Sprit Sail Wrinkles

Builder's Forum
1

Let me preface this my saying that I have zero experience sailing a sprit rigged boat of any type. 

My observation: Most pictures I see of sprit sails show the type of wrinkles that, according to my current limited understanding, indicate an improper sail shape, either in the build of the sail, or in the trimming of the sail.

My question: Is my understanding correct? Or, is this just the nature of sprit sails, and it doesn't matter so much?  I've noticed this regardless of whether there is a boom or not.  Often, while looking at the pictures,  I imagine that loosening the snotter a little, and pulling the down-haul tighter would help.  Sometimes, I think that a boom-vang is what is needed.  

I sail the Jimmy Skiff with the three-sided leg-o-mutton sail with a sprit-boom, and I love it for its simplicity and reasonably good performance.  I am just trying to get educated on the diversity of other sail plans.

Thanks - Ron Paro 

2

It matters. If you are talking about a boomless spritsail two things are important. One is the upward thrust of the sprit. The sail hangs from the sprit like a curtain. If the sprit is not extended far enough you'll get wrinkles. The snotter end of the sprit should t stick out a bit forward of the snotter  so you have some leverage when you pull down on the downhaul. Next the sheeting angle must be correct. Without a boom the sheet is all you have to control the sail. If the angle from the clew to the traverler isn't right you get wrinkles. My traveler is just rope tied across the transom. I can make it longer or shorter to a keep things adjusted. Once I'm out on the water all my intitial adjustments go to hell so about fifteen minutes into the sail I stop and hoist the sprit a little higher and pull down on the clew if the lashing are climbing the mast. If you have a boom the adjustments are the same as any marconi and the sheeting angle isn't so important.

 

 

3

Ron,

You're absolutely right, most sprits, especially boomless ones, are sailed improperly adjusted. The anonymous respondent gave an excellent explanation to which I'd like to add the following:

First, as a bit of trivia, I've heard rope travellers referred to as sheet horses. How's that for a salty, evocative name?

Second, according to Phil Bolger, the correct sheeting angle is fairly dynamic. When sailing with the sheet pulled tight (close-hauled), the sheeting point should be further aft and lower than when sailing with the sheet let out (started). 

Third, when close-hauled the sheeting point should be on a line 10 degrees to one side of the mast. With the sheet started, that angle should increase for correct setting (again, according to Bolger). However, that usually puts the correct sheeting point out over the water.

So, the sheet horse should be continuously adjustable. Maybe some kind of arrangement with a block and cam cleat would work. Even so, without outriggers, you'll never get perfection (which is why you'll see the wrinkles so many times).

Finally, many people just don't have the patience to learn how to get the adjustments right, so they add a boom which keeps them from needing to worry about the sheeting angle at all. But it's more expense, more weight, something to hit you in the head when tacking and something for the boat to trip over when heeled.

Laszlo

103 Sailing Rigs "Straight Talk" by Phil Bolger, published by Phil Bolger & Friends, Inc. 1998

 

4

If you need any further guidance in this, check out your local Optimist dinghy fleet. Those kids know how to get a sprit sail trimmed right ! Especially the hotshots.

Most, if not all, have a 2 part purchase for the snotter. That helps getting enough tension .

5

Thanks for the responses! I'll check out Bolger's book, and in the spring I'll look for the local Opti fleet. 

In the meantime, I'll attempt to be more specific with my questions.  In the clc photo below, the skerry is blasting along, but there are a few wrinkles near the luft, diagonal to the sprit.  To me, this suggests more snotter tension is in order to remove the wrinkles and optimize sail trim. 

skerry

In the picure of the Skerry from Arwen Marine, the wrinkles are parallel with the sprit.  I take this to indicate that the snotter is too tight, and there may not be enough luft tension.

Arwen Skerry

Here are some Optimist prams, and it does look the the leading boats do indeed have better trim than the trailing boats.

opti racing

I often think that the optimal sprit rig would include a sprit boom similar to the Jimmy Skiff's as a self-vanging boom.  I have seen this on a few sail plans, but never in person.

Ron Paro