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Old 28-11-2018, 13:29   #16
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Re: Compression support for winches

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Originally Posted by Snowpetrel View Post
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.


Given my current situation, cheaper and quicker has a certain appeal.
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Old 28-11-2018, 13:49   #17
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Re: Compression support for winches

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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
What size are the winches?
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Old 28-11-2018, 14:11   #18
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Re: Compression support for winches

GILow
I built the coamings on my project using Coosa board. Specialized Structural Panels - Coosa Composites

Their blue water 20.
Great stuf to work with. Comes in sheets like plywood. More $ than good marine ply, but it doesn’t take much and there’s no rot issue.

I first made plywood templates and once I had the shape I likes used them as patterns to rout out the coosa bd. The sides and Bulkheads are one layer of 1/2”. The top is two layers of 1/2” and the aft end is 4 layers 1/2”. I used 2 layers 1708 and epoxy for the insides and added 3/8” fiberglass sheet at two areas for winch backing prior to the 1708.

Once the inside was done I flipped them over and bonded them to the deck with fillets and two layers 1708 which was bedded in the rebates of the deck.

I consulted with a pro boatbuilder who supplied me with the material schedule.
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Old 28-11-2018, 14:32   #19
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Re: Compression support for winches

Here’s a few more. The guy I consulted recommended peelply. GREAT stuff!
I was also able to access the insides of the coaming after install to apply 1” radius structural fillets and in the area with storage access 1708 tabbing as well.
Seems pretty skookum.

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Old 30-11-2018, 12:50   #20
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Re: Compression support for winches

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Here’s a few more. The guy I consulted recommended peelply. GREAT stuff!

I was also able to access the insides of the coaming after install to apply 1” radius structural fillets and in the area with storage access 1708 tabbing as well.

Seems pretty skookum.

Great photos of the construction, thank you. Very reassuring because that’s kind of how I was thinking of making mine, with the exception that they’d be open on the inside of the cockpit.

As an aside, that’s a very interesting looking boat you are building. Has a slightly Hartley feel to it from the photos. Can you tell us more?

Matt
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Old 30-11-2018, 12:52   #21
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Re: Compression support for winches

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What size are the winches?

Ummm, not sure the size except to say “waaaay too big”. Seriously oversized for the job. They are the winches for the yankee on a conservatively rigged 42 footer so that’s not a lot of strain. There’s a smaller pair for the staysail. The main winches are the sort of thing you’d expect to see on a 50 footer.
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Old 30-11-2018, 13:58   #22
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Re: Compression support for winches

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Originally Posted by GILow View Post
Great photos of the construction, thank you. Very reassuring because that’s kind of how I was thinking of making mine, with the exception that they’d be open on the inside of the cockpit.

As an aside, that’s a very interesting looking boat you are building. Has a slightly Hartley feel to it from the photos. Can you tell us more?

Matt
The boat is a Cape George 38. Built in Port Townsend, WA. Many are yard finished and works of art. Many are owner finished and quality varies...I’m doing my best!
Cape George Cutters § Cape George 38' Photos § Cecil Lange / William Atkin / traditional full keel sailboat

http://www.cruisersforum.com/forums/...1&d=1543614455
The first pic is a Cape George 45 just launched a month ago. The next is a 38 I saw in the yard in Port Townsend.
There are openings in the coamings. Glassed over and not cut out yet in the photo.
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Old 30-11-2018, 14:02   #23
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Re: Compression support for winches

Ah OK. When building the winch mounts for my boat I estimated the maximum load based on the winch gearing. In my case it was 2600kg, allowing for 50kg effort on the winch handle. The winches are 52's.

The plywood or coosa board you've mentioned would be adequate. The coosa is very good, widely used for transoms in outboard powered boats now, and it'll never rot.

I doubled up, building a raised plinth for the winches to sit on, which spreads the load further and helps lead the sheets nice and low on the winch drum. I basically never get overruns.

I've used 8mm aluminium backing plates, quite a bit bigger than the winch bases. Again, spreading the load, which is pretty much what working with composites is all about.
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Old 01-12-2018, 01:23   #24
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Re: Compression support for winches

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Ah OK. When building the winch mounts for my boat I estimated the maximum load based on the winch gearing. In my case it was 2600kg, allowing for 50kg effort on the winch handle. The winches are 52's.

The plywood or coosa board you've mentioned would be adequate. The coosa is very good, widely used for transoms in outboard powered boats now, and it'll never rot.

I doubled up, building a raised plinth for the winches to sit on, which spreads the load further and helps lead the sheets nice and low on the winch drum. I basically never get overruns.

I've used 8mm aluminium backing plates, quite a bit bigger than the winch bases. Again, spreading the load, which is pretty much what working with composites is all about.


Thanks 44CC. Reassuring numbers there. And a good reminder of how to calculate the load.

Also a REALLY good point about avoiding winch overruns which are seriously bad thing in my books.

I have heard a lot of good stuff about the coosa board but I think I’ll stick with the marine ply simply because I am familiar with it. A bit of a Luddite approach I know, but learning a new material with such a complex project probably would not end well.
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