be quite difficult to measure up a SIB and from that work out the size of floorboards required - you may be better off trying to find someone with the same SIB so you can take measurements from their boards (try posting full model details and photos here, you never know your luck). It might also be worth calling Avon - I have found them helpful, but obviously there is a limit to how much help they can / will give.

Cheers

Chris

[markg]

thanks chris no 1 and no 2 appear to be correct but 3 and 4 are nothing like i have, my digital camera is knackered but there are a few pics on the ebay listing, (take no notice of the price the seller contacted me after the auction and i gave £350 for it)
http://cgi.ebay.co.uk/ws/eBayISAPI.d...MEWA:IT&ih=015
the floor consists of 1 10ft main deck board and the triangular bow section thats it, none of the braceing that you mention they are just plain boards no lips or edges to brace against each other, the main board seems to be a pretty good fit but the bow section is not so good , should the floor be a tight fit when the tubes are deflated? and do you have any pics of the braceing on yours?
thank very much, mark.

[chris123]

Hi Mark,

Have a look at the photos and info here:

http://www.rib.net/forum/showthread.php?t=10604

Hopefully it will help. A word of warning - the fitting instructions in posts 2 and 4 is for a different floorboard arrangement (one that doesn't have the fixed 'plank')

Cheers,

Chris

[markg]

thanks chris thats very helpful, i dont have the ally extrusions that fit to the edge of the floor under the tubes, so i have sent an email to avon to find out where i can get them from