Compression support for winches

[GILow]

Today I removed what was left of the cockpit coamings. As I had suspected, what looked to be reasonable timber on the outside was hiding some extraordinary wood rot on the inside. The original timber post that was serving to provide compression support for the winches was basically soil. 38 years old according to the guy who originally owned the boat.

Anyway, I've got a plan to build very different coamings this time, an open box construction with nice big pockets to put "stuff" in. But I will need to provide some compression support for the winches.

I figured a stainless steel plate top and bottom and some stainless tube between the plates, maybe welded if necessary.

Any problems with this system that anyone is aware of? Any better ways of doing it.

I want to avoid the big block of timber if I can because it would fill much of the useful pocket space.

Matt

[Chotu]

Slight potential for crevice corrosion using stainless.

It seems different to make that from stainless. Why aren't you using fiberglass out of curiosity?

[MartinR]

There is very little compression load on winches, no reason to overdo it. The load is normally almost parallel with the coaming. Fiberglass without support should do it, if thick enough, alternatively plywood/epoxy. The reason they put this massive block of wood under, was because this was easiest.

[DeepFrz]

If you use plywood, drill the holes oversize and fill with epoxy/glass mixture and then drill to proper size leaving an epoxy annulus to support the compression loads.

[MartinR]

Originally Posted by DeepFrz

If you use plywood, drill the holes oversize and fill with epoxy/glass mixture and then drill to proper size leaving an epoxy annulus to support the compression loads.

Also, for reference, my coamings are made from1/4" fibreglass, and they support three 56 winches each. There is a backing "plate" made from 3/4" plywood under each winch though and oversized washers to distribute the forces.

[S/V Alchemy]

Originally Posted by MartinR

Also, for reference, my coamings are made from1/4" fibreglass, and they support three 56 winches each. There is a backing "plate" made from 3/4" plywood under each winch though and oversized washers to distribute the forces.

Recore with encapsulated plywood, drill and fill all the holes, and spread the side loads with either a second encapsulated backing plate, 1/4" aluminum plate with a bead of sealant all the way around, or a fibreglass backing plate, same treatment. Keep water out and you won't need to pull 'em off for five-10 years to check for ingress.


I have actually never heard of a vertical compression posts beneath a winch. So much of the load is shearing, not compressive. Another method is to make a plastic or (sealed) wood base for the winch, so that the coaming is in the center of the bolt length. I would think that's only necessary on really large sheet winches.

[GILow]

Right. Well I feel like an idiot.

The way it had been made suggested lots of compression strength was needed, though I couldn’t see why. The boat was so intelligently set up that I’ve learned to assume I am missing something important if I cannot see the reason for something being the way it is.

I was going to build the coamings from 19 or 21 mm marine ply and epoxy/glass. Shearing strength will be easy to obtain due to the nature of the construction.

Looks like I can skip the compression support.... though it feels odd.

[roverhi]

Glass encapsulated 18mm ply with fender washers on the winch bolts should be enough support to mount the winches. 1/4" fiberglass plate or aluminum would be a stronger backing plate if you are nervous with just fender washers.

[coopec43]

My winches sit on marine ply encased by fiberglass. But the round pads are proud of the deck and slightly smaller in diameter than the winches. (The deck is quite heavily glassed using CSM and WR)

I hope by doing that the pads will remain dry even in a heavy downpour.


Clive

[GILow]

Originally Posted by roverhi

Glass encapsulated 18mm ply with fender washers on the winch bolts should be enough support to mount the winches. 1/4" fiberglass plate or aluminum would be a stronger backing plate if you are nervous with just fender washers.

Thank you for the numbers. I was going to go a bit thicker than 18 but I suspect you are correct.

I’ve got the old backing plates from below the deck. I can recycle those if I am careful.

[GILow]

Originally Posted by coopec43

My winches sit on marine ply encased by fiberglass. But the round pads are proud of the deck and slightly smaller in diameter than the winches. (The deck is quite heavily glassed using CSM and WR)

I hope by doing that the pads will remain dry even in a heavy downpour.


Clive

Clive, are your winches mounted on the deck by the sound of it?

[coopec43]

Originally Posted by GILow

Clive, are your winches mounted on the deck by the sound of it?

Both sheet and halyard winches are on deck.

According to the sailmaker/rigging people in Perth (West Australia) "Everyone want to take the halyards back to the cockpit these days"


Clive

[Wotname]

Originally Posted by GILow

........

The way it had been made suggested lots of compression strength was needed, though I couldn’t see why. ..........

Looks like I can skip the compression support.... though it feels odd.

If the old post was mainly rotten, you have been going without any compression support for some time now...

[GILow]

Originally Posted by Wotname

If the old post was mainly rotten, you have been going without any compression support for some time now...

Seriously rotten. Although the bit under the main winch was sorta still ok.

[Snowpetrel]

Maybe some plywood 'bulkheads' or transverse supports would help prevent any racking of the box sections. But 18mm ply is solid stuff and I reckon it would be fine on it's own.

Maybe another way to make them would be fibreglass inside a mould. But ply/glass is likely cheaper and quicker.