Double Anchor Roller that avoids Sprit Bobstay

My Olson 40 Euphoria will have a bowsprit usually rigged when the boat is outside of a marina, including when the boat is anchored.

The bowsprit requires a bobstay and whisker stays to resist vertical and horizontal loads from the pull of the tack of any roller furled screecher or asymmetric spinnaker rigged to the forward end of the bowsprit. Because of the essential bobstay, the whisker stays, and the bowsprit itself, each of the two anchors must be offset to the side so both the anchor and the anchor rode will not impinge on the bobstay, whiskers, or bowsprit as the anchor is dropped or retrieved.

Ian Farrier had a similar problem, and so came up with an idea he called the “bow wing.” His solution consists of a somewhat wing-like spar, like a Cal-20 mast section, mounted horizontally athwartship just below the deck a few feet back from the bow.

Of course, there is nothing new under the sun. Sailing ships with bowsprits supported by large numbers of stays are not new, and therefore this problem had been solved long ago using a “Cat Head” or “cathead” to hold each anchor away from the hull, aft of the bowsprit but inside the whisker stays. Nearly all ships had one cathead to port, and another to starboard, to hold each of the two anchors.

image.jpeg

 
Concept: use a G10 tube, G10 plates, and Delrin rollers

The G10 tubes available from McMaster-Carr come in a maximum length of 42”. The anchor width is 20”, so we want the roller to be centered 10” out. The width of the roller is 4”, so the outer edge of the roller is 12” out. The two plates to keep the roller in position -- one inboard and one outboard — are needed, and adds another 3/4” to the outboard length. Hence, the tube needs to extend 14” outboard of the hull on each side. So a total of 28” of the tube is outside the hull (14” on either side), allowing a 42” tube to have 14” within the hull.

The web site https://www.engineering.com/calculators/beams.htm was used to calculate the strength and deflection of the tube acting as a beam. The result that seems best requires a 3.25” OD tube with 1/8” wall thickness. This tube will support a 4000 lbs load before approaching the minimum strength of the tube (45000 PSI) with less than a third of an inch of deflection.This is the size Ian uses for his 39 foot trimarans.

The Delrin rollers are standard Lewmar replacement rollers.

 

Raz'r

Super Anarchist
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I like it. We don't have a platform, and are putting on a stubby sprit. What we're going to try, which isn't good for cruising but should be fine for occasional anchoring, will be a low-friction ring, with the rode through it, with 2 eye splices, one for the halyard to hold it off the deck, the other for a padeye on the deck. Then, we run a bridal off the anchor rode to hold it back from the sprit.  Worked well for an overnight in an exposed anchorage with 10-20 and rolling wind-waves.

 
I like it. We don't have a platform, and are putting on a stubby sprit. What we're going to try, which isn't good for cruising but should be fine for occasional anchoring, will be a low-friction ring, with the rode through it, with 2 eye splices, one for the halyard to hold it off the deck, the other for a padeye on the deck. Then, we run a bridal off the anchor rode to hold it back from the sprit.  Worked well for an overnight in an exposed anchorage with 10-20 and rolling wind-waves.
Interesting!

We have been just using moorings, but we want to go places without moorings. In particular, Santa Cruz Island, which often requires bow and stern anchoring.

On previous boats, the way I have been anchoring with bow and stern anchors is to still drop and raise the anchors from the bow, and use a boat hook to take the stern rode to a stern cleat. That keeps all rode away from the prop, and all the anchor handling activities in the same place (forward) so its easy to let out the stern rode while pulling in the bow rode (while anchoring) and easing the bow rode while pulling in the stern (while pulling up the stern anchor).

We will use the halyard winches as windlasses. We have an electric winch handle consisting of a Milwaukee battery powered angle drill, and a proper bit that fits in the top of a winch.

Everything is an experiment: we try things, and then improve.

I have a feeling that all dyneema rode will work. But to explore this concept without losing my anchor and then my boat if I am wrong, we are going to start with the following arrangement: Chain from anchor to near the halyard winches, and yellow dyneema for the rest of the rode, sized to fit in the self tailors on the winches. I will enclose the chain in dyneema. That way, I can monitor wear on the dyneema while still having the security of chain. Hopefully, I will see little chafe on the dyneema against the bottom, and I can then eliminate the chain. Or, keep the chain. We will see.

Why yellow rode? Because it floats! So seeing the rode is a good way of reducing the number of times the rode gets run over and cut.

 

yoyo

Anarchist
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Interesting approach to address anchor rollers.  Thanks for posting.   

I love how the sugar scoop turned out too.
I am curious .... what was the thought / plans behind adding the sugar scoop?

 
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El Borracho

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The clearance is tight only when fully up. We might need to do something, we will try in a couple of days.
Very nice solution to a vexing problem. Can you still mingle with other O-40 owners or are you ostracized as 'too cruisey'? :)

I spy the bobstay apparently going thru an athwartship tube. Right? What did you use as a tube? And what did you do to figure if the hull was tough enough at that spot? Pity to have a slot appear right there in a puff. I've got to do something similar on the SC50.

 
The boat is so beautiful, I don't get ostracized.

The bobstay does go through an athwartship tube. The tube is G10, purchased from that wonderful place McMaster-Carr (McMaster.com). Athwartship Hole drilled a bit oversize, then thickened epoxy.

The bow is solid glass there. Its about 6" thick solid glass. The back edge of the tube is inside the solid glass, so there is a little patch of glass to cover the tube completely on the inside of the hull. Its pretty narrow in there: I am sure the bows are similarly sharp on both O40 and SC50, and I would expect that a similar or greater amount of solid glass is at the bow of an SC50. I don't seem to have any pictures of the process, sorry.

 

El Borracho

Verified User
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2,636
Pacific Rim
The boat is so beautiful, I don't get ostracized.

The bobstay does go through an athwartship tube. The tube is G10, purchased from that wonderful place McMaster-Carr (McMaster.com). Athwartship Hole drilled a bit oversize, then thickened epoxy.

The bow is solid glass there. Its about 6" thick solid glass. The back edge of the tube is inside the solid glass, so there is a little patch of glass to cover the tube completely on the inside of the hull. Its pretty narrow in there: I am sure the bows are similarly sharp on both O40 and SC50, and I would expect that a similar or greater amount of solid glass is at the bow of an SC50. I don't seem to have any pictures of the process, sorry.
Yes, overwhelmed by beauty. What you have done is fabulous. Thx for the info. 

 




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