Please forgive a brat that never outgrew asking “Why.”
Why do we rig our forestay this way. Perhaps so the jib can reach farther forward?
Two basic reasons.
Stand back, look at your rig and follow along. When you tighten the back stay, the top of the mast is pulled aft. This causes more tension to be applied to the forestay. The forestay, then, pulls harder on the fore part of the jib boom and tries to lift it upwards. Because of the fulcrum at the attachment point with the line going to the deck, the aft end of the jib boom is pulled down towards the deck. This is your basic jib leech adjustment. The tighter the backstay, the straighter the leech. This is how the Soling One Meters do it. Other classes allow a jib topping lift to aid in adjusting the jib leech and rig tension.
When running directly downwind, if the sails are on the same side of the boat, most of the jib’s area is in the main’s wind shadow. The little bit that protrudes into clean air is enough for the wind to catch it and flip it to the other side, allowing the sails to go wing-on-wing.
Pro & Con as well -----
Benefit of exisiting jib boom setup is as noted - you can control leech tension and along with clew tension on jib boom, can vary the camber (curvature) in the jib - getting a flat or full blade.
If you run from the forestay it is posssible, but as soon as you sheet out, the clew tension decreases, allowing the jib to instantly get full. Remember that without sheeting to each side of the deck, or use of a traveller, you are controlling the clew end of the sail from the middle of the deck. To get the same benefits of tight leech, you would have to have sheets run to each side of the deck, and probably some jib cars on each side to move forward/aft to vary the pull on the sail by the sheets. Move cars aft, and get a tight foot, but “soft” leech. Move cars forward and you get a tight leech but a “soft” foot. Also need a winch to handle dual side sheeting, which is an extra channel, which is often illegal by class rules as it would require a 3 channel set up.
A negative for the above photo setup is that it moves the forward leading edge of the jib (luff) to windward when sailing upwind. In order to get the proper angle of attack, you would have to foot off slightly to return the leading edge back in line with the wind. Having the jib luff on a normal bigboat forestay would/should allow the boat to point a few degrees higher. I think the photo is what has been found to be the best compromise - maintaining leech control by giving up a couple of degrees of pointing.
A “Hoyt” type boom is a third alternative where the luff is run on a forestay, and the boom comes out of the deck slightly behind the foestay and clew is fastened to it. In this case, the jib boom doesn’t lift up when sheet tension is loosened, so you can still maintain leech control and have the luff on a forestay like a big boat. Doug Lord had discussed this in depth (technically) so if you search “Hoyt Boom” you might find more discussion in archives - if they are still there.
If you go with an overlapping headsail, (Genoa or maybe a 125% jib) then the boom arrangement will not work as it would hit the mast when tacking. The self-tacking boom (like your photo) eliminates a lot of issues that crop up when trying to get your headsail equal to your foretriangle of 100% (more like 90%).
Wanted to go a bit deeper into theory as a self-tending boom and a jib set on a true forestay can work - but you have to give up some adjustments to get the look. Either way, a jib can run downwing wing-and-wing (sails on opposite sides of hull) it’s just easier to do with the setup as in your photo.
EDIT: I knew I had a photo - just couldn’t find it. Here is the “Hoyt Jib Boom”
I wondered if it had to do with the tension on the backstay.
Whenever I’m running downwind, my jib seems to switch from side to side. Perhaps when it does that, I should turn slightly to get the jib to blow to the other side?
I’d ask about how to tell if your backstay should be looser or tighter to adjust your jib leach, except I’m probably too clumbsy a sailor yet to notice the difference:graduate:
My mom wants to sew a set of sails for it next winter.
Wind is swinging back and forth across the stern of the boat, you could get both sails on the same side and “reach” a bit more, rather than dead downwind. If wind is really that bad, it is hard to keep jib on one side and main on the other. A “deep” reach downwind may pay off since you won’t have lost the sail drive from the jib every time it flops over. Just an opinion.
Also, skip the sewing of the sail - use double-sided tape 1/4 inch wide for all your seams, and even for your “luff” hem. Easier to do and won’t “pucker” the cloth if you are using nylon. If using mylar, flower wrapping film, you can’t sew anyway.
I have seen some people putting fishing type weights on the boom, forward of the attachment to the deck. this balances out the weight of the boom and allows the jib to fly to windward
Hmm 1/4 inch double sided tape, skip the sewing. Check.
Where I sail, the wind is terrible. You can change tack every 5 seconds without coming about. You find yourself pointing straight into the wind, turn 90 degrees and find yourself pointing straight into the wind. A bit of a challenge for a landlubber:sly:
Tie a long piece of wool yarn, or a piece of old 1/4 inch wide magnetic recording tape to the trailing end of your mast crane - or attach a vertical wire with same, attached above the mast crane. Keep it long enough to stream, but short enough to keep from tangling on mast, shrouds, back stay or sail. Color yellow, red, orange or bright green, whateve is easy for you to see.
From a distance you will see the general direction of the wind angle compared to your boat heading. Since you aren’t on-board and can’t see any wind shifts until well after they happen, this might help identify them as they are happening. Many opt for a directional arrow on top of mast, which is another option. I’d try the yarn first and if it doesn’t work you calways build/buy a wind direction arrow.
I’ve heard that if you use magnetic audio tape, if you can find an old Willy Nelson, or good “Blue Grass” pickin’ recordings, it will improve the speed of your boat. [wink] 
:lol:
I have a red ribbon at the top of the backstay.
OK -
it won’t change the wind direction for you, but may give you a hint of what the wind is really doing.
If this is your normal/favorite sailing spot, by keeping track of where wind really is when it is coming (supposedly) from a single direction, you will be able to know what to expect. This is why “local knowledge” is so great. If it’s your home pond, you may know from sailing there that when you are on opposite side of pond, just past the big rock on shore, the wind will veer to the left. Then when getting close, you decide whether to tack or stay your course depending on whether you get hit with a header or a lift.
Once decision is made, you can keep heading up until sail stalls or ribbon starts fluttering in a different direction.
As I recall, you sail near large buildings, so there is little chance of having a nice sail. You are trying to learn to sail under the most adverse conditions. I know it’s convenient, but you really ought to try to find an “open” pond with minimal trees or buildings. It can be hard enough to sail in light wind with out all the shifts. Why burden yourself with additional factors. There is always time to learn shifts later. Get to know your boat and hone your handling skills in relatively steady breezes. Then “graduate” and go back to the shifty location. Once you can read sails in steady wind, you may find it is easier to sail in the shifts and holes.
JMHO of course.
hehe Yep, near big buildings, and it’s a bit of a challenge.
I went to the race when the local club was out in the botanic garden, and could almost keep up with their bigger boats. The wind was less unpredictable there. I decided not to join them 'cause they race mainly on Sunday Mornings, and I have other things to do then.
Was sailing Sunday in a pretty strong breeze. Maybe 10Mph. It was coming from the west, so it was pretty steady. Then the little string broke. With the jib flopping the wrong way, it would sometimes go backwards and sometimes nowhere.
It got heading foward pretty well, and I got it almost close enough to reach when it started backing up. Then it sat in the middle of the pond for a while flopping about like an injured bird. Then it backed up toward the shore, but just before I could grab the backstay, it started going forward again.
I finally got the bow stuck between a couple rocks and was able to retrieve the boat. Took longer to get it to shore than it did to replace the broken string.
Maintenance is important:sly: