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  #31  
Old 08-03-2008, 12:17 PM
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alan white alan white is offline
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Originally Posted by Paul Scott View Post
I do recall a jib spar that was two light spars from the clew of the jib to the forestay, but that only takes one load point and turns into two, although I suppose you could cut the jib to that?

Maybe Uffa Fox & L. Francis H. (among others) had the beginning of a solution without going far enough- replace the forestay with a spar, get rid of those pesky swept back spreaders, and running backs? and get a bit more lift off of a properly shaped jib leading edge- perhaps the problem of point loading could be suppressed, as well as headstay sag, mast compression etc.. Might be stuck with a stiff rig, though. I suppose you could have a roller reef inside of the jib spar to reef, and keep flow and shape more controlled. This idea seems to crop up once on a while- I think I saw it in Marchaj somewhere, along with a track on the bow so the jib could move to windward and to lee of the main.
I suppose there are problems with this, has anyone actually tried it? I can see weight (which was L Francis' critique), but with carbon....? Could even incorporate the wishbone into the spar, I suppose. Might make a main wingmast easier? Could think of it as a large jib foil?

Paul
It would be possinle to set up a single curved spar to pivot from a couple/three feet above the tack of the stays'l and single-part vang that to the end of the spar. Let the luff bend there close to the base (even have a thick solid stay (with toggle on top) take over from there down).
While the lower solid stay could be mounted directly to the normal tack hole on the stem head, the sail's own tack could be mounted on a simple pivoting arm that caused the sail tack to move forward when stay-hinging occurred.
Among other advantages, the lower-mounted spar need not ever lower, being at waist level, but instead the sail foot could be undone (e.g. by pelican hook) and it raised to furl with the rest of the sail.
With the spar within reach at all times, I'd feel more secure. The vang could have its own turnbuckle to allow adjustment of the clew height at any time, especially when underway (the vang's position would roughly follow the sail's foot).
I could draw this...

A.
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  #32  
Old 08-06-2008, 05:41 AM
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Originally Posted by Paul Scott View Post
Mr. Watson, nice idea- my brother tried this as a vang for the boom on his OK dinghy. It worked well, but put some stress on the mast, and the boom too, that they hadn't (in all thier hollow glory) been designed for, with predictable results. He anchored the line 1/2 way up the mast.

I like the idea of the spinn. on the 'bowsprit'. Wasn't Jet Services using a relative of this idea? I remember seeing a drawing of an Aerosparish setup with the spinnaker launched and retrieved out of the tube formed by the boom/bowsprit. Or did I draw that? You could do that with your idea too. You might have to make it that big to handle the loads anyway.

The only problem I can see with the idea is the speed that the jibboom would come across the deck during a jibe. Mr. Scott

Yes, I cant claim originality with the 'spin' concept. Harryproa's, model yachts and a lot of other boats have the Baelstrom spar idea working successfully. I dont think it would be much faster across the deck than other alternatives either.

The trick is to be able to use the balancing spar with roller reefing.

The 'unused' extension has a lot of potential for all sorts of strange attachments. The use of the spar as a launch tube might mean an unnatractively thick spar, but it might work.

The problem with using a 'vang' on a more standard jib boom is that you have to have the boom up fairly high to get enough leverage to hold the end of the boom down.
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  #33  
Old 08-06-2008, 06:05 AM
FAST FRED FAST FRED is offline
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Location: Conn in summers , Ortona FL in winter , with big dock & room for O'nite stop .
Having had a boomed jib , my opinion is they SUCK.

The boom will trash about when hoisting or lowering sail and is a sure ankle breaker when working on the foredeck to put on a larger sail.

The boom needs a mounting post back from the forestay , to allow the sail to flatten or get greater draft downwind.

The only solution for lazy folks is to copy the Dutch river work boats.

With a large overlaping jib a heavy eye would be worked into the sail , before the mast.

A line would be rove from side to side through the eye.

On tacking the sail would take care of it self , the luff would start to work as soon as it was full, only for long tacks would the area behind the eyelet need to be sheeted for a bit more area.

FF
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  #34  
Old 08-06-2008, 09:37 AM
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alan white alan white is offline
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"The problem with using a 'vang' on a more standard jib boom is that you have to have the boom up fairly high to get enough leverage to hold the end of the boom down."
True. The solution described puts the boom at maybe waist high above the deck to reduce the distortion of the sail (100 sq ft jib, e.g.). The vang then follows (roughly) the foot of the sail, allowing a reasonable angle.
The whole system of vang and boom would appear to have nothing supporting it (from pushing forward at the forward end of the boom).
Yet as it is pushed forward, the forestay tightens---- only the triangle at the foot of the sail (maybe 10% of the sail) is distorted--- until you see that the sail's tension is on the boom and not the original tack of the sail, which can be moved forward for better sail shape at the bottom.

A.
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  #35  
Old 08-07-2008, 05:11 AM
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Not quite sure what you are meaning there. Unless you get about a 45 degree angle on the vang, the downward pull is largely negated.

If the tack of the jib is 3 inches off the deck, and the vang is three feet long, then the "angle of the vangle" is too obtuse, and has no downward pull.

If you raise the tack off the deck, you lose performance.

And as for thrashing jib booms, that only occurs if you dont have roller reefing.

Thus the reason I was excited about the combination of balanced boom and roller reefing.
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  #36  
Old 02-26-2017, 03:36 AM
revintage revintage is offline
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Even if this is an old thread I couldnīt resist to add a pic of an International Canoe with the same boom concept as rwatson suggested. Note the lifting line acts as a vang.
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Self tacking jib-17316461400_8b8a99511b_k.jpg  
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