Bow anchor box design 42 ft sail yacht

[jonasaberg]

I intend to install an Anchorlift Dolphin 1000 with 50 m 8mm chain in the bow of a 42 ft sailing yacht.
The yacht does not currently have an anchor box.

Design issues:
-What distance is needed from the underside of the deck to the top of the pile of chain to avoid handling problems?
-What is the minimum vertical distance above the waterline for the bottom of the anchorbox?
-What is a sensible diameter of the drain hole in the anchor box to minimize the amount of water getting pressed in while allowing water to be drained?
-When build the box, is it ok to build it in polyester, or should I fit a stainless steel supopport to minimize wear? How thick should I make the polyester laminate? I worry that the chain may wear the polyester in really bad weather and slide from side to side when tacking.
-Is it sensible to install a bilge pump in a pit in the bottom of the anchor box or not?

-Can someone point to a source of information about this design subject I can read?

I understand that the bottom of the box should be as high as possible to minimise water getting pressed into the box when sailing against the sea in high winds, but at the same time it makes sense to have the chain as low as possible.

/Jonas

[UNCIVILIZED]

Originally Posted by jonasaberg

I intend to install an Anchorlift Dolphin 1000 with 50 m 8mm chain in the bow of a 42 ft sailing yacht.
The yacht does not currently have an anchor box.

There's some good reference data in the Offshore Cruising Encyclopedia found free, here --> SetSail FPB » Free Books

Design issues:
-What distance is needed from the underside of the deck to the top of the pile of chain to avoid handling problems?

Bear with the non-metric measurements here, you can convert them yourself:
- 100' of 8mm chain takes up about 1 cubic foot of space when well stowed. However when chain falls from a hawse & stacks up on top of itself, the stack height is about 2.5x of the chain's best stowed volume.
There's more on this in the book above.



-What is the minimum vertical distance above the waterline for the bottom of the anchorbox?
-What is a sensible diameter of the drain hole in the anchor box to minimize the amount of water getting pressed in while allowing water to be drained?
-When build the box, is it ok to build it in polyester, or should I fit a stainless steel supopport to minimize wear? How thick should I make the polyester laminate? I worry that the chain may wear the polyester in really bad weather and slide from side to side when tacking.

The noise from a stainless liner in a chain locker would drive you insane in about 5 minutes. So me, I'd avoid it. Even Navy ships use teak "batter boards" on the insides of their chainlockers.

Just build the locker with a side that's relatively easy to remove for maintenance on the locker. And you probably want to use epoxy, not polyester, but it's your call. Epoxy will bond better later on any time you need to do repairs, or make modifications. And it sticks a lot better to wood, if wood will be used as part of the construction of the locker.
Also, just build in some extra thickness of fiberglass at the beginning, if you're concerned about it wearing from the chain moving around.


-Is it sensible to install a bilge pump in a pit in the bottom of the anchor box or not?
Depends on the design I suppose. But if you do put in a pump, use a macerator, like those used in marine heads, so that it chews up all the bits which come up with/on the chain. So that the drain hose attached to it stays clear.


-Can someone point to a source of information about this design subject I can read?

I understand that the bottom of the box should be as high as possible to minimise water getting pressed into the box when sailing against the sea in high winds, but at the same time it makes sense to have the chain as low as possible.

Much of the "how high" question is also dictated by where the locker is located. Meaning how far aft from the bow, & how often water ships into it via the hawsepipe. And whether or not you religiously seal it off for anything more than a short day sail.
/Jonas

Some of the above too, is dictated by the design of the bow, & the forward sections of the boat. Including where various bulkheads are located, & whether the boat has a flush foredeck, or one with a large cabin trunk. Since if there's a lot of flush area, & sufficient room belowdecks, the chainlocker can be several meters (or more) aft of the bow. Thus keeping it much drier by virtue of it's location, coupled with not having all of the weight of your ground tackle right up in the bow. Which again is covered in the text.

Also, do a search on here on windlass installations. Since how, & where you put it can also have a big impact on all of the above. And I'm a fan of mounting a vertical windlass just aft of the bulkhead that seperates the chain locker from the rest of the boat. That way it's motor is never in a wet, dank locker. And windlasses weigh a lot, so any distance you can move them further aft helps.

[jonasaberg]

Thanks, good advice!

[GordMay]

Generally chain rodes require a minimum perpendicular fall of at least 12".
This is measured from the centre of the gypsy for Horizontal windlass’, and from the bottom of the locker deck for a Vertical windlass - hence a Vertical Windlass requires more cockpit locker depth.

[sparrowhawk1]

Here's a photo of my anchor well. the biggest advantages of it are if I have to drop an anchor quickly the chain is all flaked out and ready to go , also my windlass is kept out of the weather and green water. there's a one and one half inch drain on the side with a through-hull and a small hole at the very front that's at the very bottom to get all the water out. There's enough room have 200 feet 5/8 inch line and 60 feet of 3/8 inch chain on the port side and about a hundred and fifty feet of chain on the starboard side( currently deployed). The only disadvantage is I have to flake the chain as it's coming off The Windlass but I will gladly do that to keep the stink and dirt out of my boat and have free running chain.

Also one thing to point out is I have two snubbers. One is just a short length of half-inch line rhat keeps the chain from rattling on the bow roller. I have light line that goes all the way to my cockpit cleat (about 30 feet) it goes through a roller so there's no possibility of chafe and it's very elastic for storm conditions. I the keep the lid closed except when I'm handling anchors.

[S/V Alchemy]

Sparrowhawk, your anchor well looks a lot like mine. To the OP: this may help you make some decisions: https://alchemy2009.blogspot.ca/2015/03/thinking-outside-anchor-locker.html

[sparrowhawk1]

Wow that's a lot of info on that link. One more thing to add to my post is that there is a hauspipe underneath my windlass on the chain side so if I ever went anywhere with very deep water I could have more stowed below deck. But I currently have it capped off, the plug is sealed with butyl rubber so even if the well was full of water it wouldn't go into my boat. Edit if that happened it would be the least of my worries because I think I'd have to be in the middle of a hurricane.

[zeehag]

my anchor sits on roller on sprit. i have a chain locker. works well on my boat

[Terra Nova]

Make the chain bin rather tall and skinny to avoid feeding problems.

[UNCIVILIZED]

Originally Posted by S/V Alchemy

Sparrowhawk, your anchor well looks a lot like mine. To the OP: this may help you make some decisions: https://alchemy2009.blogspot.ca/2015/03/thinking-outside-anchor-locker.html

Guys, I can't seem to make the above link work, got any tips?

[sparrowhawk1]

Works for me on a smartphone. See if this works.
https://alchemy2009.blogspot.ca/2015...ocker.html?m=1

[zeilersailor]

Originally Posted by UNCIVILIZED

Guys, I can't seem to make the above link work, got any tips?

Didn't work for me either

[UNCIVILIZED]

I can get to the main blog okay, but not the link to the anchor locker page that's recommended.

[bobmcd625]

Hei Jonas
Could you explain choice of an Anchorlift windlass? I am looking for a windlass on my 38' cutter rigged Downeaster 38. The Dolphin looks very good, but I am not familiar at all with that brand.
Your advice would be much appreciated.
Tusen takk!

[jonasaberg]

Thanks for all good info.

The anchorlift winch seemed like a good economical choice after looking around on a boat fair in Stockholm 8-9 years ago, and when I found two identical winches on a sale a year or two later I got both of them for stern and bow. Due to a renovation project, I have not mounted them, but now is the time!
I have attached a pdf with my latest idea for the installation. I appreciate all input, views and suggestions.

Currently, there is no deck hatch. The bow storage space is accessible from inside the boat through a wooden bulkhead with a 1.5*1.5ft opening.

My thoughts are:
-I want a hatch on deck to access the bow space and anchor box
-I don't want water in the box to be able to get into the boat through the bulkhead
-I don't want the chain to be able to escape in an extreme condition if a wave turns the boat over. So, a separate compartment for the chain, and the rest of the space for ropes, a ladder, fenders etc
-In rough weather I have read that water can get pressed into the anchor box and almost fill it. The water pressure into the box when the drain is under the waterline is greater than its ability to drain water. So, keep the chain box small!
-A separate small, dry enclosure for the electric motor to extend its life.

So, I want:
-to seal of the bulkhead
-a deck hatch big enough to climb down with a hatch seal to keep the space essentially dry. Probably a small bilge pump since the space goes below the waterline.
-the deck hatch deck size requirement make me consider a deck block to place the winch off the center line
-A separate chain box under the winch. The bottom of this should be 4-6" above the waterline.
- ~3 ft of space from deck to bottom of chain box
-A side hatch from the bow storage space into the chain box to make it accessible to clear up jams, cleaning etc.

Is it safe/strong enough to use polyester to build the internal bulkhead and chain box structures, and epoxy for the deck hatch?

Your thoughts?