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I am doing major surgery, removing my existing anchor well. It is one of those shallow triangle shaped compartments that will fit a small danforth anchor. I wish to remove it completely and re-glass the deck flush to accommodate a new horizontal manual windlass(SL 555)/double anchor locker setup. My plan is to cut plywood the shape of the patch, apply 6-8 layers of fiberglass cloth with epoxy resin, then smash the patch up against the inside of hole, ovelapping as much as possible. Then I will continue to fill the hole from above with further layers of glass until it is flush with the exterior, then finish it to match the existing deck.

The windlass is the reason for so many layers of fiberglass as this specific area will inevitably suffer serious torque. I will be backing the windlass with a stainless steel plate that will cover new and old fiberglass, so it will hold even if the patch tears out.

All the books I have read have read say not to use more than 4 layers of fiberglass at once to keep from "cooking" the glass and causing delamination. What I cannot find is a procedure for using many layers that has cure times. What I am looking for would read:

Lay 4 layers of glass, wait six hours, lay 2 layers of glass, wait six hours, lay 2 layers of glass, wait six hours....etc....

I plan to use West System epoxy. Does anyone have experience with this many layers?
 

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okay what you need to read is most epoxy hardeners will give you a film thickness value of about a 1/4. so anything over a 1/4 will cure faster than the time it says, anything under will be less. you can also mix the hardeners to get a better cure rate for what you need, just make sure the ratios for the hardeners are the same. if you are talking about 70 degree temps you are fine using wests slow hardener for pretty much anything, at over say about 80 degrees stay away from the fast hardener in thick layups. now you also dont want to work with the epoxy in a tall skinny cup, mix it in a measured cup then dump it in to a paint pan. honestly do some experiments while doing the first lay ups, if it kicks too fast you can slow it down by putting the hardener in the fridge to cool it some before you mix.

as for time between layers, either wait till its real solid but still tacky or wait 24 hours. i have found on a normal 80 to 85 degree day you can get 4 layers or so of 7 oz glass in one day each layer being 5 layers of glass. you are going to want to use roving for the build up but its alot harder to get it to curve, and to saturate fully.
a trick you might want to do is to vac bag it, yes you can do this. once you get the patch in place, and each layer laid tape down a black trash bag over , with a garden hose sized hose under a corner, and duct tape that to a shop vac. this will suck it down pretty well and the sun will help cure the epoxy in about and hour, to a good point for the next layup. this will allow you to 6 layups if you work quick.

as for saturanting the glass, you need a table set up, covered with a trash bag, lay the glass out pour on some epoxy and spread it out with a soft squeegee, put the next layer on top do it again three times, then lay on one last layer with no resin work it in, then transfer the patch carefully

have fun
 

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Everything Scotty said plus a few thoughts:
1. I would not want to introduce plywood into the mix as it can rot. If you are covering the plywood with plastic and just using it as a temporary form that is OK.
2. Repairing the hole left in the deck by removing the hatch should be done by beveling the fiberglass back 8 to 1 or more.

So lets say you have a 12" hole and the glass is 1/4" thick. You will grind out a circle that is 16" on top and 12" at the bottom. The effect is if you had a very very big countersink bit.
The first piece of glass you drop in the hole is 16". It will drop in the center to hit the glass you put in from the bottom and be nearly even on the edges. Each successive layer is an inch smaller in diameter. If you can reproduce the layup with cloth, mat and roving that is even better. The boat was most likely built with polyester but you can do the repair with epoxy as it has better secondary bonding.
West system has a book and video. There are many details I left out that are critical, look it up.

Then use stainless steel backing plate like a giant washer.
If you think you need it you can glass in ribs underneath using a hose as a form.
 

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You really need to think this through a bit better. What weight cloth are you talking about? Is the plywood just used as a form temporarily or is it going to be a permanent part of the installation? Are getting rid of the anchor locker completely or making a deeper one—YOU WILL NEED AN ANCHOR LOCKER of some sort.

I am doing major surgery, removing my existing anchor well. It is one of those shallow triangle shaped compartments that will fit a small danforth anchor. I wish to remove it completely and re-glass the deck flush to accommodate a new horizontal manual windlass(SL 555)/double anchor locker setup. My plan is to cut plywood the shape of the patch, apply 6-8 layers of fiberglass cloth with epoxy resin, then smash the patch up against the inside of hole, ovelapping as much as possible. Then I will continue to fill the hole from above with further layers of glass until it is flush with the exterior, then finish it to match the existing deck.
If your plan is to make the deck flush, then you need to get cut away the old locker and then grind the glass on the underside of the deck to a 12:1 bevel and then lay a patch into that to get a strong repair. I would also recommend grinding the glass on the topside of the deck to a 12:1 bevel and glassing the hole over from both sides.

The windlass is the reason for so many layers of fiberglass as this specific area will inevitably suffer serious torque. I will be backing the windlass with a stainless steel plate that will cover new and old fiberglass, so it will hold even if the patch tears out.

All the books I have read have read say not to use more than 4 layers of fiberglass at once to keep from "cooking" the glass and causing delamination. What I cannot find is a procedure for using many layers that has cure times. What I am looking for would read:

Lay 4 layers of glass, wait six hours, lay 2 layers of glass, wait six hours, lay 2 layers of glass, wait six hours....etc....

I plan to use West System epoxy. Does anyone have experience with this many layers?
Given that you want to install an anchor windlass on this replaced section of deck, I would highly recommend you use a core material, like Divinycell foam in the repair, as it will be both lighter and stiffer than a solid fiberglass section and stronger , unless the fiberglass is very thick. Make a "hole" in the foam core so that the area under the windlass can be solid glass—both to prevent water from getting to the core and to provide compressive strength.

I wouldn't use a stainless steel backing plate, unless you plan on filling the space above the plate with thickened epoxy, so that the the plate doesn't create uneven stress on the deck.
 

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Discussion Starter #5
My idea is to make the glass so thick that it will not require coring or ribs. The glass I have is six ounce cloth. I have read that you cannot use mat with epoxy resin, has anyone done this?

I did plan on laying a new layer on top of the deck as well as this would add stability and eliminate the need for beveling any edges.

I am planning on using an oversized stainless backing plate that will be larger than the footprint of the windlass, thus distributing the load evenly. If I have enough plate, I thought of having it go out to the hull on both sides and bolt it there as well(where my bowsprit will attach and also need backing plates. Two birds, one bolt). I have a small rode locker at present in the tip of the boat that will probably need to be enlarged. I want an open locker on the port side for nylon rode-I have not yet decided how to locate it as far as in front, behind, or beside the windlass to maximize function while maintaining structural integrity. Also bear in mind that we do sleep in the V-berth with our heads in the bow. Suggestions?
 

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