Sprit boom length past mast?

[Dan St Gean]

I'm building a sprit boomed leg o mutton and need to know how much sprit needs to project past the mast to ensure adequate leverage for the snotter to do it's work.

Is a foot enough?

Dan

[Thad]

I would think that good and plenty.

[N. Scheuer]

That should do it nicely, Dan.

As owner of three sprit-rigged sailboats, I can say that it depends mostly upon the snotter hardware. You just need sufficient length for blocks to not "bottom out". Our Dovekie had a single block on the mast, so the sprit only had to be long enough for the snotter knot to stay ahead of that. Our Melon Seed Skiff has no blocks for the snotter, so even shorter is OK. Our Shearwater yawl has two blocks on the snotter, so we have about 14" of sprit ahead of the mast, and the blocks are just about touching. I'll be lengthening the sprit effectively by shortening the hardware at the clew, but not too much due to clearance needed for our jib to tack.

Moby Nick

[Dan St Gean]

Thanks so much!

Dan

[Bill Perkins]

It always seems that the various sprits damage sail shape less on the off tack (sprit to leeward )than one would expect .I have a theory that a generous length of sprit and snotter forward of the mast helps in this .

As the sprit bends under a press of sail the distance between it's ends becomes less .If the sprit and snotter have been held to their minimum possible length this shortening is going to produce the maximum cut into the airfoil of the sail .If there's a fair bit of snotter forward of the mast the bending of the sprit will slacken it , allowing the sail to push the sprit a bit more out and clear ,so there's less distortion of the sails shape .

I may be off on this . I sail small boats and have never been able to actually see the leeward side of the sail ! I do see that allot of old sprit rigs have more sprit forward of the mast than would be required just for the operation of the snotter .

[ 01-21-2005, 01:36 PM: Message edited by: Bill Perkins ]

[N. Scheuer]

Interesting point, Bill.

While both the spruce sprit in our Dovekie and the extruded aluminum sprits in our Shearwater are uch too stiff to bend under a press of sail, that is not to say that you point is invalid.

It may be taht a slightly longer sprit and snotter can be "pushed away" from the mast easier than shorter parts, thereby disturbing sail shape less.

Or, it may just be that sails are such an enefficvient way to move a boat that ssail shape doesn't matter as much as we'd like to think it does. Look at Chinese Junks. While some people claim they sail well, it's plain that their sails appear terrible.

Moby Nick

[ChuckG]

What about brailing? When the sprit is rigged nice and taut on my 14 foot whitehall, the sprit end isn't much past the mast. In order to brail the sail up, I need to slack off the snotter, so I've rigged a long tail on the snotter back to the helm. This is a pain in the patoot. I'm thinking a longer sprit, with a longer snotter perhaps rigged higher on the mast, will solve this problem.

I did some experimenting that seems to validate this, but I wasn't totally convinced just by playing with spars in the driveway.

cg

[J. Dillon]

Other things to consider.

Keeping the sprit short will also help in keeping the jib from fouling the sprit when tacking. Shown it's a bit too long as it sometimes fouled the jib.

I have since shortened it.

http://www.imagestation.com/picture/sraid155/p2488b035d444f8d338d9377c0c51d20f/f561591a.jpg

. http://www.imagestation.com/picture/sraid155/p51b10115c660175b475e1f3a614c2faf/f561591e.jpg

In this view the main is lowered when reefed. I sometimens sail with the reef in and jib up. When sailing as above (text) the jib does foul the sprit but the addition of a tennis ball on the end of the sprit sometimes helps prevent fouling.

JD

[Brian Palmer]

I keep the jib from fouling the end of our sprit by letting the wind back the jib and push it over pas tthe end of the sprit well before sheeting. Our jib overlaps the main quite a bit, by the way.

If you try to sheet the jib over, it will almost always foul the end of the sprit. Our diagonal sprit is maybe about a foot past the end of the mast.

-- brian

[Lazy Jack]

Brian Palmer is right on the money, I have to ease the jib sheet when coming about with the gunning dory after it begins to fill on the opposite tack, then it slips easily over the end of the sprit. The overlap on my sprit is about 10 inches or so and the block placement gives me plenty of leverage

http://www.imagestation.com/picture/sraid152/p65db3750b435149ae1704e9b1ed1696b/f5b7d321.jpg