Fill up large hole in foundation plate windlass

[Pepijn]

We have to replace our windlass. Our previous windlass had the motor underneath (Lofrans Kobra) whereas the new Lofrans Tigress has the motor above deck. Over the years the PO’s made modifications by adding new bolt holes and enlarging openings. They also added a stainless steel sheet 2mm on top and bottom on which the windlass was bolted through.

One way would be to cut a large square out and add a new piece of marine ply glued with a bevel and epoxy in the opening. However, I am afraid that by cutting an even larger hole I may weaken the construction even more.

Any ideas?

[wrwakefield]

We had a similar issue when we replaced our windlass. I solved it by using 1/4” thick custom SS plates on deck and as a backing plate.

Here is the solid fiberglass deck [i.e., no coring] after removing the old windlass:


And with the additional holes drilled to accommodate the new windlass:



Here is the new deck plate [ultimately glued down with 3M 4200UV]:


And for positioning reference, here is a photo showing the backing plate on top of the deck plate:
.

All of that is from 2014 [see: https://svdenalirosenc43.blogspot.co...windlass.html] and has proved very adequate.



In case this is of interest.

Cheers, Bill

[donradcliffe]

I'd use an allloy plate, minimum thickness 3/8", 1/2" better.

[Pepijn]

Thanks,

Increasing the height is not really an option. The winch is below a cover and already at its maximum height

[Bowdrie]

Originally Posted by Pepijn

Our previous windlass had the motor underneath (Lofrans Kobra) whereas the new Lofrans Tigress has the motor above deck.

Originally Posted by Pepijn

Increasing the height is not really an option. The winch is below a cover and already at its maximum height

So, the new windlass is going to be installed under the deck?
Or under some kind of hinged cover?

I would not cut a huge hole to patch, rather use cut-out pieces of G10 along with fiberglass to patch/clean up the deck to "like new/original" as though no holes had ever been cut.
Then start with a new mounting scheme.
Just adding holes and then covering-up the "Swiss cheese" of a deck with some kind of plate(s) above and/or below is not generally the best of ideas.

[Pepijn]

Yes, mounted in a deck recess under a hinged cover.
I will look into using G10. Thanks

[Spot]

Is the underside of the old winch recess accessible?

I would be tempted to laminate a layer of fiberglass on the underside, sealing all the unneeded holes so the rest of the work could be done from the outside. Then fill them with G10 or FR4 or scraps of cloth and resin. Then clean up the top really nice and cap over all the repairs with a thin lamination. Before the first underside lamination I would clean and prep the holes to be patched.

If the access to the underside is limited, it is possible to slide a patch panel through the big hole and epoxy it to the undersides using bungee cords to pull the patch tight to the underside of the deck until the resin is set. I just got done doing this twice to a small boat that needed backing plates replaced under the deck with no access from below.

[Pepijn]

Yes, it is fairly well accessible. So far I had been thinking along the same lines. Putting a piece of plywood covered with plypeel underneath and secured with a few bolts. Then cut a piece of plywood in the same contours as the old hole area (unfortunately I cannot get my hands on G10 overhere). Wet all areas and edges and then use epoxy with microfibres to fill the gaps. After hardening I remove the plywood underneath.

After all is done, faired and painted I am thinking of putting a 5mm stainless steel plate underneath and secure the windlass on top with through bolts and nuts.

[Pepijn]

Here is what I finally did. Sawed out a piece, prepared an old left over piece and filled it with West System epoxy, bonding and fairing.

Unfortunately, no picture of the fairing before primer and 2 layers of paint.

The work is time consuming but quite easy to do.