Bowsprit rigging geometry

[wingssail]

Originally Posted by Cyrus Safdari

The idea is to get a light asymmetrical or gennaker flying without hassle of spinnaker pole etc..for singlehander. I'm totally redoing standing rigging,, already adding a removable inner stay and I'm installing windlass now. So it is time to make these decisions.

Indeed the bowsprit like any other spar should be calculated to do its job but being a non engineer im going to have to go with oversizing. I figure I can't reasonably fit anything larger anyway. The retractable spirits are 70mm aluminum extended 36 inches off the bow so that can provide a basis for comparison if someone could do the math.

Cedar - White Atlantic cedar if I can get it - has been used in spars along with fir and spruce for a very long time. Teak would be nicer but Heavier and I'm not sure I want more weight on the nose. There that Oregon cedar cypress too...

Honestly costing this out along with considerations of windlass location and anchoring issues... it may be more economical to go with one of the retractable pole options, rather than a permanent fixture. But they are OH SO UGLY and my foredeck is already crowded

Cyrus, This is an interesting engineering project, and, as you are finding, it is not without challenges and expense.

But I would question the need for a bowsprit on your boat to get light asymmetrical or gennaker flying without hassle of spinnaker pole etc.

For that purpose (as opposed to simply adding more area to the sailplan) your boat does not need a bowspirit. You have considerable overhang forward, so the hull itself acts to get the tack of the asymmetrical or gennaker into clear air. You only have to reach up a bit and those types of sails will fly easily.

Modern boats with plumb bows (or nearly plumb) have more need for a sprit to project the assym sail farther infront of the boat, both for balance and to get more clear air. It does improve the effectiveness of the assym sails which is demonstrated by the rating penalty the sprit carrys.

Most of those boat were designed to use sprits. Yours was not.

I would concentrate on optimizing the rig design you have. I am not sure the costs, of which there are many, would be worth any sailing efficiency you achieve.

[fourlyons]

Originally Posted by deCarabas

Sorry for hijacking this post but couldn't find another similar post. Can anyone tell me what this is for? Thanks in advance.

There are advantages to hauling the tack to weather, that's what this bowsprit does. Dashew put a bowsprit on his last sailboat that pivoted to weather. I thought his was a bit more elegant.

Sorry, don't know how to attach the photo from above that looks like a crossbow on the bow.

[deCarabas]

[wingssail]

Originally Posted by fourlyons

There are advantages to hauling the tack to weather, that's what this bowsprit does. Dashew put a bowsprit on his last sailboat that pivoted to weather. I thought his was a bit more elegant.

Sorry, don't know how to attach the photo from above that looks like a crossbow on the bow.

Being able to sail "deep", meaning going more downwind, is advantagous. It improves downwind VMG. Many modern boats achieve their best downwind VMG by jibing and reaching back and forth. But there is often a desire to go deeper, especially in heavier winds. More projected area in heavier winds can result in downwind speeds nearly as fast as the broad reaching speeds.

Hence the idea of a pivoting bowsprit or one with a "crossbow" tack attchment device. It allows more of the kite to be projected to windward.

My own boat does not accellerate when reaching like more modern boats do. I can never keep up with the boats which can plane on a reach. A sprit does not do much for me, I am hull speed limited. I need to sail deep with a lot of projected area.

But I can get that and achieve very good downwind VMG's if I can fly a symmetrical or assymetrical kite with a pole to rotate the tack back. Then I can get to my hull speed going almost dead down wind. If the wind is over 14 knots true this is really good for us.

These two photos show use of assymetrical kites without a sprit. The white one is tacked to the anchor roller inside the bow pulpit and the red one has been rotated with a pole back to work like a symmetrical spinnaker.

[fourlyons]

Originally Posted by wingssail

Being able to sail "deep", meaning going more downwind, is advantagous. It improves downwind VMG. Many modern boats achieve their best downwind VMG by jibing and reaching back and forth. But there is often a desire to go deeper, especially in heavier winds. More projected area in heavier winds can result in downwind speeds nearly as fast as the broad reaching speeds.

Hence the idea of a pivoting bowsprit or one with a "crossbow" tack attchment device. It allows more of the kite to be projected to windward.

My own boat does not accellerate when reaching like more modern boats do. I can never keep up with the boats which can plane on a reach. A sprit does not do much for me, I am hull speed limited. I need to sail deep with a lot of projected area.

But I can get that and achieve very good downwind VMG's if I can fly a symmetrical or assymetrical kite with a pole to rotate the tack back. Then I can get to my hull speed going almost dead down wind. If the wind is over 14 knots true this is really good for us.

These two photos show use of assymetrical kites without a sprit. The white one is tacked to the anchor roller inside the bow pulpit and the red one has been rotated with a pole back to work like a symmetrical spinnaker.

Wingssail,
if I understand what you're saying, a pivoting bowsprit pulls some of the spinnaker out from the main sails shadow, allowing a fast, light boat to be almost as fast through the water as it might be tacking downwind, but vmg is better because it's sailing deeper, ie straighter to the mark.

And that is preferred to poling out the spinnaker and getting it completely out of the mains shadow? Is that because these boats are fast enough to bring the wind forward enough that a sail poled out on the"wrong" side would collapse?

I presume a boat sailed this way can't actually sail ddw, or it can, but would be much slower because only the main is working and only in drag rather than lift mode?

[wingssail]

Originally Posted by fourlyons

Wingssail,
if I understand what you're saying, a pivoting bowsprit pulls some of the spinnaker out from the main sails shadow, allowing a fast, light boat to be almost as fast through the water as it might be tacking downwind, but vmg is better because it's sailing deeper, ie straighter to the mark.

[I]It will still be tacking downwind, just on deeper angles[/I]

And that is preferred to poling out the spinnaker and getting it completely out of the mains shadow? Is that because these boats are fast enough to bring the wind forward enough that a sail poled out on the"wrong" side would collapse?

Maybe not exactly. On those really fast boats you cannot keep the pole back so far. As the boat accelerates the wind goes forward and the pole goes forward too, until it is not much different than a sprit. Only the slower boats which don't get into planing mode can benefit with a pole pulled way back.

I presume a boat sailed this way can't actually sail ddw, or it can, but would be much slower because only the main is working and only in drag rather than lift mode?

In that case both the mainsail and the spinnaker are nearly in "drag" mode because the boat cannot sail DDW faster than the wind, actually few boats can. Those that do are reaching across the wind, bringing the apparent forward

The question related to the OP's query is, "will a sprit help a boat like a pearson 35?".

My point is that the help will be limited because of the hull speed limitations of that style of boat. Where it will benefit from additional projected area is while sailing really deep and then the sprit does not do much because it is on the centerline.

[fourlyons]

Thanks for the explanation Wingssail.
I don't know if it's true, but my impression is that not many of the newer semi planing boats bother with symmetrical spinnakers anymore, but they all seem to have a bowsprit, I'm guessing this is why.
So those of us on slower displacement boats who want to improve our broad reaching and downwind speeds might still do better with a symmetrical spinnaker on a pole?

[wingssail]

Originally Posted by fourlyons

Thanks for the explanation Wingssail.
I don't know if it's true, but my impression is that not many of the newer semi planing boats bother with symmetrical spinnakers anymore, but they all seem to have a bowsprit, I'm guessing this is why.

Also, it is much simpler from a boat handling, crew competency standpoint.

So those of us on slower displacement boats who want to improve our broad reaching and downwind speeds might still do better with a symmetrical spinnaker on a pole?

The news is not as bad as that. You can stick with a assym kite, but get a big one. Many cruising assymetrical spinnakers are woefully small. Then just get in the habit of jibing downwind. Finally, if you want the DDW capability, keep a regular spinnaker pole on the foredeck (not a whisker pole, they are not strong enough). If you have a tack line on your kite which can be let out, then rig an afterguy on the windward side, also to the tack of the kite, put the pole on that afterguy and while easing out the tack line pull the pole back with the after guy. This almost duplicates a symmetrical spinnaker. (see the red spinnaker in the photo above)

The thing is, in my view, it does not make sense to try to get the performance of a modern boat out of an older design. Each new gimmick, clever technique or piece of added rigging is going to bring diminishing returns at the cost of added complexity, and you won't use them that often anyhow. Keep it simple.

You are better off to maximize your basic sailing techniques and get the most out of your boat as it is, maybe good sails if you don't have them.

In the end you will get a lot of enjoyment from a well designed, well sailed, older boat. My friend sails the heck out of his stock Baba 30 in the local races and he does quite well. His Baba 30 will never be a Hanse 45 but he still loves it.

[fourlyons]

That is excellent advice that I am usually good at following, I just have to remind myself of it regularly.

[VChild]

You could also have a bowsprit fabricated with stainless steel. That is how my old wood one was replaced. It was fabricated from 1/4” wall thickness 316ss. Kept the original bow pulpit with bronze anchor rollers but replaced the old teak boards with new. The sprit has a custom receiver pedestal and chain drops for a Lighthouse 1501 windlass with dual chain gypsies. The old wood samson posts were also replaced using 3/4” thick 316ss plate. The curved shapes were cut with a water jet to retain some of the character of the old wooden posts that were hourglass shaped. The most time consuming part was buffing out all the stainless to a mirror finish. The stainless steel stock all started as a dull rough finish from the supplier. The bobstay is solid rod. It is 3/4” diameter round bar (316ss). Each end of the bobstay has the last 6 inches threaded. Clockwise at one end and counterclockwise at the other. This allows the bobstay length to be adjusted like a turnbuckle in order to balance with forestay tension.

[Searles]

It shifts the tack point of an assametrical head sail to clear air ⚓️⛵️