Boom and gaff question

[YuriB]

Newbe qurestion . Theoretically, are there any reasons why not to attach boom and gaff (on the gaff type rig) to the mast by parrels, like on the chinese rig?

[Guest20100203]

In Nelson's navy they used jaws on both the boom and gaff. Parrels are only as good as the line that is roved through them. With modern line, this isn't a problem, but this is a relatively new development. Stretch and breaking strength were the reasons you didn't see this approach, but Spectra line can solve all of this issues.

[alan white]

That's the traditional way, with a jaws that is lined with leather and a string of parrels. Mine is that way, using homemade walnut beads. If you need advice on the design considerations, just ask.

[alan white]

Geeesh PAR, what are you doing out of bed?

[YuriB]

I was rather worried about the boom free movement along the parrel lenght. So that it would somehow interfere with tack angle of the sail..

[Guest20100203]

You'd employ a down haul and a keeper (so the boom doesn't drop to the deck when you douse the main). Movement on the boom will be toward the mast, in compression. This keeps the loads off the beads. It would be wise to at least employ a saddle of some sort to keep the boom on the mast. This is why jaws are used. The same is true of the gaff. Much depends on the size of things. On a small craft you can get away with all sorts of simple arrangements, but larger vessels need heftier gear, which normally means metals.

[YuriB]

PAR i wouldn't fully agree with your last statement. To me, simplisity is the way to reliability.
As it was said, with the modern rope materials we can get away from jaws and other heavy things, even for larger crafts.
Yes topenants should be arranged, but they also help to keep reefed sail within.

[alan white]

Yuri, i think you missed the meaning of the comment by PAR.
In any case, besides reducing chafe when the boom or gaff swings, the raising and lowering of the sail is also assisted by parrels. Like little rollers, they prevent the rope from catching on the mast.
I've gone without parrels, and even varnished, the gaff can fetch up sometimes.
It is no great complication to use parrels. in olden times, a ship in the doldrums would sit and slat its sails all day long for weeks sometimes, and serious wear was prevented by such devices as parrels. Nowadays, modern materials still don't completely obviaste the need for things like parrels (though they may be made of nylon, which is no doubt superior to wood for beads). And as said, low-stretch rope with a protective casing is superior to the more traditional rope materials. Most people who build the traditional jaw style booms and gaffs want a traditional look, which is, you must admit, a vert attractive rig.

[Guest20100203]

HDPE make far better beads then wood or nylon.

Restraining a 100 sq. ft. gaff main boom with line and beads is one thing. Doing the same with 400 sq. ft. will require a metal gooseneck.

For example, the 400 sq. ft. mainsail in force 5 winds will exert about 10 horse power on the gooseneck, while the 100 sq. ft. sail will only muster 2.5 HP.

[alan white]

Nevertheless, wood is what I use and it shows no appreciable wear, and I carry 155 sq ft of mains'l.
I believe some large vessels have used parrels and they are simply scaled up.
In fact, there isn't any great tension carried by the parrel line. The jaws are pressed forward either by the throat of the jaws or the cheek, depending on point of sail. Gaffs and some booms have a toggle, a saddle that carries the thrust of the sail opposite the parrels. The parrel line shouldn't be taut anyway, since the jaws are thrust forward under load, and slack is needed for raising the gaff, or if the boom rises, as when gybing. My 155 sq ft sail uses 1/8" line and a few 3/4" wood beads.

[YuriB]

I was just guessing we could use parrel lines for boom and gaff like on the chinese rig.

[YuriB]

I was just guessing we could use parrel lines for boom and gaff like on the chinese rig.http://yuke.users.photofile.ru/photo.../107166484.jpg

[alan white]

On a gaffer? Yes by all means. As has been done for centuries. It is basic and easily shop built rather than using an expensive bronze fitting either on the gaff or the boom. It's easily repaired and if well designed and built, very strong.

[alan white]

http://www.frankhagan.com/weekender/gaffgaff.htm