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Old 20-02-2010, 04:02   #1
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Bow Roller Construction

Hi guys, I am in the process of refitting an IOR 50 to go cruising across the pacific. Being an ex racer she dosent have much in the way of cruising amenities and no provision for ground tackle apart from hauling the anchor up from below and tossing it over the side.

I have to admit that i didnt find this forum untill after id already settled on a design and begun fabrication otherwise i might have cast around for opinion.. I struggled to find good information about the loads involved and details for the actual roller construction so in the end i might have over built it slightly. However i wanted this to be something we could have confidence in as ultimately the whole boat might be depending on it.

Complicating the design is the fact that the furling unit sits very close to the deck and the deck itself falls away at an angle from about 18" from the bow. This meant the distance between the roller and its fixing to the deck would be quite long.

To simplify construction i used two L shaped alloy extrusions (the boat is alloy) in 1/2" which were trimmed and joined along one edge to form a U shape approx 41 x 4 x 6". The roller itself is machined from nylon with a profile that will allow a Rocna 33 to sit against it on the smallest diameter but will still roll 12mm chain over a 6" diameter. The roller turns on a stainless axle 15mm in diameter which sits directly in the alloy extrusions.

Here are some pics, comments are welcome but also i hope this will be a data point for anyone else who needs to have something custom fabricated. As mentioned, i think it is perhaps slightly overbuilt and i am thinking of adding some lightening holes as its bloody heavy!
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Old 20-02-2010, 05:13   #2
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Nice.
Sometimes its helpful to have a plate or round stock or something across the top of the assembly near the working end...this is to prevent the rode from coming out of the slot if you get a hard side pull.
The challenge may be having it high enough so the shank of the anchor doesn't foul it.
I have the same anchor and the shank is pretty darn thick right over the roller.
You can see on mine that I'll need to modify the plate across the top to get the shank to settle down properly....the anchor isn't pulled in all the way so its not quite as bad as it seem.
It would sure be nice to see some pictures of you boat.
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Old 20-02-2010, 05:38   #3
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Really nice piece,
How much of the assembly is actually cantilevered from the forward-most fastenings.
50 ft of boat shearing about in a blow exerts tremendous side loads on the end point.
I twisted 3/8" stainless thru about 20 degrees vertical axis with 13 tons of boat in hurricane strength, with 5" of cantilever.
Are you going to flare the lead-in endplates so that the chain doesn't bind?
Pictures of the boat, please.
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Old 20-02-2010, 08:15   #4
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The fabrication extends obliquely to clear the furler and is cantilevered approx 15". Im attaching a pic which shows the piece sitting over full scale drawings of the bow.

This cantilevered aspect of the design is what prompted me to go with 1/2" alloy - seems im not over the top with this if 3/8" steel bends over a fulcrum of 5".

I will dig up a couple more pics of the boat and bow, the two 'ears' sticking up at the end of the roller are for a steel rod to hold the anchor in place and also to stop the road jumping out. I havent yet drilled here cause i want to get the anchor in place first to make sure it fits.

Not sure how im going to flare the end plates now they are stuck on - i can grind them to a rounder profile??
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Old 20-02-2010, 08:23   #5
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boat pics

Here are a couple of pics - one showing detail of the bow and the other a bit more of the boat. Thanks for the comments on the bow roller and the compliments as well, its satisfying seeing something materialise from ideas and take form. Ive only just discovered CAD and in the future this will help me a lot im sure. Up till now i struggled to see how an idea would work out untill it was built.
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Old 20-02-2010, 08:50   #6
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Here's how I solved the problem on my much smaller boat. It had an aluminum bow casting originally. A friend copied the bow casting out of boxed stainless and incorporated the roller into it. My furler is also quite close to the deck, I've had the roller on he boat for 10 years now and I'm very happy with it.
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Old 20-02-2010, 13:00   #7
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Good idea, & nice execution Drumroll30; but Id substitute a cleat for the fairlead.
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Old 20-02-2010, 14:16   #8
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WKD928, that's a nice looking boat and a good beginning to the anchor roller project.

1/2" aluminum is definitely not too big for that job, and yes to rounding the cheeks as best you can.

I'd also try to engineer some way to tie the forward end back to the bow somehow... would stiffen it a lot... even if you welded on an L-shaped piece underneath at the correct angle to let you thru bolt to the side of the hull right up near the deck, just back from the bow.

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Old 20-02-2010, 19:20   #9
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Make it super strong and make sure there is a bate that prevents the chain/line from jumping off the roller.

b.
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Old 21-02-2010, 04:35   #10
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weight reduction

I got bored this morning... well that and i wasnt happy with the weight of the thing so i thought i would take some material out of it. I started out drawing several large circles down the sides that i thought would meaningfully reduce the weight. I then spent some time considering the torsion and other stresses and the size and number of circles decreased. In retrospect i should have left it alone but the holes make it look lighter so psychologically im happier with it!

Bob, good idea about connecting the end to the bow - definitely the thing to do. Im still not exactly sure where it will sit taking into consideration the lead to the windlass (yet to be fitted) as well as the existing pulpit and padeyes.
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Old 27-02-2010, 10:17   #11
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powder coated

Pics of the finished item. I did grind some material away from around the front where the chain will come back to the roller - but maybe not as much as i should have, time will tell. I think the idea of tying in the front to the bow will be a key item to complete once ive actually located the main piece.
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Old 27-02-2010, 10:42   #12
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Looks pretty nice!
I would have added some flare to the cheeks you welded on and I'd recommend adding a removable pin over the top of the roller to prevent the rode from jumping off if you're caught anchored in rough water.
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