Windlass mounting/backing plate material?

Stellina

Stellina

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I have an Quick Genius on-deck windlass I want to install this winter, but the deck space available under the cover is only half as wide as the windlass. i.e. only 2 of the 4 windlass bolts would pass through the reinforced part of the deck. I need a mounting plate but what material would be suitable for it (and a backing plate) for the windlass? Would I get away with a few mm aluminium sheet or 8-10 mm marine ply?
 
I used a stainless plate which was considerably larger than the windlass bolt positions, and there was a ply pad as well - overkill perhaps, but this is not a good area to undersize, as the results could ruin your day!!!!
 
Deck winches can get some very high loadings so you need a good solid mounting.

The load must be spread over an area larger than the base mounting, a 6mm stainless steel plate with well rounded corners and top/bottom edges is needed, this will also need to be bedded to ensure the load is spread over the entire plate, a mix or resin and Micro fibres will do a good job and you can use standard resins for this.

Also make very sure ALL the holes you drill thru the deck and particularly the ply section are drilled oversize, filled with an epoxy resin and Micr fibres then re drilled to the required size to prevent water damage later on.

Avagoodweekend......
 
cant remember exactly now. I just went along to my local stainless man and asked for a suitable piece of scrap, which I then reshaped with an angle grinder. I told him what I wanted it for, and he got a suitable piece out of the scrap bin. was pretty cheap as well.
 
I am also researching material for a windlass mounting bracket, I was looking at 8-10m alluminium, I saw an installation that used similar, however they also connected a bottle screw from the windlass L bracket to the stem head fitting. This would help transmit the force to the bow of the boat and is how I intend to fabricate mine. I may struggle to get at least a 90 degree turn on the gypsy so an additional roller may be required. If you go ahead with the stainless bracket please let me know how you get on I will be fitting mine early next year.
Good luck with it
 
This is more of a generic tip about backing pads in general, rather than your specific application. If good ply is hard to get hold of (or even if it isn't) thick nylon chopping boards make ideal, rot-proof and readily available pads.

On the subject of windlass mounting, of course it needs to be a solid job, but surely the finished job shouldn't be taking all the loads of the rode. Insn't that what the samson post and/or other suitable deck fittings are for?
 
Of course that's right, but when working, especially with the snatch loads breaking out an anchor from the sea bed the loads are pretty high anyway.
Aluminium plate is OK for a backing plate but it should really be about twice the size of the pitch of the bolts in either direction to spread the load. If this is not possible just make it as big as you can. If the deck is sandwich construction you should also have spacers on the bolts the thickness of the deck to stop you crushing it. The thickness also, as an approximation in aluminium, should be 1/2 the dia of the bolts, i.e. 1/2" bolts = 1/4" plate. If it's stainless, even better, and you can then reduce the thickness, but for the DIYer aluminium is easier to work with. I agree the backing plate should be bedded on something but would prefer to see Sikaflex than hard resin for this purpose. If its aluminium a coating of epoxy tar over the finished job inside will help to stop any possible corrosion but is not strictly necessary. Hope this helps.
 
Having done this on a previous Westerly, I concluded that the deck material was not up to taking the strain, (usually a sandwich for lightness) however it is distributed with backing filler etc.

The key area of strength is the hull-deck joint area: so it is important to use a material, definitely not a plastic, but something non-flexing (under the heaviest load you can imagine) that will distribute the weight to the margins of the backing pad- right up against the hull-deck joint.

So I suggest you cut a template to ensure a tight fit against the sides of the supporting space, and fashion your backplate, filling any void between it and the underside of the deck with non-compressable material (stops any deck flexing)

This works well for temporary inner stay fixtures too.

I agree with the other post saying you should lay off the strain from your windlass when at anchor - have a short heavy strop and a chain shackle (looks like an eye with a claw attached) to carry the load to a neighbouring cleat. Otherwise, you may well loose the whole gear and a bit of your deck over the side in a violent snatch!

PWG
 
I hadn't thought of connecting the plate up to the bow but have seen solutions where the mounting plate extends forward and fills a half of the locker opening.
[image]http://www.thehurdles.com/images/IMG_0371.jpg [/image]
I'll post some pictures when I decide how to do it.
 
I have gone through a similar process with various winches. Having produced a battleship variety of backing plate for anchor capstan and sheet winches, I discovered that they were secured to the deck with M8 (Quick windlass and ST44 Lewmar) and M6 (ST40) screws!

I got to wondering about the sheer strength of these and there is nothing you can do to beef them up. I guess the manufacturers have done some sums?!
 
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