self tending jib

[merlinron]

sorry guys,i tried the search engine, but it's not working. my small mind needs more answers! can any jib be made self tending? i have seen the curved aluminum boomkins( or is it a club?)and i understand why they are anchored about a third of the jib's foot aft towards tack. i am wondering if one could make one out of wood, laminated for the curved section and birds mouth style to get it up to the tack. would the system work if just loose footed and the boomkin/club was simply straight going right to the tack from the deck? i realize the boomkin also keeps the jib from hiking up, but is it paramount to have a certain amount to the jib's foot attatched to the spar, just because it is self tending?

[dredbob]

Not any jib can be made self tending. It must be a non-overlapping 'working jib', ie., it must set entirely forward of the mast.

I can come up with more or less five variations on the self tacking jib.

(1) Jib with a curved track or traveller on the deck below it. This does not require a club or boom and is not very common. The curve of the track must be the precise radius needed to maintain the proper sheet tension.

(2) Jib with a club attached to the aft third or so of the foot. The club may be sheeted to a straight traveller such as on the Chesapeake Bay Skipjacks, or to a variety of single or multiple point purchase arrangements.

(3) Jib on a full length boom pivoted at the stay, usually the jib is attached to the boom for the complete length. Sheeting as 2.

(4) Jib on a boom that is pivoted to the deck or the bowsprit somewhere aft of the stay. This is usually attached only at the clew. Sheeting same as 2. There is a modern higher tech variation on this one in which the boom is fastened to the deck in some fashion such that it can only pivot horizontally, but not lift, keeping the clew from lifting off the wind. Sheeting this is easier, as the sheeting arrangement does not have to pull down as much. I've seen this on Island Packet yachts.

(5) Jib with a wishbone boom or a curved sprit boom or batten. This also prevents the clew from lifting off the wind. Sheeting as above.

With variations 3-5, there must be some provision for the sail to be able to move aft as it comes down, or for the boom to move forward, or for the clew to release from the boom.

Don Street's book(s) _The Ocean Sailing Yacht_ (I and II) cover this in reasonable detail.

---
Bob

[Roger Cumming]

For a jib to be self-tending it must have a club. The club limits the size of the jib as the club must clear the mast when tacking. There are several ways to mount the forward end of the club - on a deck swivel fitting, on a fitting attached to the forestay or the best way: on a car on a short length of track which permits the draft of the sail to be adjusted by moving the car forward or back.

Club-footed jibs are nice for singlehanding but tend to make you lazy because changing jibs requires tying off or removing the club when going to a larger headsail. Consequently one tends to keep going with the small jib when a larger one is indicated. The other disadvantage is having the club jumping around on the foredeck when trying to get the anchor down. The self-tending quality does make sailing singlehanded through a crowded anchorage look easy and it is. LF Herreshoff drew jibs with short clubs, shorter than the length of the foot of the jib and without any forward fitting - the club was just hung from the sail. I have no idea how effective they were.

[John Bell]

The original post sounds like he is describing the Hoyt jib-boom. See http://www.forespar.com/onlineCatalo...omSystem.shtml for an example.

I'm sure one like it could be fabricated by the ambitious home-builder. The engineering will need some skill however.

[Lucky Luke]

Self "tending" jib?
...well, good idea!

[essaunders]

(Luke's post is working now...at least from my computer)

[ 09-07-2005, 07:28 AM: Message edited by: essaunders ]

[Ian McColgin]

dredbob gives a good summary.

Option (1) we call solent sheeting. The track curve is very fussy and frankly, since it's the reverse of the deck camber (ends higher than middle) it's ugly.

(2) is usually more for convenience in the way the sail was made and for making it easily reefed - on oyster dredges the sail's horsepower had to be exactly matched to the bottom and unlike almost all other sail boats, the forebears of the skipjacks were meant to be operable at less than full power. It's not very good for self-tending.

(3) is something you'll see but gives a poorly setting sail because the geometry prevents the foot from filling as you slack the sheet bearing off.

(4) is the classic. I think the pivot should be less than 1/8 foot length abaft the tack but I've seen boats where it's almost 1/4.

Best sheeting in (4) is to have a track or horse so the deck end of the sheet can go side to side and the sheet serves to flatten the sail on the wind. The working end of the sheet needs to be led forward along the club to maybe 1/3 back from the tack and then down to a deck block and thence back to the cockpit.

Second best is to have double-ended sheeting with block near or on each rail. A quick vector analysis will show you that the effective net sheet pull is from the center of the boat but very much lower than deck level and the sail will be flattened nicely on the wind.

Only if you have lost of depth, like it's an open boat and you can plant the sheet block right on the inner keel, does it make sense to sheet (4) from the center.

(5) is my personal favorite. There's an outfit called Camber Spar that makes a nice unit. The sail must be purpose built as the curved spar lives in a sleeve in the sail and the sail's luff has a bit of forward angle in it where the spar meets the luff and stay. Whether internal camber, external half-wishbone, or just hang it all straight sprit and we don't mind no stinking crease on one tack, these versions have the spar run from the clew to the luff and jib stay landing normal to the luff. This unit is self-vanging, so you can sheet from center. Outhaul tension gives wonderful control over the sail's shape. And on a foredeck, it's safer as so much of the spar is well up in the air. The part that can most catch your head, the clew, is actually much tamer than a clew unrestrained by the spar. I've been hit by almost every sort of jib sheet and I'm sure of this one. Much easier to get under than a classic (4) foredeck sweeper.

One last option wonderful for smaller boats. This jib has no stay and the rig is suitable for unstayed masts. The club runs tack to clew and has a pivot attachment to the stem about 1/4 or less back from the tack. Takes a different cut of sail, a little more hollow in the luff and no reverse hollow near the luff's bottom, but once up and halyard and foot tension balanced for the day, it's lovely. It's also really fun to see the tack thrust to weather. I think it was a Gary Hoyt revival. It is seen on some of the smaller Freedoms though it can also be seen on some traditional whaleboats.

I personally do not like the Hoyt innovation that looks like a poorly proportioned anchor davit.

The last option is really best for small boats, like dories and such. The camber spar is far and away best (and costliest) for the larger cruising boat, whether as jib or as forestaysail. The home made half wishbone can be hard to engineer for any but the smallest jib and the straight spar is appealing only to those who like sprits in general.

The classic is always good.

G'luck

[merlinron]

this forum( you guys) is in an out and out, all inclusive human encyclodia of sailing information !!.the descriptions of 5 system and thier following critiques definately assures me of using a self tending jib. my sailing mate is more of an "enjoyer of the ride" than "participator in sail", so i imagine i'll be single handing allot.
i guess i failed to mention that my question was directed towards a working jib. i thought that detail would be understood, not realising you guys don't know how much i might know. ..i know some, probably just enough to get me in trouble

the hoyt system was what i originally envisioned, made of wood, i agree will be a highly stressed operation, doable providing the math is done, but as i think further, as it gets strong enough,probably so bulky, it would look clumsey on a small boat such as mine.

i think the classic(4) is the way i'll go with a slight variation of sheet, more a blend of the two critiques given by Ian M. ....
if i understand his explination correctly, l derive that the "best" method also serves, in effect, as a two part vang of sorts. considering i have two beutiful merriman locking jib tack slides and blocks and 2 bouble blocked boom bails, i have two routes i can take...i think(?)
#1... double(P/S)sheet, dead ended on centerline 1/3 foot lgth. aft of tack, up to blocks directly above on spar aft to blocks at clew, down to blocks on deck near rail, to cockpit....or, #2... reverse route, running both sheets down centerline to cockpit.
the slides on deck will allow correct geometry, and if i am correct in my thinking, playing one sheet against the other, will fine tune the slot.
i would imagine, the reversed route will make getting to the sheets easier when the boat is heeled. does this sound like it will work?.

[Ian McColgin]

If I understand your plan rightly, you don't need to run the sheet forward at all. The bit about the track is not critical as the tracks, I take it, are out by the rail like normal jib tracks. Were you contemplating an athwartships track (or pipe horse) for the sheet, rather like the tracks common for mainsails, it would be a different matter, and you'd need to run the sheet forward.

The double ended approach is nice because it allows for trim from either rail.

Whether you need mechanical advantage is a question.

The simplest system is just a sheet that runs from a convenient cleat on one side through a block on the rail that's about under where the clew crosses the rail (making for no fore or aft pull when close hauled), through a block at the end of the club, down to a block on the other rail and back to a conveniently placed cleat. This already has a nearly 2:1 mechanical advantage with some loss due to the inverted V in the sheet going from rail to club to rail. I find a jib of about 60 square feet easily handled by that in the strong breeze or less (Force 6) that such a boat will sail in comfortably. Unless you have a really big jib, try this first.

If your jib is over 100 square feet you may want more umph in the sheeting. I'd go with double blocks (or two singles in line on that track) on each rail and a triple or three singles on the club under the tack. From cleat - foreward through after or outer block - up through block on club - back down to fore or inner block same rail - up to club - and over and down to fore or inner block on other rail - up to club - down to aft or outer block on rail - and back to cleat.

The lay-out of the blocks at the clew end of the club can be interesting. In general, you're better off here if you do not have swivels on the blocks. If you have a triple, aim the shivs athwartships. If you go with three singles, have two on a strop shivs pointed fore and aft and use them for the bight that goes from the a rail and back to the same rail. The third can be slung shivs athwartships just ahead of those to accommodate the sheet passing from one side to the other.

By the way, remember that the club's pivot is best a bit back from the tack, maybe 1/8 of the foot's length.

Depending on the jib, you may find that the club will clear the stays when set but when lying down on deck with the sail off it overlaps the stays. This can be a convenience. I like to have my jib furled on the club off the center-line, over at the rail and a short pendant and clip sized to the shroud makes a nice landing.

Depending on the geometry, you may find that a jack line through the first four or so jib hanks allows it to settle down more easily.

For any jib over 200 square feet and for many under, I much recommend a downhaul. Nothing more complex that a bit of light dacron line that runs from the hallyard shackle (a permanent installation will keep you from ever losing the hallyard when changing jibs) clip each luff piston shackle over both the stay and the down haul (keeps it from flogging the sail) through a small block at the tack and back to where ever is convenient.

Jibs tend to be self-hoisting in a breeze and there is nothing like being able to get it down and keep it down without hanging about on deck. Besides, when the jib is down, the down-haul can be run in a Sweedish furl (chain knot over the furled sail and club for a fast clean-up and no lost sail stops.

Have fun & G'luck

[merlinron]

i was thinking that the run down the club to center would give a bit of vang to the system, considering your comments, at 100% foretriangle,my jib is only 43ft. the simple routing should be enough. thanks for all the help!

[Ian McColgin]

Good. Usually out over the rail is about the right angle for the jib anyway, so any firm trimming you do will just flatten 'er like a vang.

You want it to lift a bit and belly due to the club pivot being abaft the tack when off the wind anyway.

Have fun.