Bowsprit design - SailNet Community
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post #1 of 6 Old 07-25-2017 Thread Starter
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Bowsprit design

I was looking at some boats at the dock the other day, actually, I was taking the students on a tour of the boats to get them used to look at design differences.

When looking at boats with bowsprits I got to thinking, why?

I came up with two reasons.

1. A boat like the Catalina 30 has two models. They can save money but use the same hull and have a higher-performance model with a taller mast so the jib has to be bigger to compensate so they put on a sprit.

2. A designer wants to move the mast forward a touch to make accommodations below work out better so to balance the boat the jib has to be a little more forward with a sprit.
But in this case why not just make the boat a touch longer?

It seems like there are so many downsides to sprit I'm a little suspicious that maybe the boat is built and it is found after the fact that it needs a little more jib to balance so they just tack on a sprit.

I'm sure their is a historical answer too. A foot or two of sprit is a lot cheaper than a foot or two of boat. The problem of having to pay for dockage including the sprit is probably a rather modern problem.

So educate me please on the design issues of the bowsprit.

The lesson from the Icarus story is not about human failing.
It is a lesson about the limitations of wax as an adhesive.
If you have an engineering problem solve it.
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post #2 of 6 Old 07-26-2017
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Re: Bowsprit design

1. used as an advantage in ramming contests, no need to damage your hull while damaging and sinking someone else. Great as protective-intimidation device when 'the dreaded charterers' are dragging down on you.

2. good way to pay a 43-44ft. docking charge for a 37 ft. boat (not including the extra charge for a dinghy on davits).

3. Birds usually prefer to build their nests on anchors hung on bowsprits rather than elsewhere during nesting season. Less boat mess.

4. gives one a free and uncontested rental space for a floating dinghy when one is docked alongside of a pay-by-the-inch (but valet and concierge service is included) transient dock

5. No need to have a passerelle ... but you do sometimes get funny looks when Med-Mooring is needed. In such 'reverse Med-Moor' bow-in-first episodes ..... a good conversation starter with new neighbors.

6. having a bobstay and two whisker stays increases the joy of periodic rig tuning.

7. No need for a super-expensive retractable bow mounted carbon fiber spinnaker pole. (Actually, I couldnt pay for a carbon retracto-pole due to past and innumerous expense/costs for all those extra 7 ft. dock charges).

8. Better place to watch dolphins, etc. under the bow.

9. Helm balance - especially with (true) cutter rigs with the mast ON midships and with huge mainsails ..... the extra sq. footage helps to keep such crab-crushers moving along spiritedly and with a quite neutral helm.

Last edited by RichH; 07-26-2017 at 12:11 AM.
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post #3 of 6 Old 07-26-2017
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Re: Bowsprit design

I sail an internally ballasted, Presto 36 centerboarder. Subsequently I have a low aspect ketch rig. To increase sail area the designer of the boat not only gave the boat overhangs but also a bowsprit. So, I have 31ft.LWL, 36ft.LOD and 39ft.LOA.
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post #4 of 6 Old 07-26-2017
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Re: Bowsprit design

Quote:
Originally Posted by davidpm View Post
I was looking at some boats at the dock the other day, actually, I was taking the students on a tour of the boats to get them used to look at design differences.

When looking at boats with bowsprits I got to thinking, why?

I came up with two reasons.

1. A boat like the Catalina 30 has two models. They can save money but use the same hull and have a higher-performance model with a taller mast so the jib has to be bigger to compensate so they put on a sprit.

They could have also just used a higher aspect jib, which has some drag advantages. My guess is they were trying to shoehorn as much sail area as possible.

2. A designer wants to move the mast forward a touch to make accommodations below work out better so to balance the boat the jib has to be a little more forward with a sprit. Moving the mast forward would move the sailplane forward. If anything in this case you would want a smaller jib to rebalance of the Coe of the keel. If anything moving the mast aft would justify a bowsprit to add forward sail area.

But in this case why not just make the boat a touch longer? Adding a few feet to the length of the boat adds massively to the cost, adding a bowsprit does not.


It seems like there are so many downsides to sprit I'm a little suspicious that maybe the boat is built and it is found after the fact that it needs a little more jib to balance so they just tack on a sprit.

I'm sure their is a historical answer too. A foot or two of sprit is a lot cheaper than a foot or two of boat. The problem of having to pay for dockage including the sprit is probably a rather modern problem.

So educate me please on the design issues of the bowsprit.
There are a lot of good reason...

1) Allow enough J room for a cutter rig

2) Balance the sail plan

3) provide space for anchors

4) Fly an asymmetric spinnaker

5) Allow for a longer J, allowing a larger non-penalty spinnaker

6) Looks

7) It makes it easier to design the mast because of a wider shroud angke


You aree correct that just making the boat longer would generally be a faster option, but that is always true. Any boat could have been made faster and better sailing by just adding length to the hull. Worse this is always true, take any boat and add 15% to her length and she will be faster.

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post #5 of 6 Old 07-26-2017
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Re: Bowsprit design

In boats with internal ballast or no ballast or low aspect keels, a low aspect rig allows one to maximise sail area while lowering the centre of effort. The lower centre of effort allows maximum drive while keeping heeling moment under control.

Sometimes you'll see bow sprits on boats with multiple masts (schooners, ketches, yawls) and lower aspect sails (gaffs, lugs, etc.). The combination of bow sprits, multiple masts and low aspect sails together all offer the advantage of maximising sail area while keeping the centre of effort as low as possible, thus keeping the boat on it's feet.

Improving balance is also a factor, both at the design stage, and after. For example, the Mark 1 model of my former boat, the Fantasia 35, was often retrofitted with a bow sprit to correct excessive weather helm.
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Last edited by Arcb; 07-26-2017 at 10:06 AM.
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post #6 of 6 Old 07-26-2017
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Re: Bowsprit design

Unless you have a decent 'sprit (Thane is 12') you are forever excluded from precipitating in bow net parties .Friggin in the riggin is optional but much enhanced out over the water. I have noticed that millenniums don't seem to be bright enough to hang on to their I phones while venturing 4th.
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