Small jib for heavy wind?

Shaun , my 100 jib has a really high clew as well. Not sure what to tell you on the main shape. The new main made all the difference, it was hard for me to believe when everyone said a new sail would be like getting a new boat but they were right. Mine however was really blown out so I new there would be some difference, just never imagined how much......

Excellent info

This is a great place to start, folks (having a HS dimension). Let's try this another way, though-so we get something repeatable and applicable to all:

Take the genoa halyard shackle and cleat it off so that the bottom of the shackle is exactly even with the top of the boom track (just extend a line at this elevation to the mast-this is where the top of the "lower band" would be if you had one) when pulled hand tight-this way we have a universal length to a fixed point on the mast. Now swing the halyard shackle out to the forestay (no backstay tension) and mark where the bottom of the shackle touches the forestay when pulled hand tight. Now, using a tape measure, take the distance from this mark on the forestay down to the stem (or center of the stem shackle as Ben did). This of course will not be a full headstay length, but it will be an accurate dimension to use for comparison.

This is how the J 105, B 36.7, etc. do the HS measurement, and is good relative indicator of rake differences..

If we can start collecting this data, we can really develop some meaningful tuning information.

Sail on!

S

Going out tonight, hopefully my rigger is coming again. Will defiantely get this measurement. Also plan on flying my 100% as we took the 145 off to look at the FS swage as we are planning on shortening the FS. Forcast has it blowing 15 tonight so hopefully it holds..Will try and take some pics too of my FS sag and mast bend.

Measured last night pulling the halyard shackle to the tack location of the main. I guess not quite to the top of the boom. I walked it forward to the headstay then measured down to the stem. 86 inches...Guess I should extend the line fwd from the top of the boom and remeasure. No breeze last night so no pics of the 100%. Ended up drifting around till 11pm drinking beer and talking about sailing...

Ok measured again per Seths method. Top of the boom/ forestay pin center= 86". About 1000 lbs on the backstay.

That sounds like what I got. How much bend is in your rig at this setting? I have quite a bit up top and a good deal of BS tension. If I ease it off I get too much sag as my HS is too long right now. I am going to measure using the wing halyard this weekend. Ben do you have any sort of sheave guard up there that the shackle would stop at or is it going right to the sheave? Just waiting on some norseman fittings to shorten the headstay and backstay.

stbdtack said:

Rob thats exactly my sail trim and adjustments when I was checking the helm in 22-24 kts AWS. Flatten it all out, drop the traveler and dump a little mainsheet to depower the head, BTW I was hard on the wind, speed about 6.5kts.

I dont usually reef since another 100 yards and it will blowing 5 kts.

Click to expand...

Of course it is Ben, we're sailing the same boat! Yes, my observations are hard to the wind, speed 6.5-7knots. I don't like to reef either but the Admiral gives me fits about it. RT

My shackle stops at the the face of the mast and sits on the SS guards at each side of the sheave. Its a regular Tylaska shackle and i guess since I hooked the tape on the end I could add another 2 inches from the shackle bail against the mast.

1st pic is backstay slack, 2nd and 3rd is 3000lbs BS tension(about the most i sail with)

Wow thats a lot straighter than my rig... I definately need to get the FS shortened in order to reduce the bend when I add BS tension. I took some pics of my boom last weekend in decent breeze. The bend is a bit scary but I am hoping when I get the vang installed it may get better. Ben are you getting a lot of bend when you are beating in 16kts +?

Not so much

I also thought Ben's bend was not very much-I have seen a lot more on 38's.

This can be due to several things: aft lowers tight and restricting bend to some degree (but this is neither good or bad-just different ways to set things up), set up of mast base and partners, forestay length, etc.

What is important is not how much or how little bend you have-that can vary depending on if the mainsail has a lot of luff curve (depth) and needs the bend to get flat enough-or if your main was failry flat to begin with, you would NOT want to set things up with a lot of bend or you would have the sail boarded out from the backstay before it needed to be.

What matters, whether you are getting 5 or 10 inches of total bend, is does the bend fit the sail, is the rig in control, and is sag being controlled...

They can be different and both correct.

cheers,
S

Seth, can you explain....

kSeth,
By your statement "does the bend fit the sail", I'm assuming you mean that when the mainsail is raised and trimmed, the sail luff follows the contour of the mast bend, without any noticeable uneven pulling/stretching, or extra sail bulging anywhere--is that correct?
Frank.

The bend in my mast is pretty consistent top to bottom. I realized the photo makes it look mostly in the upper portion. Hard to capture in a pic.

My aft lowers are pretty loose and the fwds are pretty snug. Like Seth said, I dont think I need any more bend as the new main goes nice and flat with this amount when i get the backstay on.

I would like to see pics of other 38/35's mast bend.

Ted I didnt get a pic of the boom bend last sail but I'll try to get one next time out. Are you able to sheet in hard by hand with your 7:1 mainsheet? I havent needed the winch so far.

I have needed the winch but I'm a pretty small guy. 7:1 has made all but the last bit in breeze doable without the winch. Really need to get the 6:1 traveler mod going. Here are some shots from sunday. 12-14 TWS. Maybe a gust to 16. Note boom bend and headstay sag. The kite shot is from a week ago light air night and a lot of Mount Gay.Thats also my 100% high clew jib. Will get a mast bend shot soon. Home to complete the rig work this week and get the vang and hyudraulic BS on by the weekend...

NICE shots!!

Ted-The boom looks OK I think-SWEET looking main. Headstay sag seems appropriate-not horrible anyway, considering no BS adjuster yet.

The lead on your kite needs to go WAY back-at least for reaching (might be OK when running). Note the big hook in the leech? That is the lead too far fwd. This has the SLOW effect of closing off the exit of the sail, and also creating a lot of heeling force, which could cause control problems (round ups) when pressed in big breeze-move it aft!!! Open the leech!


FRANK-Good question-I should have explained more. Ben basically beat me to it, but to elaborate: Luff curve in a mainsail is one of the 2 factors that create "depth"(chord depth actually)-and hence power. The other is actual shaping in the seams. Luff curve is material on the luff forward of a straight line from head to tack. When the mast is straight, all of this material is loose and creating/adding depth to the sail. As you bend the mast, this material is taken up, and the depth is eliminated/removed. Typically we design mainsails to have a luff curve of about 80% of available mast bend-meaning that by the time you have bent the mast to 80% of available bend, most (if not all) of the luff curve/shape/draft/power has been taken up or removed. This means you can have a very "powered up" main with the mast straight (as you would want in lighter air), and a very flat main (depowered) in heavy air with the mast bent. The "curve fitting the bend" comment was to ask if the sail could go from full to flat with the available range of adjustment. If you have a mast that can bend 8 inches, but only have 3" of luff curve, the sail will become very flat as soon as you begin to bend the mast-too soon in fact.

Conversely, if you have 10" of luff curve (deep sail), but can only bend the rig 5 " you will never be able to get the sail flat enough. When you have a mast with very little bending ability (like a 35-2), the solution is to put more of the shaping into the seams instead of luff curve. Use maybe 3" of luff curve since there is only about 4" available on this mast, but put more shaping in the seams to get the depth. The seam shaping is affected by outhaul, flattening reef, cunningham, and sheet, and to a small extend, mast bend. Boats with bendy rigs have mainsails built with more luff curve than seam shaping..again, to have the best adjustment range.

I hope that helps make this a bit more clear-great questions!!!

Cheers,
S

Thanks Seth. The boom flex has had me a bit concerned, but I guess it is not so bad. Will be back withmoer shots once we finish the vang and bs adjuster mods.